Plenary

SC20-00200

Abstract Type :

Plenary session

Abstract Title :

Antibody responses to SARS-CoV-2 infection and vaccination

Abstract :

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in 2019 and has since then caused the coronavirus 2019 (COVID-19) pandemic. We have characterized the magnitude, functionality, breadth and longevity of the antibody response to the SARS-CoV-2 spike protein after infection and vaccination with different COVID-19 vaccines. This includes analysis of the mucosal immune response in the upper respiratory tract which is thought to be important for blocking infection and transmission. Our work also includes analysis of the immune response to the NDV-HXP-S vaccine, which can be manufactured using traditional facilities that produced influenza virus vaccines in eggs. We find that there are differences between infection and vaccination and also between different vaccines that may impact on protection from (re-)infection.

SC20-00048

Abstract Type :

Plenary session

Abstract Title :

Confronting the Steep Challenges in Diagnosis and Treatment of Pernicious Plasmodium vivax Malaria

Abstract :

We have considered the malaria caused by Plasmodium vivax to be a benign infection of the bloodstream affecting just a few million people per year scattered among low-endemic areas in Asia and the Americas. But it seems that none of this is true. Vivax malaria is a perniciously dangerous infection of the deep organs occurring across the tropical latitudes, including Duffy-negative Africa, in currently unknown numbers of people. We may have greatly underestimated this problem – it is more invasive, harmful, prevalent, and transmissible than we have firmly believed it to be.Acknowledging that character of vivax malaria is the first step in confronting the steep challenges thus imposed on its technical solution by diagnosis and treatment. This lecture aims to encourage that acknowledgement by highlighting the evidence of its veracity, and then to review those challenges to spur more appropriate research that serves to mitigate the substantial harm being done.

Topic Keynote

Abstract Type :

Topic Keynote

Abstract Title :

Harnessing genomics for malaria eradication

Abstract :

Over the past three decades genomics and genetics have transformed our understanding of malaria parasite biology. The publication of the first complete genome of Plasmodium falciparum was a milestone. The dawn of molecular genetics and genetic engineering enabled interrogation and functional validation and of genetic features. Many fundamental insights have since been elucidated including the identification of all essential genes. In addition, drug targets and drug resistance markers have been identified. The observed significant genetic diversity in natural populations has important implications for potential vaccine candidates and antigen based diagnostic tools, including hrp2/3 deletions which compromise RDTs (Rapid Diagnostic Tests). Adaptation of CRISPR/Cas9 technology now enables functional interrogation of any gene in the genome and allow researchers to interrogate unique aspects of parasite biology generating new insights for drug or vaccine development. In vivo evolution of resistance approaches pioneered by the Malaria Drug Accelerator have identified new targets and pathways for future drug development.
Fueled by the advancing technology, genotyping and whole genome sequencing is now routine in many endemic countries. This will enable endemic countries to implement molecular surveillance systems to detect potential emergence of drug resistance or the compromise of important diagnostic techniques. Importantly, the availability of whole genome sequences from diverse natural settings will allow identification of key targets of the human immune system or genes relevant to host- or vector- pathogen interactions. A greater understanding of the biology of the parasite can lead to novel approaches to control and eventually eradicate the disease.

SC20-00075

Abstract Type :

Topic Keynote

Abstract Title :

Alternative strategies for the elimination of lymphatic filariasis and onchocerciasis

Abstract :

Two neglected tropical diseases, lymphatic filariasis (LF, affecting 65 million people) and onchocerciasis (river blindness, affecting 21 million people) are leading causes of global morbidity. Current control efforts are hindered by the lack of a safe macrofilaricidal drug. A clinically validated approach for delivering macrofilaricidal activity is to target the Wolbachia bacterial endosymbiont of the causative nematodes. The A-WOL consortium identified two candidate molecules, which met the target product profile criteria of killing adult worms with a regimen of 7 days or less. TylAMac (flubentylosin), a novel macrolide based on the veterinary antibiotic tylosin, was the first next generation anti-Wolbachia drug to be designed specifically as a macrofilaricidal agent. The lead molecule has completed formal preclinical evaluation in partnership with AbbVie, which after successful Phase I trials, has entered Phase II trials in partnership with DNDi. Secondly, through guided medicinal chemistry from a screening hit we have delivered a preclinical candidate specifically targeting Wolbachia and showing a more rapid kill rate compared with all other anti-wolbachial drugs. The candidate drug, AWZ1066S, has completed its CMC development, formal pre-clinical development and is currently in Phase I trials. A-WOL has screened the human pharmacopeia, focused anti-infective and large diversity libraries to identify 6 novel anti-Wolbachia chemotypes with suitable drug-like qualities. The first industrial scale screening of 1.3 million compounds in partnership with AstraZeneca delivered 20,000 hits and a further 10 novel chemotypes as promising new leads. A radical improvement to targeting Wolbachia occurs via a drug synergy between a common anthelmintic drug (albendazole) and all different classes of antibiotics in the A-WOL portfolio. Using the drugs in combination reduced the length of treatment required opening up the opportunity to scale-up this approach at the community level.

SC20-00161

Abstract Type :

Plenary session

Abstract Title :

Eliminating viral hepatitis in Thailand by the year 2030

Abstract :

Viral hepatitis is a worldwide public health problem. The World Health Organization (WHO) aims to eliminate hepatitis B and C by 2030. In Thailand, the hepatitis B (HB) vaccine has been used for vaccination in all newborns for the prevention of hepatitis B virus (HBV) infection for more than three decades. The protective efficacy is very high. The long-term immunogenicity and impact of universal hepatitis B vaccination on newborns as part of the EPI program for more than 20 years were evaluated. There was a significant reduction in the number children and young adults born after universal HB vaccination who are HBV carriers. HBV infection by means of detectable antiHBc also declined in the younger population. Moreover, stringent screening of blood donations and decreasing the use of illicit injecting drugs further reduced new HB infections. It is believed that the implementation of universal vaccination to prevent new infections will lead to the eventual eradication of this disease. A national survey on hepatitis C virus (HCV) infection in Thailand through sampling from different geographical regions confirmed the declining prevalence of HCV. The reduction in HCV infection may be associated with several factors, including changes in intravenous-to-oral illicit methamphetamine use, increase awareness of HIV prevention, significant improvement in the health care and clinical practices, and precautionary measures against blood-borne pathogens. In Phetchabun province where HCV “test-to-treat” pilot program is underway, we undertook an HCV epidemiological study to assess the disease burden by screening target population and establish a diagnostic strategy. We found that higher HCV seroprevalence was significantly associated with intravenous drug use and tattoo. The birth-cohort analysis demonstrated that people who were born in or before 1982 (therefore ages 35 years or older) had disproportionately high HCV seroprevalence. It would, therefore, be ideal to include this age group in the initial phase of HCV mass screening. As such, HCV screening is recommended at least once for adults. The treatment strategy should be implemented by using the currently available highly safe and efficacious direct antiviral agents with a high cure rate, which is expected to contribute to the reduction in hepatitis C transmission and mortality. We anticipate that Phetchabun model will ensure the successful planning of hepatitis elimination in Thailand as it serves as regional pilot trial prior to national implementation.

SC20-00091

Abstract Type :

Topic Keynote

Abstract Title :

New innovations and focus in antimalarial drug discovery

Abstract :

Falciparum malaria, a devastating parasitic disease affecting an estimated 241 million people each year, is treated using fixed dose combination treatments, the Artemisinin Combination Therapies (ACTs) over 3 days of dosing. The constant threat of resistance and the need to deliver alternative options to treat patients in the event of all ACTs failing, as well as the need for improved drugs against other human-infecting Plasmodium parasites, has led to Medicines for Malaria Venture (MMV) and its partners, in collaboration, to build up a portfolio of projects and compounds focused on the treatment and prevention of malaria. MMV’s mission is to reduce the burden of malaria in disease-endemic countries by discovering, developing, and facilitating delivery of new, effective and affordable antimalarial drugs in collaboration with international partners. The portfolio has been strengthened in recent years by the delivery of twelve new products, most recently tafenoquine an 8-aminoquinoline giving a single dose radical cure of vivax malaria, in combination with chloroquine. Progress has also been made in identifying the next generation of antimalarials through defining the first wave of potential new non-artemisinin combinations – though these require further clinical testing before ultimately being available to patients. Additionally, there has been success in delivering candidate drugs into preclinical development, to a high-quality standard and fueling the Discovery pipeline, with the help of the Malaria Drug Accelerator. This talk will cover the strategy underpinning antimalarial drug discovery, the status of the current portfolio (including the attrition and delivery) alongside a summary of new innovations to accelerate antimalarial drug discovery.

IC20-TK8R4

Abstract Type :

Plenary session

Abstract Title :

Human Rabies: Prospects for Elimination in Limited-Resource Countries

Abstract :

Inappropriate dog control and vaccination programs, limited access to post-exposure prophylaxis (PEP), and shortage in supply of cell-culture rabies vaccine and immunoglobulin (RIG) remain problems of human rabies prevention for population in canine rabies endemic area. The keys to the success of elimination of human rabies has been because of control of stray dogs and mass dog vaccination, increasing accessibility to PEP using economic and efficacy intradermal (ID) regimen improved rabies vaccination, intensified follow-up of patients exposed to rabies and public education. Attempts to reduce costs of PEP by reducing the dosage of vaccine and number of visits have produced on several variations such as one-week intradermal regimen (IPC ID regimens; two-site 0.1 mL ID injection at deltoid area on days 0,3 and 7) and one 4-site ID booster vaccination for PEP as recently recommended by WHO. Local wound infiltration only of RIG is affordable and has highlighted the importance of less volume of RIG without compromising patient survival in rabies endemic countries. Each country in rabies endemic areas should encourage carefully designed studies on the feasibility and impact of incorporating pre-exposure prophylaxis (PrEP) in programs of immunization for risk groups including children because PrEP simplifies PEP by reducing the number of vaccinations required and avoiding the need for RIG. The shorten two-dose PrEP schedule completed in one week (2-site ID or 1-site intramuscular on days 0 and 7) that are recently recommended by WHO could provide an opportunity to vaccinate more people with less cost and reduced visit.

SC20-00103

Abstract Type :

Topic Keynote

Abstract Title :

Impact of insecticide resistance on disease control

Abstract :

Pyrethroids are the major insecticides used over the last decade for control of insect borne disease. In many insect vectors pyrethroid resistance is rising causing issues with effectiveness of control. The problem is particularly acute in mosquitoes that transmit malaria. Here I describe mapping and modelling efforts to track the spread and intensity of resistance in major malaria vectors and large-scale randomised control trials in Uganda and DRC demonstrating the impact that resistance has on the effectiveness of pyrethroid impregnated bednets.

SC20-00165

Abstract Type : Topic Keynote Abstract Title : Advances in molecular diagnosis of tuberculosis and mycobacterial infection Abstract : Drug-resistant tuberculosis (DR-TB) is a very serious health problem globally. The resistance level, mortality, and treatment cost of TB diseases ranged from multidrug-resistant tuberculosis (MDR-TB), pre-extensively drug-resistant tuberculosis (pre-XDR-TB) to extensively drug-resistant tuberculosis (XDR-TB). Elimination of TB on a global agenda is impossible without novel effective tools and strategies to battle against both latent TB and active TB. Also, non-tuberculous mycobacterium (NTM) infection increased its importance by causing more prevalence and anticipation of drug resistance. The increasing population at risk for NTM infection, especially the elderly, increases the concern for an effective control strategy. In this presentation, the series of TB and mycobacterial research that was recently conducted related to active tuberculosis (ATB), latent tuberculosis infection (LTBI), and NTM infection will be presented. The classical molecular diagnosis and next generation of advanced diagnosis for ATB and LTBI will be updated. The advanced molecular diagnosis for NTM will be also presented. The example of our research applying advanced technology such as high throughput sequencing analysis and proteomic analysis for TB and NTM will be presented and discussed. These studies were examples of our current efforts against TB and NTM infection control.

SC20-00175

Abstract Type :

Topic Keynote

Abstract Title :

Enteric vaccines from discovery to access

Abstract :

Vaccines against rotavirus were approved in the USA in 2006, and soon 70% of US children were vaccinated. 16 years later, in 2022, globally 60% of children have not received rotavirus vaccine. There are WHO prequalified vaccines against the enteric pathogens rotavirus, cholera, and typhoid, but as we think about the pathway for development of future enteric vaccines – shigella, non-typhoidal salmonella, paratyphoid, enterotoxigenic E. coli – we will face challenges more similar to those faced by cholera and typhoid than by rotavirus. Importantly, vaccine development for global health encompasses innovation that moves from demonstrated need to demonstrated impact. Often the burden of disease, in this case of enteric disease, is not well defined in most countries of high burden. Developing country vaccine manufacturers do not have the R&D funding or cost-structure to do engage in necessary early stage research. Funding is often provided by an outside funder (for instance, the Gates Foundation). Work with WHO, SAGE, and GAVI — and with NITAGs are critical if delay is to be avoided. It is possible to develop data around cost of illness, and cost-effectiveness analysis during late stage testing, but often this is delayed until licensure is achieved. These data are important for countries considering incorporation of the vaccine in the national immunization plan. The measurement of real-world evidence of effectiveness will be important if the impact of vaccination on the target disease is the “end-in-mind”.

SC20-00013

Abstract Type :

2. Topic Keynote

Abstract Title :

Epedemiology of submicroscopic malaria and molecular survelliance of drug resistance

Abstract :

Malaria still poses a major global threat, with a death toll of over 627,000 per year. WHO plans to eliminate malaria in the Greater Mekong subregion (GMS) by 2030. To reach this goal, we must know who are infected, which areas are at risk, and how the infections spread. Thus, detecting infection and its spread will lead to the Ministry of Public Health/WHO mandate. We developed a high-volume qPCR to identify people with asymptomatic malaria. The high-volume qPCR identified infections with as few as 20 parasites/mL, which is 2000 times lower than the microscopic method and 500 times lower than the conventional PCR technology. This involved examining 61,544 blood samples from 274 villages. In Thailand, Myanmar, Cambodia, Laos, and Vietnam, the approach has resulted to a 20 % infection rate (78% in some villages) and increased detection of the infected among the asymptomatic population. The infections found in these areas were further determined to be Plasmodium falciparum infections (5%) and Plasmodium vivax (13%). This groundbreaking information has already eliminated the traditional belief that there are few asymptomatic malaria patients in this region. Furthermore, the GMS is a source of drug resistance in P. falciparum. From 2007 to 2018, P. falciparum isolates from Myanmar, Thailand, Laos, and Cambodia (n = 10,632) were genotyped for antimalarial drug resistance markers in order to describe resistance in this region (pfkelch, pfcrt, pfplasmepsin2, and pfmdr1). To determine genetic relatedness, target gene flanking sequences were microsatellite and SNP typed. A single long pfkelch Cys580Tyr haplotype (from -50 kb to +31·5 kb) conferring artemisinin resistance (PfPailin) now dominates across the eastern GMS. Piperaquine resistance associated with pfplasmepsin2 gene amplification and mutations in pfcrt downstream of the Lys76Thr chloroquine resistance locus has also developed. On the Thailand-Myanmar border a different pfkelch Cys580Tyr lineage rose to high frequencies before it was eliminated. Elsewhere in Myanmar the Cys580Tyr allele remains widespread at low allele frequencies. Meanwhile a single artemisinin-resistant pfkelch Phe446Ile haplotype has spread across Myanmar. Despite intense use of dihydroartemisinin-piperaquine in Kayin state, eastern Myanmar, both in treatment and mass drug administrations, no selection of piperaquine resistance markers was observed. Pfmdr1 amplification, a marker of resistance to mefloquine, remains at low prevalence across the entire region. Artemisinin resistance in P. falciparum is now prevalent across the GMS. In the eastern GMS a multidrug resistant P. falciparum lineage (PfPailin) dominates. In Myanmar a long pfkelch Phe446Ile haplotype has spread widely but, by contrast with the eastern Greater Mekong subregion, there is no indication of artemisinin combination therapy (ACT) partner drug resistance from genotyping known markers, and no evidence of spread of ACT resistant P. falciparum from the east to the west. There is still a window of opportunity to prevent global spread of ACT resistance.

SC20-00174

Abstract Type : Topic Keynote Abstract Title : Target-based screening versus phenotypic screening for antiparasitic drug discovery: contrasting two strategies. Abstract : The antiparasitic drug research group at the University of Washington has been pursuing drug discovery for trypanosomatid infections following two strategies: target-based vs. non-target based. In the former, we are targeting the methionyl-tRNA synthetase of pathogenic protozoa. The target has been genetically and chemically validated, and a crystal structure is used to guide small molecule drug design. The knowledge of the target is helping to understand and avoid potential off-target effects. On the down-side, solving pharmacological problems has been challenging and working on a single-enzyme target creates the risk for mutations that could lead to drug resistance. The non-target based project began with a phenotypic screen to identify inhibitors of Trypanosoma brucei growth. Several distinct scaffolds were identified and selected for further optimization based on favorable physicochemical and pharmacological properties. Through traditional med-chem methods, multiple scaffolds were explored leading to one scaffold that is now in late-preclinical studies for Chagas disease. The lead compounds have excellent pharmacological properties and cure mice with chronic Trypanosoma cruzi infection. On the down-side, without knowing the target it is more difficult to anticipate potential side effects in the host. Further comparisons of the two drug-discovery strategies will be discussed.

SC20-00164

Abstract Type :

Topic Keynote

Abstract Title :

Molecular Evolution of SARS-CoV-2: Past, Present and Future

Abstract :

Introduction: After 2.5 years of COVID-19 pandemic, over 11 million complete genome sequences of SARS-CoV-2 have been deposited in public repositories. The epidemic spread and genetic changes of the new virus have been followed with unprecedented detail. I will highlight and analyze the main phases of the molecular epidemiology and evolution of the virus. Methods: Phylogenetic, phylodynamic, and molecular epidemiological analyses of complete genome sequences have been used to track mutations and variants, analyze sources of outbreaks, routes of transmission, and changes in the epidemiological features of the virus. Results: I differentiate four phases with different characteristics and relevant questions. Phase 0 corresponds to the origin and early spread of the virus from the Hubei region in China. Phase 1 was characterized by the appearance of a few mutations, some of which spread to fixation, in a completely naïve host population. In phase 2, a few variants, markedly different from those circulating at that time, arose in populations that were gaining immunity through vaccination and previous infections. Variants of concern (VOCs) and of interest (VOIs) such as alpha, beta, or delta, reached fixation very rapidly. The final phase is characterized by the emergence and spread of a new constellation of subvariants of the omicron VOC. With a yet undetermined origin, omicron has shown that it can spread very rapidly even in populations with high levels of immunity. Conclusion: SARS-CoV-2 has surprised experts and may continue doing so. New variants will arise and we need a continuous monitoring of their genetic features.

IC20-TK16R4

Abstract Type :

Topic Keynote

Abstract Title :

Thailand Antimicrobial Resistance (AMR) Program in Response to Global Action Plan on AMR

Abstract :

The Thailand Antimicrobial Resistance (AMR) Containment and Prevention Program, utilizing a One Health approach, has been implementing the following operational actions in accordance with the World Health Organization (WHO) global action plan on AMR since 2013. They are: 1) estimate the national AMR burden in Thailand; 2) determine the AMR prevalence and AMR chain on emergence and spread of AMR in Thailand; 3) develop laboratory and information technology systems for surveillance of AMR; 4) regulate the use and distribution of antibiotics in humans and food animals; 5) generate local evidence to promote responsible antibiotic use and infection prevention and control (IPC); 6) develop and implement the AMR campaign packages based on relevant local evidence in selected communities; and 7) conduct research and development of integrated surveillance of AMR, antibiotic consumption (AMC), antibiotic use (AMU), hospital-acquired infections (HAI) and AMR burden; rapid diagnostics, and therapy and prevention of AMR infections. The major outputs, outcomes and impacts of the Thailand AMR program are: 1) the magnitude of AMR burden in Thailand is established; 2) prevalence of important AMR bacteria and AMR chain on emergence and spread of AMR in Thailand are available; 3) AMR campaign packages for health professionals and laypeople were developed according to the established AMR chain on emergence and spread of AMR and AMR prevalence in Thailand; 4) locally-generated evidence on the responsible use of antibiotics and IPC are available; 5) implementation of AMR campaign packages in pilot communities revealed their effectiveness in terms of improved awareness, understanding and behavior change of antibiotic use and AMR, responsible use of antibiotics; and compliance with IPC practices; 6) many AMR containment and prevention measures developed by the Thailand AMR program have been adopted as national policy and implemented nationally including responsible use of antibiotic project in public healthcare facilities; 7) Faculty of Medicine Siriraj Hospital has been designated by WHO for being WHO Collaborating Centre for AMR Prevention and Containment since 2016; Faculty of Medicine Siriraj Hospital has been appointed by the Fleming Fund for being Host Institution for international fellowship training on AMR since 2018; and a large repository of more than 20,000 isolates of many kinds of important AMR bacteria collected from healthy, patient, food animal, pet, food and environment.

SC20-00205

Abstract Type : Plenary session Abstract Title : The future of Snakebite Care; how can we do better? Abstract : Snake bite remains a major global issue causing a significant burden of death and morbidity. Despite recently being designated a neglected tropical disease, there are still considerable challenges in managing the patient with snake bite. The true burden of snake bite globally and nationally is still not known accurately and estimation of the disability caused by snakebite is challenging. Antivenom quality, availability and affordability varies considerably across the world and management of local envenoming and its consequences is rarely evidence driven. The establishment of the WHO Snakebite Road map in 2019 and investment by organisations such as Wellcome has started to change the environment for snake bite research and policy, but there is still a great deal to be done. The talk will highlight areas in which we still need to understand aspects of epidemiology, pathophysiology and optimal clinical management and will explore pathways improving outcomes following snake bite

SC20-00223

Abstract Type :

Topic Keynote

Abstract Title :

Roles of an antiviral Nirmatrelvir/ritonavir during COVID-19 pandemic and beyond

Abstract :

COVID-19 pandemic continues to be a global impact. By October 2022, there’re more than 615 million confirmed COVID-19 cases and 6.5 million deaths globally. BA.5 Omicron variant continue to be dominant in most part of the world, responsible for >90% of all cases. The characteristics of Omicron BA.5 which increased infectivity and ability to evade immunity might play a key role on its dominance though the severity is not increased compared to the previous Omicron subvariant such as BA.1 and BA.2. Mutation of SARS-CoV-2 causes some of the treatment options to become ineffective. A study shows Omicron variants may be less susceptible to monoclonal antibodies, including Sotrovimab and Casirivimab/imdevimab. On the other hand, three small-molecule antiviral drugs remdesivir, nirmatrelvir and molnupiravir still maintain therapeutic effect against Omicron variants. The result is confirmed by various real-world evidence of nirmatrelvir globally including the US, Hong Kong, Israel, Italy, and China, that shows nirmatrelvir is effective on prevention of progression of COVID-19, hospitalization, and death during Omicron wave. These real-world data are in alignment with result from pivotal trial, the EPIC-HR study of nirmatrelvir which shows 89% efficacy against COVID-19 hospitalization and death if starting treatment within 5 days of symptom onset. The importance of effective antiviral treatment for high-risk patients who have underlying medical conditions is emphasized in various clinical practice guidelines including National Institute of Health COVID-19 treatment guidelines in the US and WHO’s Therapeutics and COVID-19: Living Guideline, all with nirmatrelvir/ritonavir as a first-line drug for non-hospitalized mild to moderate COVID-19 patients who are at risk of disease progression such as medical conditions including diabetes, hypertension, immunocompromised conditions, elderly etc. Nirmatrelvir/ritonavir is an anti-SARS-CoV-2 drug which mechanism of action is to inhibit protease enzyme, Mpro or Main protease, and prevent the replication of the virus. With Main protease is preserved across SARS-CoV-2 variants with minimal to no mutation, this might be an advantage of nirmatrelvir to be effective against future SARS-CoV-2 variants.

SC20-00222

Abstract Type :

Topic Keynote

Abstract Title :

A NEW ERA IN DENGUE VACCINATION

Abstract :

Dengue is a significant public health problem in tropical countries with a dire need for effective preventive measures. As dengue is a disease caused by four distinct serotypes (DENV-1, DENV-2, DENV-3, and DENV-4), the development of an effective dengue vaccine with all strain coverage becomes very challenging. Furthermore, there remains an unmet need for a dengue vaccine regardless of dengue serostatus at baseline. This lunch symposium, “A New Era in Dengue Vaccination”, has brought together an illustrious group of speakers to present and discuss the challenges mentioned above as well as exploring the new tetravalent dengue vaccine candidate including the historical development in Mahidol University, Thailand, its mechanism of action involving cell-mediated and humoral immune responses, its latest clinical trial results, and its potential to reduce dengue’s public health burden in Thailand, Asia, and beyond.

Luncheon Symposium
Sutee Yoksan
Mayuri Sharma
Gonzalo Pere
Sasisopin Kiertiburanakul

[SC20-00222]

Abstract Type :

3. Symposium

Abstract Title :

A NEW ERA IN DENGUE VACCINATION

Abstract :

Dengue is a significant public health problem in tropical countries with a dire need for effective preventive measures. As dengue is a disease caused by four distinct serotypes (DENV-1, DENV-2, DENV-3, and DENV-4), the development of an effective dengue vaccine with all strain coverage becomes very challenging. Furthermore, there remains an unmet need for a dengue vaccine regardless of dengue serostatus at baseline. This lunch symposium, “A New Era in Dengue Vaccination”, has brought together an illustrious group of speakers to present and discuss the challenges mentioned above as well as exploring the new tetravalent dengue vaccine candidate including the historical development in Mahidol University, Thailand, its mechanism of action involving cell-mediated and humoral immune responses, its latest clinical trial results, and its potential to reduce dengue’s public health burden in Thailand, Asia, and beyond.

Symposium Day 2 25 October 2022
S1_R1: Pathophysiology and treatment of severe malaria Chairperson: Katherine Plewes Co-Chairperson: Arjen Dondorp

SC20-00114

Abstract Type :

Symposium

Abstract Title :

The macro and microcirculation in severe falciparum malaria

Abstract :

Severe falciparum malaria is a disease of microcirculation. The main pathophysiology is multiple organ dysfunction caused by parasitized erythrocyte sequestration in microvasculature. Plasma lactate concentration, proxy measure of tissue perfusion, is correlated with indices of microvascular obstruction; blocked capillaries by direct in vivo observation, red cell deformability, and parasite biomass estimated by plasma PfHRP2. However, macrovascular factors of oxygen delivery and fluid status do not show a significant correlation with plasma lactate. Fluid resuscitation in severe malaria does not improve tissue perfusion in adults and even increases the mortality in children with impaired perfusion, while restrictive fluid management does not worsen tissue perfusion in adults with severe malaria. Considering the low incidence of hemodynamic shock in severe malaria, restrictive fluid management is a recommended treatment strategy in patients with severe malaria.

[SC20-00012]

Abstract Type :

Symposium

Abstract Title :

Cell free hemoglobin mediated oxidative stress and paracetamol in severe malaria

Abstract :

Background. The pathogenic role of cell-free hemoglobin-mediated oxidative stress in acute kidney injury (AKI) and whether paracetamol’s capacity to inhibit plasma hemoglobin-mediated oxidation is renoprotective in severe malaria was investigated. Methods. Among Bangladeshi patients with severe malaria, the relationships between plasma cell-free hemoglobin (CFH), lipid peroxidation markers (F2 -isoprostanes (F2 -IsoPs) and isofurans (IsoFs)) and kidney function were examined in a prospective observational study. Subsequently, a phase 2, open-label, randomized controlled trial assessed effects of paracetamol on renal function. Results. Severe malaria patients with AKI (62/107) had significantly higher plasma CFH, F2-IsoP and IsoF concentrations on enrolment compared to those without AKI (p = 0.018, p < 0.001, p < 0.001). Mixed effects modeling showed that F2 -IsoPs, IsoFs, and CFH were independently associated with increasing creatinine over 72 h. Among 62 patients randomly assigned to receive paracetamol (n = 31) or no paracetamol (n = 31), the median (interquartile range) reduction in creatinine after 72 hours was 23% (37% to 18%) in patients assigned to paracetamol, versus 14% (29% to 0%) in patients assigned to no paracetamol (p = 0.043). This difference in reduction was 37% (48% to 22%) versus 14% (30% to −71%) in patients with hemoglobin ≥45 000 ng/mL (P = .010). The proportion with progressing kidney injury was higher among controls (p = 0.034). Conclusions. Cell-free hemoglobin and lipid peroxidation are associated with AKI, and paracetamol is renoprotective, particularly in those with prominent intravascular hemolysis, without evidence of safety concerns in patients with severe falciparum malaria.

[SC20-00151]

Abstract Type :

Symposium

Abstract Title :

The gut microbiota in severe falciparum malaria

Abstract :

Introduction: Hallmark of the pathophysiology of severe falciparum malaria is sequestration of mature parasite infected red blood cell compromising the microcirculation. There is an increased interest in the role of the gut microbiota in the pathophysiology of the disease. Methods: We review the evidence on changes in microbiota composition, their potential translocation through the gut barrier, release of microbiota products, and microbiotic effects on gut immunity. Potential interventions targeting the gut microbiota including probiotics and other interventions are also presented. Results: Patients with severe malaria had reduced gut integrity and increased plasma levels of potentially gut-derived D-lactate. Plasma L-citrulline was significantly decreased in patients with malaria indicating that enterocyte integrity might be compromised during malaria infection. The gut microbiota of patients with severe malaria was significantly enriched with potentially pathogenic Enteroccocus , Escherichia coli and Shigella species. Conclusions: Current research suggests that the gut microbiota could play an important role in the pathophysiology of severe falciparum malaria. Better understanding of the interplay between gut microbiota and the host response could guide novel treatment options.

[SC20-00151]

Abstract Type :

Symposium

Abstract Title :

The gut microbiota in severe falciparum malaria

Abstract :

Introduction: Hallmark of the pathophysiology of severe falciparum malaria is sequestration of mature parasite infected red blood cell compromising the microcirculation. There is an increased interest in the role of the gut microbiota in the pathophysiology of the disease. Methods: We review the evidence on changes in microbiota composition, their potential translocation through the gut barrier, release of microbiota products, and microbiotic effects on gut immunity. Potential interventions targeting the gut microbiota including probiotics and other interventions are also presented. Results: Patients with severe malaria had reduced gut integrity and increased plasma levels of potentially gut-derived D-lactate. Plasma L-citrulline was significantly decreased in patients with malaria indicating that enterocyte integrity might be compromised during malaria infection. The gut microbiota of patients with severe malaria was significantly enriched with potentially pathogenic Enteroccocus , Escherichia coli and Shigella species. Conclusions: Current research suggests that the gut microbiota could play an important role in the pathophysiology of severe falciparum malaria. Better understanding of the interplay between gut microbiota and the host response could guide novel treatment options.

S2_R2: Antimalarial drug resistance
Chairperson: Mallika Imwong
Co-Chairperson: Olivo Miotto

[SC20-00081]

Abstract Type :

Symposium

Abstract Title :

Targeting proteostasis to overcome artemisinin resistance

Abstract :

Dihydroartemisinin (DHA) kills P. falciparum via a two-pronged mechanism, causing protein unfolding and functionally damaging the parasite proteasome. The consequent accumulation of proteasome substrates, i.e., unfolded and polyubiquitinated proteins, activates the Unfolded Protein Response and underpins DHA-mediated killing. In an effort to overcome the increasing levels of resistance to artemisinins and partner drugs, we screened a series of nucleoside sulfamates from the Takeda Pharmaceuticals library and identified compounds that exhibit high potency against P. falciparum blood stage cultures, high selectivity against mammalian cell lines and long half-lives in blood. An exemplar compound demonstrates multi-stage activity and single dose efficacy in the P. falciparum SCID mouse model. Using in vitro evolution of resistance, we have identified the target as P. falciparum tyrosyl-tRNA synthetase (PfTyr-RS). PfTyr-RS catalyses the formation of a highly stable inhibitory sulfamate conjugate, via a mechanism we call reaction-hijacking. Enzyme kinetics and X-ray crystallographic studies of plasmodium and human Tyr-RS reveal that differential flexibility of a loop over the catalytic site determines differential susceptibility to inhibition by nucleoside sulfamates. The work points to the potential for the design of bespoke nucleoside sulfamates, with tuneable specificity for applications in a broad range of infectious diseases.

[IC20-S2R2]


Abstract Type :

Symposium

Abstract Title :
Multiallelic polymorphisms of short tandem repeats (STR) drive transcriptional variations of Plasmodium falciparum associated with artemisinin resistance.

Abstract :

It is becoming clear that artemisinin resistance of Plasmodium falciparum is a complex genetic trait underlying a multifaceted molecular mechanism. Transcription-phenotype association studies (TPAS) carried by our group over last decade identified a broad spectrum of genes can be linked with artemisinin resistance by their differential transcriptional levels. Here we investigated the intergenic/noncoding regions the P. falciparum genome to identifying sequence polymorphism that potentially drive these transcriptional variations. Indeed, we identified a broad spectrum of multiallelic sequence polymorphisms in whole genome sequences of P. falciparum field isolates collected during several large-scale epidemiological surveys through the Greater Mekong Subregion between 2011 to 2019. The vast majority of these polymorphism involve microsatellite-like sequence length variations at the short tandem repeats (STR) of the AT right low complexity sequences that are known to account for ~10% of the P. falciparum genome. Using expression quantitative trait loci, we identified a subset of polymorphic STRs in the putative promoter regions that associate with transcriptional levels of their target genes (eSTR). From the ~500 eSTRs identified in the promoter regions, more than 25% (~100) can be also associated with the parasite clearance half-life, the clinical manifestation of artemisinin resistance. These results suggest that the highly dynamic, multiallelic SRT polymorphisms at the promoter regions of P. falciparum genes contribute to the currently ongoing evolution of artemisinin resistance; by modulating transcriptional activities. It is feasible to speculate that these eSTRs function either in the context of PfK13-SNP (as “a genetic background”) but can also function independently, giving rise to alternative artemisinin resistance phenotypes. Biological relevance and functional implications of the identified eSRTs on P. falciparum pathophysiology will be discussed.

[IC20-S2R2-2]


Abstract Type :

Symposium

Abstract Title :
Genetic surveillance of drug-resistant malaria

Abstract :

As the Greater Mekong Subregion (GMS) gradually approaches elimination of malaria, selective pressures on the Plasmodium falciparum parasite populations increase, often leading to rapid epidemiological changes such as the emergence and spread of drug resistance over large parts of the region. National Malaria Control Programmes (NMCPs) in this region have repeatedly needed to make important policy changes, such as the replacement of frontline therapies, in order to maintain efficacy and contain spread. The large-scale analysis of parasite epidemiology at genome level can provide important insights to support NMCP decision-making.

The GenRe-Mekong Project has produced a platform for genetic surveillance of malaria, in which sample collection procedures are easily integrated into routine public health operations, enabling NMCPs in the GMS countries to conduct large-scale genetic surveillance projects. Samples from symptomatic patients are processed by SpotMalaria, a high-throughput system that produces a comprehensive set of genotypes comprising most known drug resistance markers, species markers and a genomic barcode. GenRe-Mekong processes these data, applying heuristics based on published evidence, to produce Genetic Report Cards, a compendium of genotypes and phenotype predictions used to map prevalence of resistance to multiple antimalarial drugs.

GenRe-Mekong has collaborated with NMCPs in five countries, and with large-scale research projects, processing over 12,000 samples from clinical cases. The monitoring of resistance markers has been especially valuable for NMCPs tracking the recent spread of multidrug-resistant strains across the region. Data from GenRe-Mekong have provided novel detailed knowledge about the geographical distributions of strains resistant to artemisinin combination therapies. Genetic surveillance can also shed lights on other important epidemiological aspects, such as assessment of the causes of a malaria outbreaks, or identification of imported parasites. Here, we show how a 2020/2021 outbreak in Attapeu Province, Laos was caused by the rapid clonal expansion of a new multidrug-resistant parasite population, showing signs of a selection sweep.

GenRe-Mekong provides detailed knowledge about drug resistance at a local level, and facilitates data sharing at a regional level, providing the public health community with valuable insights. The project provides a rich open data resource to benefit the entire malaria community.

S3_R3: Approaches to malaria elimination
Chairperson: Lorenz von Seidlein
Co-Chairperson: Frank Smithuis

Abstract 

Introduction: As malaria in Myanmar declined, the burden of disease primarily remains in remote areas with limited health infrastructure. Medical Action Myanmar introduced community health workers (CHWs) delivering early diagnosis and treatment for malaria in hard-to-reach communities in Mon state, East Myanmar. 

Method: A network of 172 CHW carried out 259,223 rapid diagnostic tests (RDT) for malaria between 2011 and 2018. We conducted a retrospective analysis to assess the decline in Plasmodium falciparum and Plasmodium vivax incidence and RDT positivity rates using negative binomial regression mixed effects models.

Results: The CHWs reached a population of 202,346 during the project period (2011-2018). Median (inter-quartile range) of monthly blood examination rate for the population covered was 1.53% (1.15%-1.85%) per month. The incidence of P. falciparum and P. vivax malaria reduced by 72% (95% CI: 66-77%) and 54% (95% CI: 47-59%) respectively per each year of CHW operation. Malaria RDT positivity rate for P falciparum and P vivax reduced by 71% (95% CI: 63-76%) and 52% (95% CI: 45-58%) respectively per year of CHW operation during this period.  

Discussion: The introduction of CHWs in remote communities improved access to diagnoses and treatment and led to a dramatic reduction of P. falciparum and P. vivax malaria. Falciparum malaria was practically eliminated, with only a single – imported – positive case detected from 55,722 RDTs during 2017-2018. Introduction of access to community based passive case detection, integrated in basic health care services, was enough to rapidly eliminate falciparum malaria.

[SC20-00213]

Abstract Type :

Symposium

Abstract Title :

Targeted mass drug administration and potential supplemental interventions for malaria elimination

Abstract :

Mass drug administrations (MDA), the presumptive antimalarial treatment of an entire population to clear the subclinical parasite reservoir, is an accepted strategy to accelerate malaria elimination. Between 2013 and 2017 we conducted a cluster randomised trial to assess the effectiveness of a MDA with dihydroartemisinin-piperaquine (DP) in 16 remote village populations in Myanmar, Vietnam, Cambodia, and the Lao People’s Democratic Republic. The primary outcome, P. falciparum prevalence by month 3, fell by 92% (from 5.1% [171/3,340] to 0.4% [12/2,828]) in MDA villages and by 29% (from 7.2% [246/3,405] to 5.1% [155/3,057]) in control villages. Over the following 9 months, the P. falciparum prevalence increased to 3.3% (96/2,881) in MDA villages and to 6.1% (128/2,101) in control villages (adjusted incidence rate ratio 0.41 [95% CI 0.20 to 0.84];p = 0.015). Individual protection was proportional to the number of completed MDA rounds. MDA was successful in reducing transmission, but the impact waned over time. The most likely explanations for the recurrence of malaria transmission following very low transmission include re-importation e.g. from surrounding villages and residual infections. Additional interventions will be needed to interrupt malaria transmission permanently. The potential and the challenges of including a malaria vaccine in MDA will be described.

S4_R4: Exploiting Wolbachia as a public health tool for arbovirus and filariasis control
Chairperson: Mark Taylor
Co-Chairperson: Grant Hughes

[SC20-00155]

Abstract Type :

Symposium

Abstract Title :

Development of alternative treatments for filarial diseases

Abstract :

Twenty diseases are recognized as neglected tropical diseases (NTDs) by World Health Assembly resolutions, including human filarial diseases. The end of neglected tropical diseases is now firmly embedded within the Sustainable Development Goals for 2030, under target 3.3. Filarial diseases still affect an estimated 200 million people worldwide and global efforts undertaken in recent decades have enabled elimination of filariasis as a public health problem. It is recognized that new drugs or drug regimens that kill or permanently sterilize adult filarial worms would significantly improve elimination timelines and accelerate achievement of the program goal of disease elimination. Drug development is, however, handicapped by high attrition rates, and many promising molecules fail in preclinical development or in subsequent toxicological, safety and efficacy testing; thus, research and development (R&D) costs are, in aggregate, very high. Drug discovery and development for NTDs is largely driven by unmet medical needs put forward by the global health community; the area is underfunded and since no high return on investment is possible, there is no dedicated drug development pipeline for human filariasis. Product development partnerships between the private sector, academic institutions and NGO´s are a vital part of enabling drug development in an otherwise underfunded area. In addition, repurposing existing drugs is one approach to filling the drug development pipeline for human filariasis. While the de novo development of anthelmintics is commercially not attractive for human use, development of new drugs for animal health is (relatively) financially rewarding and therefore much better supported and further advanced. Furthermore, drug repurposing typically has a higher chance of success with an already proven drug target in nematodes of veterinary importance. Some impressive examples demonstrate successful repurposing of veterinary drugs for human use, including benzimidazoles, IVM, praziquantel, moxidectin and triclabendazole. This approach has also been adopted by the DNDi, which is currently investigating emodepside (in collaboration with Bayer AG) and ABBV-4083 (a tylosin derivative, jointly developed in collaboration with the Anti-Wolbachia (AWOL) consortium and the pharma partner AbbVie). The third lead compound is the off-patent veterinary product oxfendazole for potential human use. Here we present a project update and discuss the considerations to enable patient`s access to new medicines.

[SC20-00221]

Abstract Type : Symposium Abstract Title : Large scale implementation of the WMP Wolbachia method Abstract : Dengue causes a substantial health and economic burden for half of the world’s population. The World Mosquito Program (WMP) is a not-for-profit initiative which aims to provide a safe, sustainable, and cost-effective new tool for preventing transmission of Aedes aegypti-borne diseases, including dengue, chikungunya and Zika. Our method involves the stable infection of Ae aegypti mosquitoes with the bacterial endosymbiont Wolbachia. Wolbachia infection blocks the ability of Ae. aegypti to transmit medically-important arboviruses including dengue, Zika and chikungunya, and manipulates the mosquito’s reproductive outcomes such that Wolbachia introgresses into wild Ae. aegypti populations following short-term releases,. Field releases in 11 countries have demonstrated successful and sustained wMel introgression into local Ae aegypti populations. A cluster-randomised trial in Indonesia and non-randomised field trials in multiple countries demonstrate the efficacy of wMel-infected mosquito releases for the control of dengue and other Aedes-borne diseases.

[SC20-00156]

Abstract Type :

Symposium

Abstract Title :

Exploiting native Wolbachia strains from Anopheles mosquitoes for malaria and arbovirus control.

Abstract :

The use of Wolbachia to control arboviruses in Aedes mosquitoes has been highly successful using both population replacement and suppression approaches. Efforts in Anopheles mosquitoes, which transmit malaria Plasmodium parasites and some alphaviruses, have been more challenging, likely due to the maladaptation between Wolbachia strains and Anopheles mosquitoes. Excitingly, we have demonstrated natural, stable, and vertically transmitted Wolbachia infections of Anopheles mosquitoes. Specifically, we have found two Wolbachia strains (wAnM and wAnD) residing within An. moucheti and An. demeilloni mosquitoes. Here we will present evidence for the infection and describe Wolbachia mediated pathogen blocking against arboviruses in Anopheles systems. Looking forward, we predict these two strains that naturally reside in Anopheles mosquitoes will be ideal candidates to use for transinfection into other medically-relevant Anophelines for vector control approaches.

S5_R5: Parasites of the gut: seeking vaccine and diagnostic candidates Chairperson: Malcolm Jones Co-Chairperson: Momar Ndao

[SC20-00191]

Abstract Type :

3. Symposium

Abstract Title :

Metabarcoding – One size fits most – from Acanthamoeba to Strongyloides

Abstract :

INTRODUCTION As new DNA-based technologies emerge and the number of laboratory technicians trained in traditional parasitological methods decrease, new methods for detection and differentiation of parasites should be developed and evaluated. For a number of years, an in-house molecular assay has been used in the Laboratory of Parasitology, Statens Serum Institut (SSI) Copenhagen, Denmark, to detect and differentiate nuclear ribosomal DNA, which can be used to taxonomic identification, in clinical and environmental samples. This presentation will focus on some of the strengths and drawbacks of this assay. METHODS Examples of data from individual cases, research studies, and from ONE Health European Joint Project method evaluations will be presented. RESULTS & CONCLUSION Compared with real-time PCR, the sensitivity of the metabarcoding assay appears somewhat lower, and for Giardia, sensitivity is extremely low. Meanwhile, the assay generally exhibits a breadth and specificity that makes it useful as a second-opinion screening tool. It has enabled the detection of parasites as diverse as Acanthamoeba spp., Plasmodium cynomolgi, Toxoplasma gondii, Babesia spp., Entamoeba spp., a variety of soil-transmitted helminths, Schistosoma spp., Strongyloides stercoralis, and many more, in a variety of matrices. The assay has moreover proven relevant for research into non-pathogenic intestinal parasites since it both has a non-inferior sensitivity, a high specificity, and data on parasites can be studied in the context of the bacterial taxa also detected by the assay. Another advantage is the fact that fasta files can be retrieved for all taxa identified.

[IC20-00435]

Abstract Type :

3. Symposium

Abstract Title :

Parasites diagnostic in the context of LMIC: Senegalese experiences

Abstract :

Introduction : In many developing countries, parasitosis is a major public health problem, some of which cause significant mortality, especially in children. National control programmes have been created to improve the fight against these diseases with significant success. Among the main strategies developed, the correct and rapid management of cases occupies an important place. The success of this strategy, however, depends on the correct diagnosis of cases. This is often not the case due to the limited resources available in these countries. There is therefore a significant gap at this level, which is even greater when we compare the urban and community levels within each country

Methods : Senegal is a perfect illustration of this. Indeed, the improvement of diagnosis with the use of RDTs at the community level has reduced the prevalence of certain parasitic diseases such as malaria, while others lack financially and geographically accessible diagnostic methods.

Results : The new methods available at the global level (molecular techniques, proteomics, etc.) are only available in a few research structures and exceptionally inhealth structures. The community level, is often a health desert in terms of diagnosis and only the implementation of POCs could help improve the situation.

Conclusion : Overall, parasite diagnosis in Africa compared to northern countries does not seem to have evolved significantly over the past decades, even if morbidity and mortality have decreased as a result of national strategies such as the MDA. More attention needs to be given by policy makers to achieve the elimination targets set for certain parasitic diseases

[SC20-00099]

Abstract Type : 3. Symposium Abstract Title : Molecular diagnostics of intestinal parasites in the endemic and non-endemic population Abstract : In recent years, a huge number of nucleic acid-based techniques (NAAT) have been developed for the diagnosis of gastrointestinal parasites. These NAAT’s provide increased sensitivity and specificity, and facilitate standardization of diagnostic procedures. In addition, DNA samples can be stored for longer periods and used for genetic characterization and molecular typing of both the pathogen and the host. As such, they can provide valuable additional information in surveillance investigations. A range of different techniques have been applied, each with their own methodological advantages and pitfalls. Laboratories were initially reluctant to implement NAATs, including PCR, within the range of available methods for the most accurate diagnosis of gastrointestinal parasites. Developing relatively simple algorithms is possible providing the most efficient use of resources and analytical staff. This makes it possible to use one or more multiplex real-time PCRs as first-line diagnostics. Until today, epidemiological and surveillance studies often focus on only one or a limited number of pathogens due to often species-specific diagnostic methods. While multiplex PCR makes it possible to detect multiple pathogens sensitively and specifically with one procedure and with one sample collection. Fortunately, quality assessment schemes are now available which allow any laboratory to test and compare their procedures with other laboratories.

[SC20-00071]

Abstract Type :

3. Symposium

Abstract Title :

Schistosomiasis vaccination: new approaches of antigen delivery

Abstract :

The impact of schistosomiasis has been estimated by the CDC to be the second most devastating parasitic infection behind malaria. Current control strategies rely mainly on chemotherapy with praziquantel. Although effective, praziquantel does not protect from reinfection and drug resistance is a rising concern, justifying the development of vaccines for Schistosoma spp. Conventional vaccines (subunit vaccines) are safe, but they require adjuvants to stimulate the immune system due to their weak immunogenicity. To overcome this limitation, our group has established a vaccination platform based on i) a replication-incompetent recombinant human adenovirus serotype 5 expressing Schistosoma mansoni (Sm) cathepsin B (CB) and ii) a live attenuated Salmonella enterica serovar Typhimurium strain, YS1646, that can be administered orally. SmCB is a cysteine peptidase predominantly found in adult worms and migratory larvae and is involved in the digestion of host blood macromolecules for nutrient acquisition. Our new vaccine approaches elicit strong humoral immunity and cellular effectors, balancing Th2 and Th1 arms of immunity and targeting SmCB-expressing larvae and adult worms.

S6_R6: Antimalarial drug developments Chairperson: Steve Ward Co-Chairperson: Pradipsinh K Rathod

[SC20-00045]

Abstract Type :

3. Symposium

Abstract Title :

Structure-activity relationship, property optimization, and target identification of a novel series of hypnozonticidal compounds developed from the hit MMV987

Abstract :

Hypnozoites are quiescent parasite forms in the liver of vivax malaria patients which active after a period of latency, causing a malaria relapse and onward transmission. Because these forms are undetectable and are only killed following treatment with an 8-aminoquinoline in combination with chloroquine, the hypnozoite reservoir is an important target for discovery and development of new antimalarial therapeutics. Using a medium-throughput, primary human hepatocyte culture platform, we screened 631 compounds previously found active against the liver stages of P. berghei, a rodent species of malaria, finding several hits with activity against P. vivax hypnozoites. A make-test cycle using our culture platform was used to probe the structure-activity relationship of hit compounds. Hit compound MMV987, a thioether-linked, indolyl-quinoxaline-substituted racemic mixture, displayed micromolar activity against P. vivax hypnozoites and emerged as the most developable hit compound. Physicochemical property profiling of MMV987 identified stability and solubility to be the main chemotype liabilities. Follow-up medicinal chemistry optimization focusing on improving potency, reducing lipophilicity, improving stability, and increasing aqueous solubility to yield frontrunners which displayed sub-micromolar potency and a desired property profile necessary for progression into animal models. While continued compound development is contingent on efficacy in small animal models and continued safety testing, ongoing efforts to characterize the mechanism of action of MMV987 aim to reveal the first hypnozoite-specific targets in this important lifecycle stage.

SC20-00068]

Abstract Type :

3. Symposium

Abstract Title :

Hit to Lead Optimisation of Antimalarial Plasmepsin X Inhibitors

Abstract :

The aspartic acid proteases Plasmepsin IX and X represent excellent targets for antimalarial drug development since in vitro and in vivo experiments have revealed that specific inhibitors block liver, blood and mosquito stages of Plasmodium spp. The broad and multi-stage activity coupled with a unique mechanism of inhibition and high barrier to resistance development makes cross resistance for inhibitors less likely in parasites that are already resistant against other antimalarials. All of these features make Plasmepsin IX/X inhibitors attractive targets for drug discovery. The presentation will cover medicinal chemistry approaches to the design and synthesis of novel, highly potent and metabolically stable beta hydroxyethyl amine inhibitors that have oral bioavailability in preclinical rodent models. With additional optimisation, the current series has the potential for progression into an effective oral treatment for malaria.

[SC20-00123]

Abstract Type :

3. Symposium

Abstract Title :

Development of novel antifolate antimalarials

Abstract :

Antifolate antimalarials, pyrimethamine (Pyr) in combination with sulfadoxine (SDX) used to be the first line drug for treatment of Plasmodium falciparum. However, parasites resistant to both antifolates emerged soon after drug application in the field. Cumulative point mutations in both dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS), the drug target of Pyr and SDX respectively, were identified as the major cause of drug resistance. In developing new effective antifolate antimalarials to overcome the present and future drug resistance, rational drug design based on structural information of enzyme-substrate/ligand interactions together with drug physico-chemical properties and pharmacokinetics was applied to identify potential drug candidate, P218, currently in clinical trials. More rational drug design is on-going to discover novel antifolate antimalarials for malaria control and elimination.

S7_R7: Fever in the tropics
Chairperson: Yoel Lubell
Co-Chairperson: William Schilling

[SC20-S7R7]

Abstract Type :

3. Symposium

Abstract Title :

The epidemiology of acute febrile illness in South and Southeast Asia: definition and applications

Abstract :

This presentation will provide an overview of the current evidence on the epidemiology of acute febrile illness in the South and Southeast Asian region and the associated knowledge gaps, opportunities, and challenges. Issues to be discussed will not be limited to quantifications of disease burdens, but also how epidemiological and related data can be used to improve the management of acute febrile illness from clinical and public health perspectives.

Following this, an ambitious multi-country and multi-component project to define and apply the epidemiology of acute febrile illness in this region (the South and Southeast Asian Community-based Trials Network) will be described. This project has a particular focus on rural areas at the peripheries of developing country health systems, aiming to fill not just the gaping holes in the evidence base relating to these under-served and under-resourced populations but also to develop practical and cost-effective solutions which will be highly impactful all the way up from the individual patient care to high-level health policymaking.

[SC20-00004]

Abstract Type :

3. Symposium

Abstract Title :

Advances in POCTs for Febrile Illness

Abstract :

Often clinical testing is done in specific laboratories resulting in a delay from a few hours to days before the result is reported to the clinical team. By this time the patient may already have been treated using broad range or non-specific drugs or given completely the wrong medication, putting their lives at risk. This lack of specified and tailored treatment also adds to the pressure of increasing drug resistance and the use of valuable resources in an already stretched environment. Point-of-Care Testing (POCT) enables the fast diagnosis of disease, close to the location of the patient. This allows a reduction of time to diagnosis, and allows treatment plans to be tailored to the patients’ unique needs prior to starting treatment. The aim of POCT is that the test is simple and easy to perform by the bed-side in the ward. Many POCT we use today evolved from much larger or more complex assays and equipment, and have only become available after recent advances in a number of different technologies. Technology is rapidly changing, allowing improvement to existing POCT as well as introduction of newer simpler assays for harder to diagnose diseases. I will review some of the current and new-to-market POCT technologies available for febrile illnesses, and look at what novel technologies may soon be available and what we may look forward to in the way of diagnostic testing and patient monitoring.

S8_R8: TB drug discovery and diagnostic tools Chairperson: Giancarlo Biagini

[SC20-00055]

Abstract Type :

3. Symposium

Abstract Title :

Virtual screening identifies novel ATPase inhibitors of MTB DNA gyrase

Abstract :

MTB DNA gyrase has been identified as promising target for tuberculosis drug design and discovery. In this study, we attempted to identify ATPase inhibitors of MTB DNA gyrase by structure and pharmacophore based virtual screening, subsequently validated by biological assays. The results revealed that indole and oxindole analogs are active against MTB with the MIC value of 6.2-100 μg/mL. These compounds showed moderate inhibition activity against MTB DNA gyrase by ATPase assay. MD simulations, binding energy calculations and binding interaction studies suggested that major interactions of its new inhibitor with ATPase binding site are hydrogen bond interactions and hydrophobic interactions. The obtained results provide the key information for lead optimizations for potential ATPase inhibitors of MTB DNA gyrase.

[SC20-00153]

Abstract Type : 3. Symposium Abstract Title : Hybridisation Approaches in anti-Tuberculosis Drug Discovery Abstract : Whilst tuberculosis (TB) prevalence and associated mortality are in decline, increases in cases of multidrug-resistant (MDR) and extensively drug resistant (XDR) TB threaten to reverse the progress of reducing the disease burden globally. All current treatments for TB involved complex and lengthy drug combinations for elimination of the latent Mtb population and managing potential resistant development, but patient compliance for complex and lengthy regimens can affect the treatment outcome significantly. Drug hybridisation is a medicinal chemistry strategy that is being explore extensively in recent years, for its potential to simplify treatment regimens and to manage or combat resistance in many diseases, particularly in infectious diseases. In this talk, a number of case studies of drug hybrids, either between approved drugs or with experimental drugs, as tool molecules for investigation of their anti-TB properties are presented and discussed. Through these examples, it may help to gain more understanding of modes of action/resistant of these hybrids, stimulate further studies using them and ultimately, resulting in developing hybrid drug candidates for the treatment of drug-resistant TB.

[SC20-00054]

Abstract Type :

3. Symposium

Abstract Title :

Discovery and Hit to Lead Optimization of Potent Inhibitors as Antituberculosis Agents

Abstract :

In this research, we applied structure based virtual screening validated by biological assays to identify new and potent inhibitors of two potential targets, InhA and PknB. Two compounds (AK-087/42718313 and AP-124/43238118) have been identified as the potential InhA inhibitors with IC50 values of 0.22 and 0.38 μM. Further, these two compounds are active against M. tuberculosis H37Rv with MIC of 12.5 and 25 μg/mL. In the case of PknB target, AE-848/42799159 and AP-124/40904362 showed the potential activity for enzyme inhibition (IC50 of 11.21 and 14.39 μM) and M. tuberculosis H37Rv (MIC of 6.2 and 50 µg/ml). Compounds identified as InhA and PknB inhibitors have been used as the template for rational design followed by chemical synthesis and biological assay, to optimize lead compounds. The promising compounds discovered from this work would be candidate molecules for tuberculosis drug.

S9_R9: Conquering the issue of low-density parasite-carriers for the last mile towards malaria elimination
Chairperson: Shigeyuki Kano
Co-Chairperson: Srivicha Krudsood

[SC20-00037] 

Abstract Type :

3. Symposium

Abstract Title :

Innovative technologies and strategies to ultimately eliminate malaria

Abstract :

Definitely, we cannot stop our effort to eliminate malaria even under this COVID pandemic. However, there are some challenges to malaria elimination such as existence of asymptomatic parasite carriers, wide spread of drug resistant parasites, outbreak of Plasmodium knowlesi malaria in Asia-Pacific region, changing biting behavior of vectors with their insecticide resistance, and in fact, movement and migration of people beyond borders. Asymptomatic or low-density parasite carriers are less likely to seek treatment and are missed by passive surveillance. Those carriers can be the source of infection by vector mosquitoes. We could say that this ice burg under the sea is the silent reservoir of transmission. Thus, we should have innovative technologies for seeing deep under the sea to know how big the iceberg is. A flowcytometry developed by Sysmex (XN-31) and a nucleic acid amplification test by Eiken (LAMP) are to be introduced in this symposium. Clinical performance of both diagnostic tests has now been verified in Mahidol University, Bangkok. The rate of diagnosis among children aged under 5 years for whom care was sought has to be increased in the hyper-endemic areas, but in low-endemic areas under elimination phase, mass surveillance, monitoring and evaluation (SME) may be needed to find out and treat the last parasite carrier to attain zero malaria. We believe that these sensitive diagnostic tests can be usefully accepted in each endemic setting and performed effectively for the elimination of malaria by the year 2030.

[SC20-00027]

Abstract Type :

3. Symposium

Abstract Title :

Introduction of malaria test using flow cytometry method, XN-31

Abstract :

The gold standard for malaria diagnosis is to prepare a blood smear for microscopy to identify Plasmodium species. However, this method is time-consuming and labor intensive, and requires skill to perform microscopic examination with high accuracy. Rapid Diagnostic Tests (RDTs) are widely used because they are easy to handle and can be performed in 15 minutes. However, the sensitivity of the RDTs is inferior to other methods. The PCR method has excellent sensitivity, but it takes 2-3 hours to obtain results. Sysmex Corporation has developed the automated hematology analyzer XN-31 to overcome these issues. The XN-31 can detect and quantify Plasmodium -infected RBCs to aid malaria diagnosis. The number of Malaria Infected RBC (MI-RBC#) is counted and %parasitemia (MI-RBC%) is calculated in about 1 minute. Information on Plasmodium species and their developmental stage can also be obtained for research purposes. The operator does not require skilled lab-techniques and is faster in producing results than the other conventional methods. Prompt diagnosis leads to proper treatment. The potential contribution of the XN-31 to malaria elimination will be pointed out in this symposium.

[IC20-00478]

Abstract Type :

3. Symposium

Abstract Title :

Feasibility of Malaria-LAMP system for malaria elimination

Presentation Type :

Oral
Abstract :

Introduction : In Malaria-medium and low-endemic countries, many malaria cases have low Plasmodium concentrations that it is difficult to be detected by conventional malaria testing methods. Early and sensitive detection of Plasmodium carriers is considered essential. This is because not only rapid treatment of infected persons but also prevention of secondary infection is necessary for malaria elimination.

Methods : Introduction to the performance of Malaria-LAMP.

Results : High sensitivity: detection of undetectable positive patients → targeted elimination. High specificity: species identification contributes to the selection of treatment. Ease of use: it can be operated by smear technicians with no genetic testing experience. Rapidity: Reduced testing time and quicker return of results to the patient. Conservation: operation in peripheral facilities in developing countries without a cold chain.

Conclusion : Malaria-LAMP, which detects malaria-infected individuals at an early stage with high sensitivity, is about 10 times more sensitive than the smear microscopy test method. Malaria-LAMP can contribute to malaria elimination in the future by detecting Malaria Plasmodium carriers of malaria-infected patients that have been missed by conventional smear microscopy.

S10_R10: The Armed Forces Research Institute of Medical Science: Fighting infectious diseases for 63 years through US and Royal Thai Army collaborative medical research
Moderator: MAJ Erica Lindroth
S11_R1: Collaborative malaria re search in South Asia
Chairperson: Pradipsingh K Rathod
Co-Chairperson: Vineeta Singh

[SC20-00125]

Abstract Type :

3. Symposium

Abstract Title :

Diversity and seasonal prevalence of Anopheline species in Southwest India.

Abstract :

Introduction: Vector biology research includes seasonal descriptions of primary mosquito vectors, with a focus on their habitats, feeding and resting behaviours, and susceptibility to Plasmodium infection. The state of Goa, located in the south western coastal belt of India, has recently undergone significant transformation due to accelerated urbanization to meet the demands of the Indian tourism industry. The present study focused on understanding seasonal variation of Anopheline species in different parts of Goa, and whether this corresponds with the level of local disease transmission. Methods: Mosquito collections were carried out using CDC light traps in nine different locations of Goa having variable malaria endemicity. The species diversity was analysed by the Shannon-Wiener diversity index among the study sites and habitats. Paired and unpaired t-tests were used to understand the seasonal significance of different Anopheline species. Results: With 432 traps, a total of 29,418 mosquitoes belonging to 48 species and 9 genera were captured from 9 study sites of North and South Goa districts. Of these, a total of 2,735 female Anophelines were captured. This included 15 species, including An. stephensi, An. culicifacies, An. fluviatilis and An. subpictus, the recognized vectors of malaria in Goa, and 11 additional species including An. jamesii, An. vagus, An. tessellatus, An. karwari, An. barbirostris, An. hyrcanus, An. jeyporiensis, An. aconitus, An. varuna, An. peditaeniatus, and An. pallidus. Of these, An. jamesii was found to be the most abundant species (43%), followed by An. stephensi (10%), An. vagus (9%), An. tessellatus (8%) and An. subpictus (7%). Among the dominant species, An. jamesii was caught in significantly higher numbers in monsoon than post-monsoon (p<0.05), while other seasons showed moderate abundance. An. stephensi collection was also significantly higher in monsoon season compared to other seasons (P<0.01). Other dominant species like An. vagus (P<0.05) and An. subpictus (P<0.01) was also significantly higher in monsoon than post-monsoon season. Thus, this study found significant differences in mosquito species richness between study sites. The Shannon diversity indices indicate that species diversity was highest in new construction sites and lowest in developed urban residential sites. Conclusion: Continuous entomological and epidemiological surveillance activities, involving the monitoring of population dynamics of Anopheline communities, show significant seasonal variations between mosquito species that can inform seasonal malaria transmission in Goa.

[SC20-00016]

Abstract Type :

3. Symposium

Abstract Title :

Collaborative Malaria Research in South Asia: Indian malaria parasites

Abstract :

Introduction The South Asia International Center of Excellence for Malaria Research (ICEMR) was set up by the US National Institutes of Health (NIH) in 2010 and has been studying malaria in India for over a decade. During this time the South Asia ICEMR has collected and processed regional parasites from malaria patients in different Indian study sites; analyzed and reported on region specific diversity in these parasites. The South Asia ICEMR study sites in the states of Goa, Maharashtra, Jharkhand and Assam differ in transmission intensity, species ratio (P. falciparum: P. vivax) as well as topography and demography profiles. This presents a unique opportunity to study a wide variety of parasite phenotype and genotype. Methods Clinical and demographical data were collected during the hospital based and household-based surveys along with blood samples from malaria infected patients. The blood samples were processed, cryopreserved and later used for experiments exploring region specific traits. Results South Asia ICEMR data informs about parasite phenotype and genotype associated with region specific malaria transmission patterns, evolving antimalarial resistance, pathogenesis of uncomplicated and severe malaria, as well as host biomarkers of recent infection. Conclusion The collaborative, multidisciplinary, integrated South Asia ICEMR program, with its study sites spread across India, is uniquely positioned to capture the heterogeneity and complexity of Indian malaria parasites. It thus plays a complimentary role to national and subnational stakeholders in describing malaria in India.

S12_R2: Advances in diagnosis of intestinal protozoan diseases
Chairperson: Jaco J Verweij
Co-Chairperson: Christen Rune Stensvold

[SC20-00098]

Abstract Type :

3. Symposium

Abstract Title :

E. histolytica, Giardia, Cryptosporidium – The Usual Suspects?!

Abstract :

Twenty-five years ago, the formal recognition of E. histolytica and E. dispar as two different, microscopically identical, species made it apparent to differentiate between the potential pathogenic E. histolytica and nonpathogenic E. dispar. Around the same time PCR-based methods were described using the genetic differences of the two species for differentiation of E. histolytica/E. dispar detected by microscopic examination. However, procedures of DNA extraction and PCR methods were laborious and time consuming. Gradually these methods became more user-friendly and with the introduction of probe-based real-time PCR making it possible to multiplex different pathogen targets the use of PCR-methods as first-line diagnostic came into reach. The flagellate Giardia, in industrialized countries one of the main non-viral causes of diarrhea, was the obvious candidate to include in a multiplex real-time. Speaking of Giardia, Cryptosporidium is usually not far away and thus was the most logical trio out there to use in most settings. The last decade, multiplex real-time PCR has been excepted as a first line diagnostic tool in patients presenting with diarrhea as well in epidemiological settings. Quality assessment schemes are available to warrant the their use in an accredited laboratory. Commercial assays in different formats and automation are expanding and new techniques such as next generation sequencing are around the corner.

[SC20-00078]

Abstract Type :

3. Symposium

Abstract Title :

Advances in the Diagnosis of Cyclosporiasis

Abstract :

Cyclospora cayetanensis is an emerging food and waterborne intestinal coccidian of humans endemic to tropical and subtropical regions of world (except Australia). Cyclosporiasis is characterised by abdominal symptoms and watery diarrhoea of days to months in duration. Outbreaks are common in the United States, Canada, and Europe, mostly attributable to imported fresh produce, particularly leafy salad vegetables, berries, and herbs. Traditional microscopic methods have a low sensitivity for the detection of C. cayetanensis oocysts in food and human faecal samples there are no identified antigens suitable for serological detection. The widespread adoption of commercial gastrointestinal pathogen multiplex real-time PCR panels in many diagnostic laboratories over the past seven years has resulted in a marked increase in detected cases in the United States and elsewhere. The regularity of common source outbreaks of cyclosporiasis has led to significant research into the development of genotyping markers for molecular epidemiological investigations. The development of effective tools was hampered by the highly genetic relatedness of C. cayetanensis isolates globally and the sexual recombination of the parasite. Several approaches have been trialled with varying degrees of efficacy. A mitogenome typing approach has been developed by the Food and Drug Administration has been developed and trialled. A machine learning based multi-target genotyping system has been developed by the Centers for Disease Control and Prevention has been more widely applied and validated. This presentation will briefly summarise these significant advances in diagnostics and genotyping for C. cayetanensis over the past decade.

[SC20-00086]

Abstract Type :

3. Symposium

Abstract Title :

‘Dientamoebiasis’ and ‘blastocystosis’ – how relevant are these terms?

Abstract :

The terms ‘blastocystosis’ and ‘dientamoebiasis’ appear in the scientific literature from time and time and would appear to indicate ‘infection’ or ‘symptomatic colonisation’ with the parasites (or endosymbionts) Blastocystis and Dientamoeba, respectively. In the following, I will summarise data reflecting the experience with these parasites in Denmark that might suggest that these terms should be used with some caution. The findings of relevant publications focussing on Blastocystis and Dientamoeba from the Laboratory of Parasitology, Statens Serum Institut, over the past 15 years were reviewed. From the results of the publications, the following main trends were identified: 1) Both Blastocystis and Dientamoeba were more common in the background population than in patients seeking medical care for acute or chronic gastrointestinal illness 2) Most children in Danish daycare centres may be colonised with Dientamoeba 3) The gut microbiota of those with Blastocystis and Dientamoeba (either alone or combined) are characterized by higher alpha diversity 4) Blastocystis carriers are less likely to have a lower abundance of Proteobacteria than non-carriers These findings could indicate that these organisms are rather endosymbionts than ‘true’ parasites. Hence, the relevance of referring to an individual with a Blastocystis-positive or Dientamoeba-positive stool test as having ‘blastocystosis’ and ‘dientamoebiasis’, respectively, might be limited in the best of scenarios. However, it should be emphasized that the epidemiological profile and clinical impact of Blastocystis and Dientamoeba carriage may differ in other parts of the world.

S13_R3: Community-based service delivery – an integral component of the health system for malaria elimination
Chairperson: Jane Achan
Co-Chairperson: Khin Thet Wai

[SC20-00181]

Abstract Type :

3. Symposium

Abstract Title :

Training malaria volunteers to deliver integrated community case management: Lessons learnt from rural Myanmar

Abstract :

Introduction: Malaria remains as a major public health burden, despite its declining trend in Myanmar. Rural communities have limited access to the health services, leading to limited access to early diagnosis and appropriate treatment for childhood illnesses. Methods: After the completion of a successful pilot in 2016-2017 at three townships in Sagaing Region, Myanmar National Malaria Control Program and Malaria Consortium introduced an integrated community case management (iCCM) approach through existing malaria volunteer (MVs) network at six townships in Sagaing Region in 2017-2019. We aimed to increase access to services for rural communities, strengthen an already established network of malaria volunteers and increase their motivation to continue in this role. Results: MVs were already trained to treat malaria in all ages. iCCM introduced further training to diagnose and treat common childhood illness such as pneumonia with simple antibiotics, diarrhea with Oral Rehydration Salts (ORS) and to identify malnutrition. Community dialogue was also implemented to educate communities on danger signs and when to seek healthcare for quality health services. The activities were supervised by the basic health staff (BHS) in collaboration with Malaria Consortium. Malaria Consortium initiated a mobile health open data kit (ODK) for real-time data reporting from general practitioners (GP) to strengthen current malaria surveillance system. Conclusions: iCCM approach proved as a useful alternative healthcare service delivery channel to ensure universal primary healthcare is delivered in most remote areas, addressing common childhood illness. Lessons learnt included importance of regular monitoring and effective supervision, systematic introduction of the iCCM training curriculum, acceptability and usefulness of regular feedback and reporting mechanisms, improving MVs’ motivation by community members, alleviating the workload of BHS, strengthening referral system and update of further treatment at the health center, required improvement of coordination between national and township level health workforces and the use of mobile health application by the GP.

[SC20-00117]

Abstract Type :

3. Symposium

Abstract Title :

The important role of a community network in Malaria Elimination in Cambodia

Abstract :

Cambodia has made considerable progress in reducing malaria incidence and mortality, strongly diminishing the malaria burden over the last decade and has a vision of a malaria-free country by 2025. As laid out in the National Strategic Plan for Elimination of Malaria (NSPEM) in the Kingdom of Cambodia, 2011-2025, the objective is to eliminate Plasmodium falciparum by 2023, and all other species by 2025. Hard-to-reach population, forest goers, mobile and migrant population in Cambodia are most at-risk of malaria due to their highly mobile nature in forested areas and across international borders, the limited access to any malaria services and their exposure to the vectors in the forest. The key approach within the National Malaria Program to reach these populations is to embed the program into the local communities. Village malaria workers and mobile malaria workers are recruited from local communities, often speak the local language of minorities, and build strong relationships with the target populations over time. Community members are strongly engaged in the ‘Last Mile Strategy’, the comprehensive national malaria elimination program, and are key actors in making the approach successful. Under the guidance of, and in close collaboration with the National Malaria Program CNM, Malaria Consortium – among other contributing partners – is offering community-based quality mobile malaria services to remote populations along the international Cambodian border. The adapted approach, aligned with the national malaria elimination approach, combines local knowledge with flexible and tailored active and reactive case detection strategies in the most remote areas, contributing to and accelerating the national goal of malaria elimination by 2025.

[SC20-00145]

Abstract Type : 3. Symposium Abstract Title : The future of vertical malaria-only community health worker programs: A case study from Lao PDR Abstract : Background: Community health workers (CHWs) contribute significantly to malaria control and elimination by extending coverage of malaria testing and treatment and collecting real-time data on febrile disease trends. In Lao PDR, CHWs routinely diagnose approximately 40% of malaria cases in the five high-burden southern provinces. Such levels of contribution are not uncommon across the region. Declining malaria incidence and a test positivity rate below 1%, however, present new challenges to community acceptability of singular disease services and the feasibility of vertical program management and sustained financing. Methodology: In 2019, the Center for Malariology, Parasitology and Entomology (CMPE) initiated a mixed-methods assessment of the country’s Village Malaria Worker (VMW) program in collaboration with Clinton Health Access Initiative. Routine surveillance and programmatic data were analyzed to quantify VMW contributions to malaria elimination objectives. Semi-structured interviews were conducted from central to VMW level to complement the quantitative datasets. Results: Findings and recommendations were organized across eight pillars: program governance and management; health system linkage and community engagement; scope of work; training; payment; supply chain; supervision and performance management; and information management. CMPE developed a workplan to advance recommendations in a phased approach over the coming years to (a) ensure continued functionality of the existing VMW network in high burden settings while (b) advancing integration of VMWs into primary healthcare infrastructure in order to sustain activity levels and prevent malaria resurgence. Policy Implications: As dedicated funding for malaria declines, ministries of health in and beyond Lao PDR must embark on the complex process of transitioning the management and financing of historically vertical, heavily donor-supported community health infrastructure to the broader public healthcare system.

[SC20-00122]

Abstract Type :

3. Symposium

Abstract Title :

upSCALE: Strengthening mobile health to improve disease surveillance and community-based services in Mozambique

Abstract :

Introduction: In Mozambique, the main providers of healthcare at the community level are community health workers (CHWs) — known locally as Agentes Polivalentes Elementares (APEs) — and they play a key role in rural areas where health facilities are scattered. Within their communities, APEs conduct health promotion activities and provide integrated community case management (iCCM) for malaria, pneumonia and diarrhoea to children aged 2–59 months. They treat all age groups for malaria and diarrhoea, and refer newborns and pregnant women with danger signs, as well as cases of acute malnutrition, to the nearest health facility. Methods: In 2017, their services were digitalized and expanded to include family planning, pregnancy tracking, antenatal care, postpartum care, healthy child check-ups, tuberculosis, and HIV patient follow-up for treatment adherence counselling, to form a package of care known as upSCALE. Since then, the number of APEs within upSCALE has grown to over 3,500 digitally enabled APEs across 7 out of 11 provinces in Mozambique. This number is expected to increase to 8,800 by 2024, according to the APE programme directorate within the MOH. Results: The upSCALE digital health platform has been developed to improve quality and coverage of health services at the community level by addressing three key APE programme challenges: inadequate adherence to clinical guidelines; insufficient supply of commodities; and lack of access to community health information. Conclusions: As the outcomes, the program improves (1) a digitised community health information system can facilitate improved quality of service delivery through more accurate diagnosis and, consequently, timely treatment; (2) upSCALE can strengthen community-level surveillance of disease outbreaks and trends through real-time data capture and data granularity; and (3) geographic information system mapping can support improved targeted resource planning and mobilisation.

S14_R4: Malaria vaccine development
Chairperson: Lorenz von Seidlein

[SC20-00192]

Abstract Type :

3. Symposium

Abstract Title :

The R21/Matrix-M™ malaria vaccine: results from phase II and III trials and future plans

Abstract :

Significant progress was made reecently in malaria vaccine development with the first WHO wider-use recommendation for a malaria vaccine, RTS,S/AS01. However, the planned supply of this vaccine from 2023 will be insufficient to meet the needs of the target population. R21/Matrix-M (R21/MM), a circumsporozoite protein-based vaccine, is the first malaria vaccine to date to reach the WHO-specified goal of ≥75% efficacy in African children over 2 years. A well-tolerated safety profile was also observed. High NANP-specific IgG levels were induced by vaccination which correlate with efficacy. In early 2021, a phase III double-blind, randomised controlled trial was initiated across five African sites in Kenya, Tanzania, Mali and Burkina Faso, with differing seasonal and perennial transmission patterns and burden of disease, in 5-36 month-old children. The trial is fully enrolled with 4800 participants, who received 3 vaccine doses, 4 weeks apart and are now receiving a booster dose one year later. The primary objective of efficacy at 12 months following the primary series of vaccinations at the seasonal transmission sites will soon be known, along with interim efficacy data from the perennial transmission sites. Ongoing safety data collected through the trial will also be discussed. Applications for WHO prequalification and a policy recommendation followed by initial programmatic deployment of R21/Matrix-M™ are planned for late September 2022 and over the next 12 months. The Serum Institute of India Pvt. Ltd (SIIPL) have committed to manufacturing >200 million doses at low-cost, annually, following licensure. This will meet the requirements for the target population to ensure that R21/MM can make a significant impact on the lives of children living in malaria endemic areas. The development, licensure and accelerated deployment of R21/MM will take us closer to the WHO’s 2030 malaria targets, as well as the goal of malaria elimination.

[SC20-00217]

Abstract Type :

3. Symposium

Abstract Title :

“Recent Advances in RH5-based Vaccines for Blood-Stage P. falciparum Malaria”

Abstract :

Recent Advances in RH5-based Vaccines for Blood-Stage P. falciparum Malaria Plasmodium falciparum malaria affects 200-300 million people annually, currently resulting in the death of about 0.6 million individuals. Thus, despite increasing implementation of control measures, the burden of malarial death and disease remains far too high. The most advanced subunit vaccine against P. falciparum, RTS,S/AS01, targets the invasive sporozoite-stage of the parasite lifecycle and has shown modest efficacy against clinical disease in young children. Vaccines against the parasite’s asexual blood-stage have the potential to complement RTS,S/AS01 or other next-generation pre-erythrocytic vaccines, thereby further reducing mortality, morbidity and transmission of malaria; however such a vaccine has proved elusive. Recently, we have developed next-generation vaccines targeting the reticulocyte-binding protein homologue 5 from P. falciparum (PfRH5) and its wider invasion complex. These highly conserved parasite proteins mediate an essential invasion pathway into the human red blood cell. Critical to this work has been the elucidation of how human antibody responses are able to neutralise parasite invasion to guide rational vaccine design, coupled with human experimental medicine studies. This talk will describe our on-going work to develop next-generation protein and virus-like particle-based vaccines that target PfRH5, and present data from our most recent Phase I/II clinical trials both in the UK and Africa. Professor Simon J. Draper Department of Biochemistry, University of Oxford E: simon.draper@bioch.ox.ac.uk W: https://draperlab.web.ox.ac.uk/

[SC20-00138]

Abstract Type :

3. Symposium

Abstract Title :

Progress in evaluation of sexual-stage targeting vaccines

Abstract :

Introduction: Transmission-blocking vaccines (TBV) target surface antigens of gametes and zygotes to interrupt transmission through mosquitoes. Among the antigens in the clinic, Pfs230 forms a complex with membrane-anchored Pfs48/45 on the gamete surface and plays a role in male gamete fertility, while Pfs25 is the major surface protein of zygotes. Pfs25 was the first candidate prepared as recombinant protein and yielded functional antisera in rodent studies, however Pfs25 candidates have yielded only weak or short-lived antibody responses and serum functional activity in malaria-naive and malaria-experienced vaccinees. Methods: Pichia pastoris-expressed Pfs25 and Pfs230 domain 1 (Pfs230D1) antigens were prepared at NIAID, NIH, conjugated to ExoProtein (EPA) and formulated in different adjuvants, then assessed in human trials under FDA IND. Results: When formulated in Alhydrogel®, Pfs230D1 generated higher transmission-blocking activity than Pfs25 in humans and monkeys but not mice. Pfs230D1 activity depends on complement, and a potent complement-dependent human mAb has identified a large, highly conserved neutralizing Pfs230D1 epitope on gametes. Pfs230D1-EPA has now advanced through Phase 1 and 2 field trials using adjuvants such as Alhydrogel®, AS01 or Matrix M™, including studies with University of Bamako that demonstrate vaccine efficacy to block parasite transmission to mosquitoes. Conclusions: Pfs230D1 is superior to Pfs25 for inducing serum transmission-blocking activity and has shown field efficacy to block parasite transmission. Future studies should compare Pfs230D1 to Pfs48/45 candidates, which have been produced in Lactococcus lactis at Serum Statens Institut as fusions with malaria antigens like GLURP R0 region (“R0.6C”) or Pfs230 pro-domain and CSP repeat sequences (“ProC6C”).

S15_R5: Zika and new approaches for its control: where are we after the pandemic
Chairperson: Albert Icksang Ko
Co-Chairperson: Rome Buathong
S16_R6: Melioidosis in Southeast Asia: current status and research
Chairperson: Vanaporn Withiekanun
Co-Chairperson: Narisara Chantratita

[SC20-00009]

Abstract Type :

3. Symposium

Abstract Title :

Tactical Implementation of Melioidosis Research in Myanmar Military Medical Corps

Abstract :

Melioidosis, caused by Burkholderia pseudomallei, was first discovered at Yangon General Hospital in 1911 in Myanmar. An English Pathologist Captain Alfred Whitmore, and his assistant C. S. Krishnaswamy from Indian Medical Service found this disease in the opium addicts in Yangon. Although it was first recognised in Myanmar, there were not many research works and reports on Melioidosis. In the Military Medical Services, Melioidosis is one of the important diseases since it is considered as Category B Select Agent by the United States Centres for Disease Control and Prevention. Myanmar Military Medical Corps also listed it in the prioritized diseases, but there was no significant activity on Melioidosis in practice. In 2011, Defence Services Medical Research Centre (DSMRC) was founded and became operational in the following year with the facilities including BSL-3 laboratories and next generation genome sequencing, where melioidosis was categorised among the higher priority groups in the strategic research plan. In the process of implementing Melioidosis research, building blocks on theory, training, clinical practice, epidemiology and collaboration were developed tactically. Partners include top-notch research scientists from Mahidol University, Mahidol Oxford Tropical Medicine Research Unit and University of Nevada, Reno. Research on Melioidosis is being carried out not only at DSMRC, but it has extended to involve clinicians and researchers from Defence Services General Hospital, Defence Services Medical Academy and Military Institute of Nursing and Paramedical Sciences. At the moment, research works on Melioidosis in the Myanmar Military Medical Corps cover from simple research to advanced molecular studies.

[SC20-00160]

Abstract Type : 3. Symposium Abstract Title : Biomarkers for melioidosis Abstract : Melioidosis is a severe tropical disease caused by Burkholderia pseudomallei. To identify biomarkers for predicting mortality in melioidosis, we characterized transcriptomes in prospectively-enrolled melioidosis patients and identified genes associated with outcome. Whole blood RNA-seq was performed in a discovery set of 29 melioidosis patients. Transcriptomic profiles of patients who did not survive to 28 days were compared with patients who survived, showing 65 genes were significantly up-regulated and 218 were down-regulated in non-survivors compared to survivors. Up-regulated genes in non-survivors were involved in myeloid leukocyte activation, Toll-like receptor cascades, and reactive oxygen species metabolic processes. Down-regulated genes were hematopoietic cell lineage, adaptive immune system, and lymphocyte activation pathways. RT-qPCR was performed for 28 genes in a validation set of 60 melioidosis patients, confirming differential expression between survivors and non-survivors. IL1R2, GAS7, S100A9, IRAK3, and NFKBIA were significantly higher in non-survivors compared with survivors (P < 0.005). The AUROCC of these genes for mortality discrimination ranged from 0.80 to 0.88. In survivors, expression of IL1R2, S100A9, and IRAK3 genes decreased significantly over 28 days (P < 0.05). A multi-biomarker model of plasma proteins including IL-1R2 was further developed in 78 melioidosis patients and mortality prediction was confirmed in an external validation set of 191 melioidosis patients. The biomarker model of three plasma proteins had similar or better 28-day mortality prediction compared to predictive models using clinical variables of organ failure. These data identify key pathways activated in lethal melioidosis and suggest that plasma biomarkers have potential clinical use in making decisions about triage, treatment, and referral of melioidosis patients.

S17_R7: Dengue pathogenesis: lessons learned from patients
Chairperson: Panisadee Avirutnan
S18_R8: Role of Simian malaria in malaria elimination
Chairperson: Sylvie Manguin
Co-Chairperson: Indra Vythillingam

[SC20-00069]

Abstract Type :

3. Symposium

Abstract Title :

Genetic and Phenotypic Differentiation of the Zoonotic Malaria Parasite Plasmodium knowlesi

Abstract :

Plasmodium knowlesi is a blood parasite of longtail and pigtail monkeys in Southeast Asia. The first natural human infection by this parasite occurred in a US Army surveyor in the forest of Pahang in 1965. In 2004, a large number of human knowlesi malaria was reported in Kapit, Sarawak. To date, more than 30,000 knowlesi malaria cases have been documented, mainly in Malaysian Borneo and Peninsular Malaysia. My studies on the molecular epidemiology of P. knowlesi based on haplotype network analyses of several genes (Duffy Binding proteins, PkA-type 18S rRNA, and cytochrome c oxidase subunit I, PkCOXI) revealed that P. knowlesi from Peninsular Malaysia and Malaysian Borneo are genetically distinct. This finding is recently augmented via full genome analysis conducted by other researchers. The next quest is to investigate whether this genetic dichotomy has resulted in phenotypic differences between the P. knowlesi from these two regions. One of the studies discovered significant difference in the binding level of erythrocyte binding protein (PkDBPαII) of P. knowlesi isolates from these two regions to human erythrocytes. It was also discovered that PkDBPαII binds stronger to human Duffy FyAB erythrocytes than to Duffy FyA erythrocytes. The clinical implications of these findings are discussed.

[SC20-00142]

Abstract Type :

3. Symposium

Abstract Title :

Macaque displacement and potential alteration in the dynamics of zoonotic malaria transmission

Abstract :

Anthropogenic changes in land use and habitat fragmentation are known to alter the dynamics, and increase the risks of zoonotic disease transmission. The displacement of sylvatic disease reservoirs from their natural habitat, their subsequent colonization into the peri-domestic environment and their close interactions with synanthropic animals, narrows the disease transmission interface. This substantially increases the risk of zoonotic spill-over from the sylvatic cycle. Wild macaques (Macaca spp.) are among the major natural reservoirs of zoonotic primate malaria caused by Plasmodium knowlesi. This disease is now recognised as a major and fatal zoonosis in Southeast Asia. Macaques are widely distributed throughout the region, and have successfully colonized many peri-domestic habitats. Anthropogenic land conversion has driven these primates from their natural habitats, and their wide ecological plasticity enables them to thrive and reproduce at rapid rates in new environments. Emerging data has shown that peri-domestic macaques have higher prevalence of P. knowesi infection, and human-induced changes in the landscape and forest fragmentation correlate with higher parasite prevalence in the reservoir host. These findings suggest that ecological pressures are among the important determinants of zoonotic disease transmission dynamics. A comprehensive understanding of regional spatial distribution patterns, habitat associations, and epidemiological risk factors of malaria among wild macaques will facilitate better prevention and control measures for this zoonotic diseases in Southeast Asia.

[SC20-00061]

Abstract Type :

3. Symposium

Abstract Title :

Spatial distribution and incrimination of vectors in relation to zoonotic transmission of malaria in Malaysia

Abstract :

Simian malaria especially Plasmodium knowlesi is now an emerging public health problem in Malaysia and is the predominant species affecting humans. Cases are occurring in the forest, farms and villages close to forest areas, where both the macaques and the mosquito vectors belonging to the Anopheles Luecosphyrus group are found. The vector density and sporozoite rates are higher in the forest and farms compared to the villages. Besides, knowlesi malaria, P. cynomolgi is also being reported. With the elimination of malaria, it is possible to see an increase in the number of simian malaria cases. Results have shown that with deforestation, the macaques have been displaced and are moving to forest fringe, plantations and villages. From limited studies it shows that the vectors have colonized certain ecological habitats and humans are being infected when they visit these sites. The vectors known to date are An. blalabacensis, An. cracens, An. hackeri, An. introlatus, and An. latens. The distribution of the vectors in various habitats and their dynamics are essential to effectively target intervention strategies and predict impacts of future environmental changes in relation to the disease transmission.

[SC20-00066]

Abstract Type :

3. Symposium

Abstract Title :

Simple and purification-free nucleic acid extraction method coupled with LAMP assay for rapid diagnosis of malaria

Abstract :

Malaria is usually diagnosed by either microscopy, rapid diagnosis test and/or molecular methods. Molecular methods are often used in diagnosis due to its adaptability and versatility, and species-specific primers can distinguish different species of Plasmodium. Loop mediated isothermal amplification (LAMP) assay has become a favourable and effective alternative as a molecular diagnostic tool in recent years. LAMP is highly sensitive, specific and rapid. However, in a point of care setting for the diagnosis of malaria, DNA extraction using conventional methods are time-consuming and complicated. Therefore, we used a simple filter paper-based method for DNA extraction followed by dipping directly into a LAMP assay for amplification. This would in turn reduce the time, cost and equipment needed to perform DNA extraction. A total of 77 malaria samples were included in this study. The DNA extraction method coupled with LAMP has a detection limit of 0.001% parasitemia. Clinical sensitivity of LAMP was compared with the results from conventional nested PCR and microscopy. Among 36 P. knowlesi, 3 were not detected using this method. This method has successfully amplified all P. falciparum (n=10), P. vivax (n=10) and P. malariae (n=1) positive samples. The 20 healthy blood samples did not show any amplification. With this, the DNA extraction method coupled with LAMP showed 94.7% sensitivity and 100% specificity. In conclusion, the method presented here allows amplification of Plasmodium DNA in a time and cost-effective manner. Diagnosis of malaria is more accessible and affordable with this method, it will be useful in resource limited areas.

IC20-S18R8]

Abstract Type :

3. Symposium

Abstract Title :
Clinical management of Plasmodium knowlesi malaria

Abstract:

Introduction :Plasmodium knowlesi is endemic throughout Southeast Asia, with human cases reported in all countries . P. knowlesi accounts for nearly all cases of human malaria in Malaysia. The severe disease from P. knowlesi is at least as high as that of falciparum malaria
.Fatal cases have been reported

Methods :123 patients with PCR-confirmed uncomplicated knowlesi malaria in 3 district hospitals in Sabah, Malaysia, were randomised to receive either artemether-lumefantrine (total dose 12 mg/kg of artemether and 60 mg/kg of lumefantrine) or chloroquine (25 mg/kg)

Results :Parasite clearance at 24h, which was achieved in 76% (95% CI 63–86%) of patients administered artemether-lumefantrine, compared to 60% (95% CI 47–72%) of those administered chloroquine (P = 0.06). Median parasite clearance was shorter after artemether- lumefantrine than chloroquine (18 vs. 24h, P = 0.02), and all patients were aparasitaemic by 48h. There were no treatment failures with either artemether-lumefantrine or chloroquine up to Day 42 of follow up

Conclusion :Recognition of the ability of P. knowlesi to cause severe disease is paramount for ensuring prompt initiation of effective treatment to prevent adverse outcomes. First line ACTs such as artemether-lumefantrine have been shown to be highly effective for treatment of uncomplicated disease. For severe disease, intravenous artesunate must be initiated without delay.

S19_R9: Emerging viruses: catching up with viral evolution and diversity
Chairperson: Prasert Auewarakul
Co-Chairperson: Kobporn Boonnak

[SC20-00173]

Abstract Type :

3. Symposium

Abstract Title :

Zika virus and the interferon response: A tale of two mechanisms

Abstract :

Zika virus (ZIKV) is a mosquito transmitted Flavivirus endemic in Thailand. While in most cases human infection with ZIKV is asymptomatic, or at worst mildly symptomatic, in some cases much more severe neurological consequences of infection can occur. In particular, when a pregnant woman becomes infected in the first or second trimester, the virus can pass across the placenta to infect the developing fetus. While this can have a number of consequences on fetal development, the most significant is microcephaly or abnormally small (more than 3 S.D below the mean) brain development. The strain of Zika virus circulating in Thailand has been shown to cause microcephaly as evidenced by a number of cases. Our laboratory (amongst others) has been able to isolate the virus from autopsy tissues of a fetus medically terminated for reasons of fetal defects including microcephaly. Analysis showed that this virus differs from the endemic virus at only a nine amino acids, but that it has a distinctly slower replication profile. Examination of the induction of the interferon response in both a cell line and in human neural cells differentiated from induced pluripotent stem cells showed that the faster growing fever virus triggered significantly greater interferon beta expression, as well as greater expression of a number of interferon stimulated genes. It has previously been proposed for dengue virus that fast replicating viruses are ones that “outrace” the immune response, while slower replicating viruses are those that minimally activate innate immunity, which is consistent with the results for ZIKV. Given the small number of amino acid differences, these two viruses will allow a detailed investigation of the interaction of ZIKV with innate immunity.

[SC20-00171]

Abstract Type :

3. Symposium

Abstract Title :

Finding antivirals for emerging viruses

Abstract :

Most antiviral drugs are pathogen-specific and active only on a narrow spectrum of closely related viruses. Consequently, antivirals are not readily available for newly emerging viruses. An effective antiviral is badly and urgently needed to mitigate the impact of an emerging virus, especially in a pandemic. Conventional drug development normally takes too long to respond to this urgent situation. The search for antivirals for COVID-19 employed two strategies: 1) drug repurposing based on in vitro screening data, and 2) further development of existing compounds developed for related viruses. Repurposed drugs can be divided into those act on viral mechanism and those act on host machinery. Those act on viral mechanism are viewed as broad spectrum antiviral and usually act on more conserved viral proteins such as RNA polymerase. Host-acting drugs often have a benefit of having broader spectrum and may be less prone to drug resistance. Although several host-acting drugs are promising, none has been proven clinically effective. Mechanisms of action of most of these drugs are not clearly defined. Understanding these mechanisms may pave the way for development of effective broad-spectrum antivirals. We are currently exploring the antiviral mechanism of common repurposed host-acting antivirals such as ivermectin using thermal proteomic profile approach.

Symposium Day 3 26 October 2022
S21_R1: PfSPZ vaccines: from conception to licensure to deployment to improvement
Chairperson: Stephen L Hoffman
Co-Chairperson: Thomas L Richie

[SC20-00140]

Abstract Type :

3. Symposium

Abstract Title :

PfSPZ Vaccine (radiation attenuated PfSPZ)

Abstract :

Introduction: In 2020 there were more deaths from malaria than any year since 2012. In 2021 the WHO recommended implementation of the malaria vaccine, RTS,S/AS01, which reduced Plasmodium falciparum (Pf) malaria hospitalizations in 920,000 infants by 21% but did not prevent infection or reduce mortality. Our goal is to develop a vaccine that reduces Pf deaths, hospitalizations, cases and infections by >90%. Sanaria® PfSPZ Vaccine, composed of aseptic, purified, live (metabolically active), radiation-attenuated, cryopreserved Pf sporozoites (PfSPZ) is our most advanced PfSPZ vaccine. Methods: Twenty-two clinical trials of PfSPZ Vaccine have been conducted in the USA, Germany, Netherlands, Indonesia and 6 African countries. The regimen is three doses of 9.0×105 PfSPZ administered by direct venous inoculation on days 1, 8 and 29. Results: PfSPZ Vaccine has proven remarkably safe and well tolerated. A meta-analysis of 12 randomized trials showed no differences in adverse event rates compared to blinded normal saline controls. Vaccine efficacy (VE) has been 100% against homologous CHMI, 78% against heterologous CHMI at 9-10 weeks and in a recent field trial in Mali 41% and 61% against Pf infection and 47% and 56% against clinical malaria during 1st and 2nd transmission seasons without boosting. VE was 64-85% against infection in women who became pregnant, and 49-57% during pregnancy. New trials are underway in Malian 6- to 10-year-olds and Indonesian soldiers. Conclusions. PfSPZ Vaccine is safe, blocks many Pf infections and reduces clinical malaria in Africa. These data will be presented as well as our plans for licensure.

[SC20-00137]

Abstract Type : 3. Symposium Abstract Title : Chemoattenuated whole sporozoite malaria vaccines: PfSPZ-CVac Abstract : Introduction. We seek to improve on the success of PfSPZ Vaccine, the first-generation radiation-attenuated P. falciparum (Pf) whole sporozoite (SPZ) vaccine that arrests during early liver-stage development and is remarkably well-tolerated. In three trials, we observed that PfSPZ Vaccine conferred significant efficacy to Malian adults when administered after presumptive antimalarial treatment. Here, we explored safety and efficacy of chemoattenuated PfSPZ, or PfSPZ-CVac. Methods. Non-attenuated PfSPZ Challenge at various doses was administered monthly 3 times under drug cover with either pyrimethamine (PYR) or chloroquine (CQ) that arrest/kill early liver-stage or blood-stage parasites, respectively. CQ was administered weekly and PYR was administered either same day (Mali) or 2 and 3 days after (Mali and US) PfSPZ inoculation. Efficacy was assessed against controlled infection (CHMI) in malaria-naïve US adults or against natural infection in malaria-experienced Mali adults. Results. At 2×105 PfSPZ dose, CVac(CQ) protected 6/6 (100%) and CVac(PYR) protected 7/9 (77.8%) healthy US adults against heterologous CHMI three months post-immunization; protection was strongly dose-dependent for CVac(PYR). At 4×105 PfSPZ dose, CVac(PYR Day 0) given as a primary series with booster dose one year later protected healthy Malian adults against natural infection over 2 malaria seasons. Conclusions. PfSPZ-CVac efficacy against heterologous parasites is dose-dependent, durable, , and achieved at 4.5-8-fold lower dose than PfSPZ Vaccine. CVac(CQ) conferred an unprecedented level of protection against heterologous CHMI. CVac(PYR) has protective efficacy in the field, a first for chemoattenuated PfSPZ. Further development should compare CVac(CQ) versus CVac(PYR) field efficacy at increased doses and PfSPZ-drug co-formulation for safety.

[SC20-00152]

Abstract Type :

3. Symposium

Abstract Title :

PfSPZ Vaccine Deployment, Including P. falciparum Elimination Campaigns

Abstract :

After the positive recommendation by the World Health Organization supporting the first malaria vaccine RTS,S/AS01 to be used in children in Africa, renewed efforts have been made to further develop other candidate malaria vaccines for Plasmodium falciparum (Pf) including the whole sporozoite (SPZ) vaccines that are radiation, chemically or genetically attenuated (PfSPZ Vaccine, PfSPZ-CVac and PfSPZ-GA, respectively). More than 30 clinical trials in the USA, Europe, Indonesia and six African countries have shown PfSPZ-based vaccines to be safe and well-tolerated including in infants, children and HIV+ adults. Sustained (6-18 month) protection against naturally transmitted Pf malaria infection has been shown with PfSPZ Vaccine (4 trials) and PfSPZ-CVac (1 trial). Because PfSPZ vaccines induce potent immune responses targeting the sporozoite and liver stages of the life cycle and completely prevent blood stage infection, they meet criteria for classification as VIMTs, or vaccines to interrupt malaria transmission. The development plan following licensure is to deploy PfSPZ vaccines in mass vaccination programs (MVPs) to eliminate malaria from defined geographic regions. This will require concurrent mass drug treatment to eliminate the human reservoir of infection. Although no MVPs have been undertaken to date, the plan is to conduct cluster randomized trials, potentially using a stepped wedge design, of villages receiving different vaccine treatments, to demonstrate the safety and feasibility of regional malaria elimination. Potential targets are Bioko Island in Equatorial Guinea and Zanzibar or coastal areas in Tanzania. These strategies and associated logistical, safety and ethical considerations will be discussed.

[SC20-00139]

Abstract Type :

3. Symposium

Abstract Title :

Bioreactor production of PfSPZ in vitro without mosquitoes

Abstract :

Introduction. A highly effective vaccine is needed for prevention and elimination of malaria. The only immunogens shown to have > 90% protective efficacy against human malaria are Plasmodium falciparum (Pf) sporozoites (PfSPZ) manufactured in mosquitoes (mPfSPZ). The capacity to produce infectious PfSPZ in vitro (iPfSPZ) without mosquitoes would dramatically enhance PfSPZ vaccine development. Methods. Using 8-well chamber slides, 12-well plates, and 3.2 mL and 20 mL hollow fiber cartridge bioreactors, we systematically assessed impact of culture media, insect-derived feeder cells, and matrices on quantity and quality of iPfSPZ. Results. We produced billions of iPfSPZ. Fresh and cryopreserved iPfSPZ invaded human hepatocytes in culture and developed to mature liver stage schizonts expressing Pf merozoite surface protein 1 (PfMSP1) in numbers comparable to mPfSPZ. When injected into FRGhuHep mice containing humanized livers, iPfSPZ invaded the human hepatocytes and developed to PfMSP1-expressing late liver stage parasites at 45% the quantity of mPfSPZ. Human blood from FRGhuHep mice infected with iPfSPZ produced erythrocytic stage parasites in culture, and gametocytes developed to PfSPZ when fed to mosquitoes. The iPfSPZ had a similar profile of expressed genes in preliminary RNA-seq and qPCR studies, but expression level of iPfSPZ was in general lower than in mPfSPZ. Conclusions. We can produce large numbers of infectious iPfSPZ that fully develop in vitro and in vivo, but need to optimize their quality, consistency, and purification. The goal is inexpensive, large-scale manufacture of the iPfSPZ for mass vaccination programs to eliminate Pf malaria as a major cause of morbidity and mortality.

S22_R2: Roll back dengue
Chairperson: Usa Thisyakorn
Co-Chairperson: Sutee Yoksan

[SC20-00042]

Abstract Type :

3. Symposium

Abstract Title :

Establishment Of Asia Dengue Voice And Action (ADVA) Dengue Task Force To Prioritize Dengue Preparedness And Responsiveness In Asia

Abstract :

At the inaugural ADVA Task Force meeting held in June 2022, an advisory group comprising of multi-disciplinary stakeholders (academics, clinicians, scientists, epidemiologists, vaccine experts, environmentalists, digital healthcare experts and industry partners) finalised the proposal to establish an ADVA Dengue Task Force to consolidate dengue control efforts across Asia. The ADVA Task Force is intended to be a network of stake-holders to consolidate dengue preparedness in Asia. The ADVA Dengue Task Force will comprise of working groups responsible for various aspects of dengue control including, Surveillance, Data harvest and sharing, Diagnostics, Case management, Vaccine advocacy, Education and training, Community engagement, and Social sciences and Industry partnership. Immediate priorities identified by the Task Force include improvement in diagnosis and case management, strengthening of surveillance, development of strong dengue database, enhancement in funding and resource allocation and continued research and vaccine advocacy. A policy shaping group will be established first to focus on integrated dengue management. The ADVA Dengue Task Force puts forth a strong “Action Plan” to address the overarching burden of dengue through an integrated and holistic effort to achieve the WHO 2021 target of zero dengue deaths by 2030

[SC20-00225]

Abstract Type :

3. Symposium

Abstract Title :

World Dengue Day – a call to action

Abstract :

Dengue is a global public health burden affecting over 120 countries. An alarming 5.2 million dengue cases were recorded in 2019 [1]. Though 50% of the world’s population is at risk of dengue, Asia contributes 70% of the global dengue burden [1]. The World Health Organization (WHO) target for 2021–2030 Global Strategy for Dengue Prevention and Control is to reduce the dengue case fatality rate to 0% by 2030 [2]. To achieve this target, dengue must be acknowledged as a collective threat. Global collaborative efforts are needed to strengthen dengue preparedness, prevention, and control. Commemorating the 2021 ASEAN Dengue Day and advocacy for World Dengue Day, the International Society for Neglected Tropical Diseases (ISNTD) and Asian Dengue Voice and Action (ADVA) Group jointly hosted the ISNTD-ADVA World Dengue Day Forum–Cross Sector Synergies in June 2021. The international forum highlighted the urgent need for multisectoral partnerships between health, environment, and education ministries, the private sector, and the community for effective integrated dengue control across the globe. The forum called on the United Nations and WHO to establish a World Dengue Day to prioritize global awareness and preparedness in the fight against dengue (Fig 1). The petition for World Dengue Day has to date gathered over 29,000 signatures from dengue stakeholders across 110 countries (https://www.isntd.org/world-dengue-day).

[IC20-00549]

Abstract Type :

3. Symposium

Abstract Title :
Current management of severe dengue

Abstract :

Introduction : Dengue infection is among the most common causes of hospital admission, death, and disability in children in the Tropics. Recently, the age group of dengue infection has shifted to adolescents and adults. Data from Southeast Asia have shown that the mean age of reported dengue cases has increased from 5–9 years to older children and adults. In Thailand, affected adults over 15 years of age comprise 30–40% of dengue cases . Plasma leakage is the hallmark of severe dengue infection and leads to DSS. Until the present time, there has been no specific treatment for this condition. Hemodynamic optimization is the only mainstay treatment as supportive treatment during this critical period. The aim of this article is to review the most up-to-date knowledge of critical care management focusing on fluid management, choice of vasopressor, and target blood pressure in severe adult dengue infection.

S23_R3: Integrated approaches to insect vector control
Chairperson: Janet Hemingway
Co-Chairperson: Rudra Pratap Singh

[SC20-00146]

Abstract Type :

3. Symposium

Abstract Title :

Entomological surveillance for validation of visceral leishmaniasis elimination

Abstract :

Following operational research in 2015 the Indian visceral leishmaniasis (VL) elimination programme changed its vector control policy from indoor residual spraying (IRS) with the insecticide DDT applied with stirrup pumps to alpha-cypermethrin applied with compression pumps. In order to determine the impact of this policy change in 2016 eight sentinel sites were established in the VL endemic States, Bihar, Jharkhand, and West Bengal. These sites have since then continuously monitored for key entomological indicators including the vector, Phlebotomus argentipes, abundance, insecticide resistance, insecticide resistance mechanisms, infectivity in the vector, coverage and quality of IRS, and case incidence. WHO insecticide resistance tests have shown P. argentipes are susceptible to all tested insecticides papers including alpha-cypermethrin 0.05%, except for DDT 4% where high level of resistance was detected 40% mortality. IRS coverage with alpha-cypermethrin has increased to over 80% in all sites, with Bihar reaching 89.6% coverage and Jharkhand is 93.5% in 2021. This has resulted in a decline of Ph. argentipes abundance to <1/ trapped/ house/night, and xenomonitoring of infection of P. argentipes with the parasite Leishmania donovani has resulted in no infected sandflies being detected in past two years. This reduced transmission, along with improved case detection and treatment, have resulted in the VL elimination target of less than 1 case per 10,000 that has been reached in all the blocks associated with the sentinel sites. Presently only 8 blocks across the 4 endemic States remain above the VL elimination target.

[SC20-00096]

Abstract Type :

3. Symposium

Abstract Title :

Development of a new diagnostic Sensor for IRS Quality Assurance

Abstract :

There are 200 million people at risk of visceral leishmaniasis (VL) globally; 65 million live in India and the majority of them in the State of Bihar. VL is fatal, if left untreated. Malaria is endemic in >30 countries and 200,000 children die from the disease annually. The VL and malaria parasites are transmitted through infected female insect bites which require a bloodmeal to reproduce. VL and malaria are controlled by a World Health Organisation (WHO) insecticide Indoor Residual Spraying (IRS) programme. It functions primarily by killing endophagous mosquitoes when they land on sprayed surfaces, as well as by deterring feeding mosquitoes from entering the house completely. On the other hand, it has been highlighted that the IRS spraying is not done particularly well as there is often under dosing. The current WHO recommendation for Quality Assurance is to use live insect bioassays on sprayed walls – this is impractical, so there is no real Quality Assurance. The developed hand held sensor allows Quality Assurance by the immediate read out of data, so that remedial action can be taken to improve IRS. The sensor was successfully trialled during field studies in over 50 houses situated in different villages in India.

[SC20-00105]

Abstract Type :

3. Symposium

Abstract Title :

Operational implementation of IRS diagnostics for VL and malaria control

Abstract :

Indoor residual spraying is an essential tool for malaria control and the major control method for visceral leishmaniasis in Asia. DDT spray quality was often assessed by visual inspection as the spray leaves a white residue on the walls. WHO recommend live insect bioassays with susceptible insects, but this is almost never carried out due to logistical problems. HPLC assessment is the other recommended method, but this is costly and there is a significant gap between sampling and results. In 2005 IVCC sponsored the development of chemical assessment diagnostics for IRS. These have had limited uptake in operation IRS programmes such as those in Equatorial Guinea. A new generation of diagnostics is now being developed which will allow rapid non-invasive assessment of insecticide concentrations on walls. The impact of these diagnostics on being able to rectify problems with IRS will be discussed.

S24_R4: Triple artemisinin combination therapies for the treatment of drug resistant falciparum malaria
Chairperson: Arjen Dondorp

[SC20-00108]

Abstract Type :

3. Symposium

Abstract Title :

Results of the TACT-CV and TRAC II trials

Abstract :

Artemisinin and partner-drug resistance in Plasmodium falciparum are major threats to malaria control and elimination. Triple artemisinin-based combination therapies (TACTs), which combine existing co-formulated ACTs with a second partner drug that is slowly eliminated, might provide effective treatment and delay emergence of antimalarial drug resistance. Between 2015 and 2020, 1410 patients in Asia and Africa with uncomplicated falciparum malaria were randomised to treatment with a TACT or its corresponding ACT. The primary endpoint was efficacy, defined by 42-day PCR-corrected adequate clinical and parasitological response. Primary analysis was by intention to treat. A detailed assessment of safety and tolerability of the study drugs was done in all patients randomly assigned to treatment. Dihydroartemisinin–piperaquine plus mefloquine and artemether–lumefantrine plus amodiaquine TACTs are efficacious, well tolerated, and safe treatments of uncomplicated P falciparum malaria, including in areas with artemisinin and ACT partner-drug resistance. The mutual protection by the two partner drugs could prolong the useful therapeutic lifetime of the drugs used, providing an alternative first-line treatment in areas with artemisinin-resistant falciparum malaria in southeast Asia, and elsewhere.

[SC20-00124]
Abstract Type :

3. Symposium

Abstract Title :

Pharmacokinetic interactions of triple ACTs

Abstract :

Introduction: The first-line therapy for uncomplicated falciparum malaria is artemisinin-based combination therapies (ACTs). Artemisinin resistance was first reported in 2009 and has since been compounded by ACT partner drug resistance. New antimalarials are not expected to come to market for several years. An alternative is the use of triple ACTs (TACTs), chosen to combine the short-acting artemisinin component with two longer-acting partner drugs. Here we evaluate potential drug-drug interactions of artemether-lumefantrine-amodiaquine and dihydroartemisinin-piperaquine-mefloquine. Methods: Three clinical trials have been conducted to evaluate these TACTs (NCT02324738; NCT02453308; NCT03355664). These trials were used to evaluate potential drug-drug interactions between the partner drugs lumefantrine-amodiaquine and piperaquine-mefloquine. Non-compartmental analysis and nonlinear mixed-effects modelling was used to characterise the pharmacokinetic properties of these drugs, with particular focus on drug-drug interactions. Results: The non-compartmental analysis showed no evidence of a drug-drug interaction between piperaquine-mefloquine when administered as part of the TACT. However, a trend of lower exposure to dihydroartemisinin was seen when given as part of the TACT. Somewhat conflicting results was seen when administering artemether-lumefantrine-amodiaquine, resulting in a trend towards decreased peak levels of artemether/dihydroartemisinin when administered as part of the TACT. Furthermore, one study showed a substantially decreased exposure to lumefantrine when administered as part of the TACT, while another study showed no drug-drug interaction. Population-based modelling is underway to evaluate and characterised these interactions further. Conclusion: The studies performed here suggest that TACTs are well-tolerated, safe and effective treatments, and that potential interactions should not hinder the evaluation and development of these TACTs.

[SC20-00044]
Abstract Type :

3. Symposium

Abstract Title :

Ethical considerations in deploying Triple Artemisinin-based Combination Therapies for malaria: An analysis of stakeholders’ perspectives in Burkina Faso and Nigeria

Abstract :

Background Artemisinin-based combination therapies (ACTs) are the recommended treatment for uncomplicated Plasmodium falciparum malaria in all malaria endemic countries. Artemisinin resistance, partner drug resistance, and subsequent ACT failure are widespread in Southeast Asia. The more recent independent emergence of artemisinin resistance in Africa is alarming. In response, triple artemisinin-based combination therapies (TACTs) are being developed to mitigate the risks associated with increasing drug resistance. Since ACTs are still effective in Africa, where malaria is mainly a paediatric disease, the potential deployment of TACTs raises important ethical questions. Methods We conducted a qualitative study in Burkina Faso and Nigeria assessing stakeholders’ (policy makers, suppliers and end-users) perspectives on ethical issues regarding the potential future deployment of TACTs through 68 in-depth interviews and 11 focus group discussions. Findings Some respondents suggested that there should be evidence of local artemisinin resistance before they consider deploying TACTs, while others suggested that TACTs should be deployed to protect the efficacy of current ACTs. Respondents suggested that additional side effects of TACTs compared to ACTs should be minimal and the cost of TACTs to end-users should not be higher than the cost of current ACTs. There was some disagreement among respondents regarding whether patients should have a choice of treatment options between ACTs and TACTs or only have TACTs available, while ACTs are still effective. The study also suggests that community, public and stakeholder engagement activities are essential to support the introduction and effective uptake of TACTs. Conclusion Addressing ethical issues regarding TACTs and engaging early with stakeholders will be important for their potential deployment in Africa.

[SC20-00118]
Abstract Type :

3. Symposium

Abstract Title :

The Development of Triple Artemisinin-based Combination Therapies (DeTACT) project

Abstract :

Introduction: De novo emergence of artemisinin-resistant Plasmodium falciparum parasites was recently documented in Rwanda and Uganda. More than a decade ago they were first identified in Southeast Asia, and alarming failure rates with dihydroartemisinin-piperaquine followed. New antimalarial drugs may not be available within the next 5 years. Triple Artemisinin-based Combination Therapies (TACTs), combining artemisinin with two currently available antimalarial drugs, could be a safe, effective, and rapidly deployable alternative. The Development of Triple Artemisinin-based Combination Therapies (DeTACT) project aims to enable the introduction of TACTs as first-line treatment for malaria. Methods: The DeTACT project comprises 6 work packages (WPs). WP1: Development of 2 TACTs. WP2: Conduct a randomized, controlled, partially blinded, non-inferiority clinical trial to assess the safety, tolerability and efficacy of 2 TACTs. WP3. Modelling future benefits of TACTs. WP4. Ethical considerations of deploying TACTs when ACTs are still effective. WP5. Market positioning of TACTs. WP6. Communication and stakeholder engagement. Results: Artemether-lumefantrine+amodiaquine (AL-AQ) and artesunate-mefloquine+piperaquine (AS-MQ-PPQ) are being tested against AL+placebo and AS-MQ+placebo in 8 African and 3 Asian countries. Preliminary safety and tolerability results will be presented. Mathematical modelling indicates that deploying TACTs could delay or prevent artemisinin resistance. Bioethical and market positioning studies indicate readiness to accept TACTs should they prove clinically better than ACTs. Communication strategies have been developed for better engagement of stakeholders. Conclusion: Current safety, tolerability and efficacy data of TACTs are promising. Deploying TACTs early will delay artemisinin resistance. Engaging early with key stakeholders will lead towards successful deployment and uptake of TACTs in the future.

S25_R5: Malaria and other vector-borne diseases in mobile and hard to reach population
Chairperson: Helene Hiwat

[IC20-00413]
Abstract Type :

3. Symposium

Abstract Title :

Malaria prevention and control in mobile and hard to reach populations in Burkina Faso

Introduction : Burkina Faso is experiencing security issues in several northern regions since 2015. This security concern has triggered massive population displacement of about 1.85 millions according to UNOCHA (that is almost 10% of the country’ population) and the closure of about 185 health facilities centers. The security risk has resulted in huge difficulties in implementing malaria prevention and control interventions (patient care, supply of antimalarial drugs, ITNs distribution and others).

Methods : In this health context, the National Malaria Control Programme (NMCP) has introduced new mitigating measures to make malaria prevention and control services accessible to the affected populations.

Results : • pre-transfer treatment • inclusion of internally displaced persons (IDPs) in all control interventions with support of humanitarian structures, • communication and awareness-raising in gathering areas, using town criers • training/sensitization of health workers on their neutrality in risk areas, • single supply of antimalarial products (ACTs, RDTs) for seasonal malaria chemoprevention (SMC), • electronic payment of local delivers in charge of SMC and LLIN campaigns, instead of cash payment to avoid robberies and attacks.

Conclusion : These massive displacements have urged an adaption of the health system to trigger an adequate implementation of malaria control interventions amongst these populations but the challenges are overwhelming despite the commitment and patriotic surge of health and community workers. It is therefore urgently necessary that malaria prevention and control programmes investigate and develop innovative strategies that would allow these affected populations to have equitable access to health, all within the context of the “Peace for Health” call from the World Health Assembly in 2022.

S26_R6: Stopping future pandemics through the strengthening of One Health citizens Moderator: Dee Bourbon
S27_R7: Malaria vectors: surveillance and resistance
Chairperson: Sylvie Manguin
Co-Chairperson: Theeraphap Charoenviriyaphap

[IC20-00298]
Abstract Type :

3. Symposium

Abstract Title :

Monitoring insecticide resistance in large-scale clinical trials evaluating spatial repellent efficacy: challenges and insights

Abstract :

Introduction : Two cluster-randomized clinical trials were conducted to estimate protective efficacy of a pyrethroid-based spatial repellent product against malaria in Sumba, Indonesia and Aedes-borne viruses in Iquitos, Peru. A component of each trial was to evaluate insecticide resistance status of target mosquito vectors at baseline, intervention and post-intervention periods to describe product impact on status change.

Methods : Permethrin and transfluthrin insecticide susceptibility assays were performed using WHO tube and CDC bottle test protocols. In Indonesia, evaluations used 3- to 5-day old, F0 mixed anopheline species from 13 of 24 study clusters. In Peru, Aedes aegypti eggs were collected from all 26 study clusters with a F3 generation of a genetically diverse Ae. aegypti strain serving as a control population and pyrethroid susceptible USDA Rockefeller strain as the reference comparator.

Results : Based on assumptions of predominately pyrethroid-susceptible populations of anophelines in our Indonesia trial site, there was no conclusive evidence for development of phenotypic resistance to pyrethroids between pre- and post-intervention periods. Results from Peru indicated the presence of resistance in Ae. aegypti populations in our study area, although causality due to the spatial repellent intervention could not be determined given reduced susceptibility in placebo clusters was also observed suggesting other sources of selection pressure could have contributed to the observed phenotype shift.

Conclusion : Building evidence on insecticide resistance in large-scale trials for use towards public health assessment of new vector control interventions can be expensive and time-consuming. Added value of such monitoring must be balanced against the ability to rigorously interpret entomology outcomes.

[SC20-00064
Abstract Type :

3. Symposium

Abstract Title :

Review on new approaches for malaria vector control

Abstract :

Introduction: Innovative vector control (VC) approaches need to be developed to control outdoor malaria transmission and the increasing number of insecticide resistant vector populations. Current and most employed strategies for malaria VC still rely on indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs). However, they have no effects on outdoor transmission and growing levels of insecticide resistance are threatening the efficacy of IRS and LLINs. Also, malaria vectors are showing increasing changes in their behavior in response to the wide use of indoor VC interventions causing residual malaria transmission. This poses new challenges as conventional tools are not effective and the goal of malaria elimination jeopardized. Methods: Behavioral changes (biting time, proportion indoor/outdoor vectors, Anopheles species composition) threaten the progress made to control malaria transmission and must be studied in order to implement the proper VC strategy. New approaches target mainly adults (ATSB, eave tubes, SIT, repellents), but larvicides can also be useful in specific contexts. Immunological anti-salivary markers represent also valuable tools assessing the effectiveness of VC methods. Results: A review of existing and novel approaches used to target outdoor-biting malaria vectors and the method to assess their effectiveness is presented. A focus is given to the development of effective and eco-friendly VC methods to reduce the burden of mosquito-borne diseases. Conclusion: Integrated vector management needs to be widely used to appropriately target indoor and outdoor malaria vectors. Antibodies specific to Anopheles salivary proteins constitute an efficient indicator for evaluating and comparing the effectiveness of malaria VC methods.

[SC20-00218]
Abstract Type :

3. Symposium

Abstract Title :

Repellent study in GMS: a case study from Thailand

Abstract :

Many people living in the tropics are at risk of infection from a wide variety of vector-borne diseases, most notably malaria and dengue. Physiological resistance and behavioral responses of mosquito vectors to insecticides are critical issues of the chemical-based disease control equation. The term “excito-repellency” is conventionally referred to as the behavior that is stimulated by direct contact with a chemical that results in abnormal excitation and noncontact repellency that results without the insect making physical contact with the chemical. For decades, information on behavioral properties of chemicals can be regarded as being basic requirements to assist guide chemical use in evidence-based, vector management and control programs. Besides, natural products to protect humans from mosquito bites is a preferred policy and plant-based essential oil product is one alternative to synthetic insect repellents. There are several essential oils from botanical sources which can repel mosquitoes. This presentation provides the information on various behavioral responses to insecticides and botanical repellents in important mosquito vectors using laboratory systems and field assays conducted in Thailand.

[SC20-00060]
Abstract Type :

3. Symposium

Abstract Title :

In need of new surveillance toolbox for knowlesi malaria vectors

Abstract :

Plasmodium knowlesi a simian malaria parasite is the predominant species affecting humans in Malaysia. All countries in Southeast Asia have reported knowlesi malaria except for Timor-Leste. Leucosphyrus group of Anopheles mosquitoes have been incriminated as the vectors. Due to changes in landscape, the long-tailed macaques have been displaced and now thrive in fragmented forest, plantations or farms and villages near forest edge. Most humans are infected when they visit these sites. The vectors are biting in the early part of the night and outdoors. Thus, the use of insecticide treated bed-nets and indoor residual spraying will not be effective in controlling the vectors. Data on the vectors are also scanty and patchy. It has also been established that this public health problem is related to people who live, work or visit forested areas where both the macaques and the vector mosquitoes coexist. It is known that army personnel do get infected and this can be overcome by providing them insecticide treated uniforms. However, new tools are needed for the surveillance and control of malaria vectors to protect others who get infected. There are many challenges and obstacles in the development of a new toolbox, and these will be discussed.

[IC20-00283]
Abstract Type :

3. Symposium

Abstract Title :

Evolution of malaria vectors bionomic and insecticide resistance in urban settings in Central Africa

Abstract :

Introduction : Urban malaria is becoming a serious challenge for malaria control. We report about a series of studies conducted in the cities of Douala and Yaoundé in Cameroun assessing malaria vectors bionomics and insecticide resistance dynamic.

Methods : Anopheline breeding habitats distribution was monitored during monthly investigations. Physicochemical parameters of breeding sites were analyzed and compared between sites. Malaria transmission dynamic was assessed using human landing catches and light traps. The susceptibility level of mosquitoes to various insecticides and xenobiotics was determined using bioassays on larvae and adults. Insecticide resistant mosquitoes were screened to detect the presence of the kdr and ACE-1R alleles using TaqMan assays. A whole genome microarray analysis was conducted to compare gene expression profiles.

Results : Members of the An. gambiae complex (An. gambiae and An. coluzzii ) were the major vectors and most abundant species in Yaoundé and Douala. A seasonal transmission pattern with annual EIR of 0 to 90 infected bites/person/year were recorded. Mosquitoes originating from urban agriculture areas generally appeared highly tolerant to almost all insecticide compounds. Different xenobiotics appeared to select for insecticide resistance. Resistance to DDT and pyrethroids was associated to a high prevalence of kdr alleles and overexpression of several detoxification enzymes such as CYP6M2, CYP6P3, GSTD1-6. Resistance to carbamates and organophosphates was mediated by the ace-1R mutation and P450 genes.

Conclusion : Our data confirm the current adaptation of An. gambiae to urban areas and the diversity of resistance mechanisms. The present study calls for additional strategies in the control of malaria vectors in urban areas.

S28_R8: Centers of Excellence for Malaria Research in Asia
Chairperson: Pradipsinh K Rathod

[IC20-00576]
Abstract Type :

3. Symposium

Abstract Title :

Southeast Asian ICEMR: Addressing the Challenges in Regional Malaria Elimination

Abstract :

Introduction : The Southeast Asian International Center of Excellence in Malaria Research (ICEMR) focuses on the malaria problem in the Greater Mekong Subregion (GMS), aiming to develop an integrative strategy for malaria control and aid the NMCPs in their endeavor toward malaria elimination.

Methods : At selected sentinel sites located along international borders, we closely follow the changes in malaria epidemiology using passive and active case detection. The demographic and epidemiological systems allow us to track the distribution and dynamics of malaria and its relation to both biotic and abiotic factors such as climatic changes, host movements, and vector abundance. Investigations into vector biology provide updated information about relative abundance, seasonal fluctuations, biting behaviors, and insecticide resistance. We closely monitor the treatment efficacy of antimalarial drugs and use genomic tools to identify the molecular mechanisms of drug resistance.

Results : Vivax malaria has become the predominant parasite in the GMS, and multiple risk factors were identified with its transmission in border regions. In western GMS, we also detected deterioration of the efficacy of chloroquine/primaquine for vivax malaria. Asymptomatic malaria represents an important reservoir, requiring more sensitive tools for detection and targeted MDA for elimination. Vector studies revealed changing vector community structure in sentinel sites and emerging problems of pyrethroid resistance. Drug resistance studies identified predominant and changing genotypes of artemisinin resistance in western GMS.

Conclusion : The scientific findings from the ICEMR research activities offer a systematic view of factors sustaining residual malaria transmission and identify potential solutions to these problems to accelerate malaria elimination in the GMS.

[SC20-00158]
Abstract Type :

3. Symposium

Abstract Title :

Applying serological surveillance tools for tracking and advancing elimination of malaria in Cambodia and PNG

Abstract :

The Asia-Pacific ICEMR aims to track and advance elimination of malaria in Cambodia and Papua New Guinea. In both countries, as well are others throughout the Asia-Pacific, malaria infections due to Plasmodium vivax are a major challenge for elimination. ICEMR studies have demonstrated most infections in Cambodia are due to P. vivax, with most also being asymptomatic and undetectable by standard diagnostics such as RDTs and light microscopy. In PNG, the malaria burden is higher with clear spatial heterogeneity in transmission. Both countries thus face challenges with surveillance due to hidden infections and hot-spots of transmission. In these settings, P. vivax serological exposure markers (SEMs) have promise as a novel approach for identifying individuals with recent P. vivax infections. We have designed a panel of 8 P. vivax antigens that induce IgG antibody responses reflective of recent exposure to P. vivax in the prior 9-months. These SEMs can identify individuals at risk of recurrent P. vivax infections. We are assessing use of these SEMs in the ICEMR studies of Cambodia and PNG and will present data showing their utility in these specific settings.

[SC20-00227]
Abstract Type :

3. Symposium

Abstract Title :

Deciphering the pathogenesis of cerebral malaria through multidisciplinary and integrated patient investigations in India

Abstract :

Cerebral malaria (CM) is an acute nontraumatic encephalopathy and the most severe neurological complication of Plasmodium falciparum infection. Mortality is high, long-term neurocognitive deficits are frequent in survivors, and the pathogenetic mechanisms leading to CM are still being debated. However, the recent application of advanced neuroimaging techniques to patients with CM has revolutionised our understanding of the disease. Over the past 8 years, our team has recruited severe and uncomplicated falciparum malaria patients at Ispat General Hospital in Rourkela, India. We combined serial brain magnetic resonance imaging with cutting-edge clinical, laboratory, omics, and in silico investigations to better understand the factors influencing the development and outcome of CM. We are leveraging the generated findings to select and validate new candidate biomarkers for improved diagnosis and prognosis, as well as to inform the design of novel adjunct therapies aimed at increasing patient survival.

[SC20-00154]
Abstract Type :

3. Symposium

Abstract Title :

Malaria Evolution in South Asia (MESA): A US NIH International Center of Excellence for Malaria Research (ICEMR)

Abstract :

Starting in 2010, the US National Institutes of Health (US NIH) established a global network of independent research centres in malaria-endemic settings to provide knowledge, tools, and evidence-based strategies to support researchers working in a variety of settings, especially within governments and healthcare institutions. https://www.niaid.nih.gov/research/icemr-program-overview Today, the Malaria Evolution in South Asia (MESA) program project has field sites across India. The most highly developed site is the MESA ICEMR lab at Goa Medical College and Hospital, in Goa, India. This is a tertiary care centre that sees malaria patients with P. falciparum and P. vivax year round, with disease presentations ranging from uncomplicated malaria to severe malaria, and even malaria deaths. The US NIH-supported MESA ICEMR lab in Goa is within 15 min drive of Goa Medical College and is equipped with state of the science capabilities for patient blood processing, parasite detection and characterization, adaptation of P. falciparum to continuous culture, drug sensitivity tests on parasites freshly collected from malaria patients, and genomic analysis of parasites. Collaboration with the Government of India National Institute of Malaria Research (NIMR) lab in Goa and Mahidol University in Thailand, have allowed the MESA ICEMR lab to participate in vector biology experiments. This includes studies on parasite growth in different mosquito vectors of the region, and the ability to generate sporozoite forms of the parasites in the salivary glands of mosquitoes. These sporozoites are infectious in liver cells in culture, opening new avenues for malaria research in India. The MESA ICEMR has also established strategic partnerships with other government and academic institutions in India. This includes the Regional Medical Research Center (ICMR) in Dibrugarh, Assam, the National Institute of Malaria Research in Delhi, and the Indian Institute of Technology (IIT) in Mumbai. Government of India malaria scientists who work closely with the US NIH MESA ICEMR scientists have had opportunities to interact with malaria researchers throughout the world, every year.

S29_R9: HIV therapeutics and pharmacology
Chairperson: Steve Ward
Co-Chairperson: Tim Cressey

[SC20-00219]
Abstract Type :

3. Symposium

Abstract Title :

Current Antiretroviral Therapies: Challenges Ahead

Abstract :

Current Antiretroviral Therapies: Challenges Ahead Assist Prof. Chureeratana Bowonwatanuwong Internal Medicine Department, Chonburi Hospital, Thailand After the first reported case of HIV/AIDS in 1981, millions of those infected died until the discovery of the highly active antiretroviral therapy (HAART) in 1995.The highly effective ARVs dramatically suppressed viruses to undetectable level and so reduced the burden of HIV clinical illnesses. Miracle breakthroughs overcame the difficulties of high costs of ARTs to promised universal accesss. The study of the year in 2011 (HPTN 052) revealed the concept of treatment as prevention and targeted of “eradication HIV/AIDS in 2030”. The successful research into new ARV molecules such as Tenofovir alafinamide and new class like Integrase transfer inhibitors improved the chance of avoiding adverse events, increased potencies and controlled dosing complexities. The proof of “undetectable equals to nontransmittable” (U=U) in 2018 gave rise to the hope that social acceptance of the disease would prevail. Despite these victories in the battles against HIV/AIDS, fought over four decades, more challenges lie ahead: drugs that will completely eradicate viruses: a less harsh ARV for special populations, like pregnant women, compromised patients, and the elderly; fewer drug-drug interactions with ARV and the most important of all, a final dissolution of the social stigma.

[IC20-S29R9]
Abstract Type :

3. Symposium

Abstract Title :

Quo Vadis long-acting antiretroviral therapeutics

Abstract:

With several recent regulatory approvals of long-acting injectable antiretroviral regimens for treatment and pre-exposure prophylaxis of HIV, the posological benefits are increasingly being realised. The potential for treatment simplification and addressing complications associated with patient non-adherence are clear, but uncertainties regarding the long half-life which may be discordant between different drugs within a regimen remain. Furthermore, additional challenges are associated with the ease of administration, paediatric considerations and infrastructural demands for widespread roll-out. Existing antiretroviral long-acting injectable medicines predominantly harness advances in particle processing technologies to create drug dispersions able to be delivered at high doses via intramuscular or subcutaneous administration. However, several emerging technologies are being investigated preclinically with the potential for future clinical application in HIV and other communicable and non-communicable diseases, and may offer benefits in the context of certain clinical scenarios. Different technologies present different opportunities and challenges for meeting the needs of patients and providers, but orally delivered technologies, implants and transdermal delivery via microarray patches are all under consideration. This presentation will provide a holistic overview of different drug-delivery technologies being investigated for long-acting drug delivery, highlighting key differences between technologies as they relate to the specific needs for wider global implementation for HIV.

[SC20-00207]
Abstract Type :

3. Symposium

Abstract Title :

Transforming oral HIV drug combinations in daily pills to long-acting products through cell-targeted Drug combination nanoparticle Technology

Abstract :

Current 2-to-3 drug-combination in a one-pill-a-day dosage can bring HIV virus to undetectable levels. However, pill stoppage leads to nearly immediate virus rebound and risk of progression to AIDS. We first reported limited HIV drug exposure in HIV host cells in human lymph nodes at levels much lower than plasma or blood. To overcome lymph-drug-insufficiency, University of Washington TLC-ART (Targeted, Long-acting Combinational ART) program has successfully created a novel DcNP platform technology which enable co-assembly of multiple-drugs into a drug-combination-nanoparticles (DcNP). Subcutaneous administration of a single-dose of TLC-ART 101 containing lopinavir, ritonavir and tenofovir in DcNP formulation in primates resulted in higher lymphocyte-to-plasma drug concentrations achieved for all 3 HIV drugs; with extended drug presence over 3-4 weeks. TLC-ART 101 is progressing toward a first-in-human PK study. The DcNP platform enables integration of many current oral HIV drugs with unique but disparate physical-chemical properties, thereby allowing transformation from oral to long-acting injectable dosages. In vivo Stability of DcNP has enabled to enhanced and synchronized co-localization of multiple HIV drugs in cells for achieving maximum pharmacologic actions against HIV infected cells in the body. Other long-acting HIV drug- combinations of global interests are in the work. With support from NIH, Unitaid, public-and-private sources, our TLC-ART team has taken systems approach to develop a drug combination nanoparticulate platform technology targeted to HIV-host and metastatic cancer cells. Translational strategies-including clinical pharmacology and toxicology, pharmacokinetics, developmental and regulatory path necessary in transforming short-acting oral drug combinations into long-acting HIV therapeutics will be presented. Supported in part by Unitaid 2020-39-GLAD; NIH grants AI120176; AI 148055; HL152401; AI149665

[SC20-00204]
Abstract Type :

3. Symposium

Abstract Title :

Dose optimization of antiretroviral drugs in Thai people living with HIV: Can we do better?

Abstract :

Optimal drug exposures are regarded as a crucial element for successful viral suppression. Despite the fact that greater exposures are linked with high effectiveness, they may also result in undesirable toxicity. In contrast, suboptimal drug concentrations may lead to the emergence of drug resistance mutations that limit therapeutic responses and the efficacy of future treatment choices due to the possibility of cross-resistance between drug classes. The pharmacokinetics of antiretroviral (ARV) drugs exhibit high interindividual variability, posing a potential risk of overdosing or underdosing in a patient population which correlates with clinical outcomes (1). Therefore, for dose optimization, determining potential causes of pharmacokinetic variability is essential. Population pharmacokinetics has been an important tool for discovering and quantifying drug exposure variability. With the use of population pharmacokinetic analysis, the relationship between patient characteristics and observed drug exposure or response can be identified and described. The best dosage regimens can be determined by integrating population pharmacokinetic models and simulations to evaluate different dosing strategies. Several previous pharmacokinetic studies in Thai people living with HIV (PLWH) demonstrated a high exposure to antiretroviral (ARV) drugs when standard dosages were administered (2-4), suggesting a potential for dose reduction. There are clear benefits of ARV optimal dosage reduction, including reduced toxicity and costs and increased drug availability in resource-limited settings. Although, the long-term efficacy of dose reduction strategies remains questionable, the potential advantages of dosage reduction optimization should be actively researched. References 1. Fabbiani M, Di Giambenedetto S, Bracciale L, Bacarelli A, Ragazzoni E, Cauda R, et al. Pharmacokinetic variability of antiretroviral drugs and correlation with virological outcome: 2 years of experience in routine clinical practice. J Antimicrob Chemother. 2009;64(1):109-17. 2. Avihingsanon A, van der Lugt J, Kerr SJ, Gorowara M, Chanmano S, Ohata P, et al. A low dose of ritonavir-boosted atazanavir provides adequate pharmacokinetic parameters in HIV-1-infected Thai adults. Clin Pharmacol Ther. 2009;85(4):402-8. 3. Boyd M, Mootsikapun P, Burger D, Chuenyam T, Ubolyam S, Mahanontharit A, et al. Pharmacokinetics of reduced-dose indinavir/ritonavir 400/100 mg twice daily in HIV-1-infected Thai patients. Antivir Ther. 2005;10(2):301-7. 4. Punyawudho B, Thammajaruk N, Ruxrungtham K, Avihingsanon A. Population pharmacokinetics and dose optimisation of ritonavir-boosted atazanavir in Thai HIV-infected patients. Int J Antimicrob Agents. 2017;49(3):327-32.

S30_R10: New developments in human and animal parasites diagnostics
Chairperson: Momar Ndao
Co-Chairperson: Malcolm Jones

[SC20-00079]
Abstract Type :

3. Symposium

Abstract Title :

High Throughput Sequencing in Diagnostic Parasitology

Abstract :

The field of diagnostic parasitology has moved forward at a tremendous pace over the past two decades. Conventional PCR, followed by real-time PCR have become commonplace the field. More recently, advances in high throughput sequencing (HTS) have opened up a number of new approaches and applications which are now being adopted in the diagnostic parasitology laboratories. As the costs and complexity of HTS decreases, these approaches will become more common in routine parasitology diagnostics. HTS metagenomics has been successfully used to detect parasitic infections in both medical and veterinary sample matrices, but with variable sensitivity and specificity. Such metagenomic approaches to the diagnosis of parasites in blood and faecal matrices have been hampered by excess host or other eukaryotic DNA. The most promising results have been achieved in fluids, such as cerebrospinal fluid, where generally little interfering host or other eukaryotic DNA is present. Targeted amplicon HTS has been very successfully employed to amplify and identify individuals within specific genera, and even phyla, of parasites, but a universal HTS approach successful in all sample matrices remains elusive at this time. Some success has been obtained with universal targeted amplicon HTS of blood samples via pre- and intra-PCR reduction of interfering host DNA, but the methodology remains cumbersome. This talk will discuss the current state of the art in HTS diagnostics for parasitic infections, including the successes and challenges thus far.

[SC20-00206]
Abstract Type :

3. Symposium

Abstract Title :

One Health – Examples of applying same diagnostic methods for samples from animals and humans

Abstract :

A high proportion of pathogens are zoonotic, able to infect both humans and other animals, and many diagnostic approaches are applicable to samples regardless of the host species. Applying same methods can bring synergies and improve preparedness to scale up diagnostic capacity. Biological characteristics in sample material and potential for specificity issues may vary by host species. Applying same methods to characterize pathogens across their host range has the potential to support tracing in outbreaks, and to add to our knowledge on relative contributions of different transmission ways. Comparable baseline data are needed for One Health surveillance. This work is supported by funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No 773830 (One Health European Joint Programme).

[SC20-00083]
Abstract Type :

3. Symposium

Abstract Title :

Detection of schistosomes in areas of low prevalence and low parasite burdens

Abstract :

Schistosomiasis remains a major problem for people in many countries in tropical and sub-tropical regions of Africa, the Middle East, South America and the Caribbean and parts of Asia. The traditional means of diagnosis has been through identification of schistosome eggs from human fecal and urine specimens. Detection of eggs through microscopal studies remains an important means for identifying infections, as the eggs of each species are distinctive. Parasite eggs, which must traverse tissues to escape the host, can appear in variable abundance in diagnostic samples, and there remains concerns about the diagnostic sensitivity of the standard tools. The recent WHO Guideline on control and elimination of human schistosomiasis (WHO 2022) assessed the evidence base for deployment of diagnostic tools. The Guidelines recommended continued use of conventional tools for surveillance in areas of high or moderate infection intensity. Importantly, the hope of sensitive and readily deployable diagnostics in areas where infection intensity is low, still presents challenges and there is need for ongoing research into characterizing and validating new antigens, new immunological and molecular tools, for diagnostic purposes in clinical and epidemiological contexts. This presentation will review some of the latest advances in the suite of tools being developed for diagnostics for schistosomiasis. These tools will be considered in the light of detection of infection in regions of low infection intensities.

[SC20-00130]
Abstract Type :

3. Symposium

Abstract Title :

INNOVATIVE TOOLS FOR IDENTIFYING SCHISTOSOMA SPP. AND THEIR INTERMEDIATE HOSTS IN ENDEMIC AREAS IN SENEGAL.

Abstract :

Schistosomiasis is a neglected tropical disease. In Senegal, the disease is endemic in the north of the country with prevalence reaching 80% in many villages. Praziquantel (PZQ) is the main treatment for controlling the disease. However, despite the control strategies, the prevalence is still high. There is a lack of information about the burden of the infection in pre-school aged children, in women, in the intermediate host snails and in livestock. So, there is a need to find innovative diagnostic tools to better guide the control strategies. Repeated prevalence and malacological surveys have been conducted in the north and center of the country over a three-year period. Collected schistosomes (urine and feces) and the snails have been identified using real time PCR and matrix assisted laser desorption ionization-time of flight mass spectrometry time of flight (MALDI TOF MS). The PCR has been used to improve the detection of cases and to describe the distribution of schistosome hybrids species in snails and urine samples while the MALDI-TOF MS has allowed the identification of freshwater snails’ species. The molecular techniques have shown the heterogeneity of snail infestation at the village level. There was discrimination between species of the Schistosoma haematobium group. The analysis of spectra in MALDI TOF MS yielded intra-species reproducibility and inter-species specificity and blind test results revealed 100% of specimens were correctly identified with a log threshold greater than 1.7. These results have shown that MALDI-TOF MS is a reliable tool for the rapid identification of ethanol-stored and frozen specimens without requiring any malacological expertise. Further studies are needed to better characterize the schistosome and the snail populations.

S31_R1: Mutagenesis in populations of Plasmodium falciparum
Chairperson: Pradipsingh K Rathod

[SC20-00041]
Abstract Type :

3. Symposium

Abstract Title :

Selection parameters facilitating in vitro Plasmodium falciparum evolution

Abstract :

In vitro selection of Plasmodium falciparum parasites for resistance to specific new antimalarial agents can provide useful insights into vulnerability of new antimalarial agents to resistance. Such controlled selection experiments, when conducted with newly adapted parasite lines from around the world, can also provide early indications of global sites that harbour parasites with higher propensity to initiate resistance to novel antimalarial agents. Practically, in vitro selection experiments are most successful with antimetabolites that target specific enzymes. The nature of the genetic changes observed after in vitro evolution of resistance can depend on the selection compound, its mode of action, and the nature of the target. The end result of such selection experiments help predict susceptibility of specific new antimalarials to resistance. They help identify parasite populations with potential to mutate at high rates. Finally, for antimetabolites with specific enzyme targets, amplified regions can point to the target of the antimalarial agent used in the selection.

[IC20-00550]
Abstract Type :

3. Symposium

Abstract Title :

Molecular signatures from ARMD Plasmodium falciparum

Abstract :

Introduction : Plasmodium falciparum clones from Southeast Asia display the Accelerated Resistance to Multiple Drugs (ARMD) trait that promotes the rapid evolution of genetic diversity (PNAS 1997; 94(17): 9338-93). Poly A/T-mediated recombination and expansive copy number variation provide an initial foothold to attain drug resistance and parasite survival (PLoS Path 2013; 9(5):e1003375). Under higher selection pressure, parasites sequentially create more amplicons, acquire higher resistance, and potentially generate stable, beneficial point mutations with minimum collateral damage elsewhere.

Methods : The ARMD strategy was initially revealed in the clone W2 from SE Asia, but this clone was isolated over 30 years ago and well-adapted to in vitro culture. We determined whether present global parasites mutate efficiently and use ARMD strategies for evolution. The approach utilized an in vitro selection procedure calibrated with the thymidylate synthase inhibitor, 1843U89. Resistant populations were whole genome sequenced.

Results : When lethal selection was applied to recent Indian, Cambodian, and Ugandan isolates, amplifications and resistance emerged quickly, though it was evident that some lines were better than others at generating copy number variations leading to resistance. A consistent feature among mutants was long repeating 25-40 kb stretches of DNA around the target-coding Pfdhfr-ts locus, and only this locus.

Conclusion : The selection methods employed can resolve varying capacities for resistance acquisition and present global P. falciparum populations use ARMD traits for evolutionary advantages. Supported by US NIAID MESA ICEMR Program Project U19 AI089688

[SC20-00187]
Abstract Type :

3. Symposium

Abstract Title :

Tracking de novo CNV evolution in Plasmodium falciparum using single cell approaches

Abstract :

Changes in the copy number of genomic regions, termed copy number variations (CNVs), are an important adaptive strategy for malaria parasites. CNVs across the Plasmodium falciparum genome contribute directly to drug resistance or parasite fitness. AT-rich sequences in the P. falciparum genome contribute to CNV evolution; however, we do not know whether random spontaneous CNVs arise constantly across the genome or are stimulated when parasites are under stress. Detection of “de novo” CNVs in minor populations of parasites is challenging using traditional sequencing approaches. We developed two single cell approaches to better understand CNV evolution. In a novel single cell genomics pipeline, we isolate single parasites and amplify their genome using a low-bias method prior to sequencing and CNV analysis. In a parallel approach, we conduct Oxford Nanopore sequencing (>200-fold coverage, N50 of ~70kb) of parasite populations, with or without stress treatment, and directly visualize reads that span CNVs from single parasites. We detected a low basal rate of de novo CNVs in laboratory cultured parasites using both methods. However, metabolic or replication stress induced a ~6-fold increase in structural changes across the genome including amplifications, deletions, and other rearrangements. These events were rare, usually represented on a single read, but contained genes that may be important for malaria phenotypes when under selection. Our findings underscore the importance of stress in de novo CNV evolution. In future work, we will apply these single cell approaches to parasites from other malaria sources and species to better understand drivers of genetic heterogeneity.

S32_R2: Stamping out neglected tropical zoonoses – the necessity of a One Health approach
Chairperson: Rebecca J Traub
Co-Chairperson: COL Mathirut Mungthin
S34_R4: Severe malaria: what’s new on pathogenesis?
Chairperson: Alister Craig
Co-Chairperson: Parnpen Viriyavejakul

[SC20-00077]
Abstract Type :

3. Symposium

Abstract Title :

Neutrophils and the pathogenesis of Cerebral Malaria

Abstract :

Background: Low-density neutrophils (LDN) are a poorly understood population of neutrophils that have been shown in different disease processes including infection to be pro-inflammatory and exhibit immunosuppressive actions. LDN have been identified in Plasmodium vivax infection and positively correlated with disease severity. Their presence and function have not been investigated in cerebral malaria (CM) caused by P. falciparum. We hypothesised that LDN are elevated in CM cases and exhibit an increased inflammatory capacity that contributes to the brain blood barrier (BBB) dysfunction, a process associated with CM pathogenesis. Methods: CM patients and controls were recruited from Queen Elizabeth Central Hospital, Blantyre, Malawi. LDNs were separated from NDNs by gradient separation and both sub-sets examined using light microscopy, flow cytometry, reactive oxygen species (ROS) production and RNA-sequencing. Results and Discussion: 123 children were recruited: 68 CM, 55 non-CM comatose, 8 healthy controls (HC). Increased LDN were associated with CM compared to non-CM coma (P=0.003) and HC (P<0.0001). Compared to the NDN, LDN were associated with an expression pattern of activation (low CD62L, high CD66b) and immaturity (low CD16 and CD10). Further, RNA sequencing showed Ki67 and promyelocytes genes were upregulated in LDN. LDN have decreased ex-vivo ROS production compared to NDN. CM is associated with elevated LDN, that represent a highly activated and immature population of neutrophils with increased proliferation capacity that overall indicate a state of emergency granulopoiesis. Further evaluation of LDN in terms of their ability to form neutrophil extracellular traps (NETs) and disrupt barrier function of brain microvascular endothelial cells will be presented.

[SC20-00141]
Abstract Type :

3. Symposium

Abstract Title :

Pipecolic acid: a putative mediator of the coma of cerebral malaria

Abstract :

Coma is a characteristic feature of cerebral malaria (CM), with an unknown etiology. We have identified the neuromodulatory amino acid pipecolic acid (PA) to be abnormally elevated in the plasma of children with CM, in contrast to normal PA levels found in the blood of children with mild Plasmodium falciparum malaria. PA is renally excreted and children with CM had evidence of renal insufficiency which may contribute to higher levels of blood PA. To further explore this observation, we measured PA brain levels in animals with experimental cerebral malaria (ECM), a model which recapitulates a decline of normal neurologic function during P. berghei ANKA infection. Brain levels of PA were inversely correlated to normal neurologic behavior using a coma and behavior score. Animals infected with other rodent Plasmodium species which do not induce neurologic decline, were found to have elevated PA in the blood compared to uninfected controls, however their brain levels of PA were lower than the brain levels found in ECM. Non-ECM species do not induce blood brain barrier disruption as compared to ECM species, and this may be a factor to allow high brain PA levels to develop in ECM. In a pilot study we identified higher levels of PA in cerebral spinal fluid (CSF) from patients with CM compared to non-CM patients. Our data suggest that parasite-derived PA may play a role in the neurologic changes seen in CM and ECM. Ongoing studies to directly determine if PA induces neurologic decline will be presented.

[SC20-00170]
Abstract Type :

3. Symposium

Abstract Title :

Modeling cerebral malaria in 3D in vitro brain vascular models

Abstract :

P. falciparum-infected red blood cells sequestration in the brain microvasculature is considered one of the main pathogenic events leading to vascular dysfunction and cerebral malaria. As rodent cerebral malaria models present modest infected red blood cells sequestration rates, the pathogenic mechanisms of human cerebral malaria remain unknown. Here, we aim to study malaria pathogenesis in a three-dimensional human blood-brain barrier (3D-BBB) in vitro model. Our model is composed of a collagen hydrogel pre-patterned with microfluidic networks that recreate a wide range of flow conditions present in the brain vasculature. One of the main advantages of our system is that it provides step-wise control over biological and mechanical parameters, such as blood flow and the mechanics of the surrounding tissue. We have generated two models composed of either human primary brain microvascular endothelial cells or induced pluripotent stem cell-derived endothelial cells (iPSC-EC) in combination with primary human astrocytes and pericytes. Direct comparison of the models reveals that the iPSC-EC provide improved barrier properties, as shown by increased junctional expression of claudin-5 and ZO-1, and permeability rates of 3.3·10-8 cm/s to Lucifer Yellow (457 Da). We will use this platform to identify host and parasite factors that drive cerebral malaria pathogenesis, and explore the mechanisms underlying this disease complication at multiple scales. We are measuring changes in barrier integrity, endothelial junctional organization or activation of the cells that compose the BBB after incubation with sequestered P. falciparum-infected red blood cells or extracts of parasite toxins. The use of novel 3D-BBB in vitro models could unveil molecular mechanisms of disease and shed light on novel malaria adjunctive therapies to decrease patient mortality.

[SC20-00104]
Abstract Type :

3. Symposium

Abstract Title :

The brain-kidney axis in cerebral malaria: new insights into brain injury in children with severe malaria through analysis of cerebrospinal fluid biomarkers

Abstract :

Introduction. Acute kidney injury (AKI) is a common complication in pediatric severe malaria and a risk factor for neurocognitive impairment in survivors. To evaluate potential pathways of brain injury in children with AKI we measured host response in the cerebrospinal fluid (CSF) of children with cerebral malaria. Methods. We evaluated 30 CSF markers of inflammation, oxidative stress, and brain injury in 168 Ugandan children aged 18 months to 12 years of age hospitalized with cerebral malaria. Eligible children were positive for Plasmodium falciparum with unexplained coma. Acute Kidney Injury (AKI) was defined using the Kidney Disease: Improving Global Outcomes criteria. Results. The mean age of children was 3.8 years (SD, 1.9) and 40.5% were female. On admission, 46.3% of children had AKI. Mortality was 6.0% in-hospital and AKI was associated with 5.03-fold increased odds of mortality (95%CI 1.03, 24.44). At discharge, 42.1% of surviving children had neurologic deficits. AKI was associated with 2.60-fold increased odds of neurologic deficits at discharge (95% CI 1.34, 5.02). Among the CSF analytes measured, 14 were elevated in the context of AKI (p<0.05) with seven significant following adjustments for multiple testing. Children with AKI had increased CSF markers of oxidative stress (superoxide dismutase (SOD) activity, malondialdehyde), inflammation (TNFα), blood-brain-barrier dysfunction (albumin), neuroexcitatory activity (kynurenic acid), axonal injury (tau), and reduced nitric oxide bioavailability (ADMA) after adjusting for multiple testing. Conclusions. In children with cerebral malaria, AKI is associated with blood-brain-barrier dysfunction, and central nervous system oxidative stress, inflammation, and axonal injury.

[IC20-S28R8]
Abstract Type :

3. Symposium

Abstract Title :
The impact of Plasmodium falciparum infection in the brain: new findings from an Indian cohort

Abstract:

Cerebral malaria (CM) is an acute nontraumatic encephalopathy and the most severe neurological complication of Plasmodium falciparum infection. Mortality is high, long-term neurocognitive deficits are frequent in survivors, and the pathogenetic mechanisms leading to CM are still being debated. However, the recent application of advanced neuroimaging techniques to patients with CM has revolutionised our understanding of the disease. Over the past 8 years, our team has recruited severe and uncomplicated falciparum malaria patients at Ispat General Hospital in Rourkela, India. We combined serial brain magnetic resonance imaging with cutting-edge clinical, laboratory, omics and in silico investigations to better understand the factors influencing the development and outcome of CM. In turn, we are leveraging the generated findings to select and validate new candidate biomarkers for improved diagnostic and prognostic, as well as to inform the design of novel adjunct therapies aimed at increasing patient survival.

S35_R5: Advances in pre-erythrocytic malaria biology and vaccines
Chairperson: Noah Sather

[SC20-00176]
Abstract Type :

3. Symposium

Abstract Title :

Targeting P. vivax relapses with vaccine-elicited humoral immunity

Abstract :

Plasmodium vivax is a geographically widespread parasite that causes malaria disease, which is characterized by relapsing infections well after the primary infection has been cleared. P. vivax malaria relapse can occur months to years after primary infection and is thought to be responsible for the majority of transmission events, causing an estimated 70-90% of onward transmission. Relapse is caused by reactivation of the dormant hypnozoite form in the liver, which reactivates to cause fulminant infection. It has been hypothesized that reducing relapse infections would have a significant impact on transmission, and could potentially be achieved by reducing the hypnozoite burden in the liver. We evaluated this concept experimentally in liver humanized FRG HuHep mice infected with Thai field isolates of P. vivax, where mice were infused with sub-optimal doses of anti-Circumsporozoite protein (CSP) neutralizing antibody 24 hours prior to infection. We found that even an ineffective dose of antibody that did not prevent infection entirely significantly reduced the number of hypnozoites observed in the liver. When evaluated in a model for assessing relapses, antibody treated mice experienced ~65% fewer relapses than mock-treated mice, indicating that reducing the hypnozoite burden also reduced the incidence of relapse infections. Building on these findings, we investigated monoclonal antibodies to PvCSP to determine what epitopes were most efficient at preventing infection, and to determine whether a potent site of vulnerability identified on P. falciparum CSP also existed in PvCSP. We found that antibodies to the repeat and C-terminal regions were effective in reducing infection. Importantly, we identified a neutralizing antibody whose epitope spans the N-terminal and proximal repeat regions, similar to what has been described for PfCSP, indicating that the junctional boundary neutralizing epitope may also be a potent site of vulnerability in P. vivax CSP. Together, these findings indicate that preventing relapse infection, even in the absence of sterilizing immunity, could have a significant impact on P. vivax transmission, and provides leads for the development of next generation PvCSP vaccine candidates.

[IC20-00568] [SC20-00226]
Abstract Type :

3. Symposium

Abstract Title :

Molecular mechanisms of malaria parasite transmission from mosquitoes to mammals.

Abstract :

The WHO announced that it recommends the widespread usage of RTS,S malaria vaccine among children in the endemic regions in 2021. RTS,S prevents mosquito-to-human transmission by targeting sporozoites, the infective stage of malaria parasites accumulated in the salivary glands of mosquitoes. This is a great first step, however its 30% efficacy in reducing severe malaria needs to be further improved for malaria eradication. Sporozoites inoculated in the skin by mosquito bites migrate towards the liver via the bloodstream to infect hepatocytes. To elucidate the mechanisms of the efficient infection, we investigated the roles of sporozoite-specific secretory proteins by reverse-genetics using rodent malaria parasites. Identification of sporozoite-specific proteins essential for cell traversal 2 (SPECT2) revealed that sporozoites traverse cells by wounding their membrane for migration in the skin and for crossing the sinusoidal cell layer. Expanding on this finding, we recently proposed that sporozoites migrating in the skin could be ideal targets for inhibitory antibodies with a SPECT2-dependent cytotoxic mechanism. Next, to investigate the mechanisms of how sporozoites efficiently infect hepatocytes, we focused on secretory proteins commonly expressed in infectious forms: sporozoites and merozoites. By developing a sporozoite-stage specific gene silencing system, we demonstrated that some rhoptry proteins, namely apical sushi protein (ASP), rhoptry neck protein 2 (RON2), RON4, and RON11, are involved in sporozoite invasion of both mosquito salivary glands and mammalian hepatocytes through mediating attachment ability and motility. RON3 in sporozoites, however, was shown to be specifically required for hepatocyte infection. We also investigate the mechanisms of parasite fertilization in mosquito midguts. By screening sexual stage-specific surface proteins, we identified a microgamete surface protein (MiGS) that is required for flagella release. We demonstrated that anti-MiGS antibodies efficiently inhibit parasite transmission in mosquito vectors. Identification and functional analyses of parasite secretory or surface proteins have revealed part of the mechanisms how parasites transmit from mosquitoes to mammals. Further investigation of host-parasite interactions would elucidate the comprehensive mechanisms of parasite infection and propose logical strategies to control malaria transmission.

S36_R6: Ivermectin for malaria: characterizing pharmacokinetics, metabolites and impacts on malaria
Chairperson: Kesinee Chotivanich
Co-Chairperson: Joel Tarning

[SC20-00095]
Abstract Type :

3. Symposium

Abstract Title :

Ivermectin and its metabolites

Abstract :

IVM metabolites were identified in this work using an ultra-high performance liquid chromatography (UHPLC)-coupled quadrupole time-of-flight (Q-ToF) mass spectrometer. Potentially important IVM metabolites were evaluated using in vitro techniques (human liver microsomes) and verified using in vivo clinical samples from healthy volunteers. IVM (10 µM) was incubated with human liver microsomes. After one hour of incubation, metabolite fractions were collected, and the reaction was stopped by adding ice-cold acetonitrile. Controls included zero-time incubation, incubation without a cofactor (NADPH), and incubation without a substrate (IVM). After giving IVM (400 g/kg) to volunteers, whole blood was drawn for the in vivo investigation. Mass spectrometry analysis identified more than 10 potentially important metabolites in in-vitro samples. IVM metabolites were primarily oxidation, di-oxidation, and demethylation products. Two of them were abundant in the blood of volunteers who had ingested IVM. To our knowledge, this is the first detailed description of IVM metabolites in human. Further evaluation of these potentially important metabolites and their mosquito lethal effects is ongoing.

[IC20-00384]
Abstract Type :

3. Symposium

Abstract Title :

Ivermectin metabolites and their impact on mosquito survival
Abstract :

Abstract :

Introduction : Ivermectin has mosquito-lethal properties and treatment of human or livestock populations could provide novel opportunities for vector control. Previously it was demonstrated that the blood of ivermectin-treated volunteers was more lethal to Anopheles dirus and Anopheles minimus compared to blood spiked with ivermectin, suggesting that there are also metabolites of ivermectin with mosquito-lethal properties. Ivermectin metabolites produced in humans were previously characterized from human liver microsomes, hepatocytes, and treated volunteers, and the three most abundant metabolites were identified including: M1) 3”-O-demethylation ivermectin, M3) 4-OHMe ivermectin, M6) 3”-O-demethylation plus 4-OHMe ivermectin.

Methods : Ivermectin structures were purchased commercially including parent compound, aglycone, and monosaccharide. M3 was produced synthetically. In collaboration with Hypha Discovery, M1 was produced by feeding parent compound to a bacterial culture system, and M6 was produced by feeding M3 to the same bacterial culture system. Anopheles dirus and An. minimus mosquitoes were fed blood with various concentrations of parent compound, aglycone, monosaccharide, M1, M3, and M6, and mosquito-lethal effect was observed.

Results : Mosquito mortality analyses are ongoing. Aglycone and monosaccharide have substantially reduced mosquito-lethal effect which is likely due to a lack of the first and second sugar rings which are purported to bind to the Anopheles glutamate-gated chloride ion channel and are critical for opening the channel and driving mosquito-lethal effect.

Conclusion : Various ivermectin structures cause differential mosquito-lethal effect. This work could be used to inform the development of novel ivermectin formulations in different vertebrate hosts or novel ivermectin-like drug candidates for use in malaria elimination campaigns.

[SC20-00115]
Abstract Type :

3. Symposium

Abstract Title :

Pharmacokinetics and mosquito-lethal properties of ivermectin and its metabolites

Abstract :

BACKGROUND: Ivermectin is an antiparasitic drug, but it also has mosquito-lethal properties. This would be useful for mass drug administration with the aim to eradicate malaria. To optimise such treatments, it is crucial to understand the pharmacokinetic/pharmacodynamic properties of ivermectin and its metabolites. The objective of this study was to develop a pharmacokinetic/pharmacodynamic model to quantify the relationship between the concentration of ivermectin and its metabolites and mosquito mortality. METHODS: The model was constructed using dense data from two healthy volunteer trials (n=26). Drug concentrations of ivermectin and three newly identified metabolites were quantified using LC-MS/MS. In addition, blood from volunteers were fed to mosquitos, and mosquito mortality was measured. All the collected data were evaluated using nonlinear mixed-effects modelling in NONMEM. RESULTS: The pharmacokinetic properties of ivermectin and its metabolites were described by the developed population model. Body weight was included using an allometric function on all clearance and volume parameters. Co-administration with the antimalarial drug dihydroartemisinin-piperaquine was shown to increase the absorption of ivermectin. Mosquito mortality was modelled with an EMAX-model with an estimated baseline mortality and with the sum of the molar concentrations of ivermectin and the metabolites driving the effect. An. minimus was substantially more sensitive compared to An. dirus. CONCLUSION: A pharmacokinetic/pharmacodynamic model of ivermectin and its metabolites was developed successfully, and this model was used to simulate several different dosing scenarios for ivermectin treatment and for mass drug administration. This work could be used to inform the design of future clinical trials and malaria elimination campaigns.

[SC20-00196]
Abstract Type :

3. Symposium

Abstract Title :

In vitro evaluation of ivermectin and ivermectin metabolites on asexual blood stage of Plasmodium falciparum

Abstract :

Introduction Ivermectin is widely used to treat helminthic diseases. It is endectocide and has strong mosquito-killing activity. As a result, it has recently been proposed to be used in mass drug administration campaigns to reduce malaria transmission. There are no reports on the effect of ivermectin metabolites on the asexual blood stage of Plasmodium falciparum. The primary aim of this work was to investigate the effects of ivermectin and its metabolites on the asexual blood stage of P. falciparum clinical isolates. Methods The susceptibility of artemisinin-sensitive and artemisinin-resistant P. falciparum isolates to ivermectin and its common metabolites were evaluated using the SYBR green-based 72-hour in vitro susceptibility assay. Data were evaluated by a sigmoidal dose-response analysis, and the concentration associated with 50% of maximum inhibitory effect (IC50) was estimated. Results The mean (SD) of IC50 of ivermectin was 0.81 (0.15) uM and 0.81 (0.13) uM against artemisinin-sensitive (N=2) and artemisinin-resistant (N=3) isolates, respectively. There was no significant difference in IC50 of ivermectin on artemisinin-sensitive and artemisinin-resistant isolates (p=0.574). None of the evaluated ivermectin metabolites showed an increased potency compared to the ivermectin parent compound. Conclusion Ivermectin and its metabolites showed antimalarial activity in the asexual blood stage of P. falciparum at high concentrations, which are not the clinically relevant concentrations achieved with standard therapy. The effect of ivermectin and its metabolites in combination with antimalarial drugs need further evaluation to fully understand its potential in antimalarial therapy.

S37_R7: Angiostrongyliasis
Chairperson: Vernon Ansdell
Co-Chairperson: Paron Dekumyoy

[SC20-00015]
Abstract Type :

3. Symposium

Abstract Title :

Diagnosis and Treatment of Neuroangiostrongyliasis: Evidence-based Clinical Practice Guidelines

Abstract :

Neuroangiostrongyliasis (NAS) or rat lungworm disease is an important emerging infection caused by a nematode parasite, Angiostrongylus cantonensis. It is the leading infectious cause of eosinophilic meningitis worldwide. The disease has spread rapidly from endemic regions in Southeast Asia and the Pacific basin to the Caribbean, South America, Australia, the southern United States, and several countries in Africa. Infection in some parts of the world e.g., Hawaii and Australia appears to be associated with more severe disease, long term disability and increased mortality. Multiple factors are probably involved. Increasing numbers of severe cases in Hawaii prompted the development of guidelines for diagnosis and treatment. A presumptive diagnosis of NAS is made by finding evidence of an eosinophilic meningitis in a patient with a history of suggestive symptoms who is living in or has traveled to an endemic region. The diagnosis can be confirmed by finding larvae in the CSF or the eye, but this is rare. In the USA and a few other countries, diagnosis can also be confirmed by RT-PCR testing for A. cantonensis DNA in the CSF. Treatment is recommended with a combination of high dose corticosteroids and an effective anthelminthic such as albendazole. Animal studies suggest that treatment with albendazole is most effective when started within 7-14 days of infection, but it requires a high level of clinical suspicion to make a presumptive diagnosis at such an early stage of the illness. Increasing clinical experience suggests that early treatment with corticosteroids and albendazole is safe and effective, but further work needs to be done for confirmation.

[SC20-00090]
Abstract Type :

3. Symposium

Abstract Title :

Stat3/IL-6 signaling mediates sustained pneumonia induced by Agiostrongylus cantonensis

Abstract :

Angiostrongylus cantonensis (AC) is well-documented that parasitizes the host brain and causes eosinophilic meningitis. The migration route of AC in permissive hosts is well demonstrated, while in nonpermissive hosts, it remains to be fully defined. In the present study, we exploited live imaging technology, morphological and pathological configuration analysis, and molecular biological technologies to explore the migration route of AC and the accompanying tissue damage in nonpermissive and permissive hosts. Our data indicated that, in nonpermissive host mouse, AC larvae migrated from intestinal wall to liver at 2 hours post-infection (hpi), from liver to lung at 4 hpi and then from lung to brain at 8 hpi. AC larval migration caused fatal lung injury (pneumonia) during acute and early infection phases, along with significant activation of Stat3/IL-6 signaling. In addition, AC induce sustained interstitial pneumonia in mouse and rat and pulmonary fibrosis only in rat during late infection phase. Moreover, during the early and late infection phases, Th2 cytokine expression and Stat3 and IL-6 signaling were persistently enhanced and myeloid macrophage cells were notably enriched in host lung, and administration of Stat3 and IL-6 inhibitors (C188-9 and LMT-28) attenuated AC infection-induced acute pneumonia in mice. Overall, we are the first to provide direct and systemic laboratory evidence of AC migration route in a nonpermissive host and report that infection with a high dose of AC larvae could result in acute and fatal pneumonia through Stat3/IL-6 signaling in mice. These findings may present a feasible to rational strategy to minimize the pathogenesis induced by AC.

[SC20-00011]
Abstract Type :

3. Symposium

Abstract Title :

Immunochromatographic device, a Point-of-Care test to detect antibodies for rapid diagnosis of human angiostrongyliasis

Abstract :

Introduction : Angiostrongyliasis caused by Angiostrongylus cantonensis is a central nervous system disease. The disease can produce eosinophilic meningitis or meningoencephalitis in humans. A definitive diagnosis is confirmed by discovery of the worms in cerebrospinal fluid after lumbar puncture or in the eyes during surgery. Serological tools i.e. the ELISA and immunoblotting, are most commonly used for supportive diagnosis of human angiostrongyliasis. However, these immunological tests are laborious to examine and none are commercially available. Methods : To conquer, we have developed the immunochromatographic test (ICT) kit for rapid diagnosis of human angiostrongyliasis through the detection of anti-A. cantonensis-specific antibodies serum samples. A recombinant A. cantonensis galectin-2 (rAcGal2) from young adult female worms was used as an antigen for the ICT kit development. Diagnostic values were evaluated and compared using the ELISA. Results : The sensitivity, specificity, and positive and negative predictive values, of the ICT kit were 87.0%, 96.5%, 94.6%, and 91.4%, respectively, and those of the ELISA were 91.0%, 97.2%, 95.8%, and 94.0%, respectively. The concordance of the ICT kit was 93.9%. Discussion : We, thus, determined that the ICT kit is highly sensitive and specific and provides reliable diagnostic results. It is rapid and simple to perform and can be utilized for both point-of-care diagnoses in the bedside laboratory and epidemiological surveys in endemic regions where access to diagnostic equipment is limited. References : Am J Trop Med Hyg. 2019 Oct;101(4):851-858. doi: 10.4269/ajtmh.19-0208. Parasitology. 2019 Nov 6:1-5. doi:10.1017/S0031182019001495

[SC20-00102]
Abstract Type :

3. Symposium

Abstract Title :

Application of Multiplex Bead Assay (MBA) technology to the serological surveillance of helminthosis

Abstract :

Despite current technological advances, the diagnosis and serological surveillance of helminthiases remains an unsolved challenge. This is mainly due to: (i) the absence of individual species-specific analites for most helminthosis, which is being addressed by the selection of recombinant antigens and (ii) the lack of multiplexing systems on the market that allow the diagnosis and/or serological surveillance of multiple helminthosis simultaneously. For this purpose, we are working with multiplex bead-based fluorescent assays (MBA). Coupling of recombinant proteins to the surface of the magnetic beads and MagPlex immunoassays are carried out by combination of standard methodologies. The results obtained after analysing the fluorescence intensity values of all types of beads coupled with different recombinant antigens such as T24H, 2B2t, Ov16, Wb123, LSXP1, etc., using the Luminex 200 platform, are compared with gold standard techniques or commercially available methods depending on the application. The MBA technology shows effective applications for both combined surveillance of already established control programs of neglected tropical helminthosis (Onchocerciasis-lymphatic filariasis), as well as, mapping the endemic areas for those helminthosis presented as hot-spots where control programs should be applied, as teniosis / cysticercosis. Although, still under development, its application for the combined serological diagnosis of eosinophilic meningitis (Angiostrongylus cantonensis & Gnathostoma spinigerum) could be clinical utility.

S38_R8: Post-registration studies in antimalarial drug development
Chairperson: Stephan Duparc

[SC20-00053]
Abstract Type :

3. Symposium

Abstract Title :

The CANTAM study: evaluation in real life of the safety, tolerability and effectiveness of pyronaridine-artesunate in Central Africa and Côte d’Ivoire

Abstract :

This large clinical Phase IIIb/IV study has evaluated the hepatic safety, tolerability and effectiveness of pyronaridine-artesunate (Pyramax™) in a real-life setting including hitherto under-represented patient populations. The study was conducted in Cameroon, the Democratic Republic of Congo, Gabon, Ivory Coast and the Republic of Congo. Patients above 5kg bodyweight presenting with acute uncomplicated malaria at local health facilities were included. The primary objective was to evaluate any hepatic safety events in a subgroup of patients enrolled with asymptomatic transaminases >2xULN at baseline. Pyronaridine-artesunate was given according to the label information as a once daily dose for 3 days, the first dose under supervision. Participants were seen again on D7 and D28 at home by a community health worker. Further liver function testing was performed if there were any hepatic signs or symptoms. Between June 2017 and March 2019, 8560 uncomplicated malaria episodes, including 158 with elevated baseline liver enzymes and 134 in children <1 year of age, were treated with at least one dose of pyronaridine-artesunate. No episode of clinically apparent drug induced liver injury was detected. Nine mostly mild (0.1%) hypersensitivity reactions occurred. Serious adverse events occurred in 29 participants (0.4%) in the course of this study of which four events were judged as related to pyronaridine-artesunate. PCR corrected cure rate on D28 was 98.6% in the per-protocol population. Pyronaridine-artesunate showed a very good safety and effectiveness profile for the treatment of uncomplicated malaria in Africa in this unselected patient population.

[SC20-00092]
Abstract Type :

3. Symposium

Abstract Title :

Importance of the Community Health Workers for the management of malaria at the community level

Abstract :

Community Health Workers (CHWs) are an important backbone of global health interventions. Frequently, they are volunteers trained on specific health care interventions and can work on a broad range of health issues. In regions where access to nurses or doctors is limited or nonexistent, especially in remote areas, they can help reduce morbidity and mortality. This presentation will be focusing on the role of these CHWs in three post-marketing programmes: • CANTAM, a completed phase IV Cohort Event Monitoring study conducted in Cameroon, Democratic Republic of Congo (DRC), Republic of Congo, Gabon and Côte d’Ivoire with Tübingen University. In this study, CHWs were in charge of the safety and effectiveness assessment in real-life conditions of a population of malaria patients treated with the artemisinin-based combination therapy (ACT), Pyramax® (pyronaridine-artesunate). • An ongoing pregnancy registry conducted in Kenya and Burkina Faso with the Liverpool School of Tropical Medicine, the Kenya Medical Research Institute and the Clinical Research Unit of Nanoro. The aim of this registry is to gather data on the safety of ACTs in first trimester pregnant women. • The CARAMAL project, conducted in Nigeria, DRC and Uganda with the Swiss Tropical and Public Health Institute, in which patients suspected of severe malaria were managed by CHWs with rectal artesunate before being referred to a health center for final treatment with injectable artesunate followed by 3 days of an ACT. These three examples illustrate the importance of involving CHWs in global health interventions for the benefit of populations living in low-resource settings.

[SC20-00049]
Abstract Type :

3. Symposium

Abstract Title :

INSPECTOR insights: Tafenoquine and dihyroartemisinin-piperaquine for Plasmodium vivax radical cure in Indonesian Papua

Abstract :

BACKGROUND: Treating Plasmodium vivax malaria involves combining a blood schizontocidal agent (cure of the acute attack) with a hypnozoitocidal agent (cure of hepatic latency). This combination is widely referred to as radical cure. Tafenoquine is a newer hypnozoitocidal 8-aminoquinoline administered as a single 300 mg dose in combination with standard blood schizontocidal chloroquine therapy for radical cure. The standard-of-care radical cure (since 1952) has been primaquine, another 8-aminoquinoline administered as 0.25 or 0.5mg/kg per day for 14 days also administered with chloroquine or ACT blood schizontocidal therapy. METHODS: We engaged a study population of G6PD-normal Indonesian soldiers experiencing microscopy-confirmed P. vivax malaria on their malaria transmission-free bases in East Java (Malang and Madiun) within 5-mo of completing 9-mo tours of duty in malarious Papua, Indonesia. This was a randomized, double-blinded, double-dummy, placebo-controlled trial (NCT02802501) involving three treatment arms: 1) single-dose tafenoquine plus primaquine placebo (n=50); 2) primaquine (0.25mg/kg daily for 14d) plus tafenoquine placebo (n=50); and 3) tafenoquine placebo plus primaquine placebo (n=50). All treatment arms included co-administered standard dihydroartemisinin-piperaquine (DP) blood schizontocidal therapy. RESULTS: As already reported, both regimens proved safe, but neither tafenoquine nor primaquine achieved satisfactory efficacy relative to DP alone; 21%, 52%, and 11%, respectively. Heterogeneity of cytochrome P-450 2D6 genotypes did not appear to be involved in these outcomes. In the case of primaquine, several other trials proved that a higher dose regimen of primaquine (0.5mg/kg for 14 days) combined with DP provided clinically meaningful efficacy (>90%). CONCLUSIONS: In this trial where tafenoquine was combined with DP for the first time, we strive to understand the basis of its reduced efficacy against relapse when clinically meaningful efficacy is observed when combined with chloroquine. We review ongoing follow-up studies in vitro consistent with sub-optimal efficacy of tafenoquine when combined with DP. This work demonstrates the importance of a key therapeutic principle of 8-aminoquinolines for radical cure of vivax malaria: the partner blood schizontocide may either improve or degrade both therapeutic efficacy and toxicity of the 8-aminoquinoline applied. The safety and efficacy of any radical cure therapies involving 8-aminoquinolines must be demonstrated before recommended. Disclosure: NCT02802501 was funded by GSK (study sponsor) and MMV; listed affiliations contemporary to trial execution

[SC20-00193]
Abstract Type :

3. Symposium

Abstract Title :

From clinical studies to operational feasibility: Use of point-of-care testing for G6PD deficiency to support P.vivax case management with 8-aminoquinolines.

Abstract :

Introduction Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency is a common enzymopathological disease. Individuals with G6PD deficiency are susceptible to hemolysis during oxidative stress. Safe access to several medications including 8-aminoquinolines for treatment of P.vivax may be limited in populations with high G6PD deficiency prevalence in absence of screening for G6PD deficiency . Methods This study presents the clinical performance data for the STANDARD™ G6PD test (SD Biosensor, South Korea) from clinical studies performed in the Bangladesh, Brazil, Ethiopia, India, the UK, and the US. The study also presents early lessons learnt from operational research studies conducted in Laos and Vietnam. Results Across close to 4000 specimens collected worldwide using universal thresholds, the sensitivity on fingerstick specimens for G6PD deficiency (activity level ≤ 30%) was 100% (95% C.I.97.5–100.0) with a specificity of 98.1 (95% C.I 97.6–98.5). The sensitivity for females with intermediate activity (30-70% G6PD activity) was 77% 77.0 (95% C.I 66.8–85.4) although most false normal cases had an activity of greater than 60% G6PD activity. The performance was improved in venous specimens and 100% sensitivity for both deficient and intermediate cases across close to 400 P.vivax infected individuals. Operational feasibility for introducing the G6PD test into clinics managing P.vivax malaria was demonstrated with important lessons on training requirements specially in clinics with low disease burden. Conclusion Point-of-care testing for G6PD deficiency can expand access to critical medicines including primaquine and tafenoquine to populations where these were otherwise inaccessible due to safety concerns.

S39_R9: Virus-host interaction: what do we learn and what can we do?
Chairperson: Panisadee Avirutnan
Co-Chairperson: Bunpote Siridechadilok
Symposium Day 4 27 October 20
S41_R1: Novel tools for vector control
Chairperson: Nicole L Achee
Co-Chairperson: Alongkot Ponlawat

[IC20-00314]
Abstract Type :

3. Symposium

Abstract Title :
WHO perspective on the evaluation of novel vector control interventions
Abstract :

Introduction : The WHO vector control evaluation process comprises two complementary pathways. The new intervention pathway focuses on the systematic evaluation of epidemiological impact (referred to as public health value), while the prequalification pathway assesses safety, quality and entomological efficacy.

Methods : The goal of the process is to inform the use of scarce resources by WHO member states in the fight against vector borne diseases. This is done by means of formulating a WHO recommendation for an intervention class that has demonstrated public health value and publishing associated prequalification listings for product that fall into this class. Novel interventions that do not fall into an established class have to pass through both the new intervention pathway and the prequalification pathway.

Results : This presentation will provide an overview of the intervention classes for which first-in-class products are under active WHO evaluation, supported by the Vector Control Advisory Group, and those classes for which public health value has recently been demonstrated.

Conclusion : A summary of the key updates to the norms, standards and processes underpinning the development of WHO recommendations for vector control interventions will be provided, and how these updates affect the requirements for assessing an interventions epidemiological impact. Finally, the issue of integrated vector control will be discussed, and why this approach, although advocated by WHO under the Global Vector Control Response, can pose challenges to the evaluation of public health value.

[IC20-00294]
Abstract Type :

3. Symposium

Abstract Title :
RNAi technology for Aedes-borne virus vector control

Abstract :

Introduction : Eco-friendly innovations in mosquito control are vitally needed to address established and emerging mosquito-borne illnesses. Our research program aims to develop and characterize RNA interference (RNAi) technologies for mosquito control.

Methods : High-throughput screens in Aedes aegypti identified hundreds of RNAi-based pesticides, a subset of which have target sites that are conserved in multiple species of mosquitoes, but which are not found in non-target organisms, and which kill both developing and adult mosquitoes. Saccharomyces cerevisiae (baker’s yeast) was engineered as an inexpensive interfering RNA propagation system that facilitates oral delivery of RNAi insecticides to mosquitoes.

Results : We have developed and characterized multiple strains of yeast interfering RNA pesticides that induce high levels of mortality in Aedes, Culex, and Anopheles species of mosquito larvae, but that are not found to be toxic to select non-target arthropods. Recent studies have demonstrated that these inactivated yeast pesticides can also be delivered to adult insects as the active ingredient of attractive targeted sugar baits (ATSBs), which induce high rates of morbidity in adult mosquitoes. Recent progress in our efforts to scale yeast production, dry and formulate larvicidal and adulticidal interfering RNA pesticides, evaluate the efficacy of this intervention in the field, and assess stakeholder acceptance of this mosquito control intervention will be discussed.

Conclusion : These studies are advancing us toward the goal of introducing RNAi-based mosquito control technologies into integrated mosquito control programs worldwide.

S42_R2: Discovery of blood stage and transmission blocking vaccine candidates
Chairperson: Takafumi Tsuboi
Co-Chairperson: Rhea Longley

[SC20-00067]
Abstract Type :

3. Symposium

Abstract Title :

Asexual blood-stage falciparum malaria vaccine candidate discovery with wheat-germ cell-free system

Abstract :

Asexual blood-stage falciparum malaria vaccine candidate discovery with wheat-germ cell-free system Wheat-germ cell-free system (WGCFS) is one of the options for expressing eukaryotic proteins in vitro. The system was established at Ehime University about 20 years ago and used to express proteins of humans, rodents, parasites, and plants. Over the last ten years, we have demonstrated that WGCFS can efficiently synthesize recombinant malaria proteins in functional form. The proteins can induce biologically relevant antibodies, such as P. falciparum growth inhibitory and transmission-blocking activities. We have recently scaled up the WGCFS as a “Malaria protein factory”, generating >3000 proteins and raising >500 animal anti-plasmodial antibodies. Based on these original bioresources, we have two approaches to identifying novel blood-stage vaccine candidates, i.e., immunoscreening and reverse vaccinology. In this talk, the findings from the two approaches will be presented, including PfRipr5, a promising blood-stage vaccine candidate based on PfRipr.

[SC20-00019]
Abstract Type :

3. Symposium

Abstract Title :

Approaches for discovery and validation of asexual blood-stage P. vivax vaccine candidates

Abstract :

Malaria infections due to Plasmodium vivax are a major challenge for elimination. Novel tools for prevention that specifically target P. vivax are required. There is currently no advanced vaccine for P. vivax and only a limited number of potential candidates in the pipeline. In malaria-endemic areas, protective immunity against clinical disease is acquired with increasing exposure and age. Naturally acquired immunity is reliant on the generation of Plasmodium-specific antibodies, which perform various effector functions such as inhibition of invasion of red blood cells, neutralisation, opsonisation, and antibody-dependent cellular inhibition. Thus, longitudinal studies in malaria-endemic areas can be utilised to identify both specific targets (P. vivax proteins) and mechanisms (functional antibodies) of protection from clinical disease. In a longitudinal cohort study of 1-3 year old children from Papua New Guinea, we assessed antibody responses against 342 P. vivax proteins using a high-throughput AlphaScreen platform. We subsequently developed a novel multiplexed assay that can identify the targets of functional antibodies against P. vivax that interact with complement and Fcy-receptor. We were able to confirm previous results from our laboratory identifying the proteins reticulocyte binding protein 2b and StAR-related lipid transfer protein, as well as identification of novel targets and functions with similar levels of predicted protective efficacy. A logical pipeline can be applied to i) first identify potential P. vivax vaccine candidates and then ii) identify and validate their functional mechanisms of protection. Our findings identify promising antigens for prioritisation to advance P. vivax vaccine development.

[SC20-00184]
Abstract Type :

3. Symposium

Abstract Title :

CoPoP: a novel and universal delivery platform for malaria vaccine

Abstract :

A vaccine targeting multiple stages of the Plasmodium falciparum parasite life cycle offers advantages for controlling malaria but has been difficult to realize. The Circumsporozoite protein (CSP) is the antigenic target of leading P. falciparum pre-erythrocytic mosquirix® vaccines that prevent infection in human hosts. Pfs230, a sexual-stage P. falciparum surface protein, is currently in clinical trials for malaria transmission-blocking vaccines, which inhibit parasite development within the mosquito vector. In this study, recombinant full length CSP and a Pfs230 fragment (Pfs230D1+) are co-displayed on immunogenic liposomes with the goal of inducing immunity that reduces both infection and transmission. Here, we have shown that rapid conversion of recombinant antigens (CSP and Pfs230D1+) into particulate form via admixing with liposomes containing cobalt‐porphyrin‐phospholipid (CoPoP) potently enhances the functional antibody response. Antigens binding via His‐tag insertion into the CoPoP bilayer results in a serum‐stable and conformationally intact display of the bivalent antigens on the liposome surface. The bivalent liposomes induced antibodies in inbred and outbred mice that recognized both sporozoites and gametocytes and had greater antibody magnitude compared to admixture of the antigens with other adjuvants. The induced antibodies reduced parasite development in mosquito midguts in a standard membrane feeding assay. Mice immunized with bivalent liposomes, or receiving purified antibodies from immunized rabbits via passive transfer, had reduced parasite liver burden following challenge with transgenic sporozoites expressing P. falciparum CSP. Taken together, these data support that next-generation particle-based immunogen approaches, such as the use of CoPoP liposomes, could be useful for a developing a multi-stage next-generation malaria vaccine.

[SC20-00065]
Abstract Type :

3. Symposium

Abstract Title :

Novel malaria transmission-blocking vaccine candidates

Abstract :

Introduction Development of a malaria transmission-blocking vaccine (TBV) could make a major contribution towards malaria elimination, however, only a few TBV antigens have reached pre-clinical or clinical development. Methods Using a qualified Standard Membrane-Feeding Assay (SMFA), we have evaluated biological activities of vaccine-induced antibodies in animals and humans. The TBV potential of more than 20 novel Plasmodium falciparum antigens, which were identified by reverse vaccinology approaches or from rodent malaria models, were assessed. In addition, we have been seeking the minimum functional domains or epitopes within known TBV antigens (i.e., Pfs25, Pfs230 and Pfs48/45) to improve the quality of induced antibodies. Furthermore, beyond the antigen itself, multiple delivery platforms, conjugations, and adjuvant systems, have also been investigated to enhance the immunogenicity and/or durability of TBVs. Results While many novel TBV candidates have been tested, only a few, such as PfHAP2 and Pfs47, can induce transmission-reducing antibodies as potent as known candidates judged by SMFA. On the other hand, significant progress has been made for key domain/epitope identifications in the known antigens. In addition, multiple novel vaccine delivery systems, which are considered to be clinically applicable, have shown promising results. In the symposium, not only our results, recent progress in the TBV field and challenges for novel TBV antigen discovery will be discussed. Conclusion The efforts to identify novel TBV candidates need to be continued, and once a promising candidate (including vaccine delivery systems) is discovered, it should be assessed in humans as quickly as possible as long as there are no safety concerns.

S43_R3: Panel discussion: Implementation of COVID-19 vaccination: Thailand experiences
Moderator: TBA
S44_R4: Diagnosis of helminthic infections
Chairperson: Geoffrey Gobert
Co-Chairperson: Poom Adisakwattana

[SC20-00052]
Abstract Type :

3. Symposium

Abstract Title :

A Droplet Digital PCR (ddPCR) Workflow For The Detection Of Parasite And Intermediate Host eDNA In Water and Soil

Abstract :

All organisms shed DNA into their environment. This environmental DNA (eDNA) often degrades rapidly providing fine scale temporal inference of species presence. Recently the use of eDNA for the detection of parasite species has received growing attention due to its benefits over traditional sampling methodologies. The liver fluke, Fasciola hepatica, exhibits a complex lifecycle involving an aquatic snail intermediate host, commonly Galba truncatula at temperate latitudes, and a diverse array of mammalian definitive hosts, including agricultural ruminants and humans. Despite the importance of the external environment in the liver fluke lifecycle, traditional diagnostic methods rely on the detection of infection in the definitive host. Although reports of eDNA isolation of trematode parasites and their vector snails in environmental water samples are encouraging, these studies have relied on semi-quantitative cPCR or qPCR methods. Furthermore, G. truncatula spend considerable periods of time on mud surrounding water bodies. To date the presence of G. truncatula and parasite eDNA has not been examined in soil. The use of fully quantitative ddPCR platforms provides the opportunity for greater sensitivity and reproducibility of eDNA detection. To investigate the use of ddPCR for the detection of parasite and intermediate snail host eDNA, a workflow was developed utilising environmental samples (water and soil) collected from sheep and cattle farms in Northern Ireland. Environmental sample collection methodology and DNA extraction was optimised to allow reliable examination of parasite and intermediate host eDNA relative to in vitro amplification assays. Analysis suggests that it is possible to detect parasite and snail intermediate host eDNA from environmental water and soil samples. The isolation of F. hepatica and/or G. truncatula eDNA on a farm may provide pre-emptive warning of host infections earlier than current diagnostics, guiding anthelmintic treatment strategy. Furthermore, as F. hepatica has zoonotic potential, developing and optimising these technologies will also have clinical relevance.

S45_R5: Viral vaccine development and implementation
Chairperson: Beth-Ann Coller
Co-chairperson: Rapatbhorn Patrapuvich Rathod

[SC20-00220]
Abstract Type :

3. Symposium

Abstract Title :

Two-Years of Immunogenicity and Safety of a Purified Inactivated Zika Vaccine Candidate and Comparison With Natural Infections

Abstract :

Introduction: Sustained low levels of Zika virus (ZIKV) in Southeast Asia and Latin America underscore its significance as a public health threat for populations living in endemic countries and travellers. Therefore, an effective vaccine against ZIKV is a global unmet medical need. Here, we report immunogenicity and safety of our Purified Inactivated ZIKV Vaccine (PIZV) over two years. Methods: ZIK-101 (NCT03343626) was a phase 1, randomized, observer-blind, placebo-controlled, dose-selection study performed in 18- to 49-year-old adults at seven sites across the United States and two sites in Puerto Rico from 2017 to 2020. The primary objectives were safety, tolerability, and the immunogenicity of three dose strengths (2µg, 5µg, and 10µg) of PIZV administered each as two doses 28 days apart to flavivirus-naïve (FV-naïve) and flavivirus-primed (FV-primed) adults. Participants who received 10µg PIZV were followed over 2 years, and neutralizing antibody responses were compared with individuals with confirmed ZIKV infection from two natural history cohorts external to the study. Results: A clear dose-response trend was observed in all PIZV groups, and the highest dose was selected for further clinical development. Through 2 years post-vaccination, persistent immune responses with high geometric mean titers (> 100) were observed in both FV-naïve and FV-primed participants. Furthermore, 10µg PIZV-induced neutralizing antibodies responses comparable to individuals who underwent a natural ZIKV infection. No safety concerns have been identified for PIZV. Conclusion: Global rates of Zika virus are currently low, making human populations vulnerable to outbreaks of virus infection. Further clinical development of PIZV is an important global unmet medical need. Funding: This project has been funded in whole or in part with Federal funds from the Department of Health and Human Services (HHS); Office of the Administration for Strategic Preparedness and Response (ASPR); and Biomedical Advanced Research and Development Authority (BARDA), under Contract No. HHSO100201600015C. Any opinions, findings, and conclusions expressed in this material are those of the authors and do not necessarily reflect the views of HHS, ASPR, or BARDA.

[SC20-00076]
Abstract Type :

3. Symposium

Abstract Title :

MSD Vaccines for Tropical Diseases: Ebola and Dengue

Abstract :

Introduction: MSD is engaged in several unique global collaborations in support of two vaccine programs for tropical diseases: Ebola and dengue. The MSD Ebola vaccine (Ervebo) is indicated for the prevention of disease caused by Zaire ebolavirus in individuals 18 years of age and older and approved in over 40 countries. Post-approval trials, in parallel with widespread use of the vaccine in outbreak response, continues to generate additional information on the vaccine. MSD has also in-licensed attenuated dengue strains from the US NIH and is advancing development of the product (V181) to meet the global need for safe and effective dengue vaccines for dengue-naïve and -experienced populations. In 2018, MSD entered into a collaboration agreement with Instituto Butantan to share data and expertise to advance the development of each institution’s dengue vaccine, both of which are based on the same attenuated dengue strains from the US NIH. Methods: Five large-scale clinical trials (Phase 2 and 3) of the MSD Ebola vaccine, Ervebo, have been conducted in partnership with numerous public health partners and additional clinical trials are ongoing. A Phase 1 trial of the V181 MSD quadrivalent dengue vaccine candidate in flavivirus-naïve and -experienced populations has also been completed. Results: The MSD Ebola vaccine clinical trials demonstrated a high level of efficacy and immunogenicity and an acceptable safety profile of Ervebo in more than 15,000 adults. Additional studies conducted in children ≥1 year of age and HIV-positive participants are ongoing to assess the safety/immunogenicity of Ervebo in these populations. In a Phase 1 trial of the V181 MSD dengue vaccine candidate, both TV003 and TV005 formulations were generally well tolerated and robustly immunogenic. Furthermore, a single dose of the V181 TV003 formulation induced vaccine viremia and robust humoral immune responses to all four dengue serotypes in flavivirus-naïve and flavivirus-experienced adults. An overview of the design and status of ongoing clinical trials for both MSD vaccine programs (Ebola and dengue) will be presented. Conclusions: The MSD Ebola and dengue vaccine programs are two examples of the value of public-private partnerships to address important unmet medical needs. For the MSD Ebola vaccine program, additional data from post-approval trials will inform expanding the indication of Ervebo to other at-risk populations. While the Phase 1 data of the MSD dengue vaccine candidate supports further development of V181 for the prevention of dengue disease.

S46_R6: Critical care in tropical countries
Chairperson: Chairat Permpikul
Co-Chairperson: Arjen Dondorp
S47_R7: New targets for vaccination in melioidosis
Chairperson: Paul J Brett
Co-Chairperson: Narisara Chantratita

[IC20-00505]
Abstract :

Introduction : Burkholderia pseudomallei (Bp), the etiologic agent of melioidosis, causes severe disease in humans and animals. Diagnosis and treatment of melioidosis can be challenging and no licensed vaccines currently exist. Several studies have shown that this important bacterial pathogen expresses a variety of structurally conserved protective antigens that include cell-surface polysaccharides, cell-associated and secreted proteins. Based on this, such antigens have become important components of the subunit vaccine candidates that we are currently developing in our laboratory.

Methods : In the present study, the 6-deoxyheptan capsular polysaccharide (CPS) from Burkholderia thailandensis E555 was purified using a phenol-less extraction procedure, chemically activated and covalently linked to recombinant CRM197 diphtheria toxin mutant (CRM197) to produce CPS-CRM197. Additionally, immobilized metal affinity chromatography was used to prepare highly purified, recombinant, tag-less Bp hemolysin co-regulated protein 1 (Hcp1).

Results : Immunization of C57BL/6 mice with nanogram (low dose) or microgram (high dose) amounts of CPS-CRM197 plus Hcp1 resulted high-titer IgG and opsonizing antibody responses against the CPS component of the glycoconjugates as well as high-titer IgG and robust IFN-gamma secreting T cell responses against Hcp1. Following an inhalational challenge with a high dose (~40 LD50) of Bp K96243, 75% of the mice immunized with the low dose formulation and 67% of the mice immunized with the high dose formulation were still alive upon termination of the study at day 60.

Conclusion : Collectively, these studies help to better establish correlates of antigen-induced immunity against Bp and provide valuable insights towards the development of a safe, affordable and effective melioidosis vaccine.

[SC20-00025]
Abstract Type :

3. Symposium

Abstract Title :

DEVELOPMENT OF MELIOIDOSIS VACCINES USING SITE-SPECIFIC, SINGLE-POINT ATTACHMENT OF POLYSACCHARIDES TO NOVEL CARRIER PROTEINS

Abstract :

Burkholderia pseudomallei (Bp), the etiologic agent of melioidosis, causes severe disease in humans and animals. Diagnosis and treatment of melioidosis can be challenging and no licensed vaccines currently exist. Previous studies in our laboratory have demonstrated that subunit vaccines consisting of a Bp capsular polysaccharide (CPS)-based glycoconjugate (CPS-CRM197) co-formulated with recombinant Bp Hcp1 or TssM provide high-level protection against acute inhalational challenges of mice with Bp. Extending upon these findings, we recently set out to investigate the potential use of Hcp1 and TssM as novel carrier proteins for developing next generation polysaccharide-based glycoconjugates to immunize against melioidosis. To facilitate these studies, recombinant Hcp1 and TssM antigens engineered to possess C-terminal cysteine residues were expressed in Escherichia coli and purified using tandem nickel-cobalt affinity chromatography. Hcp1-Cys and TssM-Cys were then modified with heterofunctional cross-linkers to enable site-specific, single-point attachment of CPS or O-polysaccharide (OPS) to the carrier proteins. To assess the immunogenic potential of the glycoconjugates, C57BL/6 mice were immunized with the various glycoconjugates following which humoral and cellular responses were assessed by ELISA and ELISpot assays, respectively. Results of these studies indicated that the glycoconjugates stimulated the production of high-titer Hcp1-, TssM-, CPS- and OPS-specific IgG responses. Furthermore, we found that robust IFN-γ secreting T-cell responses were raised against both of the carrier proteins. Collectively, our findings suggest that production of glycoconjugates using site-specific, single-point attachment of CPS or OPS to Hcp1 and TssM may represent a promising approach for developing a safe and effective melioidosis vaccine.

[IC20-00506]
Abstract :

Introduction : Burkholderia pseudomallei (Bp) is a facultative-intracellular, Gram-negative bacterium that causes melioidosis in humans and animals. Previous studies in our lab have demonstrated that a capsular polysaccharide-based glycoconjugate (CPS-CRM197) combined with hemolysin co-regulated protein (Hcp1) provided mice with high-level protection against lethal inhalational challenges of Bp. In this study, we sought to identify cell-surface proteins that can be co-formulated with our lead subunit vaccine candidate to enhance its protective capacity.

Methods : To facilitate this study, we developed an in vitro culture system that promotes the expression of proteins that, similar to Hcp1, are upregulated when Bp is grown in media devoid of iron. Using a select agent excluded Bp strain that lacks both O-polysaccharide and CPS expression, bacterial cell pellets grown under iron rich and deplete conditions were exposed to Sulfo-NHS-SS-Biotin and then lysed to enable the affinity capture of biotinylated surface antigens.

Results : As expected, SDS-PAGE analysis of the captured antigens indicated that only a subset of the Bp proteome had been isolated, and that some of these proteins were differentially expressed under the two culture conditions. Additional analyses using LC/MS/MS and database searches demonstrated that at least 500 unique proteins were obtained using this approach. Of these, ~90 proteins were exclusively expressed in iron rich conditions, ~80 proteins were exclusively expressed in iron deplete conditions and ~160 were upregulated under iron deplete conditions.

Conclusion : Based on these findings, we are currently in the process of down selecting the ~240 proteins expressed under iron limiting conditions for use as potential melioidosis vaccine candidates.

S48_R8: Elimination of lymphatic filariasis
Chairperson: Mark Taylor
Co-Chairperson: Louise Kelly-Hope

[SC20-00029]
Abstract :

Background: Work on LF in Thailand started in 1949 and had been endemic only in some parts of country. National Program to eliminate LF was launched in 2001 followed WHA Resolution. Methods: Epidemiological data was reviewed to identify LF endemicity. Annually MDA, the core intervention was implemented in all implementation units (IUs) of 11 provinces with monitoring and interim surveys. Stop-MDA survey was conducted after consecutive 5 years of MDA and every 2 years in continued MDA IUS. Then, conduct post-MDA survey every 2-3 year for 5 years. In Thailand, surveys and treatment among domestic was conducted to prevent zoonotic transmission. Also, the chronic case was re-surveyed and registered for cares. Results: MDA was implemented during 2002-2006 in 357 endemic IUs of 11 provinces and were stopped in 270 IUS of 11 provinces by the stop-MDA survey in 2006. 87 IUs in Narathiwat had to be extended until 2012. Stop-MDA surveys, TAS in 2012-2013, showed positive case under critical cut off value in Narathiwat. Later TASs also demonstrated LF transmission interruption in all IUs. In elimination period, surveillance of migrant populations was intensified, showing Ag positivity rate of 0.75% (range: 0.14-2.75%) and Thai populations residing in close proximity were also concurrently tested and found zero positivity rate. And annual treatment among cats resulted in a decline of Mf prevalence. For lymphoedema case was registered and access to care services under health facilities. Conclusions: In September 2017, WHO certified the Ministry of Health Thailand eliminate lymphatic filariasis as a public health problem. Continued surveillance would be required and people affected with chronic manifestation would have access to treatment and care.

[SC20-00212]
Abstract :

Lymphatic filariasis (LF) had been endemic in some parts of Thailand, but in the year 2017, World Health Organization had acknowledged that Thailand’s Ministry of Health had eliminated lymphatic filariasis as a public health problem. Nevertheless, the recent global climate change has altered the geographic distribution of insects and affected the epidemiology of vector borne diseases, including zoonotic filariasis. Zoonotic filariasis has impact on the health and economy in both developing and developed countries. Thus, continuous monitoring for zoonotic filarial transmission is still necessary. This presentation updates the past decade’s situation of human case reports of zoonotic filariasis in the previously nonendemic areas in Thailand. The presentation also addresses some concerns regarding the increase of possible zoonotic transmission as well as several factors that may play a role in widening of zoonotic filariasis transmission in Thailand. The situation of filarial infection in reservoir hosts regarding species and prevalence of the parasites is also included in this presentation.

[SC20-00051]
Abstract :

National lymphatic filariasis (LF) elimination programmes frequently face challenges related to the implementation of mass drug administration (MDA) to interrupt transmission, and morbidity management and disability prevention (MMDP) to alleviate the suffering of affected populations. We aimed to develop and implement an operational research framework and suite of activities to address the wide-ranging barriers and optimize the elimination process. LF MDA and MMDP programmatic activities were assessed collaboratively across 12+ endemic country programmes in Africa and Asia. Information on national challenges were collated, and common themes identified to help develop key priority research areas, and related initiatives and tools. Country status, number of activities and training requirements were considered when operationalising research activities. Ten key research priority areas were identified. Five MDA-related areas included i) low endemicity ii) optimising MDA coverage iii) urban transmission vi) alternative strategies v) post-treatment surveillance. Five MMDP-related areas included i) patient estimates ii) access to care iii) quality of life vi) optimising therapy v) integrated health systems. Various novel initiatives and tools were developed and implemented; examples include vector control mapping, quality of life/mental health surveys, mHealth morbidity reporting tool, infrared thermal imaging. Each country had a unique set of priority research areas. The development and implementation of the operational framework and suite of activities intrinsically linked to national challenges helped to move programmes forward towards their elimination goal. This framework provides a practical template to adapt and address future challenges as they arise and enable countries to meet the WHO NTD roadmap 2021-2030 targets.

[SC20-00020]
Abstract :

Lymphatic filariasis is a leading cause of global disability, and the major form of secondary lymphoedema, with an estimated 36 million cases in 47 countries. Whilst LF is targeted for global elimination by 2030, patients with pre-existing pathology face a lifetime of progressively debilitating disease. Current treatment is limited to symptom management, whilst doxycycline has shown promise as a pharmacological intervention. to reduce LF pathology in early clinical trials. A first step to developing new therapeutics for filarial lymphoedema is to detail the underlying aetiology of lymphatic disease following filarial infection. Our laboratory has utilised mouse models of Brugia malayi filarial infection and developed bioimaging technologies to interrogate adaptive immune control of infection and lymphatic pathology development. In this talk I will detail the cellular and molecular mechanisms controlled by the initial type-2 polarised adaptive immune response to larval B. malayi infection and discuss our recent data proposing a central role for an alternatively-activated macrophage response in both control of filarial infection and initiation of lymphatic disease. Finally, I will introduce a potential role for bioactive lipids produced both by filariae and host as mediators of type-2 lymphatic disease which hold promise as targets for future affordable pharmacological intervention.

S49_R9: Snakebite
Chairperson: Nicholas Casewell

[SC20-00197]
Abstract Type :

3. Symposium

Abstract Title :

The burden of Snakebite envenoming

Abstract :

The estimated five million snakebites per year are an important health problem that mainly affect rural poor populations. The global goal is to halve both mortality and morbidity from this neglected tropical disease by 2030. Data on snakebite morbidity are sparse and mainly obtained from hospital records. We will look at these long term consequences and how these relate to the geographic differences in snake species. And will look at the evidence gaps in clinical and public health which need to be considered for progress towards reducing the harms caused by snakebites.

[SC20-00112]
Abstract Type :

3. Symposium

Abstract Title :

Snakebite in Thailand’s southern border provinces: clinical survey discloses high incidences of an invisible issue

Abstract :

Snakebite envenoming is an environmental, occupational and climatic hazard in many rural areas of Thailand. Narathiwat is one of southern provinces of Thailand, near the border with Malaysia. The local people mainly work in agricultural sector especially in palm oil plantation and fruit orchard where the number of snakebite victims considerably increased. A hospital based retrospective study of the prevalence of snake envenomed patients in Narathiwat was reported from 2017 to 2022. Over 400 snake envenomed cases were recorded (age 7-75 years). The most common clinical presentations were bleeding, pain and swelling at bite sites. Malayan pit viper (Calloselasma rhodostoma) and monocle cobra (Naja kaouthia) are widespread and cause numerous envenomings in this region. The majority of cases were male and admitted hospital at daytime. Bites occurred most commonly on the lower limbs followed by hand and other parts of body. No fatal cases were reported and no specific treatments such as fasciotomy were needed. Almost envenomed patients were received monospecific snake antivenom and other pharmacological treatment, e.g. antibiotics, NSAIDs and corticosteroids. However, complications such as skin rash, wheezing and associated allergic reactions following antivenom treatment were found. Moreover, insufficient antivenom and inappropriate amount of antivenom use were also reported in some hospitals. This might be due to the lack of knowledge and clinical experience of medical staffs to approach snake envenomed patients. To solve this issue, clinical training program in management of snakebite patients for medical staffs and make antivenom available are needed to reduce the serious complications observed following snakebite and anaphylactic effect of antivenom administration.

[SC20-00143]
Abstract Type :

3. Symposium

Abstract Title :

Research to meet diverse needs of tropical snakebite victims – the many contributions of the Kenya Snakebite Research & Intervention Centre

Abstract :

Snakebite envenoming (SBE) is a WHO-listed Neglected Tropical Disease that kills 32,000 people, annually, living in disadvantaged rural communities of sub-Saharan Africa (SSA). The disease leaves over 100,000 surviving victims with permanent physical and psychological disabilities. Available statistics on SBE in SSA are focal and grossly underestimate the true burden of disease. The case fatality rate in SSA is nearly double that of other regions, predominantly due to the use of ineffective treatments. The Kenya Snakebite Research and Intervention Centre (K-SRIC) was established in 2017 to undertake multi-disciplinary research leading to generation of SBE burden data, and development of diagnostic as well as therapeutic interventions. The establishment of K-SRIC has overseen major infrastructure development dedicated to SBE research, hosting a facility uniquely equipped with a bio-secure herpetarium that houses venomous snakes, venom-extraction facilities and laboratories. It is East Africa’s first facility with the skills and resources required to preclinically assess antivenom efficacy. Capacity in SBE clinical research and public health has also been facilitated by knowledge exchange and training with local as well as international partners. These efforts have resulted in the launch of Kenya’s first SBE clinical management guidelines and the first ever nation-wide attempt to determine the incidence of SBE – milestone achievements for the region. K-SRIC serves as a successful model of collaborative research towards reducing the burden of SBE morbidity and mortality in sub-Saharan Africa.

[SC20-00107]
Abstract Type :

3. Symposium

Abstract Title :

The trouble with antivenom

Abstract :

Snakebite has been recognised as a neglected tropical disease and is a significant burden in resource poor countries in the tropics, where there is a lack health infrastructure and availability of effective antivenoms. Unfortunately, the way forward has been slowed by varied agreement on antivenom quality, effectiveness and availability, and our understanding of the different clinical syndromes, in particular the importance of reversible versus irreversible venom effects. There has been less focus on the importance of early antivenom administration and therefore early diagnosis of systemic envenoming. A number of studies have demonstrated that early antivenom is effective in preventing myotoxicity and neurotoxicity in Australasian elapids, and the effectiveness of antivenom for venom induced consumption coagulopathy in Echis spp. This talk will explore the idea perhaps antivenom isn’t the universal treatment for snakebite, but a universal antivenom for all snakebites is a possibility. It is commonly thought that antivenom is the ‘magic bullet’, that cures all in snakebite. This belief ignores the fact that many pathophysiological processes in snake envenoming are irreversible. However, there is clear evidence that antivenom is effective for some clinical effects, and can prevent severe envenoming if given early. This means that early diagnosis of snake envenoming is essential to allow early administration of antivenom, when it will be most effective. Another problem is that antivenoms are biological therapies from last century – while vaccines and cancer immunotherapies have embraced human recombinant technology, antivenom manufacturer hasn’t changed since the first vaccines. This means that we continue to need a different antivenom for each snake, and reactions rates to antivenom are unacceptably high. Is it possible to develop a safer universal antivenom?

S51_R1: Ethics, community and public engagement in global health research
Chairperson: Phaik Yeong Cheah
Co-chairperson: Thomas Peto

[SC20-00195]
Abstract Type :

3. Symposium

Abstract Title :

Community engagement for ethical global health research

Abstract :

Community engagement is increasingly recognized as a critical element of medical research, recommended by ethicists, required by research funders and advocated in ethics guidelines. The benefits of community engagement are often stressed in instrumental terms, particularly with regard to promoting recruitment and retention in studies. Less emphasis has been placed on the value of community engagement with regard to ethical good practice, with goals often implied rather than clearly articulated. This article outlines explicitly how community engagement can contribute to ethical global health research by complementing existing established requirements such as informed consent and independent ethics review. The overarching and interlinked areas are (1) respecting individuals, communities and stakeholders; (2) building trust and social relationships; (3) determining appropriate benefits; minimizing risks, burdens and exploitation; (4) supporting the consent process; (5) understanding vulnerabilities and researcher obligations; (6) gaining permissions, approvals and building legitimacy and (7) achieving recruitment and retention targets.

[SC20-00134]
Abstract Type :

3. Symposium

Abstract Title :

Singing the song of Antibiotics- Engagement of community health volunteers through songs to make community aware about antimicrobial resistance

Abstract :

Background: Since the discovery of Penicillin, antibiotics have been used as miracle drugs in human and animals as prophylaxis, therapeutics, and growth promoters. However, its widespread use has led to the emergence of antibiotic resistance which is projected to rise in next decades. Among many other factors, behaviors of community members, their limited knowledge and lack of understanding associated with inappropriate antibiotics use is contributing towards the development of the current scenario regarding the resistance. Literature have highlighted the importance of community sensitization in the form of antibiotic awareness to influence patient and parent demand for antibiotic prescribing that can contribute in controlling antibiotic resistance. Methods: In Nepal, female community health volunteers (FCHVs) and tole health promoters (THPs) have been working as the frontline pillars of community-based health programs and play pivotal role as health promoters, dispensers and sometimes even as health service providers. “Singing the songs of antibiotics” aims to engage the FCHVs and THPs to raise awareness in community through songs composed by the health volunteers. Around 150+ community health volunteers (CHVs) are targeted to be engaged through this engagement activity from June-November 2022. First of all, the CHVs will be informed about the problem of resistance through presentation, videos on Anti Microbial Resistance (AMR) and discussion. After gaining knowledge regarding AMR, they will have to compose a song. Expected Outcome: Since June, around 75 CHVs have already participated in the engagement and already 4 songs on AMR have been composed. It is expected that around 10 songs will be composed by the end of November 2022. A competition will be held among these songs and the first song will be filmed to be used for other engagement activities. Conclusion: Music has been recognized as a powerful medium to influence the audiences easily and faster than any other medium of communication. Through “singing the songs of antibiotics”, we plan to engage the CHVs to make other community people aware about the problem of resistance and use the song composed by CHVs for future engagement activities.

[SC20-00073]
Abstract Type :

3. Symposium

Abstract Title :

Using Participatory Visual Methods to explore hidden ethical issues in health research participation on the Thai-Myanmar border

Abstract :

Health research participation in low-resource settings, including on borderlands, has the potential to exacerbate existing burdens to participants, which include but not limited to challenges around travel, safety, security, and economics. We conducted a qualitative ethics research study that explored the ethics of health research participation with a community residing on the Thai-Myanmar border. To supplement our in-depth interviews and to triangulate our findings from them, we conducted a participatory visual workshop with 9 members of the Tak Province Community Ethics Advisory Board (T-CAB) and 6 frontline healthcare staff, to co-create drawings and films. A Participatory Visual Method (PVM) approach was selected and introduced for the first time in this context. It has been shown that PVM is an approach to obtain views and perspectives not comfortably expressed with words through traditional interviews. This method allowed participants to freely discuss, reflect, raise, and present any ethical encounters, concerns, questions from participants’ point of view in the form of co-created drawings and films, which could have not been expressed out freely in another environment. PVM also provides a safe-in-confidence space where certain specific vulnerabilities and challenges related to research participation can be discussed. PVM can be regarded in this case as both data collection method and engagement tool. PVM through co-created drawings and films confirmed several issues we found from our interviews, including how research participation added to daily challenges and burdens for this population such as difficulties making the journey to the health facility, how they overcame these challenges and how they supported each other in this community. Moreover, participation in research also provided benefits in terms of improving health, and reducing deaths, especially from malaria, among pregnant women and children. Participants also gained more knowledge about their own health, learned to protect themselves and gained better access to care. This was demonstrated by early attendance to antenatal care by pregnant women. Lastly, being healthy and not having to suffer from illness allowed them to work and earn regular income, so that they can better support their families and improve their quality of life.

[SC20-00216]
Abstract Type :

3. Symposium

Abstract Title :

ETHICS AND ENGAGEMENT AROUND HUMAN CHALLENGE STUDIES

Abstract :

Introduction Malaria Infection Study Thailand (MIST) is the first malaria controlled human infection model (CHIM) programme of studies in Thailand and South East Asia. CHIM has been developed to better understand infectious human diseases, how they spread and to find new ways of prevention and treatment. CHIM’s fundamental procedure includes intentionally giving infectious agents to healthy volunteers which is controversial and ethically questionable compared to conventional clinical studies. In order to identify ethical and practical issues related to MIST, we have incorporated ongoing community engagement activities throughout the MIST project. Methods Different community engagement methods were used for different stakeholder groups. At the early stage prior to the clinical work inception, the MIST team engaged with professional key stakeholders, scientists, policy and media/communication influencers. We also developed a dedicated website. During the clinical study implementation, potential participants interested in the study were invited to be involved in information and Q&A sessions about the project. Throughout the study, outreach approach was employed by sharing simplified scientific information about the project and progress updates with the wider community. Results Concerns about ethical, safety and compensation aspects were frequently discussed by our stakeholders and potential participants. Disseminating accurate information to the relevant stakeholders is essential to avoid negative impacts from misinformation and rumours. Conclusions: It is important for researchers not to rush into implementing all types of studies including CHIMs. Engagement creates opportunities to improve the consent process, identify ethical and practical issues and create processes for resolving ethical problems that may arise.

S52_R2: A novel protection against COVID-19 for vulnerable populations
Chairperson: Weerawat Manosuthi
S53_R3: The Armed Forces Research Institute of Medical Science: a sampling of current scientific efforts
Chairperson: MAJ Erica Lindroth

[SC20-00188]
Abstract Type :

3. Symposium

Abstract Title :

Dynamics of Mucosal Immune Responses Elicited by Systemic Prime/Boost Vaccination

Abstract :

Mucosal surfaces play a critical role in HIV-1 transmission and disease pathogenesis, hence new vaccine strategies should induce protective mucosal immune responses. Previous studies demonstrated that additional boosting of the 6 months (mo) RV144 regimen with longer boosting intervals improved/maintained immune responses. Here we assessed cellular mucosal responses elicited after the RV144 ALVAC-HIV/AIDSVAX B/E prime/boost intramuscular vaccine regimen followed by additional late boosts (RV306). We collected sigmoid biopsies two weeks post the 6mo priming regimen and the 15mo and 18mo late boosts with ALVAC-HIV/AIDSVAX B/E. Dynamics of mucosal cell populations and vaccine-specific cellular immune responses were assessed by flowcytometry. Our data showed that the late boosts with ALVAC-HIV/AIDSVAX B/E induced mucosal CD4+ T cell homing and improved vaccine-specific mucosal CD4+ T cell responses including the induction of mucosal Th17 cells and increase in the frequency of IgA-producing plasmablasts. Detailed characterization of mucosal immune responses in future vaccine studies is warranted given that systemic vaccination induces differing patterns of immune response between compartments.

[SC20-00157]
Abstract Type :

3. Symposium

Abstract Title :

Highly differentiated CD57+NKG2C+ NK cells in HIV-1 infection

Abstract :

Natural killer (NK) cell function and phenotype is influenced by ongoing and previous viral infections. Human cytomegalovirus (HCMV) infection expands a population of highly differentiated CD57+NKG2C+ NK cells. This NK cell population is also present in HIV-1-infected individuals. We assessed NK cells from 64 HIV-1-infected and 18 HIV-1-uninfected donors to determine the relative frequency of CD57+NKG2C+ NK cells and characterize their function and phenotype. Highly differentiated CD57+NKG2C+ NK cells were more frequent in HCMV-infected donors relative to HCMV-uninfected donors and were exaggerated in HIV-1/HCMV co-infected donors. The frequency of CD57+NKG2C+ NK cells remained stable in antiretroviral therapy (ART)-treated individuals. CD57+NKG2C+ NK cells from HIV-1-infected individuals mediated cytolysis through NKG2C and were robustly activated following anti-HIV-1 antibody-dependent stimulation. Finally, CD57+NKG2C+ NK cells from HIV-1-infected donors exhibited reduced expression of the inhibitory NKG2A receptor. Highly differentiated CD57+NKG2C+ NK cells are abundant in HIV-1-infected individuals. These NK cells are highly functional and have potential utility for strategies to cure HIV-1 infection.

[SC20-00113]
Abstract Type :

3. Symposium

Abstract Title :

Field evaluation of transfluthrin treated military materials against Phlebotomine sand flies (Diptera: Psychodidae) in Thailand

Abstract :

The effect of transfluthrin applied to military netting materials was field tested to determine the impact on sand fly populations in rubber tree plantations in Chanthaburi province, Thailand. Two different military barrier structures (HESCO; 2 x 2 x 2.5 m, and ULCAN; 3 x 3 x 2 m) were constructed and lined with two types of netting materials; thick felt-like material and ultra-lightweight camouflage netting. Transfluthrin treated strips were hung inside the military barrier structures. The effectiveness of the treated strips was evaluated by sampling natural sand fly populations using CDC light traps baited with dry ice. Traps were operated for 14 hours (1800-0800) at 3 time points (1 day before application and at 0 and 2 weeks post application). All collected sand flies were separated by sex and morphologically identified to the species level and counted. The majority of sand flies captured at this location were Sergentomyia iyengari. The number of females collected by CDC light traps was analyzed using a generalized linear mixed model with Poisson distribution and a log link function. The presence of transfluthrin treated strips significantly reduced sand fly populations up to 2 weeks post application. Our findings demonstrate that spatial repellent treatments of military materials could potentially serve as an effective tool for the military and for sand fly control in Thailand.

S54_R4: Strongyloides-the neglected soil transmitted helminth: a global perspective
Chairperson: Harsha Sheorey
Co-Chairperson: Siddhartha Mahanty

[SC20-00080]
Abstract Type :

3. Symposium

Abstract Title :

Strongyloidiasis – Epidemiology in High & Middle Income Countries

Abstract :

Strongyloidiasis, primarily caused by the soil transmitted helminth Strongyloides stercoralis, remains an important neglected public health problem in many low- and middle- income tropical countries. However, there is a widespread misconception that this “tropical” disease is restricted to such settings. In fact, strongyloidiasis remains a disease affecting marginalised and underserved populations worldwide, including in several middle- to high- income sub-tropical and temperate countries. Foci of infection and possibly transmission remain in some underserved populations within the United States of America. Some remote Aboriginal communities in Australia are hyperendemic, with prevalence rates in excess of those seen in many low-income country settings. In the Australian context infection is also observed in non-remote northern regional centres and cities. In Europe, infection and transmission continues in some Roma communities of Central Europe, and in underserved populations in several regions of Eastern Europe and Central Asia. Sporadic autochthonous infections continue to be identified in other high- income nations such as Japan, Italy, Spain and France. An emerging concern is the rate of undetected chronic S. stercoralis infections in immigrants residing in high- income nations, who remain undiagnosed until they present with severe disease later in life. Strongyloidiasis remains “the most neglected tropical disease”, a term which particularly applies to its continued prevalence and transmission in high income nations where, in most cases, no co-ordinated public health control program to eliminate this condition exists.

[SC20-00097]
Abstract Type :

3. Symposium

Abstract Title :

Molecular diagnosis of strongyloidiasis

Abstract :

The laboratory diagnosis of strongyloidiasis has traditionally been based primarily on the detection of Strongyloides stercoralis larvae by microscopic examination of stool samples. Microscopic examination, however, is notoriously insensitive and concentration techniques are laborious and cumbersome, in addition, these techniques are highly dependent on living larvae, making transport of samples problematic. The sensitivity of serological techniques is high, but due to possible cross-reactions with other parasites and slow decrease in the amount of antibodies after treatment, their specificity remains unclear. Molecular methods have been used in several countries with differing sensitivity and specificity reported probably due to differences in method, reference technique and study setting. It is important to be aware of the factors and pitfalls that can influence the performance of diagnostic techniques, especially with regard to the difficult diagnosis of strongyloidiasis. Think of the DNA extraction method, the genetic target that is used, the technique itself, but the research population is certainly an important factor. proof of principle of new advanced techniques such as digital PCR and metagenomics has already been shown, however, these techniques are not yet sufficiently evaluated and available for daily diagnostic practice yet.

[SC20-00063]
Abstract Type :

3. Symposium

Abstract Title :

Awareness of strongyloidiasis in Strongyloides stercoralis and Strongyloides fuelleborni in reservoir hosts as a concerning issue in Southeast Asia through molecular epidemiology

Abstract :

Strongyloidiasis is soil-transmitted helminthiasis noted as one of the important-neglected tropical diseases, with Strongyloides stercoralis and S. fuelleborni recognized as human pathogens. This study analyzed 951 and 117 cytochrome c oxidase subunit 1 (COI) sequences of S. stercoralis and S. fuelleborni from GenBank by population genetic and phylogenetic methods. The results revealed that S. stercoralis populations are globally transmitted but with moderate genetic differentiation between populations. Conversely, S. fuelleborni populations are isolated by their localities with high genetic differentiation. For S. stercoralis in Southeast Asia, molecular evidence showed Type A has been isolated from various hosts, including humans, while evidence of type B was detected only in dogs. The distribution of S. stercoralis is highly likely to have experienced dispersal by human activities rather than gene flow. S. stercoralis can thus be transmitted between humans, in particular, through their pets or from soil contaminated with the feces of infected stray dogs. For S. fuelleborni, although reports have been mostly limited to primates, deforestation and increased anthropogenic activities may increase the chance of close contact between reservoir hosts and humans. We conclude that not only should human strongyloidiasis be concerned, but the detection and deworming of pets and stray dogs/cats should be continuously conducted to control S. stercoralis transmission.

S55_R5: Kinetoplastid diseases
Chairperson: Frederick S Buckner
Co-Chairperson: Madhubala Rentala

[SC20-00135]
Abstract Type :

3. Symposium

Abstract Title :

Aminoacyl-tRNA synthetases and their paralogs as a novel class of drug targets for the treatment of Visceral leishmaniasis

Abstract :

Leishmania donovani, a protozoan parasite, is the causative agent of visceral leishmaniasis. Due to the development of resistance against the currently available anti-leishmanial drugs, there is a growing need for specific inhibitors and novel drug targets. In this regard, aminoacyl tRNA synthetases, the linchpins of protein synthesis, have received recent attention among the kinetoplastid research community. Aminoacyl-tRNA synthetases play an essential role in translation and constitute a novel class of promising drug targets that when inhibited lead to cell death. Leishmania possesses 26 aminoacyl tRNA synthetases (11 Class I; 14 Class II; 1 non-canonical) of archaeal/eukaryotic origin. Our comprehensive bioinformatic analysis revealed 26 aminoacyl tRNA synthetases and four freestanding editing domains (Gowri et al, BMC Genomics 13: 621, 2012). We also identified two EMAP-II-like proteins similar to human EMAP-II-like proteins suggesting their participation in multisynthetase complex formation. We have characterized the following tRNA synthetases: tyrosyl-tRNA synthetase (Sneha et al., JBC, 2016, Scientific Report, 2015), Selenocysteine tRNA synthetase (Reetika et al. JBC, 2016), Asparagine tRNA synthetase (JBC, 2014), Lysyl tRNA synthetase (mSphere, 2017) and Leucyl tRNA synthetase, (Reetika et al, Antimicrob Agents Chemother. 2018, Smriti et al, J Biosci, 2021), threonyl tRNA synthetase (Sanya et al, PLoS Negl Trop Dis, 2018) We report the uniqueness of these tRNA synthetases in the Leishmania parasite. We have recently characterized the role of two aminoacyl-tRNA synthetase-associated proteins EMAPI and EMAP II (Endothelial Monocyte Activating Polypeptides 1 and 2) of Leishmania donovani in chemotaxis of human monocytes. (Smriti et al, Acta Tropica, 2022). We report the uniqueness of these tRNA synthetases in the Leishmania parasite. Of these, Leishmania has a single copy of class I leucyl-tRNA synthetase. This enzyme is essential for the parasite and susceptible to an anti-fungal inhibitor AN2690 and thus appears to be a promising drug target. The role of CP1 domain in editing the activity of LRS has also been worked out. Leishmania tyrosyl-tRNA synthetase is an indispensable single copy class I enzyme involved in aminoacylation function and also exhibits immunomodulating activity by binding to host macrophages with its ELR motif and triggering the enhanced secretion of pro-inflammatory cytokines. Among class II enzymes, Leishmania possesses a dual copy lysyl-tRNA synthetase encoded by chromosomes 15 and 30, respectively. The enzyme encoded by chromosome 15 is essential for the parasite and inhibited by Cladosporin, a fungal secondary metabolite. The non-canonical enzyme selenocysteinyl-tRNA synthase helps in the synthesis of three selenoproteins in Leishmania. Also, a novel tRNA synthetase paralog of bacterial origin, asparagine synthetase A has been characterized as a potential drug target in Leishmania. The role of two aminoacyl-tRNA synthetase-associated proteins (Endothelial Monocyte Activating Polypeptides 1 and 2) of Leishmania donovani in the chemotaxis of human monocytes has also been worked out. Our study provides a framework for designing a new class of drugs against the Leishmania parasite.

[SC20-00035]
Abstract Type :

3. Symposium

Abstract Title :

Incomplete Recruitment of Protective T Cells Is Associated with Trypanosoma cruzi Persistence in the Mouse Colon

Abstract :

Trypanosoma cruzi is the etiological agent of Chagas disease. Following T cell-mediated suppression of acute-phase infection, this intracellular eukaryotic pathogen persists long-term in a limited subset of tissues at extremely low levels. Immunisation by prior infection and drug cure results in suppression of the acute phase parasite burden but still allows parasites to establish chronic infection in the gastrointestinal tract. The reasons for this tissue-specific chronicity are not understood. Using a dual bioluminescent-fluorescent reporter strain and highly sensitive tissue imaging that allows experimental infections to be monitored at single-cell resolution, we undertook a systematic analysis of the immunological microenvironments of rare parasitized cells in the mouse colon, a key site of persistence. We demonstrate that incomplete recruitment of T cells to a subset of colonic infection foci permits the occurrence of repeated cycles of intracellular parasite replication and differentiation to motile trypomastigotes at a frequency sufficient to perpetuate chronic infections. The lifelong persistence of parasites in this tissue site continues despite the presence, at a systemic level, of a highly effective T cell response. Overcoming this low-level dynamic host-parasite equilibrium represents a major challenge for vaccine development.

[IC20-00430]

Abstract :

Introduction : The drug discovery pipeline for neglected kinetoplastid diseases remains sparse, and of note, leishmaniasis drug discovery has had limited success in translating potential drug candidates into therapies.

Methods : To discover new compounds active against Leishmania donovani, a structurally diverse synthetic library was screened. Hit molecules, active against both promastigote and intracellular amastigote stages, with minimal cytotoxicity against a panel of mammalian cells were identified, and analogues tested. Compounds were profiled against L. donovani causing visceral leishmaniasis in the Indian subcontinent and L. infantum chagasi responsible for visceral leishmaniasis in Brazil. To compare strain specific differences, a genetically modified L. donovani strain of one isolated from the Sudanese population, was also evaluated. Compounds with optimal in vitro profiles were tested in vivo using the L. infantum chagasi hamster model.

Results : The development of two lead compounds, BZ-1 and BZ-1I, with potent in vitro anti-leishmanial activity against intracellular amastigotes (nM activity) and selectivity are highlighted. Biological profiling demonstrated that compounds were active against intracellular parasites from species and strains of the Old and New World including L. donovani (Old World – Indian and Sudanese strains) and L. infantum chagasi (New World). In vivo evaluation using the hamster model illustrated that the activity observed in vitro was translated in vivo.

Conclusion : Our data suggests that further development of these compounds is warranted as they provide urgently needed chemical starting points for the development of novel lead series for future anti-leishmanial therapeutics.

[SC20-00178]
Abstract Type :

3. Symposium

Abstract Title :

Insights into leishmaniasis epidemiology in the United States: September 2021 through July 2022

Abstract :

Background: Leishmaniasis is a rare parasitic disease in the United States, occurring primarily in travelers, migrants, and military personnel. The true incidence is unknown since leishmaniasis is not a nationally notifiable condition. When CDC testing paused from September 2021 to July 2022, our laboratory became the primary reference laboratory for molecular diagnosis of leishmaniasis in the United States. Methods: We employed a PCR and Sanger sequencing assay for detection and taxonomic identification of Leishmania spp. in our clinical laboratory. The assay targets the multicopy, taxonomically informative mini-exon gene with a limit of detection of 1 genome. Results: We report the first 88 cases detected from 173 patients and 203 specimens. Positive cases were identified in 38 states. 67 cases (76%) were subgenus Viannia (52 L. guyanensis complex, 15 L. braziliensis complex); 17 (19%) were L. mexicana complex and L. tropica complex, each; 3 (3%) were L. major; one could not be identified beyond genus. We identified 20 novel mini-exon alleles. Mini-exon sequences often correlated with or indicated travel/migration case history. All positive cases represented cutaneous or mucocutaneous disease, although samples were received to evaluate for visceral disease, including CNS, lymph node, and ocular specimens. Median age of positive cases was 39.3 years [range 2.5 to 81.6] and cases were frequently pediatric: 18% (16) were < 18 years and 11% (10) were < 10 years. Patients > 65 years represented 9%. Among 33 positive cases with known history, 26 represented US-based travel to endemic areas (1 military) and 7 had a migration history. By specimens, the overall positivity rate was 48%. pathologist-reviewed tissue was more likely to be positive than fresh tissue (61%, 60 / 99 formalin-fixed vs 37%, 38 / 104 total fresh; p = 0.0007, Fisher’s exact), likely reflecting the value of histopathologic evaluation for intracellular organisms. Conclusion: In an 11-month period, 88 cases of cutaneous or mucocutaneous leishmaniasis were detected in our reference laboratory. As testing volumes have increased during and since the study period; we anticipate detecting 100-150 unique cases in calendar year 2022. This case series highlights how clinical laboratories with national reach can provide epidemiologic information about the occurrence of leishmaniasis with species-level detail.

S56_R6: Roles of flies in health
Chairperson: Kabkaew Sukontason
Co-Chairperson: Heo Chong Chin

[IC20-00380]
Abstract :

Introduction : Forensic entomology is the study of insects and arthropods pertaining to legal issues. Thus far, research and case studies on forensic entomology have been carried out in several public institutions in Malaysia.

Methods : In this presentation, several forensic cases using insects as evidence to determine the minimum postmortem interval (mPMI) will be highlighted.

Results : In terms of research, we have conducted: (1) a study using mites as location indicators in four different ecoregions in Malaysia, (2) an insect succession study on a wild boar carcass placed in Taman Negara National Park; (3) a biochemical study to determine the dynamic of Juvenile Hormone (JHBIII) concentration in maggots in relation to their age for the determination of mPMI, and last but not least, a carrion ecological study using penguin carcasses in Antarctica to understand how decomposition took place under such extreme environment.

Conclusion : All these studies aim to address the gap and fundamental questions in forensic entomology of the Tropics.

[SC20-00034]
Abstract Type :

3. Symposium

Abstract Title :

Forensic entomology molecular bioinformatics: Current concepts, trends and challenges

Abstract :

Forensic entomology could provide valuable data for decomposed corpses in forensic investigations, especially for the postmortem interval (PMI) estimation. Many studies on the community succession of arthropods, species identification and age calculation of necrophagous insects have been demonstrated through various research experiments, as well as the nocturnal oviposition, sexual size dimorphism and intraguild competition have been observed. But the fundamental reason is that a great deal of studies still remains in superficial observation and simple statistical analysis, the field is almost completely lacking in empirical validation studies, and which raises doubts about the stability and accuracy of entomological evidences in actual cases. Even for the simplest analysis, i.e., estimating maggot age from degree of development (size, instar) when corpse conditions are known, we do not know the error rate. Therefore, we need to propose new innovation theories and methods, as well as introduce the most cutting-edge technologies into forensic entomology, such as multi-omics method to deeply uncover molecular mechanisms of necrophagous behaviors, so as to make up for the defects and disadvantages of the current methods. Thus in this present review, limitations hindering the growth of this field and the way forward for future studies will be seriously highlighted.

[IC20-00556]
Abstract :

Introduction : The filth flies are of medical and forensic importance. Identification of species is mandatory to be further applied, specifically in forensic investigations. For identification, preparation of fly specimens collected from the field and/or death scene is crucial. This presentation aims to demonstrate how to prepare filth fly specimens to be examined under a light microscope (LM). The technique of photography using a digital camera is displayed.

Methods : Methods for collecting filth flies from natural habitats are demonstrated. Adult flies were killed using butane gas or ice, while larvae were boiled with chemicals heated from self-heating food packages. In the laboratory, the eggs were stained using a 1% potassium permanganate solution. For fly larvae, two clearing techniques were shown; using 10% KOH and mounting medium (Hoyer’s solution and Euparal), to examine the cephaloskeleton, larval spine, and posterior spiracle. As for puparia, specimens were firstly cleaned before being examined using LM. Photographs of specimens were performed using the focus stacking technique.

Results : This study demonstrates alternative methods for preparing fly specimens. Stacking images produced by each device display differing levels of magnification and image detail.

Conclusion : Preparation of fly specimens collected from the natural habitat and/or death scene was essential for species identification.

[IC20-00383]
Abstract :

Introduction : Death is a process naturally present in all ecosystems. However, mass mortality events (MMEs) are unique instances where a larger than average number of individuals perish in a relatively short time. These events are increasing in both magnitude and frequency with the effects of MMEs – particularly long-term effects – being understudied and unknown. To better understand the potential long-term effects of MMEs, I capitalized on a previous MME experiment to determine if certain ecosystem properties and communities remained affected four years later.

Methods : This experiment crossed three input treatments (control (none), carrion, or nutrient additive) with scavenger access (open or fenced plots). The effect of biomass size was also evaluated through random assignment of one of five biomasses, with treatments receiving either feral swine carcasses (25-726 kg) or the equivalent amount of nitrogen, potassium, and phosphorus nutrient additions.

Results : Four years later, I discovered that while soil nitrogen was largely unaffected, potassium and calcium were significantly different amongst treatments. Microbial communities also significantly differed at 182 kg treatments compared to others and indicated significant different effects between nutrient additive and carrion treatments. I found unexpected asymmetrical effects of increasing biomass on below ground and above ground arthropods. Surprisingly, biomass had a noticeable effect on above ground arthropods across abundance, family richness, and family evenness. However, there were little to no significant effects on the below ground arthropod communities.

Conclusion : These collective results demonstrate that mass mortality events can have potential multiple yearlong effects on ecosystems.

S57_R7: New targets for intervention in melioidosis
Chairperson: Shelton Wright
Co-Chairperson: Narisara Chantratita

[SC20-00201]
Abstract Type :

3. Symposium

Abstract Title :

Pulmonary gamma-delta T cells influence the innate immune response during melioidosis pneumonia.

Abstract :

INTRODUCTION: γδ T cells are highly conserved lymphocytes which may impact mucosal host defense. However, the role of γδ T cells in Burkholderia pseudomallei pneumonia is unknown. We hypothesized that pulmonary γδ T cells are critical to the host immune response during melioidosis pneumonia. METHODS: Wild-type C57BL/6J and tcrd-/- mice were infected with either ~10^3 CFU/lung aerosolized Burkholderia thailandensis or B. pseudomallei. Mice were followed for survival and health outcomes or, at pre-selected timepoints, whole lungs and bronchoalveolar lavage fluid (BAL) were assessed for bacterial replication, cell counts and protein quantification. RESULTS: tcrd-/- mice demonstrated significantly worse survival (P<0.01) and weight/temperature decline (P<0.05, both) compared to wild-type mice after B. thailandensis infection. tcrd-/- mice also had significantly more pulmonary bacteria at 24 and 48 hours after B. thailandensis infection (P<0.01, both) compared to wild-type mice. At 24 after infection, tcrd-/- mice had significantly higher whole lung neutrophil concentrations (P=0.02), but similar BAL neutrophil concentrations, compared to wild-type mice. Whole lung cytokine concentrations were similar between the two groups after infection. After B. pseudomallei infection, tcrd-/- mice had significantly worse survival compared to wild-type mice (P<0.001). CONCLUSION: Mice lacking γδ T cells have worse survival as well as worse health outcomes compared to wild-type controls after both B. thailandensis and B. pseudomallei infection. While pulmonary neutrophil recruitment appears enhanced after infection in tcrd-/- mice compared to wild-type mice, this response is ineffective in pulmonary bacterial clearance. Future studies will investigate the role of γδ T cells in neutrophil and macrophage bacterial clearance in pneumonia.

[SC20-00026]
Abstract Type :

3. Symposium

Abstract Title :

SAFETY AND IMMUNOGENICITY TESTING OF A MELIOIDOSIS SUBUNIT VACCINE CANDIDATE IN NON-HUMAN PRIMATES

Abstract :

Burkholderia pseudomallei is a Gram-negative bacterium that causes melioidosis, a severe and life-threatening disease in humans and animals. Diagnosis and treatment can be challenging and no licensed vaccines are currently available. Our previous studies have shown that immunization of C57BL/6 mice with a subunit vaccine consisting of a 6-deoxyheptan capsular polysaccharide-diphtheria toxin mutant (CPS-CRM197) conjugate combined with hemolysin co-regulated protein 1 (Hcp1) provided significant protection against an inhalational challenge with B. pseudomallei. A well-characterized animal model that mimics humans is needed for further development of melioidosis vaccines. This study aimed to determine the safety and immunogenicity of our CPS-CRM197 plus Hcp1 subunit vaccine in non-human primates (NHPs). Male and female Cynomolgus macaques were immunized subcutaneously with three doses of CPS-CRM197 plus Hcp1. At various time points throughout the study, blood was collected and plasma and peripheral blood mononuclear cells were isolated. Humoral and cellular immune responses against the vaccine antigens were determined using ELISA, opsonophagocytosis assays, IFN-gamma ELISpot assays and whole blood ex vivo stimulation assays. Immunization of the NHPs with CPS-CRM197 plus Hcp1 generated high-titer IgG responses against CPS and Hcp1. Immune plasma promoted opsonophagocytosis in comparison to pre-immune controls. IFN-gamma-secreting T cell responses against Hcp1 were detected via ELISpot and whole blood ex vivo stimulation assays. Importantly, the vaccine antigens were well tolerated and no adverse effects were observed following immunization of the NHPs. Collectively, the results of this study demonstrate that our CPS-CRM197 plus Hcp1 subunit vaccine is safe and immunogenic in NHPs.

[SC20-00159]
Abstract Type :

3. Symposium

Abstract Title :

Hemolysin co-regulated protein 1 (Hcp1) variant is associated with decreased virulence and low antigenicity in Burkholderia pseudomallei

Abstract :

Introduction Hemolysin co-regulated protein 1 (Hcp1) is a virulence factor of Burkholderia pseudomallei. hcp1, located within T6SS-1, plays an essential role in the B. pseudomallei intercellular spread. Hcp1 is a potential diagnostic target and vaccine candidate. We hypothesized that B. pseudomallei population may have variation in hcp1 and affect their virulence and antigenicity. Method Whole genome sequencing (WGS) analysis was used to examine the variation of hcp1 in 699 clinical isolates in Thailand. To assess the Hcp1 specific antibodies, we performed ELISA using two recombinant Hcp1 proteins from wild-type strain K96243 (WT) and variant strain DR90076A as target antigens. 33 plasma samples from melioidosis patients infected with WT (N=19) and variant (N=14) strains were used. To determine pathogenicity, we compared multinucleated giant cell (MNGC) formation efficiency in a human lung epithelial cell line after 10-h infection. Results By mapping WGS data against K96243 reference genome, we observed two Hcp1 types consisting of WT (N=684, 97.9%) and variant (N=14, 2.0%) in clinical isolates. 87% nucleotides and 81% amino acids of variant Hcp1 were identical to WT. The median levels of IgG against WT-Hcp1 from patients infected with WT strains was significantly higher than patients infected with variant strains. In contrast, low IgG levels against variant-Hcp1 was detected from both patient groups. MNGC formation analysis demonstrated that the variants induced less MNGC than the WT strains. Conclusion We have identified hcp1 variants in clinical B. pseudomallei isolates. Our data suggest that Hcp1 variation may influence the pathogenicity and immunogenicity of B. pseudomallei.

Symposium Day 5 28 October 20
S58_R1: Control of zoonotic diseases, with emphasis on the One Health approach
Chairperson: Jong-Yil Chai

[SC20-00082]
Abstract Type :

3. Symposium

Abstract Title :

One Health and schistosomiasis

Abstract :

The oft-repeated statement in the Introduction of many scientific publications of past years, including those of this author, held quite firmly that some African species (especially S. haematobium) were strictly human parasites, while the Asian schistosomes (Schistosoma japonicum and S. mekongi) were zoonotic . Of course, the Asian species are truly zoonotic, but ongoing studies of hybridisations in African species in revealing a complex interplay between the human-infecting species and animal-infection species. The propensity for such crossovers in Africa emphasise that schistosomiasis needs to be considered as a One Health concern. But further, many other aspects of the suite of schistosome infections of humans, including the occurrence of sylvatic cycles, of the impending, but not yet realised, risk of drug resistance, of the challenges we face because of climate change and those of altered landscapes, point to the importance of One Health concepts in understanding and combatting schistosomiases. In this One Health symposium, the author will present an overview of schistosomiasis as a One Health concern.

[SC20-00028]
Abstract Type :

3. Symposium

Abstract Title :

Focusing on lymnaeid snail vectors in experimental and field studies within a One Health action in human fascioliasis hyperendemic areas

Abstract :

Very high prevalences and intensities of infection by Fasciola hepatica have been reported from the Northern Bolivian Altiplano and the Peruvian Cajamarca Valley. Preventive chemotherapy by annual triclabendazole treatments is applied, but infections and re-infections occur in between the mass treatment campaigns. Multidisciplinary initiatives according to a One Health approach are therefore needed to define prevention and control measures. In such initiatives, lymnaeid snail vectors become crucial. The following is needed: (i) DNA sequencing for lymnaeid classification, (ii) to know which are involved in the disease transmission, and (iii) to assess the outer and inner borders of the endemic area. In the Northern Bolivian Altiplano, all lymnaeid populations proved to belong to a genetically monomorphic species, Galba truncatula, and the comparisons of transmission foci data from the 1990’s with those of 2018 demonstrated an endemic area expansion. Altitudinal, northward and southward expansions suggest movements of livestock transporting G. truncatula snails, with increasing temperatures transforming previously unsuitable habitats into suitable transmission areas. On the contrary, in Cajamarca different lymnaeid species were detected, including a species well known to be involved in the transmission to humans as G. truncatula, two species mainly linked to animal infection as Lymnaea neotropica and Pseudosuccinea columella, and a non-transmitting cryptic species as L. schirazensis. Thus, the Cajamarca province differs from the Bolivian Altiplano and indicates a pronouncedly more complex scenario for a One Health intervention. Funding: AECID 2017/ACDE/001583; RICET RD16/0027/0023 ISCIII-RETICS and FEDER; CIBER de Enfermedades Infecciosas CB21/13/00056, Madrid; PROMETEO 2016/099 and 2021/004 Valencia; Spain

[SC20-00072]
Abstract Type :

3. Symposium

Abstract Title :

Large multidisciplinary complexity of experimental studies and field surveys in a One Health initiative on fascioliasis in a human endemic area

Abstract :

Preventive chemotherapy by means of mass treatments by yearly triclabendazole mono-dose campaigns is being implemented in human fascioliasis hyperendemic areas within the WHO control strategy. Surveillance interventions demonstrate that infections and re-infections of mainly children occur in between the yearly treatments, due to the animal reservoir species assuring the Fasciola hepatica life cycle and consequent high transmission rates. A One Health strategy to complement preventive chemotherapy is now being followed in the area where the highest prevalences and intensities of liver fluke infection have been reported in humans. One key axis concerns the experimental studies and field surveys to assess the livestock reservoir species priorities. Laboratory studies include the follow-up of all life cycle phases. Field surveys include the assessment of prevalences, intensities and egg outputs. In this hyperendemic area, sheep and cattle are the main contributors to transmission, followed by pig and donkey. South-American camelids have proved to be negligible within a control action. Goats, horses, lagomorphs and rodents should not be considered for control measures in this area. This is the first time that a multidisciplinary One Health strategy is implemented in a human fascioliasis endemic area and it shows the high complexity of experimental studies and field surveys, long-term research activities and large funding for action sustainability which are needed for a One Health initiative on fascioliasis in a human endemic area. Funding: AECID 2017/ACDE/001583; RICET RD16/0027/0023 ISCIII-RETICS and FEDER; CIBER de Enfermedades Infecciosas CB21/13/00056, Madrid; PROMETEO 2016/099 and 2021/004 Valencia; Spain

S59_R2: Fluke Free Thailand
Chairperson: Watcharin Loilome

[SC20-00172]
Abstract Type :

3. Symposium

Abstract Title :

Result of Ultrasound screening for cholangiocarcinoma in Thailand: Experience from CASCAP, KKU

Abstract :

Result of Ultrasound screening for cholangiocarcinoma in Thailand: Experience from CASCAP, KKU Our ultrasound screening for cholangiocarcinoma (CCA) was started in 2014. We established the network system for screening and diagnosis CCA in every province of North East (NE) Thailand, some provinces in the North and the East of Thailand. Since the beginning to the year 2019, we did ultrasound screening for CCA more than 750,000 people. We will present the result of ultrasound screening of CCA between 2014-2019 (before COVID19), in Figures of CCA (location, morphology), stage of CCA and 5 year survival rate of CCA. Overall we had 766 CCA cases with histological proven, 163 from screening patients and 603 non-participant -Walk-in patients. We found ultrasound screening improve percent of detection of early stage CCA patients. This, therefore, increased number of candidate patients for curative resection. We found 5 year survival rate was about 48.3% in screening patients and 17.3% in non-participant -Walk-in patients. About 48.2 % were in early stage CCA and 10.0% in late stage CCA. We found 5 years survival rate in early stage intrahepatic CCA was 53.3%, early stage intraductal CCA for 51.6%, early stage periductal infiltrating CCA for 50.8% and screening intraductal CCA for 64.0%. In summary our CASCAP screening activities incur new simple tools and surveillance system for CCA detection, improve early stage CCA cases and CCA survival rates and provide potential reliable evidence for decision making in treating CCA patients

[SC20-00036]
Abstract Type :

3. Symposium

Abstract Title :

Digital Innovations for Combating Cholangiocarcinoma in Thailand (Isan Cohort)

Abstract :

Introduction: In 2013, a database system was designed for research called CASCAP Tools, in recent times being defined as Isan Cohort. It was used to reflect population at risk of Opisthorchis viverrini (OV) and cholangiocarcinoma (CCA) namely, population in the northeastern region of Thailand which is called “Isan”. However, Isan Cohort become a brand name as cohort members expanded beyond the Isan region. Methods: Isan cohort was online system that consists of many add-on web-applications were developed as modules. The OV-CCA is the main system. Tele-Radiology is for hepatobiliary ultrasonography screening and confirmation of diagnosis using CT scan or MRI. Pathology is for documenting the pathological findings. Surgery is for clinical data collection. Palliative Care is for following up the disease progressions. The last module is Randomized Controlled Trial, a research management system. Results: The adoption rate of CASCAP Tools among healthcare centers was greatly accelerated after the endorsement of the Government of Thailand that CCA was a national agenda and priority. The Isan Cohort was used for implementing the Programs for monitoring and evaluating interventions. There were approximately 4,000 healthcare centers that used the system with data for more than 20 million of the Thai population stored in the database. Conclusion: Isan Cohort is a comprehensive system for combating CCA for the Thai population. It is use to provides the foundation to provide answers in the future for currently unanswerable questions regarding OV associated CCA. Furthermore, it will enable healthcare professional to understand with a high degree of accuracy how changes over time.

[SC20-00043]
Abstract Type :

3. Symposium

Abstract Title :

Urine assay for opisthorchiasis: new tool for screening and assessment of treatment outcome

Abstract :

Improved diagnostic method for the detection of Opisthorchis viverrini (OV) infection in humans is essential for effective screening and control of OV and consequently reduction of cholangiocarcinoma (CCA). In 2015, we reported a novel urinary antigen detection method by a monoclonal antibody-based enzyme-linked immunosorbent assay (mab-ELISA) for diagnosis of opisthorchiasis. The urine assay method has been applied successfully for mass screening and post treatment follow ups in 21 provinces in Thailand and demonstrated the reduced the prevalence of opisthorchiasis by selective praziquantel treatment. In order to simplify the method and to comply with the quality-ASSURED criteria for point-of-care test (POCT) in rural and resource-limited settings by the World Health Organization, we aimed to develop a rapid diagnostic test (OV-RDT) to replace the mab-ELISA for diagnosis of OV infection. The OV-RDT has been developed to detect O,viverrini antigen using the specific monoclonal antibody in the lateral flow method. The OV-RDT had 94% sensitivity and 92% specificity compared with the standard fecal examination method and has been approved by Thai Food and Drug Administration (FDA) for screening of opisthorchiasis. An initial study suggested that it has similar performance to the conventional mab-ELISA. A large scale field test of OV-RDT is being implemented in Health Region 7 in northeast Thailand for prevalence mapping and subsequent planning for prevention and control. The availability of OV-RDT test provide a new tool for the screening and management of opisthorchiasis and should enhances the OV elimination program to reduce CCA in Thailand as well as other Southeast Asian countries.

[SC20-00014]
Abstract Type :

3. Symposium

Abstract Title :

Roles of community participation in the prevention of opisthorchiasis and cholangiocarcinoma

Abstract :

Liver fluke induced cholangocarcinoma (CCA) is an important public health problem in Thailand and countries in the lower Mekong basin. Past and current data underpin the enormous disease burden in terms of death, quality of life and socioeconomic cost. The Thai government recognized it as a national agenda and implemented a decade log program to eliminate the liver to reduce CCA from 2016-2025. The National Health Assembly of Thailand endorsed the CCA problem as a major health problem which required cooperation from all members of the society. Since the hot spot of CCA in Thailand is northeast Thailand, the Public Health Committee Zone 7 (PHPZ 7) has taken up the CCA problem with a mission to integrate agencies, organizations, public and private sector groups, networks, civil society to participate in solving this problem with the ultimate aim to create a social well-being for the Thai people. In 2019, the PHZPC 7 joined the campaign with the Cholangiocarcinoma Research Institute (CARI) and the Cholangiocarcinoma Foundation of Thailand to mobilize activities on mass public health education, food safety and cholangiocarcinoma screening activity in various provinces (>15) in Health area 7 in northeast Thailand. One of the urgent strategic plans is to find way to expand the proactive package for OV and CCA screening currently being operated by cholangiocarcinoma Screening and Care Program (CASCAP) of Khon Kaen University to become a universal care program supported by the National Health Security Office, such that all the Thai people have access for comprehensive medical examination and treatment of OV and CCA. The CASCAP model is now disseminated to other Southeast Asian countries.

S60_R3: Ivermectin mass drug administration for malaria elimination: preliminary results
Chairperson: Kevin C Kobylinski
Co-Chairperson: Jetsumon Sattabongkot Prachumsri

[IC20-00567]
Abstract Type :

3. Symposium

Abstract Title :

Mass drug administration of ivermectin and dihydroartemisinin-piperaquine against malaria in settings with high coverage of standard control interventions: a cluster-randomised controlled trial in the Gambia

Abstract :

Introduction : We assessed whether mass administration of ivermectin and dihydroartemisinin–piperaquine reduces malaria in The Gambia, an area with high coverage of standard control interventions.

Methods : This open-label, cluster-randomised controlled trial was done in the Upper River region of eastern Gambia. Thirty-two villages with a baseline malaria prevalence of at least 7% were randomized (1:1) to either the intervention (ivermectin and dihydroartemisinin–piperaquine plus standard control interventions) or the control group (standard control interventions). Three monthly rounds of mass drug administration were given during two malaria transmission seasons. Primary outcomes were malaria prevalence at the end of the second intervention year and Anopheles gambiae parous rate.

Results : The study population was 10 638, of which 4939 (46%) participants were in intervention villages. Coverage for dihydroartemisinin–piperaquine was between 49·0% and 58·4% in 2018, and between 76·1% and 86·0% in 2019; for ivermectin, coverage was between 46·9% and 52·2% in 2018, and between 71·7% and 82·9% in 2019. Malaria prevalence in November 2019 was significantly lower in the intervention (5.8%) than in the control group (12.8%)(p<0.001). The incidence of clinical malaria was significantly lower in the intervention than in the control group (IRR 0.21; 95%CI 0.10-0.43)(p<0.0001). No difference in vector parity was found although vector density was significantly lower in the intervention than in the control group.

Conclusion : In an area with high coverage of standard control interventions, mass drug administration of ivermectin and dihydroartemisinin–piperaquine significantly reduced malaria prevalence. Ivermectin decreased vector density but not vector parous rate.

[SC20-00210]
Abstract Type :

3. Symposium

Abstract Title :

Entomological impact of ivermectin mass drug administration to humans in Southern Thailand

Abstract :

BACKGROUND: Ivermectin has mosquito-lethal properties and treatment of humans was shown to reduce survival of important malaria vectors in the Greater Mekong Subregion (GMS) including Anopheles dirus and Anopheles minimus. Ivermectin mass drug administration (MDA) in West Africa was shown to be effective at reducing Anopheles gambiae survival, reducing the proportion of infectious mosquitoes, shifting the population age structure, and reducing number of clinical falciparum episodes. Thus, ivermectin MDA could be a potential new vector control measure to accelerate malaria elimination efforts the GMS. METHODS: Twenty clusters of approximately 300-600 persons were identified in Surat Thani, Thailand. Clusters were chosen based on malaria risk and were randomly assigned to treatment or control groups. Ten clusters were administered oral ivermectin (400 µg/kg) via MDA on three occasions spaced one month apart, while ten clusters served as untreated controls. In five treatment clusters and four control clusters mosquito collections were performed using the human landing collection (HLC) method. The HLCs were conducted before and after MDAs with each night having a treatment cluster paired with a control cluster. HLCs were performed for two consecutive nights and mosquitoes were collected at least once per week from each cluster. Mosquitoes were identified morphologically and An. minimus, An. dirus, An. maculatus and An. barbirostris were had their ovaries dissected to determine parity status. RESULTS: Mosquito collections and data analyses are ongoing. CONCLUSION: This is the first ivermectin MDA for malaria control conducted in the GMS. Results will be presented at the ICTMM meeting.

[IC20-S60-R3]
Abstract Type :

3. Symposium

Abstract Title :

Results from Vietnam, ivermectin mass administration to cattle (ZAIVE)

Abstract :
Treating cattle with ivermectin has been proposed as an important contribution to malaria vector management, yet the impacts are untested in field trials. Through a randomized village-based trial, this study quantified the effect of IVM-treated cattle on the anopheline populations in treated vs. untreated villages, central Vietnam
Resident cattle in three rural villages were IVM treated; with control cattle in three other rural villages. Village anopheline populations were quantified using cattle-baited traps for (ten-days before, ten-days after the 2-day treatment period). The impact was analyzed using a difference-in-differences (DID) approach with generalized estimating equations (negative binomial). Secondary analyses assessing the impact of the dose/density of treated cattle were also examined.
Across the intervention villages, 1112/1527 censused cows (73% overall) were treated with IVM. In both control and intervention villages, there was a marked decrease in total anophelines captured in the pre- vs. post-treatment period of 30-40% during the study. In the control villages, 1873 vectors were captured pre- and 1079 were captured post-treatment. Corresponding numbers for intervention villages were 1594 and 1101 respectively. In preliminary model results for the primary DID analysis there is no evidence for a difference in the change in trapping between intervention and control villages (IRR = 1.2; 95% CI; 0.60-2.4; p = 0.61). Potential follow-up studies and experimental refinements will be discussed.

S61_R4: Malaria elimination in the GMS and the GF RAI initiative
Chairperson: Arjen Dondorp
Co-Chairperson: Luciano Tuseo

[SC20-00202]
Abstract Type :

3. Symposium

Abstract Title :

Malaria elimination in the GMS and the GF RAI Initiative

Abstract :

The WHO Mekong Malaria Elimination (MME) programme is an initiative that supports malaria elimination strategies across the six countries of the Greater Mekong Subregion (GMS). Based in Phnom Penh, Cambodia, it was established in 2017 as a follow-up to the Emergency response to artemisinin resistance in the Greater Mekong Subregion, a high-level programme launched in 2013 to contain the spread of antimalaria drug-resistant parasites and provide life-saving interventions for all populations at risk of malaria in the subregion. The MME programme works in close collaboration with the WHO country offices, WHO regional offices in the Western Pacific and South-East Asia, the WHO Global Malaria Programme, as well as national malaria programmes and partners. The purpose of these collaborations being to: a. Promote dialogue, partnerships and coordination; b. Optimize regional and country surveillance; c. Facilitate targeted advocacy and communications on the ongoing efforts to eliminate malaria in the GMS; d. Provide technical support on accelerating strategies towards malaria elimination. The Malaria Elimination Database is a cornerstone of the MME programme. Since 2013, the Global Fund’s Regional Artemisinin-resistance Initiative (RAI) has been investing in Cambodia, Lao People’s Democratic Republic, Myanmar, Thailand, and Viet Nam. RAI is the Global Fund’s largest regional grant and the first catalytic funding with the defined goal of eliminating disease from a specific geographical region. The grant includes investments in health information systems, in the provision of integrated health services, and in the support for national health strategies and efficient supply chains, as well as in operational research tackling specific challenges for control and elimination. The five countries of the GMS aim to eliminate P.falciparum malaria by 2023 and eliminate all species of malaria by 2030.

[IC20-00594] [SC20-00224]
Abstract Type :

3. Symposium

Abstract Title :

Malaria elimination in Thailand

Abstract :

Thailand’s Division of Vector Borne Disease (DVBD) has made consistent progress toward its malaria elimination target of 2024, reporting just 2,893 cases in fiscal year 2021 (FY21). However, this year has seen an unexpected upsurge, with 7,439 cases in the first 10 months of FY22. These cases are largely clustered along international borders, with high concentration in the northwest of Thailand. The country has begun to coordinate with local officers in affected areas; however, timely outbreak response has been challenging. Thailand has also drafted guidance on prevention of re-establishment (POR), which incorporates vulnerability to parasite importation and receptivity for onward transmission. POR is an essential strategy for malaria elimination, and it requires accurate identification and support to specific areas at risk of malaria resurgence and reintroduction. With support from Inform Asia: USAID’s Health Research Program, the DVBD has developed an automated stratification to maximize use of available surveillance data. The stratification is a non-modeling method incorporating epidemiological and environmental variables to categorize subdistricts into various malaria transmission strata, with corresponding POR interventions for each stratum. The stratification results showed high concordance with Thailand’s detailed foci classification system, with 100% of active foci and 91% of residual foci categorized in the “Local transmission” stratum. The DVBD is now rolling out the stratification results to support provincial teams in developing robust POR plans to protect areas that are currently malaria free. Combined with additional surge interventions, Thailand is hopeful to maintain progress toward malaria elimination.

[SC20-00133]
Abstract Type :

3. Symposium

Abstract Title :

The Last Mile to Malaria Elimination: implementing aggressive interventions in Cambodia

Abstract :

Cambodia has achieved remarkable progress in the fight for malaria elimination, as witnessed by an 91% decline in malaria cases and a 98% decline in Plasmodium falciparum cases between 2017 and 2021, and zero malaria deaths since 2018. As malaria cases decrease, the concentrated control measures the country has been implementing since 2018 under the Intensification Plan are no longer enough to ensure the final push to P. falciparum elimination by the target year 2023. To accelerate the country’s progress towards elimination, Cambodia’s National Centre for Parasitology, Entomology, and Malaria Control (CNM) introduced new measures in 2019 involving the investigation and classification of every P falciparum case in the country, to guide the identification of active transmission foci. As of 2021, additional aggressive interventions have been implemented in the 100 remaining active foci in Cambodia. These include targeted drug administration (TDA) to reduce the parasite reservoir in these hotspots, intermittent preventive therapy for forest-goers (IPTf) to protect the highest-risk population against malaria, and weekly active fever screening (AFS) to reinforce the existing surveillance system and ensure all malaria cases are captured as early as possible to prevent onward transmission. We present the detailed methodology of these aggressive interventions, as well as observations of the potential impact on malaria case numbers, and lessons learned from and potential generalisability of the implementation of these interventions.

S62_R5: Meeting the challenge of outdoor and residual malaria transmission in the Indo-Pacific IVCC
Chairperson: Alongkot Ponlawat
Co-Chairperson: Jason Richardson

[IC20-00522]
Abstract Type :

3. Symposium

Abstract Title :

Expanding the toolbox for malaria vector control: The IVCC Indo-Pacific Initiative

Abstract :

Introduction : Improved vector control is needed to prevent malaria transmission amongst forest goers and inhabitants of villages across the Indo Pacific. Funded by the Australian DFAT, IVCC established partnerships to build capacities to develop, test and make accessible an expanded vector control toolbox in the region.

Methods : The BITE project partnership is using a staged approach to test vector control tools for use in forest packs provided to at risk populations in Cambodia. In Papua New Guinea, the NATNAT project partnership is testing efficacy, feasibility and acceptability of IRS, larval source management and volatile pyrethroid spatial repellents. These projects are complemented by mathematical modelling to predict impact on malaria transmission.

Results : BITE: Developed novel protocols for semi-field system (SFS) trials at Kesetsart University and AFRIMS demonstrating that the bite prevention tools tested go beyond personal protection to provide population-level impacts on mosquito feeding rates, longevity and fecundity. In Cambodia formative assessments and entomological field studies showed string user acceptance and significant protective efficacy with wild vector populations. Implementation research is ongoing for tool deployment and market research to enable access the public and private/commercial sectors. NATNAT: Completed an IRS community trial, expanded an insectary and constructed SFS and experimental huts; work is underway to test larval control and spatial repellent approaches.

Conclusion : Foundations are laid for an expanded vector control toolbox for Anopheles, and in the future, Aedes. IVCC continues to build partnerships and capacity for vector control evidence and access across sectors to fight growing threats of mosquito-borne diseases.

[IC20-00523]
Abstract Type :

3. Symposium

Abstract Title :

A series of semi-field studies using multiple biological endpoints to evaluate the personal and community protective efficacy of pyrethroid based bite prevention vector control tools

Abstract :

Introduction : Volatile pyrethroid spatial repellents (VPSR) and etofenprox treated clothing (ETC) are new tools for bite prevention for malaria elimination where vectors bite outdoors or during waking hours. It is also necessary to understand the effects on mosquitoes to ensure that additional products within a class function in the same way.

Methods : VPSR and ETC with and without picaridin topical repellent, on their own and in combination, were evaluated in two semi-field systems (SFS) in Thailand. The SFS studies used the standard measure of human landing rates but also included additional endpoints of disarming, blood feeding inhibition, and mortality, requiring recapture of mosquitoes that have been in contact with the intervention and therefore, cannot be measured in the field. Two rounds of SFS studies were completed, with learnings from the initial round applied to the second round.

Results : It was demonstrated that both these personal protection tools elicited substantial sublethal effects and some mortality. Findings indicates that the standardized measure of human landing rates does not capture the overall intervention impact of pyrethroids used for personal protection on mosquitoes and will underestimate protective efficacies. These interventions cause a range of ‘secondary effects’ that directly reduce vectorial capacity (i.e., mortality and effects on host seeking), indicating protection may extend from users to non-users.

Conclusion : These SFS studies move beyond landing rate as means of vector control tool impact assessment and represent a step forward in study design to help understand the various ways in which novel tools may impact target vectors.

[IC20-00536]
Abstract Type :

3. Symposium

Abstract Title :

Modelling the impact of novel vector control interventions on malaria transmission based on semi-field and field data

Abstract :

Introduction : Residual malaria transmission from outdoor biting mosquitoes remains a significant risk to malaria control and elimination. New classes of vector control tools, such as volatile pyrethroid spatial repellents (VPSR) and etofenprox-treated clothing (ETC), may be key in reducing outdoor exposure and malaria transmission. Mathematical modelling can help in assessing the effectiveness of new interventions and designing appropriate delivery strategies.

Methods : Semi-field studies were conducted in Thailand to estimate the impact VPSR and ETC on mosquito landing, feeding and survival. A field study in Cambodia further measured the relative reduction in outdoor biting. Mathematical models of mosquito host-seeking were fit to the semi-field data to estimate relative impact on mosquito host-encountering, biting, repellency, mortality and disarming. These estimates were modulated using a statistical model fit to the field data. The individual-based model, OpenMalaria was used to simulate the impact of VPSR and ETC on P. falciparum malaria transmission and disease.

Results : Both interventions reduced vectorial capacity and clinical incidence even at moderate intervention coverage in the population, with higher effectiveness in lower transmission settings. VPSR is likely to have a stronger impact than ETC, which also lost effectiveness faster.

Conclusion : We present a novel mathematical framework for estimating the impact of vector control interventions on mosquito biting, disarming and mortality from entomological semi-field and field study data. Our analysis suggests that VPSRs can substantially reduce clinical incidence, especially in lower transmission settings, and both interventions provide a community benefit comparable to insecticide-treated nets, especially if coverage and compliance are high.

[IC20-S62_R5]
Abstract Type :

3. Symposium

Abstract Title :

Building vector control capacity to reduce malaria transmission in Papua New Guinea

Abstract :

Purpose: Papua New Guinea (PNG) has the highest prevalence of malaria in the Western Pacific region, and despite renewed focus on bed nets and malaria case management over the past decade, malaria transmission is increasing. Malaria vector bionomics in PNG are complex with a heterogenous distribution of vector species across the county, high plasticity in host preference, diverse larval habitats and considerable outdoor and early evening biting occurring when bed nets are not protecting people. Vector-control is crucial to the prevention of malaria and multiple, complementary vector control tools are needed reduce transmission.
Methods: To address this situation the NATNAT program, Newly Adapted Tools Network Against Mosquito borne Disease Transmission is testing and optimising new and existing vector control tools in PNG. Complementary vector-control strategies include residual spraying, larval source management and spatial repellents.
Results: A new vector control testing facility as part of PNGIMR has been established in Madang province. The new facility will enable product evaluation under laboratory and semi-field conditions. In addition, we have conducted a pilot study to assess the efficacy and acceptability of residual spraying on the PNG north coast. The program is investigating the acceptability of new vector control tools at community and health system levels, and aims to strengthen policy and implementation networks and capacity with the PNG National Department of Health and other stakeholders such as the PHAs.
Conclusion: This presentation will provide a mid-project progress overview of the NATNAT program, highlight preliminary findings and experiences of the residual spraying pilot study and further discuss the pathway for testing and implementation of effective vector control tools and evidence-based vector control strategies in PNG.

S63_R6: Innovation and initiatives for malaria elimination in Thailand
Chairperson: Rungrawee Tipmontree
Co-Chairperson: Panupong Kowsurat

[SC20-00186]
Abstract Type :

3. Symposium

Abstract Title :

Webscope for malaria diagnosis

Abstract :

Webscope was an innovative low-cost and user-friendly tool developed in 2011 to take malaria images from a microscope by malaria microscopists in Mae Hong Son. The aims of this tool were 1) to increase malaria diagnosis accuracy, and 2) to improve the malaria quality control system by reducing the time response of cross-checking and precise on specific misdiagnosed blood film. Therefore, the first application of Webscope was to enable real-time microscopic consultation of difficult or equivocal diagnostic cases. It was comparable to online on-the-job training. The second application of Webscope was daily use for saving pictures or video files of blood films. Then cross-checker at the regional reference laboratory can re-examines the blood films videos on the next day. The result was clearly shown an improved performance of malaria microscopist on diagnosis with an increasing accuracy up to more than 99%. The most impact of this setting was better-quality of blood film preparation. The time used for confirming blood film was reduced from an average of 21 days to less than 2 days. However, these two applications of Webscope have some difficulties to continue. At present, Webscope has been used for other purposes such as a tool for malaria microscope training both in class and online. In addition, the Webscope is used for assessing mosquito-borne fogger by taking insecticide droplets’ images. Last but not least, it is used as a tool for developing and implementing Artificial Intelligence for malaria microscope diagnosis.

Free paper oral Day2 25 October
O1_R1: Antimalarial drug development: approached and progress
Chairperson: COL Mathirut Mungthin

[IC20-00058]
Abstract :

Introduction : The spread of Plasmodium falciparum (Pf) strains with Kelch mutant resistance markers beyond South-East Asia are concerning and threaten to reverse gains made through the years in the fight against malaria. Pf has developed resistance to almost all antimalarials in clinical use to date and therefore, novel antimalarials operating via novel mechanisms of action or novel modes of inhibition of existing validated targets are urgently required. In this regard, benzoxaboroles and triazolopyrimidine scaffolds are emerging as a promising chemotypes, which can be optimized to yield novel active antimalarials.

Methods : Hypothesis: Triazolopyrimidine and benzoxaboroles scaffolds can be optimized for antiplasmodium activity against Pf and offer insights into novel targets or pathways.

Results : A new series of benzoxaboroles was synthesized and evaluated for antiplasmodium activity against drug sensitive PfNF54 and resistant PfK1 strains. The data showed that these new benzoxaboroles possess good antiplasmodium activity with PfNF54 IC50’s = 0.12-2.6 µM and PfK1 IC50’s = 0.38-2.9 µM. Selected compounds showed high microsomal metabolic stability. Compounds in the series showed excellent solubility (110-200 µM at pH 6.5) and were not cytotoxic against the mammalian CHO cell line with an IC50 >50 µM. Triazolopyrimidines showed low antiplasmodium activity (PfNF54 IC50’s = 2.6->6 µM). Metabolomics analysis show new benzoxaboroles do not act on known pathways while triazolopyrimidines induce peptide synthesis perturbations and increase pyrimidine biosynthesis precursors. Cross resistance studies using DNA barcoded resistant mutant lines (>42 parasite lines pool) revealed the benzoxaboroles retained activity and thus did not show cross resistance. Taken together these data suggest that these series of compounds exert their antiplasmodium effects through novel targets.

Conclusion : A new class of benzoxaboroles are active against Pf and potentially act through novel pathways and targets. Triazolopyrimidines warrant further optimization to identify compounds with improved activity. The former series showed excellent in vitro microsomal metabolic stability and merit assessment for in vivo efficacy and pharmacokinetics studies to identify lead molecules for a future hit-to-lead optimization program.

[IC20-00262]
Abstract :

Introduction : In the fight against malaria, antifolate drugs were once regarded as safe, efficient drugs against the Plasmodium spp. parasite. However, upon years of drug pressure, the appearance of resistance-inducing mutations in their target enzymes has made these drugs obsolete. In 2012, our group has developed P218, a PfDHFR inhibitor that shows similar efficiency on the WT and mutated enzymes. This was achieved by combining an old antifolate core structure with a new functional group to target unexploited residues of the enzyme active site. Going a step further, we proposed to identify new building blocks for antifolate development using a fragment-based drug discovery.

Methods : Using an unbiased, high diversity commercial fragment library, we completed the parallel screens of the WT and mutant PfDHFR-TS enzymes. Fragments were first screened by Differential Scanning Fluorimetry, and primary fragment hits were confirmed by Surface Plasmon Resonance. Fragments hits were finally submitted to PfDHFR inhibition assay, providing a list of active fragment. Selected fragments were studied by X-ray crystallography and molecular docking.

Results : Our study identified 8 new fragment chemotypes that differ from existing antifolates and display enzyme inhibition in the low μM range. Interestingly, most fragments are selective to either enzyme target. Some fragments also display novel modes of binding and/or interesting kinetic properties. Initial lead design using these fragments showed promising inhibitory activity.

Conclusion : This study has unraveled new chemotypes of interest for anti-PfDHFR drug design, that allow to by-pass resistance limitations. These fragments constitute promising starting points for a new generation of antimalarial antifolates.

[IC20-00030]
Abstract :

Introduction : Tetrorchidium didymostemon is widely used in the treatment of malaria in southern Nigeria but has not enjoyed profound scientific investigation. This study was aimed at investigating the in vitro antiplasmodial activity and cytotoxicity of extracts and fractions of Tetrorchidium didymostemon.

Methods : Trager and Jensen method was used to culture Plasmodium falciparum and maintained in fresh O+ human erythrocytes at 3% hematocrit in complete medium (RPMI 1640). Synchronized ring stage P. falciparum strains Pf3D7 (1% parasitemia, 3% hematocrit) were incubated in 96 well microplate for 48 hours with different concentration of plant extract and fractions. Cytotoxicity was determined against Vero cell line using MTT assay. GC-FID was employed to identify bioactive constituents in the most active fraction.

Results : Methanol leaves extract had a better antiplasmodial activity (IC50 = 25 ± 0.81 µg/mL) in comparison to the stem bark extract (IC50 = 50 ± 1.09 µg/mL). Both extracts were not cytotoxic (CC50 > 30 µg/mL). The most potent extract (leaves) was fractionated using solvent of increasing polarity. Of the four fractions tested, the highest antiplasmodial activity was observed in the n-hexane fraction (IC50 = 3.92 ± 0.06 µg/mL). All fractions showed negligible cytotoxic effect on Vero cell line. The n-hexane fraction was considered highly active and non-toxic hence, was selected for GC-FID analysis. Kaempferol, α- pinene and β-caryophyllene occurred in high amount in this fraction and may therefore be responsible for its antiplasmodial activity.

Conclusion : Our findings therefore provide scientific data and justify T. didymostemon use in the treatment of malaria in southern Nigeria.

[IC20-00096]
Abstract :

Introduction : The development of antimalarial from natural sources is an alternative to overcome arthemisinin resistance. This study aimed to screen antimalarial activities of Streptomyces hygroscopicus fractions and to identify the active compounds of those active fractions using LC-MS as well as to estimate the potential activities by docking analysis.

Methods : Using the fraction collector, there were 47 fractions then by TLC, 6 fractions were selected. Each fraction was tested for antimalarial activity using PfLDH assay and inhibition test using PfMQO and PfDHODH assays. Six fractions (F1 – F6) and 1 crude extract of S. hygroscopicus at a dose of 40 μg/mL, 80 μg/mL, 160 μg/mL, and 320 μg/mL and atovaquone were exposed to 0.3% of P.falciparum culture and incubation for 3 days

Results : All fractions gave a high percentage of growth inhibition (Z score 0.68, S/B score 2.01). F1 and F2 fractions showed LDH – inhibitory activity with IC50 of 78.24 μg/mL and 85.66 μg/mL. F3-F6 fractions and crude extract showed 100% inhibition. There was inhibition to PfMQO activities with IC50 166.10 μg/mL (F3) and 472 μg/mL (crude extract). LC-MS succeeded in identifying several anti-malaria compounds: geldanamycin, rapamycin, nigericin, lonomycins, lenoremycin, dianemycin, carriomycin, septamycin, and etheromycin. Through docking, geldanamycin showed potential candidate as antimalarial by inhibiting the function of Hsp90 with the affinity of Hsp90-geldanamycin bond of -7.3 kcal/mol compare to the affinity of the Hsp90 bond with the control ligand of -7.8 kcal/mol

Conclusion : In conclusion there were several active substances from Streptomyces hygroscopicus as new candidates for antimalarial drug with specific target.

O2_R2: Dengue infection: virus evolution dynamics and prophylaxis
Chairperson: Padet Siriyasatien

[IC20-00162]
Abstract :

Introduction : Dengue virus (DENV) evolutionary dynamics are characterized by frequent DENV genotype replacements, which can be associated with changes in disease severity and human immunity. In 2012, a switch of DENV serotype 1 (DENV-1) genotype-I-Asia to genotype-IV-Pacific was associated with a massive outbreak in New Caledonia. In this study, we hypothesized that this genotype switch reflected a higher replicative fitness of the genotype-I-Asia in the vector and/or in the human host.

Methods : Competitive viral kinetics replication experiments with a 50:50 infectious ratio were performed with two strains per genotype isolated over the same period in 2012, on HEK 293 cells (in vitro studies) and on field-derived Aedes aegypti orally challenged (in vivo studies). Replication of each DENV genotype was measured by RT-qPCR for both experiments.

Results : Results obtained in vitro showed a better replicative fitness for DENV-1 genotype I-Asia for two viral combinations. For in vivo studies, results showed a clear fitness advantage of DENV-1 genotype-I-Asia for three out of four viral combinations at both infection and dissemination steps (ranging from 64 to 100% of infected mosquitoes with only genotype-I-Asia detected).

Conclusion : To conclude, these results suggest that vector-driven selection may have contributed to the DENV-1 genotype replacement that occurred in 2012 in New Caledonia that have led to a major change in dengue epidemiological profile. At the beginning of the vaccine era, a better understanding of the evolutionary mechanisms driving DENV genotype replacements is crucial as these ones may have an impact on vaccine strategies by the complexity of their antigenic properties.

[IC20-00369]
Abstract :

Introduction : Lactococcus lactis strain Plasma (LC-Plasma) was originally identified as a unique lactic acid bacteria which activates plasmacytoid dendritic cells (pDCs). PDCs play a critical role in anti-viral immunity and we proved LC-Plasma could prevent respiratory and gastrointestinal infectious diseases in vivo. In this study, we focused on the effect of LC-Plasma against dengue virus (DENV), as a representative vector-borne diseases.

Methods : 1. C57BL6J mice were administered 1 mg/day of heat-killed LC-Plasma for 2 weeks, then DENV was infected intraperitoneally. Two days after infection, the amount of virus and the expression of inflammatory genes in DENV-infected tissues was measured by qPCR. 2. HepG2 cells were pre-treated by LC-Plasma induced humoral factors, then DENV was infected. One day after the infection, the amount of virus in the supernatants was monitored by plaque assay and qPCR.

Results : 1. We found that the amount of DENV and inflammatory genes expression, such as il-6 and mcp-1, were significantly lower in LC-Plasma group in vivo. 2. We confirmed that proliferation of DENV was prevented by LC-Plasma induced humoral factors via type I IFN signaling pathway, and its effect was not depended on the serotypes of DENV in vitro.

Conclusion : These data suggested that LC-Plasma administration could accelerate the removal of DENV in vivo and suppress the proliferation of DENV in vitro. Thus, LC‑Plasma may be effective against DENV infection by stimulating pDCs, which results in the increased production of anti‑viral factors.

[IC20-00377]
Abstract :

Introduction : Dengue fever (DF) is a mosquito-borne disease caused by dengue virus (DENV) infection. Malaysia experienced more than 80,000 annually dengue cases in recent years. However, there are no effective treatments and prophylaxis. Lactococcus lactis strain Plasma (LC-Plasma), a food supplement reported to activate plasmacytoid dendritic cells and modulate anti-viral responses may confer protection against DF-like illnesses.

Methods : A randomized, placebo-controlled, double-blinded, parallel-group trial was undertaken to evaluate the efficacy of LC-Plasma on the presentation and severity of DF-like symptoms among healthy volunteers. Study participants were assigned into two groups, and consumed either placebo or LC-Plasma tablets (approximately 100 billion cells/day) for 8 weeks. The clinical symptoms of DF were self-recorded through questionnaires, and exposure to DENV was determined by serum antibody and/or DENV antigen tests.

Results : No significant differences between groups were observed for exposure to DENV, or the symptomatic ratio. Results obtained showed that participants from the LC-Plasma group reported a significant reduction in the cumulative incidence days of DF-like symptoms, which include fever (p < 0.001), muscle pain (p < 0.005), joint pain (p < 0.001), and pain behind the eyes (p < 0.001), compared to that of the placebo group. Subgroup analysis revealed a significantly (p < 0.05) reduced severity score in the LC-Plasma group when study sites were separately analysed.

Conclusion : Our findings suggest that LC-Plasma supplementation reduces the cumulative days with DF-like symptoms, and the severity of the symptoms. Daily LC-Plasma intake, hence, is shown to mitigate the DF-like symptoms.

[IC20-00386]
Abstract :

Introduction : Lactococcus lactis strain Plasma (LC-Plasma) ) is reported to have anti-viral effects via direct activation of plasmacytoid dendritic cells, which upregulate the production of type I and III interferons and play a critical role in anti-viral immunity.

Methods : A randomized, placebo-controlled, double-blind, parallel group study was designed for elementary schoolchildren, grades 1 to 3, in Vietnam. LC-Plasma or a control were administered to schoolchildren as a beverage (1.0 × 1011 count LC-Plasma / day / person). The primary endpoint was to determine the efficacy of LC-Plasma in reducing the cumulative days absent from school due to upper respiratory disease (URID) and gastrointestinal disease (GID), and the secondary endpoint was to evaluate the potency of LC-Plasma on URID/GID symptoms and general well-being scores.

Results : LC-Plasma intake significantly reduced the cumulative days absent from school due to URID/GID (p = 0.004) and URID alone (p = 0.005). LC-Plasma also significantly reduced the number of cumulative fever positive days during the first 4 weeks of intervention (p = 0.001) and cumulative days with diarrhea during the last 4 weeks of the intervention period (p = 0.01). The number of positive general wellbeing days was significantly improved in the LC-Plasma group compared with the control throughout the intervention period (p = 0.03, 0.04 in the first and last 4 weeks of the intervention, respectively).

Conclusion : These data suggest that LC-Plasma seems to improve the health condition of elementary school children and reduces school absenteeism due to infectious disease, especially URID.

[IC20-00436]
Abstract :

Introduction : Dengue transmission is a complex process that involves interaction of dengue virus (DENV), susceptible host and mosquito vector. Both dengue vectors, Aedes aegypti and Aedes albopictus, are long present in Malaysia. However, how the different DENV strains interact with Aedes mosquitoes to facilitate their transmission in Malaysia remains unclear. In the present study, we compared the viral replication competencies of two DENV-1 genotypes [genotype I (outbreak strain) and genotype III (non-outbreak strain)] in Ae. aegypti and Ae. albopictus. Identification of the link between the viral genotype and its phenotypic trait helps to reveal the mechanisms underlying the recurring dengue outbreaks.

Methods : The Ae. aegypti and Ae. albopictus mosquito colonies (< F5 generation) were established in the insectary. The mosquitoes were orally infected with blood meal spiked with DENV-1 (genotype I and III). The infected mosquitoes were dissected at various time points post-feeding. The salivary glands, midguts and saliva of the mosquitoes were harvested and subjected to RNA extraction. Real-time qRT-PCR was performed to determine the viral load of extracted RNA samples.

Results : In comparison to DENV-1 genotype III (non-outbreak strain), the DENV-1 genotype I (outbreak strain) replicated to a higher viral titer in Ae. albopictus. In contrast, the DENV-1 genotype III (non-outbreak strain) replicated to a higher viral titer in Ae. aegypti, in comparison to DENV-1 genotype I (outbreak strain).

Conclusion : Our finding suggests that the outbreak-causing DENV-1 strain replicates better in Ae. albopictus but not in Ae. aegypti.

O3_R3: Protozoal infection: parasite development, diagnosis and control
Chairperson: Porntip Petmitr

[IC20-00010]
Abstract :

Introduction : Developmental switching of Toxoplasma gondii from its fast replicating tachyzoite to slow replicating bradyzoite stage preferentially occurs in skeletal muscle and brain. Interestingly, terminally differentiated skeletal muscle cells (SkMCs),i.e. myotubes but not proliferating myoblasts support bradyzoite differentiation. However, the factors that drive this stage conversion of T. gondii in myotubes remained to be resolved.

Methods : By analyzing the host cell transcriptome and metabolome using RNAseq, GC-MS and RT-qPCR , we have identified candidates that might regulate bradyzoite differentiation in SkMCs.

Results : Analyzing RNAseq data and GC-MS analyses of uninfected and T. gondii-infected myotubes and myoblasts after labeling with13C-glucose indicated an increased pentose phosphate pathway (PPP) activity in myoblasts whereas myotubes preferentially fueled the tricarboxylic acid (TCA) cycle by anaplerotic reactions. Inhibition of the PPP using the glucose-6-phosphate dehydrogenase inhibitor dehydroepiandrosterone upregulated T. gondii bradyzoite antigen (BAG) 1 expression in both cell types. Furthermore, lower PPP activity as observed in myotubes led to reduced levels of NADPH and higher NADP+/NADPH ratios in myotubes than in myoblasts. Consistent with lower NADPH levels in myotubes, reactive oxygen species (ROS) levels were significantly higher in myotubes than in myoblasts. Modulation of endogenous ROS using the antioxidant N-acetyl cysteine inhibited T. gondii bradyzoite differentiation in both myotubes and myoblasts. Thus, physiological concentration of endogenous ROS as observed in myotubes but not myoblasts might favor T. gondii stage conversion in myotubes.

Conclusion : Our data confirm that lower PPP activities and higher level of endogenous ROS in mature myotubes trigger tachyzoite to bradyzoite stage conversion in SkMCs.

[IC20-00418]
Abstract :

Introduction : Toxoplasma gondii, the causative agent of toxoplasmosis, is an Apicomplexan protozoan parasite. Acute infection in pregnant females can lead to risk of life-threatening complications in the fetus. Therefore, strategizing towards early diagnosis of the pregnant female and subsequent adequate treatment during pregnancy could have a significant impact on the prevention of congenital toxoplasmosis. In the present work, the objective was to screen pregnant women with Bad Obstetrics History for toxoplasmosis using serology and its confirmation by two molecular based assays i.e.; conventional Polymerase chain reaction (PCR) & Loop Mediated Isothermal Amplification (LAMP).

Methods : Clotted blood samples (for serum) & whole blood samples were collected from 75 pregnant females. Serum samples were screened for Anti-Toxoplasma IgM & IgG antibodies by ELISA. All the whole blood and separated buffy coat samples were subjected to both PCR & LAMP targeting the Toxoplasma specific B1 gene. Samples found positive with PCR & LAMP were confirmed by Sanger sequencing.

Results : Eight (10.6%) serum samples tested positive for IgM antibody, six (8%) serum samples tested positive for IgG antibody and all IgG were of high avidity. One sample tested positive with both PCR & LAMP, and it was positive by serology on serial sampling.

Conclusion : Although serology is the main stay of diagnosis for acute Toxoplasma infection, our results suggest that molecular based detection can aid in accurate disease diagnosis and the detection limits may also be better for diagnosis and timely initiation of treatment among seronegative women.

[IC20-00258]
Abstract :

Introduction : Amoebiasis, including diarrhea and liver abscess, affects developing countries and travelers. Yet epidemiological data of this disease is inaccurate, leading to unnecessary treatment and ineffective control programs. These problems cascaded from the inaccurate diagnosis. The causative agent, Entamoeba histolytica, is difficult to be distinguished from closely related but less- and non-pathogenic species, E. moshkovskii and E. dispar, by the gold standard microscopy. Antigen-detecting immunodiagnosis is an alternative, but the currently available platforms fail to differentiate E. histolytica from E. dispar and are incompatible for unpreserved stool samples.

Methods : To overcome these limitations, we developed an immunodiagnostic assay for E. histolytica and E. moshkovskii using monoclonal antibody-based sandwich enzyme-linked immunosorbent assay (ELISA).

Results : The developed ELISA could detect as low as 210 and 810 cells of E. histolytica, and 530 and 750 cells of E. moshkovskii in unpreserved and formalin-fixed stool samples, respectively. Validated using field-collected samples, compared to PCR and the commercially available ELISA kit, the sensitivity, specificity, and accuracy of the developed test for E. histolytica were 100% and 82.2%, and 83.3, while that of E. moshkovskii were 100%, 89.1%, and 89.6%, respectively. ROC analysis showed high level of agreement between the developed ELISA platform and the commercial kit.

Conclusion : In summary, this study successfully developed a sensitive and specific immunodiagnostic platform to differentiate E. histolytica and E. moshkovskii, that is compatible for both unpreserved and preserved stool samples. The newly developed platform will contribute to accurate diagnosis and the true epidemiological picture for more effective disease control in the future.

[IC20-00084]
Abstract :

Introduction : Leptospirosis imposes a significant burden worldwide including Thailand. Mechanism of pathogenesis in particular identification of virulence factors are needed for developing leptospirosis control strategy. This research aims to identify secreted proteins of pathogenic Leptospira spp. under stress/nutrient deprivation and renal proximal tubular environment.

Methods : Leptospira secretomes were prepared in a 0.1% glucose, bicarbonate-acetate solution containing physiologic Na2+, K+, Ca2+, Mg2+, Cl-, HCO3-, and acetate at 37°C and in a humidified 37°C, 5%CO2 for 24 hours. The secretomes supernatant were verified for virulence and immunogenicity. Secretion proteins in response to nutrients deprivation, osmolarity upshifts, and salt-, and temperature stresses were identified by using LC–MS/MS system. Omics data and bioinformatic tools were integrated to interpret the protein secretion under leptospirinuria mimicking condition.

Results : The culture supernatant of a virulent serovar Autumnalis exhibited hemolytic activity, adhesion and cytotoxic activities to cell-lines. We identified 1) proteins in response of hyperosmotic and heat stresses in acid-base condition include transcriptional regulatory proteins family such as ArcC, TetR, SigB, FecR/PupR; chaperone and heat stress response (clpB, ahpC, dnaK, greE groeL); oxidative defense such as redoxin, cytochrome C, peroxidoxin, 2) multi-functional proteins involved in membrane biogenesis and signaling such as TonB-dependent receptor, ompA porin, heavy metal efflux pump, LipL45, LipL71, 3) degradation enzymes include proteases, hydrolases, endonuclease and moonlighting proteins, 4) oligopeptides found in serovar Autumnalis at osmolarity and 37°C upshifts include LA1686, DUF326, EPG82264.1, EMJ96087, EPG82264.1, EMJ97633.1, and other proteins.

Conclusion : This study provides dataset of pathogenic L. interrogans secretion proteins contributed to phenotypic leptospirinuric phase.

[IC20-00157]
Abstract :

Introduction : Leptospirosis, caused by the bacteria Leptospira spp., is a global health threat, contributing to 60,000 deaths worldwide. The gold standard diagnosis of Leptospirosis is anti-Leptospira IgM detection by microscopic agglutination test (MAT). However, this platform has low accuracy and specificity and fails to differentiate Leptospira serovars. 7-KDa and 6.8-KDa proteins have been found specifically in pathogenic and intermediate Leptospira, respectively.

Methods : To develop a better Leptospirosis diagnosis, we successfully produced monoclonal antibodies (mAbs) specific to pathogenic and intermediate Leptospira using conventional hybridoma technology.

Results : A total of 15 clones of anti-Leptospira specific mAbs were obtained, including 9 clones of anti-6.8 kDa of intermediate Leptospira, one clone of anti-pathogenic Leptospira, 2 clones of mAbs differentiating pathogenic from intermediate Leptospira and 3 clones of pan-Leptospira mAbs. These mAbs showed lowest detecting capacity at 7,461 and 14,600 cells of pathogenic and intermediate Leptospira, respectively. The mAbs were capable to detect 7-kDa and 6.8-kDa proteins as low as 0.1 ng. The mAbs positively reacted with sera of Leptospirosis patients, indicating that the 7-kDa and 6.8-kDa proteins were released into the patient sera. In controversy to anti-Leptospira IgM, levels of the released 7-kDa and 6.8-kDa proteins detected during convalescence phase were higher than the acute phase.

Conclusion : In summary, we successfully produced highly specific and sensitive mAbs that were able to differentiate pathogenic Leptospira from intermediate Leptospira and quantify proteins specifically released by Leptospira from patient sera. Current findings underlined potential applications of these Leptospira-specific mAbs for development of Leptospira-specific immunodiagnostic tests and vaccine in the future.

[IC20-00155]
Abstract :

Introduction : Leishmania is a protozoa which causes leishmaniasis, especially in immunocompromised hosts. Three major species were reported in Thailand; L. siamensis, L. martiniquensis and L. donovani complex. This study aimed to identify associated factors of infection of these species in HIV patients.

Methods : A descriptive cross-sectional study was designed. Blood and saliva samples were collected from HIV patients at Trang Hospital, Thailand. PCR technique was used for DNA extraction. Positive results for L. siamensis, L. martiniquensis and L. donovani complex were noted. Questionnaire of associated factors were employed for interviewing patients with positive Leishmania DNA. Associated factors were analyzed by logistic regression with significant level at p ≤ 0.05 at 95% confidential interval (95%CI).

Results : 526 patients were recruited. 11.98% were positive for L. siamensis, 4.56% for L. martiniquensis and 4.37% for L. donovani complex. Associated factors of L. siamensis infection included injected drug (adjusted odds ratio (AOR) 2.01, 95%CI 1.01 – 4.02). Associated factors of L. martiniquensis infection included female gender (AOR 4.23, 95%CI 1.52 – 11.75), using recreational drug (AOR 3.43, 95%CI 1.00 – 11.74) and having comorbidities (AOR 4.94, 95%CI 2.00 – 12.21). Associated factors of L. donovani complex infection were having opportunistic infection (AOR 4.22, 95%CI 1.00 – 17.79), CD4 200 – 500 cells/mm3 (AOR 3.64, 95%CI 1.14 – 6.86) and not using insect repellent (AOR 3.04, 95%CI 1.08 – 8.58).

Conclusion : There were different associated factors of Leishmania infection in Thailand. The data could be useful for prevention and control. Further studies on prevention measures are recommended.

[IC20-00471]
Abstract :

Introduction : CChagas disease (CD) or Trypanosoma cruzi infection has expanded globally through human migration. In non-endemic areas, mother to child route is the main mode of transmission contributing to autochthonous CD, however the most people living in Spain acquired the infection in their country of origin being diagnosed in the chronic phase, imported chronic CD. In both situations, CD is silent, so confirmation of the diagnosis is based on laboratory tests. In this context, we aimed to evaluate microbiological surveillance as an indicator of congenital transmission control measures in non-endemic areas.

Methods : A review of the Chagas laboratory database of the National Centre for Microbiology, Instituto de Salud Carlos, Spain, was carried out from 1997 to 2021. Laboratory diagnosis of CD is based on microscopy and PCR in samples for diagnosis of acute phase, and on serological tests (ELISA with total antigens, ELISA with recombinant antigens and indirect immunofluorescence) in samples for diagnosis of chronic phase.

Results : .From 1997 to May 2021, 31,390 samples were analyzed for serology, 8,535 were positive. During the same period, 1,824 samples from children under one year of age, whose mothers were positive for CD, were analyzed by PCR. 52 children were confirmed with congenital infection, the overall congenital transmission rate was 2.9% (range 0 – 6.6%), with the highest number of cases detected in 2009 (n = 12).

Conclusion : .Microbiological data can help CD surveillance and thus allow evaluation of control measures for interruption of congenital transmission in non-endemic settings.

O4_R4: Schistosomiasis: vaccine targets, diagnostics and control
Chairperson: Poom Adisakwattana

[IC20-00109]
Abstract :

Introduction : Schistosomiasis (Schisto) is one of the most prevalent parasitic diseases worldwide. Although >700 million people are at risk of infection and causes debilitating illnesses which can last over 30 years, such as diarrhea, blood in the stool, and in some cases bladder cancer. This project tested the protective ability of Schistosoma mansoni cathepsin B when delivered by a genetically engineered human Adenovirus serotype 5 as a vector.

Methods : Protection from infection through this vaccine was tested in a mouse model. Elicited antibody responses after immunization was assessed by ELISA assays, and splenocytes were stimulated ex vivo with antigen and were evaluated for cytokine expression using flow cytometry, and multiplex ELISA. Adult worm burden, and egg deposition in the liver and intestines were assessed after challenge.

Results : Robust humoral responses in antigen specific IgG1 and IgG2c was observed. Flow cytometry analysis of splenocytes displayed increase expression of IFNy, IL2, and TNFa from CD4+ and CD8+ T cells. Multiplex ELISA assessed on splenocyte supernatants showed increase expression of Th1 cytokines when compared to the PBS control. Immunized mice were challenged, and our vaccine delivered parasite burden reductions of 83.1%, 84.4%, and 91.8% in adult worm burden, hepatic, and intestinal egg burdens respectively, when compared to the PBS control.

Conclusion : Our recombinant Adenovirus vaccine delivers schistosomiasis protection far superior to the WHO standard of 40% parasite burden reduction. Not only would an effective vaccine for schisto benefit populations in endemic regions aiding interruption of disease transmission but it would also benefit travelers to tropical regions.

[IC20-00080]
Abstract :

Introduction : With >250 million people infected worldwide and approximately 800 million people at risk, the World Health Organization considers schistosomiasis to be the most important human helminth infection. Several prophylactic non-living vaccines are in pre-clinical and clinical development, but only one has been assessed for therapeutic effect in an animal model with modest results. We have repurposed an attenuated Salmonella enterica Typhimurium strain (YS1646) to produce such a vaccine that targets Cathepsin B (CatB), a digestive enzyme important for parasite survival.

Methods : Female C57BL/6 mice were infected with 150 S. mansoni cercariae. Once infection was well-established, mice were immunized at either two or four months post-infection. A multi-modality immunization schedule was used that included three oral (PO) doses of CatB-bearing YS1646 on days one, three, and five as well as an intramuscular (IM) dose of recombinant CatB on day one. Mice were sacrificed at intervals post-vaccination to assess adult worm and egg burden (liver and intestinal tissue) that were expressed relative to the saline control group numbers.

Results : Compared to the mock-vaccinated animals, all parasitological outcomes were 40–50% reduced at 4 weeks post-vaccination with further reductions (approximately 55 – 70%) at 8 weeks post-vaccination. Both relative and absolute reductions in worm numbers and hepatic/intestinal egg burdens continued to increase over time as mice were sacrificed 12, 16, and 24 weeks post-vaccination.

Conclusion : Current treatment consists of a single worm-targeting drug (ie: praziquantel). A vaccine that has both prophylactic and therapeutic activity would be ideal for use in conjunction with mass treatment campaigns with praziquantel.

[IC20-00355]
Abstract :

Introduction : Asian zoonotic schistosomiasis caused by blood fluke Schistosoma mekongi is endemic in Cambodia and Lao People’s Democratic Republic (Lao PDR). Development of an appropriate diagnostic method is necessary for effective treatment and accurate prevalence survey. To date, no defined antigen has been assessed for the diagnosis of S. mekongi infection due to the lack of genome information of this parasite species. Our previous study that evaluated S. japonicum thioredoxin peroxidase-1 (TPx-1) for schistosomiasis mekongi diagnosis using ELISA showed an unsatisfactory result with 71.4% sensitivity and 74.2% specificity. In this study, we expressed and evaluated S. mekongi TPx-1 for the diagnosis of human schistosomiasis by ELISA. DNA sequence of the gene coding for SmTPx-1 was obtained from the ongoing S. mekongi genome project in our laboratory.

Methods : Recombinant S. mekongi TPx-1 (rSmTPx-1) was cloned, expressed, and evaluated using ELISA. The utility of rSmTPx-1 as a detection antigen was evaluated with a panel of serum samples from endemic foci in Cambodia, which included 28 schistosomiasis-positive and 30 schistosomiasis-negative serum samples confirmed with Kato-Katz technique. In addition, 29 non-endemic negative serum samples from US volunteers were also used to calculate cut-off values.

Results : The rSmTPx-1 was successfully cloned, expressed and evaluated for the ELISA as antigen. The results showed that the rSmTPx-1 antigen demonstrated 89.3% sensitivity and 93.3% specificity in the ELISA.

Conclusion : The result suggests that the rSmTPx-1 antigen-based ELISA can be a potential diagnostic method for human S. mekongi infection in regions where the disease is endemic.

O5_R5: Towards elimination of helminthiases
Chairperson: Paron Dekumyoy

[IC20-00113]
Abstract :

Introduction : Conventional oral therapy of lymphatic filariasis drugs is only effective to kill microfilariae in the bloodstream, but is ineffective to kill macrofilariae in the lymphatics. The intradermal administration of lipid-based nanoparticles with sizes of <100 nm could be used to improve lymphatic uptake. Herein, we developed a novel approach, utilising solid lipid nanoparticles (SLNs) and microneedles (MNs) to deliver antifilariasis drugs, namely doxycycline, diethylcarbamazine and albendazole, intradermally.

Methods : The SLNs were fabricated from Geleol® and Tween®80 as a lipid and stabilizer, respectively. The SLNs were then incorporated into a polymeric hydrogel which was casted to form SLNs-loaded MNs.

Results : The formulations were <100 nm in size. Drug release was sustained over 48 h from SLNs, compared to pure drugs. SLNs-loaded MNs demonstrated satisfactory mechanical and insertion properties. Essentially, dermatokinetic studies exhibited that >40% of drugs were retained in the dermis of excised neonatal porcine skin up to 24 h post-MN administration, representing the high possibility of the SLNs to be taken by the lymphatics. In in vivo studies, the lymph concentrations of the three drugs, achieved after MN administration, ranged between 4- and 7-fold higher than that obtained following oral administration. Furthermore, compared to oral administration, the relative bioavailability of the three drugs in rat plasma was also higher using this delivery approach.

Conclusion : Therefore, this could potentially deliver the drugs effectively to the bloodstream, where the microfilariae reside, while also targeting drug to the lymphatics, where filarial nematodes reside in infected patients, resulting in an effective therapy for lymphatic filariasis.

[IC20-00135]
Abstract :

Introduction : Nepal has made substantial progress in the elimination of lymphatic filariasis (LF). Potential movement of Wuchereria bancrofti strains across Nepal-India borders might pose a challenge to elimination programs. This study attempted to address the lack of genetic information of circulating strains required to understand parasite movements and genetic variability.

Methods : W. bancrofti was recovered from blood samples of microfilaraemic individuals from LF endemic districts of Nepal. W. bancrofti abundant larval transcript (alt-2) fragment and internal transcribed spacer (its) region of 18S ribosomal DNA were PCR-amplified from gDNA and sequenced. The resulting sequences were analyzed for polymorphism in the 29 bp Short Tandem Repeats (STR) in intron-1 of alt-2 gene and haplotype mapping of the its region. Phylogenetic trees were constructed for evolutionary relationships of strains.

Results : Over hundred polymorphic sites were recognized in the its sequence (58 in Nepal alone) indicating strain variation. STR analysis of alt-2 revealed two distinct polymorphism patterns in Nepal and India. Parasite strains were largely mixed up within Nepal (different regions) and also between two countries as evidenced by phylogenetic trees of its and alt-2 sequences suggesting potential movement of parasites. Alt-2 phylogenetics showed three distinct lineages/clades of W. bancrofti in Nepal. Such genetic comparisons were lacking from Nepal.

Conclusion : To conclude, W. bancrofti strains circulating between Nepal and India are closely related with potential cross-border parasite movement. This information has important implications in LF elimination since they share open border. Therefore, monitoring by molecular tools should be considered in countries embarking LF elimination.

[IC20-00524]
Abstract :

Introduction : AWZ1066S is an azaquinazoline class of drug with superior Wolbachia killing kinetics compared with tetracyclines and has high selectivity against Wolbachia, with no general broad-spectrum antibiotic activities.

Methods : Rodent adult filarial infection models of Brugia malayi (SCID mouse), Brugia pahangi, Litomosoides sigmodontis (both gerbil), Onchocerca ochengi (SCID mouse) and a microfilariaemic SCID mouse model of Loa loa were used, as described previously. AWZ1066S was orally administered at doses between 50-300 mg/kg, bis in die (b.i.d.) for intervals between 3-7 days (n=5-7/group). Wolbachia were quantified by qPCR. Fluorescent in-situ hybridisation (FISH) was used to visualise and quantify Wolbachia depletion in different nematode tissues (n=3).

Results : 150mg/kg b.i.d. AWZ1066S dosing resulted in 98.3% median Wolbachia depletion in B. malayi female worms in as little as 4 days treatment with 100% microfilariae clearance. Drug treatment led to widespread degradation of developing embryos in uterine tissues with pyknotic nuclei and complete sterility. FISH analysis determined the Wolbachia population in ovaries are more sensitive to AWZ1066S treatment compared to the hypodermal chord population. AWZ1066S treatments of 7 days or less resulted in >99% median Wolbachia depletions in O. ochengi, B. pahangi and L. sigmodontis, with long-term sterility up to 17 weeks post-treatment observable. The selectivity for Wolbachia was confirmed with negligible activity against circulating microfilariae of the Wolbachia-free filaria Loa loa in mice.

Conclusion : <7-day courses of oral administered AWZ1066S causes >90% depletions of Wolbachia from filarial tissues predictive of eventual cure and mediates permanent sterility in adult filariae via blockade of embryogenesis and induction of apoptosis.

[IC20-00434]
Abstract :

Introduction : Wolbachia is a diverse obligate intracellular bacterium that infects a range of arthropod and parasitic nematodes. Within parasitic nematodes, such as Brugia malayi, they act as essential endosymbionts that play roles in reproduction, development and survival, making them a validated target for macrofilaricidal therapy. However, juvenile nematodes (microfilariae) suffer no overt impacts upon Wolbachia depletion, and persist for several months in circulation, potentially remaining transmissible. Our work shows that despite their persistence, Wolbachia-depleted Brugia malayi microfilariae lose their ability to develop within the mosquito vector, and thus cannot be transmitted.

Methods : Wolbachia-depleted or undepleted microfilariae were fed to Aedes aegypti mosquitoes, with infective-stage nematodes (L3s) counted after two weeks. Transcriptomics and immunoblotting experiments on the microfilariae were also performed to identify causes of any biological differences observed.

Results : Wolbachia-depleted microfilariae showed a marked decrease in ability to develop to the L3 stage compared to controls, with this phenotype consistently observed after multiple repeat experiments. Further work pinpointed the cause to be reduced transcription-translation of the microfilariae-specific chitinase enzyme, resulting in defects in exsheathment and an inability to migrate through the mosquito gut wall.

Conclusion : These observations have significant implications for existing models towards the elimination of lymphatic filariasis as a public health issue. This effect is unlikely to be limited to Brugia malayi, as previous studies that deplete Wolbachia from other parasitic nematodes have also observed defects in development within the vector or in the final host. These observations highlight the use of anti-Wolbachia therapy as both a macrofilaricidal and in transmission blocking.

[IC20-00485]
Abstract :

Introduction : Strongyloidiasis is a helminthic disease highly prevalent in tropical and subtropical regions which is often missed in the absence of effective surveillance. This infection coexists with Chagas Disease (CD) in endemic areas, both of them considered Neglected Tropical Diseases according to WHO. Different studies have shown an association between CD and Strongyloides stercoralis infection. This study pretends to evaluate the prevalence of strongyloidiasis in CD patients in order to implement a systematic program of screening in Primary Care.

Methods : Prospective study conducted at Laboratori Clinic Territorial Metropolitana Sud/Microbiology Department of Bellvitge University Hospital from June 2018-May 2022, in patients that attend Primary Care centers in the Southern Metropolitan area of Barcelona. Detection of Trypanosoma cruzi antibodies was made using two tests (LIAISON®XL MUREX Chagas and Ortho®T.cruzi Elisa). If both tests were positive, CD was diagnosed, and Anti-Strongyloides ELISA IgG (Euroimmun AG, Lbeck®) was performed in the same sample.

Results : Out of 189 patients diagnosed with CD, 77.2% were women, with a median age of 39 (IQR 34-47). Of those, 37 (19.57%) had a positive serology for S. stercoralis, being 75.7% men. All the cases were adults with a median age of 40 (IQR 37-49). The country of origin was: Bolivia (83.8%), Paraguay (2.7%), Salvador (2.7%), Honduras (2.7%). In 8.1% of the cases the country of origin was not recovered.

Conclusion : A systematic program of screening of strongyloidiasis in CD patients should be implemented in Primary Care, due to the high prevalence of coinfection (around 20%).

[IC20-00341]
Abstract :

Introduction : Myanmar is geared to achieve Lymphatic Filariasis elimination by 2030. Of 45 endemic districts, 32 districts were still endemic in 2019. This study aimed to access the factors influencing the coverage and compliance of MDA in the LF persistent transmission townships in Myanmar after a community-based intervention trial.

Methods : The community-based intervention trial to improve MDA coverage and compliance was conducted in two persistent transmission townships (Pakokku and Myaing), Magwe Region, Myanmar. A cross-sectional mixed-method approach was employed within one week after the MDA in 2020. A survey of 2,176 respondents (520 households) and 28 qualitative interviews with different stakeholders were conducted. Observed coverage and compliance, and factors influencing were identified through logistic regression.

Results : Of 2,090 eligible participants, the mean age was 34 years with 54% females. The observed coverage was 96% (95% in Township A and 97% in Township B). The observed compliance was 86% (84% in Township A and 88% in Township B). Only 28% adhered to the direct observed treatment (DOT). Younger age (6-14 years) received higher coverage (OR=2.9, 95% CI=1.0-8.45). Community from Township A (OR=1.39, 95% CI=1.04-1.85) achieved higher compliance than Township B. Qualitative findings supported stakeholder engagement with proper administrative support, systematic formation and training to CDA and implementing DOT were crucial for the success of MDA.

Conclusion : In conclusion, the coverage and compliance of MDA were high but adherence to DOT was still low. This study recommends the expansion of this community-based intervention trial which can ensure the WHO-recommended MDA coverage.

O6_R6: Malaria pathogenesis and host immune response
Chairperson: Parnpen Viriyavejakul