Author Interviews, Dengue, PLoS, Zika / 04.02.2021 Interview with: Gregor J. Devine, Ph.D Mosquito Control LaboratoryQIMR Berghofer Medical Research Institute Brisbane, Queensland, Australia What is the background for this study? Scale of the problem: Dengue, Zika and chikungunya are all transmitted by the same mosquito species.  That mosquito, Aedes aegypti, is superbly adapted to the human, urban environment – it lays its eggs and develops in the standing water that collects in the myriad containers associated with modern living (plastic bottles, food packaging, buckets, planters, crumpled tarpaulins etc.). Unusually they rely almost entirely on human blood for their nutritional requirements and they subsequently bite multiple times during each egg laying cycle. That reliance on human blood means that they are usually found resting indoors, a behaviour that also offers them some protection from weather extremes and predators. Once infected, and having incubated the virus until it is transmissible, a mosquito that survives for just a couple of weeks can infect many humans within the same and neighbouring households. In poorer tropical urban environments with dense human populations, unscreened houses, no air-conditioning, and innumerable rain-filled containers to develop in, Aedes aegypti proliferates and so do those diseases, causing ca 400M annual infections of dengue alone by some estimates. The economic impact of the dengue, which normally causes a high fever, muscle and joint pains and nausea, is pronounced; especially in poor households with few savings and no welfare system. Every year, about 500,000 of those dengue cases develop into severe dengue, or dengue haemorrhagic fever (typified by plasma leakage, severe bleeding and organ impairment). There are about 25,000 deaths annually. mosquito-Aedes aegypti-feeding-human.jpgThe Zika pandemic of 2015-2016 resulted in 1000s of babies born with microcephaly and damage to their brains and eyes. For 1000s of other children, the impacts of Zika on their cognitive development did not manifest in their first, formative years.  Chikungunya is endemic in Asia and Africa but between 2010 and 2014, outbreaks and epidemics spread across the Indian Ocean, the Caribbean, the Americas and the Pacific Islands. It causes severe, often debilitating joint pain in infected patients. Those affected also suffer from headaches, fever, severe muscle pain and conjunctivitis. Joint pain can persist in subacute or chronic form for several months or even years, particularly in older patients. The ubiquity of the mosquito Aedes aegypti across the tropics and sub tropics ensures that further epidemics of Zika and chikungunya will occur, outside their usual ranges. It’s simply impossible to predict when that will occur. (more…)
Author Interviews, Dengue, Duke, Vaccine Studies / 21.09.2019 Interview with: Dr Shee-Mei Lok, PhD Professor in the Emerging Infectious Disease program Duke-NUS, a school of National University of Singapore What is the background for this study? Response: Dengue virus consists of four different serotypes (DENV1-4) and within each serotypes, there are multiple strains. In terms of the viral particle shape, our previous research work using some laboratory adapted strains showed these DENV2 strains are very interesting in that it can change shape from the smooth spherical surface particles when grown at mosquito physiological temperature (29oC) and then becomes bumpy surfaced particles when incubated at human physiological temperature (37oC). This ability to transform into different virus surface structures helps the virus to escape from the immune system of the human host. Hence understanding the mechanism of how this occur is important for therapeutics and vaccine development. Here we also identified a laboratory adapted virus strain that do not showed this structural changes. We showed some differences in their amino acid sequences and We showed some differences in their amino acid sequences and mutating these residues coupled with observing their surface structures showed which residues are important for this temperature induced structural change. Results showed that subtle mutations at different places on the envelope protein can destabilize the virus allowing them to change in structure when temperature is elevated. Due to the poor selection pressure of the artificial laboratory tissue culture system, gradual mutations of the virus is accumulated causing the virus to have bumpy surface morphology. (more…)
Author Interviews, Dengue, Genetic Research, PLoS / 16.02.2018 Interview with: Luisa Pereira PhD Institute for Research and Innovation in Health University of Porto What is the background for this study? What are the main findings? Response: By using admixture mapping along the genome in Thai cohorts, we were able to identify new candidate genes conferring protection/susceptibility to dengue fever. A very interesting result was that the set of genes differed with the dengue phenotype: genes coding proteins that may link to the virus, conditioning its entrance in the host cells and mobility therein were associated with the less severe phenotype; genes related with blood vessels permeability were associated with the dengue shock syndrome.  (more…)
Author Interviews, Dengue, Lancet, Vaccine Studies / 29.11.2017 Interview with: Vianney Tricou DPhil Takeda Vaccines Pte Ltd Singapore What is the background for this study? What are the main findings? Response: Dengue fever is a painful, debilitating mosquito-borne disease caused by any one of the four closely related dengue virus serotypes. Forty percent of the world’s population lives under the threat of dengue, with approximately 390 million infections and 20,000 deaths occurring globally each year. Dengue virus can infect people of all ages and is a leading cause of serious illness among children in some countries in Latin America and Asia. Takeda is developing a dengue vaccine candidate to safely protect children and adults living in, or traveling to, endemic areas against all four dengue virus serotypes, regardless of previous dengue virus exposure.  Takeda’s tetravalent dengue vaccine candidate (TAK-003) is based on a live, attenuated dengue serotype 2 virus, which provides the genetic ‘backbone’ for all four vaccine viruses. Takeda’s ongoing Phase 2 DEN-204 study was designed to assess the safety and immunogenicity of different dose schedules of TAK-003 in approximately 1,800 healthy children and adolescents ages two through 17 years living in dengue-endemic countries in Latin America and Asia. Participants of the DEN-204 trial received either one primary dose of TAK-003, two primary doses of TAK-003 administered three months apart, one primary dose of TAK-003 followed by a booster dose one year later, or a placebo. Eighteen-month interim data showed that that TAK-003 is associated with a reduction in the incidence of dengue in the study participants. Data also showed that TAK-003 induced sustained antibody responses against all four serotypes of dengue virus, regardless of previous dengue exposure and dosing schedule. (more…)
Author Interviews, Dengue, Vaccine Studies / 04.05.2017 Interview with: Dr Vianney Tricou DPhil Takeda Vaccines Singapore What is the background for this study? What are the main findings? Response: Dengue fever is a painful, debilitating mosquito-borne disease caused by any one of four closely related dengue virus serotypes, and persons living in dengue endemic regions may be affected by dengue more than once in their lifetime. Some individuals with dengue fever are hospitalized and may need intensive therapy to prevent shock and death, and severe dengue is a leading cause of hospitalization and death among children and adults in some Asian and Latin American countries. About half of the world’s population lives under the threat of dengue and the disease has a significant medical and economic impact in the tropical and subtropical regions of the world where dengue is endemic. Takeda is committed to improving global public health and to developing a life-saving dengue vaccine candidate for people around the world. Takeda’s tetravalent dengue vaccine candidate (TAK-003) is based on a live-attenuated dengue serotype 2 virus (DENV-2), which provides the genetic ‘backbone’ for all four attenuated dengue virus serotypes present in the vaccine. Takeda’s Phase 1 and Phase 2 clinical study program includes 8 studies to date that assess the safety and/or immunogenicity of this candidate, before moving into Phase 3. Takeda’s ongoing Phase 2 DEN-204 study is designed to assess the safety and immunogenicity of one- and two-dose schedules of TAK-003 in 1,794 healthy children and adolescents ages two through 17 years living in dengue-endemic countries in Latin America and Asia. As published in The Lancet Infectious Diseases in March 2017, an interim analysis of DEN-204 data indicated that TAK-003 elicited antibody responses to all four dengue serotypes in the population studied, regardless of whether they had previous dengue exposure. A second TDV dose improved antibody responses against DENV-3 and DENV-4 in children who were seronegative before vaccination. In this study, the safety profile was consistent with that observed in earlier Phase 1 and 2 studies. (more…)
Author Interviews, Dengue, Lancet, OBGYNE / 07.03.2016 Interview with: Mrs Enny S Paixão London School of Hygiene & Tropical Medicine London UK What is the background for this study? What are the main findings? Response: Dengue is a vector borne disease endemic in more than 100 countries (mainly in South America and southeast Asia) and is spreading to new areas, with outbreaks of increasing magnitude and severity. It is estimated that each year, 390 million people are infected with dengue and 96 million develop clinical symptoms. Despite of the importance of this disease, the effects of disease during pregnancy on fetal outcomes remain unclear. Using the published scientific literature, we investigated the risk of stillbirth, miscarriage, preterm birth, and low birth weight for women who had dengue infection during pregnancy. This study showed some evidence that dengue infection alone, in the absence of clinical symptoms, does not affect the outcome of pregnancy, but also that clinical dengue during pregnancy seems to increase the frequency of stillbirth, prematurity, and low birthweight. (more…)
Author Interviews, Dengue, Zika / 25.02.2016 Interview with: Prof Paul Dyson Institute of Life Science Swansea University Medical School Singleton Park Swansea UK Medical Research: What is the background for this study? What are the main findings? Prof. Dyson: The spread of insect-vectored viruses such as Dengue and, more recently, Zika, underline the urgent necessity to develop new technologies to control insect disease vectors that, due to human activity, are spreading globally. The concept of using RNAi in insects is not new and is widely used as a research tool in the model organism Drosophila melanogaster. However, adapting RNAi for use in non-model insects has been slow, almost entirely due to the problem of delivering interfering RNA to the insect. Manual injection is a less than optimal means of delivery for larger insects, while including interfering RNA in a food source can be effective in smaller insects in the laboratory. But neither delivery system is suited for field applications of RNAi as a biocide. Faced with this challenge, we (myself and Dr Miranda Whitten) conceived the concept of symbiont-mediated RNAi and have advanced it with support from the UK BBSRC and the Gates Foundation, establishing it as a viable mechanism of delivery of RNAi in (a) a tropical disease vector, Rhodnius prolixus, a vector of Chagas disease, exemplified by targeting insect fertility, and (b) a globally invasive vector of plant disease, Western Flower Thrips, targeting larval growth. Interfering RNA is actively produced by symbiotic insect bacteria that multiply within the host. Critical to the technology is to ensure the stability of RNA synthesis by these bacteria. The interfering RNA is then released by the bacteria, absorbed and systemically circulated within the host, thereby causing knock-down of gene expression in specific tissues. We have exploited this technology to severely impair fertility of Rhodnius prolixus, and to cause mortality of developing larvae of Western Flower Thrips. As a biocide, the technology offers exquisite specificity due to the co-evolution and co-dependencies of the symbiont and its insect host, combined with the sequence-specificity of the RNAi. Moreover, development of resistance is highly improbable. (more…)
Author Interviews, Dengue / 10.07.2015 Interview with: Dr. Eng Eong Ooi BMBS PhD FRCPath Associate Professor & Deputy Director Program in Emerging Infectious Diseases Duke-NUS Graduate Medical School Singapore Medical Research: What is the background for this study? What are the main findings? Response: Dengue prevention continues to rely exclusively on vector control guided by disease and virologic surveillance. The latter has focused on detecting changes in the prevalence of the four antigenically distinct viral serotypes as, in general terms, herd immunity depends on long-lived serotype-specific antibodies.  However, epidemiological observations have indicated that a small number of changes within the viral genome have also been associated with several major outbreaks, without any change in viral serotype.  Identifying the genetic changes that alter viral fitness epidemiologically would thus be important to differentiate strains that have a greater potential of causing epidemics and targeted for control. Using the 1994 outbreak in Puerto Rico as a case in point, we identified nucleotide substitutions in the 3’ untranslated region (3’UTR) of the viral genome as critical determinants of dengue virus’ epidemiological fitness.  Mechanistically, mutations in the 3’UTR altered secondary viral RNA structures and changed the relative proportion of genomic to subgenomic RNA of the virus in infected cells.  The epidemiologically fitter viruses produced larger amounts of subgenomic to genomic RNA.  This subgenomic RNA then binds a host protein, TRIM25, which is a E3 ubiquitin ligase that polyubiquitylates RIG-I to amplify and sustain signalling for type-I interferon expression.  By binding to TRIM25, the subgenomic RNA of dengue virus inhibits the activation and thus enzymatic function of TRIM25.  We suggest that with reduced interferon expression, the virus was thus able to spread more effectively from cell to cell within the infected individuals to reach viremia levels for further subsequent mosquito-borne transmission. (more…)
Author Interviews, Dengue, Technology / 31.01.2015 Interview with: Professor Jackie Ying Institute of Bioengineering and Nanotechnology The Nanos, Singapore Medical Research: What is the background for this study? What are the main findings? Response: The Institute of Bioengineering and Nanotechnology (IBN) has developed a paper-based disposable device that will allow dengue-specific antibodies to be detected easily from saliva within 20 minutes. Currently, dengue infection is diagnosed in the laboratory by testing the patient’s blood sample for the presence of dengue antigens or antibodies. IBN’s device, on the other hand, is capable of detecting IgG, a dengue-specific antibody found at the onset of secondary infections, directly from saliva in one step. Unlike blood samples, saliva can be collected easily and painlessly for rapid point-of-care diagnostics. However, unlike other body fluids, it cannot be applied directly to commercially available test kits as it would cause the sensor nanoparticles to stick haphazardly to the test strip. In addition, conventional paper-based tests are not designed to handle the larger sample volume of saliva required. As described in the journal Lab on a Chip, the IBN researchers used an innovative stacking flow design to overcome key challenges faced by existing lateral flow devices, which are not designed to handle large volume of saliva samples. In IBN’s device, different flow paths are created for samples and reagents through a multiple stacked system. This allows the saliva sample to flow separately through a fiber glass matrix, which removes the substances that would interfere with the nanoparticle-based sensing system before it mixes with the sensor nanoparticles. IBN’s device configuration also helps to regulate the flow in the test strip, generating uniform test lines for more accurate results. (more…)
Author Interviews, Dengue, Infections, PLoS / 16.01.2015 Interview with: Jose R. Loaiza Smithsonian Tropical Research Institute, Panama City, Panama, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología,  Universidad de Panamá, Ciudad de Panamá, Panamá   Medical Research: What is the background for this study? Response: The mosquito Aedes albopictus is a worldwide vector of both Dengue and Chikungunya viruses. This species invaded Panama in 2002, and it expanded across much of the country since that time. Our main goal was to determine the factors (e.g., ecological and non-ecological) associated with its expansion, and to comment on the implications for vector and disease control programs elsewhere in the American tropics. Medical Research: What are the main findings? Response: We found that road networks alone best predicted the distribution of Ae. albopictus in Panama over other variables such as population density and climate. Our data explain the invasion mode of this mosquito species on a local level and demonstrate a remarkable population expansion velocity across the country. Ae. albopictus is likely moving across the landscape as immature stages (i.e., larvae and pupae) in open water, such as used tires. (more…)
Author Interviews, Dengue, Infections, NEJM, Vaccine Studies / 13.01.2015

Gustavo Dayan, MD Director, Clinical Development Sanofi Pasteur  Discovery Drive Swiftwater, PA Interview with: Gustavo Dayan, MD Director, Clinical Development Sanofi Pasteur  Discovery Drive Swiftwater, PA 18370 Medical Research: What is the background for this study? What are the main findings? Dr. Dayan: This is the first dengue vaccine efficacy trial conducted in Latin America. The trial met its primary objective showing an efficacy of 60.8% against symptomatic VCD (virologically confirmed dengue) after a 3-dose vaccination schedule. Serotype-specific efficacy was also demonstrated against all four serotypes. Furthermore, the dengue vaccine candidate effectively reduced hospitalization due to dengue by 80.3% and severe dengue disease by 95.5% over the 25-month study period. (more…)