Research Programs

 

 

 

 

 

 

 

 

 

 

 

 

 

Flaviviruses

Program Leader: Aravinda deSilva

 

Project: Antibody in protective and pathogenic immunity to Dengue type 3

Aravinda deSilva and Ralph Baric

University of North Carolina

Dengue viruses (DENV) are emerging, mosquito-borne Flaviviruses and the agents of dengue fever (DF) and dengue hemorrhagic fever (DHF). The NIAID has listed dengue (DEN) as a category A priority agent with respect to Biodefense and Emerging Infections research. A large body of work has demonstrated that people infected with DENV develop long-term protective immunity to the infecting serotype but not to other serotypes. During a second infection with a different serotype, the risk of severe disease is greater because cross-reactive immunity can exacerbate the disease. Efforts to develop DEN vaccines have been hampered by the dual role of immunity in protection and pathogenesis. We know very little about the antibody repertoire in people who have been infected with dengue. The main goal of this project is to use DENV3 as a model for defining the viral epitopes engaged by human antibody and to determine the functional outcome of these interactions. Our overall hypothesis is that a neutralizing antibody response is directed towards type-specific epitopes on domain III of E protein, whereas a non-neutralizing and potentially pathogenic antibody response is directed towards cross-reactive epitopes on domains I and II of E protein. In aim 1 studies will be done to produce human monoclonal antibodies from people who have recovered from DENV infections. In aim 2 a selected subset of human MAbs will be mapped to specific epitopes and functionally characterized for neutralizing or enhancing activity using cell culture and an animal model. The current dogma is that the main type-specific neutralization epitopes are conserved within each serotype. Our preliminary studies indicate that surface exposed regions on E protein of DENV3 are highly variable between strains. In aim 3 we will determine if the main antibody epitopes are conserved among DENV3 strains. This project takes advantage of a panel of reagents including well characterized virus strains, human samples and a DENV3 infectious clone available at UNC. The project also utilizes antibody and protein cores available within SERCEB as well as a new rodent model of DENV developed by a SERCEB investigator. The study is expected to reveal mechanisms of antibody mediated neutralization or enhancement of DENV3. This information is directly applicable to the evaluation of the safety and efficacy of candidate dengue vaccines.

Project: T cell response to Dengue virus serotype 3 in mice and human

Sujan Shresta

LaJolla Institute of Allergy and Infectious Disease

The four serotypes of Dengue virus (DENV) cause dengue fever (DF) and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) in humans. Studies suggest that DHF/DSS is an immunopathogenic disease in which T cell responses may be dysregulated. Understanding the mechanisms that regulate the balance between T cell mediated pathology versus protection is crucial for developing therapies and, importantly, a safe dengue vaccine. By alternately passaging a DENV between mice and mosquito cells, we have naturally selected for strains that induce robust T cell responses in mice, and we have demonstrated a critical role for CD8+ T cells in limiting DENV infection in mice. Due to the broad specificity and antiviral role of the CD8+ T cell response to DENV2 in mice, we hypothesize that the murine and human CD8+ T cell response to DENV3 is broad, targeting most viral proteins, and these CD8+ T cells protect against DENV3 infection in the host. Specifically, we will examine the contribution of CD8+ T cells to protection versus pathogenesis using a mouse model of DENV3 infection (Aims 1 and 2), and we will define the specificity and role of human CD8+ T cell response in the host response to DENV3 infection using HLA transgenic mice and samples derived from people who have recovered from primary DENV3 infection (Aims 3 and 4). This project focuses on DENV3 because epidemiologic studies suggest that certain DENV serotypes, genotypes, and the sequence of DENV infections may be associated with DHF/DSS, and little is known about DENV3 infection as compared with DENV2, although DENV3 co‐circulates with DENV2 in endemic countries, and DENV3 has been responsible for recent epidemics in South Asia and Latin America.