Despite being the most important mosquito-transmitted viral disease, there is currently no vaccine for dengue. There are four distinct serotypes of dengue virus (DENV) and cross reactive antibodies to one serotype can enhance infection of other serotypes into Fc receptor-bearing cells such as macrophages correlating with severe disease in humans. A safe and effective vaccine should induce strong, cross protective neutralizing antibodies against all four DENV serotypes, while minimizing non-neutralizing cross reactive antibodies that will only serve to enhance infection and disease severity. Therefore, an optimal vaccine should include only those antigenic regions that will induce strongly neutralizing antibodies and none of the antigenic regions that induce non-neutralizing antibodies. The central aim of this project is to investigate the hypothesis that a vaccine containing only those epitopes that will induce a strong, broadly neutralizing DENV antibody response will be safe and effective. To accomplish this central aim, this project proposes to shift the current paradigm of DENV vaccine research by using insights derived from the study of unique human monoclonal anti-DENV antibodies against the surface E protein to design, characterize, and test a chimeric vaccine in a mouse model. The first specific aim is to design flavivirus E protein chimeras containing DENV epitopes, and characterize their folding, assembly, and functionality. As our results with human MAbs indicate that the important neutralizing DENV epitopes are conformationally sensitive, a related flavivirus, yellow fever will be used as a scaffold for constructing the chimeras. We will introduce specific DENV epitopes into the yellow fever 17D vaccine strain E protein, generate chimeric E protein, virus- like particles, and infectious virus and determine whether these E protein chimeras are still recognized by our human anti-DENV monoclonal antibodies. The second specific aim is to evaluate the antigenicity of flavivirus E protein chimeras containing DENV epitopes in a mouse model and assay serum for the presence of binding, neutralizing, and enhancing anti-DENV antibodies in vitro. The third specific aim is to determine if flavivirus E protein chimeras containing DENV epitopes will produce a protective immunological response in a mouse DENV challenge model. Infectious challenge with DENV is proposed using a widely accepted murine model of DENV infection. Successful completion of the aims will create a DENV vaccine that will induce a broadly neutralizing antibody response, while minimizing the induction of a non-neutralizing, enhancing antibody response, minimizing the risk of more severe disease in vaccine recipients.
As there are none currently available, the development of a vaccine against dengue virus is a high priority. Since primary infection with any of the four dengue virus serotypes produces an antibody response that protects against re-infection with that same serotype, but can increase the disease severity of a secondary infection with one of the other serotypes, a safe and effective dengue vaccine will need to induce broad protection against all four dengue virus serotypes. Using insights derived from the study of unique human monoclonal antibodies, this project will design and characterize a vaccine that contains only those epitopes that induce a strong, broadly neutralizing dengue antibody response.
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