This contract supports the identification of human B cell epitopes derived from four viral pathogens; Dengue virus 4, Powassan virus, Chikungunya virus, and Venezuelan equine encephalitis virus, combined with basic studies to understand protective immunity mediated by antibodies, as well as pathological consequences of antibody responses. Milestones include 1) epitope identification; 2) epitope validation that must include in vitro evaluation using human samples; 3) submission of epitope data, computer software, and structural data to the Immune Epitope Database and Analysis Resource; and 4) studies to help understand the mechanisms of protection or pathogenesis elicited by antibodies associated with the newly identified epitopes. The primary goal of this contract is the delineation of B cell epitopes recognized by potently neutralizing or protective antibodies and evaluation of correlates of protection that can aid in the development of vaccines and therapeutics against select arthropod-transmitted viruses. The Contractor has chosen two flaviviruses (Dengue virus 4 and Powassan virus) and two alphaviruses (Chikungunya virus and Venezuelan equine encephalitis) for primary investigation of antibody responses to viral glycoprotein antigens. The Contractor will also evaluate protective antibodies that recognize the flavivirus nonstructural protein 1 (NS1) produced by West Nile and Zika viruses.