PROJECT SUMMARY Zika virus, an emerging flavivirus, is associated with severe clinical outcomes, including Guillain-Barré syndrome and birth defects. Transmission of Zika virus is primarily mosquito- borne. Mosquito salivary proteins are known to enhance infectivity and pathogenesis in Zika, dengue and West Nile viruses by modulating immune responses. This proposal seeks to develop a novel vaccine against Zika virus by targeting Aedes aegypti salivary gland proteins important for Zika virus transmission from the mosquito vector to the mammalian host. Since we know that an antibody response towards certain, undescribed salivary gland proteins can change flavivirus pathogenesis, we focused on antigenic salivary proteins that elicit antibody responses in the vertebrate host. Using a yeast surface display screen, we identified 5 Ae. aegypti salivary proteins that react with sera from mice repeatedly bitten by this species of mosquito. Passive immunization with antiserum against one of these proteins, AAEL001965, which is also named Ae. aegypti bacteria-responsive protein 1 (AgBR1) resulted in significantly more survival in mice infected with Zika virus by mosquito bite. In this proposal, we intend to carefully examine the protective effects of blocking the mosquito AgBR1 protein in preventing severe mosquito-borne Zika virus infection in mice and develop a strategy for actively immunizing mice against this protein towards the development of a vaccine for use in humans. The success of this approach also offers a functional paradigm for developing vaccines against other flavivirus and other arthropod-borne pathogens of medical importance. These studies to define a vaccine to prevent Zika virus will be structured into the following specific aims