Zika virus (ZIKV) illustrates the importance of flaviviruses as emerging vector-borne human pathogens. The major concern is the association between ZIKV infection and neurological disorders, such as congenital microcephaly and Guillain-Barré syndrome. At the cellular level, a way to enhance antiviral defense is the production of type I interferons (IFN I). When a cell is infected with a virus, intracellular receptors can sense microbial components and induce the expression of IFN I. However, flaviviruses use non-structural proteins to hinder this response. In our lab, we study the role of one non-structural protein, ZIKV NS4b, in the inhibition of IFN I production. Considering that our lab has already successfully expressed N-terminal region of ZIKV NS4b in a prokaryotic system, the specific aim of this proposal is 1) to study the structure of ZIKV NS4b and 2) analyze its interaction with other proteins exploiting different strategies. Specifically, we propose to study the interaction between ZIKV NS4b and TBK1, as well as ZIKV NS4b and STING. Both TBK1 and STING are key proteins involved in the sensing cascade. To accomplish these goals, we will perform: protein crystallization trials to study the protein structure, surface plasmon resonance assays to study biophysical interactions and bimolecular fluorescence complementation assay to visualize protein-protein interaction in cells. At present, there is no approved vaccine or treatment against ZIKV infection. Therefore, a better understanding of molecular interactions is needed. Extending the knowledge of ZIKV NS4b protein structure and the interaction with host proteins is the first step for rational drug design.