PROJECT SUMMARY The recent outbreak of Zika virus (ZIKV), a mosquito-borne flavivirus, in the western hemisphere resulted in a serious public health threat, in particular for pregnant women due to the subsequent Congenital Zika Syndrome which can manifest in infected fetuses. The placenta plays a central role in fetal susceptibility to maternal viral infections yet the timing of, and the mechanisms contributing to, placental injury following ZIKV infection are unknown. We have utilized a nonhuman primate (NHP) model of ZIKV infection during pregnancy to demonstrate functional abnormalities in placental oxygen transport, which likely constrain normal fetal organ development and predispose to growth abnormalities. Decreased oxygen permeability of the placental villi appears to be a consequence of uterine vasculitis, stromal cell death and placental villous damage. Despite a robust inflammatory response following ZIKV infection in both early and late gestation, we have shown that ZIKV persists for weeks to months in maternal-placental-fetal tissues, which highlights the need to investigate preventative strategies that can be employed during pregnancy. Vaccination is an efficient and tractable strategy for combating viral pathogens. The clinical restrictions imposed during pregnancy make the safest vaccine platforms utilizing antigens, which include virus-like particles (VLP), a high value target for development. We have recently generated a VLP-based vaccine against ZIKV by purifying VLP secreted by cells expressing the ZIKV prM-E polyprotein. Uterine and placental macrophages play a key role in maintaining normal pregnancy and have been shown to be susceptible to productive infection by ZIKV in cell culture systems. Moreover, in our NHP model we demonstrated changes in placental macrophage phenotype following ZIKV infection. We hypothesize that ZIKV targets placental macrophages, causes acute direct (viral) and indirect (immunopathological) damage to the placenta during development, which activates cellular components responsible for wound healing and may cause oxidative damage within the placental villous. These induced changes result in placental vascular adaptations, and tissue injury which impairs transport and detrimentally impacts fetal growth and development. The objective of this proposal is to temporally characterize the progression of ZIKV-mediated changes in placental function and tissue damage. Our longitudinal approach will facilitate characterization of disease pathogenesis in both the placenta and fetus by combining advanced functional imaging with temporal profiling of the fetal immune response, tissue transcriptomics following infection, and implementation of a novel vaccine to determine whether vaccination can mitigate placental and fetal injury.