Identifying placental tissue tropism and cellular mechanisms of Ebola Virus transmission from mother to fetus in pregnancy - Project Abstract Maternal viral infections during pregnancy may result in catastrophic outcomes for her health as well as for her developing fetus. Recent emerging virus epidemics and pandemics such as those with Ebola Virus (EBOV), Zika Virus (ZIKV) and SARS-CoV-2 have highlighted the impact of viral infection on pregnancy outcomes. Yet a dearth of data exists pertaining to viral infection and pathogenesis in the placenta and the role of the placenta in viral transmission to the fetus. In pregnancy, EBOV infection of pregnant mother results in ~100% fatality for her fetus or neonate with ~60% maternal mortality. Placental immunostaining from EVD outbreaks in Africa demonstrate viral antigen in placental tissues as well as viral RNA in neonates or fetuses of infected mothers. This suggests vertical transmission of virus from mother to fetus. However, rigorous experimental evaluation of maternal transmission and placental infection has not been performed. The tropism of EBOV for placental cells, mechanisms of cellular entry and route of infection from mother to fetus are currently unknown. The long- term goal of this proposal is to understand the biology of EBOV in pregnancy through understanding a) the tropism of EBOV within placental tissues that may lead to the transplacental transmission of virus from mom to baby as well as b) cell surface receptors utilized by EBOV within placental tissues. Aim1 will seek to define the tropism of EBOV in the placenta in early and late pregnancy. For these tropism studies, we will use a model virus, recombinant vesicular stomatitis virus expressing EBOV glycoprotein (rVSV/EBOV GP), to examine viral tropism in placental and fetal tissues. Using this model, we will explore the role of maternal and placental macrophages as well as placental trophoblasts driving tropism. In Aim 2, we will investigate the role of phosphatidylserine (PS) receptors in the placental infection and transmission of virus from placenta to the fetus. In Aim 3, collaborative efforts by Dr. Andrea Marzi at Rocky Mountain Laboratories will utilize mouse- adapted EBOV (maEBOV) in WT C57BL/6 mouse timed-pregnancies to evaluate virus load and tropism at later gestational times. Further, maEBOV-infected placental and fetal tissues will be evaluated for targeted innate immune responses. The data garnered from these targeted and rigorous experiments will establish the first pregnancy model of EBOV, allowing us to mechanistically explore EBOV tropism required for the virus to traffic from dams to fetuses. These studies will provide fundamental information on EBOV biology that will aid in the discovery or development of therapeutic interventions for EBOV infection during pregnancy.
