Host and Viral Determinants of Orthobunyavirus Vertical Transmission: Novel Model Systems to Understand the Mechanisms of Congenital Disease in Humans and Ruminants

PROJECT SUMMARY/ABSTRACT Emerging infectious diseases pose a significant threat to human and agricultural health; therefore, it is imperative that we take a proactive approach toward understanding virus and host factors that are associated with infection and pathogenesis. Many bunyavirus infections, including Rift Valley fever (RVFV), Cache Valley (CVV), and Schmallenberg (SBV) viruses, cause massive abortogenic events in livestock that lead to significant economic strain and increased susceptibility of human infection. La Crosse virus (LCV), a related bunyavirus, is not known to cause vertical transmission in livestock, however vertical transmission has been implicated upon experimental infection. Two cases of vertical transmission of RVFV have occurred in pregnant women and those infected with RVFV have a higher risk for late-term miscarriages. Whether vertical transmission occurs in ruminants and humans due to LACV infection or in humans from SBV and CVV infection is unknown. Given LACV and CVV infections can cause life-threatening diseases in humans, it is plausible that congenital infection may simply be overlooked due to the mild nature of most bunyavirus infections. We hypothesize that SBV, CVV, and LACV can infect human and ruminant placentas and that virulence factors, such as NSm, and variable induction of antiviral responses across viruses dictate pathogenesis severity, and thus teratogenicity, across host species. This proposal will utilize two model systems to study bunyavirus infection of the placenta. First, we will examine whether LACV, CVV, SBV, and RVFV infect placenta explants from humans, sheep, and rats in vitro. Using wild type and NSm knockout viruses, we will identify whether NSm contributes to host or cellular tropism, immune responses to infection, programmed cell death pathways, and congenital pathogenesis. Second, we will utilize genetically tractable 2D human trophoblast and trophoblast organoid (TO) systems to compare cell- specific differences in immune responses and cell death pathways upon bunyavirus infection. This will be the first study to utilize human placenta organoids to study congenital bunyavirus infection. To successfully complete the proposed project, I have developed an exceptional career development plan under the primary mentorship of Dr. Amy Hartman (University of Pittsburgh (U Pitt)) and co-mentors, Drs. Carolyn Coyne (Duke University) and Leonard D'Aiuto (U Pitt). My training will consist of hands-on and didactic training in human organoid development in addition to didactic training in pathology, cross-species placenta biology, and immunology. U Pitt provides the necessary environment to support the proposed research and training through accessibility to outstanding scientists, high containment laboratory and animal facilities, training opportunities in laboratory management, responsible conduct of research and grantsmanship, and opportunities to present research. Successful training and completion of the proposed research will support my ultimate career goal to establish an independent research program studying the cross virus- and host-species mechanisms of bunyavirus congenital infections with a special niche in human and ruminant placenta organoid research and congenital pathology.