CELLULAR REPROGRAMMING IN PERSISTENT VS. LYTIC VIRAL INFECTIONS PROJECT SUMMARY The long-range goal of the proposed research is to define the cellular factors that mediate JC polyomavirus (JCPyV) infection to better understand how virus-host cell interactions influence viral pathogenesis. JCPyV infects up to 80% of the population and establishes a lifelong, asymptomatic persistent infection in the kidneys of healthy individuals. However, in immunocompromised individuals JCPyV can spread to the central nervous system (CNS) and cause a lytic infection in glial cells resulting in the fatal, demyelinating disease progressive multifocal leukoencephalopathy (PML). Approximately 5% of individuals with HIV develop PML, a terminal AIDS- defining illness, and individuals receiving immunomodulatory therapies for diseases including multiple sclerosis are at heightened risk for PML development. The increasing number of individuals receiving immunomodulatory therapies due to immune-mediated diseases has led to a rising number of PML cases in the past decade. Over 700 total cases of PML are due to a single drug class. PML can be fatal, especially when underlying immunosuppression is left untreated, and there are currently no approved treatments for this devastating disease. The lack of an animal model and limited cell culture models have largely restricted studies of JCPyV to a single transformed cell culture model. Recently-published studies have revealed that primary cell culture models are a better representation of disease pathogenesis in vivo, and thus we have developed innovative primary cell culture models to define cellular factors that are required for JCPyV infection. Two integrated specific aims are proposed in this research project to: 1) characterize cellular factors that mediate JCPyV entry and infection in primary cell types, and 2) elucidate cell-type dependent differences in persistent and lytic JCPyV infections. This research will enhance our understanding of how virus-host cell interactions influence disease outcomes and will serve as a platform for the development of antiviral treatments. Through this work, cellular factors required for JCPyV entry in primary cell types will be characterized through loss- and gain-of-function approaches using cell-based assays. Transcriptome profiling through RNA sequencing analysis will be used to determine how JCPyV infection alters gene expression in a cell-type dependent manner to identify pathways relevant to JCPyV pathogenesis and fatal disease outcomes. This combinatorial approach utilizes newly developed primary cell models of JCPyV infection and takes advantage of innovative high-throughput analysis of viral and cellular protein expression and RNA sequencing approaches. This research will fill key gaps in our knowledge of JCPyV biology and could elucidate novel antiviral targets or provide rationale for experimental use of on-market therapies to prevent or treat the fatal disease PML. Findings obtained from this research will also provide broader insights into the entry and signaling networks for other pathogenic viruses, like coronaviruses, and improve our understanding of dysregulation of cellular signaling in other diseases such as cancer.