OVERALL ABSTRACT Infections of the central nervous system (CNS) are potentially life-threatening and can cause long-term neurological sequelae in patients that survive. Yet, CNS infections remain a diagnostic conundrum with over 50% of cases requiring management without the identification of an etiology. We and others have recently demonstrated that astroviruses, a leading cause of gastroenteritis, are also neuroinvasive. There is a significant gap in our understanding of astrovirus-associated CNS disease. The overall goal of these studies is to fill this gap in knowledge by defining the cellular tropism of astrovirus for CNS cells and the impact of infection on cellular function. The rigor of this proposal is supported by our preliminary studies demonstrating that two genetically distinct human astrovirus strains productively replicate in blood-brain barrier endothelial (BBE) cells and from literature showing astrovirus replication in astrocytes and SK-N-SH cell line. We hypothesize that numerous human astrovirus genotypes, both lab and clinical isolates, will productively replicate in CNS cells impacting cellular function. To test this hypothesis, we have developed the following specific aims: 1. Identify the CNS cells that support astrovirus replication. 2. Determine if replication in CNS cells is specific to VA1 or a property of all human astroviruses. 3. Define the impact of infection on cellular function. My laboratory is uniquely qualified to undertake this work given our long-standing expertise in astrovirus pathogenesis. The death of one of our pediatric patients due to astrovirus-associated CNS infection led us to expand into CNS infection. The studies will be performed in collaboration with St Jude colleagues with expertise in neurobiology including Dr. Elaine Tuomanen (ID), faculty within the Department of Developmental Neurobiology and Dr. Kristen Bernard at the University of Wisconsin, a neurovirology expert. The proposed work will be the basis for follow on studies to determine how astrovirus gets to the brain, examine long-term sequelae, therapeutic strategies, and potentially identify biomarkers of astrovirus-induced CNS.