Biliary atresia (BA) is the most common cause of pediatric end stage liver disease and the number one indication for pediatric liver transplantation. Because pathogenic viruses have been found in the liver of afflicted children, a proposed etiology for biliary atresia is a perinatal viral infection triggering inflammatory destruction of the biliary epithelium. <P>The murine model of biliary atresia supports a viral pathogenesis as newborn mice infected with rhesus rotavirus (RRV) develop inflammation within the portal tract and extra-hepatic bile duct obstruction. Our overarching hypothesis is that biliary atresia results from the infection of cholangiocytes by a virus which re-programs its intracellular environment triggering immune-mediated biliary obstruction. <P>Our focus is to determine the mechanisms used by RRV to infect cholangiocytes, how RRV undergoes replication within the cholangiocyte and how infected cholangiocytes modify the microenvironment by secretion of bioactive molecules. Determination of the mechanistic basis of these inter-related events is essential to understanding the pathogenesis of virus induced BA. <P>The objective of this proposal is to discover how RRV utilizes the intracellular signaling pathways within the cholangiocyte to maximize replication. Specific for this application, we propose the hypothesis that the extracellular regulated kinase 1 and 2 (ERK1/2) signal cascade governs RRV replication. The ERK 1/2 cascade is one of the mitogen activated protein kinase (MAPK) intracellular signaling pathways, and this hypothesis is supported by novel data generated in our laboratory in which inhibition of the MAPK pathways reduced the ability of RRV to replicate within the cholangiocyte. <P>We will determine how this pathway contributes to the pathogenesis of virus induced BA by the examining how cholangiocyte infection by RRV activates the MAPK pathways and how activation of MAPK pathways in turn govern RRV replication. We will use viral binding assays, western blot analysis, siRNA and specific inhibitors of the MAPK pathways to accomplish these goals. <P>PUBLIC HEALTH RELEVANCE: Biliary atresia (BA) is the most common cause of pediatric end stage liver disease and the number one indication for pediatric liver transplantation. Because pathogenic viruses have been found in the liver of afflicted children, a proposed etiology for biliary atresia is a perinatal viral infection triggering inflammatory destruction of the biliary epithelium. Our goal is to determine the mechanistic basis for this process and in so doing develop new treatment strategies to alter the course of this challenging disease. This project is in complete accord with the NIH mission to reduce illness and disability.