Since our isolation and naming of H. hepaticus and elucidating it causes hepatitis and hepatocellular carcinoma in A/J, AGAFx, B6C3F1 and AXB mice, several additional novel helicobacters have been identified in hepatobiliary tissue of both humans and animals. To continue dissecting the pathogenesis of these novel enterohepatic helicobacters, we have recently completed sequencing the genome of the prototype of these emerging enterohepatic pathogens, H. hepaticus. Using this invaluable sequence data, we can study in detail, with the use of isogenic mutants how different virulence genes play a role in chronic inflammation and tumor induction. Furthermore, given H. hepaticus recognized tumor promoting ability with hepatocarcinogens and the increasing recognition of helicobacters in diseased liver tissue of humans where hepatitis B and C virus in infection is endemic, we want to ascertain whether H. hepaticus can synergize with viral proteins to induced hepatocellular carcinomas. Finally, given the ecological niche of these helicobacters in liver is the bile canaliculi, we will explore how helicobacter products or putative virulence genes of H. hepaticus affect colonization dynamics and physiological properties of bile in vivo. Helicobacter hepaticus induced hepatitis and hepatocellular carcinoma in laboratory mice provides a powerful model system for the study of human liver disease and liver cancer. Like the human conditions, disease in the mouse model is multifactorial, with genetic and environmental factors contributing to pathogenesis. The complexity of the system necessitates parallel investigation into bacterial virulence factors, gene expression changes in liver tissue, adaptive immune changes driven by cytokines, biochemical changes in bile and acute phase response components in plasma, and of course lesion development in the liver. This proposal takes advantage of cutting-edge technology to investigate each aspect of disease pathogenesis in this model. A long-term goal is to integrate information gained in each of these areas to build a complete picture of the molecular and cellular mechanisms involved in hepatitis and hepatocellular carcinoma. In this way, our focus will shift over the next 5 years from individual Specific Aims to synergistic areas of overlap between candidate bacterial virulence factors, bacterial expression profile analysis, host expression profile analysis (at the cell, tissue, and organ level), and proteome analysis (using immunohistochemistry, western analysis, and analytic biochemistry). A more complete understanding of the etiopathogenesis of hepatobiliary disease and hepatocellular carcinoma is likely to result in new strategies for treatment and prevention of these important human diseases.
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