Project Summary and Relevance. Hepatitis B virus (HBV) infection is a worldwide health problem. It is estimated that there are 200 to 500 million HBV chronic carriers in the world for whom, to date, there is no reliable treatment. HBV causes both acute and chronic liver disease and is responsible for an estimated one million deaths annually from liver cirrhosis and primary hepatocellular carcinoma (HCC). Currently available therapies reduce viral loads but fail to resolve chronic HBV infections and hence require lifelong treatment. A major obstacle to the resolution of chronic HBV infections is the limited number of HBV targets that are suitable for the development of antiviral therapies. All the current antiviral therapies target the HBV reverse transcriptase/DNA polymerase, often leading to the development of drug-resistant variants. Curative therapies will require the identification of additional antiviral targets. Cellular gene products that make a significant contribution to HBV biosynthesis represent potential additional antiviral targets which alone or in combination with current HBV reverse transcriptase inhibitors may represent a potential curative therapy. One potential cellular gene target that might represent an HBV antiviral target is β-catenin, the terminal mediator of the Wnt/β-catenin signal transduction pathway which can be inhibited by the FDA-approved drug, Pyrvinium. Preliminary data indicate that β-catenin can activated HBV transcription and replication in cell culture and β-catenin activity correlates with viral biosynthesis in vivo in the HBV transgenic mouse model of chronic viral infection. Consequently, cell culture analysis will be performed to define the molecular mechanisms mediating β-catenin enhanced HBV transcription and replication. Characterization of inducible liver-specific β-catenin-null and APC-null (β-catenin activated) HBV transgenic mice will indicate the in vivo contribution of β-catenin to the restricted localization of viral biosynthesis to pericentral hepatocytes within the liver lobule and restricted viral expression within HCC tissue. Furthermore, treatment of HBV replicating cells and transgenic mice with Pyrvinium will indicate if an available FDA approved drug can modulate the Wnt/β-catenin signal transduction pathway and act as an antiviral therapy. Defining the role of the Wnt/β-catenin signal transduction pathway in determining the level of HBV biosynthesis may lead to the identification of cellular therapeutic targets that are amenable to the further development of novel modalities to resolve rather than simply treat chronic HBV infection.

Project Narrative Hepatitis B virus (HBV) is a major human pathogen that replicates by reverse transcription of its pregenomic RNA within the viral capsid. HBV pregenomic RNA levels are regulated by the transcriptional coactivator, β-catenin, which also contributes to liver lobule zonation and hepatocellular carcinoma development. A detailed understanding of the mechanism by which β- catenin contributes to viral biosynthesis, hepatocyte metabolism and liver tumor initiation may permit the development of more effective antiviral and cancer therapies targeting the Wnt/β- catenin signal transduction pathway.