The contract at Cornell University has an excellent track record in the breeding and housing of the woodchuck animal model with great lengths taken to study all aspects of this model's infection by the woodchuck hepatitis virus (WHV). This woodchuck/WHV model closely parallels the disease progression produced in humans by the hepatitis B virus (HBV). Predictable numbers of infected pups are produced yearly for experiments such as: (1) the testing of natural and synthetic antivirals and immunomodulators against WHV in infected animals, (2) the study of the coinfection/superinfection of human hepatitis delta virus (HDV) and WHV for the development of HDV vaccines and antivirals, (3) the comparison of disease progression between WHV and the related ground squirrel hepatitis virus (GSHV) in the woodchuck -- the latter producing more cirrhosis and a slower progression to hepatocellular carcinoma, (4) the study of immunologic mechanisms triggered during the acute and chronic stages of the disease and detection of possible pathways to target for prevention of chronicity, and (5) the transfection of woodchuck livers by recombinant WHV DNA to pinpoint biologically important sequences. This contract's goals are to assist with the overall efforts of the Hepatitis Program in the prevention of Types B and D viral hepatitis. Even though safe and effective vaccines are presently available for HBV, there are still over a million chronic carriers of hepatitis B in the U.S. alone. Specifically there is the potential for the eradication of long term complications such as chronic hepatitis B and D liver disease and primary hepatocellular carcinoma by immunization, immunologic methods, or therapeutic treatments.