Protection of woodchucks from infection with woodchuck hepatitis virus by immunization with recombinant core protein.

Woodchucks were immunized with recombinant woodchuck hepatitis virus (WHV) core antigen (WHcAg) to investigate whether such immunization protects against WHV infection. The C gene was cloned into a pUC12 vector and expressed in Escherichia coli. Core particles purified by sucrose and CsCl gradient centrifugation had a buoyant density of 1.37 g/ml which corresponded to the density of WHcAg particles present in chronically infected liver. Two animals immunized with the recombinant antigen developed high antibody titres and were protected against infection after challenge with WHV. The surface antigen (WHsAg) and WHV DNA were not detected in the sera of immunized animals after challenge and these animals did not develop anti-WHs. Three control animals developed a typical WHV infection. The protection from WHV infection may depend not on the presence of antibodies against the core protein but on a cellular immune response to WHcAg.