Although there has long been a preventive hepatitis B virus (HBV) vaccination available, it is ineffective against chronic infection. The direct and indirect consequences of immunological tolerance to HBV antigens are the major cause of chronic hepatitis B (CHB) and the largest barrier to a therapeutic vaccination. CHB infection is characterized by a deficient CD4+/CD8+ T cell response, low cytokine production, inadequate neutralizing antibody (nAb), and a poor response to HBsAg immunization. The goal of this study was to create virus-like particles (VLPs) that trigger nAb and stimulate CD4+/CD8+ T cells to eliminate intracellular HBV. Eight neutralizing B cell epitopes from the envelope PreS1 region were consolidated onto the woodchuck hepatitis core antigen, a species-variant of the HBV core protein (WHcAg). Because of their preferred expression on HBV virions, PreS1-specific B cell epitopes were selected. Since WHcAg and HBcAg are not cross-reactive at the B cell level and are only partially cross-reactive at the CD4+/CD8+ T cell level, CD4+ T cells specific for WHcAg-specific T cell sites can offer cognate T-B cell assistance for anti-PreS1 Ab production that is not hampered by immunological tolerance.

Immunization of immunological tolerant HBV transgenic (Tg) mice with PreS1-WHc VLPs resulted in anti-PreS1 nAb levels comparable to wildtype animals. In a CHB model, passive transfer of PreS1 nAbs into human-liver chimeric mice prevented acute infection and eliminated serum HBV from animals already infected with HBV. PreS1-WHc VLPs and hybrid WHcAg/HBcAg DNA immunogens induced HBcAg-specific CD4+ Th and CD8+ CTL responses in T cells.