ABSTRACT
This chapter describes recombinant-derived hepatitis B surface antigen (HBsAg)-based subunit vaccines that have been developed and licensed on the basis of their efficiency at eliciting anti-HBs. Several experimental recombinant hepatitis B vaccines are described that may elicit immunity based on mechanisms in addition to or instead of anti-HBs. The immunogenicity of yeast-derived hepatitis B vaccines can be demonstrated in several experimental species, including mice and subhuman primates. Protective efficacy in chimpanzees is the most important preclinical immunological test. Depending on the results of the clinical evaluations, inclusion of HBcAg along with HBsAg may be reconsidered in vaccines for nonresponders. Antibodies to HBcAg (anti-HBc) are elicited during acute hepatitis B and persist during chronic hepatitis B without resolution of the disease. Anti-HBc is transferred to the fetus via the placenta but does not prevent perinatal infection. HBcAg can induce cell-mediated immune (CMI) responses in laboratory animals and humans, whereas HBsAg is less effective in eliciting CMI responses.
