A brief overview of the new vaccines against hepatitis B virus infection: immunogenic gene products and peptide analogues of antigenic epitopes.

Immunologically recognizable antigens encoded by hepatitis B virus (HBV) DNA include: (i) the surface antigen (HBsAg), (ii) the pre-S antigen, (iii) the X antigen (HBxAg) and (iv) the core/e antigens (HBcAg/HBeAg). Each one of these antigens or their combination may be prepared for the next generation of vaccines against HBV infection. The synthesis of HBsAg by expression of recombinant DNA in the yeast system has now reached the stage of clinical trials and will certainly provide the first alternative to the currently licensed plasma-derived HBsAg vaccine. The recombinant vaccinia containing the gene encoding HBsAg and transfected cell-lines expressing HBsAg/pre-S gene products are also contenders for alternative vaccines. Synthetic peptide analogues produced by organic synthesis provide experimental immunogens whose potential for the third generation of vaccines appears promising. Among the following group of immunogenic synthetic peptide analogues (PA), PA (139-147) is more promising, because human antibodies in HBsAg-vaccinated individuals predominantly react with this amino acid sequence: HBsAg sequence PA 110-137, 117-137, 125-137, 134-146, 139-147, 138-149. The N-terminal 22 amino acid sequence of the 55 residues preceding the HBsAg sequence, Pre-S (120-145), with the property of binding polymerized albumin. PA HBxAg sequence (100-115, 144-154). PA'HBcAg sequence (73-84).