Antibody to hepatitis B surface antigen after a single inoculation of uncoupled synthetic HBsAg peptides

A formalin-inactivated hepatitis B virus (HBV) vaccine has been produced in several laboratories (for review, see ref. 1). The sole source of material for these vaccines has been 22-nm lipoprotein particles composed of hepatitis B surface antigen (HBsAg) and derived from plasma of persons chronically infected with HBV. Such a source presents potential hazards in view of unknown factors that may be present in the plasma, and as high-risk populations are immunized, sources of plasma containing large quantities of HBsAg will become scarce. In addition, no tissue culture system has been developed for the propagation of HBV. The possibility of a synthetic peptide vaccine 2,3 for HBV had been suggested 2,3 following studies carried out with tobacco mosaic virus 4,5 and MS-2 coliphage 6 . This possibility recently became a reality when the amino acid sequence for HBsAg was deduced from the nucleotide sequence of the cloned HBV genome (for a review, see ref. 7). More recently a portion of the major polypeptide derived from HBsAg, with a calculated molecular weight of 25,000 (P25), has been sequenced 8 . Lerner et al. 9 have described a similar approach towards HBV synthetic peptides. Antibody to HBsAg (anti-HBs) was raised in rabbits inoculated with three or four doses of a series of peptides, each containing 14–15 amino acid residues, but only after covalent linkage of the peptides to a carrier protein. Activity was also found after multiple injections of a peptide containing 34 amino acids. We have now synthesized two cyclic peptides containing disulphide bonds, both unrelated to those prepared by Lerner, from a hydrophilic region of the major viral polypeptide, which elicited an antibody response in mice after a single injection without linkage to a protein carrier.