[Immunologic study of a synthetic peptide with HBsAg activity]

A cyclic 24-peptide covering 122-145 residues of the HBsAg sequence was synthesized. This study was intended to probe into the prospect of the peptide as a candidate of hepatitis B vaccine. The results of radioimmunoassay showed positive reactions between anti-HBs and synthetic peptide and between anti-peptide and HBsAg. Using GP28/P23, a major protein dissociated from HBsAg, as antigen, the affinities of anti-peptide and anti-HBs were determined and no significant difference was found; indicating an excellent homology between them. The rabbits were immunized with the peptide 300 micrograms X 3, and with HB vaccine 3 micrograms X 3, both added Freund's adjuvant. The serologic anti-HBs level induced by the peptide was nearly 3.3 orders of twofold dilution lower than that by HB vaccine. When mice were immunized with alum adjuvant 250 micrograms of peptide induced an anti-HBs response roughly equal to 0.25 microgram of HB vaccine. So, the immunogenicity of this peptide was approximately (6-12) X 10(-4) times that of HB vaccine.