48-mer synthetic peptide analogue of the hepatitis B virus "a" determinant induces an anti-HBs antibody response after a single injection.

An extended (48 amino acid) synthetic peptide analogue of the hepatitus B virus (HBV) S protein (HBsAg) 'a' determinant has been produced by using 9-fluorenylmethoxycarbonyl (fmoc) chemistry and a low substitution polystyrene resin as the solid phase support. This peptide (S121/48) elicited a sustained anti-peptide antibody response in BALB/c (H-2(d)) mice when immunised with Freund's complete adjuvant (FCA). Cross-reactive, anti-HBs antibodies were induced, directed against a significant proportion of the conformationally restrained epitope repertoire on the native HBsAg particles. Similar responses were obtained by injection of guinea pigs, a species known both to be exquisitely sensitive to HBsAg and to produce a wide range of B cell responses to HBsAg antigens. Taken together, these data show for the first time, that a synthetic peptide mimicking conformational epitopes can be produced by chemical synthesis and can be used to induce significant titres of anti-HBs antibodies after a single injection. This immunogen has considerable potential for incorporation into novel delivery systems, e.g., microspheres, thus offering the potential of a controlled release, single dose hepatitis B vaccine.