IMMUNOGENICITY OF PEPTIDES FOR B-CELLS IS NOT IMPAIRED BY OVERLAPPINGT-CELL EPITOPE TOPOLOGY

The epitope specificity of T-cell help to B cells and of surface immun oglobulin-mediated B-cell-binding of antigens usually involves topogra phically distinct antigenic determinants. The possibility of cross-rec ognition of the same peptide sequence by both T cells and antibodies h as been a matter of conflicting opinions. We investigated this subject by detailed mapping of T- and B-cell epitopes within four immunogenic mycobacterial peptides. The identified core sequences of T- and B-cel l epitopes showed different topology within each peptide: they were pa rtially overlapping or adjacent in two P38-derived peptides, but entir ely overlapping in two P19-derived peptides. The critically important result using the two truncated peptides (P19/67-78 and P19/146-155) co ntaining only the fully overlapping epitope cores was, that they retai ned full potency for inducing antibody responses. However, despite thi s desirable overlap of determinants, antipeptide sera failed to block the proliferation of corresponding T-cell hybridomas. We conclude, tha t our study, in contrast to previous findings, suggests that overlappi ng topology of T- and B-cell epitopes within synthetic peptides does n ot necessarily impair B-cell immunogenicity.