Immunogenicity of peptides for B cells is not impaired by overlapping T-cell epitope topology.

The epitope specificity of T-cell help to B cells and of surface immunoglobulin-mediated B-cell-binding of antigens usually involves topographically distinct antigenic determinants. The possibility of cross-recognition of the same peptide sequence by both T cells and antibodies has 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-cell epitopes showed different topology within each peptide: they were partially overlapping or adjacent in two P38-derived peptides, but entirely overlapping in two P19-derived peptides. The critically important result using the two truncated peptides (P19/67-78 and P19/146-155) containing only the fully overlapping epitope cores was, that they retained full potency for inducing antibody responses. However, despite this desirable overlap of determinants, antipeptide sera failed to block the proliferation of corresponding T-cell hybridomas. We conclude, that our study, in contrast to previous findings, suggests that overlapping topology of T- and B-cell epitopes within synthetic peptides does not necessarily impair B-cell immunogenicity.