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, anti-peptide 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.