MAPPING OF CONFORMATIONAL B-CELL EPITOPES WITHIN ALPHA-HELICAL COILED-COIL PROTEINS

An approach to mapping antigenic B cell epitopes within a-helical coil ed coil proteins has been developed and applied to two proteins: Strep tococcal M protein and C. elegans paramyosin protein UNC-15. Overlappi ng peptides derived from an cc-helical coiled coil conformational epit ope were embedded between helical flanking peptides derived from the c ompletely unrelated GCN4 leucine zipper peptide. The resulting chimeri c peptides exhibited helical propensity. Chimeric peptides were tested for antigenicity (recognition by antibody) or immunogenicity (product ion of appropriate antibody response). A conformational epitope within the Streptococcal M protein recognised by three mAbs spanned 12 resid ues. Analysis of chimeric peptides based on C. elegans UNC-15 has enab led fine mapping of the minimal B cell epitope recognised by monoclona l antibody NE1-6B2 to seven non-contiguous residues (spanning 15 resid ues); the footprint of contact residues involved in antibody recogniti on being restricted to the hydrophilic face of the helix and covering five helical turns. This chimeric peptide epitope when coupled to diph theria toroid was highly immunogenic in mice and antisera recognised t he conformationally dependent native peptide epitope. This approach ha s the potential to map conformational epitopes and design minimal epit opes for use as vaccine candidates. (C) 1997 Elsevier Science Ltd.