Species-specific B-cell epitope on the C-terminal region of the α antigen fromMycobacterium scrofulaceum

In the amino acid (AA) sequences of α antigen from mycobacteria, C-terminal regions were variable among a variety of mycobacterial species though the N-terminal regions were relatively conserved. These regions may possess some species-specific antigenic determinants of the α antigen fromMycobacterium scrofulaceum(S-α). AAs288–300 of S-α fused to β-galactosidase was reactive with the antisera raised against S-α. The same fused peptide did not react with the antisera raised against the α antigen fromMycobacterium avium(A-α) andMycobacterium bovisBCG (B-α). B-cell epitope mapping then was performed focusing on the C-terminal region of S-α using the synthetic peptides. Their reactivities with antisera raised against the α antigens of three different mycobacterial species were assessed by ELISA. AAs279–286 were a cross-reactive common immunodominant region among three mycobacterial species. This region may be one of the cross-reactive common epitopes in mycobacterial species. And AAs291–300 were reactive only with the antisera raised against S-α. This region may possess a species-specific epitope.