Species-specific B-cell epitope on the C-terminal region of the α antigen from Mycobacterium intracellulare in mice

The α antigen, which is an immunodominant antigen, is a 30 kDa protein secreted by mycobacterial species. The C-terminal regions of α antigens are quite divergent. We investigated the question of whether the C-terminal regions of Mycobacterium avium α antigen (A-α), M. intracellulare α antigen (I-α) and M. bovis BCG α antigen (B-α) contained species-specific B-cell epitopes. We investigated the reactions of these peptides with anti-A-α, anti-I-α and anti-B-α sera prepared from BALB/c in a Western blot assay and ELISA. The C-terminal regions of I-α reacted exclusively with anti-I-α serum. The results of the inhibition assay of antibodies binding to I-α by peptides of C-A-α, C-I-α, and C-B-α are that only C-I-α inhibited the binding of antibodies to C-I-α. We found that the C-terminal region was B-cell epitope-specific to I-α in BALB/c mice.