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

The alpha antigen, which is an immunodominant antigen, is a 30 kDa protein secreted by mycobacterial species. The C-terminal regions of alpha antigens are quite divergent. We investigated the question of whether the C-tennina l regions of Mycobacterium avium alpha antigen (A-alpha), M. intracellulare alpha antigen (I-alpha) and M. bovis BCG alpha antigen (B-alpha) contained species-specific B-cell epitopes. We investigated the reactions of these p eptides with anti-A-alpha, anti-I-alpha and anti-B-alpha sera prepared from BALB/c in a Western blot assay and ELISA. The C-terminal regions of I-alph a reacted exclusively with anti-I-alpha serum. The results of the inhibitio n assay of antibodies binding to I-alpha by peptides of C-A-alpha, C-I-alph a, and C-B-alpha are that only C-I-alpha inhibited the binding of antibodie s to C-I-alpha. We found that the C-terminal region was B-cell epitope-spec ific to I-alpha in BALB/c mice. (C) 1999 Elsevier Science B.V. All rights r eserved.