RECOGNITION OF A COMMON MYCOBACTERIAL T-CELL EPITOPE IN MPB59 OF MYCOBACTERIUM-BOVIS

Bovine tuberculosis, which persists as a residual level of infection i n many European countries, has implications not only for the economy o f farming communities bur also for human health. The aim of this study was to identify a common mycobacterial antigen which was recognized i n bovine tuberculosis and to characterize the response to this antigen at the epitope level. A T-cell clone, phenotype CD4(+), raised from a n animal experimentally infected with Mycobacterium bovis was shown to proliferate in response to a panel of sonicates derived from differen t mycobacterial species indicating recognition of an antigen with broa d specificity. This antigen was subsequently shown to be MPB59. Recogn ition of MPB59 at the epitope level was determined in experimental and field cases of bovine tuberculosis using a panel of synthetic peptide s (20-mers with 10-residue overlaps) incorporating the signal sequence and mature protein. The results showed that in vitro interferon-gamma was predominantly produced in response to adjacent peptides numbers 1 0 and 11, suggesting that the dominant epitope was contained in the ov erlap, correlating to residues 101-110 (YYQSGLSVIM). This epitope was recognized by 54% of tuberculous cattle of mixed breeds, which suggest s that it may be genetically permissive in terms of major histocompati bility complex presentation. Sequence analysis confirmed that there we re only minor differences in the amino acid composition within this re gion for various mycobacterial species, which could explain the common T-cell recognition described in this study, Common recognition of thi s epitope indicates that it would have limited potential for use as di agnostic reagent per se but may have potential for inclusion in a subu nit vaccine.