Bovine tuberculosis, which persists as a residual level of
infection in many European countries, has implications not only for the economy of farming communities but also for human health. The aim of this study was to identify a common mycobacterial
antigen which was recognized in
bovine tuberculosis and to characterize the response to this
antigen at the
epitope level. A T-cell clone, phenotype CD4+, raised from an animal experimentally infected with Mycobacterium bovis was shown to proliferate in response to a panel of sonicates derived from different mycobacterial species indicating recognition of an
antigen with broad specificity. This
antigen was subsequently shown to be MPB59. Recognition of MPB59 at the
epitope level was determined in experimental and field cases of
bovine tuberculosis using a panel of synthetic
peptides (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 10 and 11, suggesting that the dominant
epitope was contained in the overlap, correlating to residues 101-110 (YYQSGLSIVM). This
epitope was recognized by 54% of tuberculous cattle of mixed breeds, which suggests that it may be genetically permissive in terms of major histocompatibility complex presentation. Sequence analysis confirmed that there were only minor differences in the
amino acid composition within this region for various mycobacterial species, which could explain the common T-cell recognition described in this study. Common recognition of this
epitope indicates that it would have limited potential for use as a diagnostic
reagent per se but may have potential for inclusion in a
subunit vaccine.