Defined antigenic
reagents and knowledge of T-cell responses are required for the design of improved diagnostic tests for
bovine tuberculosis. The limited species distribution of Mycobacterium bovis
antigens MPB70 and MPB64 has indicated their potential for inclusion in future tests. The strategy adopted in this study was to define bovine T-cell responses to these
antigens at the
epitope level, using cattle immunized with recombinant forms of the
antigens, and to compare these responses with cattle which had been experimentally infected with M. bovis. Panels of synthetic
peptides (20-mers with 10-residue overlaps) were used and five
epitopes were identified and found to be powerful stimulators of T-cell responses in both types of animal (residues 81-100 and 174-190 for MPB70, and residues 1-20, 41-60 and 181-200 for MPB64). Further investigation in larger numbers of cattle (n = 14) of mixed breeds from
tuberculosis-infected herds confirmed that each
peptide produced response in several of the cattle, but no single
peptide was recognized by all animals. However, the limited numbers of animals in this study suggest that
peptide reagents may identify as many positive animals as the intact antigenic
protein and could form components of a future diagnostic test. The use of cattle immunized with the
proteins of interest has proved to be an interesting model for studying the nature of bovine T-cell responses to defined mycobacterial
proteins.