T-CELL RECOGNITION OF MYCOBACTERIAL PROTEINS MPB70 AND MPB64 IN CATTLE IMMUNIZED WITH ANTIGEN AND INFECTED WITH MYCOBACTERIUM-BOVIS

Defined antigenic reagents and knowledge of T-cell responses are requi red for the design of improved diagnostic tests for bovine tuberculosi s. The limited species distribution of Mycobacterium bovis antigens MP B70 and MPB64 has indicated their potential for inclusion in future te sts. The strategy adopted in this study was to define bovine T-cell re sponses to these antigens at the epitope level, using cattle immunized with recombinant forms of the antigens, and to compare these response s with cattle which had been experimentally infected with M. bovis. Pa nels of synthetic peptides (20-mers with 10-residue overlaps) were use d and five epitopes were identified and found to be powerful stimulato rs of T-cell responses in both types of animal (residues 81-100 and 17 4-190 for MPB70; and residues 1-20, 41-60 and 181-200 for MPB64). Furt her 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 recogniz ed by all animals. However, the limited numbers of animals in this stu dy 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 int erest has proved to be an interesting model for studying the nature of bovine T-cell responses to defined mycobacterial proteins.