Identification of bovine T-cell epitopes for three Mycobacterium bovis antigens: MPB70, 19,000 MW and MPB57.

Bovine tuberculosis remains a serious problem in several regions, partly due to a lack of specific diagnostic tests. The aim of this study was to identify bovine T-cell epitopes for defined Mycobacterium bovis antigens using an experimental model of the natural disease. Panels of synthetic peptides (16-mers with five residue overlaps) were produced from published amino acid sequences for MPB70, the 19,000 MW antigen and MPB57. In vitro lymphocyte proliferation assays were used to identify T-cell epitopes. Lymphocytes from experimentally infected cattle proliferated in response to five epitopes (residues 88-105 and 144-163 for MPB70; 1-16 and 67-84 for the 19,000 MW antigen; and 85-100 for MBP57). These epitopes were not recognized by control, non-infected animals, but were recognized by field reactors to intradermal tuberculin testing. All five epitopes were recognized by three different breeds of cattle (Friesian, Charolais and Simmental). In addition, the bovine T-cell epitopes identified for the 19,000 MW antigen in this study were similar to epitopes previously reported for man and mouse. Thus, as well as identifying candidate reagents for improved diagnostic tests and vaccination, this study provides evidence for genetic promiscuity T-cell recognition of major myobacterial epitopes.