Homology between the MPB70 and MPB83 proteins of Mycobacterium bovis BCG

Isolation of MPB83 from Mycobacterium bovis BCG Tokyo culture fluid is described. MPB70 and MPB83 have similar molecular mass as judged by SDS-PAGE but differ in isoelectric points. Peptides isolated after CNBr cleavage of MPB83 revealed extensive homology as well as distinct differences from corresponding parts of the amino acid sequence deduced from the mpb70 gene cloned by Terasaka et al. Antibodies produced by immunization with MPB70 and MPB83 had distinctly different fine specificity revealing cross-reactivity between the proteins. These findings indicate that two distinct, homologous genes code for these proteins. Sensitization with live BCG Tokyo also induced T cell responses to MPB83 with development of delayed type hypersensitivity in guinea pigs.