Genes for the major protein antigens of Mycobacterium tuberculosis: the etiologic agents of tuberculosis and leprosy share an immunodominant antigen.

Mycobacterium tuberculosis genes encoding immunologically relevant proteins were isolated by systematically screening a lambda gt11 recombinant DNA expression library with a collection of murine monoclonal antibodies directed against protein antigens of this pathogen. These antibodies, previously characterized by a World Health Organization workshop on monoclonal antibodies against mycobacteria, were used to isolate DNA sequences encoding five major protein antigens of this pathogen. To evaluate the extent of crossreactivity between these M. tuberculosis antigens and antigens of Mycobacterium leprae, recombinant antigens were probed with monoclonal antibodies directed against the protein antigens of these bacilli. One of the antigens, a 65-kDa protein, has determinants common to M. tuberculosis and M. leprae. We find not only that this antigen is recognized by mouse monoclonal antibodies but that it is the major protein recognized by anti-M. tuberculosis rabbit sera. The 65-kDa proteins of M. tuberculosis and M. leprae appear to play a role in the humoral and cell-mediated immune response to these pathogens.