A family of cross-reacting proteins secreted by Mycobacterium tuberculosis.

Cross-reactions between live proteins actively secreted by Mycohacierium tuberculosis were studied by crossed immunoelectrophoresis, SDS -PAGE with immuiioblotting. and ELISA using polyelonal rabbit aniisera and mouse monoclonal aniibodies to the purified proteins. The monoclonal antibody HBT4 was demonstrated to react with the MPT5I protein. The 85A, 85B and 85C constituents of the M. tuberculosis and Mycobacterium bovis BCG antigen 85 complex cross-react extensively, each of the components containing component-specific as well as cross-reacting epilopes. These components also cross-reacted with MPT5I and MPT64. N-terminal sequence studies revealed striking homology at the amino acid level between 85A, 85B, 85C and MPT51, MPT64 showed less homology. In addition, striking homology was demonslraled between two diflerent stretches within the K5B sequence and indicated between three siretches within the MPT64 molecule. Thus, a family of at least four secreted proteins with common structural features has been demonstrated in mycobacteria, MPT64 may also belong to this family