Composition and immunogenicity of the polysaccharide components of the thermostable macromolecular antigen group of mycobacterial antigens.

The thermostable macromolecular antigen (TMA) group includes major components of the mycobacterial cell envelope and cytoplasm, which elicit humoral and cellular immune reactions, and seems to play important roles in infectious diseases. The best known member of this group, antigen A60 of Mycobacterium bovis BCG, was previously shown to contain three moieties of polysaccharides, free lipids, and polypeptides. In this work, the TMA polysaccharides of three pathogenic mycobacteria (M. avium, M. bovis and M. paratuberculosis) have been analyzed by coupled gas chromatography-mass spectrometry. In all cases the cores of the TMA complexes were represented by branched glucans of high molecular mass (about 10(6) daltons), for which structural models have been proposed. The immunogenicity of the polysaccharide components from the three TMA was verified with several immunological procedures (immunodiffusion and immunoelectrophoresis of the antigen, and immunoblotting of the corresponding electrofocused immunoglobulins). All tests tallied in showing a negligible immunogenicity of the glucans examined (inability to produce, upon injection, the synthesis of specific immunoglobulins), thus pointing to the protein moiety of TMA as the one responsible for the high immunoreactivity of the complexes.