Glucuronic acid- and branched sugar-containing glycolipid antigens of Mycobacterium avium.

The pentasaccharide hapten of the dominant glycopeptidolipid antigen of serovariant 19 of the Mycobacterium avium complex is noteworthy because of the uniqueness of its distal glycobiose, the presumed antigen determinant, which contains a 3,4-di-O-methyl glucuronic acid and a novel branched sugar. The detailed structure of the entire pentasaccharide has been established by high field 1H and 13C NMR, fast atom bombardment/mass spectrometry, and various specific degradations as 3,4-di-O-Me-beta-D-GlcAp-(1----3)-2,4-di-O-Me-3-C-Me-3,6-dideox yhexosyl-(1----3)-alpha-L-Rhap-(1----3)-alpha-L-Rhap-( 1----2)-6-dT al; the extreme acid lability of the novel penultimate sugar presented special structural challenges. Thus, the task of defining the variable epitopes of M. avium serovariants in order to charter the epidemiology of opportunistic mycobacterial diseases continues to reveal an unexpected order of sugar diversity and complexity.