Structure and antigenicity of the major specific glycolipid antigen of Mycobacterium leprae

Abstract

Earlier we reported on the presence of a specific phenolic glycolipid (Phenolic Glycolipid-I) in Mycobacterium leprae, and in infected armadillo tissues (Hunter, S. W., and Brennan, P. J. (1981) J. Bacteriol. 147, 728-735). It had an inherent oligosaccharide, composed of 3-O-Me-rhamnose, 2,3-di-O-Me-rhamnose, and 3,6-di-O-Me-glucose, glycosidically linked to the phenol substituent. The structure of the oligosaccharide has now been determined, by partial acid hydrolysis, permethylation, 1H NMR, and 13C NMR as: 3,6-di-O-Me-Glcp(1 beta leads to 4)2,3-di-O-Me-Rhap(1 alpha leads to 2)3-O-Me-Rhap1 alpha leads to phenol (assuming that the glucose substituent is in the D-enantiomeric configuration, and the two methylated rhamnoses are L). Acid hydrolysis of deacylated Phenolic glycolipid-I yielded a phenolic phthiocerol "core," and mass spectrometry and proton NMR of the permethylated core suggested the following structure: (formula, see text) Combined gas-liquid chromatography-mass spectrometry showed three tetramethyl branched "mycocerosic" acids, C30, C32 and C34, with molecular weights (as methyl esters) of 466, 494, and 522, respectively. These are esterified to the hydroxyl functions of the branched glycolic chain. Evidence is also presented that the glycolipid is immunologically active, reacting with rabbit antisera to M. leprae and with sera from lepromatous leprosy patients.