Analysis of the major antigenic determinants of the characteristic phenolic glycolipid from Mycobacterium leprae.

Antibodies to the major phenolic glycolipid purified from Mycobacterium leprae have been demonstrated previously in sera of leprosy but not tuberculosis patients using an ELISA. The major antigenic determinants on this molecule were investigated using antisera raised in rabbits to the purified glycolipid and with a pool of sera from human lepromatous leprosy patients. A small, but significant cross-reaction was observed with the glycolipids from M. bovis and M. kansasii, which contain the phenolphthiocerol dimycocerosate part of the molecule but have different sugars, and also with a semi-synthetic 'attenuation indicator lipid' which shares the phenolphthiocerol but has no sugars. There was however no cross-reaction with phthiocerol dimycocerosate. The disaccharide, corresponding to the two terminal sugars of the M. leprae glycolipid has been chemically synthesized and shown to inhibit the reaction between glycolipid and antibody in the ELISA. The cross-reactivity observed with the M. bovis and M. kansasii glycolipids was not inhibited by the synthetic disaccharide. These findings suggest that the cross-reactivity is associated with the phenol ring and implies the disaccharide may be a unique antigenic determinant of M. leprae.