Quantitation of the phenolic glycolipid of Mycobacterium leprae and relevance to glycolipid antigenemia in leprosy.

Chemical and immunologic procedures have been developed for quantitation, in the body fluids of patients with leprosy, of phenolic glycolipid I, the major specific antigen of the leprosy bacillus. Serum samples were extracted with CHCl3/CH3OH and fractionated on columns of silicic acid. Thin-layer chromatography with a sensitivity of about 500 ng allowed detection of the glycolipid in untreated lepromatous and borderline patients, and high-pressure liquid chromatography gave a quantitation of 0.8-3.7 micrograms/ml of serum from four patients. An ELISA-inhibition assay with polyclonal antibodies to glycolipid corroborated these figures. Dot-ELISA on nitrocellulose with polyclonal and monoclonal IgG antibodies allowed for much greater sensitivity (500 pg) and semiquantitative evaluation. Small quantities of glycolipid were present in the urine of patients with lepromatous leprosy. In sera obtained from patients undergoing chemotherapy, the amount of glycolipid declined sooner than did titer of antibody. This experimental approach is applicable to diagnosis of leprosy, bacillary quantification, and standardization of skin-test reagents and vaccines.