Immunological response to homologous and heterologous phenolic glycolipid antigens in tuberculosis and leprosy.

The occurrence of IgM antibodies immunoreacting in an ELISA test with five phenolic-glycolipids (GPL) antigens (PGL-Tb 1, from M. tuberculosis; PGL-I, from M. leprae; PGK-K-I, from M. kansasii; Mycoside G, from M. marinum; and Mycoside B, from M. bovis), was examined in the sera of 46 tuberculous patients, 48 multibacillary leprosy patients, 40 paucibacillary leprosy patients and in 134 healthy controls. The sensitivity (97.9) and the specificity (91.8) observed in tuberculous patients with the homologous antigen PGL-Tb 1 underlined the interest of this antigen for case finding in tuberculosis epidemiology. The sensitivity and the specificity observed in multibacillary leprosy patients, respectively 91.7 and 91.8, and in paucibacillary leprosy patients, respectively, 35.0 and 91.7, confirmed the limited value of homologous antigen PGL-I for the serological case finding of leprosy patients in endemic areas with a strong incidence of paucibacillary leprosy forms. The data obtained with the heterologous PGL antigens in tuberculosis and multibacillary leprosy serology were higher than those observed in healthy controls and in paucibacillary leprosy patients. However the ELISA using the heterologous antigens was not useful in diagnosis of active tuberculosis or multibacillary leprosy forms. Healthy controls showed low immunoreactivity against PGL antigens, with the exception of mycoside B.