Presence of human T-cell responses to the Mycobacterium leprae 45-kilodalton antigen reflects infection with or exposure to M-leprae

The ability of the 45-kDa serine-rich Mycobacterium leprae antigen to stimu late peripheral blood mononuclear cell (PBMC) proliferation and gamma inter feron (IFN-gamma) production was measured in leprosy patients, household co ntacts, and healthy controls from areas of endemicity in Mexico, Almost all the tuberculoid leprosy patients gave strong PBMC proliferation responses to the M. leprae 45-kDa antigen (92.8%; n = 14), Responses were lower in le promatous leprosy patients (60.6%; n = 34), but some responses to the 45-kD a antigen were detected in patients unresponsive to M. leprae sonicate. The proportion of positive responses to the M. leprae 45-kDa antigen was much higher in leprosy contacts (88%; n = 17) than in controls from areas of end emicity (10%; n = 20), None of 15 patients with pulmonary tuberculosis gave a positive proliferation response to the 45-kDa antigen. The 45-kDa antige n induced IFN-gamma secretion similar to that induced by the native Mycobac terium tuberculosis 30/31-kDa antigen in tuberculoid leprosy patients and h igher responses than those induced by the other recombinant antigens (M, le prae 10- and 65-kDa antigens, thioredoxin, and thioredoxin reductase); in p atients with pulmonary tuberculosis it induced lower IFN-gamma secretion th an the other recombinant antigens, These results suggest that the M. leprae 45-kDa antigen is a potent T-cell antigen which is M. leprae specific in t hese Mexican donors. This antigen may therefore have diagnostic potential a s a new skin test reagent or as an antigen in a simple whole-blood cytokine test.