Presence of Human T-Cell Responses to theMycobacterium leprae45-Kilodalton Antigen Reflects Infection with or Exposure toM. leprae

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Abstract
The ability of the 45-kDa serine-richMycobacterium lepraeantigen to stimulate peripheral blood mononuclear cell (PBMC) proliferation and gamma interferon (IFN-γ) production was measured in leprosy patients, household contacts, and healthy controls from areas of endemicity in Mexico. Almost all the tuberculoid leprosy patients gave strong PBMC proliferation responses to theM. leprae45-kDa antigen (92.8%;n= 14). Responses were lower in lepromatous leprosy patients (60.6%;n= 34), but some responses to the 45-kDa antigen were detected in patients unresponsive toM. lepraesonicate. The proportion of positive responses to theM. leprae45-kDa antigen was much higher in leprosy contacts (88%;n= 17) than in controls from areas of endemicity (10%;n= 20). None of 15 patients with pulmonary tuberculosis gave a positive proliferation response to the 45-kDa antigen. The 45-kDa antigen induced IFN-γ secretion similar to that induced by the nativeMycobacterium tuberculosis30/31-kDa antigen in tuberculoid leprosy patients and higher responses than those induced by the other recombinant antigens (M. leprae10- and 65-kDa antigens, thioredoxin, and thioredoxin reductase); in patients with pulmonary tuberculosis it induced lower IFN-γ secretion than the other recombinant antigens. These results suggest that theM. leprae45-kDa antigen is a potent T-cell antigen which isM. lepraespecific in these Mexican donors. This antigen may therefore have diagnostic potential as a new skin test reagent or as an antigen in a simple whole-blood cytokine test.