T cell response to purified filtrate antigen 85 from Mycobacterium bovis Bacilli Calmette-Guerin (BCG) in leprosy patients

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Abstract
T cell proliferation and IFN-γ production of peripheral blood mononuclear cells from 25 healthy controls and 39 leprosy patients were tested against BCG-bacilli and culture filtrate, Mycobacterium leprae and purified antigen 85 (the major secreted 30–32 kD protein antigen) from M. bovis strain BCG. In lepromin negative healthy controls, blastogenesis was low to M. leprae and completely negative to antigen 85. IFN-γ levels were very low, close to detection limits. In all lepromin positive controls, significant proliferation and IFN-γ secretion was found in response to M. leprae and antigen 85. In the group of lepromatous leprosy (LL) patients, 25/29 of patients (with either positive (13) or negative (12) lymphoproliferative response to BCG) were unreactive to M. leprae or to antigen 85. Four LL patients with positive T cell response to BCG responded with detectable lymphoproliferative response and IFN-γ secretion to antigen 85. All tuberculoid (TT) leprosy patients responded to BCG, M. teprae and antigen 85. Hence, T cells from leprosy patients and controls demonstrate a marked parallelism of responsiveness towards whole M. leprae and purified antigen 85 from M. bovis BCG, suggesting strong eross-reactivity between the two species and underlining the biological importance of such secreted antigens.