T-CELL REACTIVITY AGAINST ANTIGEN-85 BUT NOT AGAINST THE 18-KD AND 65-KD HEAT-SHOCK PROTEINS IN THE EARLY STAGES OF ACQUIRED-IMMUNITY AGAINST MYCOBACTERIUM-LEPRAE

T cell proliferation and interferon-gamma (IFN-gamma) production of pe ripheral blood mononuclear cells (PBMC) from 20 household contacts wer e tested against the 18- and 65-kD heat shock proteins from Mycobacter ium leprae (ML18 and ML65 respectively) and antigen 85 from Myco. bovi s bacille Calmette-Guerin (BCG) (Ag 85) during a 12-months follow-up s tudy. Among the eight contacts that became positive, eight showed posi tive reactivity against Ag 85, 5/8 against ML65 and 4/8 against ML18 a t the end of the study. Of the 16 contacts who were lepromin-positive either at first or second testing, all responded to Ag 85, 11 to ML65, but only eight reacted to ML18 antigen. Contacts who were lepromin-po sitive at first testing developed responses to ML18 only at second tes ting. In contrast, among the four contacts that remained lepromin-nega tive during the follow up, three proliferated to Ag 85 either at first or second testing, but only one produced IFN-gamma against Ag 85 at t he end of the study. These results demonstrated that T cell reactivity and particularly IFN-gamma secretion against Ag 85, but not against M L18 and ML65, might be a predominant mechanism in the early stages of acquired protective immunity against Myco. leprae.