THE MAJOR SECRETED ANTIGEN COMPLEX (AG-85) FROM MYCOBACTERIUM-BOVIS BACILLE CALMETTE-GUERIN IS ASSOCIATED WITH PROTECTIVE T-CELLS IN LEPROSY - A FOLLOW-UP-STUDY OF 45 HOUSEHOLD CONTACTS

T cell proliferation and interferon (IFN)-gamma secretion were analyze d in 45 leprosy contacts stimulated with antigen 85 (Ag85), the major culture filtrate antigen from Mycobacterium bovis bacille Calmette-Gue rin. All 14 Mitsuda reaction-positive contacts reacted to Mycobacteriu m leprae and Ag85. Three Mitsuda reaction-negative contacts reacted we akly to M. leprae and Ag85. The other 28 Mitsuda reaction-negative con tacts did not react to M. leprae, but 9 reacted to Ag85. Thirty-four c ontacts were retested 16 months later. Eleven contacts initially posit ive by the Mitsuda test remained lepromin positive and reactive to M. leprae and Ag85. Fourteen contacts initially negative by the Mitsuda t est converted, and all reacted in vitro to M. leprae and Ag85. Finally , 9 contacts remained Mitsuda test-negative, and 7 were unreactive to Ag85. In vitro reactivity to Ag85 at baseline in Mitsuda test-negative contacts was associated with subsequent conversion to lepromin reacti vity in 7 of 9 subjects. These data suggest that reactive T cells agai nst Ag85 develop very early during M. leprae infection and that Ag85 i s a potentially protective T cell immunogen.