Antigenic protein from Mycobacterium leprae released in macrophages in vitro as indicator of viability of bacteria.

Peritoneal macrophages from randombred, Swiss white mice, when cultured and infected with Mycobacterium leprae for 24 hours, are able to show the presence of antigen(s) with binding affinity to antibodies present in the sera of bacteriologically positive, lepromatous leprosy patients. Such antibodies are not seen in sera from normal and healthy persons, tuberculoid leprosy patients, or long-term-treated, bacteriologically negative, lepromatous leprosy patients. The production of the antigen(s) is blocked by the anti-M leprae drug rifampin. Other mycobacteria when incubated with macrophages from mice show very little antigens in the lysate but the antigens have an equal affinity for antibodies in sera from both normal individuals and lepromatous patients. Only the lysates from macrophages exposed to live M. leprae could discriminate and could exhibit differential binding to sera from leprosy patients compared to sera from normal individuals. This antigen(s) does not have any binding ability to the monoclonal antibodies available to the antigens of M. leprae identified at present and shown to be specific to M. leprae. This indicates a separate identity of this product which has potential for further exploitation in exploring host-pathogen interactions related specifically to the leprosy infection and the tolerance of M. leprae inside cells.