Immunoreactivity of mycobacterial strain ICRC and Mycobacterium leprae antigens with polyclonal and monoclonal antibodies.

ICRC, a cultivable mycobacterium, is undergoing clinical trials as an antileprosy vaccine in India. In the present study, we have investigated the crossreactivity between antigens of the mycobacterial strains of ICRC and Mycobacterium leprae using polyclonal and monoclonal antibodies in a radioimmunoprecipitation assay. It was observed that polyclonal anti-ICRC and anti-M. leprae antibodies showed predominant reactivity to a 21-kDa protein of the mycobacterial strain ICRC and the 21- and 14-kDa proteins of M. leprae. Crossreactivity between the antigens of the mycobacterial strains ICRC and M. leprae was established further by using M. leprae-specific monoclonal antibody WML06 (reacting with the 14-kDa protein of M. leprae), which identified the 21- and 14-kDa proteins of the mycobacterial strain ICRC. Thus, our studies demonstrate that the 14-kDa protein of M. leprae, which is known to harbor T- and B-cell epitopes, shares crossreactive antigenic determinants with the 21- and 14-kDa proteins of the mycobacterial strain ICRC. We believe that such proteins may provide important reagents for designing subunit vaccines and for determining skin-test reagents.

Major proteins of mycobacterial strain ICRC and Mycobacterium leprae, identified by antibodies in sera from leprosy patients and their contacts.

Sera from leprosy patients across the clinical spectrum, healthy contacts, tuberculosis patients, and healthy donors were tested for their reactivity with antigens of mycobacterial strain ICRC (a cultivable mycobacterium) and Mycobacterium leprae by immunoprecipitation technique. Using M. leprae antigens, it was not possible to distinguish between reactivities of sera from lepromatous, borderline lepromatous, borderline tuberculoid, and tuberculoid leprosy patients. All these sera identified M. antigens with molecular masses of 47, 36, 21, and 14 kDa. When the same sera were tested for their reactivities with antigens of mycobacterial strain ICRC, several differences were observed. The 21-kDa antigen of mycobacterial strain ICRC was exclusively precipitated by sera from all lepromatous leprosy patients and from those undergoing erythema nodosum leprosum reaction. Sera from all the other donors tested failed to identify the 21-kDa antigen of mycobacterial strain ICRC. The 14-kDa protein of mycobacterial strain ICRC was identified by sera from a few lepromatous leprosy patients (5 of 26) and all their contacts. Our studies indicate that antigens present on cultivable mycobacteria rather than species-specific antigens may prove to be useful in the serodiagnosis of leprosy.