Enzyme linked immunosorbent assay of a 12-kDa protein of Mycobacterium leprae with sera from leprosy patients.

A low molecular weight protein was obtained from a sonicate of armadillo-derived Mycobacterium leprae cells and from a lambda gt11 phage lysate of Escherichia coli (specifying the M. leprae 12-kDa protein) by a single step of ultrafiltration. Both proteins had an approximate molecular weight of about 12,000 (by SDS-PAGE) and were recognized by the M. leprae 12-kDa-specific monoclonal antibody ML06 by immunoblotting. Sera from 79 leprosy patients across the clinical spectrum, 17 contacts, and 12 normal healthy individuals were screened in an enzyme-linked immunosorbent assay (ELISA) using the 12-kDa proteins as the antigens. Antibodies to the 12-kDa protein (from lysate as well as sonicate) were detected in patients' sera across the clinical spectrum (44%-100% positivity), while no detectable reactivity was observed with control or contact sera. Sera from patients who had undergone a year or more of chemotherapy exhibited no reactivity compared to those from patients with only 3-6 months of chemotherapy. The 12-kDa proteins were also recognized by rabbit hyper-immune M. leprae antiserum.