Characterization of antibody-reactive epitopes on the 65-kilodalton protein of Mycobacterium leprae.

Twenty-three monoclonal antibodies (MAbs) prepared in seven different laboratories were studied, all of which recognized the 65-kilodalton (kDa) protein of Mycobacterium leprae as determined by Western blotting or gel radioimmunoassay or both. Fourteen of the MAbs recognized different epitopes, as evaluated by cross-competition studies using radiolabeled MAb and unlabeled inhibitors; the species specificity of these epitopes was defined by nitrocellulose dot blot immunoassays with bacterial sonic extract antigen preparations from 23 species of mycobacteria. Each of the 14 distinct MAbs recognized a 65-kDa protein produced by a lysogenized Escherichia coli Y1089 host containing cloned rDNA which included the gene for the M. leprae 65-kDa protein. Of the 14 distinct MAbs, 1 recognized an epitope found only on M. leprae, and the others recognized epitopes present on as few as 8 or as many as all 23 of the mycobacterial species studied. Identification of these distinct 65-kDa protein epitopes and use of the MAbs which recognize them should assist future structural studies of this protein and characterization of the T-cell reactive and serodiagnostically useful portions of the molecule.