Analysis of human antibody epitopes on the 65-kilodalton protein of Mycobacterium leprae by using synthetic peptides.

In order to study antibody reactivity to the Mycobacterium leprae 65-kilodalton (kDa) antigen, peptides representing overlapping sequences of the 65-kDa protein were synthesized, and a recombinant protein expression system for r65-kDa was constructed. Mouse monoclonal antibodies and leprosy patient seroreactivity to peptides and r65-kDa were tested by an enzyme-linked immunosorbent assay. All seven of the monoclonal antibodies used in this study reacted with their previously defined epitopes when tested against peptides. All monoclonal antibodies also reacted with r65-kDa. Leprosy patient seroreactivity to peptides and r65-kDa was seen in about one-third of active multibacillary cases. Specimens from patients positive for antibodies to peptides were seen to recognize different epitopes than did mouse monoclonal antibodies used in this study. It is concluded that substantial differences exist between mouse monoclonal antibodies and human leprosy patient reactivity to the 65-kDa antigen and that human seroreactivity to the 65-kDa antigen is indicative of a highly elevated bacillary load.