Identification of a Mycobacterium leprae specific protein antigen(s) and its possible application for the serodiagnosis of leprosy.

Acetone-killed Mycobacterium leprae separated from infected armadillo liver tissue without the use of proteases were treated with 0.2 M lithium acetate, 20 mM EDTA, pH 8.8 solution, and the concentrated antigen extract was analyzed by Ouchterlony immunodiffusion. The antigen extract gave a single immunoprecipitate when reacted with pooled lepromatous leprosy (LL) patients sera made highly specific for M. leprae by adsorption. Apparently identical precipitates were produced by reacting the antigen extract with sera of each of 15 treated LL patients, 5 of 7 patients with tuberculoid leprosy, and 3 of 4 M. leprae infected armadillos. Serum from 1 of 16 persons immunized with BCG and from none of 15 patients with chlamydial urethritis or brucellosis reacted with the antigen. Identically prepared extracts of M. smegmatis, M. phlei, M. vaccae, M. duvali and M. diernhoferi gave no immunoprecipitates with sera from LL patients or infected armadillos. Preliminary characterization indicates the antigen is protein since antigenicity was destroyed by pronase and/or heat treatment. The relative specificity of the protein antigen for M. leprae and the presence of antibody to this antigen in patients with leprosy suggest a possible role for this antigen in the serodiagnosis of leprosy.