Immunochemical analyses of a major antigen of Mycobacterium szulgai.

Unheated culture filtrate of Mycobacterium szulgai and a homologous goat antiserum were prepared. Immunoelectrophoretic analysis demonstrated a dominant anodal antigen in the culture filtrate. By the use of diethylaminoethyl-cellulose chromatography, a fraction designated MSP, which was rich in this anodal antigen, was recovered. The major antigen of MSP was demonstrated to have partial identity with reference mycobacterial antigen 6, and evidence was obtained for separate shared and specific antigenic determinants. MSP was found to be a potent, delayed skin-test antigen of considerable specificity when used in sensitized guinea pigs. Arthus reactions were also observed and were not specific.