A major T cell antigen of Mycobacterium leprae is a 10-kD heat-shock cognate protein

Several mycobacterial antigens, identified by monoclonal antibodies and patient sera, have been found to be homologous to stress or heat-shock proteins (hsp) defined in Escherichia coli and yeast. A major antigen recognized by most Mycobacterium leprae-reactive human T cell lines and cell wall-reactive T cell clones is a 10-kD protein that has now been cloned and sequenced. The predicted amino acid sequence of this protein is 44% homologous to the hsp 10 (GroES) of E. coli. The purified native and recombinant 10-kD protein was found to be a stronger stimulator of peripheral blood T cell proliferation than other native and recombinant M. leprae proteins tested. The degree of reactivity paralleled the response to intact M. leprae throughout the spectrum of leprosy. Limiting-dilution analysis of peripheral blood lymphocytes from a patient contact and a tuberculoid patient indicated that approximately one third of M. leprae-reactive T cell precursors responded to the 10-kD antigen. T cell lines derived from lepromin skin tests were strongly responsive to the 10-kD protein. T cell clones reactive to both the purified native and recombinant 10-kD antigens recognized M. leprae-specific epitopes as well as epitopes crossreactive with the cognate antigen of M. tuberculosis. Further, the purified hsp 10 elicited strong delayed-type hypersensitivity reactions in guinea pigs sensitized to M. leprae. The strong T cell responses against the M. leprae 10-kD protein suggest a role for this heat-shock cognate protein in the protective/resistant responses to infection.

Evaluation of the immune response in protection against experimental Streptococcus defectivus endocarditis

Immune protection from endocarditis caused by Streptococcus defectivus was examined by using a rabbit model. Previously we had demonstrated that immunization with nutritionally variant streptococci (NVS, now referred to as Streptococcus, species defectivus and adjacens) protected rabbits against endocarditis when they were challenged with the homologous strain. However, when high-titer immune globulin was transferred to nonimmunized rabbits, no protection was achieved. In the present study, immunosuppressive treatments were given to previously immunized rabbits, and alterations in the level of protection were determined by using the rabbit endocarditis model. Control-immunized rabbits as well as immunized rabbits receiving cyclosporin A or methylprednisolone treatments were protected from S. defectivus endocarditis at levels between 50% and 67%. Rabbits in each of these groups cleared S. defectivus organisms from the circulation by 3 hours after infection. Nitrogen mustard-treated rabbits (immunized or nonimmunized), however, were unable to clear S. defectivus organisms as efficiently (almost 100 times as many organisms in the blood when compared with other groups) by 3 hours, and all were susceptible to endocarditis. These data suggest that circulating phagocytes such as monocytes and granulocytes function to a certain extent in protection against S. defectivus endocarditis. Moreover, when neutrophils were transfused into granulocytopenic and monocytopenic rabbits, efficient clearance was prolonged, indicating that polymorphonuclear leukocytes were involved in the later (greater than 1 hour after infection) phase of protection.