The use of yeast phase antigens in a complement fixation test for histoplasmosis; preliminary results with rabbit sera.

Abstract

T HE coincidence of pulmonary calcifications and skin sensitivity to histoplasminl-” has suggested either a higher rate of infection with Histoplasrnn capsulatuw. than previously recognized or infection with an immunologically cross-reacting antigen. A recent report6 that H. capsuht~um had been isolated from nonfatal cases implies that infection with this agent may not be uniformly fatal. The high prevalence of skin sensitive reactors 110 histoplasmin in the eastern central states warrants the search for additional t,ools for evaluating evidence of past or present infections with H. capsdatum. Immunologic procedures properly developed and controlled may offer additional information. Skin test antigens (histoplasmin) are prepared from broth filtrates of the mycelial phase of H. capsdatum. Since it is the yeast phase of the organism that appears in affected tissues of man and animal, studies utilizing this phase of the infectious agent may yield additional and possibly more specific results. The ready growth and maintenance of H. capsulatum in the yeast phase has been reported previously by one of us (C.C.C.)7 and by others.P, R The utilization O-C this antigen in preliminary complement fixation studies in experimental animals is herein described. Both viable and nonviable antigens were used in immunization. Since no appreciable differences were noted other than a slightly greater immunogenic capacity of the viable forms, the experiments desrribc4 below are those utilizing killed antigens.