Detection of precipitating antibodies to Histoplasma capsulatum by counterimmunoelectrophoresis

The technique of counterimmunoelectrophoresis was evaluated for its usefulness in the detection of precipitating antibodies to Histoplasma capsulatum, designated h and m precipitin bands. Forty four patients with active histoplasmosis had either m bands or both h and m bands. The h precipitin band occurred primarily in patients with disseminated disease, chronic pulmonary disease, or mediastinal lymphadenopathy of several months' duration; with resolution of the infection, this antibody disappeared. The m band appeared earlier in the course of histoplasmosis and persisted for months to years after resolution of the infection. Antibodies detected by counterimmunoelectrophoresis were in the immunoglobin G class and were more specific for histoplasmosis than those detected by the complement fixation test. Only 1 false positive h band occurred in a total of 81 sera tested (specimens from 24 healthy control subjects and 57 patients with other diseases). Counterimmunoelectrophoresis was both more sensitive and quicker than immunodiffusion at detecting h and m antibodies. Combining this assay with standard complement fixation tests and fungal culture methods should lead to the accurate, rapid diagnosis of histoplasmosis.