An enzyme immunoassay for yeast and mycelial phase-specific antibodies in histoplasmosis

The enzyme-linked immunosorbent assay (ELISA) has been adapted to detect class-specific antibodies to yeast and mycelial phase (MP) antigens of Histoplasma capsulatum. Experimental histoplasmosis was produced in rhesus monkeys and humoral immune responses were measured by ELISA and complement-fixation (CF) tests. Antibodies to the yeast phase (YP) reached a peak after 7 weeks and gradually declined thereafter, while MP antibodies continued to increase even after 4 months. Comparison of the 2 tests showed a significant degree of correlation but ELISA was 10-20 times more sensitive than CF. The ELISA method permitted the analysis of low levels of antibodies at early stages of infection. Applications of the ELISA technique to the serodiagnosis of histoplasmosis employing the 2 phase-specific antigens are discussed.