Humoral antibody responses to specific antigens of Coccidioides immitis

To identify antigens important to the diagnosis or pathogenesis of coccidioidomycosis, we analyzed three coccidioidal extracts by immunoblotting techniques with sera from patients infected with Coccidioides immitis and from immunized rabbits. When denatured fungal extracts were used, sera from at least 9 of 10 patients reacted with antigens of 100, 60, and 45 kilodaltons (kDa). By agar diffusion, the 100-kDa antigen appeared to be identical to the conventional tube precipitin antigen. Five of the six sera from patients with pulmonary syndromes reacted with another antigen of 70 kDa, but sera from patients with disseminated disease did not react with this antigen. Both the 100-kDa and the 70-kDa antigens were present in the 70-130-kDa region of the nondenatured fungal extracts. Our results suggest that the 100-kDa antigen may be useful in future diagnostic tests and that the 70-kDa antigen may identify patients whose infection is confined to the chest.