Studies of Antigens from Young Mycelia of Coccidioides Immitis

Cell-free soluble antigens of Coccidioides immitis strain Silveira were prepared by lysis of young (3-day-old) mycelia in the presence of toluene. The solutions thus derived contained 60 to 70% of the original mycelial mass in soluble form, and one-tenth of the soluble solids were nondialyzable, representing the immunologically active material. This nondialyzable fraction contained 60 to 70% polysaccharide (mainly mannose, but with some galactose and another reducing sugar) and 3 to 4% nitrogen present in amino acids. The lysates contained antigens active in the complement fixation test and were without anticomplementary activity. They gave no significant cross reactions with serum from human histoplasmosis. These lysates possessed activity for both the precipitin and dermal sensitivity tests. One lysate was tested in mice and appeared to enhance resistance to in traperitoneal challenge with C. immitis. The complement-fixing activity was heat-labile and was diminished by acidification to pH 3 ; it was unaffected by papain and was stable in ethanol through 80% concentration. Fractional precipitation with ethanol gave fractions retaining both precipitin and complement-fixing activities at lower ethanol concentrations. At 80% ethanol the precipitate was found to have precipitin antigen activity but not complementfixing activity, indicating some separability of these 2 qualities.