Occurrence of antigenic (species-specific?) partially 3-O-methylated heteromannans in cell wall and soluble cellular (nonwall) components of Coccidioides immitis mycelia

Abstract

Skin test-active, phenol-soluble, water-soluble (PSWS) extracts of Coccidioides immitis whole, defatted mycelia were compared with skin test-active, alkali-soluble, water-soluble (ASWS) extracts of mycelial cell walls. Both PSWS and ASWS extracts contained partially 3-O-methylated mannan. Composition analysis of both PSWS and ASWS extracts indicated mannose and glucose as major components, whereas 3-O-methylmannose and galactose were minor constituents. These heteromannans and glucans could be obtained from cell walls by extraction with either mild acid or alkali, but not with aqueous phenol. We therefore conclude that the PSWS extracts which were obtainable from whole mycelia but not from cell walls represent cellular (i.e., periplasmic, membrane associated, or cytoplasmic), nonwall polymers. Both PSWS and ASWS mycelial extracts and their gel filtration fractions reacted with rabbit antispherule serum, but with little cross-reactivity. However, alkali treatment of higher-molecular-weight PSWS extract polymers yielded products that cross-reacted with serological identity with low-molecular-weight components of ASWS extracts of mycelial walls, indicating that cell walls and cellular polymers share antigenic determinants. Finally, gel filtration of PSWS extracts on Sephacryl S-200 and Sepharose CL 4B yielded fractions that reacted with serological identity with one or more components of mycelial cytosol, mycelial culture filtrate and autolysate coccidioidins, and spherulin.