Biological and chemical characterization of toxic substances from Candida albicans

Whole cells, morphological components, and various extracts of Candida albicans were tested for toxicity by methods involving biological activities ordinarily used to characterize bacterial endotoxin. Fungal preparations exerted several of these activities, but only at much higher dose levels than those required for bacterial products. Both fungal cell walls and intact cells were pyrogenic in rabbits and lethal to actinomycin D-treated mice, but only the former were also lethal to chicken embryos; neither coagulated a hemolysate of horseshoe crabs. Wallfree fungal protoplasm was minimally pyrogenic but negative in the other assays. Bacterial endotoxin was strongly active in all four systems. The toxicity of fungous cell walls was undiminished after exposure to strong alkali, a treatment which destroyed bacterial endotoxin. Extracts obtained with hot phenol-water or potassium hydroxide killed mice but were nonpyrogenic. A defatted and enzyme-digested ethylenediamine extract was both lethal and pyrogenic. Particulate fungal materials but not bacterial endotoxin induced a granulomatous response in prepared mice. These data indicate that contaminating bacterial endotoxin was not responsible for the biological effects of fungal products and suggest that C. albicans may contain at least two different toxic components. Chemical analyses were performed on soluble fractions, but a role in toxicity could not be assigned to any identified component.