Nature of the Skin-reactive Principle in Culture Filtrates Prepared from Paracoccidioides brasiliensis

Abstract

Mycelial and yeast-phase culture filtrates prepared from three strains of Paracoccidioides brasiliensis exhibited equal reactivity in sensitized guinea pigs. Ethyl alcohol-precipitated fractions obtained from the culture filtrates also showed no difference in reactivity between mycelial and yeast phase when tested in sensitized guinea pigs. Chemical analyses of the ethyl alcohol-precipitated fractions revealed the presence of seven aliphatic amino acids in both the mycelial- and yeast-phase products. Glucose, galactose, arabinose, and glucosamine were also detected, but the relative proportions of these sugars were different for the mycelial phase as compared with the yeast phase. Both the mycelial- and yeast-phase ethyl alcohol precipitated fractions contained 2 to 4% nitrogen, but no protein or nucleic acid could be detected. Removal of nitrogen from the ethyl alcohol-precipitated fractions by chloroform extraction resulted in an almost complete loss of skin reactivity, whereas the material recovered from the chloroform, which contained most of the nitrogen, still exhibited almost as much reactivity as was present prior to extraction. A considerable portion of the reducing substances was removed along with the nitrogen by the chloroform extraction, suggesting a strong chemical link between the carbohydrate and the peptide portions of the active moiety. Since no protein was present in the fractions, it was presumed that the active moiety is a glycopeptide.