Altered expression of surface α-1,3-glucan in genetically related strains of Blastomyces dermatitidis that differ in virulence

Abstract

Recent studies of the dimorphic fungal pathogens Histoplasma capsulatum and Paracoccidioides brasiliensis have suggested a role in virulence for the cell surface carbohydrate α-(1,3)-glucan. To investigate a possible basis for α-(1,3)-glucan in the pathogenicity and virulence of the dimorphic fungus Blastomyces dermatitidis, we examined three genetically related strains of B. dermatitidis that differ in their virulence for mice: wild- type virulent strain ATCC 26199; mutant strain ATCC 60915, which is 10,000- fold reduced in virulence; and mutant strain ATCC 60916, which is avirulent. Immunologic quantitation of cell wall α-(1,3)-glucan revealed that the mutant yeasts were almost devoid of this sugar moiety, in contrast to the high concentration of α-(1,3)-glucan on the cell wall of the wild-type yeasts. These differences are discussed in relation to previous studies of yeast surface expression of the WI-1 antigen and recognition and binding of the related strains by human monocyte-derived macrophages.