Comparative studies on the detection of antibodies and delayed hypersensitivity responses with 10 Blastomyces dermatitidis lysate antigens

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Abstract
Yeast-phase lysate antigens were prepared from 10 different isolates of Blastomyces dermatitidis. Comparative studies were performed using the lysate antigens in an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies in sera from dogs with blastomycosis and histoplasmosis. In order to evaluate the ability of the lysate reagents to elicit delayed dermal hypersensitivity (DTH) responses, the lysates were compared as skin-testing antigens in hairless guinea pigs that were previously sensitized with B. dermatitidis or Histoplasma capsulatum killed whole yeast cells. All ten of the lysate reagents were able to detect antibody with the ELISA in the serum specimens from dogs with blastomycosis (absorbance values ranged from 0.184 to 0.272; mean value 0.235). In contrast, when the lysates were assayed against sera from dogs with histoplasmosis, the absorbance values ranged from 0.053 to 0.151, with a mean value of 0.092. All ten lysate antigens were able to elicit a DTH response in the B. dermatitidis-immunized animals (mean axes of induration values ranged from 7.0 to 14.4 mm; mean value 8.6 mm). On the other hand, only minimal reactivity was evidenced in the guinea pigs immunized with H. capsulatum (mean axes of induration values ranged from 0.8 to 2.9 mm; mean value 1.8 mm).