Comparative stability, sensitivity and specificity studies with different lots of Blastomyces dermatitidis yeast and mycelial lysate antigens.

Comparative studies were performed to assess the stability and lot-to-lot variation of Blastomyces dermatitidis yeast and mycelial phase lysate antigens. Four lots were prepared from each growth phase of B. dermatitidis strain T-58 (canine isolate) during a 14-month period. Serum specimens from dogs with blastomycosis, histoplasmosis, coccidioidomycosis, cryptococcosis and aspergillosis were assayed for antibody content using an alkaline phosphatase enzyme-linked immunosorbent assay (ELISA). The four lots of the yeast phase reagents were similar with respect to sensitivity and specificity, and the absorbance readings were approximately four times greater with sera from dogs with blastomycosis than with histoplasmosis or coccidioidomycosis. Even less cross-reactivity was evidenced when the sera from dogs with cryptococcosis and aspergillosis were assayed. In contrast, the four lots of the mycelial lysate reagents were considerably less reactive and more cross-reactive than the yeast phase antigens and, as above, the four reagents retained their activity after prolonged storage. Therefore the results indicated that the lysate antigens exhibited a great deal of stability and lot-to-lot variations in activity were not observed.