Human sex hormones stimulate the growth and maturation of Coccidioides immitis

Abstract

Because men and pregnant women show increased susceptibility to extrapulmonary dissemination of coccidioidomycosis, studies were conducted to determine the direct effect of human sex hormones and related compounds on the growth and maturation of Coccidioides immitis in vitro. 17 beta-Estradiol, progesterone, and testosterone were highly stimulatory for the parasitic phase of C. immitis growth whereas cholesterol, ergosterol, and 17 alpha-estradiol (a physiologically inactive stereoisomer of 17 beta-estradiol) lacked such effects. Rates of spherule maturation and endospore release were accelerated, in a dose-dependent fashion, by concentrations of 17 beta-estradiol occurring in normal women, with the most striking effects seen at levels encountered in advanced pregnancy. A stimulatory effect of 17 beta-estradiol on the saprobic phase of fungal growth was also detected. The nonsteroidal "antiestrogens" tamoxifen and nafoxidine had either stimulatory or inhibitory effects, depending on fungal strain and experimental conditions. Diverse strains of Cryptococcus neoformans, Candida sp, and Petriellidium boydii were unaffected by hormones that had distinct effects on C. immitis. These studies suggest that direct stimulation of C. immitis by human sex hormones may help to account for sex- and pregnancy-related predisposition to dissemination of coccidioidomycosis.