Experimental pathogenicity and acid proteinase secretion of vaginal isolates of Candida parapsilosis

Isolates of Candida parapsilosis from women with or without candidal vaginitis were compared for their ability to produce secretory aspartate (acid) proteinase and their virulence for normal or cyclophosphamide-immunodepressed mice. Although all isolates were strongly proteolytic in vitro, only those from candidosis-affected subjects were appreciably pathogenic for neutropenic mice. In these animals, organ invasion was monitored after challenge with representative isolates of each category. The number of yeast cells in the kidneys of animals infected with an isolate from a subject without candidal vaginitis was approximately one order of magnitude less than that in mice infected with either one of two isolates from patients with candidal vaginitis. Mice infected with either category of C. parapsilosis isolates developed antibodies against a mannoprotein-rich extract of the cell wall, and these antibodies did not cross-react with a chemically similar preparation from Candida albicans. However, only those animals which had been challenged with one of the isolates from a candidosis subject produced a low level of antibodies, detectable by ELISA, against an acid proteinase of C. parapsilosis. These antibodies cross-reacted with a highly purified enzyme preparation of C. albicans. The data demonstrate differences in the potential virulence of different isolates of C. parapsilosis and suggest that the ability to express the acid proteinase in vivo may be related to differences in pathogenicity.