ULTRASTRUCTURAL-LOCALIZATION OF THE SECRETORY ASPARTYL PROTEINASE IN CANDIDA-ALBICANS CELL-WALL IN-VITRO AND IN EXPERIMENTALLY INFECTED-RATVAGINA

Detection and ultrastructural localization of aspartyl proteinase (Sap ) in Candida albicans experimentally infecting rat vagina were studied . Two Sap-positive (Sap(+)) and one Sap-negative (Sap(-)) strains of t he fungus, endowed with high and low experimental vaginopathic potenti al, respectively, were used. Both Sap(+) strains produced consistent S ap levels in the rat vagina, while the Sap-strain did not produce any measurable Sap. Electron microscopy of thin sections of chemically-fix ed vaginal scrapings showed clear evidence of hyphae of proteolitic st rains of C. albicans invading the keratinized epithelial cell layer of the vagina. The fungal cells exhibited a pronounced fibrillar layer o n the cell wall with a marked intermixing of fungal and vaginal materi als especially pronunced at the hyphal tip. Post-embedding immunogold techniques with the use of anti-Sap polyclonal and the specifically ge nerated monoclonal antibody GF1 showed that Sap was essentially locali zed in the cell wall of C. albicans early during infection, in a cytol ogical pattern mirroring Sap localization in C. albicans cells grown i n Sap-inductive media in vitro. In summary, the data offer a new bioch emical and ultrastructural evidence that Sap is actively secreted duri ng experimental rat vaginitis by C. albicans. Cell wall localization o f Sap is probably inherent to this active secretion process.