Differential expression of secreted aspartyl proteinases in a model of human oral candidosis and in patient samples from the oral cavity

Candida albicans, an opportunistic pathogen in humans, secretes secretory aspartyl proteinases (Saps), which have been correlated with virulence. We examined the temporal regulation of the mRNA expression of seven known members of the SAP gene family by reverse transcription polymerase chain reaction (RT-PCR) in (i) an in vitro model of oral candidosis based an reconstituted human epithelium (RHE); and (ii) clinical samples from patients with oral candidosis. SAP1 and SAP3 transcripts were first detected 42h after inoculation of RHE, while at the same time, slight morphological alterations in the epithelium were documented by light microscopy. SAP6 expression occurred 6h later concomitantly with germ tube formation of some infecting Candida cells and severe lesions of the epithelial tissue. SAP2 and SAP8 RT-PCR products were first detected 60 h after infection, while SAP4 and SAPS transcripts were never discovered. Thus a temporal progression of SAP expression in the order SAP1 and SAP3> SAP6> SAP2 and SAP8 was observed at the same time as increasing RHE damage occurred. At the protein level, Sap antigen was found within the C. albicans yeast cells and the epithelial cells by immunoelectron microscopy using an anti-Sap murine monoclonal antibody directed against the gene products Sap1-3. Expression of SAP1-3 and 6 was also detected by RT-PCR in samples from patients suffering from oral candidosis. Our results suggest that the pathogenesis of experimental and clinical oral candidosis is associated with the differential and temporal regulation of SAP gene expression.