Different isoforms of secreted aspartyl proteinases (Sap) are expressed by Candida albicans during oral and cutaneous candidosis in vivo.

Distinct isoforms of secreted aspartyl proteinases (Sap) of Candida albicans are important virulence factors for different types of candidosis. Predominant expression of Sap1-3 has been shown to be crucial for superficial infections in experimental mucosal and cutaneous candidosis, whereas Sap4-6 might be important for systemic disease. This in-vivo study investigated Sap expression in two samples from patients with oral candidosis and from cutaneous infection. Two different polyclonal antibodies directed against Sap1-3 and Sap4-6 were used for ultrastructural characterisation of protein localisation and expression. Post-embedding immuno-electron microscopy revealed Sap1-3 and Sap4-6 immunoreactivity in all samples. All C. albicans cells expressed predominantly the proteinases Sap1-3 which were evenly distributed within the cell wall and cytoplasmic membrane. In contrast, Sap4-6 labelling was only evident in a few fungal cells. In particular it was localised at the tips of hyphal cells during invasion. These data suggest a different pathogenetic role for Sap1-3 and Sap4-6 during host-fungal interaction.