Expression of extracellular acid proteinase by proteolytic Candida spp. during experimental infection of oral mucosa.

We traced an acid proteinase from Candida spp. in the initial stages of the pathogenesis of the mycosis. On infection of human buccal mucosa, proteinase antigens were detected by immuno-scanning electron microscopy on the surface of adhering blastoconidia and invading filamentous cells of C. albicans serotype A. Proteinase antigens were also present on blastoconidia of C. albicans serotype B, but were missing on filamentous cells of this serotype. Proteolytic isolates of C. tropicalis behaved like C. albicans serotype A. An isolate of C. parapsilosis did not express the proteinase antigen under conditions of this study. After infection of mucosa, culture medium of C. albicans or C. tropicalis showed a time-dependent accumulation of acid proteolytic activity, indicating that the visualized antigens represent active proteinase. No such activity was detected in the medium of C. parapsilosis. Preliminary experiments with the proteinase inhibitor pepstatin A revealed an 89% reduction of mucosal adherence of C. albicans (serotype A). These results suggest that Candida proteinase is involved in fungal attachment. The pattern of adherence reflects the differential expression of secretory proteinase by different candidal strains.