Pathogenicity of Candida species in a model of oral candidiasis

Objectives: To compare pathogenesis and global gene expression in Candida dubliniensis and Candida albicans, two closely related species with significant differences in virulence and epidemiology, in a model of human oral epithelium. Methods: Reconstituted human epithelium (RHE; TR146 keratinocyte cell lines, Skinethic, France) was inoculated with C. dubliniensis (strain CD36) or C. albicans (strain SC5314). Tissue cross-sections were periodic acid Schiff stained for examination by light microscopy, and RHE tissue damage was assessed with an assay measuring the release of the human enzyme, lactate dehydrogenase (LDH). Total RNA was extracted from Candida-RHE co-cultures 12 h postinoculation for use in competitive hybridization to a C. albicans microarray (Eurogentec, UK). Results: C. dubliniensis grew principally as yeast cells and showed very little adherence to the RHE, while C. albicans grew mainly as hyphae extensively penetrating RHE. After 12 h postinoculation, LDH release in the C. dubliniensis-RHE co-cultures was <15% of LDH release in the C. albicans-RHE cocultures (P< 0.01, Mann Whitney test), indicating much more extensive tissue damage by C. albicans. Yields of total RNA extracted from the co-cultures were >100 µg in each treatment, and results from microarray analyses will be presented. Conclusions: The differences between C. dubliniensis and C. albicans in RHE colonization and damage indicate that C. albicans is a much more efficient and destructive colonizer of RHE, consistent with in vivo observations of greater virulence of C. albicans than C. dubliniensis. This demonstrates the robustness of the RHE model for comparative analysis of Candida virulence. Total RNA yields are sufficient for microarray hybridizations, permitting for the first time comparative analysis of global gene expression in the two species colonizing RHE. Microarray data will aid the identification of genes critical in Candida pathogenicity. This work was funded by Science Foundation Ireland (Programme Investigator grant no. 04/IN3/B463).