Dynamic expression of candidalysin facilitates oral colonization of Candida albicans in mice

Abstract

Candida albicans is a common fungal member of the human microbiota but can also cause infections via expression of virulence factors associated with the yeast-to-hyphae transition. The evolutionary selection pressure to retain these pathogenic traits for a commensal microorganism remains unclear. Here we show that filamentation and hyphae-associated factors, including the toxin candidalysin, are crucial for colonization of the oral cavity, a major reservoir of C. albicans. Low-virulent strains of C. albicans expressed the candidalysin-encoding gene ECE1 transiently upon exposure to keratinocytes in vitro. In mice, ECE1 mutants were defective at accessing terminally differentiated oral epithelial layers where the fungus is protected from IL-17-mediated immune defence. Tight regulation of ECE1 expression prevented detrimental effects of candidalysin on the host. Our results suggest that hyphae-associated factors such as candidalysin govern not only pathogenicity, but also mucosal colonization through direct host interactions enabling C. albicans to create and maintain its niche in the oral mucosa. Despite being a virulence factor, candidalysin toxin is essential for Candida albicans to penetrate the oral epithelium to establish and maintain non-infectious colonization