Deep tissue infection by an invasive human fungal pathogen requires lipid-based suppression of the IL-17 response

Abstract

Candida albicans is the most common cause of fungal infection in humans. IL-17 is critical for defense against superficial fungal infections, but the role of this response in invasive disease is less understood. We show that C. albicans secretes a lipase, Lip2, that facilitates invasive disease via lipid-based suppression of the IL-17 response. Lip2 was identified as an essential virulence factor in a forward genetic screen in a mouse model of bloodstream infection. Murine infection with C. albicans strains lacking Lip2 display exaggerated IL-17 responses that lead to fungal clearance from solid organs and host survival. Both IL-17 signaling and lipase activity are required for Lip2-mediated suppression. Lip2 inhibits IL-17 production indirectly by suppressing IL-23 production by tissue-resident dendritic cells. The lipase hydrolysis product, palmitic acid, similarly suppresses dendritic cell activation in vitro. Thus, C. albicans suppresses antifungal IL-17 defense in solid organs by altering the tissue lipid milieu.

Keywords: Candida albicans; IL-17; fungal pathogenesis; virulence factor.