Reduced growth and biofilm formation at high temperatures contribute to Cryptococcus deneoformans dermatotropism.

Abstract

Cryptococcus deneoformans (Cd) and C. neoformans (Cn) differ in geographic prevalence and dermatotropism, with Cd strains more commonly isolated from temperate regions and skin infections. Rising global temperatures prompt concerns regarding selection for environmental fungal species with increased thermotolerance, as high mammalian temperatures provide protection against many fungal species. Cd and Cn strains exhibit variations in thermal susceptibility, with Cd strains being more susceptible to higher temperatures. Here, we identified differences in capsular polysaccharide release, adhesion and biofilm formation between strains both in vivo and in vitro. Histological results suggested that the dermatotropic predilection associated with Cd relates to biofilm formation, possibly facilitating latency and extending fungal survival through protection from high temperatures. We demonstrated that Cn strains were more tolerant to mammalian and febrile temperatures than Cd strains. Similarly, Cd strains showed reduced expression of heat-shock protein 60 and 70, after prolonged exposure to high temperature. Our findings suggest that fungal adhesion, biofilm formation, inflammation and thermotolerance contribute to tissue tropism and disease manifestation by Cn and Cd, supporting the recently assigned species distinction to each of these serotypes.