Our new reproducible and validated mouse model of dermatophytosis is a modern in vivo tool that allows a more in-depth understanding of the pathogenesis of human dermatophyte infections.

Dermatophytoses (ringworm, jock itch, athlete’s foot, and nail infections) are the most common fungal infections, but their virulence mechanisms are poorly understood. Combining transcriptomic data obtained from growth under various culture conditions with data obtained during infection led to a significantly improved genome annotation. About 65% of the protein-encoding genes predicted with our protocol did not match the existing annotation for A. benhamiae. Comparing gene expression during infection on guinea pigs with keratin degradation in vitro, which is supposed to mimic the host environment, revealed the critical importance of using real in vivo conditions for investigating virulence mechanisms. The analysis of genes expressed in vivo, encoding cell surface and secreted proteins, particularly proteases, led to the identification of new allergen and virulence factor candidates.

Microsporum canis is the most common dermatophyte in pets and is of zoonotic importance but currently there is no effective vaccine available to prevent dermatophytosis. The aim of this work was to assess the immunogenicity and protective efficacy of secreted components (SC) from M. canis adjuvanted with the monophosphoryl lipid-A (MPLA), in a vaccine study using the guinea pig as an experimental model. Animals were vaccinated with either the SC adjuvanted with the MPLA, the MPLA adjuvant alone or PBS three times at two-week intervals, until 42 days prior to M. canis infection. A blind evaluation of dermatophytosis symptoms development and fungal persistence in skin was monitored weekly. The antibody response towards the SC and the levels of Interferon (IFN)γ and Interleukin-4 expressed in peripheral blood mononuclear cells were assessed along or at the end of the study period respectively. The animals that received MPLA had a significantly lower clinical score than those inoculated with PBS. However, no significant difference was observed between the guinea pigs vaccinated with the SC adjuvanted with the MPLA and those having received MPLA alone. The results also showed that vaccination induced a strong antibody response towards the SC and an increase in IFNγ mRNA level. Our results show that the MPLA adjuvant used in this vaccine study can induce per se a partial protection against a M. canis infection. Although they induce a delayed-type hypersensitivity reaction in guinea pigs, the SC do not confer a protection under the present experimental conditions.