Heterologous transfection of an endornavirus alters the phenotype of Trichophyton rubrum in vitro and in vivo

Mycoviruses are widely distributed across fungal taxa, yet their impact on the phenotype and pathogenicity of dermatophytes remains poorly understood. In this study, we investigated the presence of mycoviruses in clinical isolates of Trichophyton sp. and characterized the phenotypic effects of previously described Terfezia claveryi endornavirus 1 (TcEV1) through heterologous transfection. While most endornaviruses are associated with cryptic infections, our results demonstrate that cross species transmission of TcEV1 significantly alters the physiological profile of T. rubrum . TcEV1-infected isolate exhibited increased radial growth at 30 °C and a significant rise in conidiation capacity. Most importantly, in a murine skin infection model, the virus-infected isolate showed a ~ 2.5-fold increase in fungal load, indicating enhanced in vivo colonization. Furthermore, TcEV1 infection was associated with reduced susceptibility to echinocandins and amphotericin B. These findings provide the first evidence of mycovirus-mediated “enhanced virulence” in T. rubrum , suggesting that viral elements may play a critical role in the severity and treatment resistance of dermatophytosis.