Malassezia sympodialis mycovirus

Fungi belonging to the Malassezia species represent the main fungal inhabitant of the mammalian and human skin microbiome. Although they belong to the natural skin commensal flora of humans, they are also associated with a variety of clinical skin disorders. Recent studies have reported associations of Malassezia with Crohn disease and pancreatic cancer, thus revealing an important and unexpected role of this understudied fungal genus. In this study, we discovered a novel mycovirus in several Malassezia species, and further characterized the MsMV1 mycovirus of M. sympodialis. We found conditions which eliminate the virus, and used isogenic virus-infected and virus-cured strains to determine the genetic and pathogenic impact of MsMV1. The MsMV1 virus induces a strong overexpression of transcription factors and ribosomal genes, while down regulating cellular metabolism. Moreover, the MsMV1 mycovirus lead to an increased pathogenicity in a murine model, but induced a significantly higher level of interferon-beta expression in bone marrow-derived macrophages. This study sheds light on the mechanisms of pathogenicity of Malassezia, focusing on a previously unidentified novel mycovirus.