[New studies on the characterization of virulence factors in Microsporum canis]

Microsporum canis is a worldwide distributed zoophilic and zoonotic dermatophyte which is responsible for most cases of feline ringworm. Its prevalence is on the rise in developed countries. Since 1995, the author and his Laboratory have developed a research programme to better understand the pathogenesis of M. canis dermatophytosis. Both the potential fungal virulence factors and the host immune response were investigated. A 31.5 kDa keratinolytic subtilase (SUB) and a 43.5 kDa keratinolytic metalloprotease (MEP) were purified from a crude exoantigen consisted in a mixture of inducible proteins secreted by the fungus in a medium enriched with keratin. Additionally, two gene families encoding respectively 3 SUBs and 3 MEPs, including the 2 keratinases previously purified (called SUB3 and MEP3), were characterized. The genes encoding several MEPs and SUBs were shown to be transcribed in vivo during infection by nested RT-PCR. Finally, we demonstrated that a specific cellular immune response towards the crude exoantigen, MEP3 and SUB3 was induced in experimentally infected guinea pigs. This indicates that the potential immunoprotective properties of these antigens are interesting to evaluate in the frame of the development of an efficient vaccine against feline ringworm.