Innate immune response in human keratinocytes infected by a feline isolate of Malassezia pachydermatis

Malassezia pachydermatis is a normal inhabitant of canine and feline skin that can spread to other pets. The outer layer or epidermis is made up primarily of keratinocytes, which are capable of releasing various factors and expressing receptors that are significantly involved in the immune regulation. Little is known about the mechanism by which M. pachydermatis overcomes the natural barrier of the skin. The aim of this study was to evaluate the direct in vitro interaction between human keratinocytes and a clinical strain of live M. pachydermatis isolated as a pure culture from an otitic cat. Human keratinocytes (HaCat) were infected with M. pachydermatis to analyse the modulation of the innate immune response. Gene expression was analysed by real-time PCR. We demonstrated that M. pachydermatis invaded HaCat cells and modulated the expression of TLR2 after 24h infection, while HBD-2, IL-1β TNF-α, IL-6 and IL-8 were modulated both at 24 and 48 h. Thus, our results demonstrated that M. pachydermatis is able to stimulate the innate immune response in infected human keratinocytes indicating a possible role of this yeast as a human opportunistic pathogen.