Staphylococcus aureus Virulent PSMα Peptides Induce Keratinocyte Alarmin Release to Orchestrate IL-17-Dependent Skin Inflammation.

Staphylococcus aureus commonly colonizes the epidermis, but the mechanisms by which the host senses virulent, but not commensal, S. aureus to trigger inflammation remain unclear. Using a murine epicutaneous infection model, we found that S. aureus-expressed phenol-soluble modulin (PSM)α, a group of secreted virulence peptides, is required to trigger cutaneous inflammation. PSMα induces the release of keratinocyte IL-1α and IL-36α, and signaling via IL-1R and IL-36R was required for induction of the pro-inflammatory cytokine IL-17. The levels of released IL-1α and IL-36α, as well as IL-17 production by γδ T cells and ILC3 and neutrophil infiltration to the site of infection, were greatly reduced in mice with total or keratinocyte-specific deletion of the IL-1R and IL-36R signaling adaptor Myd88. Further, Il17af mice showed blunted S. aureus-induced inflammation. Thus, keratinocyte Myd88 signaling in response to S. aureus PSMα drives an IL-17-mediated skin inflammatory response to epicutaneous S. aureus infection.