M. Marchitto

Neutralizing α-toxin accelerates healing of Staphylococcus aureus-infected wounds in normal and diabetic mice

ABSTRACT Staphylococcus aureus wound infections delay healing and result in invasive complications such as osteomyelitis, especially in the setting of diabetic foot ulcers. In preclinical animal models of S. aureus skin infection, antibody neutralization of alpha-toxin (AT), an S. aureus-secreted pore-forming cytolytic toxin, reduces disease severity by inhibiting skin necrosis and restoring effective host immune responses. However, whether therapeutic neutralization of alpha-toxin is effective against S. aureus-infected wounds is unclear. Herein, the efficacy of prophylactic treatment with a human neutralizing anti-AT monoclonal antibody (MAb) was evaluated in an S. aureus skin wound infection model in nondiabetic and diabetic mice. In both nondiabetic and diabetic mice, anti-AT MAb treatment decreased wound size and bacterial burden and enhanced reepithelialization and wound resolution compared to control MAb treatment. Anti-AT MAb had distinctive effects on the host immune response, including decreased neutrophil and increased monocyte and macrophage infiltrates in nondiabetic mice and decreased neutrophil extracellular traps (NETs) in diabetic mice. Similar therapeutic efficacy was achieved with an active vaccine targeting AT. Taken together, neutralization of AT had a therapeutic effect against S. aureus-infected wounds in both nondiabetic and diabetic mice that was associated with differential effects on the host immune response.

Injury, dysbiosis, and filaggrin deficiency drive skin inflammation through keratinocyte IL-1α release

Background Atopic dermatitis (AD) is associated with epidermal barrier defects, dysbiosis, and skin injury caused by scratching. In particular, the barrier‐defective epidermis in patients with AD with loss‐of‐function filaggrin mutations has increased IL‐1&agr; and IL‐1&bgr; levels, but the mechanisms by which IL‐1&agr;, IL‐1&bgr;, or both are induced and whether they contribute to the aberrant skin inflammation in patients with AD is unknown. Objective We sought to determine the mechanisms through which skin injury, dysbiosis, and increased epidermal IL‐1&agr; and IL‐1&bgr; levels contribute to development of skin inflammation in a mouse model of injury‐induced skin inflammation in filaggrin‐deficient mice without the matted mutation (ft/ft mice). Methods Skin injury of wild‐type, ft/ft, and myeloid differentiation primary response gene–88–deficient ft/ft mice was performed, and ensuing skin inflammation was evaluated by using digital photography, histologic analysis, and flow cytometry. IL‐1&agr; and IL‐1&bgr; protein expression was measured by means of ELISA and visualized by using immunofluorescence and immunoelectron microscopy. Composition of the skin microbiome was determined by using 16S rDNA sequencing. Results Skin injury of ft/ft mice induced chronic skin inflammation involving dysbiosis‐driven intracellular IL‐1&agr; release from keratinocytes. IL‐1&agr; was necessary and sufficient for skin inflammation in vivo and secreted from keratinocytes by various stimuli in vitro. Topical antibiotics or cohousing of ft/ft mice with unaffected wild‐type mice to alter or intermix skin microbiota, respectively, resolved the skin inflammation and restored keratinocyte intracellular IL‐1&agr; localization. Conclusions Taken together, skin injury, dysbiosis, and filaggrin deficiency triggered keratinocyte intracellular IL‐1&agr; release that was sufficient to drive chronic skin inflammation, which has implications for AD pathogenesis and potential therapeutic targets. Graphical abstract Figure. No Caption available.