TSLP acts on neutrophils to drive complement-mediated killing of methicillin-resistant Staphylococcus aureus

Staphylococcus aureus can cause serious skin, respiratory, and other life-threatening invasive infections in humans, and methicillin-resistant S. aureus (MRSA) strains have been acquiring increasing antibiotic resistance. While MRSA was once mainly considered a hospital-acquired infection, the emergence of new strains, some of which are pandemic, has resulted in community-acquired MRSA infections that often present as serious skin infections in otherwise healthy individuals. Accordingly, defining the mechanisms that govern the activation and regulation of the immune response to MRSA is clinically important and could lead to the discovery of much needed rational targets for therapeutic intervention. Because the cytokine thymic stromal lymphopoetin (TSLP) is highly expressed by keratinocytes of the skin3, we investigated its role in host-defense against MRSA. Here we demonstrate that TSLP acts on neutrophils to increase their killing of MRSA. In particular, we show that both mouse and human neutrophils express functional TSLP receptors. Strikingly, TSLP enhances mouse neutrophil killing of MRSA in both an in vitro whole blood killing assay and an in vivo skin infection model. Similarly, TSLP acts directly on purified human blood neutrophils to reduce MRSA burden. Unexpectedly, we demonstrate that TSLP mediates these effects both in vivo and in vitro by engaging the complement C5 system. Thus, TSLP increases MRSA killing in a neutrophil- and complement-dependent manner, revealing a key connection between TSLP and the innate complement system, with potentially important therapeutic implications for control of MRSA infection. Overall design: mRNA expression analysis. 16 samples are from 2 donors, 8 samples per donor, 2 time points (4hr and 16 hr), and 4 conditions (control, TSLP treated, Heat Killed MRSA treated, and TSLP+HKM treated) .

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West EE, Spolski R, Kazemian M, Yu ZX, Kemper C, Leonard WJ