Antiviral epithelial-macrophage crosstalk permits secondary bacterial infections

Extracellular vesicles (EVs) are produced by most known cell types as a form of intercellular communication to influence the physiological function of neighboring cells. During respiratory viral-bacterial coinfection, the preceding antiviral response can lead to an impaired antibacterial response, driven by miscommunication between cells responding to viruses and cells responding to bacteria. Previous studies have shown that antiviral signaling can influence EV cargo and promote antiviral defense in the recipient cell; however, how antiviral EVs may influence host defense against coinfecting microorganisms, specifically bacteria, is not known. Herein, we demonstrated that EVs released from the respiratory epithelium during antiviral signaling alter macrophage inflammatory signaling, induce anti-inflammatory metabolic reprogramming, and impair antibacterial activity against Staphylococcus aureus, a common coinfecting bacterial pathogen. Further proteomic analysis revealed that antiviral EVs are preferentially loaded with pyruvate kinase M2 (PKM2), a metabolic enzyme with immunomodulatory effects, and treatment with antiviral EVs leads to increased PKM2 in macrophages. Moreover, we showed that antiviral EV-treated macrophages displayed enhanced oxidative phosphorylation, a metabolic profile consistent with impaired S. aureus clearance, and that this metabolic state is phenocopied in macrophages treated with a PKM2 activator. Taken together, our findings identify EVs as a component of the epithelial antiviral response that contributes to impaired bacterial clearance through epithelial-macrophage crosstalk and suggest a role for EVs in driving disease progression during respiratory coinfection.