Staphylococcal protein A modulates inflammation by inducing interferon signaling in human nasal epithelial cells

Staphylococcus aureus (S. aureus) is one of the leading causes of human respiratory tract infections. The function of Staphylococcal protein A (SpA), expressed on the S. aureus bacterial membrane and released in the environment, on human nasal epithelial cells (HNECs) have not been fully elucidated. In this study, we tested the SpA expression in S. aureus from chronic rhinosinusitis patients and investigated the effects of SpA on HNECs inflammation through Interferon Gamma Receptor 1(IFNGR1)/phosphorylated Janus Kinase 2 (p-JAK2) pathway.

RNA profiling was performed to investigate inflammatory activation in a S. aureus chronic rhinosinusitis (CRS) mouse model. SpA release by S. aureus clinical isolates was determined using ELISA. The effect of purified SpA and SpA enriched conditioned media from S. aureus clinical isolates on HNECs cytotoxicity, apoptosis and release of inflammatory cytokines was evaluated using lactate dehydrogenase assays, and flow cytometry. SpA dependent IFNGR1 and p-JAK2 expression were assessed by qPCR, immunofluorescence and western blot in HNECs.

49 genes were significantly induced in S. aureus CRS mice indicative of activation of interferon signaling. SpA release was significantly higher in S. aureus clinical isolates from chronic rhinosinusitis with nasal polyps (CRSwNP) patients. Purified SpA significantly increased IFNGR1 mRNA and protein expression in HNECs. SpA induced cytotoxic effects and induced the release of Interleukin-6 (IL-6) and IL-8 in an IFNGR1 dependent way.

SpA induces interferon signaling through activation of the IFNGR1-JAK-2 pathway, which provides an understanding of how S. aureus SpA affects the inflammatory process in the upper airways.