Enterovirus D68 Infection Upregulates SOCS3 Expression to Inhibit JAK-STAT3 Signaling and Antagonize the Innate Interferon Response of the Host

Enterovirus D68 (EV-D68) can cause respiratory diseases and acute flaccid paralysis, posing a great threat to public health. Interferons are cytokines secreted by host cells that have broad-spectrum antiviral effects, inducing the expression of hundreds of interferon-stimulated genes (ISGs). EV-D68 activates ISG expression early in infection, but at a later stage, the virus suppresses ISG expression, a strategy evolved by EV-D68 to antagonize interferons. Here, we explore a host protein, suppressor of cytokine signaling 3 (SOCS3), is upregulated during EV-D68 infection and antagonizes the antiviral effects of type I interferon. We subsequently demonstrate that the structural protein of EV-D68 upregulated the expression of RFX7, a transcriptional regulator of SOCS3, leading to the upregulation of SOCS3 expression. Further exploration revealed that SOCS3 plays its role by inhibiting the phosphorylation of signal transducer and activator of transcription 3 (STAT3). The expression of SOCS3 inhibited the expression of ISG, thereby inhibiting the antiviral effect of type I interferon and promoting EV-D68 transcription, protein production, and viral titer. Notably, a truncated SOCS3, generated by deleting the kinase inhibitory region (KIR) domain, failed to promote replication and translation of EV-D68. Based on the above studies, we designed a short peptide named SOCS3 inhibitor, which can specifically bind and inhibit the KIR structural domain of SOCS3, significantly reducing the RNA and protein levels of EV-D68. In summary, our results demonstrated a novel mechanism by which EV-D68 inhibits ISG transcription and antagonizes the antiviral responses of host type I interferon.