Abstract:
Human enterovirus 68 (EV68) is a member of the EV-D species, which belongs to the EV genus of the Picornaviridae family. Over the past several years, there have been increasingly documented outbreaks of respiratory disease associated with EV68. As a globally emerging pathogen, EV68 infects both adults and children. However, the molecular basis of EV68 pathogenesis is unknown. Here we report that EV68 inhibits Toll-like receptor 3 (TLR3)-mediated innate immune responses by targeting the TIR domain-containing adaptor inducing beta interferon (TRIF). In infected HeLa cells, EV68 inhibits poly(I·C)-induced interferon regulatory factor 3 (IRF3) activation and beta interferon (IFN-β) expression. Further investigations revealed that TRIF, a critical adaptor downstream of TLR3, is targeted by EV68. When expressed alone, 3Cpro, an EV68-encoded protease, cleaves TRIF. 3Cpro mediates TRIF cleavage at Q312 and Q653, which are sites in the amino- and carboxyl-terminal domains, respectively. This cleavage relies on 3Cpro’s cysteine protease activity. Cleavage of TRIF abolishes the capacity of TRIF to activate NF-κB and IFN-β signaling. These results suggest that control of TRIF by 3Cpro may be a mechanism by which EV68 subverts host innate immune responses