Ubiquitin-specific protease 5 promotes EV-A71 replication by de-ubiquitinating MAVS and IRF3.

Human enterovirus A71 (EV-A71) is a major causative agent of hand, foot and mouth disease (HFMD), which poses a significant public health threat, particularly among young children. Mitochondrial antiviral signaling protein (MAVS) and interferon regulatory factor 3 (IRF3) are vital proteins for the induction of type I interferons (IFN-I) and downstream interferon-stimulated genes (ISGs) during EV-A71 infection. While posttranslational modifications are known to critically influence viral infection processes, the mechanisms by which EV-A71 exploits host deubiquitinases (DUBs) for immune evasion remain poorly understood. In this study, we demonstrated that EV-A71 infection upregulated ubiquitin-specific protease 5 (USP5) expression. Knockdown of USP5 not only inhibited EV-A71 replication but also observably increased the production of IFN-I and ISGs. Furthermore, USP5 also regulated the replication of EV-D68 and CVA16 and the production of IFN-I and ISGs. Mechanistically, USP5 physically interacted with MAVS and IRF3 and reduced the K63-linked polyubiquitination of MAVS and IRF3. Conversely, USP5 knockdown increased the K63-linked polyubiquitination of MAVS and IRF3, thereby accelerating the phosphorylation of IRF3 and increasing IFN-I production during EV-A71 infection. Furthermore, pharmacological inhibition of USP5 with the small-molecule inhibitor PR-619 significantly potentiated the antiviral effects of IFN against EV-A71. Collectively, our findings reveal a previously unrecognized role of USP5 in facilitating EV-A71 immune evasion by dampening MAVS- and IRF3-mediated antiviral signaling. These insights provide a novel therapeutic avenue for combating EV-A71 infection through targeted modulation of the USP5-IRF3 axis.