Getah virus non-structural protein 2 inhibits type I interferon production by preventing K63-linked polyubiquitination of IKKε and causing widespread cellular shutoff

ABSTRACT Getah virus (GETV) is an emerging mosquito-borne alphavirus that poses a growing threat to animal and public health. However, the molecular mechanisms underlying its pathogenesis and immune evasion remain poorly defined. This study demonstrated that GETV infection suppressed the activation of interferon β (IFN-β) or IFN-stimulated response element after poly(I:C) stimulation. By screening nine viral proteins (non-structural proteins 1–4 [nsP1–4] and C-E3-E2-6K-E1), we discovered that the nsP2 protein of GETV could effectively inhibit the production of IFN-β and IFN-stimulated genes. Subsequently, we discovered that nsP2 disrupted the retinoic acid-inducible gene I-like receptor signaling pathway by causing widespread cellular shutoff and directly targeting inhibitor of kappa-B kinase ε (IKKε). Mechanistically, the inhibitory function of nsP2 is contingent upon the protein’s structural integrity and the presence of proline 717 and nuclear localization signal-related residues. Additionally, we illustrated that nsP2 markedly inhibited TRAF2-induced K63-linked polyubiquitination and phosphorylation of IKKε, which is essential for activating IKKε. Altogether, the present study elucidated a new mechanism in which GETV modulates the host’s antiviral immunity. IMPORTANCE Getah virus (GETV), a multi-host alphavirus of the Togaviridae family, imposes a significant economic burden on the swine industry by causing fever, diarrhea, reproductive disorders in sows, and elevated mortality in newborn piglets. Here, we reveal that GETV non-structural protein 2 antagonizes interferon β (IFN-β) production through a dual mechanism: it induces broad cellular shutoff and directly interacts with inhibitor of kappa-B kinase ε (IKKε) to prevent its activation. This strategy effectively disrupts type I IFN responses by suppressing antiviral gene expression, such as IKKε, IFN-I, and IFN-stimulated genes, and impairing retinoic acid-inducible gene I-like receptor signaling activation. Our findings not only uncover a novel mechanism of GETV immune evasion but also establish the rationale for novel therapeutic targets, suggesting a new avenue for the treatment and intervention of GETV infection.