Though accessory proteins are dispensable for the replication of coronavirus in vitro, they play important roles in regulating innate immunity, viral proliferation, and pathogenicity. Different coronavirus genera, or even different species within the same coronavirus genus, encode varying amounts of accessory proteins, leading to genus- or species-specificity. These results indicated a novel mechanism by which IBV inhibits the host antiviral response and provide new insights into the selection of antiviral targets against CoV.Ĭoronavirus accessory proteins are a unique set of proteins whose genes are interspersed among or within the genes encoding structural proteins. Furthermore, Nsp14 interacted with Janus kinase 1 (JAK1) to degrade JAK1 via the autophagy pathway, thereby preventing the activation of the JAK-STAT signaling pathway and facilitating viral replication. Nsp14 impaired the nuclear translocation of chSTAT1. Meanwhile, Nsp14 remarkably reduced interferon-gamma-activated sequence (GAS) promoter activation and chIFN-γ-induced interferon-stimulated gene expression. In these cells, Nsp14 protein overexpression blocked IBV suppression induced by exogenous chIFN-γ treatment. Here we report that IBV Nsp14 was a JAK-STAT signaling pathway antagonist in chicken macrophage (HD11) cells. However, the function and mechanism of IBV Nsp14 in regulating the host’s innate immune response remain unclear. This protein has a regulatory role in viral virulence and replication. Nonstructural protein 14 (Nsp14) is a nonstructural protein encoded by the CoV genome. The Gammacoronavirus avian infectious bronchitis virus (IBV) causes acute and contagious diseases in chickens, leading to severe economic losses. Coronaviruses (CoVs) are RNA viruses that can infect a wide range of animals, including humans, and cause severe respiratory and gastrointestinal disease.

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