State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institutegrid.38587.31, Chinese Academy of Agricultural Sciencesgrid.410727.7, Harbin, China.
J Virol. 2022 Dec 21;96(24):e0138822. doi: 10.1128/jvi.01388-22. Epub 2022 Nov 30.
Type III interferons (IFN-λ) are shown to be preferentially produced by epithelial cells, which provide front-line protection at barrier surfaces. Transmissible gastroenteritis virus (TGEV), belonging to the genus of the family , can cause severe intestinal injuries in porcine, resulting in enormous economic losses for the swine industry, worldwide. Here, we demonstrated that although IFN-λ1 had a higher basal expression, TGEV infection induced more intense IFN-λ3 production and than did IFN-λ1. We explored the underlying mechanism of IFN-λ induction by TGEV and found a distinct regulation mechanism of IFN-λ1 and IFN-λ3. The classical RIG-I-like receptor (RLR) pathway is involved in IFN-λ3 but not IFN-λ1 production. Except for the signaling pathways mediated by RIG-I and MDA5, TGEV nsp1 induces IFN-λ1 and IFN-λ3 by activating NF-κB via the unfolded protein responses (UPR) PERK-eIF2α pathway. Furthermore, functional domain analysis indicated that the induction of IFN-λ by the TGEV nsp1 protein was located at amino acids 85 to 102 and was dependent on the phosphorylation of eIF2α and the nuclear translocation of NF-κB. Moreover, the recombinant TGEV with the altered amino acid motif of nsp1 85-102 was constructed, and the nsp1 (85-102sg) mutant virus significantly reduced the production of IFN-λ, compared with the wild strain. Compared to the antiviral activities of IFN-λ1, the administration of IFN-λ3 showed greater antiviral activity against TGEV infections in IPEC-J2 cells. In summary, our data point to the significant role of IFN-λ in the host innate antiviral responses to coronavirus infections within mucosal organs and in the distinct mechanisms of IFN-λ1 and IFN-λ3 regulation. Coronaviruses cause infectious diseases in various mammals and birds and exhibit an epithelial cell tropism in enteric and respiratory tracts. It is critical to explore how coronavirus infections modulate IFN-λ, a key innate cytokine against mucosal viral infection. Our results uncovered the different processes of IFN-λ1 and IFN-λ3 production that are involved in the classical RLR pathway and determined that TGEV nsp1 induces IFN-λ1 and IFN-λ3 production by activating NF-κB via the PERK-eIF2α pathway in UPR. These studies highlight the unique regulation of antiviral defense in the intestine during TGEV infection. We also demonstrated that IFN-λ3 induced greater antiviral activity against TGEV replication than did IFN-λ1 in IPEC-J2 cells, which is helpful in finding a novel strategy for the treatment of coronavirus infections.
III 型干扰素（IFN-λ）优先由上皮细胞产生，上皮细胞在屏障表面提供一线保护。传染性胃肠炎病毒（TGEV）属于冠状病毒科冠状病毒属，可导致猪的严重肠道损伤，给全球养猪业造成巨大经济损失。在这里，我们证明尽管 IFN-λ1 的基础表达水平较高，但 TGEV 感染诱导 IFN-λ3 的产生比 IFN-λ1 更为强烈。我们探讨了 TGEV 诱导 IFN-λ 的潜在机制，发现了 IFN-λ1 和 IFN-λ3 的不同调节机制。经典的 RIG-I 样受体（RLR）途径参与 IFN-λ3 的产生，但不参与 IFN-λ1 的产生。除了 RIG-I 和 MDA5 介导的信号通路外，TGEV nsp1 通过未折叠蛋白反应（UPR）PERK-eIF2α 途径激活 NF-κB，诱导 IFN-λ1 和 IFN-λ3 的产生。此外，功能域分析表明，TGEV nsp1 蛋白诱导 IFN-λ 的作用域位于 85 至 102 个氨基酸，依赖于 eIF2α 的磷酸化和 NF-κB 的核转位。此外，构建了具有改变的 nsp1 85-102 氨基酸模体的重组 TGEV，与野生型相比，nsp1（85-102sg）突变病毒显著降低了 IFN-λ 的产生。与 IFN-λ1 的抗病毒活性相比，IFN-λ3 的给药对 IPEC-J2 细胞中的 TGEV 感染显示出更大的抗病毒活性。总之，我们的数据表明 IFN-λ 在宿主固有抗病毒反应中对粘膜器官中的冠状病毒感染具有重要作用，并且在 IFN-λ1 和 IFN-λ3 的调节机制方面具有不同的作用。冠状病毒在各种哺乳动物和鸟类中引起传染病，在肠和呼吸道中具有上皮细胞嗜性。探索冠状病毒感染如何调节 IFN-λ 这一针对粘膜病毒感染的关键先天细胞因子至关重要。我们的结果揭示了参与经典 RLR 途径的 IFN-λ1 和 IFN-λ3 产生的不同过程，并确定 TGEV nsp1 通过 UPR 中的 PERK-eIF2α 途径激活 NF-κB 诱导 IFN-λ1 和 IFN-λ3 的产生。这些研究强调了在 TGEV 感染期间肠道中抗病毒防御的独特调节。我们还证明，与 IFN-λ1 相比，IFN-λ3 在 IPEC-J2 细胞中诱导对 TGEV 复制的抗病毒活性更强，这有助于找到治疗冠状病毒感染的新策略。
