State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.
State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
J Virol. 2014 Aug;88(16):8936-45. doi: 10.1128/JVI.00700-14. Epub 2014 May 28.
Porcine epidemic diarrhea virus (PEDV), a porcine enteropathogenic coronavirus, causes lethal watery diarrhea in piglets and results in large economic losses in many Asian and European countries. A large-scale outbreak of porcine epidemic diarrhea occurred in China in 2010, and the virus emerged in the United States in 2013 and spread rapidly, posing significant economic and public health concerns. Previous studies have shown that PEDV infection inhibits the synthesis of type I interferon (IFN), and viral papain-like protease 2 has been identified as an IFN antagonist. In this study, we found that the PEDV-encoded nucleocapsid (N) protein also inhibits Sendai virus-induced IFN-β production, IFN-stimulated gene expression, and activation of the transcription factors IFN regulatory factor 3 (IRF3) and NF-κB. We also found that N protein significantly impedes the activation of the IFN-β promoter stimulated by TBK1 or its upstream molecules (RIG-I, MDA5, IPS-1, and TRAF3) but does not counteract its activation by IRF3. A detailed analysis revealed that the PEDV N protein targets TBK1 by direct interaction and that this binding sequesters the association between TBK1 and IRF3, which in turn inhibits both IRF3 activation and type I IFN production. Together, our findings demonstrate a new mechanism evolved by PEDV to circumvent the host's antiviral immunity.
PEDV has received increasing attention since the emergence of a PEDV variant in China and the United States. Here, we identify nucleocapsid (N) protein as a novel PEDV-encoded interferon (IFN) antagonist and demonstrate that N protein antagonizes IFN production by sequestering the interaction between IRF3 and TBK1, a critical step in type I IFN signaling. This adds another layer of complexity to the immune evasion strategies evolved by this economically important viral pathogen. An understanding of its immune evasion mechanism may direct us to novel therapeutic targets and more effective vaccines against PEDV infection.
猪流行性腹泻病毒（PEDV）是一种猪传染性冠状病毒，可导致仔猪致命性水样腹泻，给许多亚洲和欧洲国家造成巨大的经济损失。2010 年中国发生了大规模的猪流行性腹泻疫情，2013 年该病毒出现在美国并迅速传播，对经济和公共卫生构成重大威胁。先前的研究表明，PEDV 感染抑制了 I 型干扰素（IFN）的合成，病毒的木瓜蛋白酶样蛋白酶 2 已被鉴定为 IFN 拮抗剂。在本研究中，我们发现 PEDV 编码的核衣壳（N）蛋白也抑制了仙台病毒诱导的 IFN-β产生、IFN 刺激基因表达以及转录因子 IFN 调节因子 3（IRF3）和 NF-κB 的激活。我们还发现，N 蛋白显著阻碍了 TBK1 或其上游分子（RIG-I、MDA5、IPS-1 和 TRAF3）刺激的 IFN-β启动子的激活，但不拮抗其由 IRF3 激活。详细分析表明，PEDV N 蛋白通过直接相互作用靶向 TBK1，这种结合将 TBK1 与 IRF3 之间的关联隔离，从而抑制 IRF3 的激活和 I 型 IFN 的产生。总之，我们的研究结果表明，PEDV 进化出了一种新机制来规避宿主的抗病毒免疫。
自中国和美国出现 PEDV 变异株以来，PEDV 受到了越来越多的关注。在这里，我们确定核衣壳（N）蛋白是一种新型 PEDV 编码的干扰素（IFN）拮抗剂，并证明 N 蛋白通过隔离 IRF3 和 TBK1 之间的相互作用来拮抗 IFN 的产生，这是 I 型 IFN 信号通路中的一个关键步骤。这为这种具有重要经济意义的病毒病原体进化出的免疫逃避策略增加了另一层复杂性。对其免疫逃避机制的理解可能会指导我们针对 PEDV 感染找到新的治疗靶点和更有效的疫苗。
