Huang Chen, Zhang Qiong, Guo Xue-kun, Yu Zhi-bin, Xu Ao-tian, Tang Jun, Feng Wen-hai
State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China Ministry of Agriculture Key Laboratory of Soil Microbiology, China Agricultural University, Beijing, China Department of Microbiology and Immunology, College of Biological Sciences, China Agricultural University, Beijing, China.
State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China Department of Basic Veterinary Medicine, College of Veterinary Medicine, China Agricultural University, Beijing, China.
J Virol. 2014 Sep;88(18):10934-45. doi: 10.1128/JVI.01396-14. Epub 2014 Jul 9.
Porcine reproductive and respiratory syndrome virus (PRRSV) is a highly infectious pathogen that causes severe diseases in pigs and great economic losses to the swine industry worldwide. Type I interferons (IFNs) play a crucial role in antiviral immunity. In the present study, we demonstrated that infection with the highly pathogenic PRRSV strain JXwn06 antagonized type I IFN expression induced by poly(I·C) in both porcine alveolar macrophages (PAMs) and blood monocyte-derived macrophages (BMo). Subsequently, we showed that the inhibition of poly(I·C)-induced IFN-β production by PRRSV was dependent on the blocking of NF-κB signaling pathways. By screening PRRSV nonstructural and structural proteins, we demonstrated that nonstructural protein 4 (nsp4), a viral 3C-like serine protease, significantly suppressed IFN-β expression. Moreover, we verified that nsp4 inhibited NF-κB activation induced by signaling molecules, including RIG-I, VISA, TRIF, and IKKβ. nsp4 was shown to target the NF-κB essential modulator (NEMO) at the E349-S350 site to mediate its cleavage. Importantly, nsp4 mutants with defective protease activity abolished its ability to cleave NEMO and inhibit IFN-β production. These findings might have implications for our understanding of PRRSV pathogenesis and its mechanisms for evading the host immune response.
Porcine reproductive and respiratory syndrome virus (PRRSV) is a major agent of respiratory diseases in pigs. Like many other viruses, PRRSV has evolved a variety of strategies to evade host antiviral innate immunity for survival and propagation. In this study, we show that PRRSV nsp4 is a novel antagonist of the NF-κB signaling pathway, which is responsible for regulating the expression of type I interferons and other crucial cytokines. We then investigated the underlying mechanism used by nsp4 to suppress NF-κB-mediated IFN-β production. We found that nsp4 interfered with the NF-κB signaling pathway through the cleavage of NEMO (a key regulator of NF-κB signaling) at the E349-S350 site, leading to the downregulation of IFN-β production induced by poly(I·C). The data presented here may help us to better understand PRRSV pathogenesis.
猪繁殖与呼吸综合征病毒（PRRSV）是一种高度传染性病原体，可导致猪的严重疾病，并给全球养猪业造成巨大经济损失。I型干扰素（IFN）在抗病毒免疫中起关键作用。在本研究中，我们证明，高致病性PRRSV毒株JXwn06感染可拮抗多聚肌苷酸胞苷酸（poly(I·C)）在猪肺泡巨噬细胞（PAM）和血液单核细胞来源的巨噬细胞（BMo）中诱导的I型干扰素表达。随后，我们表明PRRSV对poly(I·C)诱导的IFN-β产生的抑制作用取决于对核因子κB（NF-κB）信号通路的阻断。通过筛选PRRSV非结构蛋白和结构蛋白，我们证明非结构蛋白4（nsp4），一种病毒3C样丝氨酸蛋白酶，可显著抑制IFN-β表达。此外，我们证实nsp4抑制由包括视黄酸诱导基因I（RIG-I）、维甲酸诱导基因I结合蛋白（VISA）、TIR结构域衔接蛋白诱导干扰素β（TRIF）和IκB激酶β（IKKβ）等信号分子诱导的NF-κB激活。nsp4被证明在E349-S350位点靶向NF-κB必需调节因子（NEMO）以介导其切割。重要的是，具有缺陷蛋白酶活性的nsp4突变体消除了其切割NEMO和抑制IFN-β产生的能力。这些发现可能有助于我们理解PRRSV的发病机制及其逃避宿主免疫反应的机制。
猪繁殖与呼吸综合征病毒（PRRSV）是猪呼吸道疾病的主要病原体。与许多其他病毒一样，PRRSV已经进化出多种策略来逃避宿主抗病毒天然免疫以实现生存和繁殖。在本研究中，我们表明PRRSV nsp4是NF-κB信号通路的新型拮抗剂，NF-κB信号通路负责调节I型干扰素和其他关键细胞因子的表达。然后，我们研究了nsp4抑制NF-κB介导的IFN-β产生所使用的潜在机制。我们发现nsp4通过在E349-S350位点切割NEMO（NF-κB信号通路的关键调节因子）来干扰NF-κB信号通路，导致poly(I·C)诱导的IFN-β产生下调。此处呈现的数据可能有助于我们更好地理解PRRSV的发病机制。
