Wang Li-Chiu, Chen Su-O, Chang Shih-Ping, Lee Yi-Ping, Yu Chun-Keung, Chen Chia-Ling, Tseng Po-Chun, Hsieh Chia-Yuan, Chen Shun-Hua, Lin Chiou-Feng
Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
J Virol. 2015 Jul;89(14):7028-37. doi: 10.1128/JVI.00205-15. Epub 2015 Apr 29.
Enterovirus 71 (EV71) infection causes severe mortality involving multiple possible mechanisms, including cytokine storm, brain stem encephalitis, and fulminant pulmonary edema. Gamma interferon (IFN-γ) may confer anti-EV71 activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. This study, investigating the role of IFN-γ in EV71 infection using a murine model, showed that IFN-γ was elevated. Moreover, IFN-γ receptor-deficient mice showed higher mortality rates and more severe disease progression with slower viral clearance than wild-type mice. In vitro results showed that IFN-γ pretreatment reduced EV71 yield, whereas EV71 infection caused IFN-γ resistance with attenuated IFN-γ signaling in IFN regulatory factor 1 (IRF1) gene transactivation. To study the immunoediting ability of EV71 proteins in IFN-γ signaling, 11 viral proteins were stably expressed in cells without cytotoxicity; however, viral proteins 2A and 3D blocked IFN-γ-induced IRF1 transactivation following a loss of signal transducer and activator of transcription 1 (STAT1) nuclear translocation. Viral 3D attenuated IFN-γ signaling accompanied by a STAT1 decrease without interfering with IFN-γ receptor expression. Restoration of STAT1 or blocking 3D activity was able to rescue IFN-γ signaling. Interestingly, viral 2A attenuated IFN-γ signaling using another mechanism by reducing the serine phosphorylation of STAT1 following the inactivation of extracellular signal-regulated kinase without affecting STAT1 expression. These results demonstrate the anti-EV71 ability of IFN-γ and the immunoediting ability by EV71 2A and 3D, which attenuate IFN-γ signaling through different mechanisms.
Immunosurveillance by gamma interferon (IFN-γ) may confer anti-enterovirus 71 (anti-EV71) activity; however, the claim that disease severity is highly correlated to an increase in IFN-γ is controversial and would indicate an immune escape initiated by EV71. IFN-γ receptor-deficient mice showed higher mortality and more severe disease progression, indicating the anti-EV71 property of IFN-γ. However, EV71 infection caused cellular insusceptibility in response to IFN-γ stimulation. We used an in vitro system with viral protein expression to explore the novel IFN-γ inhibitory properties of the EV71 2A and 3D proteins through the different mechanisms. According to this study, targeting either 2A or 3D pharmacologically and/or genetically may sustain a cellular susceptibility in response to IFN-γ, particularly for IFN-γ-mediated anti-EV71 activity.
肠道病毒71型（EV71）感染导致严重死亡，涉及多种可能机制，包括细胞因子风暴、脑干脑炎和暴发性肺水肿。γ干扰素（IFN-γ）可能具有抗EV71活性；然而，疾病严重程度与IFN-γ升高高度相关这一说法存在争议，这可能表明EV71引发了免疫逃逸。本研究使用小鼠模型研究IFN-γ在EV71感染中的作用，结果显示IFN-γ水平升高。此外，与野生型小鼠相比，IFN-γ受体缺陷型小鼠死亡率更高，疾病进展更严重，病毒清除速度更慢。体外实验结果表明，IFN-γ预处理可降低EV71产量，而EV71感染导致IFN-γ耐药，同时IFN调节因子1（IRF1）基因转录激活中的IFN-γ信号减弱。为研究EV71蛋白在IFN-γ信号传导中的免疫编辑能力，在无细胞毒性的细胞中稳定表达了11种病毒蛋白；然而，病毒蛋白2A和3D在信号转导和转录激活因子1（STAT1）核转位丧失后，阻断了IFN-γ诱导的IRF1转录激活。病毒3D减弱IFN-γ信号传导，同时伴随STAT1减少，而不干扰IFN-γ受体表达。恢复STAT1或阻断3D活性能够挽救IFN-γ信号传导。有趣的是，病毒2A通过另一种机制减弱IFN-γ信号传导，即在细胞外信号调节激酶失活后，降低STAT1的丝氨酸磷酸化水平，而不影响STAT1表达。这些结果证明了IFN-γ的抗EV71能力以及EV71 2A和3D的免疫编辑能力，它们通过不同机制减弱IFN-γ信号传导。
γ干扰素（IFN-γ）介导的免疫监视可能赋予抗肠道病毒71型（抗EV71）活性；然而，疾病严重程度与IFN-γ升高高度相关这一说法存在争议，这可能表明EV71引发了免疫逃逸。IFN-γ受体缺陷型小鼠死亡率更高，疾病进展更严重，表明IFN-γ具有抗EV71特性。然而，EV71感染导致细胞对IFN-γ刺激不敏感。我们使用病毒蛋白表达的体外系统，通过不同机制探索了EV71 2A和3D蛋白新的IFN-γ抑制特性。根据本研究，从药理学和/或遗传学角度靶向2A或3D可能维持细胞对IFN-γ的敏感性，特别是对于IFN-γ介导的抗EV71活性。
