Division of Zoonosis of Natural Foci, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
Division of Zoonosis of Natural Foci, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China.
J Virol. 2018 May 29;92(12). doi: 10.1128/JVI.00047-18. Print 2018 Jun 15.
As a prevalent agent in cats, feline herpesvirus 1 (FHV-1) infection contributes to feline respiratory disease and acute and chronic conjunctivitis. FHV-1 can successfully evade the host innate immune response and persist for the lifetime of the cat. Several mechanisms of immune evasion by human herpesviruses have been elucidated, but the mechanism of immune evasion by FHV-1 remains unknown. In this study, we screened for FHV-1 open reading frames (ORFs) responsible for inhibiting the type I interferon (IFN) pathway with an IFN-β promoter reporter and analysis of IFN-β mRNA levels in HEK 293T cells and the Crandell-Reese feline kidney (CRFK) cell line, and we identified the Ser/Thr kinase US3 as the most powerful inhibitor. Furthermore, we found that the anti-IFN activity of US3 depended on its N terminus (amino acids 1 to 75) and was independent of its kinase activity. Mechanistically, the ectopic expression of US3 selectively inhibited IFN regulatory factor 3 (IRF3) promoter activation. Furthermore, US3 bound to the IRF association domain (IAD) of IRF3 and prevented IRF3 dimerization. Finally, US3-deleted recombinant FHV-1 and US3-repaired recombinant FHV-1 (rFHV-dUS3 and rFHV-rUS3, respectively) were constructed. Compared with wild-type FHV-1 and rFHV-rUS3, infection with rFHV-dUS3 induced large amounts of IFN-β and More importantly, US3 deletion significantly attenuated virulence, reduced virus shedding, and blocked the invasion of trigeminal ganglia. These results indicate that FHV-1 US3 efficiently inhibits IFN induction by using a novel immune evasion mechanism and that FHV-1 US3 is a potential regulator of neurovirulence. Despite widespread vaccination, the prevalence of FHV-1 remains high, suggesting that it can successfully evade the host innate immune response and infect cats. In this study, we screened viral proteins for inhibiting the IFN pathway and identified the Ser/Thr kinase US3 as the most powerful inhibitor. In contrast to other members of the alphaherpesviruses, FHV-1 US3 blocked the host type I IFN pathway in a kinase-independent manner and via binding to the IRF3 IAD and preventing IRF3 dimerization. More importantly, the depletion of US3 attenuated the anti-IFN activity of FHV-1 and prevented efficient viral replication and Also, US3 deletion significantly attenuated virulence and blocked the invasion of trigeminal ganglia. We believe that these findings not only will help us to better understand the mechanism of how FHV-1 manipulates the host IFN response but also highlight the potential role of US3 in the establishment of latent infection .
作为猫科动物中的一种流行病原体，猫疱疹病毒 1（FHV-1）感染可导致猫科动物呼吸道疾病和急性及慢性结膜炎。FHV-1 可以成功逃避宿主固有免疫反应并在猫的整个生命周期内持续存在。已经阐明了几种人类疱疹病毒的免疫逃避机制，但 FHV-1 的免疫逃避机制尚不清楚。在这项研究中，我们使用 IFN-β 启动子报告基因和 HEK 293T 细胞和 Crandell-Reese 猫肾（CRFK）细胞系中 IFN-β mRNA 水平的分析，筛选出负责抑制 I 型干扰素（IFN）途径的 FHV-1 开放阅读框（ORF），并鉴定出丝氨酸/苏氨酸激酶 US3 是最强大的抑制剂。此外，我们发现 US3 的抗 IFN 活性取决于其 N 端（氨基酸 1 至 75），并且不依赖于其激酶活性。在机制上，US3 的异位表达选择性抑制 IFN 调节因子 3（IRF3）启动子激活。此外，US3 与 IRF3 的 IRF 结合域（IAD）结合，并阻止 IRF3 二聚化。最后，构建了缺失 US3 的重组 FHV-1（rFHV-dUS3）和修复 US3 的重组 FHV-1（rFHV-rUS3）。与野生型 FHV-1 和 rFHV-rUS3 相比，rFHV-dUS3 感染诱导大量 IFN-β 和 更重要的是，US3 缺失显著减弱了病毒毒力，减少了病毒脱落，并阻断了三叉神经节的侵袭。这些结果表明，FHV-1 US3 通过使用新型免疫逃避机制有效地抑制 IFN 的诱导，并且 FHV-1 US3 是神经毒力的潜在调节剂。尽管广泛接种疫苗，但 FHV-1 的流行率仍然很高，这表明它可以成功逃避宿主固有免疫反应并感染猫。在这项研究中，我们筛选了抑制 IFN 途径的病毒蛋白，并鉴定出丝氨酸/苏氨酸激酶 US3 是最强大的抑制剂。与其他α疱疹病毒不同，FHV-1 US3 以激酶非依赖性方式并通过与 IRF3 IAD 结合和阻止 IRF3 二聚化来阻断宿主 I 型 IFN 途径。更重要的是，US3 的缺失削弱了 FHV-1 的抗 IFN 活性并阻止了有效的病毒复制 此外，US3 缺失显著减弱了病毒毒力并阻断了三叉神经节的侵袭。我们相信，这些发现不仅将帮助我们更好地理解 FHV-1 操纵宿主 IFN 反应的机制，而且还突出了 US3 在建立潜伏感染中的潜在作用 。
