Department of Molecular Genetics and Microbiology, Stony Brook University, Life Sciences Room 126, Stony Brook, NY 11794-5222, USA.
J Virol. 2011 May;85(10):4752-60. doi: 10.1128/JVI.01945-10. Epub 2011 Mar 2.
Hantaviruses primarily infect the endothelial cell lining of capillaries and cause two vascular permeability-based diseases. The ability of pathogenic hantaviruses to regulate the early induction of interferon determines whether hantaviruses replicate in endothelial cells. Tula virus (TULV) and Prospect Hill virus (PHV) are hantaviruses which infect human endothelial cells but fail to cause human disease. PHV is unable to inhibit early interferon (IFN) responses and fails to replicate within human endothelial cells. However, TULV replicates successfully in human endothelial cells, suggesting that TULV is capable of regulating cellular IFN responses. We observed a >300-fold reduction in the IFN-stimulated genes (ISGs) MxA and ISG56 following TULV versus PHV infection of endothelial cells 1 day postinfection. Similar to results with pathogenic hantaviruses, expressing the TULV Gn protein cytoplasmic tail (Gn-T) blocked RIG-I- and TBK1-directed transcription from IFN-stimulated response elements (ISREs) and IFN-β promoters (>90%) but not transcription directed by constitutively active IFN regulatory factor-3 (IRF3). In contrast, expressing the PHV Gn-T had no effect on TBK1-induced transcriptional responses. Analysis of Gn-T truncations demonstrated that the C-terminal 42 residues of the Gn-T (Gn-T-C42) from TULV, but not PHV, inhibited IFN induction >70%. These findings demonstrate that the TULV Gn-T inhibits IFN- and ISRE-directed responses upstream of IRF3 at the level of the TBK1 complex and further define a 42-residue domain of the TULV Gn-T that inhibits IFN induction. In contrast to pathogenic hantavirus Gn-Ts, the TULV Gn-T lacks a C-terminal degron domain and failed to bind tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3), a TBK1 complex component required for IRF3 activation. These findings indicate that the nonpathogenic TULV Gn-T regulates IFN induction but accomplishes this via unique interactions with cellular TBK1 complexes. These findings fundamentally distinguish nonpathogenic hantaviruses, PHV and TULV, and demonstrate that IFN regulation alone is insufficient for hantaviruses to cause disease. Yet regulating the early IFN response is necessary for hantaviruses to replicate within human endothelial cells and to be pathogenic. Thus, in addition to IFN regulation, hantaviruses contain discrete virulence determinants which permit them to be human pathogens.
汉坦病毒主要感染毛细血管的内皮细胞衬里，并导致两种基于血管通透性的疾病。致病汉坦病毒调节干扰素早期诱导的能力决定了汉坦病毒是否在血管内皮细胞中复制。图拉病毒（TULV）和展望山病毒（PHV）是感染人类内皮细胞但不会引起人类疾病的汉坦病毒。PHV 无法抑制早期干扰素（IFN）反应，也无法在人类内皮细胞内复制。然而，TULV 成功地在人类内皮细胞中复制，这表明 TULV 能够调节细胞内 IFN 反应。我们观察到，在 TULV 感染内皮细胞 1 天后，与 PHV 相比，IFN 刺激基因（ISGs）MxA 和 ISG56 的表达减少了>300 倍。与致病性汉坦病毒的结果类似，表达 TULV Gn 蛋白细胞质尾巴（Gn-T）阻断了 RIG-I 和 TBK1 从 IFN 刺激反应元件（ISREs）和 IFN-β启动子（>90%）指导的转录，但不阻断由组成型激活的 IFN 调节因子-3（IRF3）指导的转录。相比之下，表达 PHV Gn-T 对 TBK1 诱导的转录反应没有影响。Gn-T 截断分析表明，来自 TULV 的 Gn-T 的 C 末端 42 个残基（Gn-T-C42），但不是 PHV，抑制 IFN 诱导>70%。这些发现表明，TULV Gn-T 在 TBK1 复合物水平上抑制了 IRF3 上游 IFN 和 ISRE 导向的反应，并进一步定义了抑制 IFN 诱导的 TULV Gn-T 的 42 个残基结构域。与致病性汉坦病毒 Gn-Ts 不同，TULV Gn-T 缺乏 C 末端降解结构域，并且不能与肿瘤坏死因子（TNF）受体相关因子 3（TRAF3）结合，TRAF3 是 IRF3 激活所必需的 TBK1 复合物成分。这些发现表明，非致病性 TULV Gn-T 调节 IFN 诱导，但通过与细胞 TBK1 复合物的独特相互作用来完成这一过程。这些发现从根本上区分了非致病性汉坦病毒 PHV 和 TULV，并表明 IFN 调节本身不足以使汉坦病毒引起疾病。然而，调节早期 IFN 反应对于汉坦病毒在人类内皮细胞内复制和成为致病性是必要的。因此，除了 IFN 调节外，汉坦病毒还包含允许它们成为人类病原体的离散毒力决定因素。
