SFTSV nonstructural protein NSs-mediated immunopathogenesis

项目概要/摘要 严重发热伴血小板减少综合征病毒（SFTSV）已列入世界卫生组织 组织9最危险的病原体是一个新兴的Phlebovirus在Phenuiviridae家庭。 由于缺乏针对SFTSV感染的治疗和疫苗，迫切需要 了解SFTSV的发病机制，开发有效的抗病毒药物。指定为 生物安全性3级病原体，SFTSV含有由三个阴性或阴性片段组成的基因组， 双义RNA被命名为大、中、小。S片段编码一种核蛋白 和非结构蛋白（NS）。(Aim（1）我们发现 NS靶向Vps 15-Vps 34脂质激酶复合物，形成病毒诱导的自噬体样 包涵体（IB），随后螯合IFN信号传导效应物（RIG-I，TRIM 25，和 TBK 1）与IB结合，从而抑制IFN的产生。(Aim 2）我们还发现，SFTSV NS通过靶向TPL 2-ABIN 2-p105激酶在病毒免疫发病机制中起重要作用 复合物以稳健地诱导免疫抑制基因，特别是IL-10细胞因子的表达。 (Aim 3）我们将病毒反向遗传学、TPL 2激酶抑制剂、Tpl 2-/-和il 10-/-小鼠 模型，以显示NS介导的TPL 2信号传导途径的激活强烈诱导IL-10 病毒致病过程中必不可少的产物。我们第一次发展出一个年龄- 依赖性雪貂模型：年轻成年雪貂（<2岁）没有显示任何临床症状， 然而，SFTSV感染的老年雪貂（>4岁）表现出严重的 血小板减少，白色血细胞减少，高热，死亡率约90%，完全 再现人类临床表现。具有良好的体外实验条件 和新的体内动物模型，所提出的研究不仅证明了 SFTSV NS在病毒免疫逃避和发病机制中的作用，而且还确定了潜在的治疗方法， 治疗SFTSV感染患者的方法。

Project Summary/Abstract Severe fever with thrombocytopenia syndrome virus (SFTSV) listed in the World Health Organization 9 most dangerous pathogens is an emerging Phlebovirus in the Phenuiviridae family. Due to the lack of therapy and vaccine against SFTSV infection, there is a pressing need to understand the pathogenesis of SFTSV to develop effective antiviral agents. Designated as Biosafety level 3 agent, SFTSV contains a genome comprised of three segments of negative or ambisense RNA designated as large, medium, and small. The S segment encodes a nucleoprotein and a nonstructural protein (NSs) via an ambisense coding strategy. (Aim 1) We have discovered that NSs targets the Vps15-Vps34 lipid kinase complex to form virus-induced autophagosome-like inclusion bodies (IB), subsequently sequestrating IFN signaling effectors (RIG-I, TRIM25, and TBK1) to the IB and thereby suppressing IFN production. (Aim 2) We have also found that SFTSV NSs plays an essential role in viral immunopathogenesis by targeting the TPL2-ABIN2-p105 kinase complex to robustly induce expression of immune suppressive genes, specifically IL-10 cytokine. (Aim 3) We combined viral reverse genetics, a TPL2 kinase inhibitor, Tpl2-/- and il10-/- mouse models to show that the NSs-mediated activation of TPL2 signaling pathway robustly induced IL-10 production that was essential for viral pathogenesis. For the first time, we developed an age- dependent ferret model: young adult ferrets (<2 years old) did not show any clinical symptoms and mortality; however, SFTSV-infected aged ferrets (>4 years old) demonstrated severe thrombocytopenia, reduced white blood cells, and high fever with ~90% mortality rate, fully recapitulating human clinical manifestation. With well-established in vitro experimental conditions and novel in vivo animal models, the proposed study not only demonstrates the critical role of SFTSV NSs in viral immune evasion and pathogenesis, but also identifies potential therapeutic approaches to treat SFTSV-infected patients.