TFF2在重症流感病毒感染中保护作用的机制研究

Emerging and re-emerging respiratory infectious diseases have posed great challenges on health, social stability and economic development. Patients often face the threat of death due to lack of effective medicines. It is urgent to decipher the underlying mechanism for the pathogenesis of emerging respiratory pathogens and thereafter to develop prevention and treatment strategies. By employing transcriptomic tools, we have systemically compared gene expressions between infections of high pathogenic avian influenza (HPAI) H7N9 and of low pathogenic H9N2, observed that the expression of TFF2 is significantly higher in H9N2 infection than in H7N9 infection and pre-treatment of TFF2 confers a protection to mice from a mortality challenge of H7N9. In this proposal, we will further explore the protective mechanism for TFF2 in HPAI infection. By using protection models in vivo and in vitro, we will further investigate and identify the key gene targets and signaling pathways for TFF2 with several cutting-edge technologies, including RNA-seq, RNA hybridization in situ and Gene knockout mice. Data generated from this study will enlighten the development of novel preventive and treatment strategies against the life-threating infection of emerging respiratory pathogens.

新发突发呼吸道传染病（如SARS、H7N9等）给人民健康、社会稳定与经济发展带来严重挑战，患者常因缺乏特效药而面临死亡威胁。解析新发呼吸道病原体致病机制，并研发针对性预防与治疗策略具有迫切性。本团队前期对比分析高致病与低致病性禽流感H7N9与H9N2感染小鼠后肺组织的转录组学数据，发现TFF2在肺组织中的表达水平与预后密切相关，TFF2在低致病性的H9N2感染后高表达，且预防性将TFF2通过滴鼻给药可保护小鼠免于H7N9的致死性攻击。在此基础上，本研究拟进一步开展TFF2在高致病流感病毒感染中保护作用的机制研究。利用TFF2体内与体外保护模型， 通过组学分析、肺组织原位RNA杂交、信号通路关键基因的敲除等筛选与确认TFF2作用关键靶点与信号通路，为预防与干预新发突发呼吸道传染病重症化奠定理论基础。

本项目通过流感病毒感染小鼠模型发现TFF2不影响流感病毒复制，而是通过下调炎症信号通路，抑制炎症细胞因子分泌，促进肺组织黏膜损伤修复而发挥保护效应。组织原位研究显示TFF2主要在肺组织气道上皮细胞中产生，能与巨噬细胞，上皮细胞和一小部分CD4+T细胞结合。通过体外细胞研究筛选到与TFF2直接相互作用的细胞表面糖蛋白A4GNT和EGFR，其中，TFF2与EGFR的结合需要A4GNT介导。进一步对A4GNT的结构和功能分析，发现A4GNT的糖基转移酶活性位点以及胞外区的C末端影响TFF2与靶细胞结合。另外，TFF2抑制LPS刺激A4GNT+THP-1细胞的NF-κB p65磷酸化以及炎症细胞因子TNF-α的表达。在A4GNT敲除小鼠的流感感染模型中，TFF2失去了保护效应。因此，本项目揭示了TFF2在重症流感病毒感染中的保护作用机制，并解析了TFF2发挥效应的关键分子以及干预的信号转导通路，为TFF2预防与治疗新发突发急性呼吸道传染病重症化奠定理论基础。

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