TLR13对柯萨奇病毒B3的固有免疫识别与炎症调控及其在病毒性心肌炎发病中的作用与机制

Infections with cardiotropic ssRNA viruses, such as Coxsackievirus B3 (CVB3), can result in myocarditis, dilated cardiomayopathy, and heart failure. Although the virus is directly responsible for some cardiac injury, the majority of the myocarditis is caused by the local host inflammatory response to the virus. Recognition of CVB3 by innate TLR3/4/7/8 and MDA-5 has been reported. Upon that, we speculate that TLR13, a novel and uncharacterized member of the mammalian TLR family reported to be involved in recognition of VSV infection and 23SRNA of certain bacterial, is a novel PRR for CVB3. First, dynamic expression of TLR13 in the heart and intestinal tissue after CVB3 infection is followed. Then in vivo knock down of TLR13 was performed by in vivo-JET PEI to evaluate the intensity of myocarditis induced by CVB3. The molecular mechanism of TLR13-modulation of CVB3-myocarditis is hypothesized to be in stimulation of NF-KB-mediated inflammation and restriction of viral replication by triggering type I Interferon production. Meanwhile, the intestinal innate response induced by CVB3 after entry may have critical influence on the inflammatory cell response chemotaxed to the heart. Our study may provide an important insight into the potential role of a novel TLR-TLR13 in the recognition of CVB3 infection and in the pathogenesis of viral myocarditis. And it may give a clue for the future development of TLR13-based preventive and therapeutic strategies against CVB3 myocarditis.

RNA病毒-B3型柯萨奇病毒（CVB3）感染心肌细胞导致急慢性心肌炎及扩张性心肌病等致死心血管疾病，病毒感染早期诱导的心脏局部固有免疫炎症应答是导致病毒性心肌炎的关键。而介导CVB3感染心脏的固有免疫受体除TLR3/4/7/8/9和MDA-5外，尚有其他PRRs未被阐明。原创性提出TLR13可能是识别肠道病毒CVB3的一类新的固有免疫受体，其识别CVB3激活的NF-KB通路所介导的炎症应答和激活IFNa/b分泌介导的抗病毒应答，与急性病毒性心肌炎的发生发展密切相关；肠道作为CVB3感染的先行部位，其局部诱导的TLR13激活与炎症应答可能通过影响心脏微环境从而促发心肌炎的发生。本课题拟在CVB3病毒性心肌炎小鼠中动态跟踪TLR13表达，并以体内、体外基因敲弱试验证实上述假设。本研究不仅为阐明病毒性心肌炎发病分子机制提出基于TLR13固有免疫调控的新机制，同时为病毒性心肌炎防治提供新分子靶点。

B3型柯萨奇病毒（CVB3）感染心肌细胞导致急慢性心肌炎及扩张性心肌病等心血管疾病，心脏局部早期固有免疫抗病毒炎症应答是致病关键。已报道TLR3/RIG-I/MDA5介导的早期抗病毒固有免疫发挥一定作用，本研究原创性提出TLR13是识别CVB3的新固有免疫受体，其介导的心脏抗病毒应答和炎症应答在急性病毒性心肌炎发挥关键作用。在CVB3病毒性心肌炎小鼠模型中，发现TLR13在心脏最优势上调表达；TLR13敲除小鼠多脏器病毒复制显著增加，致小鼠易感性与死亡率激增；而心脏局部炎症浸润减轻；同时多脏器T细胞、巨噬细胞浸润减少而中性粒细胞浸润增高，伴外周Th1/Th17应答上调。体外试验证实心肌细胞高表达的TLR13识别CVB3后激活IRF7-IFNβ应答发挥早期抗病毒保护作用；而巨噬细胞TLR13则激活NF-KB通路促进心脏局部免疫炎症。心脏TLR13的抗病毒和促免疫炎症的双重功能为首次报道，填补了TLR13抗病毒免疫识别和应答的空白；补充了病毒性心肌炎的早期固有免疫发病机制，同时为病毒性心肌炎的防治提供了基于TLR13分子的免疫防治新靶点。