Role of Toll-like Receptors 3 and 4 in Viral Heart Disease

描述（由申请方提供）：心脏病毒感染是儿童和成人急性心肌炎最常见的病因之一，并与扩张型心肌病有关。虽然有相当多的关于病毒性心脏病的细胞免疫反应的信息，很少有人知道感染的心肌细胞内的先天信号传导机制，有助于宿主防御病毒感染。该实验室和其他实验室的研究已经确定了心脏中存在一个称为Toll样受体（TLR）的先天免疫受体家族。重要的是，最近的研究表明，TLR 3和TLR 4介导的信号转导有助于通过称为Toll-白细胞介素-1受体（TIR）结构域的衔接子诱导干扰素-γ（TRIF）的衔接子分子诱导抗病毒细胞因子。我们在缺乏TLR 3，TLR 4或TRIF的小鼠中的初步数据显示，TLR 3/4？TRIF信号通路对于控制早期病毒复制以及最佳诱导心脏中的抗病毒应答是必不可少的。基于上述观察结果，本建议的直接具体目标将是测试以下假设：（1）通过TLR 3和TLR 4的信号传导通过TRIF依赖性途径在肠道病毒感染的小鼠的心脏中诱导抗病毒应答，和（2）TRIF放大抗病毒应答保护心脏免受细胞病变损伤、左心室扩张和心肌收缩性丧失。有四个目标。在具体目标1中，我们将测试以下假设：肠道病毒感染后心脏中先天性抗病毒应答的诱导是由TLR 3和TLR 4通过TRIF依赖性途径介导的。具体目标2将测试假设，TLR 3/TLR 4的损失？TRIF信号传导将导致心脏中病毒诱导的细胞病变损伤增加，导致左心室扩张和心肌收缩力丧失。具体目标3将检验以下假设：TRIF的过表达将保护心肌细胞免受病毒诱导的细胞病变损伤，增强心脏中的先天性抗病毒应答，并防止与肠道病毒感染相关的左心室扩张和心肌收缩力丧失的发展。具体目标4将检验TRIF介导的心脏细胞保护作用是由TRIF的N-末端和C-末端区域激活不同抗病毒机制的能力引起的假设。因此，拟议的研究应该提供有关激活机制的明确的新信息，以及先天免疫系统（TLR）在病毒性心脏病中的作用。公共卫生相关性：心脏病毒感染可能导致儿童和成人严重心力衰竭和死亡。这种疾病没有特殊的治疗方法，患者最终可能需要心脏移植。这项补助金中提出的研究将使我们更好地了解这种疾病，并可能导致改善治疗方案。

DESCRIPTION (provided by applicant): Viral infections of the heart are among the most commonly identified causes of acute myocarditis in children and adults and have been implicated in dilated cardiomyopathy. Although there is considerable information regarding the cellular immune response in viral heart disease, little is known about innate signaling mechanisms within the infected cardiac myocyte that contribute to host defense against viral infection. Studies from this and other laboratories have identified the presence of a family of innate immune receptors in the heart termed Toll-like receptors (TLRs). Importantly, recent studies have shown that TLR3 and TLR4 mediated signaling contributes to the induction of anti-viral cytokines through the adaptor molecule termed Toll-interleukin-1 receptor (TIR) domain-containing adaptor inducing interferon-¿ (TRIF). Our preliminary data in mice deficient in TLR3, TLR4 or TRIF show that the TLR3/4?TRIF signaling pathway is essential for the control of early viral replication, as well as the optimal induction of an anti-viral response in the heart. Based upon the foregoing observations the immediate specific objectives of this proposal will be to test the following hypotheses: (1) Signaling through TLR3 and TLR4 induces an anti-viral response in the hearts of enterovirus infected mice through a TRIF-dependent pathway, and (2) TRIF amplification of the antiviral response protects the heart against cytopathic injury, left ventricular dilatation and loss of myocardial contractility. Four Aims are envisioned. In Specific Aim 1 we will test the hypothesis that induction of the innate antiviral response in the heart following enteroviral infection is mediated by TLR3 and TLR4 via a TRIF-dependent pathway. Specific Aim 2 will test the hypothesis that loss of TLR3/TLR4?TRIF signaling will result in increased virus-induced cytopathic injury in the heart, leading to left ventricular dilatation and loss of myocardial contractility. Specific Aim 3 will test the hypothesis that overexpression of TRIF will protect cardiac myocytes from virus-induced cytopathic injury, augment the innate anti-viral response in the heart, and prevent the development of left ventricular dilatation and loss of myocardial contractility associated with an enteroviral infection. Specific Aim 4 will test the hypothesis that the TRIF mediated cardiac cytoprotection results from the ability of the N-terminal and C-terminal regions of TRIF to activate distinct antiviral mechanisms. Thus, the proposed studies should provide definitive new information regarding the mechanisms of activation, as well as the role of the innate immune system (TLRs) in viral heart disease. PUBLIC HEALTH RELEVANCE: Viral infection of the heart may cause severe heart failure and death in children and adults. There is no specific treatment for this disease and patients may eventually require heart transplantation. The studies proposed in this grant will give us a better understanding of the disease and may lead to improved treatment options.