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

描述(申请人提供)：心脏病毒感染是儿童和成人急性心肌炎最常见的原因之一，并与扩张型心肌病有关。虽然关于病毒性心脏病的细胞免疫反应有相当多的信息，但对感染心肌细胞内有助于宿主防御病毒感染的固有信号机制知之甚少。来自该实验室和其他实验室的研究已经确定心脏中存在一种被称为Toll样受体(TLRs)的先天免疫受体家族。重要的是，最近的研究表明，TLR3和TLR4介导的信号通过称为Toll-IL-1受体(TIR)结构域的适配器诱导干扰素(TRIF)来诱导抗病毒细胞因子的产生。我们在TLR3、TLR4或TRIF缺陷小鼠身上的初步数据表明，TLR3/4 TRIF信号通路对于控制早期病毒复制以及在心脏中最佳地诱导抗病毒反应是必不可少的。基于上述观察，这项提议的直接具体目标将是检验以下假设：(1)通过TLR3和TLR4的信号通过依赖TRIF的途径在肠道病毒感染的小鼠心脏中诱导抗病毒反应，以及(2)TRIF扩增抗病毒反应保护心脏免受细胞病变损伤、左室扩张和心肌收缩能力丧失的影响。设想了四个目标。在特定的目标1中，我们将检验一种假设，即肠道病毒感染后心脏先天抗病毒反应的诱导是由TLR3和TLR4通过TRIF依赖的途径介导的。特异性目标2将验证TLR3/TLR4？TRIF信号的缺失将导致病毒诱导的心脏细胞病变增加，导致左心室扩大和心肌收缩能力丧失的假说。具体目标3将验证这样的假设，即过表达TRIF将保护心肌细胞免受病毒诱导的细胞病变的损害，增强心脏固有的抗病毒反应，并防止与肠道病毒感染相关的左心室扩大和心肌收缩能力丧失的发展。特定目的4将验证TRIF介导的心肌细胞保护是由于TRIF的N-末端和C-末端区域激活不同的抗病毒机制的能力所致的假设。因此，拟议的研究应该提供关于激活机制以及先天性免疫系统(TLR)在病毒性心脏病中的作用的明确的新信息。公共卫生相关性：心脏的病毒感染可能导致儿童和成人严重心力衰竭和死亡。目前还没有针对这种疾病的特效药，患者最终可能需要心脏移植。这笔赠款中提议的研究将使我们更好地了解这种疾病，并可能导致改进的治疗方案。

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.