Molecular mechanism of innate immunity control of HBV replication

描述(申请人提供)：在这项建议中，我们将研究宿主细胞天然免疫抗乙肝病毒(乙肝病毒)的机制。通常情况下，宿主细胞能够通过多个模式识别受体(PRRs)来感知病毒成分，从而激活固有的细胞防御反应来对抗病毒感染。与之形成鲜明对比的是，相当多的证据表明，在大多数情况下，乙肝病毒并不明显地激活这种细胞的先天反应，这可能是病毒发病的核心。这些现象表明，乙肝病毒的感染要么是从先天PRR的检测中悄悄地发现的，要么是有能力阻断先天信号的级联。然而，我们的初步证据表明，通过表达Toll样受体(TLR)的PRR适配器(TLR)、TRIF和MyD88或细胞内Rig-I样螺旋酶(RIH)适配器(IPS-1)而引发的先天免疫反应，显著抑制了人肝细胞来源的细胞系(如HepG2和Huh7)中的乙肝病毒复制。也许最令人惊讶的是，抑制乙肝病毒复制似乎是通过细胞内抗病毒途径(S)，而不是分泌抗病毒细胞因子，如干扰素-1/2。此外，数据表明，这些途径的激活导致HBVmRNAs转录后降解。此外，我们还发现，激活NF-：B通路是三个接头抑制乙肝病毒复制所必需的，而激活额外的途径(S)才能发挥最大的抗病毒作用。拟议的研究将集中在先天免疫反应抑制乙肝病毒复制的分子机制上。具体地说，负责转录后RNA衰退的HBVRNA序列元件将被定位，IPS-1诱导的导致HBVRNA衰退的细胞效应分子将被识别。了解强大而复杂的先天抗病毒途径可能会导致开发新的治疗方法来控制乙肝病毒感染。 与公共卫生相关：乙肝病毒感染是一个严重的公共卫生问题，全世界约有4亿人受到影响。慢性乙肝患者发生肝硬变和肝癌的风险很高。目前批准用于治疗慢性乙型肝炎的药物，包括α干扰素和抑制病毒聚合酶的核(T)类似物，受到不良反应、副作用和出现耐药性的限制。尽管有抗病毒药物，但对于患者来说，建立强大的先天免疫反应是非常重要的，以有效地清除病毒感染。在我们努力了解先天控制乙肝病毒感染的过程中，我们发现虽然乙肝病毒本身并不激活先天免疫信号，但病毒对先天免疫反应中信号级联成分的表达非常敏感。因此，进一步研究乙肝病毒先天控制的分子机制将有助于更好地了解病毒宿主之间的相互作用，并开发新的治疗乙肝的药物。

DESCRIPTION (provided by applicant): In this proposal we will study the antiviral mechanism of host cellular innate immunity against hepatitis B virus (HBV). Generally, host cells are able to sense viral components through multiple pattern recognition receptors (PRRs) that lead to activation of innate cellular defense responses to combat virus infection. In marked contrast, considerable evidence suggests that, for the most part, HBV does not apparently activate such cellular innate response and this is probably central to viral pathogenesis. Such phenomena indicate HBV infection either is stealth from the detection of the innate PRRs, or HBV has ability to block the innate signal cascades. However, our preliminary evidence shows that HBV replication in human hepatocyte-derived cell lines, such as HepG2 and Huh7, is dramatically inhibited by the innate immune response elicited by expression of PRR adaptors for either Toll-like receptors (TLR), TRIF and MyD88, or adaptor for intracellular RIG-I-like helicases (RLH), IPS-1. Perhaps most surprising is that the inhibition of HBV replication appears to be mediated by intracellular antiviral pathway(s), rather than the secretion of antiviral cytokines such as IFN-1/2. Furthermore, the data suggest that activation of these pathways result in the post-transcriptional degradation of HBV mRNAs. Moreover, we found that activation of NF-:B pathway is essential for all three adaptors to inhibit HBV replication and activation of additional pathway(s) is required for TRIF to induce the maximum antiviral effect. The proposed studies will focus on the molecular mechanism by which the innate immune response inhibits HBV replication. Specifically, the HBV RNA sequence elements responsible for the posttranscriptional RNA decay will be mapped, IPS-1-induced cellular effector molecules that lead to the decay of HBV RNAs will be identified. Understanding of the robust and intricate innate antiviral pathway could potentially lead to the development of novel therapeutics to control HBV infections. PUBLIC HEALTH RELEVANCE: Hepatitis B virus (HBV) infection is a severe public health problem affecting about 400 million individuals worldwide. Chronic hepatitis B patients have a high risk of occurrence of hepatocirrhosis and liver cancer. Currently approved drugs for treatment of chronic hepatitis B, including alpha interferon, and nucleos(t)ide analogues inhibiting the viral polymerase, are limited by poor response, side effects and emergence of drug resistance. Despite the antiviral drugs, it is very important for the patient to establish the robust innate and acquire immune response to efficiently purge the virus infection. In our effort to understand the innate control of HBV infection, we found that although HBV itself does not activate innate immunity signaling, however the virus is very sensitive to the innate immune responses elicited by the expression of the signal cascades components. Therefore, further study of the molecular mechanism of the innate control of HBV would lead to the better understanding of the virus host interaction and development of novel therapeutics for treatment of hepatitis B.