Molecular mechanism of innate immunity control of HBV replication

描述（由申请人提供）：在本提案中，我们将研究宿主细胞先天免疫抗B型肝炎病毒（HBV）的抗病毒机制。通常，宿主细胞能够通过多种模式识别受体（PRR）来感知病毒组分，所述模式识别受体（PRR）导致先天细胞防御反应的激活以对抗病毒感染。与此形成鲜明对比的是，大量证据表明，在大多数情况下，HBV并不明显激活这种细胞先天性反应，这可能是病毒发病机制的核心。这些现象表明HBV感染要么是从先天PRR的检测中隐身的，要么HBV具有阻断先天信号级联的能力。然而，我们的初步证据表明，HBV在人肝细胞衍生的细胞系，如HepG 2和Huh 7中的复制被先天免疫应答显著抑制，所述先天免疫应答由Toll样受体（TLR）的PRR衔接子（TRIF和MyD 88）或细胞内RIG-I样解旋酶（RLH）的衔接子（IPS-1）的表达引起。也许最令人惊讶的是，HBV复制的抑制似乎是由细胞内抗病毒途径介导的，而不是抗病毒细胞因子如IFN-1/2的分泌。此外，数据表明，这些途径的激活导致HBV mRNA的转录后降解。此外，我们发现NF-：B途径的激活对于所有三种衔接子抑制HBV复制是必需的，并且TRIF诱导最大抗病毒效果需要另外的途径的激活。拟议的研究将集中在先天免疫反应抑制HBV复制的分子机制。具体而言，将绘制负责转录后RNA衰变的HBV RNA序列元件，将鉴定导致HBV RNA衰变的IPS-1诱导的细胞效应分子。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HBV感染。 公共卫生相关性：B型肝炎病毒（HBV）感染是一个严重的公共卫生问题，影响全球约4亿人。慢性B型肝炎患者发生肝硬化和肝癌的风险很高。目前批准的用于治疗慢性B型肝炎的药物，包括α干扰素和抑制病毒聚合酶的核苷（酸）类似物，受到反应差、副作用和出现耐药性的限制。尽管有抗病毒药物，但患者建立强大的先天性和获得性免疫应答以有效清除病毒感染是非常重要的。在我们努力理解HBV感染的先天控制中，我们发现尽管HBV本身不激活先天免疫信号传导，但是病毒对由信号级联组分的表达引起的先天免疫应答非常敏感。因此，深入研究HBV先天控制的分子机制将有助于更好地理解病毒与宿主的相互作用，并有助于开发治疗B型肝炎的新药物。

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.