'IMMATURE SECRETION' VARIANTS OF HUMAN HEPATITIS B VIRUS

我们的长期目标是了解病毒性肝炎的病理生物学。乙肝病毒是世界上第四大人类最常见的感染源。慢性乙肝病毒感染与肝癌的发生发展密切相关。乙肝病毒慢性感染的发病机制及其发病机制仍有待深入研究。最近，有越来越多的证据表明，随着肝病的进展，患者体内存在的遗传变异可能会影响乙肝病毒的慢性化。自从聚合酶链式反应技术发明以来，人们已经报道了许多乙肝病毒的序列变异。然而，在对HBV变异体的研究中，一个共同的障碍是，大多数已报道的序列变异体没有已知的功能意义，也没有表现出与野生型病毒明显不同的强烈表型。在全球慢性携带者(83%的肝癌患者)中，在乙肝核心抗原中发现的最常见的错义突变发生在第97位密码子上。我们最近对该突变体的功能鉴定发现了一种新的和强大的表型，被称为“未成熟分泌”表型。与野生型乙肝病毒不同，97密码子突变体分泌的Dane颗粒主要包含未成熟形式的HBVDNA基因组(低分子量)。在这个应用中，我们建议：1)将我们对“未成熟分泌物”现象的观察从组织培养扩展到患者和动物模型。我们还试图将“未成熟分泌”表型扩展到其他流行于不同地理位置的病毒亚型。2)从遗传和生化两个方面探讨“未成熟分泌”的机制。需要检验的几个假设之一是，“未成熟的分泌”可能是由野生型包膜和突变的核心蛋白之间的高效相互作用造成的。3)通过体外感染试验，比较高频率密码子97突变株和野生型乙肝病毒的传染性。这项工作的成功完成将有助于理解控制乙肝病毒形态发生和病毒粒子分泌的基本规则，以及对慢性病毒性肝炎和许多其他慢性进行性病毒疾病的重要影响。

Our long-term goal is to understand the pathobiology of viral hepatitis. Hepatitis B virus (HBV) is the 4th most common infectious agent in humans worldwide. Chronic infection with HBV is tightly associated with the development of liver cancer. The mechanism of how HBV chronic infection is established and its pathogenesis remains to be fully explored. Recently, there has been increasing evidence that HBV chronicity may be influenced by the presence of genetic variants that evolve in patients as liver disease progresses. Since the invention of polymerase chain reaction technology, many HBV sequence variants have been reported. However, a common frustration in the research of HBV variants is that the majority of these reported sequence variants has no known functional significance and does not exhibit a strong phenotype distinctively different from the wild type virus. The most frequent missense mutation found in the HBV core antigen occurs at codon 97 in chronic carriers worldwide (in 83 percent hepatoma patients). Our recent functional characterization of this mutant uncovered a novel and strong phenotype, dubbed an "immature secretion" phenotype. Unlike wild type HBV, the secreted Dane particles of codon 97 mutants contain predominantly the immature form (lower molecular weight) of the HBV DNA genome. In this application, we propose 1) to extend our observation of the "immature secretion" phenomenon from tissue culture to patients and animal models. We also attempt to extend the "immature secretion" phenotype to other viral subtypes prevalent in different geographic locations. 2) to investigate the mechanism of "immature secretion" by both genetic and biochemical approaches. One of the several hypotheses to be tested is that "immature secretion" could be caused by hyper-efficient interactions between wild type envelope and mutant core proteins. 3) Finally, we will compare the infectivity of the highly frequent codon 97 mutants and wild type HBV via in vitro infection assays. Successful completion of this work will help understand the fundamental rules governing HBV morphogenesis and virion secretion, in addition to the important implications for chronic viral hepatitis as well as many other chronic progressive viral diseases.