STRUCTURE AND REPLICATION OF HEPATITIS DELTA VIRUS

丁型肝炎病毒(HDV)是乙肝病毒(乙肝)的卫星病毒，可以 增加与乙肝病毒感染相关的肝脏损害， 进展为肝细胞癌的相关风险。长距离的 这些研究的目标是了解基因的结构和复制 HDV。提出了六个目标。 一、对天然和天然的结构进行了初步研究 组装的病毒粒子和从两者分离的病毒核糖核蛋白 病毒粒子和受感染细胞的细胞核。现建议(I) 研究病毒粒子和核RNPs，化学计量和 Delta抗原和Delta抗原之间相关相互作用的特异性 HDV RNA，以及(Ii)扩展研究以考虑 德尔塔抗原和肝炎病毒表面抗原必须出现在 病毒粒子组装过程中的细胞质。 II.RNA引导的HDV RNA转录可能是通过 宿主RNA聚合酶II的重定向。初步研究表明 核抽提物可以转录HDV RNA。现建议(I) 描述新生RNA的起始点，(Ii)评估 RNA引导的RNA起始所需的序列或结构 合成，(3)调查结合的三角洲抗原的作用，如果有的话 模板RNA，以及(Iv)比较所需的转录因子 对于RNA-相对于由PolII进行的DNA指导的RNA合成。 初步研究表明，在受感染的细胞内，特定的 HDV RNA基因组上的核苷酸经历了一个必要的后 转录RNA编辑事件。该反应可以在 使用核提取液进行体外培养。建议(I)定义这些特征 编辑所需的HDV基因组RNA中，(Ii)调查 核苷酸改变的机制，以及(Iii)评估 假设RNA修饰活性与无处不在的 细胞酶、CTP合成酶。 IV.将用土拨鼠和一个 新的动物系统。初步研究表明，将HDV注射到 小鼠导致肝细胞的单一复制周期。它是 建议研究HDV感染的起始和清除(I) 土拨鼠和小鼠，在没有WHV的情况下，(Ii)在具有特异性的小鼠中 免疫缺陷，以及(Iii)转Hepadna病毒小鼠 包膜蛋白。 小鼠可以通过尾巴注射感染HDV 静脉或腹膜腔。要了解这一现象的机制 感染建议：(I)确定HDV是否能感染 作为最终感染前的一个步骤的易感非肝细胞 在肝细胞中复制，(Ii)研究WHV是否也能感染 小鼠，如果是，(Iii)检查与HDV和WHV的混合感染。 需要进一步的研究来了解这种小形式的 Delta抗原支持基因组复制。建议(一)测试 必要的顺式作用RNA序列通过特定突变和/或 HDV基因组的截短形式，以及(Ii)追求新发现的 小型型和大型型Delta抗原的性质：稳定性 复制和非复制形式的HDV基因组。

Hepatitis delta virus (HDV), a satellite of hepatitis B virus (HBV), can increase the liver damage associated with HBV infections and the associated risk of progressing to hepatocellular carcinoma. The long-range goal of these studies is to understand the structure and replication of HDV. Six aims are proposed. I. Initial studies have been made of the structure of natural and assembled virions and of the viral ribonucleoproteins isolated both from virions and from the nuclei of infected cells. It is proposed to (i) investigate for both virion and nuclear RNPs, the stoichiometry and specificity of the relevant interactions between the delta antigens and the HDV RNA, and (ii) extend the study to consider interactions between the delta antigens and hepadnavirus surface antigens which must occur in the cytoplasm during virion assembly. II. RNA-directed transcription of HDV RNA probably is thought to via redirection of the host RNA polymerase II. Initial studies have shown that nuclear extracts can transcribe HDV RNAs. It is proposed to (i) characterize the initiation sites of the nascent RNAs, (ii) assess sequences or structures needed for the initiation of RNA-directed RNA synthesis, (iii) investigate the role, if any, of delta antigens bound to template RNA, and (iv) compare and contrast transcription factors needed for RNA- relative to DNA-directed RNA synthesis by pol II. III. Initial studies have shown that inside an infected cell, a specific nucleotide on the genome of HDV RNA undergoes an essential post- transcriptional RNA-editing event. The reaction can be reconstituted in vitro using nuclear extracts. It is proposed to (i) define those features of the HDV genomic RNA that are needed for editing, (ii) investigate the mechanism by which the nucleotide is changed, and (iii) evaluate the hypothesis that the RNA modifying activity is related to an ubiquitous cellular enzyme, CTP synthetase. IV. HDV-associated pathogenesis will be studied with woodchucks and in a new animal system. Initial studies have shown that injection of HDV into the mouse leads to a single cycle of replication in hepatocytes. It is proposed to study initiation and clearance of HDV infections in (i) woodchucks and mice, in the absence of WHV, (ii) in mice with specific immune deficiencies, and (iii) in mice transgenic for hepadnavirus envelope proteins. V. The mouse can be infected with HDV by an injection into either the tail vein or the peritoneal cavity. To understand the mechanism of this infection it is proposed to (i) determine whether HDV can infect a susceptible non-liver cell as a step prior to ultimate infection and replication in hepatocytes, (ii) to find whether WHV can also infect the mouse, and if so, (iii) to examine coinfections with both HDV and WHV. VI. Further studies are needed to understand how the small form of the delta antigen supports genome replication. It is proposed (i) to test for essential cis-acting RNA sequences via specifically mutated and/or truncated forms of the HDV genome, and (ii) to pursue a newly-discovered property of both small and large forms of the delta antigen: stabilization of replicating, and non-replicating forms of the HDV genome.