STRUCTURE AND REPLICATION OF HEPATITIS DELTA VIRUS

丁型肝炎病毒（HDV）是B肝炎病毒（HBV）的卫星病毒， 增加与HBV感染相关的肝损伤， 进展为肝细胞癌的相关风险。远程 这些研究的目的是了解的结构和复制 HDV提出了六个目标。 I.初步研究了天然和 组装的病毒粒子和病毒核糖核蛋白的分离， 病毒体和受感染细胞的细胞核。建议：（一） 研究病毒体和核RNP，化学计量和 δ抗原之间相关相互作用的特异性， HDV RNA，和（ii）扩展研究，考虑之间的相互作用 δ抗原和嗜肝DNA病毒表面抗原，它们必须存在于 在病毒体装配过程中的细胞质。 二. RNA指导的HDV RNA转录可能被认为是通过 宿主RNA聚合酶II的重定向。初步研究表明， 核提取物可转录HDV RNA。建议：（一） 表征新生RNA的起始位点，（ii）评估 启动RNA引导的RNA所需的序列或结构 合成，（iii）研究δ抗原结合的作用，如果有的话， 模板RNA，和（iv）比较和对比所需转录因子 对于RNA-相对于通过pol II的DNA指导的RNA合成。 三.最初的研究表明，在受感染的细胞内， HDV RNA基因组上的核苷酸经历了一个重要的后 转录RNA编辑事件。反应可以在 使用核提取物进行体外培养。建议（i）界定这些特征 编辑所需的HDV基因组RNA，（ii）研究 改变核苷酸的机制，以及（iii）评估 假设RNA修饰活性与普遍存在的 细胞酶CTP合成酶 四. HDV相关的发病机制将研究与土拨鼠和在一个 新动物系统最初的研究表明，将HDV注射到 小鼠导致肝细胞中的单循环复制。是 建议在（i）中研究HDV感染的启动和清除 土拨鼠和小鼠，在没有WHV的情况下，（ii）在具有特异性 免疫缺陷，和（iii）嗜肝DNA病毒转基因小鼠 包膜蛋白 诉小鼠可以通过注射到尾部或尾部感染HDV。 静脉或腹膜腔。为了了解这一机制， 感染，建议（i）确定HDV是否可以感染 易感非肝细胞作为最终感染之前的步骤， 复制在肝细胞中，（ii）发现是否WHV也可以感染 小鼠，并且如果是，（iii）检查与HDV和WHV两者的共感染。 六.需要进一步的研究来了解小形式的 δ抗原支持基因组复制。建议（一）测试 通过特异性突变和/或 HDV基因组的截短形式，以及（ii）追求新发现的 δ抗原的小和大形式的性质：稳定性 HDV基因组的复制和非复制形式。

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.