WOODCHUCK VIRUS--MOLECULAR BIOLOGICAL STUDIES

土拨鼠肝炎病毒(WHV)是一种 在血清学上与乙肝病毒(乙肝)相关。感染 每一种病毒都与急性和慢性有关 各自宿主的肝炎和肝细胞癌； 这些关联在本质上似乎是病因性的。因此， WHV/土拨盘系统提供了一个相关和方便的模型 了解人类感染乙肝病毒的情况。下面的实验 已成功完成：(1)针对WHV的测试 发展了抗原-抗体系统。(2)重组WHV DNA 被转移到易感土拨鼠的肝脏和急性 以及产生慢性WHV感染。(3)经基因改造的西区 带有病毒X基因序列突变的基因组 由重组DNA技术构建。变异病毒基因组 在土拨鼠中是非传染性的，这意味着这些X基因 序列对于病毒复制是必不可少的。(4)超级盘绕 从受感染的肝细胞的细胞核中提取的WHV成功 克隆并测定了完整的核苷酸序列。这个 该复制中间体的序列与 在病毒粒子中发现的部分双链WHV基因组。(5) 另外三个WHV基因组的完整核苷酸序列是 下定决心。似乎WHV的病毒亚型正在进化， 与乙肝病毒表面抗原亚型相似。(6)体内 测定了WHV聚合酶的保真度。突变率 对于WHV复制，发现每次更改少于2 X 10-4 每年的基因组数，这低于 逆转录病毒和其他单链RNA病毒。(7)两个 针对WHV基因组X基因区域的转录本是 被发现了。一份0.65kb的记录被定位到 被感染的肝细胞的细胞核，发现缺乏聚(A) 尾巴在其3‘端。第二个文本，0.80kb长，是 显示为0.65kb转录本的多聚腺苷化版本。

The woodchuck hepatitis virus (WHV) is taxonomically and serologically related to the hepatitis B virus (HBV). Infection with each of these viruses is associated with acute and chronic hepatitis and hepatic cell carcinoma in their respective hosts; these associations appear to be etiological in nature. Thus, the WHV/woodchuck system provides a relevant and convenient model for understanding HBV infections of humans. The following experiments were successfully completed: (1) Tests specific for the WHV antigen-antibody systems were developed. (2) Recombinant WHV DNA was transfected into the liver of susceptible woodchucks and acute and chronic WHV infections produced. (3) Genetically altered WHV genomes, with mutations in the virus X gene sequence, were constructed by recombinant DNA techniques. Mutant virus genomes were non-infectious in woodchucks, which implied that these X gene sequences were essential for virus replication. (4) Supercoiled WHV, from the nucleus of infected liver cells, was successfully cloned and the complete nucleotide sequence determined. The sequence of this replicative intermediate is identical to that of the partially double stranded WHV genome found in virions. (5) The complete nucleotide sequence of three additional WHV genomes was determined. It appears that virus subtypes of WHV are evolving, analogous to the surface antigen subtypes of HBV. (6) The in vivo fidelity of the WHV polymerase was determined. The mutation rate for WHV replication was found to be less than 2 X 10-4 changes per genome per year, which is lower than the mutation rate of retroviruses and other single strand RNA viruses. (7) Two transcripts specific for the X gene region of the WHV genome were discovered. One transcript, 0.65 kb in length, was localized to the nucleus of infected liver cells, and found to lack a poly(A) tail at its 3' end. The second transcript, 0.80 kb in length, was shown to be the poly-adenylated version of the 0.65 kb transcript.