GENETIC STRUCTURE OF MURINE RETROVIRUSES

鼠逆转录病毒的遗传结构

• 批准号: 3803131
• 负责人: L H EVANS
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3803131
• 关键词: Retroviridae; Retroviridae disease; chemical fingerprinting; cytotoxicity; gene expression; genetic recombination; genetic strain; genetic transcription; laboratory mouse; molecular cloning; monoclonal antibody; mouse leukemia; murine leukemia virus; nucleic acid sequence; oncogenes; oncogenic virus; point mutation; provirus; tissue /cell culture; virus antigen; virus genetics; virus infection mechanism; virus protein; virus replication; virus virus interaction

Many retroviruses undergo genetic alterations in vivo which may affect the viral oncogenicity, cellular tropism, or immune elimination. For example the transforming avian and murine retroviruses have acquired genetic sequences of the host which are directly oncogenic. Murine leukemia viruses (MuLVs) readily undergo recombination with mouse genomic sequences to generate variants which exhibit ah altered host range of infectivity and can activate cellular oncogenic genes. Point mutation of lentiviruses such as the equine infectious anemia virus (EIAV) or the human immunodeficiency virus (HIV) may contribute to the generation of variants which escape the host immune response. The major emphasis of this project is the occurrence and mechanisms of genetic alteration in retroviruses and the consequences of such alterations. In previous studies we have examined the tissue- specific expression of host range variants which are generated after inoculation of an MuLV. Since the generation of such variants results in a mixed infections of viruses with different host ranges, there is a potential for viral pseudotyping to occur in which the genome of one virus is encapsulated in the virion coat of another. We have found a distinct pattern of pseudotyping which correlates with the onset of leukemia in mice infected with the lymphocytic leukemia virus M-MuLV. In both the spleen and thymus, host range variants are completely pseudotyped by the M-MuLV during most of the preleukemic phase of disease. Thus, all virions exhibit the host range of M-MuLV, regardless of which viral genome they contain. Complete pseudotyping persists in the spleen throughout the course of infection. However, in the thymus a high proportion of virions which exhibit the variant host range arise immediately receding the earliest onset of leukemia. Further studies will focus on the relationship of this burst of variant virions to malignant transformation. Studies on the point mutation rate of retroviruses have determined the rate of viable progeny viruses to be approximately 20-fold slower than previous reports. This study is currently being extended to determine the in vivo polymerase error rate for an MuLV. Several proviruses which have undergone a single replication cycle have been molecularly cloned into a vector which allows both direct DNA sequencing as well as in vitro transcription and RNA fingerprinting. Analysis of these clones will yield the first in vivo polymerase error rate determination for a eukaryotic virus. In previous studies numerous monoclonal antibodies (mAb) directed at MuLV antigens have been developed. We have initiated collaborative experiments with Dr. Pincus of the LMSF to construct and test ricin A-chain immunotoxins (IT) for their ability to selectively kill cells infected by MuLVs. Several immunotoxins exhibit cytotoxic activity for infected cells. These include an immunotoxin which exhibits significant cytotoxicity of cells infected with all classes of MuLVs and another immunotoxin which exhibits virtually complete killing of cells infected with a highly neurovirulent MuLV.

许多逆转录病毒在体内经历遗传改变，这可能影响逆转录病毒的功能。 病毒致瘤性、细胞嗜性或免疫消除。 例如 转化的禽类和鼠类逆转录病毒已经获得了遗传学上的 直接致癌的宿主序列。 鼠白血病 病毒（MuLV）容易与小鼠基因组序列进行重组 以产生表现出改变的宿主范围的感染性的变体， 可以激活细胞致癌基因。 慢病毒的点突变， 如马传染性贫血病毒（EIAV）或人类免疫缺陷病毒（HIV）， 病毒（HIV）可能有助于产生逃避免疫缺陷病毒的变异体。 宿主免疫反应 本项目的主要重点是发生 逆转录病毒基因变异的机制及其后果 这样的改变。 在之前的研究中我们检查了组织- 宿主范围变异体的特异性表达， 接种MuLV。 由于这种变体的产生导致 不同宿主范围的病毒混合感染， 病毒假型化的可能性，其中一种病毒的基因组 被包裹在另一个病毒体的外壳中。 我们发现了一个明显的 与小鼠白血病发病相关的假型模式 感染了淋巴细胞白血病病毒M-MuLV。 在两个脾脏 和胸腺，宿主范围变异体被M-MuLV完全假型化 在白血病前期的大部分时间里 因此，所有病毒体都表现出 M-MuLV的宿主范围，无论它们包含哪种病毒基因组。 在整个病程中，脾脏中的完全假型化持续存在。 感染 然而，在胸腺中， 表现出变异寄主范围最早出现， 白血病发作 进一步的研究将集中在这一关系 变异病毒体的爆发到恶性转化。 对逆转录病毒点突变率的研究已经确定了 存活后代病毒的速度比以前慢大约20倍 报道 这项研究目前正在扩大，以确定在体内 MuLV的聚合酶错误率。 几个前病毒已经经历了 单个复制循环已被分子克隆到载体中， 允许直接DNA测序以及体外转录和RNA 指纹识别 对这些克隆的分析将产生第一个体内 真核病毒的聚合酶错误率测定。 在先前的研究中，许多针对MuLV的单克隆抗体（mAb） 已经开发了抗原。 我们已经开始了合作实验 与LMSF的Pincus博士一起构建并测试蓖麻毒素A链 免疫毒素（IT）的能力，选择性地杀死细胞感染 MuLV。 几种免疫毒素对感染的细胞表现出细胞毒活性。 这些包括免疫毒素，其表现出显著的细胞毒性， 感染所有类型MuLV和另一种免疫毒素的细胞， 显示出几乎完全杀死感染了高度 神经毒性MuLV。