GENETIC STRUCTURE OF MURINE RETROVIRUSES

逆转录病毒经常发生基因改变 通过点突变或通过重组产生变体， 可能表现出不同的感染性和致病性。的 这些变异体的产生及其在致病性中的作用是一个 这个项目的重点。嗜亲鼠感染小鼠 白血病病毒（MuLV）与一个非常 一组密切相关的内源性逆转录病毒env基因序列 以产生多变性病毒。多变性病毒利用不同的 细胞受体，并表现出与亲本不同的宿主范围 亲嗜性MuLV，并已被牵连在诱导一个 增殖性疾病的数量。近交系小鼠品系含有 它们的基因组中有30到40个内源性序列， 与多变性MuLV的env基因同源。我们有 确定这些序列中的至少几个序列参与所述序列。 重组逆转录病毒的产生，然而，它们的参与 显然是非随机的我们最近描述了两个主要的 多嗜性MuLV的抗原亚类，其对应于 与不同的内源序列重组。不同 接种的亲嗜性MuLV始终产生明显不同的 抗原亚类的比例。我们目前的目标之一是 阐明这种选择性的基础。为此，我们定义了 编码核衣壳基因的一个小区域和编码核衣壳基因的一部分， 蛋白酶基因强烈影响的类型多变的 在受感染的小鼠中产生的MuLV。的第二目的 本项目旨在阐明病毒相互作用对 混合逆转录病毒中病毒传播和病理的动力学 感染，例如由遗传性疾病的出现所产生的感染， 变体。假型化和病毒干扰等现象 是混合病毒相互作用的结果，但 这些相互作用赋予组合物的组分协同作用， 感染还不太清楚。我们对混合病毒的初步研究 考虑到嗜亲性和多变性病毒相互作用的感染 Moloney（M）MuLV的白血病发生过程中。这项工作 提出了一个逐步的机制，促进肿瘤发生 伪型和干扰。最近我们的努力 针对的是混合逆转录病毒感染的影响， 共接种嗜亲性和嗜多性MuLV分离株。我们有 发现两种共同接种的病毒之间有惊人的协同作用， 这会导致一种迅速致命的神经系统疾病， 感染后10 - 15天。多变MuLV的水平 与小鼠相比，在共接种小鼠中感染高度升高 单独感染多变性MuLV。这种增强在 复制可能是几乎完全假型化的结果， 嗜亲性病毒粒子内的嗜多性MuLV基因组 感染的过程。多变基因组广泛存在于 在感染后病毒传播的最早时间假型化 在宿主体内的数量是最少的。考虑到伪类型只能 在被两种病毒感染的细胞中发生，这一观察表明 这两种接种的病毒最初感染的是同一个小的 细胞群。检查感染程度和 在病毒可以被识别的最早时间的假型程度 在共同接种的小鼠中检测到， 小种群（<1%）中的嗜亲性和多变性MuLV 外周血细胞。流式细胞仪分析表明，这一群体是 单核细胞/巨噬细胞谱系。

Retroviruses frequently undergo genetic alteration by point mutation or by recombination to generate variants which may exhibit different infectious and pathogenic properties. The generation of these variants and their role in pathogenicity is a major focus of this project. Mice infected with ecotropic murine leukemia viruses (MuLV) recombine with members of a very closely related group of endogenous retroviral env-gene sequences to generate polytropic viruses. Polytropic viruses utilize a different cellular receptor and exhibit a host range distinct from the parental ecotropic MuLV and have been implicated in the induction of a number of proliferative diseases. Inbred mouse strains contain in their genomes 30 to 40 endogenous sequences that are closely homologous to the env genes of polytropic MuLVs. We have determined that at least several of these sequences participate in the generation of recombinant retroviruses, however, their participation is clearly non-random. We have recently described two major antigenic subclasses of polytropic MuLVs which correspond to recombination with distinct endogenous sequences. Different inoculated ecotropic MuLVs consistently yield distinctly different ratios of the antigenic subclasses. One of our current objectives is to elucidate the basis of this selectivity. To this end we have defined a small region encoding the nucleocapsid gene and a portion of the protease gene which strongly influences the types of polytropic MuLVs that are generated in infected mice. A second objective of this project is to elucidate the effects of viral interactions on the dynamics of virus spread and pathology in mixed retrovirus infections such as that generated by the emergence of genetic variants. Phenomena such as pseudotyping and viral interference are consequences of mixed viral interactions, but the potential for these interactions to confer synergism on the components of the infection is not well understood. Our initial studies of mixed virus infections considered ecotropic and polytropic viral interactions during leukemogenesis by Moloney (M) MuLV. This work suggested a stepwise mechanism of oncogenesis facilitated by pseudotyping and interference. Recently our efforts have been directed at the effects of mixed retrovirus infections generated by co-inoculation of ecotropic and polytropic MuLV isolates. We have found a striking synergism between the two co-inoculated viruses, which results in a rapidly fatal neurological disease occurring within 10 to 15 days after infection. The level of the polytropic MuLV infection is highly elevated in co-inoculated mice compared to mice infected with the polytropic MuLV alone. This enhancement in replication is likely the result of nearly complete pseudotyping of the polytropic MuLV genome within ecotropic virions throughout the course of infection. Polytropic genomes are extensively pseudotyped at the earliest times after infection when virus spread in the host is minimal. Considering that pseudotyping can only occur in cells infected by both viruses, this observation indicates that both of the inoculated viruses initially infect the same small population of cells. Examination of the level of infection and the degree of pseudotyping at the earliest times that virus can be detected in co-inoculated mice, revealed a converging infection of the ecotropic and polytropic MuLVs in a small population (<1%) of periferal blood cells. FACS analyses suggest that this population is of the monocyte/macrophage lineage.