Alternative Entry Mechanism for Pathogenic Retroviruses

致病性逆转录病毒的替代进入机制

• 批准号: 6948241
• 负责人: JAMES CUNNINGHAM
• 金额: $ 28.37万
• 依托单位: BRIGHAM AND WOMEN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-10 至 2009-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6948241
• 关键词: MCF7 cell; Retroviridae; feline leukemia /sarcoma virus; genetic susceptibility; laboratory mouse; leukemia virus; molecular oncology; mouse leukemia; murine leukemia virus; pathologic process; polymerase chain reaction; protein binding; receptor expression; viral leukemia; viral leukemogenesis; virus envelope; virus infection mechanism; virus integration; virus protein; virus receptors; virus related neoplasm /cancer; virus replication; western blottings

DESCRIPTION (provided by applicant): A key step in the pathogenesis of leukemia associated with ecotropic retrovirus infection in mice is altered regulation of myc or other proto-oncogenes caused by adjacent integration of an MCF provirus (12, 30, 57). MCF viruses are the product of recombination between the genome of the inciting ecotropic virus and host sequences derived from defective endogenous proviruses (27-29, 79). In studies of virus receptor function in human 293 cells, we observed that cells exposed to MCF247 virus acquired 20-40-fold more proviruses/cell than cells exposed to closely related retroviruses that are not pathogenic (85). Our studies have identified two possible explanations for this observation: 1) The receptor binding affinity of the MCF247 env gp is significantly lower than other viruses (Ka >100 nM) and therefore a substantially higher level of env gp expression is required before additional infection is blocked by receptor down regulation. 2) MCF247 viruses are uniquely suited to gain entry into certain cells through an alternative mechanism that is not dependent on direct binding to a cellular receptor. By this route, infection is triggered by binding of the MCF247 virus env gp to the env gp of an ecotropic virus located in a complex with its receptor on the surface membrane of the target cell (85). This mechanism, termed "trans-activation" is not down regulated by expression of the MCF247 virus env gp and therefore its activity is independent of the number of prior infections (and provirus insertions). We propose the combined use of both receptor and trans-activation-dependent mechanisms provides the MCF247 virus with a selective advantage over other recombinant viruses that are created during ongoing ecotropic virus replication and may explain, in part, why MCF247 virus is highly leukemogenic. In addition, we observe that trans-activation is the sole mechanism of infection by FeLV-T (8), a recombinant feline retrovirus associated with profound immunodeficiency caused by massive provirus accumulation and apoptosis in T cells (25, 66). The behavior of FeLV-T and MCF247 viruses suggests that cooperative interactions between recombinant and inciting viruses may contribute to the content and properties of the quasi-species in an infected host. To date, our studies of trans-activation have been largely limited to FeLV-T and MCF247 viruses in vitro. Our specific aims are to: 1. Determine if susceptibility to trans-activation is a common property of pathogenic MCF viruses. 2. Develop an in vitro system to investigate the mechanism of trans-activation. 3. Assess the contribution of trans-activation to the pathogenesis of retrovirus-induced leukemia in mice.

描述（由申请人提供）：与小鼠亲嗜性逆转录病毒感染相关的白血病发病机制中的一个关键步骤是由 MCF 原病毒的相邻整合引起的 myc 或其他原癌基因的调节改变（12,30,57）。 MCF 病毒是刺激共嗜性病毒的基因组与源自有缺陷的内源原病毒的宿主序列之间重组的产物 (27-29, 79)。在人类 293 细胞病毒受体功能的研究中，我们观察到暴露于 MCF247 病毒的细胞比暴露于密切相关的非致病性逆转录病毒的细胞获得的原病毒数量多 20-40 倍 (85)。我们的研究对此观察结果确定了两种可能的解释：1) MCF247 env gp 的受体结合亲和力显着低于其他病毒 (Ka >100 nM)，因此在受体下调阻断额外感染之前需要显着更高水平的 env gp 表达。 2) MCF247 病毒特别适合通过不依赖于与细胞受体直接结合的替代机制进入某些细胞。通过这种途径，MCF247 病毒 env gp 与亲嗜性病毒的 env gp 结合而触发感染，该病毒位于与其靶细胞表面膜上的受体形成的复合物中 (85)。这种称为“反式激活”的机制不会被 MCF247 病毒 env gp 的表达下调，因此其活性与先前感染（和原病毒插入）的数量无关。我们提出，结合使用受体和反式激活依赖性机制，为 MCF247 病毒提供了优于其他重组病毒的选择性优势，这些重组病毒是在持续的亲嗜性病毒复制过程中产生的，并且可以部分解释为什么 MCF247 病毒具有高度致白血病性。此外，我们观察到反式激活是 FeLV-T 感染的唯一机制 (8)，FeLV-T 是一种重组猫逆转录病毒，与 T 细胞中大量原病毒积累和凋亡引起的严重免疫缺陷相关 (25, 66)。 FeLV-T 和 MCF247 病毒的行为表明，重组病毒和激发病毒之间的合作相互作用可能有助于受感染宿主中准物种的内容和特性。迄今为止，我们对反式激活的研究主要限于体外 FeLV-T 和 MCF247 病毒。我们的具体目标是： 1. 确定对反式激活的敏感性是否是致病性 MCF 病毒的共同特性。 2. 开发体外系统来研究反式激活机制。 3. 评估反式激活对逆转录病毒诱导的小鼠白血病发病机制的贡献。