Alternative Entry Mechanism for Pathogenic Retroviruses

致病性逆转录病毒的替代进入机制

• 批准号: 7459064
• 负责人: JAMES CUNNINGHAM
• 金额: $ 25.96万
• 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 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7459064
• 关键词: Affinity; Apoptosis; Behavior; Binding; Cells; Complex; Family Felidae; Feline Leukemia Virus; Genetic Recombination; Genome; Human; Immunologic Deficiency Syndromes; In Vitro; Infection; Membrane; Mink Cell Focus-Inducing Viruses; Mus; Numbers; Pathogenesis; Predisposition; Property; Proto-Oncogenes; Proviruses; Receptor Down-Regulation; Recombinants; Regulation; Research Personnel; Retroviridae; Retroviridae Infections; Route; Surface; System; T-Lymphocyte; Virus; Virus Replication; leukemia; receptor; receptor binding; receptor function; recombinant virus

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（申请人提供）：嗜亲性逆转录病毒感染相关的小鼠白血病发病机制的关键步骤是由MCF前病毒的邻近整合引起的myc或其他原癌基因的调节改变（12，30，57）。MCF病毒是激发亲嗜性病毒的基因组与来源于缺陷性内源性前病毒的宿主序列之间重组的产物（27-29，79）。在人类293细胞中的病毒受体功能研究中，我们观察到接触MCF 247病毒的细胞获得的前病毒/细胞比接触非致病性的密切相关逆转录病毒的细胞多20-40倍（85）。我们的研究已经确定了这一观察结果的两种可能的解释：1）MCF 247 env gp的受体结合亲和力显著低于其他病毒（Ka >100 nM），因此在通过受体下调阻断额外感染之前，需要显著更高水平的env gp表达。2)MCF 247病毒独特地适合于通过不依赖于与细胞受体的直接结合的替代机制进入某些细胞。通过这一途径，感染是由MCF 247病毒env gp与嗜亲性病毒的env gp结合触发的，该嗜亲性病毒位于与靶细胞表面膜上的受体的复合物中（85）。这种称为“反式激活”的机制不受MCF 247病毒env gp表达的下调，因此其活性与先前感染（和前病毒插入）的数量无关。我们建议结合使用受体和反式激活依赖性机制提供了MCF 247病毒的选择性优势，超过其他重组病毒，正在进行的亲嗜性病毒复制过程中创建的，并可能解释，部分原因是MCF 247病毒是高度致白血病。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细胞中大量前病毒积累和细胞凋亡引起的严重免疫缺陷相关（25，66）。FeLV-T和MCF 247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感染宿主中准种的内容和性质。迄今为止，我们的反式激活研究主要限于FeLV-T和MCF 247病毒的体外研究。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. 建立一个研究反式激活机制的体外系统。 3. 评估反式激活在逆转录病毒诱导的小鼠白血病发病机制中的作用。