Host response to lentiviral infection

猫容易感染逆转录病毒（猫免疫缺陷病毒= FIV），导致猫艾滋病，就像艾滋病毒导致人类艾滋病一样。这两种病毒都感染辅助性T淋巴细胞，诱导免疫缺陷并最终导致宿主死亡。猫感染FIV是唯一自然发生的HIV感染模型，非常适合解决人类难以研究的问题。艾滋病毒感染引起的疾病和死亡仍然是全世界的巨大问题，但迄今为止，艾滋病毒疫苗都失败了。高效抗逆转录病毒疗法对治疗艾滋病毒感染有效，但绝大多数人无法获得。 艾滋病的流行是由几百年前黑猩猩的逆转录病毒传播给人类引起的，很可能是通过与狩猎有关的血液交换。不太为人所知的FIV流行病源于几千年前野猫向家猫传播的逆转录病毒。在理解逆转录病毒疾病方面的一个长期难题是，黑猩猩和野猫的感染不会引起疾病，而人类和猫的感染是致命的。新的知识表明，宿主在接触病毒后立即处理的方式可能对确定免疫缺陷和死亡是否以及多快发生最为重要。暴露后第一天的宿主反应是由先天或预先存在的宿主反应介导的。这种宿主反应的某些成分通常会感知任何病毒并引发炎症反应，而其他因素则会感知特定的病毒，如HIV或FIV。这种病毒特异性宿主“限制因子”在遗传上比其他宿主基因进化得更快，在人类和猫中似乎已经丢失或无效，但在猿和野猫中仍然活跃。 在这项研究中，我们将确定为什么猫不能限制FIV复制。首先，我们检查病毒本身是否包含抑制免疫反应的因子。这将通过产生高度纯化的病毒颗粒，通过质谱分析其蛋白质，搜索数据库以鉴定非病毒蛋白质，并确定这些蛋白质的功能来实现。然后，我们检查宿主体内哪些基因对树突状细胞（这是第一个捕获入侵粘膜的病毒的细胞）和淋巴细胞（这是免疫缺陷发展过程中的主要病毒库）中的炎症刺激做出反应。这些基因将被仔细检查是否可能与FIV相互作用，特别是限制因子中与病毒结合的位点将被详细描述到分子水平。然后，编码限制因子的候选基因将被克隆，它们的蛋白质将在体外产生，然后进行检测以精确确定它们在细胞中的病毒干扰机制。最后，它将解决是否具有较高的细胞因子抑制敏感性的病毒导致较低的病毒负荷和较少的免疫缺陷和疾病的猫。 这些研究旨在确定1）宿主抗FIV因子的存在; 2）它们对FIV生命周期和致病性的重要性; 3）干扰病毒感染的机制;以及4）此类反应与感染结果的相关性。结果将产生广泛适用于了解逆转录病毒宿主适应和进化的见解，并产生新的治疗和预防目标。拟议的研究解决了自然科学中的基本问题，特别是病毒学和免疫学，这可能最终对促进人类健康产生影响。NSERC是这项研究的适当资助机构。

Cats are susceptible to infection with a retrovirus (feline immunodeficiency virus = FIV) that causes AIDS in cats like HIV causes AIDS in humans. Both viruses infect helper T-lymphocytes, induce immunodeficiency and eventually cause death of the host. Infection of cats by FIV is the only naturally occurring model of HIV infection, and very suitable for addressing questions difficult to investigate in humans. Illness and death from infection with HIV remain enormous problems throughout the world, but vaccines against HIV to date have uniformly failed. Highly active anti-retroviral therapy is effective for treating HIV infections, but is not accessible to the vast majority of people. The HIV epidemic arose from transmission of a chimpanzee retrovirus to humans several hundred years ago, most likely through exchange of blood associated with hunting. The lesser-known FIV epidemic arose from transmission of a retrovirus from wild cats to domestic cats several thousand years ago. A long-standing conundrum in understanding of retroviral disease is that infection in chimpanzees and wild cats does not cause disease, while in humans and cats infections are fatal. Knowledge is emerging to indicate that the manner in which the host deals immediately after exposure with the virus is probably most important for determining whether and how quickly immunodeficiency and death will occur. Host responses in the first days after exposure are mediated by innate, or pre-existing, host responses. Some components of this host response generally sense any virus and initiate an inflammatory response, while other factors sense specific viruses such as HIV or FIV. Such virus-specific host "restriction factors" evolve genetically more quickly than other host genes, and appear have become lost or ineffective in humans and cats, but remain active in apes and wild cats. In this research we will determine why cats fail to restrict FIV replication. First, we examine whether the virus itself incorporates factors that suppress immune responses. This will be accomplished by generating highly purified virus particles, analysis of their proteins by mass spectrometry, search of databases to identify the non-viral proteins, and determination of the function of such proteins. We then examine within the host what genes respond to an inflammatory stimulus in dendritic cells (which are the first cells that capture virus invading across mucous membranes) and lymphocytes (which are the main viral reservoir during development of immunodeficiency). These genes will be scrutinized for possible interaction with FIV, and specifically the sites within the restriction factor that bind to virus will be detailed to the molecular level. Then, candidate genes that code for restriction factors will be cloned, their proteins produced in vitro, and then examined to precisely determine their mechanism of viral interference in cells. Finally, it will be resolved whether viruses with higher susceptibility to inhibition by cellular factors cause lower viral burdens and less immunodeficiency and disease in cats. These investigations aim to determine 1) the presence of host anti-FIV factors; 2) their significance to the FIV life cycle and pathogenicity; 3) the mechanisms of interference with viral infection; and 4) the relevance of such responses to outcomes of infection. Results will yield insight widely applicable to understanding of retroviral-host adaptation and evolution, and to generation of new therapeutic and prophylactic targets. The proposed research addresses fundamental questions in the natural sciences, specifically virology and immunology, which may have eventual impact on advancing human health. NSERC is the appropriate funding agency for this research.