Host response to lentiviral infection

猫很容易感染逆转录病毒(猫免疫缺陷病毒)，这种病毒会引起猫的艾滋病，就像艾滋病毒会引起人类的艾滋病一样。这两种病毒都会感染辅助T淋巴细胞，导致免疫缺陷，最终导致宿主死亡。猫被FIV感染是唯一自然发生的艾滋病毒感染模式，非常适合于解决人类难以调查的问题。感染艾滋病毒的疾病和死亡在世界各地仍然是巨大的问题，但迄今为止，针对艾滋病毒的疫苗都失败了。高度有效的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。艾滋病毒的流行源于数百年前黑猩猩逆转录病毒向人类的传播，很可能是通过与狩猎有关的血液交换。鲜为人知的FIV疫情源于数千年前从野猫向家猫传播的逆转录病毒。长期以来，对逆转录病毒疾病的理解一直是一个难题，即黑猩猩和野猫的感染不会导致疾病，而人类和猫的感染是致命的。新出现的知识表明，宿主在接触病毒后立即处理的方式可能对确定是否以及以多快的速度发生免疫缺陷和死亡可能是最重要的。暴露后最初几天的宿主反应是由先天或预先存在的宿主反应调节的。这种宿主反应的一些成分通常可以感知任何病毒并启动炎症反应，而其他因素则可以感知特定的病毒，如HIV或FIV。这种病毒特有的宿主“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，但在猿猴和野猫中仍然活跃。在这项研究中，我们将确定为什么猫无法限制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素。这将通过产生高度纯化的病毒颗粒、用质谱仪分析它们的蛋白质、搜索数据库以识别非病毒蛋白质以及确定这些蛋白质的功能来实现。然后，我们在宿主内检查树突状细胞(它们是第一个捕获跨越粘膜入侵的病毒的细胞)和淋巴细胞(它们是免疫缺陷发展过程中的主要病毒库)中的哪些基因对炎症刺激做出反应。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置将在分子水平上得到详细说明。然后，编码限制因子的候选基因将被克隆，它们的蛋白质在体外产生，然后进行检查，以准确地确定它们在细胞中的病毒干扰机制。最后，对细胞因素抑制敏感性较高的病毒是否会导致猫的病毒负担较低，免疫缺陷和疾病较少，这一问题将得到解决。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意义；3)干扰病毒感染的机制；以及4)这种反应与感染结果的相关性。结果将产生广泛适用于理解逆转录病毒宿主适应和进化的洞察力，以及产生新的治疗和预防靶点。这项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，这些问题可能最终会对促进人类健康产生影响。NSERC是这项研究的合适资助机构。

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.