HTLV-1 antagonists of HIV restriction factors

描述(申请人提供)：人类嗜T淋巴细胞病毒I型(HTLV-1)和人类免疫缺陷病毒1型(HIV-1)是在人类中发现的最常见的逆转录病毒。全世界有1,500-2,000万人感染HTLV-1，另有3,000万人感染HIV-1。这两种逆转录病毒主要感染CD4+T淋巴细胞，但它们感染天然免疫反应(树突状细胞)所必需的细胞群的能力不同。如果不加以控制，先天免疫系统的固有手臂会在单细胞水平上阻止逆转录病毒的复制。作为这些细胞内抗逆转录病毒防御的必要对抗策略，逆转录病毒进化出特定的蛋白质来中和这些天然的抑制物。与我们对慢病毒拮抗剂(APOBEC3：VIF；Tetherin/BST2：VPU、Nef和Env；SAMHD1：VPX)的日益增长的知识相反，我们对HTLV-1如何克服这些障碍知之甚少。HTLV-1已经在人类种群中成功传播了数千年，这表明它一定已经进化出有效的策略来绕过宿主限制因素。这项建议旨在确定HTLV-1逃脱慢病毒限制因子APOBEC3、Tetherin/BST2和SAMHD1的身份和潜在机制。我们最近发现APOBEC3家族的几种胞苷脱氨酶能有效地抑制HTLV-1。我们获得的初步证据表明，除了所述的核衣壳介导的A3G从病毒粒子中排除外，还需要其他机制来抵消A3G对HTLV-1的限制。我们将使用野生型和突变型HTLV-1变种来确定哪些结构和非结构基因需要对抗APOBEC3抑制(特定目标1)。将使用病毒和基于细胞的方法相结合的方法来测试这种作用模式。在具体目标2中，我们将使用类似的策略来探索HTLV-1非结构蛋白或结构蛋白是否拮抗人类Tetherin/BST2或SAMHD1限制。对原代人类细胞的结构、功能实验和感染将提供对a)潜在机制和b)沉默这些限制因素的后果的见解。概述的研究将阐明HTLV-1的S对抗策略与慢病毒使用的策略有何不同，并可能为利用这些细胞内抑制物治疗免疫缺陷和恶性肿瘤开辟新的途径。

DESCRIPTION (provided by applicant): Human T-lymphotropic virus type I (HTLV-1) and Human Immunodeficiency virus type 1 (HIV-1) are the most common retroviruses found in humans. Worldwide 15-20 million people are infected with HTLV-1, while another 30 million live with HIV-1. Both retroviruses mainly infect CD4+ T-lymphocytes, but differ with respect to their ability to infect cell populations essential for the generation of innate immune responses (dendritic cells). If left unchecked, the intrinsic arm of the innate immune system blocks retrovirl replication at a single cell level. As a necessary counterstrategy to these intracellular antiretroviral defenses, retroviruses evolved specific proteins to neutralize these natural inhibitors. In contrast to our growing knowledge of lentiviral antagonists (APOBEC3: Vif; Tetherin/BST2: Vpu, Nef and Env; SAMHD1: Vpx), we know very little about how HTLV-1 overcomes these blocks. HTLV-1 has been circulating successfully in human populations for thousands of years suggesting that it must have evolved efficient strategies to bypass host restriction factors. This proposal aims to determine the identity and the underlying mechanisms allowing HTLV-1 to escape from the lentiviral restriction factors APOBEC3, Tetherin/BST2 and SAMHD1. We showed recently that several cytidine deaminase of the APOBEC3 family potently inhibit HTLV-1. We obtained preliminary evidence suggesting that other mechanisms than the described Nucleocapsid-mediated A3G exclusion from virions are required to counteract HTLV-1 restriction by A3G. We will use wild-type and mutant HTLV-1 variants to determine which structural and non-structural genes are required to antagonize APOBEC3 inhibition (Specific Aim 1). The mode of action will be tested using a combination of virus and cell based approaches. In Specific Aim 2 we will use a similar strategy to probe whether HTLV-1 non-structural or structural proteins antagonize human Tetherin/BST2 or SAMHD1 restriction. Structure function experiments and infections of primary human cells will provide insights into a) the underlying mechanisms and b) the consequences of silencing of these restriction factors. The studies outlined will elucidate how HTLV-1's counter-strategies differ from those employed by lentiviruses and will likely open new avenues for harnessing these intracellular inhibitors for treatment of immunodeficiencies and malignancies.