HTLV-1 antagonists of HIV restriction factors

描述（由申请人提供）：人类t淋巴细胞病毒I型（HTLV-1）和人类免疫缺陷病毒1型（HIV-1）是人类最常见的逆转录病毒。全世界有1500万至2000万人感染HTLV-1，另有3000万人感染HIV-1。这两种逆转录病毒主要感染CD4+ t淋巴细胞，但它们感染产生先天免疫应答所必需的细胞群（树突状细胞）的能力不同。如果不加以控制，先天免疫系统的内在臂会在单个细胞水平上阻止逆转录病毒的复制。作为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抑制剂。与我们对慢病毒拮抗剂（APOBEC3: Vif; Tetherin/BST2: Vpu， Nef和Env； SAMHD1: Vpx）的了解不断增加相比，我们对htlv1如何克服这些阻断知之甚少。HTLV-1已经在人群中成功传播了数千年，这表明它必须进化出有效的策略来绕过宿主的限制因素。本研究旨在确定htlc -1的身份和潜在机制，使其能够逃避慢病毒限制性因子APOBEC3、Tetherin/BST2和SAMHD1。我们最近发现APOBEC3家族的几种胞苷脱氨酶能有效抑制HTLV-1。我们获得的初步证据表明，除了上述核衣壳介导的A3G排除病毒粒子之外，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变体来确定需要哪些结构和非结构基因来拮抗APOBEC3抑制（Specific Aim 1）。将使用基于病毒和基于细胞的方法组合来测试作用方式。在Specific Aim 2中，我们将使用类似的策略来探测HTLV-1非结构或结构蛋白是否能拮抗人Tetherin/BST2或SAMHD1限制。结构功能实验和原代人细胞感染将提供以下方面的见解：a)潜在机制和b)沉默这些限制因子的后果。概述的研究将阐明HTLV-1的对抗策略与慢病毒的不同之处，并可能为利用这些细胞内抑制剂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.