Lentiviral Resistance to Tetherin

描述（由申请人提供）：Tetherin （BST-2或CD317）是一种干扰素诱导的跨膜蛋白，可抑制病毒从感染细胞中释放。大多数猿类免疫缺陷病毒（siv）在非人灵长类宿主中使用Nef来克服拴链蛋白的限制，而HIV-1 Vpu和HIV-2 Env已经进化到在人类中发挥这一功能，因为人类拴链蛋白的细胞质结构域中缺乏赋予Nef易感性的序列。我们最近在恒河猴中发现了gp41细胞质尾部的代偿性变化，这种变化在一种网络缺失的SIV毒株中恢复了对tetherin的抗性，这种毒株在恒河猴中恢复了致病表型。这些观察结果类似于HIV-2 Env对人类tetherin的拮抗的适应性，并暗示对tetherin的抗性对慢病毒的发病机制很重要。我们现在已经确定了HIV-1 Nef等位基因，能够抵消人类绳链蛋白的限制，强调了灵长类慢病毒在适应宿主绳链蛋白方面的非凡可塑性，并揭示了Nef在HIV-1感染中以前未被认识到的作用。本提案中概述的研究建立在这项工作的基础上，以揭示慢病毒对tetherin的耐药性的基本机制及其在免疫缺陷病毒感染中的作用。我们的第一个目标（目的1）是确定Nef拮抗tetherin的分子相互作用和细胞运输途径，以及siv感染细胞中tetherin的命运（降解与隔离）。这些研究将建立在我们小组的工作基础上，确定Nef是SIV的病毒基因产物，可以抵消tetherin的限制，并将更好地理解慢病毒对tetherin的抗性机制。我们的第二个目标（目标2）是确定与HIV-1 Nef获得抗系绳蛋白活性相关的遗传变化，以及HIV-1 Nef抵消人类系绳蛋白的机制。这些研究对于确定原代HIV-1分离株的Nef等位基因抗系绳蛋白活性的广泛程度，导致HIV-1 Nef获得这种功能的情况，以及HIV-1 Nef与SIV Nef在系绳蛋白拮抗方面的机制差异具有重要意义。我们的第三个目标（目标3）是评估原代HIV-2 Ev蛋白抗栓蛋白活性的自然变化，并确定这种活性所需的Env序列。这些研究将揭示原代HIV-2 Env蛋白抗tetherin活性的普遍性/范围，以及Env中促成这种活性的分子适应。通过比较进展性HIV-2感染个体的Env等位基因活性与含有病毒复制的无症状个体的Env等位基因活性，这些研究将揭示tetherin拮抗剂的差异是否与HIV-2发病机制的差异有关。

DESCRIPTION (provided by applicant): Tetherin (BST-2 or CD317) is an interferon-inducible transmembrane protein that inhibits virus release from infected cells. Whereas most simian immunodeficiency viruses (SIVs) use Nef to overcome restriction by tetherin in their non-human primate hosts, HIV-1 Vpu and HIV-2 Env have evolved to serve this function in humans due to the absence of sequences in the cytoplasmic domain of human tetherin that confer susceptibility to Nef. We recently identified compensatory changes in the cytoplasmic tail of gp41 that restore resistance to tetherin in a nef-deleted strain of SIV that regained a pathogenic phenotype in rhesus macaques. These observations are analogous to the adaptation of HIV-2 Env for antagonism of human tetherin and imply that resistance to tetherin is important for lentiviral pathogenesis. We have now identified HIV-1 Nef alleles that are able to counteract restriction by human tetherin, underscoring the extraordinary plasticity of the primate lentiviruses in adapting to the tetherin proteins of their hosts and revealing a previously unappreciated role for Nef in HIV-1 infection. The studies outlined in this proposal build on this work to reveal the fundamental mechanisms of lentiviral resistance to tetherin and their role in immunodeficiency virus infection. Our first objective (Aim 1) is to define the molecular interactions and cellular trafficking pathways involved in tetherin antagonism by Nef, and the fate of tetherin (degradation versus sequestration) in SIV-infected cells. These studies will build on work by our group identifying Nef as the viral gene product of SIV that counteracts restriction by tetherin and will lead to a better understanding of the mechanisms of lentiviral resistance to tetherin. Our second objective (Aim 2) is define the genetic changes associated with the gain of anti-tetherin activity by HIV-1 Nef and the mechanism by which HIV-1 Nef counteracts human tetherin. These studies are important for determining how widespread anti-tetherin activity is for Nef alleles of primary HIV-1 isolates, the circumstances that lead to the gain of this function by HIV-1 Nef, and the mechanistic differences in tetherin antagonism by HIV-1 Nef versus SIV Nef. Our third objective (Aim 3) is to assess the natural variation in anti- tetherin activity for primary HIV-2 Ev proteins and to define the sequences in Env required for this activity. These studies will reveal the prevalence/range of anti-tetherin activity for primary HIV-2 Env proteins and the molecular adaptations in Env that contribute to this activity. By comparing the activity of Env alleles derived from individuals with progressive courses of HIV-2 infection to Env alleles derived from asymptomatic individuals who contain virus replication, these studies will reveal whether differences in tetherin antagonism are related to differences in HIV-2 pathogenesis.