Lentiviral Resistance to Tetherin

描述（由申请人提供）：Tetherin（BST-2或CD 317）是一种干扰素诱导型跨膜蛋白，可抑制病毒从感染细胞中释放。尽管大多数猿免疫缺陷病毒（SIV）使用Nef来克服其非人灵长类宿主中的系链蛋白的限制，但由于人类系链蛋白的胞质结构域中缺乏赋予Nef易感性的序列，HIV-1 Vpu和HIV-2 Env已经进化为在人类中发挥这种功能。我们最近确定了gp 41细胞质尾部的补偿性变化，该变化恢复了对SIV nef缺失株系栓蛋白的抗性，该SIV在恒河猴中恢复了致病表型。这些观察结果类似于HIV-2 Env对人系链蛋白的拮抗作用的适应，并暗示对系链蛋白的抗性对于慢病毒发病机制是重要的。我们现在已经确定了HIV-1 Nef等位基因，这些等位基因能够抵消人类tetherin的限制，强调了灵长类慢病毒在适应宿主tetherin蛋白方面的非凡可塑性，并揭示了Nef在HIV-1感染中以前未被重视的作用。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耐药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（Aim 1）是确定分子相互作用和细胞运输途径参与拴系蛋白拮抗Nef，和拴系蛋白的命运（降解与隔离）在SIV感染的细胞。这些研究将建立在我们小组确定Nef为SIV的病毒基因产物的工作基础上，该病毒基因产物抵消了tetherin的限制，并将导致更好地理解慢病毒对tetherin的耐药性机制。我们的第二个目标（Aim 2）是确定与HIV-1 Nef获得抗tetherin活性相关的遗传变化以及HIV-1 Nef抵消人类tetherin的机制。这些研究对于确定主要HIV-1分离株的Nef等位基因的抗栓蛋白活性有多广泛、导致HIV-1 Nef获得这种功能的情况以及HIV-1 Nef与SIV Nef在栓蛋白拮抗作用中的机制差异非常重要。我们的第三个目标（目标3）是评估主要HIV-2 Ev蛋白的抗束缚素活性的自然变异，并定义该活性所需的Env序列。这些研究将揭示主要HIV-2 Env蛋白的抗栓蛋白活性的普遍性/范围以及Env中有助于该活性的分子适应性。通过比较来自HIV-2感染进行性病程个体的Env等位基因与来自包含病毒复制的无症状个体的Env等位基因的活性，这些研究将揭示系链蛋白拮抗作用的差异是否与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.