Lentiviral Resistance to Tetherin

描述(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。虽然大多数猴免疫缺陷病毒(SIV)使用Nef来克服其非人类灵长类宿主中Tetherin的限制，但由于人类Tetherin细胞质区域中缺乏赋予Nef易感性的序列，HIV-1 VPU和HIV-2 Env已进化为在人类中提供这一功能。我们最近发现了gp41胞浆尾部的代偿性变化，这些变化恢复了猕猴对nef缺失的SIV菌株的耐受，该菌株在猕猴中重新获得了致病表型。这些观察结果类似于HIV-2Env对人类Tetherin的拮抗作用，并暗示对Tetherin的抵抗在慢病毒致病中是重要的。我们现在已经确定了能够对抗人类Tetherin限制的HIV-1Nef等位基因，这突显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感染中以前未被认识到的作用。这项建议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的抗性及其在免疫缺陷病毒感染中的作用。我们的第一个目标(目标1)是确定Nef参与Tetherin拮抗的分子相互作用和细胞运输途径，以及Tetherin在SIV感染细胞中的命运(降解与隔离)。这些研究将建立在我们团队工作的基础上，确定Nef是SIV的病毒基因产物，可以抵消Tetherin的限制，并将导致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)是定义与HIV-1Nef获得的抗Tetherin活性相关的遗传变化，以及HIV-1Nef抵消人类Tetherin的机制。这些研究对于确定HIV-1主要分离株的Nef等位基因的抗栓酶活性的广泛性，导致HIV-1Nef获得这一功能的情况，以及HIV-1Nef和SIV Nef在Tetherin拮抗机制上的差异具有重要意义。我们的第三个目标(目标3)是评估主要HIV-2 EV蛋白的抗栓酶活性的自然变异，并确定这一活动所需的Env序列。这些研究将揭示主要HIV-2包膜蛋白的抗栓酶活性的盛行率/范围，以及促成这一活性的包膜蛋白的分子适应。通过比较来自HIV-2进行性感染个体的Env等位基因的活性和来自无症状的包含病毒复制的个体的Env等位基因的活性，这些研究将揭示Tetherin拮抗的差异是否与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.