HIV Coreceptor Switching

项目概述-本研究计划解决与HIV包膜糖蛋白gp120的共受体使用有关的两个问题。首先是在初次感染时有利于使用ccr5的（R5） HIV-1传播的选择性压力。这些研究对于确定围绕传播的选择压力具有重要意义，对于疫苗开发和CCR5抑制剂在杀微生物剂中的潜在使用具有重要意义。我们将对一系列主要传播包膜克隆进行表征，然后用它们来验证两个假设：(1)传播的病毒在传播的生理条件下更稳定；(2)选择性感染骨髓树突状细胞有利于R5病毒的传播。第二个问题涉及选择性力量，这种力量允许50%的患者在长期感染后出现使用cxcr4的病毒。我们将描述从早期到晚期感染的一系列包膜的纵向特征，并用它们来检验四个额外的假设：(1)共受体转换的可能性受到包膜进化到参与CCR5不同细胞外结构域的方式的影响；(2)使用cxcr4的变体（R5X4或X4病毒）仅在抗体对包膜反应消失时出现；(3)在一些患者中，R5病毒的进化达到了适应度上限，随后突然丧失适应度，从而允许X4病毒变体在没有竞争的情况下出现；(4)与硫代糖胺聚糖的结合促进了辅受体的转换。负责这些功能变化的包络序列将被映射。这些实验与即将在III期临床试验中使用CCR5抑制剂高度相关，并且可以很好地预测对这类抗病毒药物的耐药概率。

DESCRIPTION (provided by applicant): Project Summary - This research plan addresses two issues relating to coreceptor use by the HIV envelope glycoprotein gp120. The first is the selective pressures that favor transmission of CCR5-using (R5) HIV-1 at the time of primary infection. These studies are important for defining the selection pressures surrounding transmission and are of great importance for vaccine development and the potential use of CCR5 inhibitors in microbicides. We will characterize a series of primary transmission envelope clones, and then use them to test two hypotheses: (1) that transmitted virus is more stable under the physiological conditions of transmission, and (2) that selective infection of myeloid dendritic cells favors R5 virus transmission. The second issue addresses the selective forces that allow emergence of CXCR4-using viruses in 50% of patients after prolonged infection. We will characterize a longitudinal series of envelopes from early to end- stage infection and use them to test four additional hypotheses: (1) that the probability of coreceptor switching is influenced by the way in which envelope evolves to engage different extracellular domains of CCR5; (2) that CXCR4-using variants (R5X4 or X4 viruses) only emerge when antibody responses to envelope disappear; (3), that evolution of R5 viruses reaches a fitness ceiling in some patients that is followed by an abrupt loss of fitness that allows X4 viral variants to emerge without competition; and (4), that binding to sulfated glycosaminoglycans promotes coreceptor switching. The envelope sequences responsible for these functional changes will be mapped. These experiments are highly relevant to the approaching use of CCR5 inhibitors in phase III clinical trials, and may well predict the probability of resistance to this class of antivirals.