HIV Coreceptor Switching

描述(由申请人提供)：项目摘要-本研究计划解决与艾滋病毒包膜糖蛋白gp120使用共受体有关的两个问题。首先是选择压力，这种压力有利于在初次感染时使用(R5)HIV-1传播CCR5。这些研究对确定围绕传播的选择压力很重要，对疫苗开发和CCR5抑制剂在杀微生物剂中的潜在使用也非常重要。我们将对一系列初级传播包膜克隆进行表征，然后用它们来检验两个假设：(1)传播的病毒在传播的生理条件下更稳定，(2)选择性感染髓系树突状细胞有利于R5病毒的传播。第二个问题涉及选择性因素，使50%的患者在长期感染后出现使用CXCR4的病毒。我们将描述从感染早期到晚期的一系列纵向包膜的特征，并用它们来检验另外四个假设：(1)包膜进化到与CCR5的不同胞外结构域结合的方式会影响协同受体切换的概率；(2)只有当对包膜的抗体反应消失时，才会出现使用CXCR4的变体(R5X4或X4病毒)；(3)在一些患者中，R5病毒的进化达到了适应的上限，随后就是适应性的突然丧失，使得X4病毒变体能够在没有竞争的情况下出现；以及(4)与硫酸化的糖胺聚糖结合促进了协同受体切换。负责这些功能变化的包膜序列将被绘制出来。这些实验与CCR5抑制剂即将在III期临床试验中的使用高度相关，并可以很好地预测对这类抗病毒药物的耐药性概率。

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.