Investigating an interface between gp120 and gp41 for HIV entry inhibition

描述(申请人提供)：我们最近描述了一种HIV融合抑制剂PF-68742，它针对涉及gp41的融合肽(FP)和二硫键环(DSL)区域的一个新位点。自那以后，我们在gp120的C5区域发现了突变，这些突变深刻地影响了艾滋病毒对PF-68742的敏感性。结果表明，PF-68742与天然的HIV env结合在gp120和gp41之间的界面上，涉及FP、DSL和C5。有趣的是，其他几种HIV进入抑制剂的抗病毒活性对涉及gp120-gp41接口和/或FP的突变表现出复杂但难以解释的敏感性。例如，VIRIP是一种最近被描述的针对FP的融合抑制剂，但对HIV的耐药性和对VIRIP的逃逸还没有很好的研究，而FP的突变最近被证明深刻地影响了HIV对CCR5依赖的进入抑制剂如马拉韦罗(MVC)的敏感性。有趣的是，FP介导的对这些抑制剂的耐药性或逃逸与“负”抑制有关，在这种情况下，HIV的特定变种的传染性在低浓度抑制剂存在时增加，然后在较高浓度时抑制。涉及gp120-gp41界面突变的不同进入抑制活性在功能结果上的这些共性对药物开发具有影响，因此值得进一步研究。为了更好地了解PF-68742良好的特异性和作用机制，在特定的目标1中，我们将使用突变图谱来探索影响HIV对PF-68742敏感性的环境结构决定因素，并与VIRIP和MVC进行比较。这些实验将解决FP及其突变在产生多类耐药中的作用，将有助于概述FP与Env其他区域之间的功能关系，并将为下游筛查新的进入抑制物提供信息。还将评估PF-68742和VIRIP与其他进入抑制剂的协同作用。在具体目标2中，我们将制备示踪剂标记的PF-68742和VIRIP版本，以物理地探测其结合位点的特定元件在天然Env的不同激活状态下的暴露，以及用于探测具有gp120-gp41界面的相关Env模拟分子。在具体目标3中，我们将筛选不同的化合物文库，目的是通过与影响FP的Env内保守的亚单位接口结合和干扰来识别抑制HIV的药物。还将测试“HIT”化合物影响环境稳定性的可能性，以及与PF-68742、VIRIP或其他现有融合抑制剂的互补或协同作用。总体而言，将获得的关于Env的结构功能信息，我们将开发的工具和新的Env三聚体结合分析，以及我们将确定的新的进入抑制剂先导，与设计和发现HIV进入抑制剂到天然HIV-1环境中保守的gp120-gp41界面有关。 与公共卫生相关：需要新的和更好的药物来在艾滋病毒进入宿主细胞之前阻止它。为了加速这类药物的发现和开发，我们希望了解最近描述的一种第一类HIV进入抑制剂的作用机制，并将其独特特性与其他关键进入抑制剂药物的共同之处区分开来。我们将生产有价值的工具来探测其结合部位，然后寻找相关的新的艾滋病毒药物线索。

DESCRIPTION (provided by applicant): We recently described an HIV fusion inhibitor, PF-68742, that targets a novel site involving the fusion peptide (FP) and disulfide loop (DSL) region of gp41. We have since discovered mutations in the C5 region of gp120 that profoundly affect sensitivity of HIV to PF-68742. The results suggest that PF-68742 binds to native HIV Env in an interface between gp120 and gp41 involving FP, DSL and C5. Interestingly, antiviral activities of several other entry inhibitors to HIV show complex but poorly explained sensitivity to mutations involving the gp120-gp41 interface and/or FP. As examples, VIRIP is a recently described fusion inhibitor that targets FP but HIV resistance and escape to VIRIP has not been well studied, whereas mutations in FP have recently been shown to profoundly affect HIV sensitivity to CCR5-dependent entry inhibitors such as maraviroc (MVC). Interestingly, FP-mediated resistance or escape to these inhibitors has been associated with 'negative' inhibition, in which infectivity of particular variants of HIV is increased in the presence of low concentrations of inhibitor, followed by inhibition at higher concentrations. These commonalities in the functional outcome of different entry inhibitor activities involving mutations at the gp120-gp41 interface have implications for drug development and therefore warrant further investigation. To gain a better understanding of the fine specificity and mechanism of action of PF-68742, in Specific Aim 1, we will use mutagenic profiling to probe structural determinants of Env that affect HIV sensitivity to PF-68742 in comparison to VIRIP and MVC. The experiments will address the role of FP and its mutation in generating multi-class drug resistance, will help outline the functional relationship between FP and other regions of Env, and will inform downstream screens for new entry inhibitors. Potential for synergy of PF-68742 and VIRIP with other entry inhibitors will also be evaluated. In Specific Aim 2, we will prepare tracer labeled versions of PF-68742 and VIRIP to physically probe the exposure of specific elements of their binding sites in different activation states of native Env, as well as for use in probing relevant Env mimetic molecules that bear a gp120-gp41 interface. In Specific Aim 3, we will screen a diverse chemical compound library with the aim of identifying agents that inhibit HIV by binding to and perturbing the conserved subunit interfaces within Env that affect FP. Potential for 'hit' compounds to affect Env stability and complement or synergize with PF-68742, VIRIP or other existing fusion inhibitors will also be tested. Overall, the structure-function information on Env that will be gained, the tools and novel Env trimer- binding assays that we will develop, as well as the new entry inhibitor leads we will identify are relevant to the design and discovery of HIV entry inhibitors to a conserved gp120-gp41 interface in native HIV-1 Env. PUBLIC HEALTH RELEVANCE: New and better drugs are desired that can block HIV before it enters into host cells. To accelerate discovery and development of such drugs, we wish to understand the mechanisms of a recently described, first-in-class HIV entry inhibitor, and distinguish its unique features from those it shares with other key entry inhibitor drugs. We will produce valuable tools for probing its binding site, and then look for relevant new HIV drug leads.