Investigating an interface between gp120 and gp41 for HIV entry inhibition

描述（由申请人提供）：我们最近描述了一种HIV融合抑制剂PF-68742，其靶向涉及gp 41的融合肽（FP）和二硫环（DSL）区域的新位点。此后，我们在gp 120的C5区域发现了突变，这些突变深刻影响了HIV对PF-68742的敏感性。结果表明，PF-68742在涉及FP、DSL和C5的gp 120和gp 41之间的界面中与天然HIV Env结合。有趣的是，其他几种HIV进入抑制剂的抗病毒活性对涉及gp 120-gp 41界面和/或FP的突变表现出复杂但解释不清的敏感性。例如，VIRIP是最近描述的靶向FP的融合抑制剂，但HIV对VIRIP的抗性和逃逸尚未得到很好的研究，而FP中的突变最近已显示出深刻影响HIV对CCR 5依赖性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抗性或逃逸与“负”抑制相关，其中在低浓度的抑制剂存在下，HIV的特定变体的感染性增加，随后在较高浓度下抑制。涉及gp 120-gp 41界面突变的不同进入抑制剂活性的功能结果的这些共性对药物开发具有影响，因此需要进一步研究。为了更好地了解PF-68742的良好特异性和作用机制，在特定目的1中，我们将使用诱变分析来探测Env的结构决定簇，与VIRIP和MVC相比，Env影响HIV对PF-68742的敏感性。这些实验将解决FP及其突变在产生多类耐药性中的作用，将有助于概述FP与Env其他区域之间的功能关系，并将为下游筛选新的进入抑制剂提供信息。还将评价PF-68742和VIRIP与其他进入抑制剂的协同作用潜力。在特定目标2中，我们将制备PF-68742和VIRIP的示踪剂标记版本，以物理探测其结合位点的特定元素在天然Env的不同活化状态下的暴露，以及用于探测具有gp 120-gp 41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学化合物库，目的是通过结合和干扰影响FP的Env内的保守亚基界面来识别抑制HIV的药物。还将测试“命中”化合物影响Env稳定性以及与PF-68742、VIRIP或其他现有融合抑制剂互补或协同的潜力。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型Env三聚体结合测定以及我们将鉴定的新进入抑制剂先导物与设计和发现天然HIV-1 Env中保守gp 120-gp 41界面的HIV进入抑制剂相关。 公共卫生相关性：需要新的和更好的药物，可以阻止艾滋病毒进入宿主细胞之前。为了加速发现和开发此类药物，我们希望了解最近描述的一类HIV进入抑制剂的机制，并将其独特的功能与其他关键进入抑制剂药物的独特功能区分开来。我们将生产有价值的工具来探测其结合位点，然后寻找相关的新的HIV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.