Structural Targeting of Potentially Protective gp120 Epitopes in the C1/C2 Region

 描述(由申请人提供)：关于具有强大的Fc受体介导(FCR)效应功能的非中和抗体(NnAbb)是否可以阻止HIV/SIV感染，存在一个重大的尚未解决的争议。因此，我们计划的长期目标是测试这样一个假设，即疫苗诱导的具有强大FCR效应功能的针对gp120的C1/C2-和V2-区表位的nnAbs可以防止SIV感染。这一假设将分两步进行检验。首先，通过本申请提出的AIMS，我们将 确定一种最佳的免疫原/佐剂配方，以在小动物中引发这些反应。其次，通过一项小型的“概念验证”研究，我们将在重复的、低剂量的SHIV162P3挑战模型中评估免疫原/佐剂配方。该项目的主要意义在于，它将支持或驳斥上述假设，为HIV-1疫苗的开发提供关键的新信息。大量证据表明，抗体的FCR效应功能，包括对gp120(A32类表位)C1区非中和表位的抗体依赖性细胞毒性(ADCC)，在预防或调节HIV-1感染和疫苗诱导的人类保护中具有作用。后者在很大程度上得到了RV144疫苗试验的结果的支持，该试验表明，在疫苗的子集中，抗体对A32亚区的应答降低了感染风险。此外，针对C1区和线性V2表位的抗体对传染性病毒捕获和ADCC具有协同作用，表明这些特异性之间的相互作用有助于由于FCR效应器功能而产生疫苗效果。通过这项应用，我们的目标是开发基于内部结构域的免疫原(ID)，能够仅诱导针对RV144试验中被确定为FCR效应反应靶点的表位的nnAbb。我们提出了这些新的ID结构，进一步优化了ADCC表位的选择性呈递和/或多聚体，以开发成新的免疫原，有效地选择性诱导针对人类保护性ADCC反应的一个(A32亚区)和两个(A32亚区和V2环)环境靶的FCR效应抗体反应。我们的候选ID免疫原由稳定在CD4结合构象中的gp120核心的内部结构域组成。ID在最小的稳定结构单元内稳定地呈现A32类表位，是进一步基于结构的优化和修饰的平台。目的1开发表达ADCC表位的ID和ID-V1V2的单体和多聚体。目的2将评估ID和ID-V1V2的单体和多聚体变种的抗原性，目的3将评估ID和ID-V1V2的单体和多聚体在BALB/c小鼠中的免疫原性。这些研究将完成检验疫苗诱导的nnAbs防止SIV感染的假说的第一步；识别免疫原。经修订的工作范围没有为开展SHIV162P3挑战研究提供足够的时间；然而，一旦有了合适的免疫原配方，研究所将为初步研究提供资金，同时为项目继续寻求资金。

 DESCRIPTION (provided by applicant): There is a major unresolved controversy of whether non-neutralizing antibodies (nnAbs) with potent Fc-receptor mediated (FcR)-effector functions can block HIV/SHIV acquisition. Accordingly, the long-term goal of our program is to test the hypothesis that vaccine-elicited nnAbs with potent FcR-effector functions and directed at epitopes in the C1/C2- and V2- regions of gp120 protect against SHIV acquisition. This hypothesis will be tested in two steps. First, through aims proposed with this application, we will identify an optimal immunogen/adjuvant formulation to elicit these responses in small animals. Second, through a small "proof of concept" study, we will evaluate the immunogen/adjuvant formulation in a repeat, low-dose SHIV162P3 challenge model. The principal significance of this project is that it will either support or refute the above hypothesis, providing new information critical to HIV-1 vaccine development. Considerable evidence points toward a role of FcR-effector functions of Abs including antibody-dependent cellular cytotoxicity (ADCC) toward non-neutralizing epitopes in the C1 region of gp120 (A32-like epitopes) in preventing or modulating HIV-1 infection and in vaccine induced protection in humans. The latter is largely supported by results of the RV144 vaccine trial that implicated Ab responses to A32 sub-region with reduced infection risk in a subset of vaccines. Furthermore, Abs specific for C1 region and linear V2-epitopes synergized for infectious virus capture and ADCC, suggesting the cross-talk between these specificities contributing to vaccine efficacy due to FcR-effector functions. With this application we aim to develop inner domain-based immunogens (ID) capable of inducing solely the nnAbs directed at epitopes identified as targets of FcR- effector response in the RV144 trial. We propose these novel ID constructs, further optimized for selective presentation of ADCC epitopes and/or multimerized to develop into new immunogens effective in selective inducing FcR-effector Ab responses directed at one (A32 sub-region) and both (A32 sub-region and V2 loop) Env targets associated with protective ADCC responses in human. Our ID immunogen candidate consists of the inner domain of the gp120 core stabilized in CD4-bound conformation. ID stably presents A32-like epitopes within a minimal stable structural unit and is a platform for further structure based optimization and modification. Aim 1 develop monomeric and multimerized variants of ID and ID-V1V2, both expressing the ADCC epitopes. Aim 2 will evaluate antigenicity of monomeric and multimeric variants of ID and ID-V1V2 and Aim 3 will evaluate the immunogenicity of monomeric and multimerized variants of ID and ID-V1V2 in BALB/c mice. These studies will complete the first step in testing the hypothesis that vaccine-elicited nnAbs protect against SHIV acquisition; identification of an immunogen. The revised work scope does not provide sufficient time to carry out a SHIV162P3 challenge study; however, once a suitable immunogen formulation is in hand, institute funds will be provided for a preliminary study while funding is sought for project continuation.