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

 描述（由申请方提供）：具有强效Fc受体介导（FcR）效应子功能的非中和抗体（nnAb）是否可以阻断HIV/SHIV获得存在重大争议。因此，我们计划的长期目标是测试疫苗诱导的nnAb具有有效的FcR效应子功能并针对gp 120的C1/C2和V2区域中的表位保护免受SHIV感染的假设。这一假设将分两步进行检验。首先，通过本申请提出的目标，我们将 鉴定最佳免疫原/佐剂制剂以在小动物中引发这些应答。其次，通过一项小型的“概念验证”研究，我们将在重复、低剂量SHIV 162 P3激发模型中评价免疫原/佐剂制剂。该项目的主要意义在于，它将支持或反驳上述假设，为HIV-1疫苗的开发提供关键的新信息。相当多的证据指向抗体的FcR效应子功能的作用，包括针对gp 120的C1区中的非中和表位（A32样表位）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的作用。后者在很大程度上得到了RV 144疫苗试验结果的支持，该试验涉及对A32亚区的抗体应答，在一个疫苗亚组中具有降低的感染风险。此外，特异于C1区和线性V2表位的Ab协同感染性病毒捕获和ADCC，表明由于FcR效应子功能，这些特异性之间的串扰有助于疫苗效力。通过该应用，我们的目标是开发能够仅诱导针对在RV 144试验中被鉴定为FcR效应子应答的靶标的表位的nnAb的基于内部结构域的免疫原（ID）。我们提出了这些新的ID构建体，进一步优化ADCC表位的选择性呈递和/或多聚化以开发成新的免疫原，其有效地选择性诱导针对一个（A32亚区）和两个（A32亚区和V2环）Env靶标的FcR效应物Ab应答，所述Env靶标与人中的保护性ADCC应答相关。我们的ID免疫原候选物由稳定在CD 4结合构象中的gp 120核心的内部结构域组成。ID在最小稳定结构单元内稳定地呈现A32样表位，并且是进一步基于结构的优化和修饰的平台。目的1开发均表达ADCC表位的ID和ID-V1 V2的单体和多聚化变体。目的2将评价ID和ID-V1 V2的单体和多聚体变体的抗原性，目的3将评价ID和ID-V1 V2的单体和多聚体变体在BALB/c小鼠中的免疫原性。这些研究将完成测试疫苗引发的nnAb防止SHIV获得的假设的第一步;免疫原的鉴定。修订后的工作范围没有提供足够的时间进行SHIV 162 P3攻毒研究;但是，一旦有合适的免疫原制剂，将为初步研究提供研究所资金，同时为项目的继续寻求资金。

 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.