Germline-Specific Immunogens for the Induction of Neutralizing Antibodies to HIV-

描述(申请人提供)：疫苗可以减缓艾滋病毒/艾滋病疫情的传播，识别诱导中和抗体的免疫原仍然是艾滋病毒疫苗研究的重要目标。越来越多的广泛中和的人类单抗(MAbs)已经从感染的人身上分离出来，这些人表现出非常广泛和强大的中和反应。再加上过去的研究，这些结果支持了这样的观点，即人类免疫系统可以产生罕见但有效的保护性抗体来对抗病毒。许多工作，包括我们自己的工作，都集中在识别与广泛中和抗体结合的HIV-1包膜糖蛋白(Env)的形式上。与优化Env与这些高亲和力成熟抗体结合的方法不同，我们现在建议识别能够与广泛中和抗体的种系形式结合的Env变体，作为一种更有效的免疫方法。虽然抗体-抗原相互作用的结构研究已经为抗原设计提供了信息，但相应的生殖系抗体序列很少显示出与HIV-1环境病毒的任何结合。因此，对于生殖系结合环境的合理设计来说，详细的信息并不容易获得。因此，我们建议使用定向分子进化方法来鉴定种系特异性免疫原。这种免疫原可以更有效地刺激幼稚的B细胞。广泛中和的VRC01单抗非常适合于这种方法，特别是因为与大多数其他广泛中和的单抗相比，CDRH3结构域对中和活性的重要性较小。这最小化了预测胚系VRC01前体结构的约束之一。我们将根据猕猴生殖系序列创建一些类似VRC01的单抗，并将其用作试剂来筛选通过体外同源DNA重组创建的环境变异体文库。我们将用这些种系特异性变种免疫猕猴，并使用大规模平行DNA测序技术分析这些基于环境的免疫原刺激特定种系亲和力成熟的能力。根据初步免疫研究的结果，我们将确定更多的免疫原，这些免疫原刺激沿着特定路径部分亲和成熟的抗体形成成熟的中和抗体。生殖系特异性免疫原和额外的免疫原将用于在10个月内免疫猕猴。对抗体基因突变模式的分析将表明是否有可能沿着特定的途径引导抗体成熟。即使我们不能成功地诱导出类似VRC01的活性，这项研究的结果也将使我们更好地理解免疫原的最初反应，以及它可以在多大程度上被操纵和控制。这项提议是确定HIV-1疫苗候选免疫原的一种创新方法。它普遍适用于已确定具有保护性(或广泛保护性)单抗的其他病原体(例如呼吸道合胞病毒或流感)，但这些特异性的诱导被证明是有问题的。

DESCRIPTION (provided by applicant): Vaccines can slow the spread of the HIV/AIDS epidemic, and the identification of immunogens that induce neutralizing antibodies remains an important goal of HIV vaccine research. An increasing number of broadly neutralizing human monoclonal antibodies (mAbs) have been isolated from infected individuals who show remarkably broad and potent neutralizing responses. Coupled with past studies, these results support the idea that the human immune system can generate rare but potent protective antibodies to the virus. Much work, including our own, has focused on identifying forms of the HIV-1 envelope glycoprotein (Env) that bind to broadly neutralizing antibodies. In contrast to approaches that optimize Env for binding to these highly affinity-matured antibodies, we now propose to identify Env variants that can bind to the germline form of the broadly neutralizing antibodies as a more productive approach to immunization. While structural studies of antibody-antigen interactions have informed antigen design, the corresponding germline antibody sequences rarely show any binding to the HIV-1 Env. As a result, detailed information is not readily available for the rational design of germline-binding Env. We propose therefore to use a directed molecular evolution approach to identify germline-specific immunogens. Such immunogens could more effectively stimulate naive B cells. The broadly neutralizing VRC01 mAb is well suited to this approach, notably because the CDRH3 domain is less important for the neutralization activity compared to most of the other broadly neutralizing mAbs. This minimizes one of the constraints in predicting the structure of the germline VRC01 precursor. We will create a number of VRC01-like mAbs based on macaque germline sequences that are increasing reverted to the germline sequence and use these as reagents to screen libraries of Env variants created by in vitro homologous DNA recombination. We will immunize macaques with these germline-specific variants and analyze, using massively parallel DNA sequencing technologies, the ability of these Env-based immunogens to stimulate affinity maturation of the specific germline for which they were selected. Based on the results of an initial immunization study, we will identify additional immunogens that stimulate partially affinity-matured antibodies along a particular path to form a mature neutralizing antibody. The germline-specific and the additional immunogens will be used to immunize macaques over a 10-month period. Analysis of the pattern of mutation in the antibody genes will indicate whether it is possible to direct antibody maturation along a specific pathway. Even if we do not succeed in eliciting VRC01-like activity, the results of this study will lead to a greater understanding of the initial response tothe immunogen and to what extent can it be manipulated and controlled. This proposal represents an innovative approach to the identification of candidate immunogens for HIV-1 vaccines. It has general applicability to other pathogens for which protective (or broadly protective) mAbs have been identified (e.g. RSV or influenza) but where induction of those specificities has proven problematic.