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

描述(申请人提供)：迫切需要疫苗来减缓艾滋病毒/艾滋病疫情的传播，能够诱导中和抗体的免疫原仍然是疫苗研究的重要目标。近年来，从表现出广泛而有效的中和反应的个体中分离出越来越多的人类单抗(MAbs)。再加上过去的工作，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与这些高度亲和力成熟的抗体结合的方法不同，我们和其他人现在建议识别能够与广泛中和抗体的种系形式结合的免疫原，作为一种更有效的免疫方法。 虽然抗体-抗原相互作用的三维结构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-1Env的任何结合。因此，结构信息不容易用于种系免疫原的合理设计。因此，我们建议采用定向分子进化的方法来识别种系特异性免疫原。这种免疫原可以刺激携带成熟广中和抗体胚系前体的未成熟B细胞。因为任何单独的生殖系序列只代表所有重排免疫球蛋白基因的几个百分点，用生殖系特异性免疫原激活特定的B细胞可能会增加诱导适当抗体的可能性。人们还可以设想使用一系列免疫原来刺激沿着特定路径部分亲和力成熟的抗体形成成熟的中和抗体。 最近鉴定的VRC01单抗非常适合于这种方法，特别是因为与大多数其他广谱中和单抗相比，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。我们将创建一些类似VRC01的单抗，这些单抗越来越多地恢复到生殖系序列，并使用这些单抗作为试剂来筛选通过体外同源DNA重组创建的环境变异体文库。可以以逐步递归的方式使用回复突变体，从而可以将结合最小回复单抗的环境变异体用作亲本来创建额外变异体的文库，用于筛选具有更高回复形式的变异体。我们将评估这些生殖系特异性Env免疫原与在细胞表面表达VRC01类生殖系抗体的骨髓瘤细胞结合的能力，这种相互作用类似于B细胞激活的第一步之一。 这项提议是确定HIV-1疫苗候选免疫原的一种创新方法。它对其他已确定具有保护性(或广泛保护性)单抗的病原体(例如RSV或流感)具有普遍适用性，但这些抗体特异性的诱导已被证明是有问题的。 与公共卫生有关：艾滋病毒/艾滋病疫情继续造成死亡和新的感染，约有3300万人患有这种疾病。能够减少感染的疫苗是预防措施的重要组成部分。这项研究提案旨在创造能够防止艾滋病毒感染细胞的候选疫苗。

DESCRIPTION (provided by applicant): Vaccines are urgently needed to slow the spread of the HIV/AIDS epidemic, and immunogens that can induce neutralizing antibodies remain an important goal of vaccine research. An increasing number of human monoclonal antibodies (mAbs) have been isolated in recent years from individuals who show remarkably broad and potent neutralizing responses. Coupled with past work, 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 and others now propose to identify immunogens that can bind to the germline form of the broadly neutralizing antibodies as a more productive approach to immunization. While three-dimensional structures 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, structural information is not readily available for rational design of germline immunogens. We propose therefore to employ a directed molecular evolution approach to the problem of identifying germline-specific immunogens. Such immunogens could stimulate immature B cells that carry the germline precursor of a mature broadly neutralizing antibody. Because any individual germline sequence represents only a few percent of all rearranged immunoglobulin genes, activating specific B cells with germline-specific immunogens could increase the likelihood of inducing an appropriate antibody. One can also envision using a series of immunogens that stimulate partially affinity-matured antibodies along a particular path to form a mature neutralizing antibody. The recently characterized 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 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. The revertants can be used in a stepwise recursive fashion, whereby Env variants that bind minimally reverted mAbs can be used as parents to create libraries of additional variants for screening with more highly reverted forms. We will evaluate the ability of these germline-specific Env immunogens to bind to myeloma cells that express VRC01-like germline antibodies on the cell surface, an interaction that resembles one of the first steps of B-cell activation. 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 induction of those antibody specificities has proven problematic. PUBLIC HEALTH RELEVANCE: The HIV/AIDS epidemic continues to cause death and new infections with some 33 million people living with the disease. A vaccine that can reduce infection is an essential component of preventative measures. This research proposal is designed to create vaccine candidates that can prevent the HIV virus from infecting cells.