Expansion and targeted maturation of germline HIV-1 bNAb-associated BCRs

摘要 通过免疫接种引发有效和广泛的HIV-1中和抗体（bNAb）一直是免疫治疗的方法之一。 自HIV/AIDS流行开始以来，HIV-1疫苗研究的主要目标。在过去的十年里， 重大的技术和概念进步使得能够分离和详细描述 大量来自HIV-1感染者的新bNAb。这种抗体的结构表征， 结合它们个体发育的信息，极大地提高了我们对这些抗体如何 是在自然感染过程中产生的，这导致了关于如何通过 次免疫我们的HIVRAD计划拨款旨在测试新试剂和初免-加强免疫 引发VRC 01类bNAb的方案，这是最广泛和最有效的HIV-1中和 已知的抗体，并在动物研究中显示出令人印象深刻的保护潜力。但发展 通过免疫接种VRC 01类bNAb将需要克服几个障碍。一个成功 免疫方案可能至少需要新的免疫原的可用性， 指导bNAb成熟过程，制定战略，将最大限度地减少扩张 竞争脱靶B细胞，开发最佳的“加强”Env免疫原，以指导适当的 抗体成熟和持续的T辅助反应的供应。在这里，我们建议测试概念，而不是 我们已经开发了一种可以直接解决这些问题的方法。我们将评估一个新策略 是基于使用抗独特型单克隆抗体（aiMAb），我们产生的生殖系VRC 01- BCR类。我们的初步数据表明，这些aiMAb特异性扩增表达以下蛋白的幼稚B细胞： 生殖系VRC 01-B类细胞受体（BCR），这些细胞进入生殖中心（GC）反应 并进一步扩展Env免疫。一个明显的优点是GC的更大扩展， 期望的B细胞而不是“脱靶”的B细胞，从而提高了我们诱导正确的体细胞集的机会。 在加强免疫过程中的超突变。因此，用aiMAb免疫接种后将进行加强免疫。 用专门设计用于接合生殖系VRC 01类BCR（426 c核心）的Env进行免疫接种，然后 其中Envs表达VRC 01类抗体的关键空间阻断。在这方面，我们强调， 自从我们最初提交以来，我们产生了新的信息，表明426 c核心抗体 绕过保守的N-连接糖基化位点N276上的聚糖，这是主要的障碍之一， 防止生殖系VRC 01类抗体成为广泛中和的。我们将测试我们提出的 战略的迭代方法与良好的综合实验。我们提供的初步数据支持 我们的整体方法。

ABSTRACT The elicitation of potent and broad HIV-1 neutralizing antibodies (bNAbs) by immunization has been one of the major goals of HIV-1 vaccine research since the beginning of the HIV/AIDS epidemic. During the past decade, significant technical and conceptual advances have enabled the isolation and detailed characterization of a plethora of new bNAbs from HIV-1-infected subjects. The structural characterization of such antibodies, combined with information on their ontogenies, has vastly improved our understanding of how such antibodies are generated during natural infection, leading to new hypotheses regarding how to elicit them by immunization. Our HIVRAD Program grant aims at testing novel reagents and prime-boost immunization schemes to elicit VRC01-class bNAbs, which are among the most broad and potent HIV-1 neutralizing antibodies known and display impressive protective potential in animal studies. However, the development of VRC01-class bNAbs by immunization will necessitate overcoming several obstacles. A successful immunization scheme will likely require, at a minimum, the availability of novel immunogens to initiate and guide the bNAb maturation process, the development of strategies that will minimize the expansion of competing off-target B cells, the development of optimal ‘boost’ Env immunogens to guide the appropriate antibody maturation, and the supply of sustained T helper responses. Here we propose to test concepts, not tested previously, that we have developed to directly address these issues. One new strategy we will evaluate is based on the use of anti-idiotypic monoclonal antibodies (aiMAbs) we generated against germline VRC01- class BCRs. Our preliminary data suggest that these aiMAbs specifically expand naive B cells that express germline VRC01-class B cell receptors (BCRs) and that these cells enter the germinal center (GC) reaction and expand even further upon Env immunization. One obvious advantage is a greater expansion in GC of desired B cells over ‘off target’ B cells, thus improving our chance to induce the correct set of somatic hypermutations during the boost immunizations. Thus, immunizations with aiMAbs will be followed by booster immunizations with an Env specifically designed to engage germline VRC01-class BCRs (426c Core) and then with Envs expressing key steric blocks for VRC01-class antibodies. In this regard we highlight the fact that since our initial submission we generated new information which indicates that the 426c Core elicits antibodies that bypass glycans on the conserved N-linked glycosylation site N276, which are one of the major obstacles preventing germline VRC01-class antibodies from becoming broadly neutralizing. We will test our proposed strategy by an iterative approach with well-integrated experiments. The preliminary data we present support our overall approach.