Development of prime-boost immunization schemes to elicit VRC01-class bNAbs in polyclonal human BCR backgrounds

开发初免-加强免疫方案以在多克隆人 BCR 背景中引发 VRC01 类 bNAb

• 批准号: 10540729
• 负责人: Leonidas Stamatatos
• 金额: $ 63.83万
• 依托单位: FRED HUTCHINSON CANCER CENTER
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-12-06 至 2024-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10540729
• 关键词: Affinity; Alleles; Amino Acids; Animal Experiments; Animal Model; Antibodies; Antibody Affinity; Antibody Formation; Antibody Response; Antigens; B-Cell Activation; B-Cell Antigen Receptor; B-Lymphocyte Epitopes; B-Lymphocytes; Binding; Binding Sites; Bypass; Carbohydrates; Collaborations; Development; Elements; Engineering; Epitopes; Evolution; Frequencies; Generations; Genes; Goals; Grant; Growth; HIV; HIV Infections; HIV-1; Human; Immunization; Immunoglobulin Idiotypes; Immunoglobulin Somatic Hypermutation; In Vitro; Infection; Knock-in Mouse; Learning; Light; Link; Methodology; Monoclonal Antibodies; Mus; Mutate; Pathway interactions; Polysaccharides; Positioning Attribute; Process; Proteins; Reagent; Recombinants; Reporting; Scheme; Secondary Immunization; Series; Site; Site-Directed Mutagenesis; Somatic Mutation; Specificity; Testing; Transgenic Mice; Vaccination; Virus; adoptive B cell transfer; design; env Gene Products; experimental study; glycosylation; improved; in vivo; mouse model; neutralizing antibody; novel; prevent; simian human immunodeficiency virus; success; vaccination strategy; vaccine trial

ABSTRACT VRC01-class broadly neutralizing antibodies (bNAbs) recognize a conserved epitope within the CD4- binding site of HIV-1 Env. They are among the most potent bNAbs known and protect animals from experimental S/HIV infection, making them a highly attractive type of antibody to elicit by vaccination. They have been isolated from multiple HIV-1-infected subjects, but are all derived from the same VH1-2 allele (*02) and a small number of light chains, all of which express a 5 amino-acid CDRL3. In contrast to the mature, fully mutated forms of VRC01-class antibodies, their inferred germline forms do not recognize Env and do not neutralize HIV-1. This led to the hypothesis that previous recombinant Env immunogens were ineffective in activating naïve B cells expressing germline VRC01-class B cell receptors (BCRs), which may, in part, explain why such immunogens have not elicited VRC01-like antibody responses in vaccine studies. We reported on the design of a clade C-derived Env protein (426c Core) that binds germline VRC01-class antibodies and initiates the expansion of naïve B cells expressing the corresponding BCRs in vivo, but is insufficient to induce the maturation of these BCRs towards their neutralizing forms. A major hurdle to overcome in order to elicit any bNAbs through immunization is due to steric restrictions imposed by glycans present at the conserved glycosylation site N276 in Loop D of Env. These glycans limit access to the epitope recognized by germline VRC01-class antibodies, but as the antibodies undergo somatic hypermutation and affinity-based selection they ‘learn’ how to bypass this steric block. The success of our immunization strategies to elicit VRC01-class bNAbs will therefore depend on our ability to guide the evolution of germline VRC01-class antibodies along particular maturation pathways to bypass the N276 glycan-imposed restrictions. In this Project we propose to use concepts and reagents, not tested previously, in an effort to overcome these major obstacles preventing the generation of VRC01-class antibodies by immunization. Specifically, we propose to use anti-idiotypic monoclonal antibodies (aiMAbs) against the germline VRC01-class antibodies to specifically increase the frequency of VRC01-expressing B cells prior to immunization with the germline-binding’ 426c Core immunogen, followed by booster immunizations with Env-based reagents that select for VRC01-class B cells that can bypass the restrictions imposed by the N276 glycans. Our studies will be performed in an iterative fashion in diverse animal models that express VRC01-class BCRs, including mice engineered to express a polyclonal human BCR repertoire.

抽象的 VRC01级广泛中和抗体（BNAB）在CD4-中识别出保守的发作 HIV-1 Env的结合位点。它们是已知的最潜在的BNAB之一，并保护动物免受 实验性S/HIV感染，使其成为通过疫苗接种引起的高度吸引人的抗体类型。他们 已从多个HIV-1感染的受试者中隔离，但都源自同一VH1-2等位基因（*02） 以及少量的轻链，所有链条表达了5个氨基酸CDRL3。与成熟，完全相反 VRC01级抗体的突变形式，其推断的种系形式不承认Env和不认识 中和HIV-1。这导致了以下假设，即先前的重组ENV免疫原子无效 激活表达生殖线VRC01级B细胞受体（BCR）的B细胞，该细胞可能部分解释 为什么这种免疫原子在疫苗研究中没有引起VRC01样抗体反应。我们报告了 结合种系VRC01级抗体和 启动在体内表达相应BCR的天真B细胞的扩展，但不足以诱导 这些BCR朝着中和形式的成熟。要克服的主要障碍，以引起任何 通过免疫抑制的BNAB是由于存在于保守的聚糖施加的空间限制所致 Env的循环D中的糖基化位点N276。这些聚糖限制了对种系认可的表位的访问 VRC01级抗体，但随着抗体经历躯体超成名和基于亲和力的选择 他们“学习”如何绕过这个空间块。我们的免疫策略获得VRC01级的成功 因此，BNAB将取决于我们指导沿着种系VRC01级抗体进化的能力 绕过N276型聚糖施加的限制的特殊成熟途径。在这个项目中，我们建议 使用以前未测试的概念和试剂，以克服这些主要障碍，以防止 通过免疫产生VRC01级抗体。具体而言，我们建议使用抗IDiotypic 针对种系VRC01级抗体的单克隆抗体（AIMAB），以特异性增加 用种系结合‘426C核心在免疫之前表达VRC01的B细胞的频率 免疫原，然后是基于ENV的试剂的增强免疫抑制作用，可以选择VRC01级B细胞 这可以绕过N276聚糖施加的限制。我们的研究将在迭代中进行 表达VRC01级BCR的潜水动物模型中的时尚，包括设计用于表达的小鼠 多克隆人类BCR曲目。