Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA.
Center for Vaccines and Immunology, College of Veterinary Medicine, University of Georgia, Athens, GA.
J Immunol. 2022 Jul 1;209(1):5-15. doi: 10.4049/jimmunol.2101171. Epub 2022 Jun 13.
Computationally optimized broadly reactive Ag (COBRA) hemagglutinin (HA) immunogens have previously been generated for several influenza subtypes to improve vaccine-elicited Ab breadth. As nearly all individuals have pre-existing immunity to influenza viruses, influenza-specific memory B cells will likely be recalled upon COBRA HA vaccination. We determined the epitope specificity and repertoire characteristics of pre-existing human B cells to H1 COBRA HA Ags. Cross-reactivity between wild-type HA and H1 COBRA HA proteins P1, X6, and Y2 were observed for isolated mAbs. The mAbs bound five distinct epitopes on the pandemic A/California/04/2009 HA head and stem domains, and most mAbs had hemagglutination inhibition and neutralizing activity against 2009 pandemic H1 strains. Two head-directed mAbs, CA09-26 and CA09-45, had hemagglutination inhibition and neutralizing activity against a prepandemic H1 strain. One mAb, P1-05, targeted the stem region of H1 HA, but did not compete with a known stem-targeting H1 mAb. We determined that mAb P1-05 recognizes a recently discovered HA epitope, the anchor epitope, and we identified similar mAbs using B cell repertoire sequencing. In addition, the trimerization domain distance from HA was critical to recognition of this epitope by mAb P1-05, suggesting the importance of protein design for vaccine formulations. Overall, these data indicate that seasonally vaccinated individuals possess a population of functional H1 COBRA HA-reactive B cells that target head, central stalk, and anchor epitopes, and they demonstrate the importance of structure-based assessment of subunit protein vaccine candidates to ensure accessibility of optimal protein epitopes.
先前已经针对几种流感亚型生成了经过计算优化的广泛反应性 Ag（COBRA）血凝素（HA）免疫原，以提高疫苗诱导的 Ab 广度。由于几乎所有个体都对流感病毒具有预先存在的免疫力，因此在 COBRA HA 接种后，流感特异性记忆 B 细胞可能会被召回。我们确定了针对 H1 COBRA HA Ag 的人 B 细胞预先存在的表位特异性和 repertoire 特征。针对分离的 mAb 观察到野生型 HA 和 H1 COBRA HA 蛋白 P1、X6 和 Y2 之间的交叉反应性。mAb 结合了大流行 A/加利福尼亚/04/2009 HA 头部和茎区的五个不同表位，大多数 mAb 对 2009 年大流行 H1 株具有血凝抑制和中和活性。两种针对头部的 mAb，CA09-26 和 CA09-45，对流行前 H1 株具有血凝抑制和中和活性。一种 mAb，P1-05，针对 H1 HA 的茎区，但不与已知的茎靶向 H1 mAb 竞争。我们确定 mAb P1-05 识别最近发现的 HA 表位，即锚定表位，并且我们使用 B 细胞 repertoire 测序鉴定了类似的 mAb。此外，HA 与 mAb P1-05 识别的表位的三聚体化结构域距离对于该表位的识别至关重要，这表明蛋白设计对于疫苗制剂的重要性。总的来说，这些数据表明，季节性接种疫苗的个体拥有针对头部、中央茎和锚定表位的功能性 H1 COBRA HA 反应性 B 细胞群体，并且它们证明了基于结构的亚单位蛋白疫苗候选物评估的重要性，以确保可及性最佳的蛋白表位。
