Department of Biochemistry, The University of Texas at Austin, Austin, Texas, USA.
Excelimmune, Inc., Woburn, Massachusetts, USA.
Infect Immun. 2018 May 22;86(6). doi: 10.1128/IAI.00004-18. Print 2018 Jun.
Despite high vaccination rates, the incidence of whooping cough has steadily been increasing in developing countries for several decades. The current acellular pertussis (aP) vaccines all include the major protective antigen pertussis toxin (PTx) and are safer, but they appear to be less protective than infection or older, whole-cell vaccines. To better understand the attributes of individual antibodies stimulated by aP, we isolated plasmablast clones recognizing PTx after booster immunization of two donors. Five unique antibody sequences recognizing native PTx were recovered and expressed as recombinant human IgG1 antibodies. The antibodies all bind different epitopes on the PTx S1 subunit, B oligomer, or S1-B subunit interface, and just one clone neutralized PTx in an assay. To better understand the epitopes bound by the nonneutralizing S1-subunit antibodies, comprehensive mutagenesis with yeast display provided a detailed map of the epitope recognized by antibodies A8 and E12. Residue R76 is required for antibody A8 binding and is present on the S1 surface but is only partially exposed in the holotoxin, providing a structural explanation for A8's inability to neutralize holotoxin. The B-subunit-specific antibody D8 inhibited PTx binding to a model receptor and neutralized PTx as well as in an leukocytosis assay. This is the first study, to our knowledge, to identify individual human antibodies stimulated by the acellular pertussis vaccine and demonstrates the feasibility of using these approaches to address outstanding issues in pertussis vaccinology, including mechanisms of accelerated waning of protective immunity despite repeated aP immunization.
尽管疫苗接种率很高，但几十年来，发展中国家百日咳的发病率一直在稳步上升。目前的无细胞百日咳（aP）疫苗都包含主要的保护性抗原百日咳毒素（PTx），更安全，但它们的保护效果似乎不如感染或较旧的全细胞疫苗。为了更好地了解 aP 刺激的个体抗体的特性，我们在两名供体加强免疫后分离出识别 PTx 的浆母细胞克隆。回收了识别天然 PTx 的 5 个独特抗体序列，并表达为重组人 IgG1 抗体。这些抗体都结合了 PTx S1 亚基、B 聚体或 S1-B 亚基界面上不同的表位，只有一个克隆在测定中中和了 PTx。为了更好地了解非中和性 S1 亚基抗体结合的表位，酵母展示的全面突变提供了抗体 A8 和 E12 识别的表位的详细图谱。残基 R76 是抗体 A8 结合所必需的，存在于 S1 表面，但在全毒素中仅部分暴露，为 A8 无法中和全毒素提供了结构解释。B 亚基特异性抗体 D8 抑制了 PTx 与模型受体的结合，并中和了 PTx，以及在白细胞增多测定中。据我们所知，这是首次鉴定出由无细胞百日咳疫苗刺激的个体人类抗体的研究，并证明了使用这些方法解决百日咳疫苗学中未解决问题的可行性，包括尽管重复 aP 免疫但保护性免疫加速减弱的机制。
