Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, United States.
Department of Epidemiology and Biostatistics, The University of Texas Health Science Center at San Antonio, San Antonio, TX, United States.
Front Immunol. 2019 Mar 29;10:706. doi: 10.3389/fimmu.2019.00706. eCollection 2019.
Recent studies of human sera showed that the majority of the respiratory syncytial virus (RSV) neutralizing antibodies are directed against pre-fusion conformation of the fusion (F) protein of RSV and revealed the importance of pre-fusion antigenic site Ø specific antibodies. However, detailed analysis of multiple antigenic site-specific competitive antibody responses to RSV F protein and their contribution to virus clearance in humans are lacking. We prospectively enrolled a cohort of RSV infected hematopoietic cell transplantation (HCT) adults ( = 40). Serum samples were collected at enrollment (acute, = 40) and 14 to 60 days post-enrollment (convalescent, = 40). Antigenic site-specific F protein antibodies were measured against pre-fusion site Ø, post-fusion site I, and sites II and IV present in both the pre-fusion and post-fusion F protein conformations utilizing four different competitive antibody assays developed with biotinylated monoclonal antibodies (mAb) D25, 131-2A, palivizumab, and 101F, respectively. The lower limit of detection were 7.8 and 1.0 μg/mL for the competitive antibody assays that measured site Ø specific response, as well as sites I, II, and IV specific responses, respectively. Neutralizing antibody titers to RSV A and B subgroups was determined by microneutralization assays. The overall findings in RSV infected HCT adults revealed: (1) a significant increase in antigenic site-specific competitive antibodies in convalescent sera except for site Ø competitive antibody ( < 0.01); (2) comparable concentrations in the acute and convalescent serum samples of antigenic site-specific competitive antibodies between RSV/A and RSV/B infected HCT adults ( > 0.05); (3) significantly increased concentrations of the antigenic site-specific competitive antibodies in HCT adults who had genomic RSV detected in the upper respiratory tract for <14 days compared to those for ≥14 days ( < 0.01); and (4) statistically significant correlation between the antigenic site-specific competitive antibody concentrations and neutralizing antibody titers against RSV/A and RSV/B (r ranged from 0.33 to 0.83 for acute sera, and 0.50-0.88 for convalescent sera; < 0.05). In RSV infected HCT adults, antigenic site-specific antibody responses were induced against multiple antigenic sites found in both the pre-fusion and post-fusion F conformations, and were associated with a more rapid viral clearance and neutralizing antibody activity. However, the association is not necessarily the cause and the consequence.
最近对人体血清的研究表明，大多数呼吸道合胞病毒（RSV）中和抗体针对 RSV 融合（F）蛋白的预融合构象，并揭示了预融合抗原表位 Ø 特异性抗体的重要性。然而，目前缺乏对 RSV F 蛋白多个抗原表位特异性竞争抗体反应的详细分析及其对人体中病毒清除的贡献。我们前瞻性地招募了一组 RSV 感染的造血细胞移植（HCT）成人（n=40）。在入组时（急性期，n=40）和入组后 14 至 60 天（恢复期，n=40）采集血清样本。利用四种不同的竞争性抗体测定法，分别用生物素化单克隆抗体（mAb）D25、131-2A、palivizumab 和 101F 测量针对预融合表位 Ø、融合后表位 I 以及存在于预融合和融合 F 蛋白构象中的表位 II 和 IV 的抗原表位特异性 F 蛋白抗体。用于测量表位 Ø 特异性反应以及表位 I、II 和 IV 特异性反应的竞争性抗体测定的检测下限分别为 7.8 和 1.0μg/mL。通过微量中和测定法确定 RSV A 和 B 亚组的中和抗体滴度。RSV 感染的 HCT 成人中的总体发现包括：（1）除表位 Ø 竞争抗体外（<0.01），恢复期血清中抗原表位特异性竞争抗体的显著增加；（2）RSV/A 和 RSV/B 感染的 HCT 成人急性和恢复期血清中抗原表位特异性竞争抗体的浓度相当（>0.05）；（3）与上呼吸道中检测到 RSV 的时间≥14 天的 HCT 成人相比，上呼吸道中检测到 RSV 的时间<14 天的 HCT 成人的抗原表位特异性竞争抗体浓度显著增加（<0.01）；（4）抗原表位特异性竞争抗体浓度与针对 RSV/A 和 RSV/B 的中和抗体滴度之间存在统计学显著相关性（r 值范围为急性血清的 0.33 至 0.83，恢复期血清的 0.50 至 0.88；<0.05）。在 RSV 感染的 HCT 成人中，针对预融合和融合 F 构象中存在的多个抗原表位诱导了抗原表位特异性抗体反应，并且与更快的病毒清除和中和抗体活性相关。然而，这种关联不一定是原因和结果。
