Supplementary file 1_Human broadly neutralizing influenza B virus antibodies recognizing hemagglutinin computationally optimized broadly reactive antigens.docx

IntroductionInfluenza B viruses (IBVs) are responsible for severe disease and death, similarly to influenza A viruses (IAVs), with a higher number of infections happening in children and the elderly. Despite the inclusion of an IBV component in the seasonal influenza vaccine, rates of vaccine effectiveness (VE) are still variable and low in many previous seasons.
MethodsIn this work, longitudinal profiling of IBV hemagglutinin (HA)-specific B-cell responses was described following influenza vaccination in 15 vaccinated participants over four consecutive influenza seasons. These individuals belonged to different age groups and monoclonal antibodies (mAbs) showing broad binding and functional antibody profiles were isolated from the plasmablasts of one individual.
ResultsThese individuals possessed different breadths and magnitudes of antibody responses to a panel of IBV historical and more recent vaccine strains. In particular, young adults (age 23–33) showed a higher magnitude and breadth of antibody response compared to middle-aged (age 55–58) and elderly (age 65–77) participants who instead showed a lower albeit detectable antibody response. Interestingly, one of the isolated mAbs, mAb #46, had the broadest response with a broad binding and potent functional activity against historical and recent IBV strains spanning both Victoria and Yamagata lineages and including binding to IBV computationally optimized broadly reactive antigen (COBRA) HAs. Importantly, mAb #46 administration, either therapeutically or prophylactically, fully protected IBV-challenged mice. Structural characterization of the mAb #46–HA complex by cryo-electron microscopy single-particle analysis revealed that mAb #46 targets a conserved epitope within the HA receptor binding site.
DiscussionThis study highlights the presence of broadly neutralizing antibodies in the human repertoire that may be recalled by vaccination with COBRA HA, although this hypothesis will be confirmed in upcoming clinical trials.

引言：乙型流感病毒（Influenza B viruses, IBVs）与甲型流感病毒（Influenza A viruses, IAVs）类似，可引发重症疾病甚至死亡，且儿童与老年群体的感染人数更多。尽管季节性流感疫苗中已包含IBV组分，但此前多个流感季的疫苗保护效力（Vaccine Effectiveness, VE）仍波动较大且普遍偏低。
方法：本研究对15名接种者连续四个流感季接种流感疫苗后的IBV血凝素（hemagglutinin, HA）特异性B细胞应答进行了纵向分析。这些受试者覆盖不同年龄组；研究还从1名受试者的浆母细胞中分离出了具备广谱结合与功能活性特征的单克隆抗体（monoclonal antibodies, mAbs）。
结果：受试者对一组IBV经典及近期疫苗株的抗体应答广度与强度存在差异。具体而言，年轻成年人（年龄23~33岁）的抗体应答强度与广度均高于中年（55~58岁）与老年（65~77岁）受试者，后两者虽抗体应答水平较低，但仍可检测到应答。值得注意的是，分离得到的单克隆抗体#46（mAb #46）具有最广谱的反应性，可结合维多利亚（Victoria）与山形（Yamagata）两个谱系的经典及近期IBV毒株，且具备强效的功能活性，同时可结合经计算优化的广谱反应性抗原（computationally optimized broadly reactive antigen, COBRA）HA。重要的是，无论是治疗性还是预防性给药，mAb #46均可完全保护受IBV攻击的小鼠。通过冷冻电镜单颗粒分析解析mAb #46与HA复合物的结构，发现mAb #46靶向HA受体结合位点内的保守表位。
讨论：本研究证实人类免疫库中存在广谱中和抗体，此类抗体可通过接种COBRA HA疫苗被唤起，但该假说仍需在后续临床试验中加以验证。