Throsby Mark, van den Brink Edward, Jongeneelen Mandy, Poon Leo L M, Alard Philippe, Cornelissen Lisette, Bakker Arjen, Cox Freek, van Deventer Els, Guan Yi, Cinatl Jindrich, ter Meulen Jan, Lasters Ignace, Carsetti Rita, Peiris Malik, de Kruif John, Goudsmit Jaap
Crucell Holland BV, Leiden, The Netherlands.
PLoS One. 2008;3(12):e3942. doi: 10.1371/journal.pone.0003942. Epub 2008 Dec 16.
The hemagglutinin (HA) glycoprotein is the principal target of protective humoral immune responses to influenza virus infections but such antibody responses only provide efficient protection against a narrow spectrum of HA antigenic variants within a given virus subtype. Avian influenza viruses such as H5N1 are currently panzootic and pose a pandemic threat. These viruses are antigenically diverse and protective strategies need to cross protect against diverse viral clades. Furthermore, there are 16 different HA subtypes and no certainty the next pandemic will be caused by an H5 subtype, thus it is important to develop prophylactic and therapeutic interventions that provide heterosubtypic protection.
Here we describe a panel of 13 monoclonal antibodies (mAbs) recovered from combinatorial display libraries that were constructed from human IgM(+) memory B cells of recent (seasonal) influenza vaccinees. The mAbs have broad heterosubtypic neutralizing activity against antigenically diverse H1, H2, H5, H6, H8 and H9 influenza subtypes. Restriction to variable heavy chain gene IGHV1-69 in the high affinity mAb panel was associated with binding to a conserved hydrophobic pocket in the stem domain of HA. The most potent antibody (CR6261) was protective in mice when given before and after lethal H5N1 or H1N1 challenge.
The human monoclonal CR6261 described in this study could be developed for use as a broad spectrum agent for prophylaxis or treatment of human or avian influenza infections without prior strain characterization. Moreover, the CR6261 epitope could be applied in targeted vaccine strategies or in the design of novel antivirals. Finally our approach of screening the IgM(+) memory repertoire could be applied to identify conserved and functionally relevant targets on other rapidly evolving pathogens.
血凝素（HA）糖蛋白是流感病毒感染保护性体液免疫反应的主要靶点，但此类抗体反应仅能有效抵御给定病毒亚型内有限范围的HA抗原变体。诸如H5N1之类的禽流感病毒目前呈大流行态势，并构成了大流行威胁。这些病毒在抗原性上具有多样性，保护策略需要对不同的病毒进化枝提供交叉保护。此外，有16种不同的HA亚型，且无法确定下一次大流行是否由H5亚型引起，因此开发能够提供异源亚型保护的预防和治疗干预措施非常重要。
在此，我们描述了一组从组合展示文库中筛选出的13种单克隆抗体（mAb），该文库由近期（季节性）流感疫苗接种者的人IgM(+)记忆B细胞构建而成。这些单克隆抗体对多种抗原性不同的H1、H2、H5、H6、H8和H9流感亚型具有广泛的异源亚型中和活性。高亲和力单克隆抗体组中对可变重链基因IGHV1-69的限制与结合HA茎区保守疏水口袋有关。最有效的抗体（CR6261）在致死性H5N1或H1N1攻击前后给予小鼠时具有保护作用。
本研究中描述的人源单克隆抗体CR6261可被开发用作预防或治疗人类或禽流感感染的广谱药物，无需事先对毒株进行鉴定。此外，CR6261表位可应用于靶向疫苗策略或新型抗病毒药物的设计。最后，我们筛选IgM(+)记忆库的方法可应用于识别其他快速进化病原体上保守且功能相关的靶点。
