Jia Manxue, Zhao Hanjun, Morano Nicholas C, Lu Hong, Lui Yin-Ming, Du Haijuan, Becker Jordan E, Yuen Kwok-Yung, Ho David D, Kwong Peter D, Shapiro Lawrence, To Kelvin Kai-Wang, Wu Xueling
Aaron Diamond AIDS Research Center, Affiliate of Rockefeller University, New York, NY 10016, USA.
State Key Laboratory for Emerging Infectious Diseases, Carol Yu Centre for Infection, Department of Microbiology, School of Clinical Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China.
Res Sq. 2023 Nov 7:rs.3.rs-3429355. doi: 10.21203/rs.3.rs-3429355/v1.
The avian influenza A virus H7N9 causes severe human infections with more than 30% fatality despite the use of neuraminidase inhibitors. Currently there is no H7N9-specific prevention or treatment for humans. From a 2013 H7N9 convalescent case occurred in Hong Kong, we isolated four H7 hemagglutinin (HA)-reactive monoclonal antibodies (mAbs) by single B cell cloning, with three mAbs directed to the HA globular head domain (HA1) and one to the HA stem region (HA2). Two clonally related HA1-directed mAbs, H7.HK1 and H7.HK2, potently neutralized H7N9 and protected mice from a lethal H7N9/AH1 challenge. Cryo-EM structures revealed that H7.HK1 and H7.HK2 bind to a β14-centered surface partially overlapping with the antigenic site D of HA1 and disrupt the 220-loop that makes hydrophobic contacts with sialic acid on the adjacent protomer, thus affectively blocking viral entry. The more potent mAb H7.HK2 retained full HA1 binding and neutralization capacity to later H7N9 isolates from 2016-2017, which is consistent with structural data showing that the antigenic mutations of 2016-2017 from the 2013 H7N9 only occurred at the periphery of the mAb epitope. The HA2-directed mAb H7.HK4 lacked neutralizing activity but protected mice from the lethal H7N9/AH1 challenge when engineered to mouse IgG2a enabling Fc effector function in mice. Used in combination with H7.HK2 at a suboptimal dose, H7.HK4 augmented mouse protection. Our data demonstrated an allosteric mechanism of mAb neutralization and augmented protection against H7N9 when a HA1-directed neutralizing mAb and a HA2-directed non-neutralizing mAb were combined.
甲型H7N9禽流感病毒可引发严重的人类感染，即便使用神经氨酸酶抑制剂，其致死率仍超过30%。目前尚无针对人类的H7N9特异性预防或治疗方法。从2013年香港出现的一例H7N9康复病例中，我们通过单个B细胞克隆分离出四种H7血凝素（HA）反应性单克隆抗体（mAb），其中三种mAb针对HA球状头部结构域（HA1），一种针对HA茎区（HA2）。两种克隆相关的HA1导向性mAb，即H7.HK1和H7.HK2，能有效中和H7N9，并保护小鼠免受致命的H7N9/AH1攻击。冷冻电镜结构显示，H7.HK1和H7.HK2与以β14为中心的表面结合，该表面部分与HA1的抗原位点D重叠，并破坏与相邻原体上唾液酸形成疏水接触的220环，从而有效阻断病毒进入。效力更强的mAb H7.HK2对2016 - 2017年的后期H7N9分离株仍保留完全的HA1结合和中和能力，这与结构数据一致，表明2016 - 2017年相对于2013年H7N9的抗原突变仅发生在mAb表位的周边。HA2导向性mAb H7.HK4缺乏中和活性，但经工程改造为具有小鼠IgG2a从而在小鼠中具备Fc效应子功能时，可保护小鼠免受致命的H7N9/AH1攻击。以次优剂量与H7.HK2联合使用时，H7.HK4增强了对小鼠的保护作用。我们的数据证明了单克隆抗体中和的变构机制，以及当一种HA1导向性中和单克隆抗体和一种HA2导向性非中和单克隆抗体联合使用时增强对H7N9的保护作用。
