Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
Core Facility for Protein Production and X-ray Structural Analysis, Academia Sinica, Taipei, Taiwan.
Sci Rep. 2019 Mar 14;9(1):4546. doi: 10.1038/s41598-019-40937-4.
Influenza is a contagious acute respiratory disease caused by the influenza virus infection. Hemagglutinin (HA) is an important target in the therapeutic treatment and diagnostic detection of the influenza virus. Influenza A virus encompasses several different HA subtypes with different strains, which are constantly changing. In this study, we identified a fully human H1N1 neutralizing antibody (32D6) via an Epstein-Barr virus-immortalized B cell-based technology. 32D6 specifically neutralizes the clinically isolated H1N1 strains after the 2009 pandemic but not the earlier strains. The epitope was identified through X-ray crystallographic analysis of the 32D6-Fab/HA1 complex structure, which revealed a unique loop conformation located on the top surface of HA. The major region is composed of two peptide segments (residues 172-177 and 206-213), which form an abreast loop conformation. The residue T262 between the two loops forms a conformational epitope for recognition by 32D6. Three water molecules were observed at the interface of HA and the heavy chain, and they may constitute a stabilizing element for the 32D6-HA association. In addition, each 32D6-Fab is likely capable of blocking one HA trimer. This study provides important information on the strain specificity of 32D6 for the therapeutic treatment and detection of viral infection.
流感是由流感病毒感染引起的传染性急性呼吸道疾病。血凝素 (HA) 是流感病毒治疗和诊断检测的重要靶点。甲型流感病毒包含几种不同的具有不同株系的 HA 亚型，这些株系在不断变化。在这项研究中，我们通过基于 Epstein-Barr 病毒永生化 B 细胞的技术鉴定了一种全人源 H1N1 中和抗体 (32D6)。32D6 特异性中和 2009 年大流行后的临床分离的 H1N1 株，但不中和早期株。通过 32D6-Fab/HA1 复合物结构的 X 射线晶体学分析鉴定了表位，该分析揭示了位于 HA 顶面的独特环构象。主要区域由两个肽段（残基 172-177 和 206-213）组成，形成并列环构象。两个环之间的残基 T262 形成 32D6 识别的构象表位。在 HA 和重链的界面观察到三个水分子，它们可能构成 32D6-HA 结合的稳定元素。此外，每个 32D6-Fab 可能能够阻止一个 HA 三聚体。这项研究为 32D6 治疗病毒感染的治疗和检测提供了有关其株系特异性的重要信息。
