Antibody pressure by a human monoclonal antibody targeting the 2009 pandemic H1N1 virus hemagglutinin drives the emergence of a virus with increased virulence in mice.
Antibody pressure by a human monoclonal antibody targeting the 2009 pandemic H1N1 virus hemagglutinin drives the emergence of a virus with increased virulence in mice.
复制标题
作者：
O'Donnell CD;Vogel L;Wright A;Das SR;Wrammert J;Li GM;McCausland M;Zheng NY;Yewdell JW;Ahmed R;Wilson PC;Subbarao K
2009年，一种新型H1N1甲型流感病毒（2009 pH1N1）出现并引起大流行。从一名重症 2009 pH1N1 病毒感染患者中分离出一种人单克隆抗体（hMAb；EM4C04），对 2009 pH1N1 病毒血凝素 (HA) 具有高度特异性。我们假设在 EM4C04 的免疫压力下，2009 pH1N1 病毒将发生抗原漂移并在识别抗体结合位点的位点发生突变。为此，我们在 EM4C04 存在的情况下感染 MDCK 细胞，并产生 11 个逃逸突变体，在 HA 中显示 7 个不同的氨基酸取代。六种取代大大降低了 MAb 结合（K123N、D131E、K133T、G134S、K157N 和 G158E）。残基 131、133 和 134 与球状结构域结构中的残基 157 和 158 相邻，并构成新的 pH1N1 抗体表位。受体结合位点附近的一个突变 S186P 增加了 HA 与受体的结合亲和力。 186P 和 131E 存在于高毒力的 1918 病毒 HA 中，最近被鉴定为小鼠传代的 pH1N1 病毒的毒力决定簇。我们发现，与野生型 2009 pH1N1 病毒相比，表达这些替换的 pH1N1 逃逸变体增强了小鼠体内的复制和致死率。这些病毒毒力的增加与α2,3唾液酸受体的亲和力增加有关。我们的研究表明，针对 2009 pH1N1 HA 的 Sa 区域中的新表位的 hMAb 产生的抗体压力能够无意中驱动具有改变的受体结合特性的毒性更强的病毒的发展。这拓宽了我们对抗原漂移的理解。流感病毒在称为抗原漂移的过程中积累氨基酸取代以逃避抗体反应，因此有必要每年接种流感疫苗。绘制人单克隆抗体 (hMAb) 表位图谱是了解人类抗原漂移的必要步骤。我们定义了专门针对 2009 pH1N1 病毒的 hMAb 的特异性，并描述了一个新的表位。此外，我们还发现了抗体逃逸增强病毒致病性的潜力，这一点以前未被认识到。我们通过体外免疫压力鉴定的逃逸突变是由其他研究人员使用非免疫小鼠体内选择独立报告的。尽管体外产生的逃逸突变体不太可能完全再现抗原漂移，但数据表明，针对 2009 年大流行 H1N1 病毒血凝素中新表位的人单克隆抗体的压力可能会无意中驱动逃逸突变体的发展，其中一部分具有增加的毒力和改变的受体结合特性。
In 2009, a novel H1N1 influenza A virus (2009 pH1N1) emerged and caused a pandemic. A human monoclonal antibody (hMAb; EM4C04), highly specific for the 2009 pH1N1 virus hemagglutinin (HA), was isolated from a severely ill 2009 pH1N1 virus-infected patient. We postulated that under immune pressure with EM4C04, the 2009 pH1N1 virus would undergo antigenic drift and mutate at sites that would identify the antibody binding site. To do so, we infected MDCK cells in the presence of EM4C04 and generated 11 escape mutants, displaying 7 distinct amino acid substitutions in the HA. Six substitutions greatly reduced MAb binding (K123N, D131E, K133T, G134S, K157N, and G158E). Residues 131, 133, and 134 are contiguous with residues 157 and 158 in the globular domain structure and contribute to a novel pH1N1 antibody epitope. One mutation near the receptor binding site, S186P, increased the binding affinity of the HA to the receptor. 186P and 131E are present in the highly virulent 1918 virus HA and were recently identified as virulence determinants in a mouse-passaged pH1N1 virus. We found that pH1N1 escape variants expressing these substitutions enhanced replication and lethality in mice compared to wild-type 2009 pH1N1 virus. The increased virulence of these viruses was associated with an increased affinity for α2,3 sialic acid receptors. Our study demonstrates that antibody pressure by an hMAb targeting a novel epitope in the Sa region of 2009 pH1N1 HA is able to inadvertently drive the development of a more virulent virus with altered receptor binding properties. This broadens our understanding of antigenic drift. Influenza viruses accumulate amino acid substitutions to evade the antibody response in a process known as antigenic drift, making it necessary to vaccinate against influenza annually. Mapping human monoclonal antibody (hMAb) epitopes is a necessary step towards understanding antigenic drift in humans. We defined the specificity of an hMAb that specifically targeted the 2009 pH1N1 virus and describe a novel epitope. In addition, we identified a previously unappreciated potential for antibody escape to enhance the pathogenicity of a virus. The escape mutation that we identified with in vitro immune pressure was independently reported by other investigators using in vivo selection in nonimmune mice. Although in vitro generation of escape mutants is unlikely to recapitulate antigenic drift in its entirety, the data demonstrate that pressure by a human monoclonal antibody targeting a novel epitope in the hemagglutinin of the 2009 pandemic H1N1 virus can inadvertently drive the development of escape mutants, of which a subset have increased virulence and altered receptor binding properties.