Mutations in NA That Induced Low pH-Stability and Enhanced the Replication of Pandemic (H1N1) 2009 Influenza A Virus at an Early Stage of the Pandemic

An influenza A virus that originated in pigs caused a pandemic in 2009. The sialidase activity of the neuraminidase (NA) of previous pandemic influenza A viruses are stable at low pH (≤5). Here, we identified the amino acids responsible for this property. We found differences in low-pH stability at pH 5.0 among pandemic (H1N1) 2009 viruses, which enhanced the replication of these viruses. Low-pH-stable NA enhancement of virus replication may have contributed to the rapid worldwide spread and adaptation to humans of pandemic (H1N1) 2009 viruses during the early stages of the 2009 pandemic.2009年引发全球大流行的甲型流感病毒起源于猪群。既往大流行甲型流感病毒的神经氨酸酶（neuraminidase, NA）所具备的唾液酸酶活性（sialidase activity），在低pH（≤5）环境下可维持稳定。本研究鉴定出了赋予该酶该低pH稳定特性的氨基酸残基。研究发现，2009年甲型（H1N1）大流行病毒株之间在pH 5.0条件下的低pH稳定性存在差异，该差异可增强这类病毒的复制能力。低pH稳定型NA所介导的病毒复制增强效应，或是2009年甲型（H1N1）大流行病毒在大流行早期能够实现全球快速传播并适应人类宿主的重要原因。