Centre for Infections, Health Protection Agency, London, United Kingdom.
PLoS One. 2011;6(8):e23779. doi: 10.1371/journal.pone.0023779. Epub 2011 Aug 24.
The emergence of the influenza (H1N1) 2009 virus provided a unique opportunity to study the evolution of a pandemic virus following its introduction into the human population. Virological and clinical surveillance in the UK were comprehensive during the first and second waves of the pandemic in 2009, with extensive laboratory confirmation of infection allowing a detailed sampling of representative circulating viruses. We sequenced the complete coding region of the haemagglutinin (HA) segment of 685 H1N1 pandemic viruses selected without bias during two waves of pandemic in the UK (April-December 2009). Phylogenetic analysis showed that although temporal accumulation of amino acid changes was observed in the HA sequences, the overall diversity was less than that typically seen for seasonal influenza A H1N1 or H3N2. There was co-circulation of multiple variants as characterised by signature amino acid changes in the HA. A specific substitution (S203T) became predominant both in UK and global isolates. No antigenic drift occurred during 2009 as viruses with greater than four-fold reduction in their haemagglutination inhibition (HI) titre ("low reactors") were detected in a low proportion (3%) and occurred sporadically. Although some limited antigenic divergence in viruses with four-fold reduction in HI titre might be related to the presence of 203T, additional studies are needed to test this hypothesis.
2009 年甲型 H1N1 流感病毒的出现为研究该病毒在人群中传播后的进化提供了一个独特的机会。在 2009 年流感大流行的第一波和第二波期间，英国进行了全面的病毒学和临床监测，广泛的实验室感染确认允许对代表性循环病毒进行详细采样。我们对在英国大流行的两个波次（2009 年 4 月至 12 月）期间选择的 685 株甲型 H1N1 流感大流行病毒的血凝素（HA）片段的完整编码区进行了测序。系统进化分析表明，尽管在 HA 序列中观察到氨基酸变化的时间积累，但总体多样性小于季节性甲型 H1N1 或 H3N2 流感病毒。存在多种变体的共同循环，其特征是 HA 中的特征性氨基酸变化。一种特定的取代（S203T）在英国和全球分离株中均占主导地位。2009 年没有发生抗原漂移，因为在血凝抑制（HI）滴度降低四倍以上的病毒（“低反应者”）在低比例（3%）中被检测到，并且是零星出现的。尽管 HI 滴度降低四倍的病毒中存在一定程度的抗原差异可能与 203T 的存在有关，但需要进一步研究来验证这一假设。
