Reassortment and Mutation of the Avian Influenza Virus Polymerase PA Subunit Overcome Species Barriers
Reassortment and Mutation of the Avian Influenza Virus Polymerase PA Subunit Overcome Species Barriers
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DOI：
10.1128/jvi.06203-11
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发表时间：
2012-02-01
影响因子：
5.4
通讯作者：
Doudna, Jennifer A.
中科院分区：
文献类型：
--
作者：
Mehle, Andrew;Dugan, Vivien G.;Doudna, Jennifer A.
随着病毒从动物宿主转移到人类，新型大流行甲型流感病毒的出现需要克服跨物种传播的障碍。这个复杂的过程是由个体基因突变和基因组重配驱动的。病毒聚合酶复合物由蛋白质 PB1、PB2 和 PA 组成，是控制宿主适应的主要因素，过去大流行的病毒中也发生过涉及聚合酶基因片段的重配事件。在这里，我们研究聚合酶重配恢复人类细胞中通常受损的禽流感病毒聚合酶活性的能力。我们的数据表明，将人源 PA 亚基替换为禽流感病毒聚合酶可减轻对人类细胞的限制并增加体外聚合酶活性。与 2009 年大流行 H1N1 PA 蛋白的重配是最活跃的。突变分析表明，人 PA 活性增强的大部分原因是残基 552 处的苏氨酸变为丝氨酸。与含有完全禽聚合酶复合物的病毒相比，具有禽类聚合酶和人 PA 亚基的重配病毒（或简单的 T552S 突变）在培养物中表现出更快的复制动力学，并且在小鼠中的致病性增加。因此，获得人类 PA 亚基或特征性 T552S 突变是克服禽类聚合酶物种特异性限制并增加病毒复制的潜在机制。我们的数据表明，目前在猪群中共同传播的人类、禽类、猪和 2009 H1N1 类病毒为 PA 重组奠定了基础，有可能产生具有扩大的趋向性和增强的致病性的新型病毒。
The emergence of new pandemic influenza A viruses requires overcoming barriers to cross-species transmission as viruses move from animal reservoirs into humans. This complicated process is driven by both individual gene mutations and genome reassortments. The viral polymerase complex, composed of the proteins PB1, PB2, and PA, is a major factor controlling host adaptation, and reassortment events involving polymerase gene segments occurred with past pandemic viruses. Here we investigate the ability of polymerase reassortment to restore the activity of an avian influenza virus polymerase that is normally impaired in human cells. Our data show that the substitution of human-origin PA subunits into an avian influenza virus polymerase alleviates restriction in human cells and increases polymerase activity in vitro. Reassortants with 2009 pandemic H1N1 PA proteins were the most active. Mutational analyses demonstrated that the majority of the enhancing activity in human PA results from a threonine-to-serine change at residue 552. Reassortant viruses with avian polymerases and human PA subunits, or simply the T552S mutation, displayed faster replication kinetics in culture and increased pathogenicity in mice compared to those containing a wholly avian polymerase complex. Thus, the acquisition of a human PA subunit, or the signature T552S mutation, is a potential mechanism to overcome the species-specific restriction of avian polymerases and increase virus replication. Our data suggest that the human, avian, swine, and 2009 H1N1-like viruses that are currently cocirculating in pig populations set the stage for PA reassortments with the potential to generate novel viruses that could possess expanded tropism and enhanced pathogenicity.