Dudas Gytis, Bedford Trevor, Lycett Samantha, Rambaut Andrew
Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, United Kingdom
Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA.
Mol Biol Evol. 2015 Jan;32(1):162-72. doi: 10.1093/molbev/msu287. Epub 2014 Oct 15.
Influenza B viruses make a considerable contribution to morbidity attributed to seasonal influenza. Currently circulating influenza B isolates are known to belong to two antigenically distinct lineages referred to as B/Victoria and B/Yamagata. Frequent exchange of genomic segments of these two lineages has been noted in the past, but the observed patterns of reassortment have not been formalized in detail. We investigate interlineage reassortments by comparing phylogenetic trees across genomic segments. Our analyses indicate that of the eight segments of influenza B viruses only segments coding for polymerase basic 1 and 2 (PB1 and PB2) and hemagglutinin (HA) proteins have maintained separate Victoria and Yamagata lineages and that currently circulating strains possess PB1, PB2, and HA segments derived entirely from one or the other lineage; other segments have repeatedly reassorted between lineages thereby reducing genetic diversity. We argue that this difference between segments is due to selection against reassortant viruses with mixed-lineage PB1, PB2, and HA segments. Given sufficient time and continued recruitment to the reassortment-isolated PB1-PB2-HA gene complex, we expect influenza B viruses to eventually undergo sympatric speciation.
乙型流感病毒对季节性流感所致发病情况有相当大的影响。目前已知正在传播的乙型流感病毒分离株属于两个抗原性不同的谱系，即B/维多利亚系和B/山形系。过去已注意到这两个谱系的基因组片段频繁交换，但所观察到的重配模式尚未得到详细规范。我们通过比较基因组片段的系统发育树来研究谱系间重配情况。我们的分析表明，在乙型流感病毒的八个片段中，只有编码聚合酶基本蛋白1和2（PB1和PB2）以及血凝素（HA）蛋白的片段保持了独立的维多利亚系和山形系，并且目前正在传播的毒株拥有完全源自其中一个或另一个谱系的PB1、PB2和HA片段；其他片段在谱系间反复重配，从而降低了遗传多样性。我们认为片段之间的这种差异是由于对具有混合谱系PB1、PB2和HA片段的重配病毒进行选择所致。鉴于有足够的时间以及持续纳入重配隔离的PB1 - PB2 - HA基因复合体，我们预计乙型流感病毒最终会发生同域物种形成。
