Genetic variation in West Nile virus from naturally infected mosquitoes and birds suggests quasispecies structure and strong purifying selection
Genetic variation in West Nile virus from naturally infected mosquitoes and birds suggests quasispecies structure and strong purifying selection
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DOI：
10.1099/vir.0.81015-0
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发表时间：
2005-08-01
影响因子：
3.8
通讯作者：
Ebel, GD
中科院分区：
文献类型：
--
作者：
Jerzak, G;Bernard, KA;Ebel, GD
对自然感染的蚊子和鸟类的宿主内遗传多样性进行了分析，以确定西尼罗河病毒(WNV)是否在自然界中作为准种存在，并量化了宿主内部和宿主之间的选择压力。2003年西尼罗河病毒传播高峰期，从美国纽约长岛收集的10只受感染的禽类和10个受感染的蚊子池中采集了西尼罗河病毒。扩增和克隆了西尼罗河病毒囊膜(E)编码区3‘1159个核苷酸和非结构蛋白1(NS1)编码区5’779个核苷酸的1938个核苷酸片段，每个样本20个克隆。这项分析的结果表明，西尼罗河病毒感染来自自然界中遗传多样性的基因组群体。个体内的平均核苷酸多样性为0.016%，与一致序列不同的克隆的平均百分比为19.5%。蚊子中的西尼罗河病毒序列在遗传上的多样性明显高于鸟类中的西尼罗河病毒。没有观察到特定类型突变的宿主依赖偏见，并且E和NS1编码序列之间对遗传多样性的估计没有显著差异。从两个禽类样本获得的非共识克隆具有高度相似的遗传特征，提供了初步证据，表明西尼罗河病毒的遗传多样性可能在整个地方性传播周期中保持不变，而不是在每次感染期间独立产生。从寄主内和寄主间的西尼罗河病毒种群中都获得了净化选择的证据。综合起来，这些数据支持了西尼罗河病毒种群可能被构建为准种的观察结果，并证明了西尼罗河病毒种群中强烈的净化自然选择。
Intrahost genetic diversity was analysed in naturally infected mosquitoes and birds to determine whether West Nile virus (WNV) exists in nature as a quasispecies and to quantify selective pressures within and between hosts. WNV was sampled from ten infected birds and ten infected mosquito pools collected on Long Island, NY, USA, during the peak of the 2003 WNV transmission season. A 1938 nt fragment comprising the 3' 1159 nt of the WNV envelope (E) coding region and the 5' 779 nt of the non-structural protein 1 (NS1) coding region was amplified and cloned and 20 clones per specimen were sequenced. Results from this analysis demonstrate that WNV infections are derived from a genetically diverse population of genomes in nature. The mean nucleotide diversity was 0.016 % within individual specimens and the mean percentage of clones that differed from the consensus sequence was 19.5 %. WNV sequences in mosquitoes were significantly more genetically diverse than WNV in birds. No host-dependent bias for particular types of mutations was observed and estimates of genetic diversity did not differ significantly between E and NS1 coding sequences. Non-consensus clones obtained from two avian specimens had highly similar genetic signatures, providing preliminary evidence that WNV genetic diversity may be maintained throughout the enzootic transmission cycle, rather than arising independently during each infection. Evidence of purifying selection was obtained from both intra- and interhost WNV populations. Combined, these data support the observation that WNV populations may be structured as a quasispecies and document strong purifying natural selection in WNV populations.