Western Equine Encephalitis Virus: Evolutionary Analysis of a Declining Alphavirus Based on Complete Genome Sequences
Western Equine Encephalitis Virus: Evolutionary Analysis of a Declining Alphavirus Based on Complete Genome Sequences
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DOI：
10.1128/jvi.01463-14
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发表时间：
2014-08-01
影响因子：
5.4
通讯作者：
Weaver, Scott C.
中科院分区：
文献类型：
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作者：
Bergren, Nicholas A.;Auguste, Albert J.;Weaver, Scott C.
西方马脑炎病毒（western equine encephalitis virus，WEEV）是披膜病毒科甲病毒属的一种虫媒病毒，在北美的鸟类和蚊子之间传播，偶尔会引起人类和马科动物的疾病。近几十年来，人类感染急剧减少;北美最后一次记录在案的人类病例发生在1994年，自2008年以来，在蚊子池中没有发现该病毒。由于有限的信息存在关于WEEV的进化，我们分析了33个低传代数菌株的基因组序列与不同的地理和时间分布，并进行了全面的系统发育分析。我们的研究结果表明，WEEV是一种高度保守的甲病毒，其最可变的基因只有约5%的分歧。我们证实了先前确定的A组和B谱系的存在，并进一步将B组分解为三个亚谱系。我们还观察到相对遗传多样性的增加，在世纪中期，这与几个组B亚系的出现和共循环。估计的WEEV种群规模在1990年代下降，在过去的20年里只对B3谱系进行了抽样。结构图谱显示，包膜糖蛋白中的大多数取代发生在E2-E2界面。我们假设，一个事件发生在世纪中期，导致WEEV在北美的遗传多样性增加，其次是遗传收缩，由于无论是竞争性位移的B3亚系或随机事件造成的人口下降。
Western equine encephalitis virus (WEEV) is an arbovirus from the genus Alphavirus, family Togaviridae, which circulates in North America between birds and mosquitoes, occasionally causing disease in humans and equids. In recent decades, human infection has decreased dramatically; the last documented human case in North America occurred in 1994, and the virus has not been detected in mosquito pools since 2008. Because limited information exists regarding the evolution of WEEV, we analyzed the genomic sequences of 33 low-passage-number strains with diverse geographic and temporal distributions and performed comprehensive phylogenetic analyses. Our results indicated that WEEV is a highly conserved alphavirus with only approximately 5% divergence in its most variable genes. We confirmed the presence of the previously determined group A and B lineages and further resolved group B into three sublineages. We also observed an increase in relative genetic diversity during the mid-20th century, which correlates with the emergence and cocirculation of several group B sublineages. The estimated WEEV population size dropped in the 1990s, with only the group B3 lineage being sampled in the past 20 years. Structural mapping showed that the majority of substitutions in the envelope glycoproteins occurred at the E2-E2 interface. We hypothesize that an event occurred in the mid-20th century that resulted in the increased genetic diversity of WEEV in North America, followed by genetic constriction due to either competitive displacement by the B3 sublineage or stochastic events resulting from a population decline.