Herring Belinda L, Bernardin Flavien, Caglioti Sally, Stramer Susan, Tobler Leslie, Andrews William, Cheng Lawrence, Rampersad Sarah, Cameron Cherie, Saldanha John, Busch Michael P, Delwart Eric
Blood Systems Research Institute, San Francisco, CA 94118, USA.
Virology. 2007 Jun 20;363(1):220-8. doi: 10.1016/j.virol.2007.01.019. Epub 2007 Feb 26.
West Nile Virus (WNV) collected from 179 human blood donors in 25 US states and three Canadian provinces during the 2003 and 2004 epidemic seasons were genetically analyzed. The evolution of WNV during its Western spread was examined by envelope (E) gene sequencing of all 179 cases and full open reading frame sequencing of a subset of 20 WNV to determine if geographic and temporal segregation of distinct viral variants had occurred. Median joining network analysis was used to examine the genetic relationship between E gene variants and identified four large genetic clusters showing the gradual accumulation of mutations during the virus' western expansion. Two related WNV variants and their descendents, undetected in prior years, expanded in frequency. Apparent founder effects were observed in some regional outbreaks possibly due to local WNV colonization by a limited number of viruses. Amino acid mutations associated with newly expanding genetic variants reflect either selectively neutral mutational drift and/or mutations providing replicative advantages over the previously dominant forms of WNV.
对2003年和2004年流行季节期间从美国25个州和加拿大3个省的179名人类献血者身上采集的西尼罗河病毒（WNV）进行了基因分析。通过对所有179个病例的包膜（E）基因测序以及对20个WNV子集的完整开放阅读框测序，研究了WNV在其向西传播过程中的进化情况，以确定是否发生了不同病毒变体的地理和时间隔离。采用中位数连接网络分析来研究E基因变体之间的遗传关系，并确定了四个大型遗传簇，显示出病毒在向西扩张过程中突变的逐渐积累。两种相关的WNV变体及其后代，在前几年未被检测到，其频率有所增加。在一些局部疫情中观察到明显的奠基者效应，这可能是由于有限数量的病毒在当地的WNV定殖所致。与新出现的扩展遗传变体相关的氨基酸突变反映了选择性中性突变漂移和/或提供比以前占主导地位的WNV形式更具复制优势的突变。
