Auguste Albert J, Pybus Oliver G, Carrington Christine V F
Department of Preclinical Sciences, Faculty of Medical Sciences, University of the West Indies, St Augustine, Trinidad and Tobago.
Infect Genet Evol. 2009 Jul;9(4):709-15. doi: 10.1016/j.meegid.2008.07.006. Epub 2008 Jul 29.
Using a Bayesian coalescent approach on a dataset of 73 envelope gene sequences we estimated substitution rates and dates of divergence for St. Louis encephalitis virus (SLEV) in the Americas. We found significant rate heterogeneity among lineages, such that "relaxed" molecular clock models were much better supported than a strict molecular clock. The mean substitution rate estimated for all SLEV was 4.1x10(-4)substitutions/site/year (95% HPD 2.5-5.7)-higher than previous estimates that relied on the less well-suited strict clock. Mean substitution rates for individual lineages varied from 3.7x10(-4) to 7.2x10(-4)substitutions/site/year. For the first time we also assessed the magnitude and direction of viral gene flow within the Americas. The overall direction of gene flow during the period represented by the phylogeny is from South to North, and the region between 15 degrees N and 30 degrees N latitude appears to be the major source of virus for the rest of North America, which is consistent with migratory birds returning to their northern breeding grounds having acquired infection while wintering in the region of the Gulf of Mexico.
我们采用贝叶斯合并方法，对73个包膜基因序列数据集进行分析，估算了美洲圣路易斯脑炎病毒（SLEV）的替换率和分化日期。我们发现不同谱系间存在显著的速率异质性，因此“宽松”分子钟模型比严格分子钟模型得到了更好的支持。所有SLEV的平均替换率估计为4.1×10⁻⁴替换/位点/年（95%最高后验密度区间为2.5 - 5.7），高于之前依赖不太合适的严格时钟的估计值。各个谱系的平均替换率在3.7×10⁻⁴至7.2×10⁻⁴替换/位点/年之间。我们首次还评估了美洲内部病毒基因流动的规模和方向。系统发育所代表时期内基因流动的总体方向是从南向北，北纬15度至30度之间的区域似乎是北美其他地区病毒的主要来源，这与候鸟在墨西哥湾地区越冬感染后返回其北方繁殖地的情况一致。
