Department of Emerging Infectious Diseases, United States Army Medical Research Directorate-Africa, Nairobi, Kenya.
Centre for Virus Research, Kenya Medical Research Institute, Nairobi, Kenya.
PLoS One. 2024 Aug 22;19(8):e0301956. doi: 10.1371/journal.pone.0301956. eCollection 2024.
The West Nile virus (WNV), primarily transmitted by mosquitoes, is one of the most widespread flaviviruses globally, with past outbreaks occurring in the USA and Europe. Recent studies in parts of Africa, including Kenya, have identified the West Nile virus Koutango lineage (WN-KOUTV) among phlebotomine sandfly populations, however, our understanding of this virus remains limited. This study aimed to characterize WN-KOUTV from phlebotomine sandflies. Sandflies were sampled between 12th -16th March 2021 and 16th -20th March 2023 from six villages each in Baringo and Isiolo Counties, using CDC light traps. Female sandflies were taxonomically identified and pooled based on genus and site of collection. Virus isolation was performed in Vero cells. Viral genomes were determined using next-generation sequencing. Phylogenetic and molecular clock analyses were done to decipher the virus's evolutionary relationships. Comparative analyses of amino acid sequences were performed to determine variations. Protein modeling in Pymol was conducted to elucidate variations in key protein regions. Evolutionary pressure analysis investigated the selection pressures on the virus. In vitro experiments were done to investigate the virus growth kinetics in mammalian Vero E6 and mosquito C6/36 cells. We report the isolation of WN-KOUTV from Salabani in Baringo and Aremet in Isiolo, Kenya. The isolated WN-KOUTVs clustered with previously identified WN-KOUTV strains. Comparative analysis revealed a unique amino acid at NS5 653. The WN-KOUTV lineage as a whole is under purifying selective pressure, with diversifying pressure acting at site NS3 267. The current WN-KOUTV replicated in Vero E6 and C6/36 cells comparable to West Nile virus Lineage 1a, isolated from mosquitoes. Subsequent isolations of WN-KOUTV in phlebotomine sandflies suggest potential vectors, however, vector competence studies would confirm this. Replication in mammalian and insect cell lines suggests there may exist a vector/host relationship. We speculate the close genetic relationship of WN-KOUTV strains from East and West Africa may potentially be enabled by bird migratory routes between the two regions. If proven, this could point to a potential future pandemic pathway for this virus.
西尼罗河病毒（WNV）主要通过蚊子传播，是全球分布最广泛的黄病毒之一，过去曾在美国和欧洲爆发过疫情。最近在非洲部分地区（包括肯尼亚）的研究中，在白蛉种群中发现了西尼罗河病毒库坦戈谱系（WN-KOUTV），但我们对该病毒的了解仍然有限。本研究旨在对来自白蛉的 WN-KOUTV 进行特征描述。2021 年 3 月 12 日至 16 日和 2023 年 3 月 16 日至 20 日，在肯尼亚巴林戈和伊西奥洛县的六个村庄，使用 CDC 诱捕器采集了白蛉。根据属和采集地点对雌性白蛉进行分类鉴定和分组。在 Vero 细胞中进行病毒分离。使用下一代测序确定病毒基因组。进行系统发育和分子钟分析以阐明病毒的进化关系。进行氨基酸序列比较分析以确定变异。使用 Pymol 进行蛋白质建模以阐明关键蛋白区域的变异。进行进化压力分析以研究病毒的选择压力。进行体外实验以研究哺乳动物 Vero E6 和蚊子 C6/36 细胞中的病毒生长动力学。我们报告了从肯尼亚巴林戈的萨拉巴尼和伊西奥洛的阿雷梅特分离出的 WN-KOUTV。分离出的 WN-KOUTV 与先前鉴定的 WN-KOUTV 株聚类。比较分析显示 NS5 653 处存在独特的氨基酸。整个 WN-KOUTV 谱系受到纯化选择压力的影响，而在 NS3 267 处存在多样化压力。当前的 WN-KOUTV 在 Vero E6 和 C6/36 细胞中复制，与从蚊子中分离出的西尼罗河病毒 1a 谱系相当。在白蛉中随后分离出的 WN-KOUTV 表明存在潜在的传播媒介，但媒介效能研究将证实这一点。在哺乳动物和昆虫细胞系中的复制表明可能存在媒介/宿主关系。我们推测，来自东非和西非的 WN-KOUTV 株之间的密切遗传关系可能是由这两个地区之间的鸟类迁徙路线促成的。如果得到证实，这可能指向该病毒未来潜在的大流行途径。
