North American West Nile virus genotype isolates demonstrate differential replicative capacities in response to temperature
North American West Nile virus genotype isolates demonstrate differential replicative capacities in response to temperature
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DOI：
10.1099/vir.0.032318-0
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发表时间：
2011-11-01
影响因子：
3.8
通讯作者：
Brault, Aaron C.
中科院分区：
文献类型：
--
作者：
Andrade, Christy C.;Maharaj, Payal D.;Brault, Aaron C.
西尼罗病毒（WNV）于2003年夏季首次在美国加利福尼亚州被发现，随后该病毒已成为该州的地方性流行病。序列分析表明，流行的菌株是北美（WN02）基因型的代表，取代了东海岸基因型（NY99）。最近的一项研究表明，在高温下增强的媒介能力可能在WN02取代东海岸基因型的过程中发挥了作用。在当前的研究中，来自加利福尼亚的4株WN02菌株，包括2003年的最初分离株（COAV997），在不同的生物学相关温度下，在蚊子和鸭胚胎成纤维细胞（DEF）细胞系中进行生长曲线测定，以评估这些天然分离株的相对温度敏感性。COAV997与NY99对照株的全长序列比较发现，COAV997在包膜糖蛋白（V159A）、非结构蛋白1 (NS1) （K110N）和非结构蛋白4A (NS4A) （F92L）中存在非同义突变，并且在3' UTR中有两个突变：C -> T在nt 10772和A -> G在nt 10851。这些非同义突变通过定点诱变被引入NY99病毒主干。含有NS1-K110N和NS4A-F92L突变的突变体在44℃时在DEF细胞中表现出生长减弱的表型，与COAV997相似。对该基因型存在的一种解释是，COAV997是从加利福尼亚的一个地区获得的，那里的鸟类宿主物种可能不会出现高温。这些数据表明，在一些WN02分离株中发现的NS1和NS4A突变可能会降低病毒在发热禽宿主中观察到的温度下的热稳定性并阻碍病毒的复制。
The presence of West Nile virus (WNV) was first documented in California, USA, during the summer of 2003, and subsequently the virus has become endemic throughout the state. Sequence analysis has demonstrated that the circulating strains are representative of the North American (WN02) genotype that has displaced the East Coast genotype (NY99). A recent study has indicated that enhanced vector competence at elevated temperatures may have played a role in the displacement of the East Coast genotype by WN02. In the current study, four WN02 strains from California, including an initial 2003 isolate (COAV997), were compared to strain NY99 in growth curve assays in mosquito and duck embryonic fibroblast (DEF) cell lines at differing, biologically relevant temperatures to assess the relative temperature sensitivities of these natural isolates. COAV997 was significantly debilitated in viral replication in DEF cells at 44 degrees C. Full-length sequence comparison of COAV997 against the NY99 reference strain revealed non-synonymous mutations in the envelope glycoprotein (V159A), non-structural protein 1 (NS1) (K110N) and non-structural protein 4A (NS4A) (F92L), as well as two mutations in the 3' UTR: C -> T at nt 10 772 and A -> G at nt 10851. These non-synonymous mutations were introduced into the NY99 viral backbone by site-directed mutagenesis. A mutant containing the NS1-K110N and NS4A-F92L mutations exhibited a debilitated growth phenotype in DEF cells at 44 degrees C, similar to that of COAV997. One explanation for the subsistence of this genotype is that COAV997 was obtained from an area of California where avian host species might not present elevated temperatures. These data indicate that the NS1 and NS4A mutations identified in some WN02 isolates could reduce thermal stability and impede replication of virus at temperatures observed in febrile avian hosts.