Antigenic relationships among Nigerian strains of West Nile virus by complement fixation and agar gel precipitation techniques.

Using two serological techniques, eight Nigerian West Nile virus isolates were investigated to determine antigenic relationships among them, and to find out if these virus isolates were related to West Nile virus strains from the different zoogeographic areas of the world. One virus differed significantly from the seven other strains and was later found to be a strain of Usutu virus. The remaining strains were differentiated into two serological intratypic groups depending on their cross reactions with two strains which served as prototypes for each group. Five virus isolates which constitute one of the antigenic groups were found to be related to the Egypt 101 strain of West Nile virus originating from general Palearctic zone (European and Middle East). The other two virus isolates did not show any relationship to the strains from any of the different zoogeographic zones.     

Phylogenetic analysis of West Nile virus isolates, Italy, 2008-2009

To determine the lineage of West Nile virus that caused outbreaks in Italy in 2008 and 2009, several West Nile virus strains were isolated from human specimens and sequenced. On the basis of phylogenetic analyses, the strains isolated constitute a distinct group within the western Mediterranean cluster.     

Fatal neurologic disease and abortion in mare infected with lineage 1 West Nile virus, South Africa

In 2010, lineage 1 West Nile virus was detected in South Africa in the brain of a pregnant mare that succumbed to neurologic disease and in her aborted fetus, suggesting an association with abortion in horses. All West Nile virus strains previously detected in horses and humans in South Africa were lineage 2.     

Antigenic relationship of West Nile strains by titre ratios calculated from cross-neutralization test results

The antigenic relationship of ten South African West Nile isolates, the South African prototype virus H442, the Egyptian strain EG101 and the Indian strain G2266 were compared using titre ratios. The titre ratios or 'R' values were calculated from heterologous and homologous neutralization titres and expressed as a percentage. Substantial antigenic differences were demonstrated between the South African prototype strain and the majority of the recently obtained South African isolates, seven of which were fairly closely related and possibly form a distinct antigenic sub-set. The recent isolates also differed from the Egyptian and Indian West Nile isolates. The heterologous results between the South African West Nile strains and the Indian strain G2266 suggest that prior infection with an Indian West Nile virus would give poor protection against the South African viruses, whereas the reverse would not be so.     

西尼罗病毒特异性抗原片段筛选及ELISA方法的研究

目的筛选西尼罗病毒特异抗原片段,并建立其ELISA快检方法。方法参考亲水性、抗原性、可塑性、表面可及性及二级结构信息,对西尼罗病毒抗原表位进行系统分析,预测得分值较高的抗原区域经原核表达、Western blot筛选及亲和层析纯化后,包被ELISA微孔板,对ELISA反应条件进行系统优化,建立其ELISA快检方法。结果预测获病毒特异性抗原表位29个,对其中11段进行了表达,经筛选,获得西尼罗病毒特异抗原片段及西尼罗与乙型脑炎病毒共同抗原片段各一段。利用西尼罗病毒特异抗原片段WnAg16建立了检测西尼罗病毒抗体的ELISA方法,与所试相近病毒无交叉反应,S/N比值均在23以上,对鼠抗西尼罗病毒多抗的检出下限达1∶204 800。结论利用特异性抗原初步建立了检测西尼罗病毒抗体的ELISA方法。     

West Nile virus in Morocco, 2003

West Nile virus (WNV) reemerged in Morocco in September 2003, causing an equine outbreak. A WNV strain isolated from a brain biopsy was completely sequenced. On the basis of phylogenetic analyses, Moroccan WNV strains isolated during the 1996 and 2003 outbreaks were closely related to other strains responsible for equine outbreaks in the western Mediterranean basin.     

Infection of the mosquito Aedes aegypti with infectious west Nile virus-antibody complexes

Aedes aegypti fed through chick skin membranes on West Nile virus-homologous antiserum mixtures shown by an anti-globulin neutralization test to be highly infectious complexes (in terms of plaque formation in tissue culture) failed to become infected. Control mosquitoes fed on West Nile virus—normal rabbit serum mixtures containing similar or smaller amounts of infectious virus were shown to become infected.Mosquitoes ingesting suspensions of West Nile virus previously incubated with Murray Valley encephalitis or Ntaya antiserum became infected at significantly lower rates (P = < 0.05) than controls ingesting West Nile virus—normal rabbit serum mixtures.West Nile virus—17D yellow fever or dengue—2 antiserum mixtures did not produce significantly reduced infection rates in Ae. aegypti when compared to controls.     

TaqMan荧光定量RT—PCR快速检测西尼罗病毒的研究

目的建立特异、快速、灵敏的TaqMan实时荧光定量聚合酶链反应（TaqMan—based Real—timePCR）用于西尼罗病毒（WNV）核酸检测，为WNV的感染诊断和流行病学监测奠定技术基础。方法根据文献公开发表的WNV核酸检测引物和TaqMan探针，优选最佳引物探针。应用DNAWorks2．4在线软件设计8条寡核苷酸片段，基于PCR合成包含引物探针扩增区域的230个核苷酸作为WNV模拟核酸。并对TaqMan-based Real—timePCR条件进行优化，验证该方法的特异性、灵敏度。结果该方法对WNV核酸检测有高度特异性，与流行性乙型脑炎、登革热1～4型等虫媒病毒均无交叉反应，对构建的DNA检测灵敏度达100拷贝／反应。结论TaqMan—based Real—timePCR是一种快速检测WNV特异、敏感的方法，适用于WNV的早期感染诊断和流行病学监测。     

Isolation of West Nile virus from the brains of children who had died of encephalitis

The isolation of West Nile virus from the brain tissue of three children who died of encephalitis in Mysore and Kolar districts of Karnataka State, India, is reported. This is the first such report from India. The significance of these isolations with reference to the role of West Nile virus in encephalitis in children in southern India is discussed.     

West Nile virus in Mexico: evidence of widespread circulation since July 2002

West Nile virus (WNV) antibodies were detected in horses from five Mexican states, and WNV was isolated from a Common Raven in the state of Tabasco. Phylogenetic studies indicate that this isolate, the first from Mexico, is related to strains from the central United States but has a relatively high degree of sequence divergence.     

Phylogenetic analysis of West Nile virus, Nuevo Leon State, Mexico

West Nile virus RNA was detected in brain tissue from a horse that died in June 2003 in Nuevo Leon State, Mexico. Nucleotide sequencing and phylogenetic analysis of the premembrane and envelope genes showed that the virus was most closely related to West Nile virus isolates collected in Texas in 2002.     

Entomological studies along the Colorado Front Range during a period of intense West Nile virus activity

To better understand the ecology of West Nile virus transmission in Northern Colorado, field studies were conducted in Larimer and Weld counties from September 2003 through March 2005. During summer studies, 18,540 adult mosquitoes were collected using light traps and gravid traps. West Nile virus RNA was detected in 24 of the 2,140 mosquito pools tested throughout the study area in 2003 and 2004. Culex tarsalis had the highest minimum infection rate (MIR) in both 2003 (MIR = 34.48) and in 2004 (MIR = 8.74). During winter studies, 9,391 adult mosquitoes were collected by aspirator from various overwintering sites including bridges and storm drains. The most frequently collected species was Culex pipiens. West Nile virus was not detected in our overwintering collections. The relationship between spring adult emergence and temperature inside and outside overwintering sites is described. Species composition of collections as well as the spatial and temporal distribution of West Nile virus detections are presented.     

Mental status after West Nile virus infection

Mental status after acute West Nile virus infection has not been examined objectively. We compared Telephone Interview for Cognitive Status scores of 116 patients with West Nile fever or West Nile neuroinvasive disease. Mental status was poorer and cognitive complaints more frequent with West Nile neuroinvasive disease (p = 0.005).     

Migratory birds and spread of West Nile virus in the Western Hemisphere

West Nile virus, an Old World flavivirus related to St. Louis encephalitis virus, was first recorded in the New World during August 1999 in the borough of Queens, New York City. Through October 1999, 62 patients, 7 of whom died, had confirmed infections with the virus. Ornithophilic mosquitoes are the principal vectors of West Nile virus in the Old World, and birds of several species, chiefly migrants, appear to be the major introductory or amplifying hosts. If transovarial transmission or survival in overwintering mosquitoes were the principal means for its persistence, West Nile virus might not become established in the New World because of aggressive mosquito suppression campaigns conducted in the New York area. However, the pattern of outbreaks in southern Europe suggests that viremic migratory birds may also contribute to movement of the virus. If so, West Nile virus has the potential to cause outbreaks throughout both temperate and tropical regions of the Western Hemisphere.     

美国西尼罗病毒监测及我国国境口岸实施监测的策略

目的为有效地开展我国国境口岸西尼罗病毒监测这项新工作，防止并延缓西尼罗病毒传入我国。方法对美国199％2000年的西尼罗病毒监测工作方法、经验进行分析研究。结果美国西尼罗病毒监测的成功经验非常值得我国在国境口岸开展西尼罗病毒监测借鉴。结论积极开展我国国境口岸西尼罗热的监测及其它虫媒病毒的监测和管理工作。     

Co-circulation of two Usutu virus strains in Northern Italy between 2009 and 2014

Usutu virus is an arbovirus closely related to West Nile virus (genus Flavivirus), which circulates between mosquitoes and wild birds. This virus has been increasingly reported in Europe, raising concerns for its possible pathogenic potential for wild birds and humans. This study reports the whole genome sequences of 15 strains of USUV, isolated between 2010 and 2014 from mosquitoes and wild birds in the course of West Nile virus surveillance in the Emilia-Romagna and Lombardy regions of Northern Italy. Both whole and 656 partial genome sequences, obtained from isolated viruses and field samples (mosquitoes and wild birds), were analyzed to describe the temporal and geographical spread of USUV in the surveyed area. The detected sequences belonged to two groups, with one circulating primarily in the northwestern part of the area and the other in the southeastern part. This pattern is likely the result of different routes of introduction from the North (over the Alps) and from the East, respectively. The phylogenetic analysis of obtained sequences and other European sequences demonstrated that the majority of European strains belonged to one main clade, while less common strains, mainly from Western Europe, fell in other two clades. This analysis strongly suggested an autochthonous evolution process of strains of the main clade from a common ancestor with an estimated time of arrival in Europe at the beginning of the 1990s.In addition to causing mass mortality in wild birds, Usutu virus can infect humans and can sporadically cause disease. These factors and the endemization of the Usutu virus in a large area of Europe, sustained by the obtained data, strongly support the need to adequately survey Usutu virus in areas in which its circulation is detected.     

西尼罗病毒E蛋白的结构和应用进展

西尼罗病毒是一种单股正链RNA病毒,属于黄病毒属黄病毒科,主要通过库蚊传播,能引起西尼罗热及神经侵袭性疾病如脑炎、脑膜炎等。近年来,该病毒在多个国家和地区间广泛流行,给发病国家带来了极大的危害。目前对于西尼罗病毒尚未有可用于人类的疫苗上市,也没有特定的抗病毒药物可用,因此加强病毒监测、研发新的疫苗及掌握实验室诊断方法变得尤为重要。本文主要通过对西尼罗病毒E蛋白的结构、疫苗及检测方法的最新进展加以探讨,为研发西尼罗病毒疫苗及诊断试剂盒提供理论依据。     

Serologic evidence of West Nile virus infection in horses,Coahuila State,Mexico

Serum samples were obtained from 24 horses in the State of Coahuila, Mexico, in December 2002. Antibodies to West Nile virus were detected by epitope-blocking enzyme-linked immunosorbent assay and confirmed by plaque reduction neutralization test in 15 (62.5%) horses. We report the first West Nile virus activity in northern Mexico.     

Serologic evidence of West Nile virus infection in horses,Yucatan State,Mexico

Serum samples were obtained from 252 horses in the State of Yucatan, Mexico, from July to October 2002. Antibodies to West Nile virus were detected by epitope-blocking enzyme-linked immunosorbent assays in three (1.2%) horses and confirmed by plaque reduction neutralization test. We report the first West Nile virus activity in the State of Yucatan.