Characterization of the Mouse Neuroinvasiveness of Selected European Strains of West Nile Virus

West Nile virus (WNV) has caused outbreaks and sporadic infections in Central, Eastern and Mediterranean Europe for over 45 years. Most strains responsible for the European and Mediterranean basin outbreaks are classified as lineage 1. In recent years, WNV strains belonging to lineage 1 and 2 have been causing outbreaks of neuroinvasive disease in humans in countries such as Italy, Hungary and Greece, while mass mortality among birds was not reported. This study characterizes three European strains of WNV isolated in Italy (FIN and Ita09) and Hungary (578/10) in terms of in vitro replication kinetics on neuroblastoma cells, LD50 values in C57BL/6 mice, median day mortality, cumulative mortality, concentration of virus in the brain and spinal cord, and the response to infection in the brain. Overall, the results indicate that strains circulating in Europe belonging to both lineage 1 and 2 are highly virulent and that Ita09 and 578/10 are more neurovirulent compared to the FIN strain.西尼罗河病毒（West Nile virus, WNV）已持续45余年在中欧、东欧及地中海欧洲区域引发暴发疫情与散发性感染病例。绝大多数导致欧洲及地中海流域暴发疫情的毒株被归类为1谱系。近年来，属于1谱系与2谱系的WNV毒株，在意大利、匈牙利、希腊等国引发了人类神经侵袭性疾病暴发，但尚未见鸟类大规模死亡的相关报道。本研究针对意大利分离的两株西尼罗河病毒（FIN株与Ita09株）以及匈牙利分离的578/10株，开展了系统性特性表征：包括神经母细胞瘤细胞的体外复制动力学、C57BL/6小鼠的半数致死量（LD50）、中位死亡天数、累计死亡率、脑与脊髓中的病毒载量，以及脑部的感染应答反应。整体研究结果表明，在欧洲流行的1谱系与2谱系毒株均具有高致病性，且Ita09株与578/10株的神经毒力强于FIN株。