Bosco-Lauth Angela M, Kooi Kris, Hawks Seth A, Duggal Nisha K
Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado.
Wildlife Services, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Golden, Colorado.
Am J Trop Med Hyg. 2024 Dec 31;112(3):657-662. doi: 10.4269/ajtmh.24-0363. Print 2025 Mar 5.
West Nile virus (WNV), St. Louis encephalitis virus (SLEV), and Usutu virus (USUV) are zoonotic flaviviruses that cause neuroinvasive disease in humans and are maintained in overlapping avian-mosquito transmission cycles. West Nile virus and SLEV cocirculate in the United States, and WNV and USUV cocirculate in Europe. Cross-reactivity of immune responses against closely related flaviviruses is well documented. In birds, prior infection with WNV provides strong protection against SLEV genotype II and V infection, which may explain the decrease in SLEV circulation in the United States after WNV emergence in 1999. However, in 2015, a new SLEV genotype (III) emerged in the United States, suggesting that WNV immunity in birds may not provide cross-protection against this SLEV genotype. Here, we tested whether prior WNV infection protects birds against infection with SLEV genotype III, as well as USUV. First, we established a house sparrow (Passer domesticus) model of infection for SLEV genotype III. We then inoculated house sparrows with WNV and, 4 weeks later, challenged WNV-immune birds with SLEV genotype III or USUV. All birds were completely protected against secondary challenge, with no viremia detected. Low levels of cross-neutralizing antibodies against SLEV and USUV were found in the blood prior to secondary challenge. However, two naturally WNV-exposed house sparrows did develop SLEV genotype III and USUV viremia after inoculation. These results indicate that experimental WNV infection may protect birds against infection with SLEV genotype III and USUV; however, additional studies to investigate the role of avian immunity in flavivirus emergence are necessary.
西尼罗河病毒（WNV）、圣路易斯脑炎病毒（SLEV）和乌苏图病毒（USUV）是可导致人类发生神经侵袭性疾病的人畜共患黄病毒，它们在重叠的鸟类 - 蚊子传播循环中持续存在。西尼罗河病毒和圣路易斯脑炎病毒在美国共同传播，而西尼罗河病毒和乌苏图病毒在欧洲共同传播。针对密切相关黄病毒的免疫反应交叉反应性已有充分记录。在鸟类中，先前感染西尼罗河病毒可提供对圣路易斯脑炎病毒II型和V型感染的强大保护，这可能解释了1999年西尼罗河病毒出现后美国圣路易斯脑炎病毒传播的减少。然而，2015年，一种新的圣路易斯脑炎病毒基因型（III型）在美国出现，这表明鸟类中的西尼罗河病毒免疫力可能无法提供针对这种圣路易斯脑炎病毒基因型的交叉保护。在此，我们测试了先前的西尼罗河病毒感染是否能保护鸟类免受圣路易斯脑炎病毒III型以及乌苏图病毒的感染。首先，我们建立了圣路易斯脑炎病毒III型感染的家麻雀（Passer domesticus）模型。然后我们给家麻雀接种西尼罗河病毒，4周后，用圣路易斯脑炎病毒III型或乌苏图病毒对具有西尼罗河病毒免疫力的鸟类进行攻击。所有鸟类都完全免受二次攻击，未检测到病毒血症。在二次攻击前，血液中发现了针对圣路易斯脑炎病毒和乌苏图病毒的低水平交叉中和抗体。然而，两只自然暴露于西尼罗河病毒的家麻雀在接种后确实出现了圣路易斯脑炎病毒III型和乌苏图病毒血症。这些结果表明，实验性西尼罗河病毒感染可能保护鸟类免受圣路易斯脑炎病毒III型和乌苏图病毒的感染；然而，有必要进行更多研究以调查鸟类免疫在黄病毒出现中的作用。
