Characterization of swine-origin H1N1 canine influenza viruses

Host switch events of influenza A viruses (IAVs) continuously pose a zoonotic threat to humans. In 2013, swine-origin H1N1 IAVs emerged in dogs soon after they were detected in swine in the Guangxi province of China. This host switch was followed by multiple reassortment events between these H1N1 and previously circulating H3N2 canine IAVs (IAVs-C) in dogs. To evaluate the phenotype of these newly identified viruses, we characterized three swine-origin H1N1 IAVs-C and one reassortant H1N1 IAV-C. We found that H1N1 IAVs-C predominantly bound to human-type receptors, efficiently transmitted via direct contact in guinea pigs and replicated in human lung cells. Moreover, the swine-origin H1N1 IAVs-C were lethal in mice and were transmissible by respiratory droplets in guinea pigs. Importantly, sporadic human infections with these viruses have been detected, and preexisting immunity in humans might not be sufficient to prevent infections with these new viruses. Our results show the potential of H1N1 IAVs-C to infect and transmit in humans, suggesting that these viruses should be closely monitored in the future.

甲型流感病毒（influenza A viruses, IAVs）的宿主转换事件持续对人类构成人畜共患病威胁。2013年，在中国广西省猪群中检出猪源性H1N1亚型甲型流感病毒后不久，该病毒便在犬群中出现。此次宿主转换事件发生后，这些H1N1毒株与犬群中此前流行的H3N2亚型犬源性甲型流感病毒（influenza A viruses in dogs, IAVs-C）发生了多次重配事件。为评估此类新鉴定病毒的表型特征，我们对3株猪源性H1N1亚型IAVs-C及1株重配型H1N1 IAVs-C进行了系统表征。研究结果显示，H1N1 IAVs-C主要结合人类型受体，可通过直接接触途径在豚鼠中高效传播，并能在人肺细胞中完成复制。此外，猪源性H1N1 IAVs-C对小鼠具有致死性，且可通过呼吸道飞沫途径在豚鼠中实现传播。尤为重要的是，目前已检测到零星的人类感染此类病毒的病例，且人群预存免疫可能不足以抵御这类新型病毒的感染。本研究结果表明，H1N1 IAVs-C具备在人类中感染与传播的潜力，提示未来需对这类病毒开展密切监测。