Laboratory of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-Ku, Tokyo, Japan.
Laboratory of Infectious Diseases, School of Veterinary Medicine, Azabu University, Kanagawa, Japan.
Sci Rep. 2024 Aug 13;14(1):18750. doi: 10.1038/s41598-024-69509-x.
In 2004, the equine-origin H3N8 canine influenza virus (CIV) first caused an outbreak with lethal cases in racing greyhounds in Florida, USA, and then spread to domestic dogs nationwide. Although transmission of this canine virus to humans has not been reported, it is important to evaluate its zoonotic potential because of the high contact opportunities between companion dogs and humans. To gain insight into the interspecies transmissibility of H3N8 CIV, we tested its adaptability to human respiratory A549 cells through successive passages. We found that CIV acquired high growth properties in these cells mainly through mutations in surface glycoproteins, such as hemagglutinin (HA) and neuraminidase (NA). Our reverse genetics approach revealed that HA2-K82E, HA2-R163K, and NA-S18L mutations were responsible for the increased growth of CIV in human cells. Molecular analyses revealed that both HA2 mutations altered the optimum pH for HA membrane fusion activity and that the NA mutation changed the HA-NA functional balance. These findings suggest that H3N8 CIV could evolve into a human pathogen with pandemic potential through a small number of mutations, thereby posing a threat to public health in the future.
2004 年，马源 H3N8 犬流感病毒（CIV）首先在美国佛罗里达州导致了具有致命病例的赛狗爆发，并随后在全国范围内传播到了家养犬。虽然这种犬流感病毒尚未传播给人类，但评估其人畜共患潜力很重要，因为伴侣犬与人类之间有很高的接触机会。为了深入了解 H3N8 CIV 的种间传播能力，我们通过连续传代测试了其对人呼吸道 A549 细胞的适应性。我们发现，CIV 通过表面糖蛋白（如血凝素（HA）和神经氨酸酶（NA））的突变，主要在这些细胞中获得了高生长特性。我们的反向遗传学方法表明，HA2-K82E、HA2-R163K 和 NA-S18L 突变负责 CIV 在人细胞中的生长增加。分子分析表明，这两种 HA2 突变改变了 HA 膜融合活性的最佳 pH 值，而 NA 突变改变了 HA-NA 功能平衡。这些发现表明，H3N8 CIV 可能通过少数突变进化成具有大流行潜力的人类病原体，从而对未来的公共卫生构成威胁。
