Laboratory of Virology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
Center for Medical Biotechnology, VIB, Ghent, Belgium.
Sci Rep. 2017 May 2;7(1):1323. doi: 10.1038/s41598-017-01512-x.
Avian H9N2 and 2009 pandemic H1N1 (pH1N1) influenza viruses can infect pigs and humans, raising the concern that H9N2:pH1N1 reassortant viruses could emerge. Such reassortants demonstrated increased replication and transmissibility in pig, but were still inefficient when compared to pH1N1. Here, we evaluated if a reassortant virus containing the hemagglutinin and neuraminidase of A/quail/Hong Kong/G1/1997 (H9N2) in the A/California/04/2009 (pH1N1) backbone could become better adapted to pigs by serial passaging. The tropism of the original H9N2:pH1N1 (P0) virus was restricted to the nasal mucosa, with no virus detected in the trachea or lungs. Nevertheless, after seven passages the H9N2:pH1N1 (P7) virus replicated in the entire respiratory tract. We also compared the transmissibility of H9N2:pH1N1 (P0), H9N2:pH1N1 (P7) and pH1N1. While only 2/6 direct-contact pigs showed nasal virus excretion of H9N2:pH1N1 (P0) ≥five days, 4/6 direct-contact animals shed the H9N2:pH1N1 (P7). Interestingly, those four animals shed virus with titers similar to those of the pH1N1, which readily transmitted to all six contact animals. The broader tissue tropism and the increased post-transmission replication after seven passages were associated with the HA-D225G substitution. Our data demonstrate that the pH1N1 internal-protein genes together with the serial passages favour H9N2 virus adaptation to pigs.
禽流感 H9N2 和 2009 年大流行 H1N1（pH1N1）流感病毒可感染猪和人类，这引起了人们的担忧，即 H9N2:pH1N1 重组病毒可能会出现。这些重组病毒在猪中的复制和传播能力增强，但与 pH1N1 相比仍然效率低下。在这里，我们评估了一种含有 A/quail/Hong Kong/G1/1997（H9N2）血凝素和神经氨酸酶的重组病毒（A/California/04/2009（pH1N1）骨架）是否可以通过连续传代更好地适应猪。原始 H9N2:pH1N1（P0）病毒的嗜性仅限于鼻黏膜，气管或肺部未检测到病毒。然而，经过七次传代后，H9N2:pH1N1（P7）病毒在整个呼吸道中复制。我们还比较了 H9N2:pH1N1（P0）、H9N2:pH1N1（P7）和 pH1N1 的传染性。虽然只有 2/6 只直接接触的猪出现 H9N2:pH1N1（P0）≥五天的鼻病毒排泄，但 4/6 只直接接触的动物排出了 H9N2:pH1N1（P7）。有趣的是，这四只动物排出的病毒滴度与 pH1N1 相似，很容易传播给所有六只接触动物。经过七次传代后，更广泛的组织嗜性和复制后传播增加与 HA-D225G 取代有关。我们的数据表明，pH1N1 内部蛋白基因与连续传代一起促进了 H9N2 病毒对猪的适应。
