College of Marine Science, Shandong University (Weihai), Weihai, People's Republic of China.
Department of Epidemiology, School of Public Health, Fudan University, Shanghai, People's Republic of China.
PLoS One. 2019 Aug 12;14(8):e0220249. doi: 10.1371/journal.pone.0220249. eCollection 2019.
Since 2013, epidemics caused by novel H7N9 avian influenza A viruses (AIVs) have become a considerable public health issue. This study investigated the evolution of these viruses at the population level. Compared to H7 and N9 before 2013, there were 18 and 24 substitutions in the majority of novel H7N9 AIVs, respectively. Nine of these in HA and six in NA were rare before 2013, and four of these in HA and two in NA displayed host tropism. S136(128)N and A143(135)V are located on the receptor binding sites of the HA1 subunit and might be important factors in determining the host species of novel H7N9 AIV. On an overall scale, the evolution of H7 and N9, both in terms of time distribution and host species, is under negative selection. However, both in HA and NA, several sites were under positive selection. In both the overall epidemics and the human-derived H7N9 AIVs, eight positive selection sites were identified in HA1, with some located within the known antigen epitopes or the receptor binding site(RBS) domain. This may induce variations in H7N9 AIV with positive selection. It is necessary to strengthen the surveillance of novel H7N9 AIVs, both in human and bird population to determine whether a new virus has emerged through selection pressure and to prevent future epidemics from occurring.
自 2013 年以来，新型 H7N9 禽流感 A 型病毒（AIV）引发的疫情已成为一个相当严重的公共卫生问题。本研究调查了这些病毒在人群水平上的进化情况。与 2013 年之前的 H7 和 N9 相比，新型 H7N9 AIV 中有 18 个和 24 个取代，其中 9 个在 HA 和 6 个在 NA 中在 2013 年之前是罕见的，其中 4 个在 HA 和 2 个在 NA 中显示出宿主嗜性。S136(128)N 和 A143(135)V 位于 HA1 亚基的受体结合位点上，可能是决定新型 H7N9 AIV 宿主物种的重要因素。总体而言，H7 和 N9 的进化，无论是在时间分布还是宿主物种方面，都受到负选择的影响。然而，在 HA 和 NA 中，有几个位点受到正选择的影响。在整个疫情和人源 H7N9 AIV 中，在 HA1 中鉴定出了 8 个正选择位点，其中一些位于已知的抗原表位或受体结合位点（RBS）域内。这可能会导致具有正选择的 H7N9 AIV 发生变异。有必要加强对人类和鸟类人群中新型 H7N9 AIV 的监测，以确定是否有新病毒通过选择压力而出现，并防止未来发生疫情。
