1Department of Avian Disease Research and Diagnostic, Razi Vaccine and Serum Research Institute, Agricultural Research Education and Extension Organization (AREEO), Karaj, Iran.
2Department of Viral Vaccine Quality Control, Razi Vaccine and Serum Research Institute, Agricultural Research Education and Extension Organization (AREEO), Karaj, Iran.
Acta Vet Hung. 2020 Sep 30;68(3):328-335. doi: 10.1556/004.2020.00048.
Despite the use of wide-scale vaccination programmes against the H9N2 virus, enzootic outbreaks of H9N2 avian influenza (AI) have often occurred and caused serious nationwide economic losses, particularly in broiler chickens. In this study, the haemagglutinin (HA) and neuraminidase (NA) genes of nine recent H9N2s and a common vaccine strain were fully sequenced and compared with other representative Iranian viruses. Phylogenetic analysis revealed that all Iranian viruses were grouped into the G1 sub-lineage with different clusters in which recent isolates (2014-2017) formed a distinct cluster compared to the vaccine group (1998-2004). All Iranian H9N2s exhibited low pathogenicity AI connecting peptide feature with an R/KSSR motif. Amino acid 226, located in the 220 loop of the receptor binding site, was leucine among the recent Iranian viruses, a characteristic of human influenza viruses. With an overall gradual increase in the genetic diversity of H9N2s, Bayesian skyline plots of Iranian HA and NA genes depicted a fluctuation and a relative stable situation, respectively. It is recommended to apply constant surveillance to assess any increase in viral human adaptation and evolutionary changes in circulating field H9N2s. Moreover, antigenic characterisation of the prevailing H9N2 viruses seems to be necessary for evaluating the possible antigenic drift from the vaccine strain.
尽管广泛使用针对 H9N2 病毒的疫苗接种计划，但 H9N2 禽流感（AI）的地方性爆发仍经常发生，并造成严重的全国性经济损失，尤其是在肉鸡中。在这项研究中，对最近的 9 株 H9N2 株和一种常见疫苗株的血凝素（HA）和神经氨酸酶（NA）基因进行了全序列测定，并与其他代表伊朗的病毒进行了比较。系统进化分析显示，所有伊朗病毒均分为 G1 亚谱系，其中不同的簇中最近的分离株（2014-2017 年）与疫苗组（1998-2004 年）形成了一个明显的簇。所有伊朗 H9N2 株均表现出低致病性 AI 连接肽特征，具有 R/KSSR 基序。位于受体结合位点 220 环中的氨基酸 226 在最近的伊朗病毒中为亮氨酸，这是人类流感病毒的特征。随着 H9N2 遗传多样性的总体逐渐增加，伊朗 HA 和 NA 基因的贝叶斯天空线图分别描绘了波动和相对稳定的情况。建议进行持续监测，以评估病毒对人类的适应能力的任何增加以及流行的 H9N2 病毒在流行领域中的进化变化。此外，对流行的 H9N2 病毒进行抗原特征分析似乎对于评估疫苗株可能的抗原漂移是必要的。
