Parvin Rokshana, Heenemann Kristin, Halami Mohammad Y, Chowdhury Emdadul H, Islam M R, Vahlenkamp Thomas W
Faculty of Veterinary Medicine, Institute of Virology, Center for Infectious Diseases, University of Leipzig, An den Tierkliniken 29, 04103, Leipzig, Germany.
Arch Virol. 2014 Jul;159(7):1651-61. doi: 10.1007/s00705-014-1976-8. Epub 2014 Jan 14.
Low-pathogenic avian influenza viruses (LPAIVs) of subtype H9N2 have become widespread in poultry in many Asian countries with relevance to respiratory diseases of multifactorial origin. In Bangladesh, LPAIVs of subtype H9N2 co-circulate simultaneously with highly pathogenic avian influenza viruses (HPAIVs) of subtype H5N1 in commercial and backyard poultry. The aim of this study was to characterize LPAIVs of subtype H9N2 currently circulating in Bangladesh. The selected isolate A/Chicken/Bangladesh/VP01/2006 (H9N2) was propagated in chicken embryos. All eight gene segments were amplified by RT-PCR, cloned, and subjected to full-length sequencing. The sequence data obtained were compared with reference strains available in GenBank. Phylogenetic analysis of LPAIV H9N2 from Bangladesh revealed a close relationship to Indian, Pakistani and Middle Eastern isolates and identified an ancestor relationship to LPAIV H9N2 Quail/HK/G1/1997. The internal genes M and NP belong to lineage G1, whereas NS, PA, PB1 and PB2 belong to the prototype virus A/Chicken/Korea/38349-p96323/96. The internal genes showed high sequence homology to an HPAIV of subtype H7N3 from Pakistan, whereas the PB1 gene showed similarly high nucleotide homologies to recently circulating HPAIV H5N1 from Bangladesh, revealing two independent reassortment events. Examination of the hemagglutinin cleavage site of LPAIV H9N2 confirmed its low pathogenicity. The receptor-binding sites indicated a binding preference for human-type receptors. Several mutations in internal proteins are associated with increased virulence and altered host range, while other amino acids were found to be highly conserved among LPAIV H9N2 isolates.
H9N2亚型低致病性禽流感病毒（LPAIVs）已在许多亚洲国家的家禽中广泛传播，与多因素起源的呼吸道疾病有关。在孟加拉国，H9N2亚型LPAIVs与H5N1亚型高致病性禽流感病毒（HPAIVs）在商业家禽和后院家禽中同时循环传播。本研究的目的是对目前在孟加拉国流行的H9N2亚型LPAIVs进行特征分析。选择的分离株A/Chicken/Bangladesh/VP01/2006（H9N2）在鸡胚中增殖。通过RT-PCR扩增所有八个基因片段，进行克隆并进行全长测序。将获得的序列数据与GenBank中可用的参考菌株进行比较。对来自孟加拉国的LPAIV H9N2进行系统发育分析，发现其与印度、巴基斯坦和中东分离株关系密切，并确定与LPAIV H9N2 Quail/HK/G1/1997有祖先关系。内部基因M和NP属于G1谱系，而NS、PA、PB1和PB2属于原型病毒A/Chicken/Korea/38349-p96323/96。内部基因与来自巴基斯坦的H7N3亚型HPAIV具有高度序列同源性，而PB1基因与来自孟加拉国最近流行的HPAIV H5N1具有同样高的核苷酸同源性，揭示了两个独立的重配事件。对LPAIV H9N2的血凝素裂解位点进行检查证实了其低致病性。受体结合位点表明对人源型受体有结合偏好。内部蛋白中的几个突变与毒力增加和宿主范围改变有关，而其他氨基酸在LPAIV H9N2分离株中高度保守。
