Department of Avian and Rabbit Medicine, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
Department of Virology, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
J Microbiol Immunol Infect. 2015 Feb;48(1):28-35. doi: 10.1016/j.jmii.2013.12.002. Epub 2014 Feb 21.
Two distinguishable subclades of H5N1 (classic and variant strains) are cocirculating among the poultry populations in Egypt despite the intensive vaccination programs. A study to investigate the genetic relationship between avian influenza virus (AIV) isolates from backyard chickens in Sharkia (2009-2011), subclades, and commercially available vaccines was carried out.
Forty-eight suspected AIV infected birds were clinically examined and used for virus isolation followed by reverse transcription-polymerase chain reaction. Four H5N1 virus isolates were sequenced and analyzed. The intravenous pathogenicity index (IVPI) of three AIV isolates was determined.
Thirty-four hemagglutinating viral agents (30 AIV subtype H5N1 and 4 Newcastle disease virus) were detected. Both the nucleotide and amino acid sequence identities of four H5N1 virus isolates (SHZA-0412/2009, SHZA-0801/2010, SHMK-1903/2010, and SHAH-1403/2011) were high--98.4-99.7% and 100%, respectively--indicative of their genetic homogeneity. The hemagglutinin cleavage site characterization revealed the presence of multiple basic amino acids (-PQRERRRKKR/GL-) of the highly pathogenic phenotype. These results were supported by IVPI in chickens of 2.69-2.90. The similarity of our isolates with H5N1 AIV vaccine strains (93.9-95.1%) was higher than that with H5N2 strains (77.8-91.9%). The divergence of four sequences with classic and variant lineages is 2-2.7% and 2.3-3%, respectively, with two amino acid substitutions (A249P and N251Y).
Genetic characterization and IVPI data of backyard H5N1 isolates are indicative of a highly pathogenic avian influenza virus with hemagglutinin cleavage site constancy and two amino acids substitutions with Egyptian classic and variant lineages, suggesting a beginning of antigenic drift.
尽管实施了强化疫苗接种计划，但埃及家禽群体中仍同时存在 H5N1 的两个可区分亚群（经典株和变异株）。本研究旨在调查来自 Sharkia 地区后院鸡（2009-2011 年）的禽流感病毒（AIV）分离株、亚群以及市售疫苗之间的遗传关系。
对 48 只疑似感染 AIV 的禽类进行临床检查，并进行病毒分离，然后进行逆转录聚合酶链反应。对 4 株 H5N1 病毒分离株进行测序和分析。测定了 3 株 AIV 分离株的静脉致病性指数（IVPI）。
检测到 34 种血凝病毒（30 株 AIV 亚型 H5N1 和 4 株新城疫病毒）。4 株 H5N1 病毒分离株（SHZA-0412/2009、SHZA-0801/2010、SHMK-1903/2010 和 SHAH-1403/2011）的核苷酸和氨基酸序列同一性均很高，分别为 98.4-99.7%和 100%，表明其遗传同质性。血凝素裂解位点特征表明，存在高度致病性表型的多个碱性氨基酸（-PQRERRRKKR/GL-）。鸡的 IVPI 为 2.69-2.90，支持这一结果。与 H5N1 AIV 疫苗株（93.9-95.1%）相比，我们的分离株与 H5N2 株（77.8-91.9%）的相似性更高。与经典和变异谱系相比，4 个序列的差异分别为 2-2.7%和 2.3-3%，有两个氨基酸取代（A249P 和 N251Y）。
后院 H5N1 分离株的遗传特征和 IVPI 数据表明，具有血凝素裂解位点稳定性和与埃及经典和变异谱系的两个氨基酸取代的高致病性禽流感病毒已经开始出现抗原漂移。
