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J Microbiol Immunol Infect. 2015 Feb;48(1):28-35. doi: 10.1016/j.jmii.2013.12.002. Epub 2014 Feb 21.

Cleavage site stability of Egyptian highly pathogenic avian influenza viruses in backyard chickens during 2009-2011.

Author information

1
Department of Avian and Rabbit Medicine, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
2
Department of Virology, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
3
Department of Zoonoses, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
4
Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD 57007, USA.
5
Department of Avian and Rabbit Medicine, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt. Electronic address: amalaeid@yahoo.com.

Abstract

PURPOSE:

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.

METHODS:

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.

RESULTS:

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).

CONCLUSION:

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.

KEYWORDS:

Backyard chicken; Egypt; H5N1; Hemagglutinin gene; Highly pathogenic avian influenza

PMID:
24560697
DOI:
10.1016/j.jmii.2013.12.002
[Indexed for MEDLINE]
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