Molecular characterization of non-structural gene of H9N2 subtype of avian influenza viruses isolated from broiler chickens in Iran

BACKGROUND: The H9N2 subtype of avian influenzaviruses (AIVs) have spread in Asia and Middle East countriesand have become a serious threat to poultry industry in Iran.OBJECTIVES:Characterization of genes of H9N2 subtype involvingin pathogenicity and diagnosis are crucial in control of avianinfluenza outbreaks. The Nonstructural (NS) gene and its proteinproducts (NS1 & NS2) are important as diagnostic marker, lifecycle and pathogenicity of AIVs. METHODS:The NS gene of fivestrains, isolated from 1998 to 2010, were completely sequencedand analyzed. RESULTS:All of the examined strains were composedof 890 nucleotides with 230 amino acids. In this regard, onlytwo Iranian strains from GeneBank had 217 amino acids in NS1protein. All Iranian H9N2 strains subdivided into two distinctsublineages including I and II. Comparative analysis of NS genesof Iranian strains showed that since 2003, they might haveoriginated from Pakistan H7N3 strains; whereas from 2008 theycould be originated from Pakistan H9N2 strains. CONCLUSIONS:Although the low pathogenic H9N2 subtype has been permanentlycirculating from 1998 to the present in Iran, phylogeneticanalysis of NS genes revealed that sublineage II has circulatedmore in poultry industry of Iran. These epidemio-logicallyvariations could be related to vaccination pressure due tomassive vaccination or NS gene reassortment in rural andbackyard chickens.