Molecular characterization and phylogenetic analysis of neuraminidase gene of avian Influenza H9N2 viruses isolated from commercial broiler chicken in Iran during a period of 1998-2007

Avian influenza (AI) outbreaks due to H9N2 subtype of avian influenza virus (AIV)  occurred in poultry industry in Iran, throughout the  past  decade and caused serious economic losses as a result of decreased egg production, increased mortality and the cost of vaccination in Iranian poultry industry. Our aim was to find the phylogenic and genetic relationships among avian influenza viruses recently isolated from poultry in Iran with other Asian H9N2 lineages (1998-2007). The complete nucleotide sequences of the neuraminidase (NA) genes of ten H9N2 influenza virus strain isolated from diseased chickens in different farms in Iran during 1998-2007, were amplified and sequenced and phylogenetic relationships between these and  previously  reported  N2 genes were investigated. The viruses surface glycoprotein genes was >90% similar to those of A/Quail/Hongkong/G1/97 (H9N2) lineage. The NA stalks regions in these viruses had no deletion or insertion or shortening as compared to that A/DK/HK/Y280/97 lineage (CK/Bei-like viruses) and the 2 human isolates A/HK/1073/99, A/HK/1074/99. The hemadsorbing site of NA had up to 3 amino acid substitution and is different from those of earlier Iranian viruses and ten Iranian isolates possessed seven potential glycosylation sites like the most H9N2 isolates. Phylogenetic analysis of NA gene showed that they belonged to the same A/Quail/Hong Kong/G1/97 like virus sub lineage.   Key words: Avian influenza virus, H9N2, neuraminidase gene, phylogenetic analysis, Iran.