ABSTRACT
Survey of molecular characterization of nucleoprotein gene of H9N2 avian influenza viruses and determination of the genetic relationship of Iranian H9N2 viruses and other Asian viruses. The nucleoprotein [NP] genes from 4 isolates of H9N2 viruses isolated from commercial chickens in Iran during 2008-2009 were amplified by RT-PCR method and sequenced. Nucleotide sequences [orf] of the NP genes were used for phylogenetic tree construction. Nucleotide sequence analysis of the NP gene showed that the Iranian virus isolates did not exhibit insertions or deletions within nucleoprotein [NP] gene as compare with their prototype A/turkey/winconsin/66; however numerous point mutations were occurred in the gene length of these viruses similar to the previous Iranian strains. Nucleotide sequence analysis showed that these isolates are very closely related [96/7-99/6] and shared a homology of 91/9-92/3% and 91/5-92% with 2 human isolates A/HK/1073/99 and A/Hk/2108/2003, respectively. Phylogenetic analysis of the NP gene showed that all the NP genes of the Iranian H9N2 viruses fall into a single group within a G1-like sublineage which had contributed as donor of six internal genes to H5N1 a highly pathogenic avian influenza. The current study indicated that the NP gene of H9N2 influenza viruses circulating in Iran during the past years were well conserved. It seems that the differences between these Iranian virus isolates are the result of accumulation of point mutations among them