Sequencing and genetic analysis of hemagglutinin gene of H9 avian influenza viruses from Iran (2008 to 2011)

Abstract Objective To survey on molecular characterization of Hemagglutinin(HA) gene in H9N2 viruses and determine genetic relationship between Iranian H9N2 viruses and other Asian viruses. Methods Ten H9N2 viruses were isolated from commercial broiler chickens in Iran during 2008-2011 and their HA genes were analyzed by reverse transcription-polymerase chain reaction and sequencing. Meanwhile, nucleotide sequences (open reading frame) of the HA genes were used for phylogenetic tree construction. Results All the isolates possessed the same amino acid motif -R-S-S-R/G-L- at the cleavage site of HA and possessed H at amino acid position 183, A and T at position 190, S at position 138, whereas the representative strains of the other sublineage (except CK/HK/G1/97-like) of H9N2 viruses had N, E, and A at these positions respectively. Phylogenetic analysis of HA genes showed that it shared a common ancestor Qa/HK/G1/97 isolate which had contributed internal genes of human H5N1 viruses. Conclusions The present results indicated the HA genes of H9N2 influenza viruses circulating in Iran were well conserved in the past years and the earliest Iranian isolates may be considered to represent such a progenitor.