Sequence and phylogenetic analysis of (PB1) gene in Iranian H9N2 avian influenza viruses



Background: Viral (H9N2) polymerase complex in Avian influenza viruses is composed of the PB1, PB2, and PA protein subunits. These subunits are crucial for viral transcription and replication.The PB1 subunit forms the core of the polymerase complex. It plays a key role in RNA synthesis. Objectives: Survey on molecular characterization of PB1 gene in H9N2 viruses and determination of genetic relationship between Iranian H9N2 viruses and other Asian viruses. Methods: Seven H9N2 viruses were isolated from commercial broiler chickens in Iran during 2008-2009 and their PB1 genes were analyzed by RT-PCR and sequencing. Meanwhile, nucleotide sequences (Open Reading Frame: orf) of the PB1 genes were used for phylogenetic tree construction. Results: Phylogenetic analysis of the PB1 gene showed that all Iranian viruses form a separate unknown sublineage. On the other hand, while nucleotide sequence comparisons indicated high genetic diversity in Iranian viruses, a close homology (95-96%) was shown with H5 or H7 subtypes when compared with established H9N2 Eurasian sublineages (G1, Korean and Y280-like). Conclusions: The results indicate that H9N2 viruses in Iran have undergone striking reassortment to generate some new genotypes.