title: Evolutionary characterization of hemagglutinin gene of H9N2 influenza viruses isolated from Asia.
abstract: The full length hemagglutinin (HA) genes of 287 H9N2 AI strains isolated from chickens in Asia during the period 1994-2009 were genetically analyzed. Phylogenetic analysis showed that G1-like viruses circulated in the Middle East and Indian sub-continent countries, whereas other sublineages existed in Far East countries. It also revealed G1-like viruses with an average 96.7% identity clustered into two subgroups largely based on their time of isolation. The Ka/Ks ratio was calculated 0.34 for subgroup 1 and 0.57 for subgroup 2 indicates purifying/stabilizing selection, but despite this there is evidence of localized positive selection when comparing the subgroups 1 and 2 protein sequences. Five sites in HA H9N2 viruses had a posterior probability >0.5 using the Bayesian method, indicating these sites were under positive selection. These sites were found to be associated with the globular head region of HA. To identify sites under positive selection; amino acid substitution classified depends on their radicalism and neutrality. The results indicate that, although most positions in HAs were under purifying selection and can be eliminated, a few positions located in the antigenic regions and receptor binding sites were subject to positive selection.
authors: Razi Vaccine & Serum Research Institute, P.O. Box 31975-148, Karaj, Iran.
authors: Shahla
authors: S
authors: Shahsavandi
authors: Ali-Hatef
authors: AH
authors: Salmanian
authors: Seyed Ali
authors: SA
authors: Ghorashi
authors: Shahin
authors: S
authors: Masoudi
authors: Mohammad Majid
authors: MM
authors: Ebrahimi
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D001208:Asia; D001483:Base Sequence; D002645:Chickens / Q000821:virology; D019143:Evolution, Molecular; D005838:Genotype; D006388:Hemagglutinins / Q000235:genetics*; D053127:Influenza A Virus, H9N2 Subtype / Q000235:genetics* / Q000302:isolation & purification; D005585:Influenza in Birds / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D011201:Poultry Diseases / Q000821:virology; D012641:Selection, Genetic / Q000235:genetics
chemical_list: D006388:Hemagglutinins