title: Evolutionary analysis of HA and NS1 genes of H5N1 influenza viruses in 2004-2005 epidemics.
abstract: H5N1 avian influenza viruses circulating in early 2004 in eastern Asia appeared to be under strong purifying selection, except for the hemagglutinin (HA) and nonstructural 1 (NS1) genes, where few amino acid positions were found under positive selection pressure. To evaluate whether the widespread circulation of the H5N1 viruses in the following years was accompanied by a change in the evolution of the HA and NS1, phylogenetic and positive selection analyses were performed on 89 HA and 57 NS1 sequences. Results showed that the number of HA positively selected sites decreased compared to 2004; no selection pressure for NS1 was found. These findings suggest a possible change in the adaptation of the H5N1 virus to birds.
authors.affiliation: Department of Infectious, Parasitic and Immunomediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena, 299, Rome 00161, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Ciccozzi
authors.forename: Stefania
authors.initials: S
authors.lastname: Montieri
authors.forename: Marzia
authors.initials: M
authors.lastname: Facchini
authors.forename: Giovanni
authors.initials: G
authors.lastname: Rezza
authors.forename: Isabella
authors.initials: I
authors.lastname: Donatelli
authors.forename: Laura
authors.initials: L
authors.lastname: Campitelli
mesh_terms: D000818:Animals; D001717:Birds / Q000821:virology; D004196:Disease Outbreaks / Q000662:veterinary*; D019143:Evolution, Molecular; D005814:Genes, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics*; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics*; D005585:Influenza in Birds / Q000821:virology*; D010802:Phylogeny; D013997:Time Factors; D017361:Viral Nonstructural Proteins / Q000235:genetics*
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; C085820:INS1 protein, influenza virus; D017361:Viral Nonstructural Proteins; C109963:hemagglutinin, avian influenza A virus