Analysis of the hemagglutinin and neuraminidase genes of human Influenza A/H3N2 viruses circulating in iran between 2005 and 2007: antigenic and phylogenetic relationships to vaccine strains.

OBJECTIVES To study the antigenic variations in influenza A/H3N2 viruses circulating in Iran for characterization and phylogenetic relationships to vaccine strains. METHODS RT-PCR, full sequencing of hemagglutinin (HA) and neuraminidase (NA) genes and analysis by sequence handling and phylogenetic programs were done. RESULTS The HA sequences of 2007 isolates fell within the clade represented by the HA of A/Brisbane/10/07 and characterized by the amino acid changes relative to the HA of A/Wisconsin/67/05, G50E and K140I. The only isolate in 2006 fell within A/Berlin/02/06 with V112I and K173E changes. The 2005 isolates characterized by Y159F, S189N and S227P changes within A/California/07/04. In all isolates we had E190D which is important because this was responsible for the loss of ability of A/H3N2 viruses to bind to chicken red blood cells. There were some substitutions in the antigenic sites of the HA. Similar to other studies, conserved residues for catalytic sites and also framework sites of NA supporting the catalytic residues were detected. We had some changes in the variable regions of the NA head domain. CONCLUSION Comparison between Iranian viruses and vaccine strains showed high similarity between them and vaccine strains used in the northern hemisphere.