molecular characterization and phylogenetic study based on matrix gene of avian influenza viruses (h9n2) in iran during 1998-2008

background: h9n2 avian influenza viruses (aiv) a have become panzootic in eurasia over the last decade and have caused several human infections in iran since 1998 and inactivated vaccine has been used in chickens to control the disease. objectives: the purpose of this study was to analyze h9n2 viruses that have infected broiler in tehran province, iran between 1998 and 2008 based on matrix gene. methods:  the complete coding region of matrix (m) gene from 8 of h9n2 subtype isolated from chicken flocks in tehran province during 1998-2007 was amplified and sequenced. results: sequence analysis and phylogenetic studies of h9n2 viruses on the basis of data of viruses in this study and other selected strains available in the genbank were conducted and determined variations among these sequences at different levels. sequence analysis revealed a large number of similar substitution mutations and close evolutionary relation among sequences of m gene. phylogenetic analysis showed that all our isolates belonged to the g1-like sublineage. in this study, it was determined that iran’s isolates have been in two separate branches and have the most similarity with pakistan, united arab emirate and occupied palestine’s isolates. conclusions: the available evidence indicates that m genes of h9n2 circulating in iran during the past years were not well conserved. our finding emphasizes the importance of reinforcing aiv surveillance.