مقايسه توالي اسيدهاي آمينه در محل شكسته شدن پروتيين هماگلوتينين سه ويروس آنفلوآنزاي طيور H9N2( )

Amino acid sequence analysis of cleavage site of hemagglutinin protein in three avian influenza viruses (H9N2)

Since 1998, Iranian poultry industry has been affected by avian influenza (AI) virus,subtype H9N2. The association of high mortality with these outbreaks in the field raised the specter of a possible new genetic modified AI virus. In this study, three AI viruses (H9N2) isolated from the broiler flocks with different mortality rates were characterized.The 486 bp PCR products containing the cleavage site of hemagglutinin (HA) protein were generated and sequenced to determine molecular characterization of the isolates.Sequence analysis of main region ofHAl gene of three isolates showed that the viruses had similar sequences at the cleavage site. However, none of the isolates were identical at the nucleotide as well as amino acid levels. Phylogenefic analysis of 453 bp nucleotide region of the PCR products revealed that Iranian AI viruses had very close relationship to each other indicating these came from the common source. Moreover, the maximum genetic similarity of these viruses was observed with AI viruses from Saudi Arabia, Germany and Pakistan, respectively. Overall, the results indicate that with the exception of some Chinese isolates the current status of Iranian AI viruses resembles to other Eurasian H9N2 viruses and in spite of different nucleotide sequences among the viruses there is no evidence for existence of new AI pathotype.