Pathogenicity and haemagglutinin gene sequence analysis of Iranian avian influenza H9N2 viruses isolated during (1998–2001)

Document Type : Full paper (Original article)


1 Department of Veterinary Research and Biotechnology, Razi Vaccine and Serum Research Institute, Mashhad, Iran

2 Department of Research and Diagnosis of Avian Diseases, Razi Vaccine and Serum Research Institute, Karadj, Iran


Sixteen avian influenza (AI) H9N2 viruses were isolated from disease outbreaks in different parts of Iran
during (1998–2001). These AI isolates were used for pathogenicity, haemagglutinin (HA) gene variation and
phylogenetic analysis. Results in both pathogenicity tests and HA gene cleavage site sequence detection
represented a non-highly pathogenic feature for all Iranian AI isolates studied. The cleavage site motif (R-SS-R) of all AI isolates however, indicated that they had capability of becoming highly pathogenic viruses
following 2 nucleotide substitutions at this region. Based on 450 nucleotides region obtained for local
isolates and those for referenced viruses available in Gene Bank database used in phylogenetic analysis, all
viruses placed on 3 distinct groups, 2 for Iranian and 1 for reference viruses. Among the reference AI viruses, isolates from Pakistan, Saudi Arabia and 1 from Germany showed less differences with Iranian AI isolates. Results also revealed that the circulating viruses in neighbouring provinces have been remained with less mutation for about 2 years.