Characterization and phylogenetic analysis of neuraminidase gene in isolated avian influenza viruses of H9N2 subtype from Iran

Avian Influenza (AI) is a viral respiratory disease of poultry industry that cause great economic losses in worldwide. In this study, the neuraminidase (NA) gene of two H9N2 avian influenza virus (AIV) strains (A/Chicken/Iran/ZMT-101/1998 and A/Chicken/Iran/NGV-1/2006), isolated from AI infected poultry farms in 1998 and 2006, were cloned and sequenced. Amino acids at hemadsorbing (HB) site of these isolates showed some differences between them and also with other Iranian isolates. No insertion or deletion or shortening in the stalk region of the NA gene were observed. Phylogenetic analysis showed that N2 gene of these strains, belonged to the same A/Qail/HongKong/G1/97-like virus sublineage. However, these strains were allocated in two different groups in the same sublineage. These results indicate that the N2 gene and protein sequences of the recently isolated H9N2 strain (NGV-1/2006) have substantial variation compared to the previous Iranian reported H9N2 strain (ZMT-101/1998). These changes may cause some new biologic and immunologic characteristics for AIVs, such as reduction of vaccination efficacy in immunized chickens. Therefore, evaluation of important genes and protective efficacy of used H9N2 vaccine strain used in Iran would be crucial