ABSTRACT
Avian Influenza [AI] is a rival respiratory disease of poultry industry that cause great economic losses in worldwide. In this study, the neuraminidase [NA] gene of two H[9]N[2] 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 N[2] gene of these strains, belonged to the same A/Qail/Hong Kong/ G1/ 97-like virus sublineage. However, these strains were allocated in two different groups in the same sublineage. These results indicate that N2 gene and protein sequences of the recently isolated H[9]N[2] stain [NG-1/2006] have substantial variation compared to the previous Iranian reported H[9]N[2] 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 H[9]N[2] vaccine strain used in Iran would be crucial