Molecular characterization of non-structural gene of H9N2 subtype of avian influenza viruses isolated from broiler chickens in Iran


1 Department of Poultry Diseases, Faculty of Veterinary Medicine University of Tehran, Tehran, Iran

2 Department of Clinical Sciences, Faculty of Veterinary Medicine University of Tehran, Tehran, Iran


BACKGROUND: The H9N2 subtype of avian influenza
viruses (AIVs) have spread in Asia and Middle East countries
and have become a serious threat to poultry industry in Iran.
OBJECTIVES:Characterization of genes of H9N2 subtype involving
in pathogenicity and diagnosis are crucial in control of avian
influenza outbreaks. The Nonstructural (NS) gene and its protein
products (NS1 & NS2) are important as diagnostic marker, life
cycle and pathogenicity of AIVs. METHODS:The NS gene of five
strains, isolated from 1998 to 2010, were completely sequenced
and analyzed. RESULTS:All of the examined strains were composed
of 890 nucleotides with 230 amino acids. In this regard, only
two Iranian strains from GeneBank had 217 amino acids in NS1
protein. All Iranian H9N2 strains subdivided into two distinct
sublineages including I and II. Comparative analysis of NS genes
of Iranian strains showed that since 2003, they might have
originated from Pakistan H7N3 strains; whereas from 2008 they
could be originated from Pakistan H9N2 strains. CONCLUSIONS:
Although the low pathogenic H9N2 subtype has been permanently
circulating from 1998 to the present in Iran, phylogenetic
analysis of NS genes revealed that sublineage II has circulated
more in poultry industry of Iran. These epidemio-logically
variations could be related to vaccination pressure due to
massive vaccination or NS gene reassortment in rural and
backyard chickens.