The low pathogenic avian influenza (LPAI) H9N2 subtype has become the most prevalent and widespread in many Asian and Middle Eastern countries. It causes an enzootic situation in commercial poultry and known as a potential facilitator virus that can be transmitted to human from birds. The neuraminidase (NA) gene plays an important role the release and spread of the virus from infected cells and throughout the bird. The complete nucleotide sequences of the NA gene of seven H9N2 viruses collected from apparent healthy chicken and quail flocks in Egypt during 2014-2015, were amplified and sequenced. The phylogenetic relationships were investigated and all viruses were belonging to the A/Q/HK/G1/97 strain (G1-like). There were no insertions or deletions or shortening in NA stalk regions when compared to Y280-lineage and the human H9N2 isolates. No obvious changes NA interactions with antiviral drugs. We found that the Egyptian H9N2 viruses have seven glycosylation sites like the most recorded H9N2 viruses in the country, except A/Q/Egypt/14864V/2014 virus which has only six. The NA has four amino acid substitutions distributed in different parts of the hemadsorbing site. The most characteristic substitutions in this site were S372A and W403R these substitutions were a distinctive feature resembling to human H9N2, H2N2 and H3N2 viruses but differs from the other avian influenza viruses. These Special features of surface glycoproteins of LPAI-H9N2 viruses refer to the tendency for enhanced introductions into humans and ensuring the importance of poultry in the transfer influenza viruses.
Keywords: (LPAI) H9N2; Avian influenza viruses; H3N2; Hemadsorbing (HB) sites; Neuraminidase gene; Phylogenetic analysis.