Molecular characteristic analysis of neuraminidase genes of avian influenza virus H9N2 in environments in Weining, Guizhou Province during 2015-2017

Abstract

Objective To understand the genetic variations of neuraminidase (NA) genes of avian influenza virus H9N2 in Weining, Guizhou Province, and to provide the scientific evidence for the prevention and control of avian influenza virus. Methods Ribonucleic acids (RNA) were extracted and NA genes were amplified and sequenced from 13 randomly selected H9N2 positive samples from the live poultry market (LPM) environments in north of Weining Yi and Hui and Miao autonomous county (Weining), Guizhou Province during 2015 to 2017. Then the homology, genetic evolution, and sites of stalk deletion areas, potential N-glycosylation, receptor binding regions and drug resistance of H9N2 subtype avian influenza viruses were analyzed by a series of bioinformation software. Results Homology analysis revealed that there were 93.0%-100.0% and 92.1%-100.0% similarity among 13 strains H9N2 avian influenza viruses in nucleotide and amino acid of the NA gene, respectively. All strains belonged to DK/HK/Y280/97 sub-lineage, but their genetic sources were complex and diverse. Thirteen strains had a stalk deletion of 3 amino acid residues TEI at positions 63-65 and 3 isolates had mutation QN to QK at positions 39-40. The potential N-glycosylation sites at amino acid residues 86, 146, 200, and 234 of the NA protein of all strains were highly conserved, while other N-glycosylation sites had quantity and site mutations. There were different mutation types at the three sialic acid binding site areas, especially at 399-404 area. All NA protease activity sites and key sites of the 13 strains had no mutations associated with resistance to the neuraminidase inhibitor drugs. Conclusions All 13 strains H9N2 viruses belongs to DK/HK/Y280/97 sub-lineage in Weining, Guizhou Province during 2015-2017, and their genetic sources are complex and diverse. The mutations on sites of stalk areas, potential N-glycosylation and sialic acid binding site areas are presented at different degrees. Hence, enhancing surveillance and controlling H9N2 avian influenza virus is necessary. Key words: Influenza A virus, H9N2 subtype; Neuraminidase gene; Molecular characteristic