Genetic characteristics analysis of hemagglutinin gene of H9N2 subtype avian influenza viruses in Guizhou province / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To understand the genetic variation and the prevalence of H9N2 subtype avian influenza virus in Guizhou province, and to provide the scientific evidence for the prevention and control of avian influenza virus.Methods:The results of AIV detection in live poultry market(LPM) environment in Guizhou province from October 2018 to March 2019 were statistically analyzed, RNAs were extracted and sequenced from the HA genes of 13 samples of H9N2 positive screened by real-time PCR. Then the homology, the genetic evolution and the mutations of important amino acid were analyzed by bioinformation softwares. Results:The positive rate of AIV was 52.2% and the positive rate of H9N2 was 83.7% in LPM environment. The homology between nucleotides of the HA gene of 21 strains ranged from 91.6% to 100.0%, and the homology between amino acids of the HA gene ranged from 91.0% to 100.0%. All strains belonged to Y280 sublineage and G57 genotype. Key sites analysis showed that they had a common motif PSRSSRGLF and LSRSSRGLF at the cleavage site, which indicated that they were lentogenic and low pathogenic strains. Mutations H191N, E198T/A and Q234L at the receptor binding sites in the HA was found in 21 strains, while indicated the viruses had the potential to bind human-like receptor. The analysis results of glycosylation motifs showed that all 21 strains had 7 glycosylation sites, but had a site deletion at amino acid site 218 and an addition at 313.There was no significant mutation in the key site compared with the human infected strains. Conclusions:The detection rate of AIV in LPM environment in Guizhou province was high, and the pollution was very serious, and H9N2 subtype is the main subtype, All H9N2 subtype AIVs belonged to Y280 sublineage and G57 genotype, and they were low pathogenic avian influenza viruses in Guizhou province, but the genetic gap were widening and mutations of key amino acid site might enhance susceptibility and pathogenicity to human beings. Hence, It is necessary to strengthen the surveillance of molecular characteristic variation of H9N2 subtype AIV.