Genomic characteristics of H9N2 avian influenza viruses in external environment in Huainan city, 2016 / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To analyze the genomic characteristics of H9N2 subtype avian influenza virus in external environmental specimens collected in Huainan city from February to April, 2016.Methods:Specimens positive for H9N2 nucleic acid (Ct value≤30) were screened by fluorescent PCR and cultivated in chicken embryos to extract RNA. Eight gene segments were amplified and analyzed with whole genome sequencing. The molecular characteristics of each gene segment of Huainan strains were analyzed. A phylogenetic tree was constructed based on the sequences.Results:The hemagglutinin (HA) and neuramidinase (NA) genes of two Huainan H9N2 avian influenza strains and the human-derived strain A/Anhui-Lujiang/39/2018/H9N2 shared the homology of 98.2%-98.3% and 97.2%-94.9% in nucleotide and 98.9%-98.8% and 99.2%-98.6% in amino acid. The other six endogenous genes were highly homologous to those of the A/Anhui/1/2013/H7N9 and A/Anhui/33163/2016/H5N6 strains. The phylogenetic tree showed that two H9N2 subtype avian influenza strains isolated in Huainan city in 2016 belonged to G57 genotype, and the endogenous genes of two Huainan H7N9 isolates and human-derived A/Anhui/1/2013/ H7N9 and A/Anhui/33163/2016/H5N6 strains were G57-like genotype. Amino acid mutations in the HA protein receptor binding domain including S132D, K138T, T189D, V/A190T and Q226L were detected. The " TEI" sequence was deleted from the NA stem region. Amino acid mutations associated with drug resistance including H274Y, R292K and N294S were not detected in the isolates, but they carried the mutations of I550L in PA gene, I368V in PB1 gene, I504V in PB2 gene, P42S in NS1 gene, N30D and T215A in M1 gene and S31N in M2 gene.Conclusions:The two H9N2 viruses isolated in the live poultry market in Huainan city were highly homologous to the A/Anhui-Lujiang/39/2018/H9N2 strain isolated from humans. The three strains were within the same evolutionary branch and belonged to G57 genotype. The endogenous genes of the two H9N2 viruses could recombine with H7N9 and H5N6 subtype avian influenza viruses that caused human infection. Amino acid mutations in the HA protein receptor binding domain, deleted sequences in the NA stem region and increased polymerase activity strengthened the ability of viruses to infect humans and were related to the drug resistance to M2 ion channel inhibitors (adamantane). The two Huainan H9N2 viruses remained sensitive to NA inhibitors (oseltamivir phosphate).