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.
ABSTRACT
Objective@#To investigate the molecular characteristics and tracing of the hemagglutinin (HA) gene, and to analyze the risk of human infection with influenza virus A (H7N9) in Guizhou Province, so that to provide evidence for the prevention and control of highly pathogenic avian influenza A (H7N9).@*Methods@#Nucleic acids of 5 strains of H7N9 including 1 sample of the patient′s nasopharyngeal swab and 4 samples of the live poultry market (LPM) environment were extracted and HA genes were amplified and sequenced. Then the homology, genetic evolution and the pivotal sites related to receptor binding regions, pathogenicity and potential glycosylation of the avian influenza A (H7N9) viruses were analyzed by a series of bioinformatics softwares.@*Results@#Homology analysis revealed that the homologies of nucleotide and amino-acid of the HA gene of H7N9 strains from the patient and LPM in Weining County, Guizhou Province were 99.8% and 99.6%, respectively, while those of 4 strains from LPM were both 100%. The homologies of nucleotide and amino-acid of the HA gene of H7N9 strains were the highest with the strain of A/Guangxi/5/2017 isolated from a Guangxi infected patient (99.7%-99.9% and 99.4%-99.8%, respectively), while those with the strain isolated from LPMs environment at the end of 2016 (A/Environment/Guangdong/C16283222/2016) were 99.0%-99.2% and 98.9%-99.2%, respectively. However, the homologies of nucleotide and amino-acid of the HA gene of H7N9 strains with A/Shanghai/2/2013 recommended by world health organization and the candidate vaccine strain A/Anhui/1/2013 were 96.8%-97.0% and 95.8%-96.2%, respectively. Phylogenetic analysis showed that the 5 strains had the nearest genetic distance to the strain A/Guangxi/5/2017. All the 5 strains cleavage site sequences of HA protein showed mutation of PEVPKRKRTAR↓GLF, and they were highly pathogenic avian influenza viruses mutant strains, which all had mutation of G186V at the receptor binding sites of HA gene, while no Q226L mutation was found. All 5 strains had new mutation of A363S, and new mutations of R56K and I297V were only found in the strain isolated from the patient. Among the five potential glycosylation motifs in the HA, only 421NWT and 493NNT had variation of the position post shift.@*Conclusions@#All the 5 H7N9 strains isolated in Weining County, Guizhou Province are highly pathogenic avian influenza mutative viruses. The current candidate vaccine may not provide a very good protection. The mutations of cleavage site of HA protein, G186V as well as other new mutation sites of HA may enhance the susceptibility and pathogenicity to human beings.