Objective To explore the molecular characteristics of human infections with H9N2 avian influenza virus (AIV) in Guizhou province, so as to provide evidence for the prevention and control of avian influenza in Guizhou province.
Methods Two human AIV samples were collected, environmental samples from the same period were collected. Real?time fluorescence quantitative reverse transcription polymerase chain reaction was used for avian influenza virus typing detection. The hemagglutinin (HA) and neuraminidase (NA) genes of the avian influenza virus were sequenced. The homology analysis， specific site, and glycosylation site analysis of the HA and NA gene sequences were completed using software such as NCBI and Mega 11.0.13.
Results The full-length HA and NA sequences of two human cases of H9N2 avian influenza and five local environmental samples from the same period were obtained. Comparison between the two human cases (GZ269 and GZ973) and local environmental samples from the same period showed that the HA gene had nucleotide homology of 90.68%-98.46% and amino acid homology of 92.16%-99.29%; the NA gene had nucleotide homology of 92.57%-98.20% and amino acid homology of 94.84%-99.14%. The HA protein cleavage site sequence of both GZ269 and GZ973 was PSRSSR↓GLF, and the H232N mutation occurred in the HA region of both GZ269 and GZ973. Amino acid deletions at positions 63-65 were observed in the NA region of both GZ269 and GZ973. The erythrocyte binding site of GZ269 showed an S369N amino acid mutation. No drug resistance mutations were found.
Conclusions The two H9N2 avian influenza strains isolated in Guizhou province were both low pathogenic AIVs, and most of the key sites were relatively conserved. The possibility of causing an epidemic in the human population was not high. Surveillance of pathogen should be carried out well, and mutation of AIV should be closely monitored