M gene characteristics of influenza A (H1N1) pdm09 viruses from Hainan province during the 2019-2020 influenza season.

Objectives To analyze the evolution pattern of matrix (M) gene and amino acid site variation of M2 protein of influenza A (H1N1) pdm09 viruses in Hainnan province during the influenza epidemic season 2019-2020 (April 1, 2019 - March 29, 2020). Methods A total of 14 strains of influenza A (H1N1) pdm09 subtype virus was selected for sequencing. The phylogenetic trees were constructed by neighbor-jointing method, and the differences between the prevalent and vaccine strains in Hainan were compared by gene evolutionary trees. The sequencing results were analyzed by MEGA 10.1.8 and DNASTAR 7.0.1 software. Results During 2019-2020 influenza season influenza A (H1N1) pdm09 virus accounted for 4.9% of total influenza viruses detected in Hainan province. Phylogenetic analysis showed that M gene of influenza A (H1N1) pdm09 virus isolates in Hainan province from 2019 to 2020 could be divide into 6B.1 clade, be same with the international vaccine strain A/Brisbane/02/2018. The nucleotide and amino acid similarities were 98.7%-100.0%, 98.8%-100.0% respectively. And 12 isolates had mutations in amino acid S23N in the coding region of the extracellular region of the protein; all 14 isolates had mutations in the S31N site in the transmembrane region, and the mutation rate was 100.0%. There was 1 isolate with amino acid variation at the I39V locus and 9 isolates with amino acid variation at the E70D locus in the cytoplasmic region. Conclusions These data suggest that the activity of influenza A (H1N1) pdm09 virus was low level in Hainan province during 2019-2020 influenza season. The strains isolated in Hainan province have remained resistant to amantadine, and the circulating viruses were matched by current influenza vaccine. Special attention should be paid to the amino acid variation of M2 protein in future work to provide a scientific basis for the use of clinical anti-influenza virus drugs. [ABSTRACT FROM AUTHOR]