Genomic analysis of avian influenza A(H7N9) virus in Suzhou, Anhui, 2017

Abstract

Objective To illustrate molecular evolution and biological characteristics of avian influenza A (H7N9) virus isolated in Suzhou, Anhui in 2017. Methods The 4 strains of influenza A (H7N9) were isolated from throat swab samples and the viral genomes were sequenced. Phylogentic tree was constructed and mutations at important amino acid sites were analyzed. Results The HA genes of the four strains had the highest similarity (99%) with A/Henan/15337/2017 (H7N9) and NA genes had a similarity of 99%-100% with A/Changsha/44/2017 (H7N9). The internal genes showed high similarity (94%-100%) to avian influenza A (H9N2) virus strains from Zhejiang, Hunan, Jiangxi and Guangdong provinces between 2013 to 2017. Phylogenetic analysis indicated that HA genes of the four strains belonged to the Yangtze River Delta branch. Neither G186V and Q226L mutations in HA receptor site nor the mutations related to resistance of neuraminidase inhibitant in NA protein was found. The mutations, including E627V mutation in PB2 protein, N30D and T215A mutations in M1 protein, P42S and PDZ motif deletion in NS1 protein, and S31N mutation in M2 protein were found. Conclusions The 4 strains of human avian influenza A (H7N9) virus were all in the Yangtze River Delta branch. Resistance to M2 ion channel inhibitant occurred. Therefore, more attention should be paid on the genetic evolution of the virus for the effective prevention and treatment of H7N9 avian influenza in Suzhou, Anhui province. Key words: Avian Influenza; Genome; Sequence similarity; avian influenza A (H7N9) virus; amino acid site