Genetic characterization of influenza A(H3N2) viruses from 2014 to 2017 in Yantai, east of China

Abstract

Abstract Background: The genetic variations of influenza viruses pose a real challenge to the vaccine strategies and medical treatment of patients. Methods: In this study, the molecular epidemiology and evolution of influenza A(H3N2) strains were analyzed from April 2014 to March 2017 in Yantai area of eastern China. Results: The phylogenetic analysis of the hemagglutinin (HA) sequences of influenza A(H3N2) showed that all of the influenza A(H3N2) strains during the study period belonged to the genetic clade 3c with the mutations N145S (epitopeA), V186G (epitopeB), P198S (epitopeB) and F219S (epitopeD). Most strains (12/14) of the 2014/2015 season fell into the subgroup 3C.3a characterized by A138S (epitopeA), R142G (epitopeA), F159S (epitopeB) and T128A (epitopeB), while strains isolated from the 2015/2016 and 2016/2017 seasons clustered in 3C.2a shared mutations N144S (epitopeA), F159Y (epitopeB), K160T (epitopeB) and Q311H (epitopeC). The strains isolated from the 2014/2015 and 2015/2016 seasons was were genetically and antigenically distinct from the given vaccine strains. The evaluation of vaccine efficacy (VE) against circulating strains estimated using the pepitope model suggested that little or no protection against circulating strains from 2014/2015 and 2015/2016 seasons was afforded by the given vaccine strains. The sequence analysis of the neuraminidase (NA) showed that all of the analyzed strains had no substitution in the catalytic sites or the framework sites or the supporting the catalytic residues or the oseltamivir resistance substitutions. Conclusions: The results of the study suggested that the vaccine strains provided suboptimal protection against influenza A(H3N2) strains, especially in the 2014/2015 and 2015/2016 seasons and the A(H3N2) strains circulating in the Yantai area were still susceptible to NA inhibitors. Continued systematic antigenic and molecular surveillance of the influenza virus is essential to developing strategies for the prevention and control of influenza.