Influenza B virus monitoring and analysis of variation and evolution of hemagglutinin (HA) and neuraminidase (NA) genes in Jining city from 2017 to 2020 / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To analyze the variation and evolution characteristics of hemagglutinin (HA) and neuraminidase (NA) genes of influenza B virus circulating in Jining from 2017 to 2020.Methods:Throat swab specimens were collected from patients with influenza-like symptoms in sentinel hospitals and influenza outbreaks in Jining from 2017 to 2020 and tested for influenza B virus nucleic acid. After virus isolation, 20 representative strains of influenza B virus were selected to sequence the full length of HA and NA genes. Phylogenetic trees were constructed and the molecular characteristics were analyzed using bioinformatics software. Results:A total of 4 575 specimens were collected and 842 of them were positive for influenza virus, including 398 (8.7%, 398/4 575) influenza B virus-positive specimens. The positive rate of influenza B virus was 47.27% (398/842). The isolated influenza B virus strains of Victoria (BV) and Yamagata (BY) lineages from 2017 to 2020 shared 98.7%-98.8% and 98.5%-99.1% homology in HA gene with vaccine strains, respectively. The BV lineage strains isolated from 2018 to 2020 belonged to Victoria clade 1A branch and the BY lineage strains isolated from 2017 to 2018 belonged to Yamagata clade 3 branch. Mutations were detected in several antigenic sites, but not in the sites related to NA inhibitor resistance. Conclusions:Mutations in several antigenic sites caused antigenic changes in influenza B virus of BV and BY lineages, which might be related to the outbreaks of influenza B virus infection in Jining during 2017 to 2020.