Genetic evolution of influenza B virus in Guizhou Province during 2017 to 2021 / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To analyze the molecular evolution characteristics of HA and NA genes of influenza B/Yamagata (BY) and influenza B/Victoria (BV) lineage viruses in Guizhou Province, aiming to provide reference for scientific prevention and control of influenza. Methods:The prevalence of various types of influenza viruses in Guizhou Province from 2017 to 2021 was analyzed. The nucleic acid of influenza B viruses was extracted, and then the HA and NA genes were amplified by RT-PCR. Fourteen strains were sequenced and the sequences of 83 strains were obtained from GISAID. Homologies between the 97 influenza B viruses as well as the phylogenetic characteristics and amino acid site variations were analyzed. Results:Influenza A, BY and BV lineage viruses co-circulated in Guizhou Province and BV lineage was the predominant type. The homologies of HA and NA genes were 98.7%-99.4% and 98.4%-99.6% between BY lineage viruses and the reference vaccine strain B/PHUKET/3073/2013. BV lineage viruses shared 98.3%-99.3% and 98.9%-99.6% homologies with the reference vaccine strain B/Colorado/06/2017. The BY lineage strains in Guizhou Province mainly belonged to Y3 genetic group with HA gene in two branches of Y3-H1-2 and NA gene in three branches of Y3-N1-3. Three reassortant strains were found in Y3 clade. The isolated BV lineage strains mainly belonged to V1A-2 genetic group with HA gene in four branches of V1A-2 H1-4 and NA gene in five branches of V1A-2 N1-5. Twenty reassortant strains were found in V1A-2 clade and no inter-lineage reassortants were found. Analysis of variations at key amino acid sites showed that there was no mutation at epitopes in Y3 genetic group. However, there were point mutations at four main epitopes and a shift mutation in 190 helix in V1A-2 genetic group. There was no mutation in drug resistance sites. Conclusions:Various types of influenza viruses circulated in Guizhou Province. The homology between influenza B viruses and vaccine strains was decreasing. Different branches of HA and NA genes had been evolved and various forms of mutations were detected in the sequences. Intra-lineage reassortant strains and new varieties emerged. Surveillance of influenza B viruses should be strengthened.