Genomic characteristics of mumps virus genotype G in Dalian

Abstract:

Objective Mumps virus (MuV) is the causative agent of mumps. Nowadays, genotype F is widely prevalent in China, while genotype G appears in localized areas and is exhibiting a trend of gradual expansion. To understand the genetic characteristics of genotype G strains in China, we selected two genotype G MuV strains that were isolated from Dalian, Liaoning for analysis.Methods The whole genomes of the two strains were sequenced, and the genotypes were determined according to the WHO reference strains. Furthermore, we compared the molecular characteristics among different genotypes and within genotype G. By comparison with the sequences of genotype G strains in other areas of China, we analyzed the features of genotype G MuVs in China, as well as the genetic distance and variations of key antigenic sites between the wild-type genotype G strains and the existing vaccine strains.Results The strains isolated in this study both belonged to genotype G, and they showed the nucleotide differences ranging from 4.2% to 6.9% from other 12 genotypes, with the greatest divergence from genotype A. Among the protein coding genes, the SH coding gene exhibited the largest variation, while the NP, M, and L coding genes were conserved. The P, F and HN coding genes demonstrated significant differences among different genotypes. The genotype G strains isolated in this study were closely related to the strain isolated in Jiangsu Province (Jiangsu.CHN/22.13/2), while they were distinct from the strains previously isolated in Liaoning Province. The genotype G strains isolated in this study lacked a N-glycosylation site (aa 12-14) but gained a N-glycosylation site (aa 464-466) in the key epitope of HN protein. In addition, the genotype G strains showed considerable differences in terms of neutralizing epitopes from the genotype A vaccine strain. These differences suggested that the mutations of these sites may potentially reduce the cross-protection effects of vaccine strains against wild-type MuV strains. Although there were some mutations in F protein, the functional region was conserved.Conclusion This study details the genotypic characteristics of genotype G MuVs in Dalian, highlighting their high similarities to the genotype G strains in China and the WHO reference strains, while underscoring significant differences from the genotype A vaccine strain used worldwide. These findings suggest the necessity of continuous surveillance of MuV strains in China and further studies of their epidemiology and virology, which could provide references for tracing MuVs, cutting the transmission route, and developing immunization strategies in China.

Key words:mumps virus;genotype G;whole genome;genetic characteristic