Molecular characterization of coxsackievirus A16 B1 in Anhui, 2018−2019

  Objective  To understand the characteristics of molecular etiology of coxsackievirus A16 (CV-A16) causing hand foot and mouth disease (HFMD) in Anhui province from 2018 to 2019.

  Methods  CV-A16 strains were isolated from throat swabs of HFMD cases in Anhui during 2018−2019. The full-length gene of VP1 of CV-A16 strains was amplified by RT-PCR and sequenced. The genotype/sub-genotype of CV-A16 strains was identified by enterovirus online typing tool (https://www.rivm.nl/mpf/typingtool/enterovirus/), and the phylogenetic tree of VP1 gene was constructed by maximum likelihood method with biological software MEGA 6.0 Software Megalign was used to compare the homology of nucleotide and amino acid.

  Results  A total of 88 CV-A16 strains were isolated from HFMD cases in Anhui from 2018 to 2019. Among the strains, 30 were isolated in 2018 and 58 were isolated in 2019. The full-length gene of VP1 regions of the strains were all composed of 891 nucleoside acid, encoding 297 amino acids. Genotyping identification and phylogenetic analysis showed that among the 88 CV-A16 strains, B1a and B1b sub-genotypes were detected in 25 and 63 strains, accounting for 28.41% (25/88) and 71.59% (63/88) respectively. The genetic evolution of VP1 region showed that 88 CV-A16 strains were classified as B1 genotype, in which 25 belonged to sub-genotype B1a and 63 belonged to sub-genotype B1b. Homology analysis showed that the nucleotide homology between B1a strain and CV-A16 prototype strain G-10 was 64.1%–65.3%, and the amino acid homology was 90.3%–91.1%; The homology of nucleotide and amino acid between B1b strain and prototype strain was 62.8%–66.0% and 91.1%–91.8%, respectively. The amino acid sequences of VP1 regions of 88 strains CV-A16 were compared with that of the prototype strain, and mutation occurred in 26 amino acid loci.

  Conclusion  B1b and B1a were the common sub-genotypes of CV-A16 causing HFMD in Anhui from 2018 to 2019, and B1b was predominant. It is necessary to pay attention to the surveillance for molecular etiology of CV-A16 epidemic strains.