Sequence analysis of VP1 and VP4 genes of enterovirus 71 strains isolated from children with severe and mild hand-foot and mouth disease

Objective To analyze and compare VP1 and VP4 genetic characteristics of human enterovirus 71(EV71) isolated from children with severe and mild hand-foot and mouth disease(HFMD). Methods EV71 strains isolated from severe HFMD patients (6 cases) and mild HFMD patients (6 cases) in Taizhou district, Zhejiang province were included during 2016.Total virus RNA was extracted by Viral RNA Mini Extraction Kit, and reverse transcription polymerase chain reaction(RT-PCR) was used to amplify the sequence of the VP1 and VP4 genes of EV71.And then the sequencing results were compared with those of A, B, C genotype reference EV71 strains from GenBank by nucleotide alignment and amino acid alignment analysis. Results There were no statistically significant differences in sex and age between the two groups(χ2=14.51, t=2.82, all P<0.05). The homogeneity between EV71 strains from severe patients and mild patients was 95.8%~99.6% and 99.1%~100.0% for VP1 nucleotide sequences and amino acid sequences, respectively, while 95.0%~99.9% and 99.0%~100.0% for VP4 nucleotide sequences and amino acid sequences, respectively.The twelve EV71 strains isolated from HFMD patients in Taizhou shared the highest identity with EV71-genotype C, especially genotype C4a.In addition, compared with the mild patients, three respective strains from severe HFMD patients showed mutations at the residue 170 in the VP1 protein(V→L), residue 293 in the VP1 protein(A→S) and residue 7 in the VP4 protein(T→A). Conclusion All EV71 strains isolated from severe and mild HFMD patients in Taizhou district share high homology of nucleotide and amino sequence, and all of them belong to subgenogroup C4a.The mutations in the VP1 and VP4 of EV71 might be related to HFMD disease severity. Key words: Hand-foot and mouth disease; Enterovirus 71; Genotype; Disease severity; Mutation