Sequence analysis of VP1-VP4 genes of enterovirus 71 strains isolated from children with severe or mild hand, foot and mouth disease in Shenzhen, China in 2012

Abstract

Objective To analyze the VP1-VP4 genetic region of enterovirus 71 (EV71) strains isolated from children with severe or mild hand, foot and mouth disease (HFMD) in Shenzhen in 2012. Methods EV71 strains were isolated from five children with mild HFMD and five children with severe HFMD in Shenzhen in 2012. Reverse transcription-polymerase chain reaction (RT-PCR) method was used to amplify the sequence of VP1-VP4 genes of EV71 strains. The sequences of the amplified products were analyzed by comparing with those of the EV71 reference strains (A, B and C genotypes) published in GenBank using nucleotide alignment, amino acid alignment and phylogenetic tree analysis. Results The homogeneity between the EV71 strains isolated from severe and mild cases was 95.1%-98.2% in nucleotides and 99.2%-100% in amino acids. The VP1-VP4 nucleotide sequences of 5 strains isolated from severe cases and 5 strains from mild cases in Shenzhen shared 87.9%-97.8% homologies in nucleotides and 97.3%-99.9% homologies in amino acids with the genotype C EV71 reference strain. The EV71 strains isolated from children in Shenzhen were highly similar with the EV71 strain (FJ439769) isolated in Fuyang in 2008 and the one isolated in Jingdezhen in 2011 (JQ806378, C4a subtype) in nucleotide sequences. Mutations at the residue 31 in the VP1 region (N→D) were detected in 3 strains isolated from children with severe HFMD. Conclusion All of the 10 EV71 strains isolated in Shenzhen in 2012 belonged to the sub-genotype C4a. The mutation (aa31 N→D) in the VP1 region of EV71 might be related to the different clinical manifestations of HFMD cases in Shenzhen area. Key words: Hand, foot and mouth disease; Enterovirus 71; Sequence analysis; Genotype; Mutation