Abstract：To understand the relationship between variation of enterovirus 71 ( EV 71) and its virulence, the sequence of the VP4 gene of EV71 virus was analyzed. Eight strains of EV71 isolated from clinical samples collected from infants and children with hand, foot and mouth disease in the Children’s Hospital Affiliated to Capital Institute of Pediatrics in Beijing during 2007 to 2008 were used for comparison. Full length VP4 genes from these eight EV71 strains were amplified by reverse-transcriptase PCR ( RT-PCR) and sequenced after the amplicons were cloned into pUCm-T. The sequences were compared with VP4 genes from EV71 in GenBank. Sequence analysis and type identification were performed by bioinformatics ( DNAStar) . The full length of VP4 gene has 207 bp coding for a protein of 69 amino acids with estimated molecular weight of 7 ×103 . The nucleotide homology of VP4 genes among the eight strains were 94% ～100% and homology of the deduced amino acids were 100% . The nucleotide sequence homology between these eight strains isolated in Beijing and those isolated in Fuyang, Shenzhen and Taiwan was higher than those isolated elsewhere. The homology of deduced amino acid sequences encoded by VP4 between these eight isolates in Beijing and those in GenBank was 100% except one strain isolated from India. The amino acids at the 7th and 54th position of VP4 of the strain from India were different from others. There were many differences between the nucleotide sequences of VP4 from the eight Beijing strains and those from severe cases ( BrCr, MS and NCKU9822) , as reported in the literature, whereas only a few nucleotide differences were observed between severe
cases ( BJ97, BJ110B, BJ110Y and BJ4243) and mild cases ( BJ25, BJ47, BJ65 and BJ67) among these eight Beijing strains. Phylogenetic analysis of the VP4 sequences from these eight strains indicates that the EV71 viruses that circulated in Beijing during 2007 to 2008 should be classified as subtype C4. The VP4 genes from the isolates in Beijing from2007 and 2008 were highly conserved. There was no consistent divergence in the sequences of VP4 between strains isolated fromsevere cases and those frommild cases, suggesting that the virulence of the EV71 virus does not seem to be related to the sequence of VP4.
2009, Vol. 4 
