Sequence analysis of enterovirus 71 strains isolated from patients with different clinical symptoms in Ningbo city

Objective To determine the neurovirulence-related sites of enterovirus 71 (EV71) isolated in Ningbo area in 2010.Methods Fluorescent PCR was used to detect the excrements of patients with different clinical symptoms.EV71 was isolated and checked from the positive species,and the genome determined with reverse transcription-PCR (RT-PCR) was cloned,spliced,and sequenced with eight superimposed fragments.The homology was analyzed and the amino acid sequences were deduced and analyzed with DNAstar.Results All of the sequences of six strains were 7 406 bp in length and the homology of nucleotide were 97.9%-99.4%.The nucleotide sequence of the three severe cases at the position of 124th,272th and 408th were T,G,and A,respectively,distinguishing from the other three of A,A,and G.According to the deduced amino acid sequences,the three severe cases in the position of 715th,1704th and 1706th were met,arg and ile,respectively,distinguishing from the other three of leu,lys,and val.Conclusion The variations in IRES,VP1,and 3C may be associated with the neurovirulence of EV71 isolated from patients in Ningbo area in 2010.