Sequence analysis of VPl and VP4 genes of enterovirus 71 strains isolated from children with hand-foot-mouth disease in Guiyang city,2013-2015

Objective To analyze the characteristics of the VP1 and VP4 genes of enterovirus 71(EV71)isolated from the children with hand-foot-mouth disease(HFMD)during 2013-2015 in Guiyang city of Guizhou province and to provide references for HFMD vaccine selection and clinical diagnosis and treatment of the disease.Methods Nasopharyngeal swab and/or faeces specimens were collected from 120 children seeking medication for mild HFMD at the Fifth People's Hospital of Guiyang City from April 2013 to August 2015 for the isolation of EV71.Then,the VPl and VP4 genes of the isolated EV71 strains were amplified and sequenced with reverse transcription-polymerase chain reaction(RT-PCR).The identified sequences were compared with those of A,B,C genotype references of EV71 strains from GenBank issued by National Center for Biotechnology Information of United States with phylogenetic tree analyses.In addition,nucleotide and amino acid alignments of VPl and VP4 genes of the EV71 strains isolated from randomly selected 20 cases were compared with those identified in other regions in China based on the results of phylogenetic tree analyses.Results All isolated EV71 strains belong to subgenogroup C4,clustered with those isolated from the HFMD cases in Beijing and Shanghai city and Anhui province in 2008 and in Shenzhen city in 2011.Compared with the strains isolated in other regions in China,the mutation of amino acid 293 (alanine to serine Ala→Ser) in the VP1 protein was observed for the strains from 12 of the 20 selected cases and that of amino acid 26 (alanine to threonine Ala→Thr),31 (asparagine to aspartic acid Asn→Asp),and 282 (Asn→Ser) in the VP1 protein were observed in one of the 20 selected cases,respectively;whereas only one mutation of amino acid 52(lysine to arginine Lys→Arg)in the VP4 protein was observed in one of the 20 selected cases.Conclusion The prevalent EV71 strains isolated in Guiyang city belong to subgenogroup C4 and common amino acid point mutations in VP1 for the isolated strains are 293(Ala→Ser),26(Ala→Thr),31(Asn→Asp),and 282(Asn→Ser)and a rare point mutation in VP4 is 52(Lys→Arg).