Genetic Characterization Of Echovirus Type 7&11 In Tibet

Human enteroviruses(HEV) are noneveloped single-stranded positive-sense RNA viruses belonging to the Enterovirus genus of the Picornaviridae family. They are major human pathogens ang are associated with a broad spectrum of clinical features including acute respiratory illness,aseptic meningitis, meningoencephalitis,myocarditis,hand,foot andmouth disease,neonatal multiorgan failure and acute flaccid paralysis.Based on their antigenic properties,the originol HEV serotype were initially grouped into polioviruses(PV),coxsachieviruses A(CA),coxsachieviruses B(CB), echoviruses(E),and the more recently identified enteroviruses(EV) 68 to 71.A new HEV classification based on molecular and biological data has recently been proposed as an altermative to the antigenic classification.This classification groups enteroviruses into five species:PV,HEV-A,HEV-B, HEV-C,HEV-D.Outbreaks of disease associated with enteroviruses are often reported and represent a major public health problem.Tibet is in a particular geographic environment.It is valuable to study the genetic characterization of enteroviruses in Tibet. Methods To isolate the enteroviruses from stool specimens of AFP cases and other children in Tibet in 1999-2002,and identify them by neutralization test using the RIVM antiserum;then determine the complete nucleotide sequence of VP1 region of ECHO7&11 viruses,and analyse the results.Results A total of 16 strains of ECHO7 virus and 15 strains of ECHO 11 were isolated from the stool specimens and identified.The complete nucleotide sequence of VP1 region of these ECHO7&11 viruses was 876nt coding 292 amino acids.To compare with the sequences of Wallace strain,the homogeneity of nucleotide sequence of Tibet-ECHO7 were 77.85-78.99%;that were 81.67-83.79%compare with UMMC strain.The phylogenetic tree of ECHO7 viruses showed 4 genotypes,and the ECHO7 isolates from Tibet formed 1 independent genotype.The phylogenetic tree of ECH11 viruses also showed 4 genogroup,and the ECHO11 isolates from Tibet belong to 2 independent genogroups:Genogroup A and C.Conclusion The deduction is that the 16 ECH07 virus strains isolated from China Tibet are proposed one new genotype of ECHO7 virus.There are 4 genogroups among all the ECHO11 viruses.The ECHO11 strains isolated from China Tibet belong to 2 independent genogroups:Genogroup A and C.