Molecular characteristics of the full-length genome of dengue serotype 4 virus strains isolated from dengue fever cases in Yunnan Province, China / 中国人兽共患病学报

ABSTRACT

We investigated the molecular characteristics of the full-length genome of 5 dengue serotype 4 virus (DENV-4) strains isolated in Yunnan Province,China,2015 and their molecular epidemiological feature.Isolation of dengue virus was using C6/36 cell culture method.Viral RNA was extracted from virus isolates,then the full-length genome was amplified by RT-PCR.The homology and phylogenetic analysis was made on the nucleotide and deduced amino acid sequences by bioinfor matics softwares including ClastalX1.83 and MEGA6 etc.Results showed that five strains of DENV-4 isolated from dengue fe ver cases in Ruili City of Yunnan Province in 2015,of these,2 strains from indigenous cases,3 from imported cases from Lashio and Nam Can cities of Myanmar to Ruili of China.RT-PCR and sequencing indicated that the full-length genes (10 661 nt) of 5 DENV-4 strains were obtained,and their open reading frame (103-10 264) were coded 3 386 amino acid residues.Phylogenetic tree and homology analysis based on the comeplete genome or structural and non-structural protein genes showed that the 5 DENV 4 isolates were highly homologous and gathered in an evolution as well as they have a closer genetic relationship with the DENV-4 genotype Ⅰ (G-Ⅰ) strains isolated from Thailand.Results indicated that the Yunnan strains belonged to G-Ⅰ.Yunnan strains and Thailand strains compared with DENV 4 prototype strain (H241,Philippines 1956) and Guangzhou strain (B5,1990) of China and showed low homology and evolutionary relationship.When Yunnan strains compared with H241 strain,there were 21 and 45 different sites in amino acid of structural and non-structural proteins,respectively.This is the first time in Yunnan to obtain full-length genomes sequence of DENV-4 and they have closer evolutionary relationship with DENV 4G-Ⅰ strains from Southeast Asia region in recent years.The autochthonous DENV-4 epidemic in Yunnan was detected for the first time,and the virus transmission sources were from neighboring northern Myanmar.It is necessary to further study that change of the amino acid sites of Yunnan strains of DENV-4 is related to its antigenicity and virulence.