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.
ABSTRACT
We investigated the molecular characteristics of the full-length genome of 14 dengue serotype 1 virus (DENV-1)strains isolated in Sino-Myanmar border region in Yunnan Province,China during 2013-2015.Isolation of dengue virus was using C6/36 cell culture method.Viral RNA was extracted from virus isolates,and 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 bioinformatics software including ClastalX1.83 and MEGA6 etc.Results showed that fourteen strains of DENV-1 isolated from dengue fever cases,of these,9 strains from Ruili City of Dehong Prefecture,3 from Lincang Prefecture,2 from Kunming City.RT-PCR and sequencing indicated that the full-length genes (10 735 nt) of 14 DENV-1 strains were obtained,and their open reading frame (95-10 271) were coded 3 392 amino acid residues.The genotypes of DENV-1 were revealed by homology and phylogenetic analysis based on structural and non-structural proteins.Thirteen were genotype Ⅰ (G-Ⅰ) (7 from indigenous cases in Ruili and Lincang and 6 from imported case from Myanmar to Ruili,Lincang and Kunming),and 1 G-Ⅲ from imported case from India to Kunming.The phylogenic analysis indicated that the 13 isolates from Yunnan divided into 2 phylogenic subgroups,and they had a closer genetic relationship with the strains isolated from Southeast Asia.The gene sequences of the 13 G-Ⅰ strains have been acquired,the rate of their nucleotide homology and amino acid homology were 97.02 ％-100 ％ and 98.78 ％100 ％ respectively.Compared with 6 strains from Southeast Asia,nucleotide homology and amino acid homology were 96.53％-99.53％ and 97.33％-100％ respectively.Compared with prototype strain (US_Hawaii) of DENV-1,nucleotide homology and amino acid homology were 93.76％-94.45 ％ and 95.86 ％-96.91％ respectively.Compared with US_Hawaii strain,there were 44 and 150 different sites in amino acid of structural and non-structural proteins,respectively.The G-1 of DENV-1 have been popular in Sino-Myanmar border region in Yunnan,2013-2015.They have genetic diversity but multiple transmission sources were from Myanmar,and should strengthen control cross-border spread of dengue fever in this region.It is necessary to further study that change of the amino acid sites of Yunnan strains of DENV-1 is related to its antigenicity and pathogenicity.