RESUMO
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.
RESUMO
Objective@#To understand the serotypes, genotypes and transmission source of dengue viruses(DENV) isolated in Yunnan from 2013 to 2015.@*Methods@#Viral RNA was extracted from serum samples of dengue fever(DF) cases at the acute stage in Yunnan, then the gene fragments of envelope protein(E) region were amplified by RT-PCR. The homology and phylogenetic analysis was made on the nucleotide and deduced amino acid sequences by bioinformatics softwares including Clustal X, DNAStar and MEGA5.@*Results@#Viral nucleic acid detection and sequencing indicated that 40 E genes of DENV were obtained. The serotypes and genotypes of DENV were revealed by homology and phylogenetic analysis based on E genes of DENV. Fifteen virus strains belonged to DENV serotype 1(DENV-1), of these, 14(11 from Ruili, 1 from Lincang and 2 from Kunming) were genotype I(G-I), 1 from Kunming was G-V. Twenty-two virus strains belonged to DENV serotype 2(DENV-2), of these, 10 from Ruili were G-I and 12 from Xishuangbanna were G-IV. Two virus strains belonged to DENV serotype 3(DENV-3) and G-II. One virus strain belonged to DENV serotype 4(DENV-4) and G-I. All detected DENV genotypes were mainly predominant in Southeast Asia. All the 40 Yunnan DENV strains shared high homology with the DENV strains in Southeast Asia countries.@*Conclusions@#Four serotypes and multiple genotypes of DENV had been co-circulating in Yunnan from 2013 to 2015. The DENV transmitted from Southeast Asia countries was the main cause of DF in Yunnan. It is necessary to strengthen the surveillance and management on the imported cases of DF in Yunnan.
RESUMO
<p><b>OBJECTIVE</b>To understand the molecular characteristics of a dengue virus outbreak in China-Myanmar border region, Yunnan province, 2015 and provide etiological evidence for the disease control and prevention.</p><p><b>METHODS</b>Semi-nested RTPCR was conducted to detect the capsid premembrane (CprM) gene of RNA of dengue virus by using dengue virus NS1 positive serum samples collected in Mengdin township, Gengma county, Yunnan province in July, 2015. Some positive samples were then detected by using PCR with specific primers to amplify the full E gene. The positive PCR products were directly sequenced. Then sequences generated in this study were BLAST in NCBI website and aligned in Megalign in DNAstar program. Multiple sequence alignments were carried out by using Mega 5.05 software based on the sequences generated in this study and sequences downloaded from GenBank, including the representative strains from different countries and regions. Phylogenetic trees were constructed by using Neighbor-Joining tree methods with Mega 5.05 software.</p><p><b>RESULTS</b>Twenty one of 25 local cases and 10 of 14 imported cases from Myanmar were positive for DENV-1. Eight serum samples were negative for dengue virus. A total of 13 strains with E gene (1485 bp), including 8 local strains and 5 imported strains, were sequenced, which shared 100% nucleotide sequence identities. Twelve strains with CprM gene (406 bp) from 9 local cases and 3 imported cases shared 100% nucleotide sequence identities. Phylogenetic analyses based on E gene showed that the new 13 strains clustered in genotype I of dengue virus and formed a distinct lineage.</p><p><b>CONCLUSIONS</b>This outbreak was caused by genotype I of DENV-1, which had the closest phylogenetic relationships with dengue virus from neighboring Burma area. Comprehensive measures of prevention and control of dengue fever should be strengthened to prevent the spread of dengue virus.</p>