Sequence determination and phylogenetic tree analysis of the E gene of dengue virus type 4 isolated from a patient in Shenzhen / 中国人兽共患病学报

ABSTRACT

To identify the genotype and analyze the molecular characteristics of dengue virus strain SZ0524 isolated from serum samples of patients with early stage of dengue fever in Shenzhen in 2005 so as to explore its possible origin. The C6/36 cell line was cultivated with virus strain SZ0524 and its suspension was harvested. The type of isolated virus strain was determined by RT-semi-nested PCR and fluorescent PCR. E gene of isolated virus strain was amplified by RT-PCR and sequenced. Homology and phylogenetic tree of E gene of this dengue virus with the strains isolated from other areas were constructed. This SZ0524 strain was further identified by fluorescent PCR, and confirmed to be the type 4 virus after obtaining the 392bp band with type 4 specific primers. The homology of nucleotide sequence of E gene of SZ0524 strain with the standard type 4 dengue virus H241 strain were 99.7%, but the homology with the standard dengue virus 1,2,3 in the same fragment were 57.0%, 59.2% and 56.2% respectively. Analysis of the phylogenetic tree indicated that SZ0524 was more close to D4-73NIID and D4-61NIID strain, next to H241 strain, and they lied in the same branch of phylogenetic tree. The isolated dengue virus type 4 belonged to genotype Ⅰand the SZ0524 strain was proved to be dengue virus type 4 in the molecular level. Combined with epidemiology information, it is suggested that this case can be classified as an imported case and the SZ0524 strain may be transferred from the southeast asian region.