[Identification and sequence analysis of E gene of Dengue virus type 2 strain isolated from patient serum in Shenzhen]

Abstract

Objective: To isolate and identify the pathogen of Dengue fever from Shenzhen city in 2005 - 2006, and to analyze the molecular characteristics of the isolated Dengue virus strain as well as to explore its possible origin.

Methods: IgM and IgG of serum samples taken from 60 suspected Dengue fever patients were detected by ELISA and immunochromatography, and 9 specimens were positive. Nine samples from patients with early stage Dengue fever were used to isolate virus with C6/36 cell line and the positive cell cultures were identified by MGB fluorescent PCR. 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 Shenzhen Dengue virus with the strains isolated from other areas were constructed.

Results: Of nine antibody-positive serum samples, one strain of Dengue virus was successfully isolated. The isolated virus strain was confirmed as Dengue virus type 2 and designated as DEN2-SZ0521. The homology of nucleotide sequence and the deduced amino acid sequence of E gene of SZ0521 with standard type 2 Dengue virus NGC strain was 94.2% and 98.2%, but the homology with standard Dengue virus 1, 3, 4 in the same fragment were 59.1%, 57.2%, 58.5% and 68.1%, 66.7%, 63.2%, respectively. The phylogenetic tree indicated that SZ0521 had the greatest similarity with the Malay0412a/Tw strain and they lied in the same branch of the phylogenetic tree. The corresponding homology of nucleotide sequence and amino acid sequence was 99.8% and 100%, respectively. The isolated Dengue virus type 2 belonged to genotype IV with Indonesia-76, Somalia-84 and Sri Lanka-90.

Conclusion: Dengue virus was isolated from Shenzhen for the first time, and it was classified as type 2. It was confirmed that the type 2 Dengue virus may come from the epidemic area in Malaysia.