The etiology detection and analysis for the first local case of dengue virus type 3 infection in Shenzhen

Abstract

Objective To determine the etiology of the first local dengue fever case reported in Shenzhen city in 2016, and to isolate, to identify as well as to study the molecular characteristics of the isolated dengue virus strain. Methods The serum sample collected from the suspect dengue fever case was detected for IgM, IgG by ELISA, and NS1 antigen by immunochromatography and dengue virus nucleic acid by real-time RT-PCR. The samples were further inoculated in C6/36 cells for virus isolation. PrM/M-E gene of isolated virus strain was amplified by RT-PCR and sequenced to construct homology comparison and phylogenetic tree of PrM/M-E gene of Shenzhen dengue virus with the strains isolated from other areas. Results IgM, NS1 antigen and RNA of dengue virus type 3 were detected in the serum sample. Type 3 dengue virus named DENV3-SZ1648 was successfully isolated from the serum sample. The homology of nucleotide sequence of PrM/M-E gene of SZ1648 with standard type 3 dengue virus H87 strain, 80-2 strain, GWL-25 strain were 92.0%, 91.8% and 90.3%, respectively. The homology with standard dengue virus 1, 2, 4 in the same fragment were 68.7%, 64.2% and 63.2%, respectively. The phylogenetic tree indicated that SZ1648 had the greatest similarity with the MKS-0098 strain (Indonedia 2007) and they lied in the same branch. The isolated dengue virus type 3 belonged to genotype I as the 85-159 strain (Indonedia 1985), 2167 strain (Tahiti 1989) and 29472 strain (Fiji 1992). The patient lived in Shenzhen and had no history of travelling outside the area in one month before infection. Conclusions The virological, serological and molecular features showed that the local case of dengue fever was caused by dengue virus type 3 and was most likely imported from Indonesia. This is also the first report of the local dengue virus type 3 infection case in Shenzhen. Key words: Local case; Dengue virus type 3; PrM/M-E gene; Sequence analysis