Dengue virus type-3 envelope protein domain III; expression and immunogenicity

OBJECTIVES Production of a recombinant and immunogenic antigen using dengue virus type-3 envelope protein is a key point in dengue vaccine development and diagnostic researches. The goals of this study were providing a recombinant protein from dengue virus type-3 envelope protein and evaluation of its immunogenicity in mice. MATERIALS AND METHODS Multiple amino acid sequences of different isolates of dengue virus type-3, corresponding to the envelope protein domain III, were achieved from GenBank. Clustal V alignment tool was used to provide a consensus amino acid sequence. Nucleotide sequence of the coding gene was optimized using "Optimizer". The origami (DE3) strain of Escherichia coli was used as the host in order to express the protein. A commercial affinity chromatography method was used to purify the recombinant protein. Immunogenicity of the recombinant protein was evaluated in mice using ELISA, MTT and cytokine assays. RESULTS A consensus amino acid sequence corresponding to the most important region of dengue virus type-3 envelope protein (domain III) was provided. A high concentration (≥ 20 mg/L culture medium) of soluble recombinant antigen (EDIII3) was achieved. Immunized mice developed specific antibody responses against EDIII3 protein. The splenocytes from EDIII3-immunized mice showed a high proliferation rate in comparison with the negative control. In addition, the concentrations of two measured cytokines (IFN-γ and IL-4) were increased markedly in immunized mice. CONCLUSION The results showed that the expressed recombinant EDIII3 protein is an immunogenic antigen and can be applied to induce specific immune responses against dengue virus type-3.