High-level expression of recombinant dengue virus type 2 envelope domain III protein and induction of neutralizing antibodies in BALB/C mice

Dengue fever is a growing public health problem in many countries since so far no effective vaccines are available. In this study, the domain III of dengue virus type 2 envelope was expressed in Escherichia coli without fusion of any carrier protein. The recombinant protein was detected in the form of inclusion bodies, which were solubilized in 8 M urea and could be purified subsequently by high-performance liquid chromatography (HPLC) on an ion exchange column. After refolding, the recombinant protein inhibited the DEN-2 plaque formation on C6/36 cells, demonstrated its function of receptor-interaction was retained. The recombinant protein was inoculated into BALB/c mice to test its immunogenicity and ability to induce neutralizing antibodies. The mice immunized with the purified protein developed high antibody titers. A neutralizing titer of 1:64 was also obtained by a cytopathogenic effect (CPE) inhibition assay in C6/36 cells. Mice challenged with lethal dose of DEN-2 in combination with sera from immunized mice were protected completely. The results suggested that these expression and purification strategies have the potential for development of an inexpensive vaccine.