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 8M 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.