Preliminary evaluation of DNA vaccine candidates encoding dengue-2 prM/E and NS1: their immunity and protective efficacy in mice.

Public health is still seriously threatened by dengue virus (DENV) and no vaccine against DENV is yet available for clinical use till now. In this study, DNA vaccine candidates encoding DENV serotype 2 (DENV-2) prM/E (premembrane and envelope proteins) and NS1 (non-structural 1 protein) with or without a gene adjuvant, granulocyte-macrophage colony-stimulating factor (GM-CSF), were evaluated in the aspects of immunity and protective efficacy in mice. We constructed three plasmids, pCAG-prM/E (which only expressed DENV2 prM/E), pCAG-prM/E/NS1 (which only expressed DENV2 prM/E/NS1) and pCAG-DG (which co-expressed DENV2 prM/E/NS1 and GM-CSF). The expressions of the recombined plasmids were analyzed by immuno-staining in Vero cells. Antibody responses and neutralization activity of the sera from the mice were assayed by ELISA and plaque reduction neutralization test after immunization with the plasmids. Immunized BALB/c mice were intracerebrally challenged with DENV2 to evaluate protective efficacy of the plasmids. The recombinant plasmids could be efficiently expressed in Vero cells and induced different levels of specific anti-DENV2 immune responses. The immunized mice were partially protected. The highest survival rate was observed in the pCAG-DG group although the anti-DENV2 titer and neutralization antibody titer were not the highest among the three groups. Our data suggested that pCAG-DG offered better protection against DENV2 infection.