Recombinant plasmid expressing a truncated dengue-2 virus E protein without co-expression of prM protein induces partial protection in mice

A nucleic acid vaccine candidate against dengue-2 virus was constructed to express a truncated dengue-2 E glycoprotein without concomitant expression of prM. The truncated E protein was properly expressed even in the absence of prM. Mice inoculated intramuscularly with the recombinant plasmid containing 94% of the E gene did not respond with anti-dengue antibodies, cellular proliferation, or synthesis of cytokines by their lymphoid cells when stimulated with purified dengue-2 virus. However, protection was observed in 20% of the challenged mice immunized with this recombinant plasmid and the mice survived longer than the control group. The low percentage of protection might be explained by a weak activation of the immune system resulting from an imperfect secretion of E due to lack of the prM protein. This study corroborates with the hypothesis that prM is important for the processing of the E glycoprotein and should be incorporated on candidate vaccines engineered by recombinant DNA technology.