DNA vaccines expressing either the GP or NP genes of Ebola virus protect mice from lethal challenge

DNA vaccines expressing the envelope glycoprotein (GP) or nucleocapsid protein (NP) genes of Ebola virus were evaluated in adult, immunocompetent mice. The vaccines were delivered into the skin by particle bombardment of DNA-coated gold beads with the Powderject-XR gene gun. Both vaccines elicited antibody responses as measured by ELISA and elicited cytotoxic T cell responses as measured by chromium release assays. From one to four vaccinations with 0.5 microgram of the GP DNA vaccine resulted in a dose-dependent protection from Ebola virus challenge. Maximal protection (78% survival) was achieved after four vaccinations. Mice were completely protected with a priming dose of 0.5 microgram of GP DNA followed by three or four subsequent vaccinations with 1.5 micrograms of DNA. Partial protection could be observed for at least 9 months after three immunizations with 0.5 microgram of the GP DNA vaccine. Comparing the GP and NP vaccines indicated that approximately the same level of protection could be achieved with either vaccine.