Nanoplasmid Vectors Co-expressing Innate Immune Agonists Enhance DNA Vaccines for Venezuelan Equine Encephalitis Virus and Ebola Virus

John J Suschak; Lesley C Dupuy; Charles J Shoemaker; Carolyn Six; Steven A Kwilas; Kristin W Spik; James A Williams; Connie S Schmaljohn

doi:10.1016/j.omtm.2020.04.009

Nanoplasmid Vectors Co-expressing Innate Immune Agonists Enhance DNA Vaccines for Venezuelan Equine Encephalitis Virus and Ebola Virus

Mol Ther Methods Clin Dev. 2020 Apr 15:17:810-821. doi: 10.1016/j.omtm.2020.04.009. eCollection 2020 Jun 12.

Authors

John J Suschak¹, Lesley C Dupuy¹, Charles J Shoemaker², Carolyn Six¹, Steven A Kwilas¹, Kristin W Spik¹, James A Williams³, Connie S Schmaljohn⁴

Affiliations

¹ Virology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD 21702, USA.
² Diagnostic Systems Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD 21702, USA.
³ Nature Technology Corporation, Lincoln, NE 68521, USA.
⁴ Headquarters, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD 21702, USA.

Abstract

DNA vaccines expressing codon-optimized Venezuelan equine encephalitis virus (VEEV) and Ebola virus (EBOV) glycoprotein genes provide protective immunity to mice and nonhuman primates when delivered by intramuscular (IM) electroporation (EP). To achieve equivalent protective efficacy in the absence of EP, we evaluated VEEV and EBOV DNA vaccines constructed using minimalized Nanoplasmid expression vectors that are smaller than conventional plasmids used for DNA vaccination. These vectors may also be designed to co-express type I interferon inducing innate immune agonist genes that have an adjuvant effect. Nanoplasmid vaccinated mice had increased antibody responses as compared to those receiving our conventional pWRG7077-based vaccines when delivered by IM injection, and these responses were further enhanced by the inclusion of the innate immune agonist genes. The Nanoplasmid VEEV DNA vaccines also significantly increased protection against aerosol VEEV challenge as compared to the pWRG7077 VEEV DNA vaccine. Although all mice receiving the pWRG7077 and Nanoplasmid EBOV DNA vaccines at the dose tested survived EBOV challenge, only mice receiving the Nanoplasmid EBOV DNA vaccine that co-expresses the innate immune agonist genes failed to lose weight after challenge. Our results suggest that Nanoplasmid vectors can improve the immunogenicity and protective efficacy of alphavirus and filovirus DNA vaccines.

Keywords: CpG; DNA Vaccine; Ebola virus; Genetic Adjuvant; Immunostimulatory RNA; Innate Immune Agonist; Nanoplasmid; RIG-I; Venezuelan equine encephalitis virus.