A Synthetic Micro-consensus DNA Vaccine Induces Potent Immune Responses Against Diverse Strains of Marburgvirus
Sarah Elliott1, Jacqueline Chu1, Jian Yan2, Ami Patel1, Jingjing Jiang2, Stephanie Ramos2, Kate Broderick2, David Weiner1
1The Wistar Institute, Philadelphia, PA, USA; 2Inovio Pharmaceuticals, Plymouth Meeting, PA, USA
Outbreaks caused by filoviruses from the genus Marburgvirus have emerged sporadically since 1967, exhibiting a severe and often fatal course of disease in humans. There are currently no approved prophylactic approaches against severe Marburgvirus infection, and treatment is largely supportive given a lack of approved antiviral therapies. Here, we demonstrate a novel, synthetic, micro-consensus-based DNA vaccine against Marburgvirus. Engineered plasmid DNA is relatively simple to manufacture, can be developed in temperature-stable formulations of crucial benefit for rapid distribution to remote regions.
We built a phylogenetic tree of Marburg (MARV) and Ravn (RAVV) viral GP sequences to design three synthetic micro-consensus plasmid DNA constructs encoding optimized Marburgvirus glycoprotein (GP). DNA vaccine constructs were injected intramuscularly accompanied by CELLECTRATM 3P electroporation in BALB/c mice. A single dose of each plasmid DNA construct induced potent antigen-specific antibodies in mice, which bound to recombinant GP from MARV-Angola, MARV-Musoke, and RAVV. Immunization also induced potent yet distinct mouse IFN cellular responses against peptides from either MARV-Angola or RAVV GP. Immune responses were boosted by subsequent DNA immunizations, yielding geometric mean antibody endpoint dilution titers ranging 104-106 and IFN ELISpot responses 1,500 spots per million splenocytes. Immune responses persisted over two months after the last immunization and demonstrated similar magnitude in vaccinated BALB/c (MHC haplotype H2d) versus C57BL/6 (H2b) mice.
To induce pan-Marburgvirus immune responses, we mixed all three plasmid DNA constructs and delivered simultaneously. This Marburgvirus DNA vaccine cocktail generated simultaneously potent immune responses to highly-diverse MARV and RAVV antigens. Studies are underway toward demonstrating protection against severe MARV and RAVV infection in a guinea pig model of pathogenic infection. We have also evaluated co-administration of this DNA vaccine cocktail and our previously-published Ebola Zaire DNA vaccine with the aim of developing a sustainable pan-filovirus vaccine.