An mRNA Vaccine Encoding the Ebola Virus Glycoprotein Induces High Neutralizing Antibody Titers and Provides Strong Protection Against Lethal Infections in Mouse Models

Zachary R Stromberg¹Elvia Silva²Sara C Johnston³Dylan M Johnson²Dominique Hall⁴Emmanuel F Adeji⁵John Altin⁶Abisola Abisoye-Ogunniyan⁴Travis Gollott⁴Wei He⁴Iris K A Jones²Steven Kwilas³Sean J Lund²Heather Mead⁶Georgia A Nelson⁶Lisa Ouyang²Sandra K G Peters⁴Jennifer L Schwedler²Caleb Z Trecazzi⁴Matthew W Turner¹Chunyan Ye⁷Steven Bradfute⁷Nicholas O Fischer⁴Jay Hooper³Jason Ladner⁵Amy Rasley⁴Oscar Negrete^2*

• ¹Pacific Northwest National Laboratory, Richland, United States
• ²Sandia National Laboratories California, Livermore, United States
• ³US Army Medical Research Institute of Infectious Diseases, Fort Detrick, United States
• ⁴Lawrence Livermore National Laboratory, Livermore, United States
• ⁵Northern Arizona University, Flagstaff, United States
• ⁶Translational Genomics Research Institute Flagstaff, Flagstaff, United States
• ⁷The University of New Mexico, Albuquerque, United States

Ebola virus (EBOV) is the causative agent of Ebola disease (EBOD), a viral hemorrhagic fever with a notably high case fatality rate. Current treatments for EBOD are limited to monoclonal antibodies or two licensed viral vector vaccines, a recombinant vesicular stomatitis virus (rVSV)-vectored vaccine or an adenovirus and modified vaccinia Ankara regimen. However, comparisons of protection, efficacy, and durability with alternative nucleotide platforms remain understudied. Here, we evaluated the immunogenicity of an mRNA vaccine expressing the EBOV glycoprotein (GP) in parallel with rVSV-and DNA-based vaccine platforms. The mRNA EBOV-GP vaccine, formulated in lipid nanoparticles, elicited significantly higher levels of total IgG and neutralizing antibody titers compared to the rVSV-EBOV-GP vaccine. Linear antibody epitope analysis indicated a preference for targeting the mucin-like domain in EBOV-GP1 following rVSV-based vaccination, while the mRNA platform distinctly targeted the internal fusion loop of EBOV-GP2. After characterizing the immunogenicity of the mRNA vaccine, two models of EBOD were used to demonstrate its protective efficacy: a surrogate rVSV-based challenge model of EBOD using type-I interferon deficient C57BL/6 mice and infection of BALB/c mice with authentic mouse-adapted EBOV. In both studies, the EBOV mRNA vaccine fully protected the mouse cohorts against morbidity and mortality. Additionally, the EBOV mRNA vaccine produced greater neutralizing antibody titers compared to the DNA EBOV-GP vaccine. These results suggest that an mRNA vaccine expressing EBOV-GP can induce robust, functional humoral responses that are protective against EBOD, warranting further development as an alternative to, or as part of a vaccine strategy including, viral vectored vaccines.