Further characterization of the immune response in mice to inactivated and live rabies vaccines expressing Ebola virus glycoprotein

We have previously developed (a) replication-competent, (b) replication-deficient, and (c) chemically inactivated rabies virus (RABV) vaccines expressing Ebola virus (EBOV) glycoprotein (GP) that induce humoral immunity against each virus and confer protection from both lethal RABV and mouse-adapted EBOV challenge in mice. Here, we expand our investigation of the immunogenic properties of these bivalent vaccines in mice. Both live and killed vaccines induced primary EBOV GP-specific T-cells and a robust recall response as measured by interferon-γ ELISPOT assay. In addition to cellular immunity, an effective filovirus vaccine will likely require a multivalent humoral immune response against multiple virus species. As a proof-of-principle experiment, we demonstrated that inactivated RV-GP could be formulated with another inactivated RABV vaccine expressing the nontoxic fragment of botulinum neurotoxin A heavy chain (HC50) without a reduction in immunity to each component. Finally, we demonstrated that humoral immunity to GP could be induced by immunization of mice with inactivated RV-GP in the presence of pre-existing immunity to RABV. The ability of these novel vaccines to induce strong humoral and cellular immunity indicates that they should be further evaluated in additional animal models of infection.