Genetically modified rabies virus-vectored Ebola virus disease vaccines are safe and induce efficacious immune responses in mice and dogs

- Rabies virus-based vaccines expressing the Zaire or Sudan Ebola virus glycoprotein (ZGP or SGP) were generated.
- ZGP or SGP expression did not increase the virulence of the vector.
- Both rERAG333E/ZGP and rERAG333E/SGP are safe and immunogenic as oral or inactivated vaccine in mice.
- Dogs orally vaccinated with rERAG333E/ZGP developed efficacious Ebola and rabies virus neutralizing antibodies.

Ebola viruses (EBOVs) are zoonotic pathogens that cause EBOV disease (EVD) with high case fatality in humans. Currently, EVD vaccines are still under development in several countries. Here, we generated two recombinant rabies viruses (RABVs), rERAG333E/ZGP and rERAG333E/SGP, expressing the Zaire EBOV glycoprotein (ZGP) or Sudan EBOV glycoprotein (SGP) gene based on a modified ERA vaccine strain (rERAG333E) vector platform. The recombinant RABVs retained growth properties similar to those of the vector virus in BSR cell culture and efficiently expressed ZGP or SGP. After intracerebral (i.c.) inoculation with rERAG333E/ZGP or rERAG333E/SGP, all adult mice showed no signs of disease or weight loss and suckling mice maintained similar survivorship curve as those mice inoculated with control vector rERAG333E, demonstrating that ZGP or SGP expression did not increase the virulence of the vector. Mouse immunization studies showed that vaccination with rERAG333E/ZGP and rERAG333E/SGP induced Zaire or Sudan EBOV neutralizing antibody (VNA) responses and IgG, IgG2a responses to ZGP or SGP, suggesting their potential as oral or inactivated bivalent vaccines against rabies and EVD. Most importantly, all dogs immunized orally with rERAG333E/ZGP developed long-lasting ZEBOV and RABV VNA responses with or without previous rabies vaccine immunization history. Live rERAG333E with EBOV GP thus appear to have the potential to be oral vaccines for free-roaming animals in endemic areas of EVD and rabies, and may serve as inactivated vaccines for use in humans.