Inactivated Rabies Virus-Based Ebola Vaccine Preserved by Vaporization Is Heat-Stable and Immunogenic Against Ebola and Protects Against Rabies Challenge

Background. Ebola virus (EBOV) is a highly lethal member of the Filoviridae family associated with human hemorrhagic disease. Despite being a sporadic disease, it caused a large outbreak in 2014-2016 in West Africa and another outbreak recently in the Democratic Republic of Congo. Several vaccine candidates are currently in preclinical and clinical studies but none are stable without cold chain storage. Methods. We used preservation by vaporization (PBV), a novel processing technology to heat-stabilize FiloRab1 (inactivated rabies-based Ebola vaccine), a candidate Ebola vaccine, and stored the vials at temperatures ranging from 4 degrees C to 50 degrees C for 10 days to 12 months. We immunized Syrian hamsters with the best long-term stable FiloRab1 PBV vaccines and challenged them with rabies virus (RABV). Results. Syrian hamsters immunized with FiloRab1 PBV-processed vaccines stored at temperatures of 4 degrees C and 37 degrees C for 6 months, and at 50 degrees C for 2 weeks, seroconverted against both RABV-G and EBOV-GP. Notably, all of the FiloRab1 PBV vaccines proved to be 100% effective in a RABV challenge model. Conclusions. We successfully demonstrated that the FiloRab1 PBV vaccines are stable and efficacious for up to 6 months when stored at temperatures ranging from 4 degrees C to 37 degrees C and for up to 2 weeks at 50 degrees C.