Immunization with vesicular stomatitis virus vaccine expressing the Ebola glycoprotein provides sustained long-term protection in rodents

Ebola virus (EBOV) infections cause lethal hemorrhagic fever in humans, resulting in up to 90% mortality. EBOV outbreaks are sporadic and unpredictable in nature; therefore, a vaccine that is able to provide durable immunity is needed to protect those who are at risk of exposure to the virus. This study assesses the long-term efficacy of the vesicular stomatitis virus (VSV)-based vaccine (VSVδG/EBOVGP) in two rodent models of EBOV infection. Mice and guinea pigs were first immunized with 2×10⁴ or 2×10⁵ plaque forming units (PFU) of VSVδG/EBOVGP, respectively. Challenge of mice with a lethal dose of mouse-adapted EBOV (MA-EBOV) at 6.5 and 9 months after vaccination provided complete protection, and 80% (12 of 15 survivors) protection at 12 months after vaccination. Challenge of guinea pigs with a lethal dose of guinea pig-adapted EBOV (GA-EBOV) at 7, 12 and 18 months after vaccination resulted in 83% (5 of 6 survivors) at 7 months after vaccination, and 100% survival at 12 and 18 months after vaccination. No weight loss or clinical signs were observed in the surviving animals. Antibody responses were analyzed using sera from individual rodents. Levels of EBOV glycoprotein-specific IgG antibody measured immediately before challenge appeared to correlate with protection. These studies confirm that vaccination with VSVδG/EBOVGP is able to confer long-term protection against Ebola infection in mice and guinea pigs, and support follow-up studies in non-human primates.