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One shot of an experimental vaccine made from two Ebola virus gene segments incorporated into a chimpanzee cold virus vector (called chimp adenovirus type 3 or ChAd3) protected all four macaque monkeys exposed to high levels of Ebola virus 5 weeks after inoculation, report National Institutes of Health (NIH) scientists and their collaborators. The ability of the ChAd3 Ebola virus vaccine to elicit rapid protection in monkeys is notable as the world health community battles an ongoing Ebola virus disease outbreak in West Africa. While the protective effects of the single shot waned over time, two out of four inoculated animals were protected when challenged with Ebola virus 10 months after vaccination.
The research team, headed by Nancy J. Sullivan, PhD, of the National Institute of Allergy and Infectious Diseases Vaccine Research Center, also demonstrated increased levels of durable protection using an additional vaccine. They inoculated four macaques first with the ChAd3 Ebola vaccine, then eight weeks later with a booster vaccine containing Ebola virus gene segments incorporated into a different vector (a poxvirus). Ten months after the initial inoculation, four out of four animals that received both shots were fully protected from infection with high doses of Ebola virus, demonstrating that the prime-boost regimen resulted in durable protection.
The research team included scientists from Okairos, a Swiss-Italian biotechnology company now part of GlaxoSmithKline, and the U.S. Army Medical Research Institute of Infectious Diseases. The experimental ChAd3 Ebola vaccine used in these non-human primate studies is the same one currently being tested in an early-stage human clinical trial at the NIH in Bethesda, Maryland.
Reference: Stanley DA, et al. Chimpanzee adenovirus vaccine generates acute and durable protective immunity against ebolavirus challenge. Nature Medicine DOI:10.1038/nm.3702 (2014).
Source: National Institute of Allergy and Infectious Diseases