The Ebola virus causes a hemorrhagic fever that progresses rapidly and that has high mortality rates. An experimental vaccine involving a combination of DNA immunization and boosting with adenoviral vectors (ADV) against the most lethal subtype (Zaire) of Ebola virus exists. However, this vaccine requires more than 6 months to achieve complete immunization, rendering it impotent in limiting an acute epidemic. In the August 7 Nature, Nancy J. Sullivan and colleagues at the National Institutes of Health show that a single vaccine injection with ADV vectors encoding viral proteins can be an effective accelerated vaccination strategy against Ebola virus in monkeys (Nature, 424:681-684, August 7, 2003).

Sullivan et al. vaccinated cynomolgus macaques with an ADV vector encoding the Ebola glycoprotein (GP) and nucleoprotein (NP) vectors. They observed that after immunization with ADV–GP/NP, the antibody response to immunization was more rapidly induced than after DNA priming and ADV boosting, but it was of a lower magnitude. However, the ADV–GP/NP immune response offered a highly effective protection against the Ebola virus, even if the challenge was 28 days after vaccination. The level of protection correlated well with the generation of Ebola-specific CD81 T-cell and antibody responses.

"Should this vaccine approach prove effective in humans, our finding raises the possibility that ring vaccination could be used to contain outbreaks, similar to smallpox in the past. This result also suggests alternative strategies for vaccination against Ebola or other acute pathogenic diseases," conclude the authors.