A FAST-ACTING Ebola vaccine might help to contain outbreaks of the deadly disease. A single shot of the experimental vaccine protected monkeys from the virus within a month, compared with six months for an earlier multi-injection regime.
鈥淲e may be able to create a ring of vaccination around an outbreak to contain it,鈥� says Gary Nabel of the Vaccine Research Center at the National Institutes of Health in Bethesda, Maryland.
And if the Ebola vaccine proves safe and effective, he hopes that the same approach could be used to inoculate people against other infections for which there are currently no vaccines, such as SARS and malaria.
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Because Ebola is so deadly, creating a conventional vaccine of inactivated whole virus or a live weakened strain is much too dangerous. Instead, Nabel鈥檚 team originally tried a two-pronged method: injecting animals with the DNA that codes for three Ebola viral proteins to stimulate a killer T-cell response, followed by an adenovirus 鈥� a cold virus 鈥� modified to carry these proteins to stimulate antibody production. The adenovirus cannot replicate.
Nabel noticed that the modified adenovirus alone stimulated rapid antibody production, and even produced a T-cell response, although at a lower level than the DNA vaccine. To the team鈥檚 surprise, a single shot of the adenovirus proved to be enough: after 28 days, eight monkeys all survived doses of the virus that killed two unprotected animals (Nature, vol 424, p 681).
鈥淭hat is super-solid protection,鈥� says C. J. Peters, a vaccine researcher at the University of Texas, Galveston. He says that a single-shot vaccine could also be useful for vaccinating other wild animals such as chimps and gorillas, which in some regions are being wiped out by Ebola (快猫短视频, 12 April, p 11).
One problem with vaccinating humans is that people already have an immune response to some strains of adenovirus, which would reduce the response to the vaccine strain. This means that it may be necessary to develop several different strains.