Vaccine protects monkeys from Ebola infection

From Christy Feig
CNN Medical Correspondent

(CNN) -- For the first time researchers have found a potential vaccine for the Ebola virus. The vaccine was tested only in monkeys, but it could be a significant development because doctors currently have nothing to treat or prevent infections.

The current Ebola outbreak in Uganda has killed 145 people. Since it first appeared in 1976, the virus has killed more than 800, infecting nearly 1,100. The disease causes its victims to bleed to death within days of infection.

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The vaccine was created by Dr. Gary Nabel and colleagues at the Vaccine Research Center at the National Institutes of Health. Research appears in the journal Nature.

"We found that it's possible to protect against the lethal effects of the Ebola virus in a primate model. By vaccinating animals ahead of time against Ebola virus we were able to prevent them from dying from the infection when they were challenged with virus," said Nabel.

Nabel and his colleagues tested the vaccine in four monkeys. All of them survived after being infected with the virus, but four others that didn't get the vaccine died when they were given Ebola.

The vaccine contains two parts. The first is a genetic vaccine made up of strands of DNA from Ebola and is designed to prime the immune system. These types of vaccines closely mimic virus infection and the immune system responds accordingly. But that response alone is not always strong enough, so researchers added a booster vaccine -- a piece of the virus added to a common cold bug. This boosts the immune system against Ebola.

There are still several outstanding issues. The vaccine must prove to be effective against several strains of the disease. And it must be tested in humans to see if the protection carries over.

"The animal model that we've used is the closest one to the disease that affects humans," explained Nabel. "So by studying the disease in a highly relevant animal model, we hope to be able to apply these lessons to humans and to promote the development of a vaccine for people."

In human trials the researchers will test the vaccine in health care workers in countries most often hit by the outbreaks. They will not infect the workers with Ebola, but will wait to see if they are protected when they are exposed while treating patients.

Nabel said it could be three years or more before they know if the vaccine is safe and effective for humans. If it is, it might also help treat patients who already have the disease.

When a person is naturally infected with Ebola, it takes the immune system two to three weeks to recognize the virus and mount a response. By that time they disease may have already killed them. In theory, giving the vaccine to patients recently infected with the virus may make their immune system recognize the infection and give it the strength to fight.

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Nature Online
WHO - Ebola Hemorrhagic Fever
CDC - Preventing Infectious Diseases

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