A vaccine that protects monkeys against the highly deadly Marburg virus, a relative of Ebola, may also provide the first known treatment for the infection, researchers reported Wednesday.
Now they hope to use a similar vaccine to try to treat Ebola. Both viruses have caused rare, but frightening and deadly, outbreaks in Africa and both are considered to be potential bioterror agents.
The vaccine was created using a harmless virus known as vesicular stomatitis virus, or VSV. The researchers took out one gene and replaced it with a key gene from Marburg virus.
When they infected monkeys with Marburg and then administered the vaccine, the monkeys were protected and stayed healthy, said Thomas Geisbert of the U.S. Army Medical Research Institute of Infectious Diseases.
Unvaccinated monkeys died within 10 to 12 days.
“We were very surprised,” Geisbert said.
Geisbert, whose team worked with colleagues at the National Microbiology Laboratory at the Public Health Agency of Canada, published the findings in this week’s issue of the Lancet medical journal.
He said it may be a while before the vaccine is tested in people but hopes it is a first step.
Marburg virus killed more than 300 people — 90 percent of those infected —in Angola last year. Ebola is usually somewhat less deadly and killed 254 people between 2001 and 2005 in Gabon and the Democratic Republic of Congo.
There is no cure for either diseases, both caused by a family of viruses known as filoviruses. They lead to a particularly nasty form of hemorrhagic fever and victims usually die of multiple organ failure and shock.
A few victims have been lab or medical workers experimenting with the virus or trying to help patients who suffered “needle-stick” accidents that tend to infect the victim with a large dose of virus.
“In the 1976 Ebola outbreak in former Zaire (now the Democratic Republic of Congo) there were 85 confirmed needle sticks because they were re-using needles. All 85 folks died that got stuck with a needle and the disease course went faster,” Geisbert said in a telephone interview.
“In a real-world situation most folks are going to be exposed to much lower doses of virus by different routes.”
If the vaccine was so effective in monkeys given high doses of virus, it should be effective in an outbreak scenario in which people typically get lower doses, Geisbert said.
Close contact is needed to transmit both Ebola and Marburg. Geisbert said relatives preparing a victim for burial often become infected, possibly through infected blood getting into small cuts or abrasions, or by touching blood or other bodily fluids and then touching the nose, mouth, lips or even eyes.
It may take some time to develop and license a human vaccine, but Geisbert said it may be possible to use an experimental version in case of a lab accident.
It is not certain whether a similar vaccine against Ebola will be as effective because of small but significant differences between the viruses, Geisbert said.
He also said Wyeth was testing a similar vaccine approach for the AIDS virus.