NurseWeek: Ebola vaccine protects monkeys

Ebola vaccine protects monkeys
Raises hope for human version

By Nicolle Charbonneau
HealthScout Reporter
November 30, 2000


	You've read the article. Now tell us what you think. What To Do Find out more about this disease from the Centers for Disease Control and Prevention or the World Health Organization. You may also want to check this FAQ from Outbreak.Org. Read this HealthScout story about research into an Ebola vaccine developed for rodents, which ran in March.

(HealthScout). Scientists are one step closer to a vaccine against Ebola, a horrific disease that swiftly kills most people it infects.

Researchers at the National Institutes of Health (NIH) have developed a new vaccine that protects macaque monkeys from the Ebola virus, a microbe that has devastated several African villages since the 1970s.

Their findings appear in the Nov. 30 issue of the journal Nature.

Ebola's mysterious origins lie somewhere in the jungles of Africa and Asia. Three different strains of the virus, Ebola-Zaire, Ebola-Sudan and Ebola-Ivory Coast, affect humans.

Currently, doctors can do little for patients with the highly infectious virus, other than replacing lost fluids and providing comfort. Since humans don't "carry" the virus, experts believe transmission occurs through direct contact with the blood, secretions, organs, or semen of another infected person or by contact with contaminated objects.

Infected patients develop fever, weakness, muscle pain, headache and sore throat. Vomiting, diarrhea, rash, kidney and liver dysfunction, and both internal and external bleeding follow. Death usually occurs in two to 21 days.

Building on previous work with a vaccine for rodents, the NIH researchers wanted to produce a similar immune response in nonhuman primates, since they are genetically close to humans.

Working with a DNA vaccine, which enters cells and produces a line of viral proteins, lead study author Nancy Sullivan and her colleagues stocked the new vaccine with genes from Ebola-Zaire, Ebola-Sudan and Ebola-Ivory Coast.

No infected monkeys died
To give the vaccine an extra boost, Sullivan, a research fellow at the NIH Vaccine Research Center, also developed an anti-Ebola booster, made with Ebola Zaire surface proteins attached to a harmless virus.

Sullivan and her team gave four macaque monkeys three injections of the vaccine and one of the booster. Four control macaques received placebo injections. All the animals were exposed to lethal doses of an Ebola virus.

All the control monkeys died, while all monkeys that received the vaccine-booster combo survived. Three survivors showed no signs of viral infection, while one experienced a small increase in Ebola antigens in its blood that resolved after one week. "We're encouraged by the fact that the immune response in that animal was strong enough to eliminate that little bit of virus," says Sullivan.

More than six months after exposure, all four vaccinated monkeys are symptom-free with no detectable Ebola in their blood. Still, Sullivan cautions, "we don't know how long that will last."

The awful nature and mortality rate of the disease in humans gives the researchers a sense of urgency. "It's a very nasty disease," says Sullivan. Since Ebola was first described in 1976, nearly 1,100 cases, 800 of them fatal, have been documented. In some outbreaks, the death rate has been as high as 90 percent. An outbreak of Ebola which started last September in the African country of Uganda killed its 145 victim this week.

Sullivan says she cannot predict when a human vaccine will be ready for testing. "We have to do many tests first in monkeys before we'll know if this is a vaccine that will work in humans."

Dennis Burton, a professor of immunology at The Scripps Research Institute in La Jolla, Calif., says some questions remain about how great an Ebola challenge the monkeys faced. "Nobody knows for sure what dose someone is exposed to normally during an outbreak," says Burton.

Still, he says the vaccine is "a very positive development. We need to be able to respond to viruses like Ebola … not least because in the future, we may encounter some new virus that is much more easily transmitted."

This is a News story from HealthScout, a service of Rx Remedy, Inc.