Posted on 11/19/2003 10:04:12 PM PST by neverdem
The first test in humans of an experimental vaccine against the deadly Ebola virus began yesterday, government scientists said.
The vaccine, administered by injection, was designed to try to prevent outbreaks of the lethal hemorrhagic fever where it occurs naturally in Africa. It is also a bid to thwart any efforts to use the highly infectious virus as a bioterrorist agent.
As part of a standard three-stage process, the first phase involves testing the vaccine's safety. Scientists also plan to measure immune responses among volunteers receiving the shots.
No effective treatment exists against the viral infection, which kills up to 90 percent of victims quickly from severe internal bleeding. Ebola was discovered in 1976 in the Republic of Congo, then Zaire. This week, the World Health Organization reported a new outbreak of Ebola in that country, attributing 11 deaths in as many cases to it.
The experimental DNA vaccine is synthesized using modified, inactivated genes from the Ebola virus. Because it does not contain any infectious material from the virus, recipients cannot get the disease, said Dr. Gary Nabel, who directs the institute's Vaccine Research Center.
Researchers plan to test the vaccine on 27 people, ages 18 to 44. They are expected to receive three injections of either the experimental vaccine or a placebo at the National Institute of Allergy and Infectious Diseases in Bethesda, Md., over two months. They will then be monitored for a year.
The first volunteer, Steve Rucker, a 36-year-old research nurse at the institute, said in a phone interview that he felt fine after the vaccine was injected in his left arm yesterday.
Mr. Rucker, of College Park, Md., said he was participating because he believed that the findings from animal tests were "extremely promising."
Dr. Nabel said in a telephone interview that only a handful of individuals, mostly institute employees, had volunteered for the study and that his team needed at least 20 more volunteers. Details are posted at www.clinicaltrials.gov.
The vaccine is made by Vical, a biotechnology company in San Diego that has collaborated with Dr. Nabel's team as they tested the vaccine on animals.
The goal is to use the Vical vaccine and another one to protect against Ebola in a prime-boost strategy. Under those conditions, the Vical vaccine would be given first to prime the immune system. Then a different vaccine, which uses an adenovirus (that causes colds) to bolster the immune system that had been primed by the Vical vaccine. The second vaccine is still being developed for human use; the first tests in volunteers are expected to begin next year, Dr. Nabel said.
Tests of the prime-boost strategy are expected to begin in 2005. But the schedule depends in part on the findings from the current tests.
Of the volunteers in the Vical study, 21 will get injections of the vaccine and 6 a placebo. Neither the volunteers nor the scientists will know which volunteers received which type of injection until the scientists analyze the results.
The government's program to defend against bioterrorism has helped accelerate development of a vaccine, said Dr. Anthony S. Fauci, the institute's director. "An effective Ebola vaccine not only would provide a life-saving advance in countries where the disease occurs naturally, it also would provide a medical tool to discourage the use of Ebola virus as an agent of bioterrorism," he said.
The human study is based on animal experiments in which Dr. Nabel's team gave the two vaccines separately to guinea pigs and monkeys. When the researchers exposed the animals to Ebola virus, they found 100 percent protection, Dr. Nabel said.
A single injection of the adenovirus vaccine provided faster protection than expected.
Because it is unethical to deliberately expose humans vaccinated against Ebola to the virus because the disease is so lethal, scientists and government officials might have to apply what they call "the two-animal rule." Government officials recently adopted the rule for possible licensing of a vaccine that proves safe in humans and shows adequate protection against a deliberate infection in two species of animals.
Dr. Nabel said he envisioned that health workers might someday vaccinate against Ebola the same way epidemiologists used the smallpox vaccine to eradicate that disease. The strategy involved vaccinating all possible contacts of the initial cases and then their contacts as well.
Scientists might test the vaccine in an outbreak of Ebola under emergency conditions.
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