By DENISE GRADY
Two new Ebola vaccines have passed an important test, protecting monkeys against the strain of the virus responsible for the current deadly outbreak, researchers reported on Wednesday. Only one dose was needed, and there were no apparent side effects.
The vaccines have not yet been tested in people, but safety trials in healthy volunteers will probably begin early this summer, said Thomas W. Geisbert, an Ebola expert at the University of Texas Medical Branch in Galveston, and the senior author of a report published on Wednesday in the journal Nature.
Tests in nonhuman primates are an important step, because those animals are far more closely related to humans than are other lab animals.
The study of the new vaccines involved 10 macaques. Eight were vaccinated, and two, as controls, were not.
The vaccinated animals showed no signs of side effects from the vaccine, Dr. Geisbert said. On the 28th day after the vaccines were given, all the monkeys were injected with Ebola virus from the current outbreak. No vaccinated monkeys became ill, but the unvaccinated ones both died within a week.
The two new vaccines are improved versions of an older one that was licensed to Merck and is now being tested for efficacy in people in Liberia. The older vaccine can cause unpleasant side effects like fever and pain in joints and muscles. One safety test of it was stopped temporarily last year because of the joint pains. (Another vaccine, licensed to GlaxoSmithKline, is also being tested in West Africa, and has not had serious side effects.)
The side effects of the vaccine licensed to Merck were not considered serious enough to block its use. But they could pose problems during an outbreak because they resemble early symptoms of Ebola, so patients with a fever soon after vaccination might have to be tested or even quarantined until it was determined whether they were infected or just having a reaction to the shot.
“I think these improved vaccines should fix that,” Dr. Geisbert said in an email.
The two newer vaccines are being made by Profectus BioSciences. The company’s chief scientific officer, John Eldridge, said the company had received $55 million in recent months to work on Ebola vaccines from a consortium of government agencies that includes the National Institutes of Health and the Department of Defense. He said that Profectus was also working on another vaccine that would protect people against several strains of Ebola as well as Marburg, a related virus. None of the vaccines is likely to be approved much before 2017, he said.
Several authors of the Nature report are scientists employed by Profectus. The study described in the report was paid for by the National Institutes of Health and the University of Texas Medical Branch.
The Merck and Profectus Ebola vaccines are made from vesicular stomatitis virus, or V.S.V., which causes a mouth disease in cattle but rarely infects people. Profectus specializes in vaccines based on V.S.V. and has developed several for different diseases, but none have been marketed yet.
In the Ebola vaccines, the stomatitis virus is genetically engineered to make a protein from the surface of the Ebola virus, which stimulates the immune system to recognize Ebola, fight if off and prevent infection.
The side effects are caused by the stomatitis virus, which replicates in the bloodstream. In the newer vaccines the V.S.V. has been genetically altered further to attenuate it, meaning that it will not replicate or reach such high blood levels as the original. The lower levels reduce side effects but do not diminish the ability of the vaccine to create immunity, Dr. Eldridge said.
Half the monkeys in the study received a highly attenuated version, and the other half a less attenuated form. The two vaccines worked equally well, so Profectus plans to develop the less attenuated one, because it should be safer, Dr. Eldridge said.
The 28-day period between vaccination and exposure to the virus was picked to match up with previous studies, so that results could be compared, but the vaccine probably starts working much sooner than that, Dr. Geisbert said. Future studies will try to find out just how quickly the vaccine works. (NY Times)
you may also like: