Ebola vaccine tested on chimps could save wild apes

Thanks to new molecular diagnostics, scientists can pinpoint the cause of death for many endangered African apes, and quite often the finger points to virulent pathogens. Recent Ebola virus outbreaks, for example, have killed nearly a third of the world’s gorillas. Now researchers have tested an Ebola vaccine on a group of captive chimpanzees, and results from this clinical trial of sorts show a lot of promise for vaccinating apes in the wild.

Instead of live (and weakened) viruses, the vaccine uses noninfectious, virus-like particles — in particular, fragments of the protein coat that surrounds the virus. This trains the immune system to recognize and build up defenses against Ebola, but without the risk of infecting the animal. This experimental vaccine is being developed for humans, and it has previously been given to 80 macaques, who were then exposed to the virulent Zaire species of Ebola virus without serious health complications.

To evaluate whether it’s safe for wild apes, a team led by Peter Walsh from the University of Cambridge tested six chimps between the ages of 17 and 31 at the New Iberia Research Center in Louisiana. The team gave multiple doses of two vaccine formulations to the chimps over about two months and monitored them for at least 12 weeks. Pictured above, one of the captive chimpanzees.

Vaccinated chimps maintained normal weight, blood chemistry, and blood cell count, and they showed no symptoms of an Ebola infection. Furthermore, the chimps, who were never exposed to the virus, developed a strong immune response similar to that of the macaques who survived exposure. The team detected Ebola antibodies as early as two weeks after the first dose for some chimps and within two weeks of the second vaccination for all of them. Then the researchers transferred those antibodies to mice who were exposed to the virus. Mouse survival rates rose from zero to between 30% and 60%, depending on the formulation.

Licensing human vaccines is so expensive that only a few make it to market, leaving behind a large pool of experimental vaccines with excellent results in non-human primate trials. This study shows how even modestly funded researchers could co-opt those orphan vaccines, adapting them as conservation tools that could stave off wild ape extinction. — Janet Fang | 29 May 2014

Source: Warfield, K.L. et al. Vaccinating captive chimpanzees to save wild chimpanzees, Proceedings of the National Academy of Sciences (2014). doi/10.1073/pnas.1316902111

Image: Jeremy Breaux (New Iberia Research Council, New Iberia, LA)