The potential for another Ebola epidemic is high, so work on developing a treatment or vaccine for the disease is of paramount importance. To this end, two new studies published in the journal Science have revealed that antibodies taken from an Ebola survivor protected monkeys infected with the disease. Potentially, this could be the first step in developing a workable vaccine for use in afflicted humans who are otherwise doomed to die.
The most recent Ebola epidemic killed over 11,000 people. It is easily the most devastating outbreak of the virus in history, killing more people than in every previous outbreak combined. Although the main phase of the epidemic appears to be over, cases keep appearing long after regions are said to be Ebola-free.
Not everyone dies from Ebola: fatalities rates over the course of history and in different parts of the world have varied from 25 to 90 percent. Those fortunate enough to survive will develop antibodies, the “handcuffs” of the immune system that pin down the invading pathogen next time it appears, ready for the white blood cells to devour and neutralize them.
In order to investigate how the antibodies of a survivor would respond in the bloodstream of an infected monkey, a team from the National Institute of Allergy and Infectious Diseases (NIAID) looked back at the 1995 Ebola epidemic. One of the survivors of the outbreak, centered on Kikwit in the Democratic Republic of the Congo, donated a sample of his blood to the researchers.
A single type of antibody, identified to act against the Ebola virus, was isolated. At the same time, four rhesus monkeys were given a lethal dose of the virus, and left for five days. One was left untreated, and within nine days died, showing symptoms of the viral infection.
The Ebola virus glycoprotein (blue) bound by the antibody mAb114 (pink/white) and another similar antibody mAb100 (purple/white). NIAID
The remaining three were given daily injections containing copies of this antibody, known as mAb114 – but only after five days had passed. Not only did these three macaques survive, but they remained completely free of any Ebola symptoms.
This incredible result first confirms that the original survivor still had immunity to the disease over a decade after the infection. “This is probably the longest ever recorded immunity to the Ebola virus,” Dr. Nancy Sullivan, the current chief of the Biodefense Research Section of NIAID and coordinator of this research, told IFLScience.
Significantly, this research also demonstrates that the antibody involved was incredibly effective at neutralizing the virus. Another antibody, mAb100, was shown to have the same neutralizing effect.
These antibodies were seen to bind to part of the virus called the glycoprotein (GP), a surface segment that is used to attach itself to host cells. A specific section of the GP, the receptor binding domain, was previously thought to be unreachable by antibodies – it is thoroughly concealed by other parts of the virus, and only becomes truly exposed when the virus has infiltrated the inside of a cell. This groundbreaking research demonstrates that these antibodies are able to do something completely unprecedented and save lives as a result.
At present, two experimental vaccines for Ebola are being trialed, but this new research may lead to the production of a third. “I was part of the development for the very first Ebola vaccine,” Sullivan noted. “And this research will certainly help in developing future vaccines for the virus.”
“We’re very proud of this work,” she added.