Ebola Survivor's Antibodies May Yield a Cure for All Known Species of the Virus
Each species of ebolavirus has its own characteristics, but these two antibodies have an amazing potential to thwart any of them from causing an infection.
In the 41 years since Ebola’s discovery, the various ebolaviruses that cause the hemorrhagic fever have sparked more than 24 outbreaks and killed thousands of people. The 2014-2016 outbreak in West Africa was by far the most lethal, sickening more than 29,000 people and killing over 11,000. And contagion continues to occur. This month, the World Health Organization declared another outbreak in the Democratic Republic of Congo.
Both of these eruptions were caused by the Ebola Zaire virus, but there are four other species of ebolavirus that can also infect humans. This variety has posed a significant challenge to scientists. How can they use one drug to fight all of the viruses, when each of them has its own specific anatomy?
Researchers now think they may have found a solution: a human antibody that can stop all five species of ebolavrius from infecting human cells. The study, published in the journal Cell, identified two antibodies from an anonymous survivor of West Africa’s epidemic that can fight all ebolaviruses at once.
John M. Dye, viral immunology branch chief at the US Army Medical Research Institute of Infectious Diseases and the study’s co-lead author, told Seeker that investigators hadn’t believed it was possible to find an antibody that could stop multiple species of the virus. But in 2016, a panel of antibodies from Ebola Patient 45 was released, allowing researchers to test different antibodies to determine whether they would be effective against fighting the disease. They found two antibodies, ADI-15878 and ADI-15742, that prevented ebolaviruses from replicating within human cells and causing an infection.
In normal cases, the virus gets into the host cell through the endosome, a small compartment that is separated from the rest of the cell by a membrane. Inside the endosome, a glycoprotein on the virus’s surface receives a signal from the host cell to merge, and deploys loop-shaped structures that shoot from the surface of the virus. Think of them like harpoons, said study co-leader Kartik Chandran, a professor of microbiology and immunology at the Albert Einstein College of Medicine. Known as fusion loops, they latch onto the host cell’s membrane and pull it close enough to the virus so that it can fuse with the cell.
At that point, it’s game over. Once the virus fuses into the rest of the cell and replicates, it can start spreading the infection to the rest of the body.
The antibodies discovered by the researchers disrupt this process. Antibodies are proteins that float around in the blood stream in search of a specific virus that they target. In the case of Ebola, the antibodies “hitchhike” with the virus into the cell, explained Dye, and then bind with the glycoprotein, leaving the fusion loops unable to deploy. This makes the virus incapable of replicating and spreading the infection.
Each strain of ebolavirus has its own glycoprotein, but remarkably, these two antibodies can bind to all of them. Dye said that they “have an amazing potential to thwart any ebolavirus.”
The first time they saw the antibodies neutralize all five of the viruses “was pretty incredible,” said Zachary Bornholdt, director of antibody discovery at Mapp Biopharmaceutical and another co-lead on the study.
The research team hopes that these antibodies will be able to fight ebolaviruses that have not yet been discovered. The fifth known ebolavirus, called Bundibugyo, was identified only in 2007.
“We don’t know what’s going to come out of the woods next,” Dye said.
But given that these antibodies appear to work against all current ebolaviruses, it is likely they will be able to work against future strains as well.
This discovery could lead to several different types of treatments, including a vaccine. It could also help create a powerful prophylactic treatment that could be given to people who may have been exposed to the virus.
“If you give the antibodies a head start,” Chandran said, “the virus is toast.”
The team has already moved into primate trials, and are collaborating with another group of Ebola researchers that also published a paper this week about Ebola antibodies, though theirs were found in monkeys.
Dye estimated that there could be a human trial with these antibodies in as little as two to three years, depending on when the next outbreak is. The interaction between antibodies and glycoproteins could also be studied to develop treatments for other viral illnesses, he said, such as Dengue fever and HIV.
Current studies are encouraging, said Chandran. “We’re very optimistic.”
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