Even though the Ebola virus was discovered as recently as 1976, over 30,000 people have been infected since, and half have died a horrible death. Since there's no way to cure the infection, the world desperately needs a way to prevent it — and the five similar viruses in its family, the ebolaviruses.
"Since it's impossible to predict which of these agents will cause the next epidemic, it would be ideal to develop a single therapy that could treat or prevent infection caused by any known ebolavirus," said Zachary A. Bornholdt, the director of antibody discovery at Mapp Biopharmaceutical, Inc., in a press release from Albert Einstein College of Medicine regarding a new study.
Bornholdt, the study's co-lead researcher, and his colleagues, have found an antibody in the blood of an Ebola survivor that might make the perfect vaccine, giving uninfected people the ability to fight off the virus. The new study's findings were published May 18 in the journal Cell.
Ebola's Short, but Powerful Story
The ebolaviruses cause hemorrhagic fevers — unexplained bleeding and fever are hallmarks of the infection — and the infections primarily occur in Africa, but can spread worldwide if someone gets on a plane then infects others. The virus is passed through direct contact with blood or body fluids of an infected person or by contact with infected fruit bats or primates.
Five strains of Ebola virus have been identified and four are known to cause disease in humans: Ebola virus (Zaire ebolavirus), Sudan ebolavirus, Taï Forest ebolavirus, and Bundibugyo ebolavirus. Reston ebolavirus has caused disease in primates, but not in humans.
Ebola virus budding from the surface of a Vero cell.
The Centers for Disease Control and Prevention have documented 35 outbreaks of Ebola since 1976. The largest outbreak occurred from March 2014–2016 in several African countries where 28,652 people were infected and 11,325 died. Z. ebolavirus caused that outbreak.
Fluid administration, given to replace the blood and fluids lost due to bleeding and fever, is the usual treatment, but that often isn't enough to prevent death. There are 12 different Ebola vaccines in development — all specific to the Z. ebolavirus, but nothing is approved for use yet.
A Survivor's Legacy
Blood from an Ebola infection survivor has given us cause for optimism that we might be able to prevent infection with all ebolaviruses one day.
Two of the researchers in the new study — Bornholdt and Laura M. Walker at Adimab, LLC — had already isolated 349 different antibodies from a survivor of the 2014–2016 Ebola outbreak. The new multi-institutional research team found that two of those antibodies could stop infection by all five known ebolaviruses in lab animal tests. Both antibodies also protected mice and ferrets that had been exposed to a lethal dose of Zaire, Bundibugyo, and Sudan ebolaviruses from developing the diseases.
The way the new antibodies worked to stop the viruses was unusual.
When viruses attach to a cell, they are engulfed into a compartment inside the cell called a lysosome — basically a cell's trash can, which digests extra proteins that are no longer needed. The virus must "break out" of this lysosome and travel to the cell's cytoplasm to replicate and produce more infectious viral particles.
When the new antibodies were injected into the blood of animals, they met the virus while it was still in the bloodstream, then bound to protein-carbohydrate chains on the viral surface. These early steps of viral entry into the body are where antibodies usually work.
But the two new antibodies stayed with the virus on its journey to the lysosome and prevented it from breaking out and multiplying, effectively stopping the infection. The cells could then break down the virus inside the lysosome. The researchers think that the action of these antibodies so late in the infectious process is what makes them so effective.
The scientists believe they can trigger a body's immune cells to produce the two antibodies and hope this approach could be used for an effective vaccine, according to study co-leader, Kartik Chandran, of Albert Einstein College of Medicine.
On April 27, 2017, the advisory group on immunization at the World Health Organization (WHO) recommended that an experimental vaccine called rVSV-SEBOV — a vaccine that prevents Z. ebolavirus only — should be used immediately if an Ebola outbreak occurred. That outbreak may be in progress right now. On May 12, the WHO announced that nine suspected cases of Ebola have been reported in the Democratic Republic of the Congo, one of which has been confirmed.
The rVSV-SEBOV vaccine may help prevent a catastrophic outbreak, but only if the virus involved turns out to be Z. ebolavirus. The world needs an effective vaccine against all the ebolaviruses — and further developments from the research team working on the two promising antibodies can't come a moment too soon.
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Cover photo by Staff Sgt. Benjamin W. Stratton/US Air Force
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