An antibody isolated from a human survivor of the Ebola virus has proven effective at protecting non-human primates from the effects of the disease up to five days after infection, according to a pair of new studies published Thursday in the online edition of the journal Science.
The protein in question, a single monoclonal antibody that attacks viral pathogens, was found in blood samples belonging to a survivor of the 1995 Ebola outbreak in Kikwit, a city in Bandundu Province, Democratic Republic of the Congo, the US National Institute of Allergy and Infectious Diseases (NIAID) scientists behind the research confirmed in a statement.
The NIAID team analyzed the blood samples and found that the survivor had retained antibodies against the disease. Colleagues at the Institute for Research in Biomedicine in Switzerland were able to isolate specific proteins that could potentially be used to treat Ebola, and experts from the Army Medical Research Institute of Infectious Diseases then tested the antibody on primates.
Specifically, they administered a lethal dose of Zaire ebolavirus to four rhesus macaques. Then, five days later, then treated three of the macaques with once-daily intravenous injections of the antibody, mAb114, for three consecutive days. While the untreated creature showed signs of the disease and eventually died, those receiving the antibody remained symptom free.
Testing can now begin on humans, but some doubt its effectiveness
Researchers from the NIAID and Dartmouth College studies how the antibody neutralized the virus, and found that it attaches itself to the core of the Ebola glycoprotein, preventing the virus from interacting with a receptor on human cells. It had previously been believed that this region of the pathogen was too well hidden and could not be reached by antibodies.
The mAb114 antibody is said to be the first to demonstrate that it can neutralize the Ebola virus by blocking its interaction with cell receptors. Combined with evidence that there is a novel site of vulnerability on the Ebola virus, the evidence suggests that this could prove to be an effective way to treat the condition and warrants further exploration.
The results of their research are detailed in a pair of studies (“Protective monotherapy against lethal Ebola virus infection by a potently neutralizing antibody” and “Structural and molecular basis for Ebola virus neutralization by protective human antibodies“) currently available on the Science website, and the antibody will now be able to advance to testing on humans.
“On the face of it, this is really exciting work, but there are still uncertainties about how effective this approach might be,” Nottingham University molecular virology professor Jonathan Ball told The Guardian. “The virus will find it easier to mutate and escape the killing effects of a single antibody compared to a mixture of three, each targeting a different part of the virus.”
“The antibody cocktails can protect monkeys even when they are given after symptoms develop. This is really important, because humans usually only get diagnosed after symptoms appear,” he added. “So if the virus doesn’t mutate to stop the antibody working and it works after symptoms develop then it truly is a big step forward.”
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Image credit: NIAID
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