Experimental Ebola Serum Likely Treating Sick Americans

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An American doctor working in West Africa and another health care worker, also American, who contracted Ebola there have both received experimental treatments for the deadly viral disease, according to news reports.

Nancy Writebol, a worker with the charity Samaritan's Purse, received an experimental serum, and Dr. Kent Brantly, from the same charity, received a blood transfusion from a patient who recovered from Ebola, according to NBC News. One or both of the health care workers are also being flown to an isolation unit in an American hospital for treatment, according to news reports.

Watch "Ebola: Are We Next?" on Thursday, Sep. 18, starting at 9/8c on both Discovery Channel and Discovery Fit & Health.

Though there are conflicting reports, and no one is saying exactly what the experimental serum is, its likely that both of the reported methods contained antibodies to the Ebola virus, said Dr. William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center in Nashville, Tenn. Delivering antibodies to a patient could slow the virus's replication, and give the immune system time to recover.

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"There is a long tradition of using immune serum as treatment," Schaffner told Live Science. "You give the person antibodies, and you would hope that those antibodies would then bind the viruses and interfere with their multiplication."

No current treatments

This Ebola outbreak is the largest in history and has so far claimed 729 lives in Sierra Leone, Guinea and Liberia. Doctors without Borders has said that the crisis is "out of control." Sierra Leone has declared a national emergency, closed all of its schools and is quarantining disease hot spots. [2014 Ebola Outbreak (Infographic)]

There are no treatments or vaccines available for Ebola, though several are in the pipeline. A study in Nature this year reported that one drug improved survival in monkeys who were exposed to a closely related virus, called Marburg virus. Public Health Canada is testing another antibody-based treatment and the company Tekmira Pharmaceuticals has developed an experimental drug that uses a process called RNA interference to block the virus' replication, Forbes reported.

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Antibody methods

As for the American health-care workers, one possibility is that Writebol was given a concentrated form of antibodies to the virus from someone who survived, Schaffner said. To make such a treatment, researchers would have to separate and concentrate the antibodies from a survivor's blood.

If Writebol did receive such an immune serum, it would almost certainly have to have been created at the site of the outbreak and have come from someone infected with the same strain of Ebola that she has, said Thomas Geisbert, a virologist at the University of Texas Medical Branch in Galveston, who has helped develop potential Ebola drugs. There are several species of Ebola virus; the current outbreak is caused by one called the Zaire species.

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Brantly is reportedly receiving a transfusion of whole blood from a 14-year-old patient who survived the disease.

In an Ebola infection, the virus first disables some of the immune system's frontline cells and then replicates almost unchecked. It then bursts out of cells throughout the body and damages them, eventually causing multi-organ failure.

Both experimental treatments, if they work, would need to lower the viral load by binding to the virus and preventing it from replicating, which would give the immune system enough time to regenerate its cells and fight the disease, Geisbert said.

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However, such treatments likely have limitations. In the last stages of the disease, in a process known as a cytokine storm, the immune system goes haywire and inflammatory molecules called cytokines attack the body's own tissue.

At that point, "if you're 24 to 72 hours from death and you've got a full blown case of Ebola hemorrhagic fever, there's probably nothing on the planet that's going to save you," Geisbert told Live Science.

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