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Survivors' Blood Holds Promise, But Draws Critics, As Ebola Treatment
As reported by The Los Angeles Times, the World Health Organization is endorsing blood transfusions from Ebola survivors as a treatment for those currently infected. The idea behind blood transfusion is similar to vaccination by other means, though (at least as discussed here) administered only after a patient has been infected: "The blood plasma of people who have recovered from Ebola contains antibodies that were successful in fighting off the virus. If these antibodies are pumped into an infected person, they might help the recipient fight the disease as well."
The article mentions that while there is little evidence to back the efficacy in preventing Ebola, "Transfusions were used to treat a small number of patients during the 1995 Kikwit Ebola outbreak in Zaire, now known as the Democratic Republic of Congo, according to Dr. Oyewale Tomori, a professor of virology at Redeemer's University in Nigeria. A study published in the Journal of Infectious Diseases after the outbreak reported that eight patients received transfusions, and only one of them died."
The idea of blood transfusions has critics, too: Dr. William Shaffner of Vanderbilt University is skeptical, saying he was surprised that the WHO would make transfusions a priority in the ongoing crisis because they are labor-intensive, making it difficult to serve a large number of patients. "You can't do this en masse," Schaffner said. "This is going to be a desperate attempt to provide something for a relatively small number of patients." Finding suitable donors may also prove more challenging than WHO officials expect, he warned. Malnutrition and other health concerns could make it more difficult to draw blood from people. "These are people who have recovered from Ebola," Schaffner said. "When are they hale and hearty enough to actually do a donation?"
The idea of blood transfusions has critics, too: Dr. William Shaffner of Vanderbilt University is skeptical, saying he was surprised that the WHO would make transfusions a priority in the ongoing crisis because they are labor-intensive, making it difficult to serve a large number of patients. "You can't do this en masse," Schaffner said. "This is going to be a desperate attempt to provide something for a relatively small number of patients." Finding suitable donors may also prove more challenging than WHO officials expect, he warned. Malnutrition and other health concerns could make it more difficult to draw blood from people. "These are people who have recovered from Ebola," Schaffner said. "When are they hale and hearty enough to actually do a donation?"
It has been done and quite successfully.
Couldn't this approach be used for any infectious disease for which there's no effective cure but there are some survivors? Are there just no Western diseases that fit the profile? I suppose you need both a person sick with a deadly infection and a recent survivor of a same infection (with the same blood type). So it may just be the case that we simply don't experience that scenario enough to develop this solution. But I'm curious if this approach has been used outside of Ebola in Africa.
It's not used much today, because we've largely conquered the disease agents that such an approach works against. Typically, it works well against infectious agents which are highly vulnerable to a Humoral (antibody-mediated) immune response. Co-incidentally, this also means most vaccines work extremely well against those same disease agents. Unfortunately, Ebola doesn't yet have a commercially available vaccine, but I would expect such a vaccine to work well.
There are only a few examples in the West where we still use this approach -- one that I can think of, is the use of anti-HepB sera in infants born to infected mothers, and for emergency prophylaxis of needlestick injuries involving Hepatitis B exposure. For the bulk of the population, Hepatitis B vaccination works well enough (and is far cheaper).
What it doesn't work well against, are infectious agents that don't respond well to natural antibody defenses. For instance, most anti-HIV antibodies do not defend well against HIV, anti-HepC antibodies do not protect against Hepatitis C, nor do anti-TB antibodies protect against Tuberculosis. For those agents, an effective response depends on cell-mediated immunity.
... give the patient more time to produce his own antibodies. ... the experimental treatment used on some western patients is basically antibodies.
Right on both counts.
- Much of why Ebola is so often fatal is that it produces a glycoprotein that interferes with immune system signaling, reducing and delaying the immune system's antibody-mediated specific responses. (Meanwhile the cell damage and foreign protein stimulate the GENERAL responses, which causes self-damage to the body and aids in spreading the infection.) Details on Wikipedia Keeping the virus population and the glycoprotien concentration down by supplying ready-to-go antibodies holds down cell death from infection, self-destruction, and signaliing interference, giving the immune system more time and ability to respond.
- The drug in question is a mix of three monoclonal antibodies, manufactured by stock genetic engineering techniques.
Injections of extracted antibodies, or blood containing them, has a long history in medicine. They have been used against bacteria, viruses, and poisons such as snake venom. Typically they are made by extracting a blood fraction containing antibodies from an animal which has been recently immunized - and is currently hyper-reactive to - the target disease agent or venom. (This gets a load of mixed antibodies which is heavy with those specific to the target.) They may also be extracted from a human survivor of a disease of interest, or a human in general. (These you might hear being called "human imune globin" or "gamma globulin".)
Downsides include allergic reactions to the animal used (typically a horse) or person providing the globulin, infection with blood-borne diseases (such as Hepatitis C), and reaction against the patient by some antibody in the serum.
Antiseura fell out of use for bacteria with the rise of antibiotics (even for diseases, such as menningitis, where antiseurm treatment had higher success rates). Antiviral drugs and the rise of a number of human viral diseases are pushing it down in preference for viral disease treatments - though better blood tests for viral infections is improving its safety. Nothing, of course, has replaced it for antivenom. It's still used for things like Hepatitis A, Measles, rabies exposure, supplement for certain immune difficiencies, and modulating immune system rejection of liver transplants.
With both the rise of antibiotic and antiviral drug resistance and the development of monoclonal antibody culture (prodcing just the desired antibodies to a target on an industrial scale, with negligible risk of dangerous contamination), expect more use of antiseura in medicine - like this "new experimental ebola drug".
Meanwhile, using antibodies extracted from ebola survivors - or transfusions if a matching donor is available - is the same system and might work just fine. And the technology is simple and cheap enough to be available even in third world countries.
Of course you need to wait until the survivor has recovered enough to have built up antibodies and enough blood to spare. Ideally you should also wait until the virus has cleared. (For instance, with Ebola, semen remains infective for at least two months, so blood likely does. as well.) But if the patient is already infected and likely to die without treatment, that's not an issue.
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It has been done during the 1995 Kikwit Ebola outbreak in Zaire. They tried it on eight patients and only one died. I have found no indication that any health care workers were infected.
Just in case anyone is curious, here is the actual paper: http://jid.oxfordjournals.org/...
Between 6 and 22 June 1995, 8 patients in Kikwit, Democratic Republic of the Congo, who met the case definition used in Kikwit for Ebola (EBO) hemorrhagic fever, were transfused with blood donated by 5 convalescent patients. The donated blood contained IgG EBO antibodies but no EBO antigen. EBO antigens were detected in all the transfusion recipients just before transfusion. The 8 transfused patients had clinical symptoms similar to those of other EBO patients seen during the epidemic. All were seriously ill with severe asthenia, 4 presented with hemorrhagic manifestations, and 2 became comatose as their disease progressed. Only 1 transfused patient (12.5%) died; this number is significantly lower than the overall case fatality rate (80%) for the EBO epidemic in Kikwit and than the rates for other EBO epidemics.