... 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.