The internet and television news agencies are awash with chatter about the "secret" Z-Mapp serum that was administered to the two Americans currently fighting to survive infections with the deadly Ebola virus. There are claims that the serum caused an almost miraculous upturn in the health of both patients who had started to deteriorate severely. However, this notion of a “secret” serum is misleading and may also stoke false belief that this treatment is some mystical tonic that has amazing powers to reverse the symptoms of Ebola and cure the patient.
In reality, there is nothing secret or mysterious about Z-Mapp. Mapp Biopharmaceuticals, the company that manufactures the serum has published research articles on the early result of testing carried out on primates and the development design of the serum. The premise of the serum is based on the same premise as that of an anti-toxin for a disease such as Botulism, or the antivenom that's given to a person who has been bitten by a poisonous snake. This approach is called a "Passive Immunity" treatment regimen. This means that if there is any real benefit from using the drug it is based on antibodies produced by a source other than the person who is infected. In the case of Z-Mapp the antibodies that may provide temporary protection from the virus is produced in tobacco plants.
How Does Passive Immunity Work?
Usually the body’s immune response takes a few days or weeks to mount a strong defense against a potential toxin or pathogen when a person has no prior exposure to that toxin or pathogen. In the case of a poisonous snake bite or Botulism the toxins released into the body would kill the patient before the body has time to fight it off and produce a “natural active immunity” response. Therefore, an antidote or antibody serum is administered as soon as possible to reverse detrimental effects of the venom or toxin. If administered quickly enough there is a better chance of saving the patient’s life.
ZMapp’s Passive Immunity Protection
Dr. Brantly and Nurse Writebol were given doses of the serum that appear to have had a beneficial effect shortly after being administered. However, unlike a scenario where a person receives a serum with antibodies against a snake bite, or Botulism, the complications for these two Ebola patients may revolve around how efficiently the virus infects cells and remaining active in the body. Ebola reproduces by infecting cells inside the body of the patient and then replicating inside of those cells. Once the virus replicates it doesn’t destroy the initially infected cells but releases thousands of viral particles, or virions, by a process called “budding”. Each single virion can then infect more cells in the person’s body and quickly overwhelm the person’s immune system.
The Z-Mapp serum would potentially work by binding to the virions as they are released from the already infected cells, and preventing them from infecting more cells. However, the serum is not stable indefinitely and if the virus can continue to replicate and release more virions it will outlast the beneficial effects of the serum if the person’s immune system doesn’t begin to successfully fight the infection. This would be the equivalent of treating a person for a deadly snake bite but allowing the snake to continue biting the person after the initial treatment. Unless the person is given more antivenom the patient would most likely die because their body would not be able to produce the antivenom naturally and quickly enough to survive. It’s interesting to note that Nancy Writebol is now being given a third dose of the Z-Mapp serum in an effort to provide more passive protection against the virus until her own immune system has a better chance of hopefully producing enough anti-Ebola antibodies to eliminate the virus naturally.
ZMapp’s Promise As An Ebola Cure?
While a drug like Z-Mapp may provide short-term benefits to a person infected with Ebola, just as an antidote for a deadly snake bite provides short term relief, only time and more research will be able to determine if Z-Mapp would be a true “cure” for Ebola. In addition, as the early primate studies by the developer of ZMapp have shown, the sooner you administer the drug, the better the prognosis. This is similar to what happens if a person is given an antivenom serum quickly versus hours after a snake bite or contracting Botulism. Therefore, it is extremely important for the scientific and medical community to continue to work quickly to find a preventative vaccine for Ebola, or to find a treatment that will have a protracted beneficial impact on a person who is infected with Ebola.