Antibodies
derived from an ebola survivor to cure seriously-ill patients. This is what US Dr James Crow, from the Vanderbildt University tries to achieve together
with pharmaceutical company Mapp. This is the producer of the experimental
ebola drug ZMapp, consisting
of a cocktail of three antibodies originating from mice. Human derived antibodies could be better in beating
the virus
From DNA to antibody
Dr. Rick Sacra, an US physician who contracted the
virus while working in Liberia, donated blood. The scientists are searching
after his antibody-producing white blood cells, the B-cells. James Crow selects the cells that produce
antibodies to ebola and clones the genes encoding those antibodies The DNA supplies the researchers with an
endless source for antibody production. It can be stored for ages and
multiplied in bacteria, a rather simple step. To go from DNA to antibody Mapp receives
help from the Amgen company. Mapp, who produce their own
antibodies in tobacco plants, will make large quantities of the human
antibodies in mammalian cells. To do so, the antibody-DNA is transferred into those cells, which read the
code and translate that to large amounts of antibodies. This takes place in bioreactors.
What follows is a long way of testing. Are these antibodies capable of neutralizing
ebola? This is first tested in the lab, later in animals. The new drug is
clearly not ready-to-use tomorrow.
Cloning
antibodies from patients is a well-known method. But why should you clone them, why not purify
them directly from the blood? That is because large volumes of patient blood are
needed to purify sufficient amounts of antibodies. During the height of the epidemic
many patients have high titers of anti-ebola antibodies. But when the disease
fades out, the titers drop. Complicating factor is that many patients are
infected with other viruses or parasites, like HIV. You don’t want that
in your medication vial.
Purified from blood
Nevertheless,
this is frequently done. Think of tetanus. For this disease in the Netherlands
volunteer donors are frequently vaccinated to maintain high titers. The antibodies
are purified from their blood to cure patients who have contacted this serious
disease. The same goes for anti-rhesus-D injections. Antibodies to rhesus D are
purified from blood of women who in the past had made antibodies to their babies.
Next, patients with immune deficiencies receive antibodies
purified from plasma of thousands of blood bank donors. They get the entire
spectrum, so to defeat all general occurring infections.
The
question remains whether Sacra survived thanks to his effective antibodies or
whether the supporting treatment in an US hospital was crucial.
Source: http://www.reuters.com/article/2014/12/22/us-health-ebola-usa-antibodies-exclusive-idUSKBN0K00VA20141222
