It’s reported in the press that a health care worker, recently diagnosed with Ebola, is being offered plasma treatment in a London hospital. This involves a transfusion of plasma from patients who have recovered from Ebola.
Plasma (blood with the cells removed) is a rich broth, full of antibodies and other immune proteins. The treatment should perhaps be re-named “antibody transfusion”.
When there's a new, unfamiliar infection the adaptive division of the immune system takes a while to set up a production line for the appropriate antibodies. First, a wandering immune cell detects the presence of a virus or bacterium and carries it to a lymph node where it's examined by passing lymphocytes. If a lymphocyte identifies it as a new threat it settles down in the lymph node, cloning a huge number of identical self-copies. These are then released (into the plasma) with the capacity to flood the body with millions of copies of the newly minted antibody. It is this lymphocyte-cloning process that takes several days.
The danger is, that in a disease like Ebola, a patient could die before their own antibodies can be produced in sufficient quantities to eliminate the virus. An infusion of antibodies from a recovered patient has the potential to keep them alive until their own production gets up to speed.
From the late 1890s plasma has been used to treat infections. Often the donor was a horse, which had been inoculated with a virus or bacterium causing it to form ample quantities of the antibody. The technique saved many lives but had its disadvantages – the need to keep large stables of horses and the risk of developing immune reactions to equine plasma proteins to name but two. The practice declined rapidly with the discovery of antibiotics and other modern drugs.
Plasma donated by human Ebola survivors has proved useful in previous outbreaks and is probably the best treatment currently available. As with any type of blood transfusion donors should be screened for viruses such as HIV. WHO has recently issued guidelines.
I’m sure we all hope that in this current UK case it will prove successful.