New Ebola drug *may* have saved lives of two Americans infected by Ebola virus

This is encouraging news from CNN on efforts to develop a drug against Ebola virus (EV):

"It's a story that could have come from a cinematic medical thriller: Two American missionary workers contract Ebola. Their situation is dire. Three vials containing a highly experimental drug are flown into Liberia in a last-ditch effort to save them. And the drug flown in last week appears to have worked, according to a source familiar with details of the treatment."

As I mentioned in my post on Sunday, one class of therapeutics are antibodies (or antisera) against Ebola virus (EV) produced by another organism (i.e. another person or animal) exposed to the virus, and then harvesting their blood or immune cells for antibodies against EV. These antibodies can be injected into an affected person and help neutralize the virus.

Note that a vaccine works differently by exposing your own body to a harmless version of the virus so that your own body makes anti-EV antibodies even before you get infected, thus helping to protect you against an infection.

The source of the anti-EV antibodies were mice generated by a small company called Mapp Biopharmaceuticals:

"The medicine is a three-mouse monoclonal antibody, meaning that mice were exposed to fragments of the Ebola virus and then the antibodies generated within the mice's blood were harvested to create the medicine. It works by preventing the virus from entering and infecting new cells."

More specifically, the mice were exposed to fragments of EV, and then the immune cells (from the spleen) that made antibodies against these fragments were isolated. These immune cells are essentially "factories" that produce anti-EV antibodies; they can be grown and cultured to manufacture large quantities of the neutralizing antibodies.

Here is a short blurb from Wikipedia on monoclonal antibodies and a schematic on how they are generated (Figure 1).

In pre-clinical tests, these monoclonal antibodies were able to protect monkeys 24 to 48 hours after infection. Now we may have data from humans (i.e. the two Americans) in which this treatment appears to have had a beneficial effect. This news warrants some cautious optimism and further investigation (i.e. trials).

Figure 1. How monoclonal antibodies are made. Spleen cells from mice exposed to an antigen (e.g. Ebola virus protein) are isolated and combined with myeloma cells to make "hybridomas" that produce antibodies and are capable of dividing in culture. These hybridomas are screened for cells that make antibodies against the desired target (e.g. EV protein). The positive hybridomas can be outgrown and used to manufacture large quantities of the desired antibodies.