A View from Conor Myhrvold
Monoclonal Antibody Treatment Shows Promise for Curing Ebola
The virus is tamed in macaques.
A new kind of antibody treatment has eliminated Ebola in several monkeys, yielding promise for a forthcoming vaccine.
No cure currently exists for Ebola, and conventional treatments need to be administered within an hour of infection, a somewhat impractical solution given that symptoms may only appear after several days.
Researchers from the Public Health Agency of Canada and the University of Manitoba used a more effective and expensive technique to get antibodies cloned from a single cell line, producing what are called monoclonal antibodies.
Making a vaccine traditionally involves using a grab bag of different antibodies. But these antibodies can bind to undesirable targets and produce other side effects.
With the new approach, individual immune cells (often a single B cell of a bunny rabbit) are isolated and then cultured using standard techniques to produce antibodies that are perfect replications of the “parent” cell.
Each monoclonal antibody is selected to bind to a specific target; in this case, the Ebola virus. These antibodies are then tested to see which ones work best, and the up to thousands of choices are narrowed to just a few (in the Ebola case, three.)
Because of the immune response detected in the surviving monkeys through antibodies and T cells, the Canadian scientists hypothesize that each round of monoclonal antibodies slowed down the replication of Ebola in the host. This bought enough time for the immune system to respond.
In the study, two groups of four crab-eating macaques were injected with Ebola then given the antibody treatment. An additional unlucky monkey served as a control for the other two groups, and was injected without treatment.
The three antibody mixture, named ZMAb, was given in succession, three times at three day intervals. It cured all four Ebola-infected macaques when first administered a day after infection and saved two of four when administered two days afterward.
Ebola’s high mortality rate and short time incubation period in humans, as well as non-human primates, means that it has been too successful too soon to cause a global pandemic, but some still worry that the disease could be used as part of a biological weapon. Although Ebola is not nearly as contagious as the common cold it can nevertheless be contracted via virtually any bodily fluid.
The study was published on June 13th in Science TranslationalMedicine, and is part of a drug trial to approve an Ebola vaccine.