Thursday, August 22, 2013

Possible therapy for people with Ebola Virus Disease

A map of historical outbreaks of  Ebola Virus 
Disease. A related virus also escaped  in Reston, 
Virginia (U.S.A.) but did not infect humans. 

Ebola Virus Disease is an often fatal hemorrhagic fever, triggered in humans and other primates by a small set of closely related viruses. This family comprises some of the most virulent infectious agents known, causing fatality rates as high as 90 percent. Thus far, this disease has only hit humans in small, but devastating, localized outbreaks. However, because of its high transmissibility, the scarcity of diagnostic tests, and the ceaseless motion of modern travelers, these viruses could conceivably trigger much larger, even international, pandemics. Finally, in addition to being a public health concern, the viruses of this family are also considered potential biological weapons.

Historically, there has been no cure for Ebola Virus Disease, and public health efforts were limited to isolating patients to prevent further transmission. But now scientists at the United States Institute for Infectious Diseases (USIID) and collaborators have announced a possible therapy for people with Ebola Virus Disease. The therapy agent, called MB-003, is a mixture of three monoclonal antibodies, each of which can bind to proteins expressed by Ebola virus. In an earlier paper, these scientists had found that MB-003 could protect rhesus macaques from the virus when the cocktail was administered 1 h postinfection,  and even  obtained significant protection if  treatment began 24 or 48 h postinfection. But new work published in Science Translational Medicine the authors extended these studies in a really exciting way.  This time, they waited until infected animals showed symptoms of disease, suggesting that the infection was already rampaging. This situation more closely resembles what a doctor would confront especially in a rural clinic,  i.e. the patient would not come in until the illness were already manifest.

The approach used to fight Ebola, a mixture of monoclonal antibodies,  is a modern take on an old therapy known as passive immunization or serum therapy. Long before the modern pharmaceutical era, doctors had realized that blood serum isolated from survivors of a disease would be very effective if given to patients suffering from the same disease. This is because the blood of the recovered patient would have lots of antibodies against that disease agent. Of course, blood will have antibodies against all sorts of other things, and the toxicity was a big reason this type of therapy was largely abandoned in favor of pharmaceuticals. Monoclonal cocktails may have fewer toxic side effects than whole blood serum therapies, and might even be used as immunizations in the future. 

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