November 10, 2014 in Blog by jmeyer

By Dr. Joanne Elliott

According to the World Health Organization, almost 2300 people have died as a result of the current Ebola virus outbreak in West Africa, including 79 health workers. Moreover, it is estimated that approximately 4000 are infected in Guinea, Sierra Leone, Nigeria, Senegal and Libera. Although severe, Ebola hemorrhagic Fever is a relatively rare infection that can affect primates and humans. The incubation period of the virus can range form 2-21 days and symptoms of infection include high fever, bleeding and CNS damage.

Understanding the spread of Ebola is essential to curtail further transmission. Although bats are the natural virus host, it is thought humans become infected through contact with infected blood, meat or bodily fluids. The index case for the current Ebola outbreak has been linked to a woman in the Congo who ate an infected bush animal. Proven methods of infection control, protective clothing and new treatment centers are the current methods used to halt the spread of the virus while researchers are striving to develop a proven, effective treatment that can combat the Ebola epidemic.

Promising research by Stanley et al., published in Nature Medicine on September 7th, suggests a Ebola vaccine may be attainable. Using a Chimpanzee derived, replication deficient adenovirus modified to contain 2 Ebola virus gene segments, they could protect 4 out of 4 macaque monkeys exposed to Ebola 5 weeks after vaccination. However, only 2 out of the 4 monkeys where protected after subsequent challenge 10 months after vaccination. Rates of long-term protection where improved when a separate group of macaques were given a booster vaccine consisting of a recombinant poxvirus containing Ebola gene sequences. Currently, this vaccine has been fast-tracked for safety testing in healthy volunteers at the NIH in Bethesda and if positive, may become available for use in November.

ZMapp, developed by Mapp Biopharmaceutical based in San Diego, has also been proven to be effective in treating two US aid workers who contracted Ebola while caring for patients in Liberia. ZMapp is a combination of three mouse monoclonal antibodies that is thought to stop the virus from gaining entry into host cells. However, ZMapp has yet to be subjected to a randomized clinical trial and its limited supplies have been exhausted. An upsurge in Zmapp manufacturing has become and hopefully supplies will be become available over the next two months. Another potential therapeutic vaccine against Ebola, has been developed in collaboration with the Public Health Agency in Canada. The vaccine based on Vesicular Stomatitis Virus is a live virus containing Ebola proteins, which can stimulate the host immune response to offer protection. New Link Genetics, which has licensing rights for this vaccine, has given permission for the FDA to start trials in healthy volunteers this Fall.

Although, an effective Ebola vaccine is on the horizon, an immediate solution to the current epidemic suggested by the World Heath organization is to use blood therapies. Although controversial, individuals that have survived infection will have antibodies present in their serum to fight Ebola virus. With the current Ebola, outbreak having a mortality rate of 50%, there are a large number of survivors whose blood may be used to treat others. During the 1995 Ebola epidemic in the Congo, 7 out of 8 people who were given blood therapy survived. However, large-scale data is lacking and those who survived received better than average care and may have recovered without medical intervention. Using blood of patients who recover form Ebola to treat others may be both cost effective and potentially useful in the short term to limit the spread of the current Ebola outbreak. However, in the long-term it is hoped that a safe, effective and easily administered vaccine may become available to combat the current Ebola epidemic.