Editors:Elham Reshid and Hailemariam Shimelis : Click for the PDF version
Ebola virus (EBOV) infections cause severe illness in humans. After an incubation period of 3 to 21 days, patients initially present with general flu-like symptoms before a rapid progression to advanced disease characterized by hemorrhage, multiple organ failure and a shock-like syndrome.
Without an approved vaccine or treatment, Ebola outbreak management has been limited to palliative care and barrier methods to prevent transmission. These approaches, however, have yet to end the 2014 out-break of Ebola after its prolonged presence in West Africa.
A study performed with an experimental Ebola drug called ZMapp previously given to two American aid workers (Brantly and Writebol) successfully cured a group of non-human primates infected with EBOV in laboratory tests. This product is a combination of three different monoclonal antibodies that bind to the protein of the Ebola virus.
This study showed ZMapp, optimized from two previous antibody cocktails, was able to rescue 100% of rhesus macaques when treatment is initiated up to 5 days post-challenge. High fever, viraemia and abnormalities in blood count and blood chemistry were evident in many animals be-fore ZMapp intervention.
Advanced disease, as indicated by elevated liver enzymes, mucosal haemorrhages and generalized petechia could be reversed, leading to full recovery.
Since the host antibody response is known to correlate with and is required for protection from EBOV infections monoclonal-antibody-based treatments are likely to form the centrepiece of any future therapeutic strategies for fighting EBOV outbreaks. However, whether ZMapp treated survivors can be susceptible to re-infection is unknown. In a previous study of murine ZMAb treated, EBOV-challenged NHP survivors, a re-challenge of these animals with the same virus at 10 and 13 weeks after initial challenge yielded 6 of 6 survivors and 4 of 6 survivors, respectively.
In light of the current outbreak of EBOV, a panel of ethicists specially appointed by the World Health Organization said that it is ethical to give untested treatments to people battling Ebola in the current out-break. ZMapp is the only experimental treatment that has been deployed against Ebola during this outbreak, but others could be on the way.
Xiangguo Qiu et.al. Reversion of advanced Ebola virus disease in non-human primates with ZMapp. http://www.nature.com/nature/journal/vnfv/ncurrent/full/nature13777.html