A paper in the July 2005 issue of Nature Medicine reports the development of a vaccine that successfully protects non-human primates against Ebola and Marburg viruses, and is the first time a Marburg vaccination has been shown to work in a monkey model.
Ebola and Marburg viruses are emerging pathogens that cause hemorrhagic fever with high mortality rates in humans and non-human primates. Public concern about these viruses has recently increased owing to a large frequency of virus-related deaths in central Africa -- such as the current crisis in Angola -- and because these pathogens are considered to be potential bioterrorism agents, with no known cure.
Currently, there are no vaccines or therapies against Ebola or Marburg virus approved for human use. In the new study, Thomas Geisbert and Heinz Feldmann and colleagues developed vaccines against the two pathogens. The vaccines are based on a recombinant form of the vesicular stomatitis virus expressing either the Ebola or the Marburg virus surface protein. The vaccine is attenuated, meaning that the structure looks like rVSV, but triggers none of the symptoms associated with it, as the coding is contained within the surface protein which in this case has been replaced with either Ebola or Marburg surface protein.
The researchers found that a single injection of either vaccine in macaques produced completely protective immune responses when the corresponding virus was introduced into the macaques systems. Looking for the immune mechanisms that accounted for the protection, the authors found that the Ebola vaccine induced both cellular and antibody-mediated immune responses in all vaccinated monkeys. However, the antibody-mediated response induced by the Marburg vaccine was stronger than the corresponding cellular response. Finally, the scientists found no evidence of Ebola or Marburg viral replication in any of the vaccinated animals.
The data of this study indicate that these vaccine candidates are safe and highly effective in a relevant animal model, highlighting their real potential for use in humans.
Tom Geisbert (United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, USA)
Steve Jones, co-author (Canadian Science Center for Human and Animal Health, Winnipeg, Canada)
Also published online(C) Nature Medicine press release.
Message posted by: Trevor M. D'Souza