New Vaccine Against Ebola and Marburg Viruses is Effective in Nonhuman Primates
By Luciana Borio, M.D., June 14, 2005
Researchers from the University of Manitoba in Winnipeg, Canada have developed a live-attenuated recombinant vaccine against Ebola and Marburg viruses that has been found to be safe and effective in nonhuman primates. The vaccine is based on a live-attenuated vesicular stomatitis virus vector that expresses either the Ebola (subtype Zaire) or Marburg virus glycoprotein.
The researchers immunized 6 cynomolgus macaques with a single dose of the Ebola vaccine, and 6 cynomolgus macaques with a single dose of the Marburg vaccine, intramuscularly. None of the animals showed signs of illness, and none displayed vaccine vector shedding, indicating that the attenuated viral vector is not pathogenic to them.
On day 28, all animals were challenged with lethal doses of either Ebola virus or Marburg virus. All four animals that served as controls died: Two animals that had been immunized against Ebola and received a Marburg challenge died, and two animals immunized against Marburg that received an Ebola challenge died. All other animals remained healthy after lethal challenges of Ebola or Marburg viruses.
This new vaccine candidate has several apparent advantages when compared with previous Ebola vaccine candidates:
Animals were protected against lethal challenges of Ebola or Marburg after only one dose.
It employs a platform that has the potential to protect against one or more subtypes of Ebola virus and Marburg virus in a single vaccine.
The vector (vesicular stomatitis virus) is thought to be safe in humans, and preexisting immunity to it is thought to be negligible.
A previous experimental Ebola vaccine designed at the National Institutes of Health entered clinical trials in November 2003. It was the first vaccine to protect nonhuman primates from Ebola virus. However, this vaccine uses an adenovirus vector. Since 40-60% of the population has preexisting immunity to adenoviruses, there is a significant possibility that the vaccine would be ineffective in humans.
Given that there is no currently existing therapy for infection with Ebola or Marburg viruses, both of which are Category A agents and transmissible from person-to-person, this potentially safe and effective vaccine is good news.
For additional information see: Jones SM, Feldmann H, Stroher U, et al. Live attenuated recombinant vaccine protects nonhuman primates against Ebola and Marburg viruses. Nat Med. Jun 5 2005.