There are no proven treatments or vaccines for Ebola virus. At present, four vaccine platforms have reached the clinical trial stage in humans.
The vaccine, detailed in the journal Science, was developed using a novel experimental platform at the University of Wisconsin-Madison that allowed the researchers to safely study the virus in laboratory conditions.
"In terms of efficacy, this affords excellent protection," says Prof. Yoshihiro Kawaoka, a professor of pathobiological sciences at the University of Wisconsin-Madison School of Veterinary Medicine. "It is also a very safe vaccine."
Whole virus vaccines have been used in the past to prevent other serious diseases, including hepatitis, human papillomavirus-mediated cervical cancer, influenza and polio. Using inactivated whole viruses provides the immune system with the complete range of viral proteins and genes, improving the likelihood of the virus triggering a strong immune response.
Earlier attempts to develop an inactivated whole Ebola virus vaccine, using irradiation and the preservative formalin, were ultimately unsuccessful and failed to protect monkeys from the virus. As a result, these attempts were abandoned.
Developing a new experimental platform from which to work with the virus has helped these researchers to be successful this time round. Devised in 2008, the new system enabled the team to work safely with Ebola virus by deleting a key gene called VP30 which allows the virus to make a protein required for it to reproduce.
Ebola virus only consists of eight genes and relies heavily on the molecular mechanics of host cells to proliferate around the body.
Using monkey kidney cells engineered by the researchers to express VP30, the team could safely use the virus as a starting point for the development of treatment for it. The whole virus vaccine devised by Kawaoka and his team was also chemically inactivated with hydrogen peroxide.
The vaccine has been tested successfully with macaques
Although the vaccine has not been tested in humans, successful tests have been conducted with cynomolgus macaques - considered to be the "gold standard" in testing vaccines in a model comparable to virus transmission among humans. "It's the best model," Kawaoka states. "If you get protection with this model, it's working."
The tests were conducted at the National Institutes of Health (NIH) Rocky Mountain Laboratories, a facility in Hamilton, MT, in collaboration with another group led by Heinz Feldmann of NIH. The laboratories are biosafety level 4 - the highest level of biological safety, designed for the study of dangerous and exotic microbes.
A number of other vaccines for Ebola virus are currently being trialled. These include:
- A DNA-based plasmid vaccine
- A live attenuated virus from the family of viruses that causes rabies
- A vaccine based on a replication incompetent chimpanzee respiratory virus
- A vaccine based on a vaccinia virus.
Each of these vaccines works to express or prime host cells with crucial Ebola proteins. However, Kawaoka believes that each of these different vaccines has shortcomings regarding their safety and method of delivery. The new whole virus vaccine will hopefully be unaffected by these limitations.
While the researchers have overcome the problems experienced by previous attempts at developing a whole virus vaccine, it will still be some time before the vaccine is ready to be rolled out. Human trials need to be conducted, and these are both complex and highly expensive.
Vaccinating humans is not the only goal for Ebola virus researchers. Recently, Medical News Today reported on a group of scientists who have developed a new vaccine that could potentially be used to reduce infection from the virus among wild African ape populations.