Scientists at University of Wisconsin-Madison have successfully tested an Ebola vaccine in primates and so far it is proving to be effective and safe. The vaccine itself is constructed using a novel experimental platform and is different from other Ebola vaccines because it primes the host immune system with the full complement of Ebola viral proteins and genes, potentially conferring greater protection.
As Ebola is often fatal virus, one of the main priorities in this study was safety. Researchers were aiming not only to make a safe vaccine, but also to make environment safe for scientists to work with the virus. The vaccine was constructed on an experimental platform first devised in 2008. Key to safety is in the deletion of a key gene known as VP30, which the Ebola virus uses to make a protein required for it to reproduce in host cells.
Scientists engineered monkey kidney cells to express the VP30 protein so that the virus could be safely studied in the lab and be used as a basis for devising countermeasures like a whole virus vaccine. The studies were conducted with cynomolgus macaques, which are very susceptible to Ebola and, according to scientists, are the best models. However, several vaccine platforms are being developed for years, four of which already reached the stage when they are being tested with humans. But scientists say that this new platform has some advantages.
Ebola vaccines currently in trials with humans include: a DNA-based plasmid vaccine and three vaccines engineered to express a key Ebola protein – vaccine based on a replication incompetent chimpanzee respiratory virus, a live attenuated virus from the same family of viruses that causes rabies and a vaccine based on a vaccinia virus. However, new vaccine is the first one that could be called a whole virus vaccine.
Main advantage of a whole virus vaccine is that it presents the complete range of proteins and genetic material to the host immune system, which is then more likely to trigger a broader and more robust immune response. Such vaccines are used to prevent polio, influenza, hepatitis, human papillomavirus-mediated cervical cancer and other serious human diseases.
It was not a first attempt at creating a whole Ebola virus vaccine. But early attempts to devise an inactivated whole virus Ebola vaccine through irradiation and the preservative formalin failed to protect monkeys exposed to the Ebola virus and were abandoned. Even now, when such vaccine is proving to be successful, scientists will have to wait until human trials are possible. Human trials are expensive and complex, costing millions of dollars.
Ebola has been known since 1976, the current outbreak in West Africa has so far claimed more than 10,000 lives. That is why scientists are rushing to prepare effective and safe vaccine for future outbreaks. Ebola virus has only eight genes and, like most viruses, depends on the molecular machinery of host cells to grow and become infectious. Therefore, new vaccines, using innovative platforms are quite possibly going to solve this problem in the near future.