HAMILTON – Researchers at the National Institute of Allergy and Infectious Disease’s Rocky Mountain Labs in Hamilton, working in conjunction with a team in Oregon, have made an important discovery related to a potential Ebola vaccine.
Dr. Heinz Feldmann, chief of the Laboratory of Virology at RML, and Andrea Marzi, a staff scientist who designed the research project, believe they have learned how an experimental Ebola vaccine protects against infection in nonhuman primates — monkeys — which is the best model for human Ebola disease.
Feldmann has a long history with Ebola. He started researching a vaccine more than 10 years ago while he was working in Canada, and the vaccine has been successfully tested on rodents and monkeys. However, one key question remained about why the vaccine was successful: Did the vaccine work because of the “killing action” of the immune cells or through antibodies that neutralize the virus?
The results of the study by Feldmann, Marzi and a team of researchers at Oregon Health and Science University found that the vaccine indeed elicits antibodies that can protect animals against Ebola infection. The scientists used another virus, vesicular stomatitis virus, to produce the sole surface proteins from Ebola after immunization so that the animals’ immune system can recognize the foreign protein and fight off the virus if they were ever infected.
The results were published recently in the prestigious journal Proceedings of the National Academy of Sciences.
Ebola causes severe hemorragic fever in humans, which includes profuse internal organ bleeding, and up to 90 percent of people who are infected die from shock, bleeding and multiple organ failure. There currently is no licensed treatment or vaccine for Ebola, which is why this study is so important for moving toward a clinical trial with humans.
In 2012, the World Health Organization reported Ebola hemorrhagic fever outbreaks in the Democratic Republic of Congo and Uganda, accounting for more than 100 cases (probable and confirmed) and numerous deaths. Feldmann said Ebola and its cousin Marburg are a huge concern for the scientific community and governments around the world because the potential for importation of infections and misuse of the virus would be challenging for any public health system.
The viruses originated in Africa and are believed to be transmitted to humans through bats. The scientists also have successfully tested the experimental vaccine against Marburg.
Feldmann said there is a lot of efficacy data, or success, in the nonhuman primate model to support the next step in testing the vaccine.
“We know it works very well, and we hope we can get into clinical trials,” he said. “We did not know why it worked. The body has two big weapons to fight viral infections. Cellular immunity means immune cells that kill incoming viruses, or antibodies that would neutralize the virus. The question was what is this vaccine mediating in an immunized host? Is it triggering one or the other or both? Andrea and the Portland team show very elegantly in their study that it is the antibody that is important.
“This has huge implications not only for this vaccine platform, but also for the field in general. The general thinking was that antibodies are not important for Ebola. Not every Ebola vaccine that has been tried might not work with the same mechanism, however.”
Feldmann said that the study also defined what scientists call a “correlate of protection.”
“We could go into humans and we know what kind of an antibody response we need to achieve in a human, so we can predict that the antibody is working should we have to use it in a human,” he explained. “We know what to test for should we go into humans. These are the two key findings.”