Human Trials for Ebola Vaccine?

Nov 8, 2012 | Jason Hayes | Research & Policy

Recent Ebola outbreaks in the Democratic Republic of Congo and Uganda underscore a persistent challenge about the terrifying little virus: we don’t yet know how to prevent it. In fact, we only recently made steps towards curing it.

However, based on new research from Canada, the same scientists who identified antibodies that stopped Ebola infection in monkeys believe they have identified antibodies that may predict whether the immune system can overcome Ebola. The new discovery from Gary Kobinger and his team at the Public Health Agency of Canada means that scientists can assert if a vaccine for Ebola will work.

Quick refresher: Antibodies are proteins that the immune system produces when it detects the presence of pathogens. Each pathogen has a particular set of identifiers, called antigens, which trigger the release of specific antibodies. The immune system releases antibodies to identify and neutralize pathogens.

Until now, the serum that saved monkeys in the lab could not be tested on humans because it would require scientists to expose humans to one of the deadliest viruses in the world, without knowing if they could be saved.

For obvious ethical reasons, we need to be certain a vaccine is effective before human trials. No one would condone inoculating people with Ebola to test a vaccine without significant evidence of vaccine effectiveness. After all, there is a chance in each person, however small, that a vaccination may not produce antibodies or actually yield individual immunity.

Kobinger’s research provides reassurance. In a study published in Science, Kobinger compared animals with IgG levels – blood borne immune system triggers – of the antibody produced against potentially lethal inoculations of Zaire ebolavirus (ZEBOV). The findings confirm that this specific antibody can offer immunity. As a rule of thumb with other diseases, the antibodies Kobinger found provide correlates of protection, or expected immunity – with up to 99 percent accuracy. Not only can scientists now predict immunity but they can also confirm a vaccinated person will become immune, which is a step towards human trials.

The new antibodies, both those that constitute a cure and those that predict immunity, could not come at a more poignant time. ZEBOV, the strain tested in Kobinger’s study, can exhibit a case fatality rate as high as 90 percent. This month, the World Health Organization confirmed 25 deaths in the DR Congo from Ebola, which compounds the 15 deaths in Uganda. 

In the aftermath of these summer outbreaks, scientists in Canada provide hope that we may soon be able to test an Ebola vaccine on a person – the last step before getting it to the people who need it most.

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