How scientists are targeting Ebola
Souped-up antibodies against the virus are designed to strike with atomic precision, Viviane Richter reports.
The average human immune system is no match for Ebola. In West Africa, the WHO estimates 70% of people lose their fight within a few weeks of infection.
So far the best weapon we have is a precious supply of ZMapp, a cocktail of antibodies that targets the virus. But as in any arms race, these antibodies will need constant upgrading. In the latest issue of Scientific Reports, Xiangguo Qiu and colleagues at the Canadian Public Health Agency describe what is needed to stay one step ahead of the virus.
“Even though ZMapp is effective for now, the virus evolves. This research shows that we need to develop the next treatments,” says Grant Hill-Cawthorne, an epidemiologist at the Sydney School of Public Health.
To stop a virus from infecting us in the first place, we use vaccines. But they don’t work if a person is already infected. In that case lives can be saved through “passive immunisation” – injecting ready-made antibodies that block the virus from spreading further. ZMapp is a collection of ready-made antibodies produced by genetically engineered tobacco plants. Developing it took a collaboration between three companies (California-based Mapp Pharmaceuticals, its commercial arm LeafBio, and Canadian company Defyrus), the US government and the Public Health Agency of Canada. In a small trial ZMapp cured 100% of infected rhesus monkeys. Two infected American aid workers survived after receiving it, provoking a mass outcry to make it available to infected West Africans.
Although there have been no controlled trials in humans, given the desperate situation, the WHO approved ZMapp’s use in people in August. But the stocks are now exhausted. One challenge is ramping up large-scale production. Another is updating the antibodies as the virus mutates.
Antibodies home in on a specific target. In the case of ZMapp, the target is the single “glycoprotein” that sprouts all over Ebola’s surface. The problem is the virus keeps disguising the target.