A study of Ebola survivors in west Africa has found a group of women who appear to be immune to the deadly virus. The discovery was made by a team of British and European scientists who are studying Ebola survivors in Guinea.
“These are phenomenal women who have had a horrendous story to tell. They have had lots of contact with the virus, clearing up vomit, diarrhoea, sleeping with children with Ebola overnight, and they never presented with Ebola symptoms and somehow they have an immune response to the virus,” said Prof Miles Carroll, a virologist and head of research at Public Health England’s national infection service.
Early data from the research also offers a theory as to why survivors have not contracted Ebola for a second time even when the virus lingers in places such as the testes, spinal cord and eye chamber. London hospital says nurse is being treated for Ebola in isolation unit, in case that raises concerns for survivors elsewhere, The research bodes well for the 16,000 survivors in Sierra Leone, Liberia and Guinea, although British nurse Pauline Cafferkey has shocked experts by suffering complications from an earlier Ebola infection.
The most eye-catching finding in the research came from the parallel study of women who failed to show symptoms of Ebola even though they had been in direct contact with people who had died of the illness. The team studied 60 women, 25 of whom were in Guéckédou, the town where the most recent Ebola epidemic in west Africa is believed to have started. Blood tests showed one woman in this subset had Ebola antibodies even though she had never contracted the virus.
“We tested her blood eight months later in May 2015 and she had a phenomenally strong neutralising antibody response to Ebola,” said Carroll.
“It may be that these people are genetically unique and have an innate response strong enough to fight Ebola before it can get a foothold,” said Carroll. The findings suggest there are people who are exposed to the virus but never become infected.
Before the epidemic, it was widely assumed that Ebola survivors would have lifetime immunity to the virus but there was limited scientific evidence to prove this. Virus can be sexually transmitted months after original infection has disappeared, according to new study. Carroll’s project, which is ongoing and not yet published in a scientific journal, will test the theory that survivors develop long-term immunity because, for a limited time, the virus lingers in parts of the body the immune system cannot reach. He believes that when it leaches back into the blood it re-stimulates the immune response. His team found that the immune response in survivors is approximately 10 times stronger in survivors than in those who received a vaccine being tested in Guinea and the strength of the immune response did not appear to diminish over the year they studied the individuals.
With EU funding, Carroll and his collaborator, German scientist Prof Stephan Günther, started looking at blood and semen samples from Ebola survivors in Guinea from 2014. They discovered, as others have, that the virus continued to be present in the semen, but not in the blood of approximately one third of their sample.
“What is likely to be happening is the virus is lingering around these immune-privileged sites like the gonads and the spinal cord but continually leaching into the body, but the survivor never experiences symptoms because it is instantly soaked up by antibodies and T cells [part of the body’s immune response],” said Carroll.
He said the team found “really strong neutralising antibody response” that was 10 times higher than the response in those who had taken part in a vaccination program.“The naturally acquired immunity is exceptionally strong,” he said.