Genetic studies of some of the earliest Ebola cases in Sierra Leone reveal more than 300 genetic changes in the virus as it leapt from person to person, changes that could blunt the effectiveness of diagnostic tests and experimental treatments now in development, researchers said on Thursday.
"We found the virus is doing what viruses do. It's mutating," said Pardis Sabeti of Harvard University and the Broad Institute, who led the massive study of samples from 78 people in Sierra Leone, all of whose infections could be traced to a faith healer whose claims of a cure attracted Ebola patients from Guinea, where the virus first took hold.
The findings, published in Science, suggest the virus is mutating quickly and in ways that could affect current diagnostics and future vaccines and treatments, such as GlaxoSmithKline's Ebola vaccine, which was just fast-tracked to begin clinical trials, or the antibody drug ZMapp, being developed by California biotech Mapp Biopharmaceutical.
The findings come as the World Health Organization said that the epidemic could infect more than 20,000 people and spread to more countries. A WHO representative could not immediately be reached for comment on the latest genetic study.
Study coauthor Robert Garry of Tulane University said the virus is mutating at twice the rate in people as it was in animal hosts, such as fruit bats.
Garry said the study has shown changes in the glycoprotein, the surface protein that binds the virus to human cells, allowing it to start replicating in its human host. "It's also what your immune system will recognize," he said.
In an unusual step, the researchers posted the sequences online as soon as they became available, giving other researchers early access to the data.
Erica Ollmann Saphire of the Scripps Research Institute in La Jolla, California, has already checked the data to see if it impacts the three antibodies in ZMapp, a drug in short supply that has been tried on several individuals, including the two U.S. missionaries who contracted Ebola in Sierra Leone and who have since recovered.
"It appears that they do not (affect ZMapp)," said Saphire, who directs a consortium to develop antibody treatments for Ebola and related viruses. But she said the data "will be critical to seeing if any of the other antibodies in our pool could be affected."
Saphire said the speed with which Sabeti and colleagues mapped genetic changes in the virus gives researchers information that "will also be critical"