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 "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" to companies developing RNA-based
therapeutics.
That could impact treatments under way from Vancouver-based Tekmira
Pharmaceuticals Corp and privately held Profectus BioSciences of
Tarrytown, New York.
Part of what makes the data useful is the precise picture it paints
as the epidemic unfolded. Sabeti credits years of work by her lab,
colleagues at Tulane and the Sierra Leone Ministry of Health and
Sanitation in developing a response network for Lassa fever, a virus
similar to Ebola that is endemic in West Africa.
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Several of the study authors gave their lives to the work, including
Dr Sheik Humarr Khan, the beloved "hero" doctor from the Kenema
Government Hospital, who died from Ebola.
The team had been doing surveillance for two months when the first
case of Ebola arrived from Guinea on May 25. That case involved a "sowei"
or tribal healer, whose claim of a cure lured sick Ebola victims
from nearby Guinea.
"When she contracted Ebola and died, there were a lot of people who
came to her funeral," Garry said. One of these was a young pregnant
woman who became infected and traveled to Kenema Government
Hospital, where she was diagnosed with Ebola.
With the Lassa surveillance team in place, they quickly began
testing samples.
"We've been able to capture the initial spread from that one person
and to follow all of these contacts and everything with sequencing,"
Garry said.
The team used a technique called deep sequencing in which sequences
are done repeatedly to generate highly specific results, allowing
them to see not only how the virus is mutating from person to
person, but how it is mutating in cells within the same person.
What is not clear from the study is whether the mutations are
fueling the epidemic by allowing the virus to grow better in people
and become easier to spread. That will require further tests in the
lab, Garry said.
(Editing by Matthew Lewis)
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