PROMISING EBOLA VACCINE DEVELOPED
An experimental vaccine to prevent Ebola virus disease was well-tolerated
and produced immune system responses in all 20 healthy adults who received it
in a Phase 1 clinical trial conducted by researchers from the National
Institutes of Health. The candidate vaccine, which was co-developed by the
NIH's National Institute of Allergy and Infectious Diseases (NIAID) and
GlaxoSmithKline (GSK), was tested at the NIH Clinical Center in Bethesda,
Maryland. The interim results are reported online in advance of print in the New England Journal of Medicine.
The unprecedented
scale of the current Ebola outbreak in West Africa has intensified efforts to
develop safe and effective vaccines, which may play a role in bringing this
epidemic to an end and undoubtedly will be critically important in preventing
future large outbreaks," said NIAID Director Anthony S. Fauci, M.D.
"Based on these positive results from the first human trial of this
candidate vaccine, we are continuing our accelerated plan for larger trials to
determine if the vaccine is efficacious in preventing Ebola infection."
The candidate
NIAID/GSK Ebola vaccine was developed collaboratively by scientists at the
NIAID Vaccine Research Center (VRC) and at Okairos, a biotechnology company
acquired by GSK. It contains segments of Ebola virus genetic material from two
virus species, Sudan and Zaire. The Ebola virus genetic material is delivered
by a carrier virus (chimpanzee-derived adenovirus 3 or cAd 3) that causes a common
cold in chimpanzees but causes no illness in humans. The candidate vaccine does
not contain Ebola virus and cannot cause Ebola virus disease.
The trial enrolled
volunteers between the ages of 18 and 50. Ten volunteers received an
intramuscular injection of vaccine at a lower dose and 10 received the same
vaccine at a higher dose. At two weeks and four weeks following vaccination,
the researchers tested the volunteers' blood to determine if anti-Ebola
antibodies were generated. All 20 volunteers developed such antibodies within
four weeks of receiving the vaccine. Antibody levels were higher in those who
received the higher dose vaccine.
The investigators also
analyzed the research participants' blood to learn whether the vaccine prompted
production of immune system cells called T cells. A recent study by VRC
scientist Nancy J. Sullivan, Ph.D., and colleagues showed that non-human
primates inoculated with the candidate NIAID/GSK vaccine developed both
antibody and T-cell responses, and that these were sufficient to protect
vaccinated animals from disease when they were later exposed to high levels of
Ebola virus.
The experimental
NIAID/GSK vaccine did induce a T-cell response in many of the volunteers,
including production of CD8 T cells, which may be an important part of immune
protection against Ebola viruses. Four weeks after vaccination, CD8 T cells
were detected in two volunteers who had received the lower dose vaccine and in
seven of those who had received the higher dose.
"We know from
previous studies in non-human primates that CD8 T cells played a crucial role
in protecting animals that had been vaccinated with this NIAID/GSK vaccine and
then exposed to otherwise lethal amounts of Ebola virus," said Julie E.
Ledgerwood, D.O., a VRC researcher and the trial's principal investigator.
"The size and quality of the CD8 T cell response we saw in this trial are
similar to that observed in non-human primates vaccinated with the candidate
vaccine."
There were no serious
adverse effects observed in any of the volunteers, although two people who
received the higher dose vaccine did develop a briefly lasting fever within a
day of vaccination.
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