Progress in Developing a Vaccine against the Ebola Virus
The recent spread of hemorrhagic fever (EHF) in areas of West
Africa including Guinea, Sierra Leone and Liberia has placed considerable
urgency on the need to develop an effective vaccine against the pathogen
responsible for this horrific and highly contagious disease, the Ebola virus
(EBOV). To date, of the approximately
27,200 reported cases, there have been more than 11,100 deaths – a mortality rate
of 40.8 percent. EBOV
is so infectious that a high incidence rate has also been reported among health
care workers. It needs to be kept in
mind that the health care infrastructure of the countries affected has been
severely compromised especially since these so-called, “low resource” countries
have budgets inadequate to respond effectively to this challenge.
By way of background EBOV belongs to a class of viruses
called filoviruses. Filoviruses are single-stranded RNA
viruses. This class of viruses possesses
a glycoprotein (GP) on its surface that could conceivably make a good candidate
as an immunogen – a protein capable of eliciting an immune response.
Dr. Andrea Marzi at the Laboratory of Virology, Division of
Intramural Research at the National Institute of Allergy and Infectious Diseases at the National Institutes of Health in
Hamilton Montana.and his colleagues have
helped develop a strategy for developing such a vaccine. The strategy they employed can be outlined in
the following way –
- A live attenuated stomatitis virus was employed as a viral vector
- Recombinant technology was employed to modify this virus so that it expresses the Ebola GP on its surface referred to as Viral Stomatitis Vector EBOV (VSV-EBOV)
- This viral vector was then introduced into experimental animals – the rodent and macaque.
This approach was shown to be highly efficacious in both pre
and post exposure vaccinations. These
results were so promising that phase 1 clinical trials in humans were begun in several worldwide locations.
The following is in the author’s own words – “Complete and
partial protection was achieved with a single dose given as late as 7 and 3
days before challenge, respectively.
This indicates that VSV-EBOV may protect humans against EBOV infections
in West Africa with relatively short time to immunity, promoting its use for
immediate public health responses.”
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