Thursday, September 24, 2015

Progress in Developing a Vaccine against the Ebola Virus

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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