Ebola vaccine developed to fight bioterrorism

An experimental vaccine against the lethal Ebola virus has been administered to humans for the first time in November 2003. If the trial proves successful, then the vaccine will be commercialised by 2006, a decade sooner than the time, it was thought, it would take to develop the inoculation. The potential to use the virus as a bioterrorism weapon is one of the major factors determining the speed at which the vaccine was developed. It can also be used as a preventive tool in countries where the virus is endemic

 
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By Vibha Varshney
Published: Wednesday 31 December 2003

-- (Credit: EMKAY)an experimental vaccine against the lethal Ebola virus has been administered to humans for the first time in November 2003. If the trial proves successful, then the vaccine will be commercialised by 2006, a decade sooner than the time, it was thought, it would take to develop the inoculation. The potential to use the virus as a bioterrorism weapon is one of the major factors determining the speed at which the vaccine was developed. It can also be used as a preventive tool in countries where the virus is endemic.

It is the first of two vaccines being developed by researchers from the us-based National Institutes of Health (nih). During tests on monkeys in 2000, it was found to be 100 per cent effective. The human trial would involve 27 volunteers. Six of them would be given a placebo. The rest will receive three injections during two stages of the treatment. In the first stage, the immune system will be 'primed' by the direct injection of non-infectious genetic material of the virus. The presence of the genetic material will initiate the production of antibodies against the virus on a large-scale.

During the second stage, the immune system's response will be 'boosted' with the help of the two other jabs, which contain the common cold-causing viruses genetically modified to incorporate the genetic material of the Ebola virus. The material is incorporated in the common cold viruses so that it can be replicated when they multiply. If the Ebola virus attacks the person in future, then his/her immune system will have a 'memory' of the virus; this will help in quickly producing the desired immunity. In an unvaccinated person, the production of antibodies would be slower than what is required.

The researchers claim that their vaccine is safe, as it does not contain any infectious material from the virus. However, there is a hitch -- the human body is accustomed to attacks by the common cold virus, and hence it may not produce the antibodies if the virus is injected several times. Two people have been given the vaccine to date. All the subjects will be followed up for one year. The researchers would collect blood samples to measure the type and duration of the immune system's response. The subjects would not be infected by the virus to gauge the effectiveness of the treatment as it is too risky to do so.

On November 14, 2003, the health ministry of the Republic of Congo, along with the World Health Organization, confirmed that the northwestern part of the country is facing an Ebola epidemic. The death toll so far is 28. More than 47 people are infected and another 97 are being followed up.
The researchers are also testing a single-dose vaccine that will take less time to confer immunity. This vaccine uses only the 'boost' part of the therapy, and hence the immunity provided by it is less than that of the first vaccine. It has been tested successfully in monkeys, who became immune to the Ebola haemorrhagic fever within 28 days. It is likely to enter human trials in 2004. "Both the vaccines have to be now tested for safety, duration of protection, and the mode of production on a large-scale," says D A Henderson, a biosafety expert from the us-based University of Pittsburgh.
Endless benefits The success of the vaccines is important to ensure protection against bioterrorism. The Ebola virus is considered to be the most potent weapon in the hands of of bioterrorists, as it is highly contagious and there is no treatment. It kills around 90 per cent of the infected people. Experts realised that Ebola could make a frightening weapon in the early 1990s. The anthrax attacks in 2001 also provided impetus to develop the vaccines. The simple genome of the virus made the task of the scientists easier.

But without the fear of bioterrorism, the inoculations would even be a far-fetched dream, as is the case with many other diseases that plague the developing world. Even though large sums of money have been invested in the development of vaccines against malaria, kala azar and aids, their success has been limited. The new vaccines will prove to be the much needed tool to combat the virus, especially for the most affected African countries. The disease is characterised by haemorrhagic fever, followed by diarrhoea, vomiting, stomach ache and ultimately death.

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