Synthetic vaccine may help tackle foot-and-mouth disease
Scientists have developed a synthetic vaccine that could be modified to tackle problematic forms of foot-and-mouth disease (FMD) in the developing world.
FMD is a highly contagious viral disease afflicting livestock that is endemic in many parts of Africa, the Middle East and Asia. Outbreaks can have devastating economic consequences; for example, a 1997 epidemic in Taiwan cost an estimated US$15 billion and led to the slaughter of 38 per cent of its pigs.
The current vaccine is made in costly bio-secure plants and needs to be kept refrigerated, therefore in the developing world it is only used in regions with easy access to the specialised facilities that produce it.
Now researchers working in the United Kingdom have for the first time created a safe, synthetic vaccine that works as well as the current vaccine and eliminates the risk of a live-virus outbreak.
- Current foot-and-mouth vaccines are ineffective against some variants of the disease
- Scientists are confident their synthetic vaccine can be modified to tackle these strains
- But any vaccine could be up to eight years away from use
They used X-ray crystallography and computer-aided design to develop detailed knowledge of the virus shell structure in order to mirror its shape, then modified it atom by atom to stabilise it.
The results, from a collaboration of researchers at The Pirbright Institute, Diamond Light Source and the Universities of Oxford and Reading, all in the United Kingdom, were published in PLOS Pathogens last month (27 March).
"The benefits of this new [vaccine] are that no live virus is involved, making it less expensive to produce and much safer, and the vaccine is so stable that it is less dependent on a cold chain," says Bryan Charleston, head of the Livestock Viral Diseases Programme at The Pirbright Institute and one of the study's lead researchers.
To test the vaccine, two groups of four cattle plus two non-vaccinated control animals were inoculated and followed for nine months. The vaccinated cattle were found to have high levels of antibodies against FMD indicating protection from infection. Further, larger animal trials are planned for Southern Africa and Europe.
More than one billion smallholder farmers depend on livestock for their livelihoods. In the developing world this disease particularly affects subsistence farmers with small herds spread across large areas.
"In these regions, vaccination programmes may not be effective, partly because it is difficult to deliver vaccines to rural areas because of problems maintaining a cold chain," says David Stuart, life science director at Diamond Light Source and the study's other lead researcher.
Stuart tells SciDev.Net that in Southern Africa a virus strain known as SAT2 is particularly unstable and no good vaccine candidate is available.
The team is collaborating with virologists in Southern Africa to modify their vaccine to treat this form. There are sufficient similarities between the virus strains to suggest that a similar technique can be used.
"If we can produce a significantly more stable vaccine, then this will be a major step forward in these regions," says Stuart.
Charleston adds: "We are working hard on ongoing pilot production studies with our commercial partner to make further improvements and ensure the technology can apply to all virus subtypes. So far, we don't envisage a major hurdle to taking this forward."
But he tells SciDev.Net that it may take up to eight years for global regulatory authorities to approve the vaccine's use by farmers.
Livio Heath, manager of the Transboundary Animal Disease Programme at the Agricultural Research Council-Onderstepoort Veterinary Institute, South Africa, says: "Application of the new vaccine in global efforts to control FMD is still some way off. However, the advantages over the current vaccine make it an attractive alternative in the fight against the disease."
PLOS Pathogens doi:10.1371/journal.ppat.1003255 (2013)