Foot-and-mouth advance heralds end of farmers' greatest horror

Revolutionary vaccine means mass culling of healthy animals is no longer necessary

Steve Connor@SteveAConnor
Wednesday 27 March 2013 23:00
Government workers incinerate the carcasses of livestock thought to be infected with foot and mouth disease in 2001
Government workers incinerate the carcasses of livestock thought to be infected with foot and mouth disease in 2001

Scientists have developed a new type of vaccine against foot and mouth disease that could radically change the way the government deals with future outbreaks as well as earning Britain a major slice of the £3.3bn annual market in the animal vaccine.

The last major outbreak of foot and mouth disease in 2001 cost the UK an estimated £8bn with more than 10 million cattle and sheep slaughtered as part of a national cull. Limited vaccination around the epicentre of any future outbreak could prove a viable alternative to mass culling of healthy animals.

The vaccine is based on a synthetic “shell” of the foot and mouth virus which was created by a unique combination of genetic engineering and high-powered microscopy using the Diamond Light Source in Oxfordshire, which produces X-rays that are 100 billion times brighter than hospital X-rays.

Conventional foot and mouth vaccines are made by growing thousands of litres of live virus in giant fermenters, which is an inherently dangerous and expensive process running the ever-present risk of accidental escapes into the environment.

The new vaccine uses genetically-engineered insect cells that make only the outer, non-infectious shell of the virus, which means that there is no risk of an accidental leak of live virus. The Diamond Light Source produced powerfully magnified 3-D images of the virus’s shell which allowed the scientists to ensure the vaccine was both stable and effective.

Tests show that the viral shells remain effective at high ambient temperatures, which means the vaccine may not require expensive refrigeration, even in tropical climates where the disease is endemic. Preliminary trials also show that the vaccine produces good immunity against foot and mouth when injected into animals.

“What we have achieved here is close to the holy grail of foot and mouth vaccines. Unlike the traditional vaccines, there is no chance that the empty shell vaccine could revert to an infectious form,” said Professor Dave Stuart, life science director at Diamond Light Source.

The technique, which has been patented, could revolutionise vaccine manufacturing, making it cheaper as well as safer, and might be applied to a range of other similar viruses, including some affecting humans such as poliovirus, Professor Stuart said.

“We were able to visualise something a billion times smaller than a pinhead and further enhance the design atom by atom of the empty shells. Through information gained at Diamond we also verified that these have essentially the same structure as native virus to ensure the appropriate immune response,” he said.

Bryan Charleston, of the Pirbright Institute in Surrey, who leads the team working on foot and mouth vaccine, said that a key factor in developing the new vaccine was to be able to see the 3-dimensional structure of the viral shell each time changes were made to the viral genes used to make the structure in cultured insect cells.

“We would simply not have been able to do this without Diamond because you need to know the structure otherwise you are literally floundering around in the dark,” Dr Charleston said.

The purity of the new vaccine, which is not contaminated with proteins from other parts of the virus, will help to distinguish between vaccinated cattle that have never been infected and cattle that have been infected but show no physical symptoms other than carrying antibodies in their blood. This distinction is critical for countries that use vaccines routinely and want to continue exporting to countries that are free of foot and mouth, Dr Charleston said.

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