Nerves reveal clue to CJD

Nerves such as those in muscle in beef cattle may carry the infectious agent for bovine spongiform encephalopathy (BSE) - or "mad cow disease" long before the animals develop the symptoms, according to new research.

But the finding could also lead to the development of drugs able to stave off the human form of the disease, suggested Adriano Aguzzi, the respected scientist who led the work. "It's early days. We still don't know if we will find a drug to do the job but at least now we have a very distinct idea about what we are searching for," Professor Aguzzi said.

The development came in experiments at the University of Zurich where a team has uncovered an important step in the development of fatal illnesses like BSE and its human equivalent, Creutzfeldt-Jakob disease (CJD). More than 20 Britons have so far developed a form of CJD thought to be caused by eating BSE-infected food.

Both CJD, BSE and scrapie, found in sheep, are reckoned to be caused by the build-up of misshapen forms of a normal body protein called a prion. The infection is caused when one misshapen form of prion begins recruiting other copies in the body, which also become misshapen. In the brain, the effect is that the nerve cells die and leave spongy holes. At present, such diseases are incurable.

Today Professor Aguzzi reports in the journal Nature that prion "recruitment" occurs in the lymphatic system - explaining why such diseases can incubate for up to 30 years. In BSE and CJD, the infectious prions then need a "bridge" to cross to the central nervous system. Swiss scientists have speculated that that bridge could be part of the peripheral nervous system - so nerves and muscles could be a source of infective prions in dead BSE-infected animals. But Professor Aguzzi thinks the finding is more important.

"It gives us a possibility to stop the expression of the normal prion in these specific places, and this should effectively prevent the infective agent from reaching the brain," he said.