CJD test closer

Cattle carcasses must be stripped of dangerous tissues

By BBC News Online's Helen Briggs

Swiss scientists are on the brink of developing a diagnostic test for variant CJD and its cattle equivalent, BSE.

The test could one day be used to detect whether a patient or an animal is infected with a transmissible spongiform encephalopathy, before they show clinical symptoms.

This selective binding property could serve as the basis for a diagnostic test aimed at differentiating and diagnosing BSE or CJD

Swiss research team

The technology might also be used to screen human blood donations for the abnormal rogue proteins, or prions, that cause such diseases. There is a theoretical risk that humans with undiagnosed vCJD could transmit the infection through blood transfusions or products made from human blood. However, no cases have actually been recorded.

The Swiss method is based on a natural substance found in blood that is able to bind to the infectious agents.

The work, published in the scientific journal Nature, may also give an insight into how prions cause disease.

vCJD and BSE

The prions responsible for vCJD are thought to linger in human tissue and blood for many years before any symptoms of the disease begin to emerge.

These symptoms include unsteadiness on the feet, insomnia, memory loss and dementia. There is no cure.

The only way of confirming a vCJD case in humans is following death, in a post mortem examination.

But scientists are working on developing diagnostic tests that would detect the disease in its early stages.

The Swiss research is based on a natural blood substance called plasminogen. The scientists have discovered that the sticky protein binds to abnormal rogue prions.

Magnetic beads

Tiny magnetic beads coated with the sticky substance were able to fish-out rogue prions from samples of infected animal brain tissue. Similar, normal proteins found in the body did not bind to the beads.

The team, led by Dr Adriano Aguzzi, said: "This selective binding property could serve as the basis for a diagnostic test aimed at differentiating and diagnosing BSE or CJD. Further, it is conceivable that this interaction might be used to remove prions from blood products."

However, they stress that more work needs to be done before a reliable diagnostic test can be developed.

They added: "Before this discovery can be translated into a diagnostic test, the binding must be characterised in more detail."

Other experts say the new research is an important step up in knowledge. Dr Stephen Dealer, a consultant microbiologist and BSE researcher, said: "This is an exciting development that may eventually lead to a blood test for CJD.

"But we must find methods to look for the exceptionally small amounts of the rogue prions that are found in the white blood cells. We expect to have a technique that can be shown to work within a year, based on this and other research."