Source: UC Davis School of Veterinary Medicine

Researchers investigating brain diseases known as transmissible spongiform encephalopathies, which are thought to be caused by mutant versions of so-called prion proteins, have discovered a key distinction between normal prion proteins and their rogue counterparts. The discovery, described in the November 23 issue of the journal Nature, may shed light on how prion diseases like bovine spongiform encephalitis (BSE) claim their victims, and may offer a way to test blood for the presence of infectious prions.

The difference, according to Adriano Aguzzi of the University Hospital of Zurich and his colleagues, lies in the ways the prions react to a common blood component known as plasminogen. The team coated tiny magnetic beads with the sticky plasminogen and mixed them with samples of brain tissue from mice that had been infected with a sheep prion disease dubbed scrapie. Subsequent examination of the beads revealed that diseased prions had stuck to the coating. Healthy prions, however, were absent.

Whereas current tests for mutant prions require samples of brain tissue that can only be taken after an animal has died (right), the new research may lead to tests that can be conducted while the animal is still alive. In this way, unnecessary cattle slaughter, for example, might be avoided. And in the U.S., where would-be organ donors who have lived in the U.K. are turned away as a precaution (in response to the U.K.s BSE crisis), fears of contaminated blood might diminish if a reliable screening method were available. Furthermore, researchers might be able to use the sticky beads to rid contaminated blood products of pathological prions. The accuracy of tests and treatments based on the plasminogen approach will depend on how sensitive the binding is. But if future tests bear out, researchers will have a powerful new weapon against the deadly prion diseases.