Scientists use glowing molecules to identify prions
EU-funded researchers have come up with a new method involving glowing molecules for detecting and characterising prions. Prion diseases occur when abnormally-folded infectious prions cause normally-folded proteins in the brain to become similarly malformed. Examples include BSE (Bovine Spongiform Encephalopathy, commonly known as mad cow disease), scrapie (which affects sheep) and Creutzfeldt-Jakob Disease (CJD). Although prions are not easily transmitted from one species to another, once they have entered a new species, they can rapidly adapt and become contagious. Although levels of BSE are now falling, other prion disorders are on the increase, and there is concern that these could infect humans. 'Because prion strains may vary in their transmissibility to humans, strain discrimination is of keen interest for prion diagnostics and for public health,' the researchers write in their article in the journal Nature Methods. The scientists infected mice with four different prion diseases (BSE, chronic wasting disease (also known as 'mad elk disease') and two strains of scrapie) for several generations in a row. Over time, new strains of prions emerged, making the diseases more deadly to the mice. The researchers took tissue samples from the mice, and stained them with a fluorescent molecule called a luminescent conjugated polymer. When the polymer binds with prions, it changes colour. By altering the molecule, the researchers were able to get it to show different colours for different prion diseases. The new technique also proved successful at identifying prions in tissue taken from other animals which had died from prion diseases, such as cows infected with BSE and prion-infected deer and sheep. 'Using our methods, we can directly see the structure of the prions and thereby deduce the disease,' said Peter Nilsson of the University Hospital Zurich, one of the lead authors of the study. The new method could have a number of useful applications, for example in screening blood products. In the UK, over 60 people have received blood from blood donors who were subsequently discovered to be infected with new variant CJD, the human form of BSE. Of those who received infected blood, four have since been shown to be infected. The technique could also prove useful in studying other diseases caused by misfolded proteins. 'For us researchers it is truly exciting to use this technique to understand more about both prions and other defectively folded proteins that give rise to similar disorders, such as Alzheimer's,' said Peter Hammarström of the prion laboratory at Linköping University in Sweden. EU funding for the work came from the UPMAN (Understanding Protein Misfolding and Aggregation by NMR) and TSEUR (An integrated immunological and cellular strategy for sensitive TSE diagnosis and strain discrimination) projects, both of which are financed under the 'Life sciences, genomics and biotechnology for health' thematic area of the Sixth Framework Programme (FP6).