Protection from prions
Bovine spongiform encephalopathy (BSE), also called mad cow disease, decimated European cow populations over 20 years ago and caused major food scares across Europe. It even leapt across the species barrier to infect some humans with vCJD, killing around 200 people. Extensive research is required to prevent or deal with emergence of diseases due to prion infection. The PRIORITY (Protecting the food chain from prions: Shaping European priorities through basic and applied research) project focused on four areas: structure and function, detection, transmission and epidemiology. Structure and transmission research have resulted in a low-resolution model of the spongiform encephalopathy that infects goats and sheep, scrapie (PrPSc) together with the key characteristics of recombinant prions. The researchers have identified two key sites for conversion of the cell prion (PrPc) to the infectious PrPSc. On a biochemical level, the flexible tail of PrPc has a role in associated toxicity together with key signalling cascades that have been elucidated. Detection methods developed include a strain identification assay using luminescence, a high-throughput Förster resonance energy transfer-based assay to detect prions. The scientists also devised a process to amplify misfolded proteins and identify prions in milk, blood and waste. Results showed that prion infectivity is quite persistent in wastewater. To contain further spread, better decontamination methods for surgical instruments were developed as well as an improved system to decontaminate waste with microwave technology. Researchers found that prions spread from exposure site to brain via initial accumulation on follicular dendritic cells, and elucidated the routes of prion propagation from the gut to the central nervous system. An age-related decline in the effectiveness of the immune system is a major factor in susceptibility of older individuals, and elements of blood and milk that carry prion-related infectivity were identified. Overall, the conclusions are that atypical scrapie can transmit to humans and that strain properties change with the species barrier breach. PRIORITY confirmed that the ban on meat and bone meal was the most significant factor supporting the containment of BSE, and recommended continuing the prohibition. Sustained research in prion research will also identify factors that help prions flourish and cross to different species together with the means to disrupt this process.
Keywords
Prions, misfolded proteins, mad cow disease, BSE, species barrier, scrapie
