Protein amplification from peripheral tissues

      Prion diseases are infectious and fatal neurodegenerative disorders affecting humans and animals, associated to the accumulation of the misfolded prion protein (PrPSc), which behaves as an infectious agent to transmit the disease. The most common disease in humans is sporadic Creutzfeldt-Jakob disease (sCJD), and the most worrisome is variant CJD (vCJD) which is associated to consumption of cattle derived food infected with bovine spongiform encephalopathy. The number of asymptomatic carriers of vCJD in the UK alone is estimated to be 1 in 2,000 people and vCJD has been demonstrated to be transmitted from human-to-human by blood transfusion. Development of a biochemical assay for the sensitive, specific, early and non-invasive detection of prions in tissues and biological fluids from people infected with prions is a top medical priority to decrease the further spreading of the disease and to increase the safety of the blood supply. For this purpose we developed the protein misfolding cyclic amplification (PMCA) technology which reproduces the prion replication process in vitro in an accelerated manner and enables detection of minute quantities of prions, up to the level of a single particle of PrPSc. Using PMCA we were able to detect PrPSc in samples of blood and urine from vCJD patients with sensitivities and specificities approaching 100%. We also found detectable PrPSc is all of 91 tissues analyzed from vCJD patients, including skin, muscle, lung, heart, kidney, etc. Finally, a study in non-human primates inoculated with vCJD prions showed that PMCA enable to detect PrPSc in blood of animals during the entire incubation period of the disease, years before the monkeys become clinically ill. Our findings indicate that PrPSc detection in easily accessible tissues and biological fluids offers a good opportunity to diagnose the disease even at the clinically silent stage of prion infection. Implementation of the PMCA technology may substantially improve blood safety and help treatment of the disease before brain becomes irreversible.
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