Detection of prions in blood

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Abstract
Prion diseases are caused by an unconventional infectious agent termed prion, composed mainly of the misfolded prion protein (PrPSc)1. The development of highly sensitive assays for biochemical detection of PrPSc in blood is a top priority for minimizing the spread of the disease2. Here we show that the protein misfolding cyclic amplification (PMCA) technology3 can be automated and optimized for high-efficiency amplification of PrPSc. We show that 140 PMCA cycles leads to a 6,600-fold increase in sensitivity over standard detection methods. Two successive rounds of PMCA cycles resulted in a 10 million–fold increase in sensitivity and a capability to detect as little as 8,000 equivalent molecules of PrPSc. Notably, serial PMCA enables detection of PrPSc in blood samples of scrapie-afflicted hamsters with 89% sensitivity and 100% specificity. These findings represent the first time that PrPSc has been detected biochemically in blood, offering promise for developing a noninvasive method for early diagnosis of prion diseases.