Research Article: Enhanced detection of prion infectivity from blood by preanalytical enrichment with peptoid-conjugated beads

Date Published: September 12, 2019

Publisher: Public Library of Science

Author(s): Simone Hornemann, Petra Schwarz, Elisabeth J. Rushing, Michael D. Connolly, Ronald N. Zuckermann, Alice Y. Yam, Adriano Aguzzi, Gianluigi Zanusso.

http://doi.org/10.1371/journal.pone.0216013

Abstract

Prions cause transmissible infectious diseases in humans and animals and have been found to be transmissible by blood transfusion even in the presymptomatic stage. However, the concentration of prions in body fluids such as blood and urine is extremely low; therefore, direct diagnostic tests on such specimens often yield false-negative results. Quantitative preanalytical prion enrichment may significantly improve the sensitivity of prion assays by concentrating trace amounts of prions from large volumes of body fluids. Here, we show that beads conjugated to positively charged peptoids not only captured PrP aggregates from plasma of prion-infected hamsters, but also adsorbed prion infectivity in both the symptomatic and preclinical stages of the disease. Bead absorbed prion infectivity efficiently transmitted disease to transgenic indicator mice. We found that the readout of the peptoid-based misfolded protein assay (MPA) correlates closely with prion infectivity in vivo, thereby validating the MPA as a simple, quantitative, and sensitive surrogate indicator of the presence of prions. The reliable and sensitive detection of prions in plasma will enable a wide variety of applications in basic prion research and diagnostics.

Partial Text

Transmissible spongiform encephalopathies (TSEs) or prion diseases are caused by conformational transitioning of the physiological host-encoded prion protein, PrPC, into a misfolded and aggregated form, PrPSc that accumulates in the brain in the form of plaques or smaller plaque-like deposits [1, 2]. PrPSc differs from PrPC in several biochemical and physicochemical properties such as its insolubility and partial resistance to proteinase K [1].

Previously, we have reported that the MPA could detect prion aggregates with high sensitivity in the brain of a patient with a familial prion disease [27]. Crucially, the MPA detected PK sensitive conformers of PrPSc that were only barely detectable by standard methods [27]. The analytical sensitivity of the MPA has recently been determined in a spiking experiment of a BH from a vCJD patient into normal human plasma. PrP aggregates were still detectable at a dilution below 10 nl/ml (10−6 dilution, LOD estimated to be < 40 pg/ml of aggregated PrP) [31]. These findings prompted us to investigate further the sensitivity of the peptoid-conjugated beads to capture prion infectivity from the plasma of prion-infected hamsters. This is biologically and medically relevant because (1) the conformation of infectious PrP in blood is unknown and (2) the detection of prions in blood and blood products continues to represent a major analytical challenge.   Source: http://doi.org/10.1371/journal.pone.0216013

 

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