Detection of water-soluble disease-associated PrP species in blood and brain of scrapie-infected hamster

Abstract

The high-speed supernatant (S(HS)) of scrapie-infected hamster brain homogenate contains a soluble infectivity similar to that of the plasma that escapes leukodepletion and can transmit prion infection. This recent finding highlights the fact that soluble prion infectivity could be relevant for prion disease propagation and progression. PrP(Sc) is essential in prion disease pathogenesis, but little to nothing is known about the PrP(Sc) species that may be associated with this form of prion infectivity. Scrapie-infected hamster plasma and S(HS) were subjected to biochemical analysis, and the results demonstrate for the first time that soluble infectivity is associated with a water-soluble PrP(Sc) species with substantially different properties from classical PrP(Sc), the concentration of which seems to correlate with the magnitude and efficiency of the soluble infectivity. Such characteristics suggest that this species might represent the soluble prion agent itself or its vehicle, highlighting the need to adequately revise the strategies involved in prion removal, diagnosis, and therapy.

Analysis of the Glycosylation Profile of Disease-Associated Water-Soluble Prion Protein Using Lectins

“…Classical PrP C and PrP Sc have a similar glycosylation profile, although some glycosylation differences between them have been detected [9, 11], and ws-PrP C and ws-PrP Sc have identical biochemical-physical properties [3]. Taking into account these two characteristic aspects of the classical PrP and ws-PrP, the comparisons between the two proteins were performed using infected material and only when necessary also noninfected material.…”

“…Plasma was prepared as described previously [3, 9]. Blood was collected from individual Syrian hamsters (at time zero and at different time points after scrapie-infection) in tubes containing sodium citrate and separated into components by centrifugation at 2,000 x g for 15 min at 4°C.…”

“…The amount of total proteins from plasma, S HS , and P HS loaded into ELISA plate is based on calculations made in a previous study [3], in which PrP Sc from plasma, S HS , and P HS had been quantitatively and qualitatively characterized. These amounts of total proteins (which contain an excess of PrP Sc that guarantee a saturated binding to the antibodies) have been calculated in order to allow for the binding of equivalent amounts of PrP to the capturing antibodies, as shown in Figure 1.…”

“…A recent study revealed the existence of a water-soluble form of the prion protein (ws-PrP) in blood plasma and brain of Syrian hamster [3]. This PrP has biochemical-physical properties that are substantially different from those of the classical PrP.…”

“…This PrP has biochemical-physical properties that are substantially different from those of the classical PrP. Particularly, a Western blot of normal ws-PrP (ws-PrP C ) and disease-associated ws-PrP (ws-PrP Sc ) [3] displayed a glycotyping that was different from that of the classical PrP C and PrP Sc , showing a slightly faster migration mobility and a diglycoslated band with higher propensity to degradation by endogenous enzymes. This increased susceptibility to degradation of ws-PrP compared to the classical PrP may be due to an instability issue caused by glycosylation differences between the two proteins.…”