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Efficient prion disease transmission through common environmental materials - PubMed

  • ️Mon Jan 01 2018

Efficient prion disease transmission through common environmental materials

Sandra Pritzkow et al. J Biol Chem. 2018.

Abstract

Prion diseases are a group of fatal neurodegenerative diseases associated with a protein-based infectious agent, termed prion. Compelling evidence suggests that natural transmission of prion diseases is mediated by environmental contamination with infectious prions. We hypothesized that several natural and man-made materials, commonly found in the environments of wild and captive animals, can bind prions and may act as vectors for disease transmission. To test our hypothesis, we exposed surfaces composed of various common environmental materials (i.e. wood, rocks, plastic, glass, cement, stainless steel, aluminum, and brass) to hamster-adapted 263K scrapie prions and studied their attachment and retention of infectivity in vitro and in vivo Our results indicated that these surfaces, with the sole exception of brass, efficiently bind, retain, and release prions. Prion replication was studied in vitro using the protein misfolding cyclic amplification technology, and infectivity of surface-bound prions was analyzed by intracerebrally challenging hamsters with contaminated implants. Our results revealed that virtually all prion-contaminated materials transmitted the disease at high rates. To investigate a more natural form of exposure to environmental contamination, we simply housed animals with large contaminated spheres made of the different materials under study. Strikingly, most of the hamsters developed classical clinical signs of prion disease and typical disease-associated brain changes. Our findings suggest that prion contamination of surfaces commonly present in the environment can be a source of disease transmission, thus expanding our understanding of the mechanisms for prion spreading in nature.

Keywords: Creutzfeldt-Jakob disease; chronic wasting disease; neurodegeneration; neurodegenerative disease; prion; prion disease; protein misfolding; scrapie.

© 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

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Conflict of interest statement

Dr. Soto is inventor on several patents related to the PMCA technology and is currently founder, chief scientific officer, and vice president of Amprion Inc., a biotech company focusing on the commercial utilization of PMCA for diagnosis of various neurodegenerative diseases

Figures

Figure 1.
Figure 1.

Ability of PrPSc attached to different surfaces to sustain in vitro prion replication. Serial dilutions of 263K brain homogenate (10−2–10−9) were incubated with either polypropylene, glass, stainless steel, wood, rock, cement, aluminum, or brass beads (0.32 cm diameter) for 16 h at room temperature. Water-washed and dried beads were mixed with PMCA substrate, and the presence of resulting PrPSc attached to each material was detected by PMCA. A, results of the polypropylene, rock, aluminum, and brass beads are shown as a representation of the different degrees of PMCA data obtained. Results with the rest of the materials are shown in

Fig. S1

. F, non-amplified control; 1, 2, and 3, PMCA rounds. B, summary of the last detectable dilution for each surface. ND, not detectable. C, as controls, 10% normal brain homogenate (NBH) was incubated with beads made of the different materials. After washing and drying, beads were added to PMCA tubes, and the reaction was carried out for three consecutive rounds of amplification. The blot displays representative results of the third PMCA round. As positive controls of PMCA amplification, various dilutions of 263K brain homogenate (10−7–10−10) are shown. In A and C, all samples, except for PrPC used as a migration control, were PK-treated. Numbers at the left of the blots indicate molecular mass markers. Data shown in this figure correspond to representative results obtained in two different experiments.

Figure 2.
Figure 2.

Interference of different materials on PMCA reactions. A, aliquots of PMCA substrate were spiked with different dilutions of 263K-infected brain homogenates (10−5–10−12) and submitted to incubation/sonication cycles. Additional aliquots of PMCA substrate were spiked with two high dilutions of 263K–infected brains (10−7 (B) and 10−9 (C)), mixed with untreated beads (0.32 cm in diameter) made of different materials, and immediately submitted to PMCA. Serial PMCA rounds were performed as described under “Experimental procedures.” All samples were PK-treated with the sole exception of PrPC used as a control for the electrophoretic mobility. Numbers at the left of each membrane depict molecular mass markers. Data shown in this figure correspond to representative results obtained in two different experiments.

Figure 3.
Figure 3.

Interaction of rodent, cervid, and human prions with different materials. To investigate whether prions from other species also interact with the materials under study, serial dilutions of RML, vCJD, and CWD brain homogenates (10−3, 10−5, and 10−7) were incubated either with polypropylene, glass, stainless steel, wood, rock, cement, aluminum, or brass beads (0.32 cm in diameter) for 16 h at room temperature. After thorough washing and drying, beads were mixed with respective PMCA substrate (wildtype mice or transgenic mice expressing human or deer PrPC) and subjected to three consecutive rounds of PMCA. Samples were analyzed by Western blotting using 6D11 or PRC1 anti-PrP antibody, and results of the third round of PMCA are shown. All samples were PK-treated with the sole exception of PrPC used as a control for the electrophoretic mobility. Numbers at the left of each membrane depict molecular mass markers. Numbers at the right indicate the dilution of brain homogenate used to incubate the beads.

Figure 4.
Figure 4.

In vivo assessment of prion transmission through contaminated surfaces implanted in the brain. The figure shows the survival curves (A), average incubation times and attack rates (B), and analysis of protease-resistant PrPSc (C) for hamsters intracerebrally (ic) challenged with implants exposed to 263K brain homogenates. Animals treated with implants incubated with normal brain homogenates (NBH) were also included as controls. All samples in C, except PrPC used as a migration control, were PK-treated. Numbers on the left of the blots represent molecular mass markers.

Figure 5.
Figure 5.

Disease transmission by simple exposure to prion-contaminated surfaces. The figure shows the survival curves (A), average incubation times and attack rates (B), and biochemical assessments of protease-resistant PrPSc (C) for hamsters exposed to large spheres contaminated with 263K prions. Animals in contact with spheres exposed to normal brain homogenates (NBH) were also included as controls. The middle panel in C depicts brains from animals exposed to 263K-contaminated spheres but not developing clinical signs. All samples, except PrPC used as a migration control, were PK-treated. Numbers at the left of the blots in C represent molecular mass markers.

Figure 6.
Figure 6.

Mimicking different modes of prion exposure to contaminated surfaces. A, schematic representation of three potential routes by which prions attached to large spheres may get access to the animals: (i) direct exposure through licking or sniffing the materials, (ii) indirect exposure through rubbing against the surfaces, and (iii) secondary exposure through transmission of prions from the surface to other components of the environment (e.g. bedding). Survival curves (B), average incubation periods and attack rates (C), and biochemical analysis (D) of protease-resistant PrPSc for hamsters exposed to 263K-contaminated polypropylene spheres mimicking rubbing, licking, and shedding of prions to bedding are shown. Data of animals challenged with spheres treated with normal brain extracts (NBH) are also included as controls. Analysis of 263K-treated asymptomatic animals is also shown (middle panel in D). All samples, except PrPC used as migration control, were PK-treated. Numbers at the left of blots in D represent molecular mass markers.

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