Prion adsorption to stainless steel is promoted by nickel and molybdenum

A field-deployable diagnostic assay for the visual detection of misfolded prions

Diagnostic tools for the detection of protein-misfolding diseases (i.e., proteopathies) are limited. Gold nanoparticles (AuNPs) facilitate sensitive diagnostic techniques via visual color change for the identification of a variety of targets. In parallel, recently developed quaking-induced conversion (QuIC) assays leverage protein-amplification and fluorescent signaling for the accurate detection of misfolded proteins. Here, we combine AuNP and QuIC technologies for the visual detection of amplified misfolded prion proteins from tissues of wild white-tailed deer infected with chronic wasting disease (CWD), a prion disease of cervids. Our newly developed assay, MN-QuIC, enables both naked-eye and light-absorbance measurements for detection of misfolded prions. MN-QuIC leverages basic laboratory equipment that is cost-effective and portable, thus facilitating real-time prion diagnostics across a variety of settings. In addition to laboratory-based tests, we deployed to a rural field-station in southeastern Minnesota and tested for CWD on site. We successfully demonstrated that MN-QuIC is functional in a non-traditional laboratory setting by performing a blinded analysis in the field and correctly identifying all CWD positive and CWD not-detected deer at the field site in 24 h, thus documenting the portability of the assay. White-tailed deer tissues used to validate MN-QuIC included medial retropharyngeal lymph nodes, parotid lymph nodes, and palatine tonsils. Importantly, all of the white-tailed deer (n = 63) were independently tested using ELISA, IHC, and/or RT-QuIC technologies and results secured with MN-QuIC were 95.7% and 100% consistent with these tests for positive and non-detected animals, respectively. We hypothesize that electrostatic forces help govern the AuNP/prion interactions and conclude that MN-QuIC has great potential for sensitive, field-deployable diagnostics for CWD, with future potential diagnostic applications for a variety of proteopathies.

The importance of ongoing international surveillance for Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive, fatal and transmissible neurodegenerative disease associated with the accumulation of misfolded prion protein in the CNS. International CJD surveillance programmes have been active since the emergence, in the mid-1990s, of variant CJD (vCJD), a disease linked to bovine spongiform encephalopathy. Control measures have now successfully contained bovine spongiform encephalopathy and the incidence of vCJD has declined, leading to questions about the requirement for ongoing surveillance. However, several lines of evidence have raised concerns that further cases of vCJD could emerge as a result of prolonged incubation and/or secondary transmission. Emerging evidence from peripheral tissue distribution studies employing high-sensitivity assays suggests that all forms of human prion disease carry a theoretical risk of iatrogenic transmission. Finally, emerging diseases, such as chronic wasting disease and camel prion disease, pose further risks to public health. In this Review, we provide an up-to-date overview of the transmission of prion diseases in human populations and argue that CJD surveillance remains vital both from a public health perspective and to support essential research into disease pathophysiology, enhanced diagnostic tests and much-needed treatments.

Pros and cons in prion diseases abatement: Insights from nanomedicine and transmissibility patterns

Ample research progress with nanotechnology applications in health and medicine implies precision and accuracy in the scenario of neurodegenerative disorders, for which impending research in ultimate and complete cure has been the vision worldwide. The complexity of prion disease has been unravelled by scientists and demarcated for efficient abatement protocols, but which are still under research and clinical trials. Drug delivery strategies combating prion diseases across the blood brain barrier, the efficacy of drugs and biocompatibility remain a serious question to be thoroughly studied for effective diagnosis and treatment. The present review compiles comprehensively the current treatment modalities against prion diseases and future prospects of nanotechnology addressing diagnosis and treatment of prion diseases with a special emphasis on transmissibility. Further, approaches for anti-prion technology, immunotherapy, and hindrances in vaccine development are discussed.

PAD-Beads enrichment enhances detection of PrPSc using real-time quaking-induced conversion

Objective

Scrapie is a transmissible spongiform encephalopathy (TSE) that naturally occurs in sheep and goats. This fatal neurodegenerative disease results from misfolding of the normal cellular prion protein (PrP^C) to a pathogenic prion protein form (PrP^Sc). This pathogenic form, PrP^Sc, accumulates in the brain and lymphoid tissues. The presence of PrP^Sc can be detected by an in vitro conversion assay known as real-time quaking induced conversion (RT-QuIC). RT-QuIC has been used to detect PrP^Sc in a variety of biological tissues from brains to fluids. While this technique is both rapid and sensitive, enhancing the detection of prions would be valuable in the diagnostic laboratories.

Results

In this study, we assessed whether PrP^Sc detection sensitivity of RT-QuIC can be increased by enriching PrP^Sc in scrapie tissue homogenates using commercially available aggregated protein binding ligands coated magnetic beads (PAD-Beads). Coupling of RT-QuIC to PAD-Beads based cleanup allowed detection of PrP^Sc rapidly and without dilution of scrapie sheep brain homogenates prior to RT-QuIC. The PAD-Beads sample pretreatment step prior to RT-QuIC is a useful enhancement in the diagnosis of TSEs.

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

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.

Effects of heme-PrP complex on cell-free conversion and peroxidase-linked immunodetection of prions in blood-based assays

Prion protein (PrP) binding to natural and synthetic porphyrins has been previously demonstrated but the effects of endogenous heme interactions with PrP remain uncertain. This study investigated implications of this interaction in blood-based peroxidase-linked prion immunodetection and seeded conversion of cellular prion (PrP(C)) into disease associated form (PrP(Sc)). Heme binding to recombinant PrP(C) enhanced intrinsic peroxidase activity (POD) by 2.5-fold and POD inherent to denatured blood accounted for over 84% of luminol-based substrate oxidation in a prion immunodetection assay. An immuno-capture assay showed that 75-98% of blood POD was attributable to binding of PrP(C) with endogenous heme. Additionally, 10 μM heme inhibited (P<0.05) the seeded conversion of PrP(C) to PrP(Sc) through the protein misfolding cycling amplification assay. We conclude that the observed effects can interfere with cell-free conversion and peroxidase-linked immunodetection of prions in blood-based assays. These results indicate that heme-PrP interactions could modulate intrinsic POD and protect PrP(C) from conversion into PrP(Sc).

Homogenous photocatalytic decontamination of prion infected stainless steel and titanium surfaces

Prions are notorious for their extraordinary resistance to traditional methods of decontamination, rendering their transmission a public health risk. Iatrogenic Creutzfeldt-Jakob disease (iCJD) via contaminated surgical instruments and medical devices has been verified both experimentally and clinically. Standard methods for prion inactivation by sodium hydroxide or sodium hypochlorite have failed, in some cases, to fully remove prion infectivity, while they are often impractical for routine applications. Prion accumulation in peripheral tissues and indications of human-to-human bloodborne prion transmission, highlight the need for novel, efficient, yet user-friendly methods of prion inactivation. Here we show both in vitro and in vivo that homogenous photocatalytic oxidation, mediated by the photo-Fenton reagent, has the potential to inactivate the pathological prion isoform adsorbed on metal substrates. Photocatalytic oxidation with 224 μg mL(-1) Fe (3+), 500 μg mL(-1) h(-1) H 2O 2, UV-A for 480 min lead to 100% survival in golden Syrian hamsters after intracranial implantation of stainless steel wires infected with the 263K prion strain. Interestingly, photocatalytic treatment of 263K infected titanium wires, under the same experimental conditions, prolonged the survival interval significantly, but failed to eliminate infectivity, a result that we correlate with the increased adsorption of PrP(Sc) on titanium, in comparison to stainless steel. Our findings strongly indicate that our, user--and environmentally--friendly protocol can be safely applied to the decontamination of prion infected stainless steel surfaces.

Cleaning, disinfection and sterilization of surface prion contamination

BACKGROUND

Prion contamination is a risk during device reprocessing, being difficult to remove and inactivate. Little is known of the combined effects of cleaning, disinfection and sterilization during a typical reprocessing cycle in clinical practice.

AIM

To investigate the combination of cleaning, disinfection and/or sterilization on reducing the risk of surface prion contamination.

METHODS

In vivo test methods were used to study the impact of cleaning alone and cleaning combined with thermal disinfection and high- or low-temperature sterilization processes. A standardized test method, based on contamination of stainless steel wires with high titres of scrapie-infected brain homogenates, was used to determine infectivity reduction.

FINDINGS

Traditional chemical methods of surface decontamination against prions were confirmed to be effective, but extended steam sterilization was more variable. Steam sterilization alone reduced the risk of prion contamination under normal or extended exposure conditions, but did show significant variation. Thermal disinfection had no impact in these studies. Cleaning with certain defined formulations in combination with steam sterilization can be an effective prion decontamination process, in particular with alkaline formulations. Low-temperature, gaseous hydrogen peroxide sterilization was also confirmed to reduce infectivity in the presence and absence of cleaning.

CONCLUSION

Prion decontamination is affected by the full reprocessing cycle used on contaminated surfaces. The correct use of defined cleaning, disinfection and sterilization methods as tested in this report in the scrapie infectivity assay can provide a standard precaution against prion contamination.

Spiroplasma spp. biofilm formation is instrumental for their role in the pathogenesis of plant, insect and animal diseases

Spiroplasma spp. are important phyto and insect pathogens, and candidate causal agent/s of transmissible spongiform encephalopathies (TSE) in man and animals. These filterable wall-less bacteria are widely distributed in nature with an unspecified environmental reservoir. In this study we showed by scanning electron microscopy that spiroplasma form biofilm on an assortment of hard surfaces including mica, nickel and stainless steel. Spiroplasma were stuck to the surfaces by fibrillar threads consistent with curli fibers (an amyloid protein found in bacterial biofilms). After a lengthy time in cultures (6 weeks), spiroplasma in biofilm bound to mica disks lost their spiral shapes and formed coccoid forms interconnected by long (>2 μm) branched membranous nanotubules, therein representing direct conjugate connections between the cells. The affinity of spiroplasma biofilms for mica and nickel, and the membrane communications suggest that soil could be a reservoir for these bacteria. The persistence of clay bound spiroplasma in soil could serve as the mechanism of lateral spread of TSEs by ingestion of soil by ruminants. Spiroplasma binding to stainless steel wire supports bacterial contamination of surgical instruments following surgery on dementia patients as a mechanism of iatrogenic transmission of TSEs, especially with resistance of spiroplasma in biofilms to drying or exposure to 50% glutaraldehyde. The discovery of biofilm formation by spiroplasma addresses questions regarding environmental persistence of these organisms in nature and suggests novel mechanisms of intercellular communication and transmission.

Superparamagnetic nanoparticle capture of prions for amplification

Prion diseases are associated with the presence of PrP(Sc), a disease-associated misfolded conformer of the prion protein. We report that superparamagnetic nanoparticles bind PrP(Sc) molecules efficiently and specifically, permitting magnetic separation of prions from a sample mixture. Captured PrP(Sc) molecules retain the activity to seed protein misfolding cyclic amplification (PMCA) reactions, enabling the rapid concentration of dilute prions to improve detection. Furthermore, superparamagnetic nanoparticles clear contaminated solutions of PrP(Sc). Our findings suggest that coupling magnetic nanoparticle capture with PMCA could accelerate and improve prion detection. Magnetic nanoparticles may also be useful for developing a nontoxic prion decontamination method for biologically derived products.