Explore the vast range of titles available.

Definitive diagnosis of prion disease currently requires postmortem brain tissue. Now, Ryuichiro Atarashi and colleagues have discovered an assay that can identify prions in human cerebrospinal fluid. This assay could allow for diagnosis of disease in living humans. The development of technologies for the in vitro amplification of abnormal conformations of prion protein (PrP Sc ) has generated the potential for sensitive detection of prions. Here we developed a new PrP Sc amplification assay, called real-time quaking-induced conversion (RT-QUIC), which allows the detection of ≥1 fg of PrP Sc in diluted Creutzfeldt-Jakob disease (CJD) brain homogenate. Moreover, we assessed the technique first in a series of Japanese subjects and then in a blind study of 30 cerebrospinal fluid specimens from Australia, which achieved greater than 80% sensitivity and 100% specificity. These findings indicate the promising enhanced diagnostic capacity of RT-QUIC in the antemortem evaluation of suspected CJD.

Oligodendrocyte-lineage cells, including NG2 glia, undergo prominent changes in various neurodegenerative disorders. Here, we identify a neuroprotective role for NG2 glia against prion toxicity. NG2 glia were activated after prion infection in cerebellar organotypic cultured slices (COCS) and in brains of prion-inoculated mice. In both model systems, depletion of NG2 glia exacerbated prion-induced neurodegeneration and accelerated prion pathology. Loss of NG2 glia enhanced the biosynthesis of prostaglandin E2 (PGE2) by microglia, which augmented prion neurotoxicity through binding to the EP4 receptor. Pharmacological or genetic inhibition of PGE2 biosynthesis attenuated prion-induced neurodegeneration in COCS and mice, reduced the enhanced neurodegeneration in NG2-glia-depleted COCS after prion infection, and dampened the acceleration of prion disease in NG2-glia-depleted mice. These data unveil a non-cell-autonomous interaction between NG2 glia and microglia in prion disease and suggest that PGE2 signaling may represent an actionable target against prion diseases. Oligodendrocyte-lineage NG2 glia are shown to limit prion-induced neurodegeneration by quenching toxic microglial responses. Their depletion unleashes prostaglandin E2 secretion by microglia and contributes non-cell-autonomously to prion toxicity.

Prion diseases share common clinical and pathological characteristics such as spongiform neuronal degeneration and deposition of an abnormal form of a host-derived protein, termed prion protein. The characteristic features of prion diseases are long incubation times, short clinical courses, extreme resistance of the transmissible agent to degradation and lack of nucleic acid involvement. Sporadic and genetic forms of prion diseases occur worldwide, of which genetic forms are associated with mutations in PRNP . Human to human transmission of these diseases has occurred due to iatrogenic exposure, and zoonotic forms of prion diseases are linked to bovine disease. Significant progress has been made in the diagnosis of these disorders. Clinical tools for diagnosis comprise brain imaging and cerebrospinal fluid tests. Aggregation assays for detection of the abnormally folded prion protein have a clear potential to diagnose the disease in peripherally accessible biofluids. After decades of therapeutic nihilism, new treatment strategies and clinical trials are on the horizon. Although prion diseases are relatively rare disorders, understanding their pathogenesis and mechanisms of prion protein misfolding has significantly enhanced the field in research of neurodegenerative diseases. This Primer by Zerr et al. discusses the epidemiology, pathophysiology, diagnosis and potential future treatments for Creutzfeldt–Jakob disease and other human prion diseases.

While cerebrospinal fluid (CSF) biomarkers for Creutzfeldt-Jakob disease (CJD) are established and partly included in the diagnostic criteria, no blood biomarkers are available. Here, we assessed the utility of serum neurofilament light chain (NF-L) and tau protein in comparison to CSF markers (NF-L and phosphorylated NF heavy chain (pNF-H), tau, S100B, 14-3-3) and prion conversion assay (real-time quaking induced conversion (RT-QuIC)) for sporadic and genetic CJD. Importantly, a Gerstmann-Sträussler-Scheinker mutation carrier in the asymptomatic phase and at disease onset was included as well. Both NF-L and tau were markedly increased in CJD serum, reaching similar or even better performance as in CSF (sensitivity and specificity for serum NF-L 100% and 85.5%, and for serum tau 84.6% and 96.2%, respectively). Serum S100B showed high sensitivity as well (84.2%), but lower specificity (63%). CSF neurofilaments were increased before symptom onset, while prion seeding assay was negative. Just before a clinical diagnosis could be made, all CSF markers and NF-L in the serum were increased and CSF prion conversion assay was positive. The data suggest that neurofilaments are sensitive and specific blood markers for the diagnosis of genetic and sporadic CJD and might represent promising tools to predict disease onset.

The self-templating nature of prions plays a central role in prion pathogenesis and is associated with infectivity and transmissibility. Since propagation of proteopathic seeds has now been acknowledged a principal pathogenic process in many types of dementia, more insight into the molecular mechanism of prion replication is vital to delineate specific and common disease pathways. By employing highly discriminatory anti-PrP antibodies and conversion-tolerant PrP chimera, we here report that de novo PrP conversion and formation of fibril-like PrP aggregates are distinct in mechanistic and kinetic terms. De novo PrP conversion occurs within minutes after infection at two subcellular locations, while fibril-like PrP aggregates are formed exclusively at the plasma membrane, hours after infection. Phenotypically distinct pools of abnormal PrP at perinuclear sites and the plasma membrane show differences in N-terminal processing, aggregation state and fibril formation and are linked by exocytic transport via synaptic and large-dense core vesicles. In this work, the authors investigated the cellular mode of prion propagation. The report that proteopathic seeds of abnormal PrP are N-terminally truncated and detected within minutes after infection. These seeds reach the plasma membrane by regulated secretory pathways where phenotypically distinct fibril-like PrP aggregates are formed with a lag of 24 h after infection.

Alzheimer's disease (AD), the most common type of senile dementia, is associated to the build-up of misfolded amyloid-β (Aβ) in the brain. Although compelling evidences indicate that the misfolding and oligomerization of Aβ is the triggering event in AD, the mechanisms responsible for the initiation of Aβ accumulation are unknown. In this study, we show that Aβ deposition can be induced by injection of AD brain extracts into animals, which, without exposure to this material, will never develop these alterations. The accumulation of Aβ deposits increased progressively with the time after inoculation, and the Aβ lesions were observed in brain areas far from the injection site. Our results suggest that some of the typical brain abnormalities associated with AD can be induced by a prion-like mechanism of disease transmission through propagation of protein misfolding. These findings may have broad implications for understanding the molecular mechanisms responsible for the initiation of AD, and may contribute to the development of new strategies for disease prevention and intervention.

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.

Prion diseases are fatal, infectious, neurodegenerative disorders resulting from accumulation of misfolded cellular prion protein in the brain. Early pathological changes during CNS prion disease also include reactive astrocyte activation with increased CD44 expression, microgliosis, as well as loss of dendritic spines and synapses. CD44 is a multifunctional cell surface adhesion and signalling molecule which is considered to play roles in astrocyte morphology and the maintenance of dendritic spine integrity and synaptic plasticity. However, the role of CD44 in prion disease was unknown. Here we used mice deficient in CD44 to determine the role of CD44 during prion disease. We show that CD44-deficient mice displayed no difference in their response to CNS prion infection when compared to wild type mice. Furthermore, the reactive astrocyte activation and microgliosis that accompanies CNS prion infection was unimpaired in the absence of CD44. Together, our data show that although CD44 expression is upregulated in reactive astrocytes during CNS prion disease, it is dispensable for astrocyte and microglial activation and the development of prion neuropathogenesis.

PrP Sc , the infective agent for transmissible spongiform encephalopathies, is the misfolded form of the prion protein that can template the conversion of the native fold of the protein (PrP C ). The high-resolution structure of PrPSc remains elusive. This review presents recent progress in the area and existing structural models, in addition to discussing the challenges ahead. PrP Sc , the infective agent for transmissible spongiform encephalopathies, is the misfolded form of the prion protein that can template the conversion of the native fold of the protein (PrP C ). The high-resolution structure of PrPSc remains elusive. This review presents recent progress in the area and existing structural models, in addition to discussing the challenges ahead. Prions are the proteinaceous infectious agents responsible for the transmission of prion diseases. The main or sole component of prions is the misfolded prion protein (PrP Sc ), which is able to template the conversion of the host's natively folded form of the protein (PrP C ). The detailed mechanism of prion replication and the high-resolution structure of PrP Sc are unknown. The currently available information on PrP Sc structure comes mostly from low-resolution biophysical techniques, which have resulted in quite divergent models. Recent advances in the production of infectious prions, using very pure recombinant protein, offer new hope for PrP Sc structural studies. This review highlights the importance of, challenges for and recent progress toward elucidating the elusive structure of PrP Sc , arguably the major pending milestone to reach in understanding prions.