Genetically mediated increased expression of syntaxin-6, a SNARE protein involved in intracellular protein trafficking, is a proposed risk mechanism for progressive supranuclear palsy and sporadic prion disease. Increased syntaxin-6 protein levels are also causally associated with Alzheimer’s disease, suggesting it may have shared roles across multiple neurodegenerative diseases. However, no study has validated its functional role in tauopathies. To validate a role for syntaxin-6 in tauopathy pathogenesis, we knocked out syntaxin-6 in humanised P301S tauopathy mice. Mice underwent longitudinal rotarod testing, gait analysis, frailty and weight assessment, with neuropathological, biochemical and pathological analyses at 3 and 5 months. Stx6+/+;hTauP301S/P301S mice showed motor impairment from 1 month of age, which was partially rescued by syntaxin-6 knockout from months 1 to 4, with additional protection of gait at 5.5 months. Physiologically, syntaxin-6 knockout exerted a protective effect on weight trajectories and measures of frailty. Reduced neurodegeneration in the superficial cortex was observed at 3 months, as well as higher synaptic coverage at 5 months of age, supporting preserved neuropathological measures related to function. We further observed localised increases in tau pathology in the spinal cord and defined brain regions in young Stx6−/−;hTauP301S/P301S mice, despite total tau levels being comparable, in keeping with altered trafficking of pathological tau species with syntaxin-6 knockout. Despite a partial, early phenotypic rescue of functional measures, terminal endpoint comparisons were confounded by a 20

Importance:Alzheimer disease (AD) is pathologically characterized by the deposition of amyloid-β (Aβ) and hyperphosphorylated tau. Human transmission of Aβ pathology in a prion-like fashion has resulted in iatrogenic cerebral amyloid angiopathy. More recently, iatrogenic Alzheimer disease (iAD) was described in recipients of cadaveric pituitary-derived human growth hormone (c-hGH) contaminated with Aβ amyloid seeds. Objective:To describe the clinical and postmortem findings in iAD. Design, Setting, and Participants:This case series describes 4 c-hGH recipients who were referred to the UK National Prion Clinic. Between February 2024 and February 2025, 14 c-hGH recipients had been referred to this service, with clinical assessments ongoing. The current study included 4 of 14 people treated with c-hGH who were referred since the original report. These data were analyzed during February and March 2025. Exposure:c-hGH contaminated with Aβ amyloid seeds. Main Outcomes and Measures:Clinical and histopathological description. Results:The study describes 4 males who developed dementia following confirmed or suspected c-hGH treatment in childhood (age at symptom onset between 47 and 60 years) with cognitive syndromes characterized by prominent language involvement. Results include clinical and postmortem findings for 1 patient (onset at age 47 years) in whom postmortem examination (at age 57 years) showed unequivocal neuropathological features of AD, including severe tauopathy. Brief descriptions of 3 additional patients with prominent language involvement are also provided. Conclusions and Relevance:These results demonstrate that patients with iAD can have histopathological findings classically found in sporadic AD and that prominent language involvement might be an important phenotypic feature in this AD subtype.

Prion diseases represent a unique biological paradigm with mechanistic parallels to other neurodegenerative conditions like Alzheimer's and Parkinson's diseases. However, the study of human prion pathobiology and the development of effective therapeutics has been severely constrained by the inability to propagate human prions in dividing cells-forcing reliance on costly and slow animal bioassays. Here, we report the generation of EKV cells-a humanized cell model which supports the robust, indefinite propagation of sporadic Creutzfeldt-Jakob disease (sCJD) prions. We demonstrate that these cells replicate bona fide human prion infectivity in culture-cell lysates induce lethal neurodegeneration in humanized mice that is clinically and neuropathologically indistinguishable from inoculation with sCJD-infected brain tissue. We use EKV cells to develop the Human Prion Assay (HPA), which quantifies sCJD infectivity with sensitivity comparable to gold-standard mouse bioassay, while reducing the experimental timeline from years to weeks. Furthermore, we demonstrate that established sCJD infection can be cured by an anti-prion protein antibody, validating the system as a high-throughput platform for drug discovery. This model bridges a critical translational gap, offering a renewable alternative to animal bioassays, a paradigm to dissect the biology of human sCJD prion disease and screen for therapeutic agents.

Prion diseases, of which Creutzfeldt-Jakob disease is the most common, are fatal neurodegenerative disorders and are often rapidly progressive. They are associated with a significant palliative care burden for patients and families, ranging from prognostic uncertainty to complex symptom management to caregiver distress. Healthcare professionals face unique pressures when caring for these patients, which can include a lack of familiarity with this rare diagnosis and rapidly evolving symptom needs due to accelerated clinical deterioration. We convened a multidisciplinary panel of experts from around the UK, including palliative care doctors, general practitioners, physician and nurse specialists in prion diseases, and a lived experience representative to compile practical, consensus-based recommendations for managing prion diseases, much of which can also be applied to other rapidly progressive dementias. In this article, we examine the available evidence base for managing various aspects of prion diseases. Where evidence is limited, we suggest best practices informed by decades of our collective experiences.

BACKGROUND AND OBJECTIVES: Prion diseases can mimic Alzheimer disease (AD) at presentation. Alzheimer's Association AD diagnostic criteria suggest that a single abnormal highly specific plasma biomarker (including p-tau217) is sufficient for a biological diagnosis. We investigated the performance of AD plasma biomarkers in distinguishing AD and prion diseases. METHODS: We examined plasma biomarker data from patients with prion disease from a prospective cohort study recruited through the UK National Prion Clinic. Prion diseases were diagnosed clinically or with autopsy confirmation, and AD was diagnosed clinically with CSF biomarker confirmation. Plasma p-tau217, p-tau181, Aβ42/40 ratio, brain-derived tau (BD-tau), neurofilament light chain (NfL), and glial fibrillary acid protein (GFAP) were measured using Simoa. Median biomarker values in different groups were compared with Kruskal-Wallis test, and area under the receiver operating characteristic curve was used to compare accuracy in distinguishing prion diseases from sporadic AD (sAD). Lumipulse p-tau217 and NfL were measured in a validation study in a different laboratory. RESULTS: In the main study, we analyzed 345 samples from 278 individuals (mean age 58 [SD 13.5], 48.2% female), including 204 with prion diseases (121 sporadic Creutzfeldt-Jakob disease [CJD], 11 iatrogenic CJD, 9 variant CJD, 47 slow-progressing inherited prion disease (IPD) and 16 fast-progressing IPD), 33 with AD, and 41 healthy controls. For discriminating prion disease without AD copathology from sAD, none of p-tau217 (area under the curve [AUC] [95% CI] 0.605 [0.486-0.724]), p-tau181 (AUC 0.554 [0.446-0.661]), or GFAP (AUC 0.514 [0.389-0.640]) performed well. Aβ42/40 discriminated moderately (AUC 0.770 [0.684-0.856]). NfL/p-tau217 ratio (AUC 0.996 [0.987-1.000]), NfL (AUC 0.988 [0.974-1.000]), BD-tau/p-tau217 ratio (AUC 0.963 [0.929-0.996]), and BD-tau (AUC 0.934 [0.890-0.978]) discriminated very well. In an independent validation study, consecutive samples were analyzed from 32 patients with sAD and 35 patients with sporadic Creutzfeldt-Jakob disease (mean age 65.0 [SD 6.4], 56.7% female). NfL/p-tau217 again discriminated almost perfectly (AUC 0.986 [95% CI 0.966-1.000]). DISCUSSION: Plasma p-tau217 and p-tau181 are increased in both AD and prion diseases (regardless of burden of AD copathology). Diagnosing AD with a single abnormal p-tau plasma biomarker risks misdiagnosing prion diseases as AD. Plasma NfL/p-tau217 discriminates near-perfectly and could act as a flag to suspect prion diseases where this is a diagnostic possibility. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that plasma NfL/p-tau217 discriminates patients with CJD from those with AD.

Abstract Living at risk of a neurodegenerative condition such as inherited prion disease (IPD) is associated with substantial psychological burden, yet evidence-based supportive interventions are lacking. This unmet need is likely to grow as advances in biomarkers and predictive testing lead to increasing identification of individuals in pre-symptomatic stages of neurodegenerative disease. Acceptance and Commitment Therapy (ACT), a transdiagnostic intervention targeting psychological flexibility, has shown promise in chronic health contexts but has not been evaluated in individuals at genetic risk. We conducted a feasibility and acceptability study of a brief, group-based ACT intervention in adults at risk of IPD recruited through the UK National Prion Clinic. The intervention comprised a single 5-hour, face-to-face workshop followed by an individual booster session. Prespecified feasibility and acceptability criteria were assessed alongside secondary psychological outcomes at baseline, 1 month, and 3 months post-intervention, complemented by semi-structured qualitative interviews. Twenty-three participants completed the intervention. All predefined feasibility criteria were met, including recruitment (58%), intervention completion (80%), retention at 3 months (79%), and low missing data (10%). Acceptability was high, with all participants reporting the intervention as useful and appropriate. Quantitative analyses demonstrated improvements in psychological quality of life and behavioural awareness at 3 months, with larger effects observed in participants with elevated baseline depressive symptoms. Qualitative findings highlighted the importance of peer connection, experiential learning, and practical strategies for managing uncertainty. These findings demonstrate that a brief, hybrid ACT intervention is feasible and acceptable for individuals living at risk of IPD and provide preliminary evidence for improving psychological well-being. As the population of individuals identified as at risk for neurodegenerative disease continues to expand, scalable psychological interventions that address cost and time barriers may represent an important component of future clinical care.

Summary Cryo-electron microscopy (cryo-EM) studies of amyloid fibrils have revealed endpoint structures of disease-relevant filaments and polymorphic intermediates formed during in vitro assembly of prion-like proteins. However, how transmissible prion or prion-like amyloids evolve during de novo formation and maturation in living cells remains unknown. Here, using the yeast prion [ PSI + ] as a model, we isolated Sup35NM amyloid fibrils from successive stages of [ PSI + ] maturation in Saccharomyces cerevisiae and characterised their near-atomic structures and population-level structural diversity by combining cryo-EM and atomic force microscopy. We show that intermediate and mature states differ in predominant fibril structure and the regions of the Sup35 sequence incorporated into the core, and that structural diversity decreases during maturation. Curing of [PSI+] at the mature state by guanidine hydrochloride (GdnHCl), which selectively inhibits ATPase activity of the chaperone Hsp104, restored both the predominant intermediate amyloid structure and the broader structural diversity characteristic of the intermediate state. In addition, Hsp104, Ssa1 (Hsp70) and Sis1 (Hsp40) associate differently with fibrils from the two states. Together, these findings provide direct structural evidence for amyloid evolution in vivo and support a chaperone-mediated mechanism of conformer selection within a polymorphic amyloid population.

Mutational analysis of the cellular prion protein (PrPC) has revealed various regions of the protein that modulate prion propagation. However, these approaches involve deletions, insertions, or replacements in the presence of the WT PrPC, which may mask the true phenotype. Here, site-directed alanine mutagenesis of the prion protein (PrP) was conducted to identify sites, particularly potential "surface patches" of PrPC required for prion propagation. Mutations were targeted to the helical, sheet, and loop regions of PrPC, or a combination thereof and the mutated proteins expressed in mouse neuroblastoma cells in which the endogenous PrPC had been silenced. Using the scrapie cell assay, a highly sensitive cell culture-based bioassay for quantifying infectious titers of Rocky Mountain Laboratory (RML) prions, we found that all mutations within the structured 119 to 231 domain, irrespective of secondary structure, severely reduced prion propagation. We further analyzed four strongly inhibiting mutations within conformationally variable loop regions of PrPC-residues 123 to 125 (PRP1); 134 to 135 (PRP4); 139,141 (PRP5), and connecting helix residues 146 and 153, respectively, as well as residues 188,191 to 192 (PRP13). Mutations in PRP1, 4 and 5 dominantly inhibited prion propagation even in the presence of WT PrPC, while mutations in PRP13 had no comparable effect, suggesting that the former disrupt prion fibril structure or its replication mechanism. None of the most inhibitory mutations substantially altered PrP stability, and mutant PrPs were able to both form amyloid in vitro and seed fibril formation of WT PrP.

Seeded protein misfolding and aggregation are relevant to many neurodegenerative diseases. The archetype are prions: protein-only infectious agents that cause fatal neurodegenerative diseases including Creutzfeldt-Jakob disease (CJD). The recent recognition of iatrogenic amyloid β cerebral amyloid angiopathy (CAA) and Alzheimer's disease, caused by inadvertent seeding of amyloid β pathology following historical medical procedures, raises concerns that these conditions might also be transmitted via blood components and products, as was the case in rare instances for variant CJD. Recent epidemiological data showing the apparent transmission of haemorrhage risk between blood donors and recipients raise the possibility of blood-based CAA transmission. In this Viewpoint, we review the evidence for amyloid β transmission, provide an overview of relevant prion biology, and consider the circumstances under which bloodborne prion transmission has previously occurred. We discuss the implications for blood transfusion services, particularly in light of the UK Infected Blood Inquiry, and the key questions that need to be addressed to better quantify transfusion-related risk.

Prions are self-templating assemblies of the host prion protein in which conformational templating encodes heritable "strain" information. Human prion diseases, including Creutzfeldt-Jakob disease (CJD), are rare but uniformly fatal neurodegenerative disorders with established public-health relevance through epidemic and iatrogenic transmission and provide a paradigm for conformational templating in neurodegeneration. Mechanistic analysis of human prion propagation and development of infectivity assays for public health surveillance have been limited by the absence of mammalian cell systems that replicate authentic infectious human prions. Here, we establish a humanized neural cell system that enables propagation of variant CJD (vCJD) prions and reveals that prion replication is constrained by strain-compatible cellular states. The platform was generated using a silencing-followed-by-reconstitution strategy analogous to that used in transgenic mouse models of human prion disease, combined with high-throughput clonal selection. These cells propagate brain-derived vCJD prions and support chronic infection. Prions propagated in vitro transmit disease to humanized transgenic and wild-type mice while preserving defining biochemical and strain-specific neuropathological features, demonstrating faithful propagation. Propagation is strain specific: The cells are permissive to vCJD but refractory to sporadic CJD isolates, indicating that prion replication is constrained by strain-compatible cellular states. These humanized cells enable quantitative detection of infection at high dilution, support systematic genetic manipulation, and are readily adaptable to automation. By overcoming a longstanding barrier of propagating authentic human prions, this platform enables mechanistic dissection of the cellular determinants of prion replication and strain specificity and provides a scalable system for genetic analysis and sensitive detection of infectious human prions.

INTRODUCTION:Iatrogenic transmission of amyloid beta can cause cerebral amyloid angiopathy (CAA) and Alzheimer's disease (AD), but the relationship between these phenotypes is unclear. METHODS:We retrospectively analyzed standardized neuropsychological and neuroimaging data from 11 patients with iatrogenic CAA (iCAA). Brain MRI was assessed for medial temporal lobe atrophy (MTA), the posterior atrophy score for parietal atrophy, and global cortical atrophy (GCA). RESULTS:All patients (mean age 42 ± 8.3 years) had childhood neurosurgery; 91% had confirmed cadaveric dura exposure. Six patients (55%) presented with intracerebral hemorrhage, and none showed MTA, parietal atrophy, or GCA at presentation. Over a median 5-year follow-up, 8/11 (73%) developed atrophy on at least one score, moderate to severe in three patients. Cognitive impairment was present in 9/11 (82%) at a median 3-year follow-up. AD was confirmed histopathologically in 2/4 (50%) examined cases. DISCUSSION:Progressive brain atrophy and cognitive impairment are common in iCAA, suggesting frequent co-existing neurodegeneration and possible AD pathology. Vigilance for cognitive decline may enable earlier identification and management.

Prions are assemblies of misfolded proteins that cause transmissible, progressive neurodegenerative disease in humans and other mammals. Human prion diseases have particular public health and biological significance, both due to their transmissibility between hosts, and the mechanisms they share with many other neurodegenerative conditions. However, their study has been considerably impeded by the absence of a cell-based system capable of reproducibly propagating and quantifying bona fide human prion infectivity, which has been a goal for several decades. Here, we describe the first robust, cell-based assay of human prion infectivity in dividing cells. We found that CAD5 cells expressing human prion protein instead of the endogenous mouse prion protein, replicate human prion infectivity from brain samples of patients with sporadic Creutzfeldt-Jakob disease (sCJD) expressing valine at codon 129 of the prion protein gene. Moreover, these cells quantify human prion infectivity with similar sensitivity to the current gold standard animal bioassay, at a fraction of the cost and time, maintain persistent infection that can be cured with an anti-prion treatment, and can be adapted for therapeutic screening. This novel system permits direct cell-based quantification and investigation of human prion infectivity for the first time. ### Competing Interest Statement JC is a Director of D-Gen Ltd., an academic spin-out company working in the field of prion disease diagnosis, decontamination and therapeutics. D-Gen supplied the ICSM35 and ICSM18 antibodies used for western blot and Elispot assays performed in this study. The other authors declare no competing interests. Medical Research Council, https://ror.org/03x94j517, MR/P019862/1 National Institute for Health Research UCLH Biomedical Research Centre

Prions are assemblies of misfolded prion protein that cause several fatal and transmissible neurodegenerative diseases, with the most common phenotype in humans being sporadic Creutzfeldt-Jakob disease (sCJD). Aside from variation of the prion protein itself, molecular risk factors are not well understood. Prion and prion-like mechanisms are thought to underpin common neurodegenerative disorders meaning that the elucidation of mechanisms could have broad relevance. Herein we sought to further develop our understanding of the factors that confer risk of sCJD using a systematic gene prioritization and functional interpretation pipeline based on multiomic integrative analyses. We integrated the published sCJD genome-wide association study summary statistics with publicly available bulk brain and brain cell type gene and protein expression datasets. We performed multiple transcriptome and proteome-wide association studies and Bayesian genetic colocalization analyses between sCJD risk association signals and multiple brain molecular quantitative trait loci signals. We then applied our systematic gene prioritization pipeline to the obtained results and nominated prioritized sCJD risk genes with risk-associated molecular mechanisms in a transcriptome and proteome-wide manner. Genetic upregulation of both gene and protein expression of syntaxin-6 (STX6) in the brain was associated with sCJD risk in multiple datasets, with a risk-associated gene expression regulation specific to oligodendrocytes. Similarly, increased gene and protein expression of protein disulfide isomerase family A member 4 (PDIA4), involved in the unfolded protein response, was linked to increased disease risk, particularly in excitatory neurons. Protein expression of mesencephalic astrocyte derived neurotrophic factor (MANF), involved in protection against endoplasmic reticulum stress and sulfatide binding (linking to the enzyme in the final step of sulfatide synthesis, encoded by sCJD risk gene GAL3ST1), was identified as protective against sCJD. In total 32 genes were prioritized into two tiers based on the level of evidence and confidence for further studies. This study provides insights into the genetically-associated molecular mechanisms underlying sCJD susceptibility and prioritizes several specific hypotheses for exploration beyond the prion protein itself, as well as beyond the previously highlighted sCJD risk loci, through the newly prioritized sCJD risk genes and mechanisms. These findings highlight the importance of glial cells, sulfatides and the excitatory neuron unfolded protein response in sCJD pathogenesis.

Inherited prion diseases (IPDs) are phenotypically diverse neurodegenerative conditions caused by mutations in the prion protein gene (PRNP). We describe IPD due to a novel PRNP E146G mutation in a 50-year-old man presenting with slowly progressive dysarthria, prominent myoclonus especially in the lower limbs, and less prominent gait ataxia, pyramidal and extrapyramidal signs. Cognitive impairment was not overt at disease onset. MRI revealed cerebellar atrophy and white matter hyperintensities. His 46-year-old sister carries the mutation and has subtle gait ataxia and dysarthria. Both patients exhibit a distinctive fluid biomarker profile: in CSF S100B is > twofold upper limit of normal, total tau is moderately elevated, and neurofilament light chain, 14-3-3 and RT-QuIC are negative; in plasma there is marked elevation of GFAP but repeatedly normal neurofilament light chain. The proband’s father died aged 55 following an 8-year dementing illness with similar presentation. Post-mortem revealed cerebellar cortical atrophy and profuse large PrP amyloid plaques across cerebral and cerebellar grey matter. Immunoblotting identified low molecular weight protease-resistant PrP fragments. E146G mutation IPD broadly fits into the historical Gerstmann–Sträussler–Scheinker disease spectrum but, based on deep clinical phenotyping of this initial pedigree, we highlight some distinctive features, which may aid in identification of this disease.

The epizootic prion disease of cattle, bovine spongiform encephalopathy (BSE), caused variant Creutzfeldt-Jakob disease (vCJD) in humans following dietary exposure. Codon 129 polymorphism of the human prion protein gene (PRNP), encoding either methionine (M) or valine (V), dictates the propagation of distinct human prion strains and up to now all but one neuropathologically confirmed vCJD patients have had a 129MM genotype. Concordant with this genetic association, transgenic modelling has established that human PrP 129V is incompatible with the vCJD prion strain and that depending on codon 129 genotype, primary human infection with BSE prions may, in addition to vCJD, result in sporadic CJD-like or novel phenotypes. In 2016 we saw the first neuropathologically confirmed case of vCJD in a patient with a codon 129MV genotype. This patient's neuropathology and molecular strain type were pathognomonic of vCJD but their clinical presentation and neuroradiological features were more typical of sporadic CJD, suggestive of possible co-propagation of another prion strain. Here we report the transmission properties of prions from the brain and lymphoreticular tissues of the 129MV vCJD patient. Primary transmissions into transgenic mice expressing human PrP with different codon 129 genotypes mainly produced neuropathological and molecular phenotypes congruent to those observed in the same lines of mice challenged with prions from 129MM vCJD patient brain, indicative that the vCJD prion strain was the dominant propagating prion strain in the patient's brain. Remarkably however, some transgenic mice challenged with 129MV vCJD patient brain propagated a novel prion strain type which at secondary passage was uniformly lethal in mice of all three PRNP codon 129 genotypes after similar short mean incubation periods. These findings establish that cattle BSE prions can trigger the co-propagation of distinct prion strains in humans.