Chitinases are hydrolytic enzymes responsible for degrading chitin and have been evolutionarily conserved across various species. Although their signaling pathways are not fully understood, the chitinases are considered active immunomodulators across several cell types. Specific isoforms, including Chitotriosidase-1 (CHIT1), Chitinase-3-like protein 1 (CHI3L1), and human-specific Chitinase-3-like protein 2 (CHI3L2), have emerged as markers of inflammation across the neurodegenerative spectrum, including amyotrophic lateral sclerosis (ALS). ALS is a fatal neuromuscular condition, and therapeutic development has been severely hindered by phenotypic heterogeneity and an incomplete understanding of etiology. Although several overlapping disease mechanisms can contribute to neuronal death, inflammation can exacerbate pathology. Prior studies have reported that CHIT1, CHI3L1, and CHI3L2 levels are elevated in the cerebrospinal fluid (CSF) of ALS patients and associated with disease aggressiveness. Nevertheless, several open questions critical to our understanding of the chitinases' role in ALS disease burden remain: namely, 1) which cell types in the central nervous system (CNS) are chitinase sources under physiological conditions, 2) which of these display chitinase upregulation in ALS, and 3) what is the diagnostic utility of the chitinases relative to established biomarkers. Here, we utilize pre-clinical models and post-mortem human tissue to demonstrate at both the transcriptomic and protein level that neurons are a primary source of chitinases; furthermore, neuronal chitinase expression is conserved across species. Under physiological conditions, CHI3L1 is more abundant and widely expressed across various cell types, whereas CHIT1 is predominantly expressed in neurons. Additionally, utilizing symptomatic mice from three familial ALS models, we demonstrate isoform-specific expression profiles, with astroglial and microglial upregulation of CHI3L1, and neuronal and microglial upregulation of CHIT1. Differing expression dynamics and diagnostic utility were also noted in our clinical cohort: CSF CHIT1 and CHI3L2 levels had more discriminatory power when distinguishing between ALS vs. non-ALS controls, while CHI3L1 was more closely associated with inflammation and aging across the neurodegenerative spectrum. Although the chitinases did not diagnostically outperform the neurofilament proteins as biomarkers, we propose that appreciating their expression patterns can aid in optimizing biomarker-guided trial design. Taken together, we demonstrate that chitinase upregulation in ALS is evident in various CNS cell types and that its neuronal expression may provide new insights into its role in disease activity.

Synaptic loss is an early hallmark of Alzheimer's disease (AD), predominantly driven by aberrant microglial reactivity. Pioglitazone, a peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist with anti-diabetic properties, has been shown to suppress microglial activity and improve cognitive performance in both AD models and clinical studies. However, whether its neuroprotective effects involve direct modulation of synaptic architecture remains unclear. Here, using longitudinal in vivo two-photon imaging, multi-channel immunohistochemistry, super-resolution confocal microscopy and three-dimensional reconstruction techniques in an AD mouse model, we analyse synaptic and microglial interactions. We show that a 4-week pioglitazone treatment preserves dendritic spine density and enhances spine stability over time. Mechanistically, pioglitazone reduces synaptic C1q deposition, thereby limiting complement-mediated microglial synaptic engulfment and attenuating synapse loss. These findings identify pioglitazone as a modulator of complement-dependent microglial synaptic pruning and support its therapeutic potential in preserving synaptic integrity during early AD pathogenesis.

Microglia are innate immune cells of the central nervous system (CNS). They extend their processes and migrate toward injuries in vivo. However, how the fractalkine receptor (CX3CR1) influences microglial migration remains unknown. Label-free proteomic profiling predicted changes in Ras homology family (RHO)-signaling activity that hint at dysregulated cytoskeleton signaling in Cx3cr1-deficient murine cortex tissue. To further investigate microglial migration, we carried out two-photon in vivo imaging at 4-h intervals for 72 h after a laser lesion in the cortex. Cx3cr1-deficient microglia showed enhanced migration toward the lesion. Additionally, the length and velocity of microglial fine processes extending toward the lesion were increased in Cx3cr1-deficient microglia. Migration remained unchanged in Ccr2-deficient mice, indicating that monocyte-derived macrophages/microglia did not contribute to microglia accumulation around the lesion. These results demonstrate that CX3CR1 modulates microglia migration toward laser-induced CNS injury. Manipulating microglia migration via the CX3CR1 signaling axis is therefore a potential target for the treatment of CNS injury.

Neurodegenerative diseases are characterised by the assembly of a limited number of disease-specific proteins into amyloid filaments, which form intracellular inclusions or extracellular deposits in the central nervous system (CNS)1,2. We previously found that amyloid filaments of TATA-binding protein-associated factor 15 (TAF15) characterise a subtype of frontotemporal lobar degeneration with FET protein-immunoreactive inclusions (FTLD-FET)3, termed atypical FTLD with ubiquitin-positive inclusions (aFTLD-U)4, which causes early-onset, rapidly progressive behavioural variant frontotemporal dementia (FTD). However, it was not clear if TAF15 proteinopathy was more widespread in neurodegenerative diseases. Two additional FTLD-FET subtypes have been proposed, neuronal intermediate filament inclusion body disease (NIFID) and basophilic inclusion body disease (BIBD)5,6, which have more heterogenous clinical presentations including FTD, motor neuron diseases (MND) and movement disorders. Here, we used electron cryo-microscopy (cryo-EM) to determine a total of 32 amyloid filament structures from the brains of 17 individuals encompassing all three proposed subtypes of FTLD-FET and their diverse clinical presentations. All cases were characterised by TAF15 filaments, in the absence of filaments of the other FET proteins, fused in sarcoma (FUS) and Ewing's sarcoma (EWS). All three aFTLD-U cases had the previously-reported TAF15 fold3. Unexpectedly, we found four distinct TAF15 folds among 11 NIFID cases. Eight of these cases shared a common fold, while the remaining three were each distinct. Furthermore, we found distinct TAF15 folds for each of the three BIBD cases. Neuropathological reassessment of the neocortical TAF15 inclusion pathology of these cases distinguished the NIFID cases with the common fold from the others. Thus, TAF15 filament structures form the basis of a new, expanded classification of FTLD-FET subtypes. Moreover, we discovered a TAF15 Y38C variant in the filament fold of one of the individuals with BIBD. The structure is unable to incorporate wild-type TAF15, despite the individual being heterozygous, suggesting that this variant drives TAF15 filament assembly. This study provides structural and genetic evidence that TAF15 amyloid filaments underlie the diverse group of neurodegenerative diseases currently termed FTLD-FET, which we therefore rename FTLD-TAF15.

The combination of brain glucose hypometabolism and hyperphosphorylated Tau (p-Tau) pathology is the strongest known clinical predictor of imminent cognitive decline, yet how these factors cooperate to drive dementia remains unknown. Here, we show that glucose hypometabolism synergizes with p-Tau to trigger neuronal loss through necroptosis. Under low-glucose conditions, accumulated p-Tau forms a molecular scaffold that directly recruits RIPK1, while concomitant loss of the necroptosis checkpoint A20 removes a critical brake on this death pathway. This dual mechanism thereby precipitates neuronal necroptosis. Restoring A20 expression with acetyl-L-carnitine or preventing the p-Tau-RIPK1 interaction using a RIPK1-derived competitive peptide alleviates neuronal necroptosis and brain atrophy in a Tau transgenic mouse model. Collectively, our findings uncover a previously unrecognized metabolism-driven necroptotic signaling cascade initiated by a p-Tau-RIPK1 hub, providing mechanistic insight into how glucose hypometabolism synergizes with p-Tau to drive neurodegeneration.

OBJECTIVES:Amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) share neuropathological features, including tau, amyloid, and TDP-43 pathology. This study investigated whether AD-related pathological changes are associated with cognitive impairment ALS. METHODS:Cerebrospinal fluid (CSF total-tau, phosphorylated-tau, beta-amyloid) and plasma biomarkers (TDP-43; neurofilament light chain [NfL]) were analyzed in 192 individuals with ALS or ALS with frontotemporal dementia (ALS-FTD) and 100 healthy controls. Cognitive performance was assessed using the Edinburgh Cognitive and Behavioral ALS Screen (ECAS). Group comparisons and regression analyses examined associations between biomarker profiles and cognitive status. Autopsy data were available for a subset of participants. RESULTS:Compared with healthy controls, patients with ALS - particularly those with cognitive impairment (ALSci) or ALS-FTD - showed elevated AD-related biomarkers. Significant differences in beta-amyloid levels were observed between healthy controls (HCs) and patients with ALSci, but not between controls and cognitively unimpaired patients. CSF p-tau and total-tau levels were strongly associated with domain-specific cognitive performance. In contrast, plasma extracellular vesicle TDP-43 and NfL showed weak or no association with cognition. In vivo biomarkers alone reliably distinguished cognitive impairment only in ALSci and ALS-FTD. Postmortem analyses showed no strong association between ABC scores or overall TDP-43 burden and cognitive state; however, temporal and hippocampal TDP-43 burden was associated with cognitive dysfunction. INTERPRETATION:Our findings suggest that tau-related CSF biomarkers, particularly p-tau and total-tau, are associated with cognitive deficits in ALS, indicating that AD-related pathology might be associated to cognitive decline in ALS. However, postmortem data showed even stronger relation of TDP43 pathology to cognitive deficits in ALS. ANN NEUROL 2026;100:123-138.

Abstract Amyloid beta (Aβ) plaque deposition in the central nervous system (CNS) is a hallmark of Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA), triggering robust innate immune responses. However, the role of the adaptive immune system remains less well understood. Here we show the immune microenvironment dynamics in APP23 transgenic (APP23-tg) mice modelling CNS amyloid pathology, using single-cell transcriptomics. We observed a marked increase in T-cell populations during late disease stages, particularly CD8⁺ T-cells that clustered around Aβ plaques, suggesting a targeted immune response. Among these, we identified an Aβ plaque-associated subset of CD8⁺ T cells expressing interferon-stimulated genes (ISGs), which promoted Type-I interferon signaling. This subset also produced CXCL10, facilitating the recruitment of non-ISG T cells through the CXCL10-CXCR3 axis. Importantly, similar Type-I interferon responses were detected near plaques in human CNS amyloid pathology. Together, these findings highlight a shift from microglia-driven to T-cell-mediated neuroinflammation as amyloid pathology progresses, with implications for time-resolved therapy development.

Recent advances in anti-amyloid therapies for Alzheimer's disease have been promising, but they have also highlighted critical challenges, including increased vascular complications, such as amyloid-related imaging abnormalities. Emerging evidence suggests that the soluble epoxide hydrolase may be a promising therapeutic target due to the involvement of sEH-derived diols in inflammation, oxidative stress, and vascular destabilization. APPPS1 mice, a model of amyloidosis, were crossed with an inducible soluble epoxide hydrolase knock-out mouse line. The knock-out was induced before onset of amyloid deposition, and then the mice were analyzed using histological, molecular, and RNA sequencing techniques. Here, we identify astrocytic soluble epoxide hydrolase as a key mediator of vascular instability in amyloid pathology. Targeted astrocyte-specific deletion of soluble epoxide hydrolase in APPPS1 mice dramatically mitigated vascular changes, reducing the vascular amyloid burden by 67.95% and preserving VE-cadherin architecture. Importantly, vasomotion was markedly impaired in the Alzheimer's disease model and was preserved in soluble epoxide hydrolase-deficient animals. Transcriptomic profiling of vasculature in APPPS1xsEHΔAC mice revealed upregulated expression of genes critical for neurovascular protection. These findings identify soluble epoxide hydrolase as a central regulator of neurovascular dysfunction and underscore its therapeutic potential in increasing vascular stability in amyloidosis-associated diseases, such as Alzheimer's disease.

Stem-cell-based in vitro models offer promising potential to elucidate human brain cell functions and interactions under physiological and pathological conditions. However, harnessing this potential is impaired by low reproducibility, maturity, or cell-type diversity of existing models. Especially, prolonged incorporation of mature microglia and studies of neuroinflammation have proven challenging. Here, we developed a 3D cortical brain tissue model (3BTM) containing neurons, astrocytes, and microglia with high reproducibility, maturity, and viability. 3BTMs show morphological, functional, and proteomic maturation of all cell types, leading to high similarity to their in vivo counterparts. Incorporated microglia survive for over 6 months and display mature morphology, functions, and gene expression. Importantly, when engineered to model Alzheimer's disease (AD) pathology, 3BTMs recapitulate key disease hallmarks including amyloid deposition, increased phospho-Tau levels, and neuroinflammation, with microglia shifting their transcriptional landscape to disease-relevant signatures. Treatment of AD 3BTMs with anti-Aβ immunotherapy cleared deposits and largely reversed disease signatures in glia. Together, our model offers unprecedented possibilities for studying physiological and pathological states of human brain tissue and translational applications. ### Competing Interest Statement J.K., C.C.G., and D.P. have filed a patent application covering generation, maintenance, and applications of 3BTMs. D.P. is an advisor to ISAR Bioscience GmbH, Planegg. All other authors declare no competing interests. Deutsche Forschungsgemeinschaft, https://ror.org/018mejw64, EXC2145, ID 390857198, EXC2151, ID 390873048, TRR 274/1,2 project Z01 – ID 408885537 BrightFocus Foundation, ADR AD2019604S Centers of Excellence in Neurodegeneration, CoEN6005 Bundesministerium für Bildung und Forschung, FKZ: 16LW0473, FKZ: 01ED2402A Ministry of Culture and Science of North Rhine-Westphalia

INTRODUCTION:Progressive supranuclear palsy (PSP), a 4-repeat tauopathy, can be visualized using [18F]PI-2620 tau positron emission tomography (PET). However, the value of sequential [18F]PI-2620 imaging for tracking tau accumulation during the disease course has not yet been investigated. METHODS:Twenty-three PSP patients underwent two [18F]PI-2620 PET scans (interval: 21.4 ± 4.3 months) and were compared to cross-sectional data from 25 healthy controls. Regional volume of distribution ratio values were analyzed for longitudinal tau changes, clinical correlations, and network-based propagation. Post mortem analyses examined neuronal density and AT8 tau pathology. RESULTS:Subcortical tau PET signals increased, strongest in the globus pallidus internus (P < 0.0001). Patients with low baseline tau showed the largest increases. Despite clinical worsening (Progressive Supranuclear Palsy Rating Scale +48%), tau PET change did not correlate with symptom progression. Tau accumulation followed functional connectivity (R = 0.34, P < 0.0001). Post mortem data linked elevated tau PET to higher AT8 burden despite neuronal loss. DISCUSSION:[18F]PI-2620 PET enables monitoring of tau progression in PSP, indicating network-based tau propagation with saturation in advanced stages.

Microglia are highly plastic cells that are capable of integrating subsequent insults. As the majority of Alzheimer’s Disease (AD) patients also show cerebrovascular pathology, we here aimed to dissect the interactions between AD and ischemic brain injury on the microglial response to amyloid beta (Aβ) pathology. Unexpectedly, ischemic stroke in the context of cerebral β-amyloidosis drives the emergence of a neuroprotective microglial phenotype characterized by an ApoE-enriched transcriptional state and enhanced lipid handling. These microglia promote the rapid formation of highly compact Aβ plaques that are relatively inert and strikingly reminiscent of those observed in cognitively resilient AD patients. Our findings thus reveal that the microglial response to Aβ pathology is not a fixed trajectory toward dysfunction, but retains a capacity for beneficial reprogramming when engaged by the appropriate stimulus. Beyond characterizing this comorbid state, our data identify specific molecular pathways, centered on ApoE, complement activation, and lysosomal processing, that may be amenable to therapeutic targeting to promote protective microglial function in AD.

Precision of clinical diagnosis in neurodegenerative diseases is critically important for clinical care and study recruitment. This study aimed to investigate the clinical accuracy using gold-standard neuropathological reference. Neuropathological diagnoses from the Neurobiobank München were correlated with real-world clinical diagnoses from hospitals in Germany. Accuracy metrics, including sensitivity, specificity, and area under the curve (AUC) of clinical diagnoses, were calculated. Among nine neuropathologically diagnosed neurodegenerative diseases (Alzheimer’s disease, argyrophilic grain disease, corticobasal degeneration, frontotemporal lobar degeneration, Huntington’s disease, Lewy body disease, motor neuron disease, multiple system atrophy, and progressive supranuclear palsy) with a total of 455 cases, clinical sensitivity varied widely (0–100

Background. Progressive supranuclear palsy (PSP) is a primary tauopathy defined by the accumulation of 4R tau isoforms in neurons, oligodendrocytes and astrocytes. Despite evidence of genetic susceptibility operating through glial cell types, it remains poorly understood how cell type-specific epigenetic-transcriptional programs evolve with progression of tau pathology. Methods. We conducted single-nucleus chromatin accessibility (snATACseq) and RNA sequencing (snRNAseq) on postmortem frontal cortex samples from PSP patients (n = 8) and matched controls (n = 8), yielding over 144,000 nuclei passing quality control. Tau pathology burden, including neurofibrillary tangles, coiled bodies, and tufted astrocytes, was quantified on AT8-immunostained sections from the same individuals. We integrated differential gene expression analysis, transcription factor motif enrichment, weighted gene co-expression network analysis, and pseudotime modeling anchored to cell type-specific tau pathology burden to delineate molecular pseudo-progression trajectories. Results. In eight cell types, 20 subclasses, and 70 subclusters, PSP brains displayed a selective depletion of certain excitatory deep-layer neurons and oligodendrocyte subclusters, with relative preservation of inhibitory neurons and vascular cells. Genetic risk enrichment was localized to astrocytes and oligodendrocytes, whereas excitatory neurons exhibited the greatest transcriptional dysregulation. Oligodendrocyte pseudo-progression indicated a transition from homeostatic myelination programs (MBP, MOBP) through glucocorticoid-responsive stress (FKBP5, ZBTB16), to compensatory myelination (PLP1, CNP) and proteostasis stress (UCHL1, CYRAB, CLU). Neuronal pseudo-progression revealed early dysregulation of synaptic (RORB2, NRG3, NPTX1), microtubule dynamics (KIF2C, RAB27B, TUBA/B), and survival (MEG3, FTX) pathways, alongside a transient increase in neuron-glia interactions (GRIP, CNTNAP4, ERBB4), converging late on ribosomal translation and vesicular trafficking modules across all neuronal subtypes. Cross-modal integration with independent cerebrospinal fluid proteomics identified a concordant subset of glial reactivity, axonal injury, and synaptic markers jointly dysregulated in inhibitory neurons, oligodendrocytes, and excitatory deep-layer neurons. Conclusion. PSP pathogenesis reflects a combination of glial genetic susceptibility and staged, cell type-specific transcriptional dysfunction. Oligodendrocytes transition from myelination-competent states to FKBP5-mediated stress states, while neurons show variably timed loss of synaptic excitability and survival programs, preceded by neuron-glia interactions and followed by convergent ribosomal-proteostatic failure. These cytopathology-anchored trajectories outline a potential pathophysiological sequence and may inform candidate selection for stage-specific therapeutic interventions in PSP.

Stem-cell-based in vitro models offer promising potential to elucidate human brain cell functions and interactions, but limitations in reproducibility, maturation and cell-type diversity persist. Especially, prolonged incorporation of mature microglia and studies of neuroinflammation have proven challenging. Here, we developed a human induced pluripotent stem cell-based three-dimensional cortical brain tissue model (3BTM) containing neurons, astrocytes and microglia with high reproducibility, maturity and viability. 3BTMs show morphological, functional and proteomic maturation of all cell types, leading to high similarity to their in vivo counterparts. Incorporated microglia survive for over 6 months and display mature morphology, functions and gene expression. Importantly, when engineered to model Alzheimer's disease pathology, 3BTMs recapitulate key disease hallmarks, including amyloid deposition, increased phospho-tau levels and neuroinflammation, with microglia shifting their transcriptional landscape to disease-relevant signatures. Treatment of Alzheimer's disease 3BTMs with anti-Aβ immunotherapy cleared deposits and largely reversed disease signatures in glia. Together, our microglia-containing model provides a platform for studying physiological and pathological states of human brain tissue.

Abstract Parkinson’s disease (PD) is characterized by degeneration of dopaminergic neurons in the substantia nigra pars compacta, but the molecular events preceding neuronal loss remain unclear. Here, we combine spatial transcriptomics, spatial proteomics, and α-synuclein (αSyn) seed amplification assays to profile post-mortem midbrain tissue from controls, incidental Lewy body disease (iLBD), PD, Alzheimer’s disease (AD), and AD with Lewy body pathology (AD + LBP). We find that αSyn seeding activity correlates with dopaminergic neuron loss in PD-spectrum cases but not in AD-associated LBP, indicating disease-context dependent relationships between αSyn pathology and neurodegeneration. In iLBD, before overt substantia nigra Lewy pathology or detectable αSyn aggregation, we detect increased expression of the complement component C1QC together with loss of inhibitory synaptic markers. These findings support early complement-associated remodeling of inhibitory synapses as a potential pathogenic event preceding overt αSyn aggregation and neuronal degeneration in PD.

Atypical frontotemporal lobar degeneration with ubiquitin-positive inclusions (aFTLD-U) is neuropathologically characterized by aggregation of the FET family of proteins and clinically manifests as sporadic young-onset frontotemporal dementia. Here we describe a major risk locus on chr15q14 identified through a genome-wide association study in 59 pathologically confirmed aFTLD-U cases and 3,153 controls (lead single nucleotide polymorphism rs549846383, P = 5.85 × 10-21, odds ratio 26.7). When combined with data from 28 additional aFTLD-U cases, 3,712 controls and 3,215 individuals with other neurodegenerative diseases and by leveraging in-house and public long-read genome sequencing data from 1,715 individuals, we identified a tandem repeat expansion on the associated haplotypes in an intron of GOLGA8A. We found variation in repeat length, motif length, and motif sequence, with long CT-dimer expansions strongly associated with aFTLD-U. Although the functional consequence of this repeat remains unknown, its presence in nearly 60% of aFTLD-U cases points to a fundamental role in disease pathogenesis.

The molecular basis for accelerated cognitive decline seen in Alzheimer's Disease (AD) cases presenting with cortical alpha-Synuclein (⍺-Syn) co-pathology is not well understood. We show that such co-pathology brains express higher levels of microtubule- associated protein tau and that increasing ⍺-Syn expression is sufficient to drive tau accumulation. Our results reveal a hitherto unknown link between the pathogenesis of AD and Parkinson's Disease whereby tau and ⍺-Syn synergistically drive dementia-related pathology. ### Competing Interest Statement The authors have declared no competing interest.

The molecular basis for accelerated cognitive decline seen in Alzheimer's Disease (AD) cases presenting with cortical alpha-Synuclein co-pathology is not well understood. Mouse experiments have shown adverse interactions between tau (encoded by MAPT ) and alpha-Synuclein (encoded by SNCA ), but how this finding translates to humans from a genome-centered point of view remains unknown. Whole genome sequencing was performed on 137 neuropathologically defined AD cases, 36 of which presented with neocortical alpha-Synuclein co-pathology (Braak stage 6). Polygenic risk scores were calculated. Single-nucleus RNA sequencing and Western Blot data were collected from post-mortem tissue. Transcriptomic and proteomic results were validated in the MSBB cohort ( n  >300). Cellular, molecular and epigenetic consequences were assessed in isogenic iPSCs-derived neurons carrying a triplication of SNCA (AST) or a normal SNCA copy number (CAS). AD brains with alpha-Synuclein co-pathology had significantly higher polygenic risk scores for Parkinson's Disease, which could be partially explained by variants associated with higher expression of SNCA . Single-nucleus RNA sequencing and immunoblot analysis revealed a higher expression of MAPT and phosphorylated tau in alpha-Synuclein co-pathology cases. Protein and mRNA expression of MAPT and SNCA were positively correlated in the MSBB cohort. The employed iPSCs differentiation protocol accelerated neuronal maturation due to transient inhibition of EZH2 . Day50 AST neurons exhibited significantly increased pathological tau and alpha-Synuclein at both the RNA and protein levels compared to CAS neurons. AST neurons also showed highly activated GSK3β and decreased PSD95 (post-synaptic protein) in the immunofluorescence and immunoblot analyses. ATAC profiles identified dysregulated accessibility in the cAMP signaling pathway, as well as pathways related to axon guidance, postsynaptic density, and calcium signaling, among others. We demonstrate that alpha-Synuclein co-pathology in AD is characterized by higher phosphorylated tau levels in patients and iPSC-derived neurons. Our results provide insights into the complex molecular processes through which alpha-Synuclein and tau synergistically drive dementia-related pathology.

Alpha-synuclein (α-syn) deposits are common in around half of the Alzheimer's disease (AD) cases. While direct and indirect protein interactions are suggested, the relationships between different protein aggregates remain poorly understood. Here, we aimed to characterize α-syn, amyloid beta (Aβ), and tau load distributions of AD patients. Protein deposits were automatically quantified with random forest pixel classifiers in immunohistochemical stains of up to 28 brain regions in 72 brains with advanced AD neuropathological change. α-syn-negative cases were distinguished from amygdala predominant, brainstem predominant, and cortical α-syn-positive cases. Relationships with age, sex, and ApoE genotype were examined. α-syn co-pathology was detected in 60% of AD cases, more frequently, although not significantly, in women. Half of these positive cases presented α-syn deposits in the cortex, around one-third predominantly in the amygdala, and the remaining cases primarily in the brainstem. A high α-syn load in the amygdala was associated with an increased cortical Aβ load. The cortical tau load was increased in the amygdala-predominant α-syn group, but decreased in the brainstem-predominant and cortical α-syn cases in comparison with α-syn-negative cases. ApoE4 was associated with higher hippocampal α-syn and cortical Aβ deposition. Younger age at death was associated with a focally higher Aβ and tau load. AD cases with cortical α-syn deposition tended to have a younger age at death. Here, we show that next to age, sex, and ApoE genotype, the α-syn distribution in AD is related to different Aβ and tau loads. This may have therapeutic relevance for identifying patients who respond to Aβ immunotherapy related to tau burden and underpin the need to define α-syn pathology and distribution in early disease stages.

Description of a patient with multiple sclerosis (MS) who underwent immunotherapy with ocrelizumab and suffered a severe course of tick-borne encephalitis (TBE): A 33-year-old man presented with acute cerebellitis with tonsillar herniation. The initial suspected diagnosis of TBE was confirmed after a significant diagnostic delay, likely caused by negative serological testing due to B-cell depletion from ocrelizumab treatment for underlying MS. TBE diagnosis was made using polymerase chain reaction (PCR) and oligo-hybrid capture metagenomic next-generation sequencing (mNGS) of cerebral spinal fluid and brain biopsy samples which yielded a near-full length TBE Virus (TBEV) genome.