Aims

The ongoing Auτonomy trial (NCT04619420) enrolls participants presenting with mild early symptomatic (prodromal or mild dementia) Alzheimer’s disease (early AD). The Janssen plasma p217+tau assay is used as a pre-screen for eligibility to proceed to tau PET to reduce participant burden and improve screening efficiency. Using all screening data available to date, we report on observed differences in plasma p217+tau levels by race and ethnicity amongst participants who were tau PET positive [table 1] and who constituted a group of 5 or more participants.

Methods

Associations were analyzed using a linear model of p217+tau in log (pg/ml) as a function of age, sex, Hispanic or Latino ethnicity, race, and screening levels of creatinine and body mass index (BMI). Significance was set at nominal p values < 0.05.

Results

Regression analysis showed plasma p217+tau had significant negative (age, BMI) and positive (creatinine) associations, with higher levels in females. Race significantly accounted for an additional 10% of the variance. Specifically, Asian participants had the highest average level of plasma p217tau+ followed by White, then Black or African American participants. No statistical significance was found for differences with Native Hawaiian or Other Pacific Islander or for Hispanic or Latino ethnicity.

Conclusions

We have found that plasma p217+tau levels are associated with age, BMI, and creatinine in concordance with the literature^[1,2,3], and are more elevated in females. Importantly, race was a significant additional contributing factor. This highlights the importance of gathering fluid biomarker data along with tau PET from large cohorts across the disease continuum to improve performance across diverse groups.

References: [1] Jack et al., Brain 2018. [2] Edwards L et al., Neurobiology of Aging 2021. [3] Binette et al. Alzheimer’s Dement. 2023

Aims

Currently there is no blood biomarker to define the prodromal phase of α-synucleinopathies or differentiate Lewy body pathology from alternative proteinopathies. We aimed to cleanly isolate L1CAM-positive neuronally-derived extracellular vesicles (L1EVs) from serum and investigate whether L1EV α-synuclein measurements identify individuals at risk of developing Parkinson’s disease and related dementia and/or stratify parkinsonian syndromes.

Methods

L1EVs were directly immunocaptured from serum using an improved methodology that was confirmed with size-exclusion chromatography, electron microscopy, immunoblotting and mass spectrometry. α-Synuclein and syntenin-1 were measured by electrochemiluminescence. Area under the ROC curve (AUC) with 95% CI evaluated biomarker performance. Probable prodromal Parkinson’s disease was determined using the updated MDS research criteria. Multiple linear regression model assessed the association between L1EV α-synuclein and prodromal markers.

Results

We analysed >1000 samples from 7 cohorts internationally. L1EV α-synuclein exhibited a consistent performance (AUC=0.86) in separating clinical Parkinson’s disease from controls across populations and differentiated Parkinson’s disease from other proteinopathies with AUC> 0.93 and from Multiple System Atrophy with AUC>0.90. A trained threshold of L1EV α-synuclein distinguished iRBD subjects from controls AUC>0.90. L1EV α-synuclein differentiated subjects with >80% probability of having prodromal PD from healthy control populations (AUC=0.90) irrespective of initial diagnosis or recruitment site. Subgroup analysis revealed that the presence of specific combinations of prodromal markers was associated with increased L1EV α-synuclein levels. L1EV α-synuclein was increased in at-risk subjects with a positive CSF α-synuclein seed amplification assay and was above the identified threshold in 80% of cases (n=40) that phenoconverted to Parkinson’s disease or related dementia.

Conclusions

Serum L1EV α-synuclein is a promising biomarker for the stratification of those at high risk of developing Parkinson’s and related dementia and their differentiation from other Parkinsonian syndromes.

Aims

Development of selective and specific PET tracers, based on diarylbisthiazole with high binding affinity to α-synuclein fibrils (α-syn), excellent selectivity over β-amyloid and tau fibrils and a suitable brain uptake kinetic.

Methods

We apply in silico approaches to design tracers with excellent binding properties and a favorable pharmacokinetics (PK). The precursors and ¹⁸F-labelled leads, with high affinity to α-syn and excellent selectivity synthesized to assess uptake kinetic and PET/CT in 12 weeks post intrastriatal injection of preparation of human aSYN preformed fibrils (PFF) mice.

The leads with appropriate PK and stability were studied within our translational research, screened via experimental lipophilicity and assays, plasma stability, biodistribution, in vivo metabolite analyses and postmortem autoradiography of human brain with α-Synucleinopathies.

Results

Autoradiography of promising tracers (K_i <3 nM and >>100 folds selectivity) show high density binding to α-Synucleinopathies in PD, DLB and MSA brains then confirmed by IHC. The most promising tracers showed initial brain uptakes of up to 7 %ID/g and with fast washout from brain at 120 mins p.i. down to 0.6 %ID/g and an excellent plasma and brain stability. The PET/CT and kinetic modelling results of the PFF mice show elevated tracer retention where α-synuclein aggregates are in left brain hemisphere including striatum and amygdala but not in WT mice which fit to to the immunohistochemical results showing abundant α-Synucleinopathies.

Conclusions

In silico rational design helped to develop groundbreaking and highly desirable, but as yet unmet, medical tool to detect and quantify the presence, severity, and regional distribution of α-syn and its clinical manifestations in individuals with α-synucleinopathies. The tracers with promising binding and selectivity encouraging us to study them by imaging in mice, NHP and first-in-human.

The project is supported by ParkinsonFonds-Deutschland.

Aims

Our group and others have previously reported an attenuation of age-related changes in cognitive performance and Alzheimer’s disease (AD) biomarkers measured in cerebrospinal fluid in the carriers of a functionally advantageous KL-VS variant (KL-VS_HET) of the KLOTHO gene. Here we examine whether KL-VS_HET attenuation of unfavorable age-related biomolecular changes can be detected in plasma biomarkers of significance to AD in a middle-aged and older cohort enriched for AD risk.

Methods

Cognitively unimpaired adults (N=309, Mean_AGE=65) from the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Research Center with available data of interest were included. Covariate-adjusted (sex, education, APOE4, family history of AD) multivariate regression examined relationships between age group (Younger (N=140); Older (N=158); mean split @Age≥65) and plasma biomarkers (Aβ40, Aβ42, pTau181, pTau217, pTau231, neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP)) and whether these relationships differed for KL-VS non-carriers [KL-VS_NC; N=212; Younger=89(41%); Older=123(58%)) and KL-VS_HET (N=86; Younger=51(59%); Older=35(41%)].

Results

In the pooled analyses, older age was associated with unfavorable profiles in all plasma biomarkers (all P's ≤ 0.001), except Aβ42 (P = 0.16). No associations were observed between plasma biomarkers and global cognition (MMSE) within the normal range of function (MMSE = 26-30; all P's ≥ 0.16). In the stratified analyses, KL-VS_NC continued to exhibit this age-related pattern of alteration in plasma biomarkers (all P's ≤ 0.009 except Aβ42 P = 0.63), which was attenuated in KL-VS_HET for Aβ40, Aβ40/42, and pTau181, pTau217 and pTau231(all P's ≥ 0.1).

Conclusions

Age-associated changes in plasma biomarkers of significance to AD were attenuated in carriers of a functionally advantageous KLOTHO variant. KL-VS heterozygosity seems to be protective against age-related biomolecular alterations known to confer risk for AD.

Aims

Rapidly progressive dementias (RPD) are a group of neurological disorders characterized by a rapid cognitive decline. Creutzfeldt-Jakob disease (CJD), the prototype of human prion disease, is the most common cause of neurodegenerative RPD with an estimated annual incidence of approximately 1-2 cases per million population. The diagnostic value of blood-based biomarkers for Alzheimer’s disease (AD) in RPD and CJD has not been fully explored. Here, we aimed to investigate the value of established plasma markers for AD in RPD and CJD.

Methods

We measured plasma brain-derived tau (BD-tau) and p-tau181 in 11 controls, 15 AD patients and 33 with RPD, of which 19 were CJD. We compared diagnostic perfomance of plasma BD-tau and p-tau181 with CSF T-tau and p-tau181 in the different diagnostic groups and explored the clinical value of the ratio CSF T-tau(p-tau181 and Plasma BD-tau/p-tau181.

Results

Plasma BD-tau differentiated AD from RPD and controls (p=0.002 and p=0.03 respectively), while plasma and CSF p-tau181 distinguished AD from RPDs (p<0.001) but not controls from RPD (p>0.05). The correlation CSF T-tau-plasma BD-tau was stronger (r=0.77, p<0.001), than the correlation CSF-plasma p-tau181 (r=0.26, p=0.04). The ratio BD-tau/p-tau181 performed equivalently to the CSF T-tau/p-tau181 ratio, differentiating AD from CJD (p<0.0001). These resuls show that plasma BD-tau and p-tau181 mimic their CSF corresponding markers. P-tau significantly increased in AD but not in RPD. Plasma BD-tau, like CSF T-tau, increases according to neurodegeneration intensity.

Conclusions

Taken together, our results indicate that these novel tau-related plasma markers might be useful tools to help clinicians to estimate noninvasively both the degree of neurodegeneration and the presence of AD-related pathology with relatively low cost and have a potential application for the first line screening and monitoring of a broad patient population with suspected RPD.

Aims

Neuropathological studies have reported concomitant Alzheimer’s disease (AD) and primary age-related tauopathy (PART) in Creutzfeldt-Jakob disease (CJD). However, established cerebrospinal fluid (CSF) phospho-tau181 (p-tau181), targeting mid-region-tau, is rarely increased in CJD. Since novel, N-terminal p-tau forms (p-tau231, p-tau217 and p-tau181) associate with early amyloid pathology, we investigated these biomarkers in autopsy-verified CJD with/without concomitant pathologies and compared with AD-MCI and AD-dementia.

Methods

CSF N-terminal p-tau181, p-tau217 and p-tau231 (in-house Simoa assays), as well as mid-region total-tau (t-tau) and p-tau181 (Innotest), were measured in patients with CJD (n=29), AD-dementia (n=75), mild cognitive impairment (MCI) due to AD (n=65), and subjective cognitive decline (SCD, n=28). Post-mortem examination in CJD patients was performed 1.3 (0.3-14.3) months after CSF collection and revealed no co-pathology in ten, concomitant AD in eight (CJD^+AD), PART in eight, and other co-pathologies in three CJD cases.

Results

Predictably, mid-region t-tau/p-tau181 ratio best separated CJD from AD (AUC=100%) due to markedly increased t-tau (28-fold) in CJD. N-terminal p-tau biomarkers were also elevated in CJD versus SCD (p<0.0001) with highest, 8-fold changes observed in p-tau217. N-terminal p-tau181 and p-tau231 were similar as in AD-MCI, while p-tau231 and p-tau217 did not differ between CJD and AD-dementia, which resulted in their modest and significantly lower diagnostic accuracy (AUC=67.5% and 65.5%, respectively) compared with mid-region biomarkers. N-terminal p-tau biomarkers correlated significantly with t-tau (Spearman’s rho=0.930, 0.656 and 0.813 for p-tau181, p-tau231, and p-tau217, respectively; p<0.0001). Considering co-pathology, N-terminal p-tau forms were highest in CJD^+AD.

Conclusions

Whilst traditional CSF t-tau and t-tau/p-tau181 ratio accurately differentiated between CJD and AD, different fold-changes of N-terminal p-tau biomarkers in CJD, which further increased in the presence of concomitant AD, suggest they concurrently reflect AD pathology and intensity of neurodegeneration in CJD.

Aims

Positron Emission Tomography (PET) ligands have advanced Alzheimer's disease (AD) diagnosis and treatment. We aim to elicudate the structural basis of MK-6240 PET in quantifying PHF deposits in AD using Cryo-EM.

Methods

Helical Reconstruction

Helical reconstruction was done using RELION 4.0.

Results

We started with a neuropathologically confirmed AD case. We selected frontal cortical tissue to purify AD filaments. Guided by autoradiography with [18F]MK-6240, dissected regions with high AD tau filament concentration and extracted sarkosyl-insoluble tau filaments using standard methods. Cryo-EM confirmed the presence of isolated tau filaments, and in vivo binding of the purified tau filaments to MK-6240 was validated by inoculation into the rat hippocampus.

The density corresponding to MK-6240 was discernible at 12.5 standard deviations above the noise, and the amino acid main chain was extended up to 16 standard deviations. Notably, MK-6240 molecules exhibited a 1:1 stoichiometry with tau monomer rungs.

We fit the atomic coordinates of MK-6240 within the largest non-protein density in the C-shaped cavity of each tau protofilament, predicting packing interactions with amino acids Q351 and I360, and a hydrogen-bond with K353. The alignment of the 6-Azaindole ring of MK-6240 near K353 was stabilized by an inter-residue ion pair with neighboring D358.

Conclusions

Our study represents the first examination of the molecular binding interface of PHFs derived from AD brain, complexed with MK-6240, a second-generation, high avidity tau-PET ligand. The binding mode involves specific amino acid contacts and a stacked arrangement with pi-pi aromatic interaction, reflecting a 1:1 stoichiometric ratio. This information elucidates the basis of MK-6240 PET in quantifying PHF deposits in AD and may facilitate the structure-based design of superior ligands against tau amyloids.

Aims

Parkinson’s disease (PD) pathology is hypothesized to spread through the brain via the connections between regions. We aimed to test this theory by (1) deriving a PD atrophy map from the largest imaging dataset in PD to date, and (2) relating this pattern to models of brain network architecture.

Methods

We analyzed structural MRI data from 3,048 PD patients and 1,234 healthy controls from 23 ENIGMA-Parkinson’s Study sites. Measures of regional cortical and subcortical morphometry were estimated, harmonized, and w-scored to generate PD-specific atrophy maps (adjusted for age, sex, and scanner site). Structural and functional connectivity data from the Human Connectome Project were used to generate normative reference networks. The PD atrophy pattern was then examined with three models: (1) regional degree centrality that defined hubs of brain connectivity, (2) epicentre likelihood that identified disease epicentres based on regional connectivity profiles, and (3) node-neighbourhood deformation that related regional and network atrophy.

Results

We observed widespread cortical and subcortical atrophy in PD, consistent with previous findings. Regional degree centrality was negatively correlated with PD atrophy, suggesting hub regions in the brain are more vulnerable to disease spread. Disease epicentres were identified in posterior parietal cortices and subcortical limbic regions. Finally, regional atrophy was positively correlated with mean atrophy across connected network neighbours. Importantly, our findings were significant when tested against spatial autocorrelation-preserving and randomly shuffled null models.

Conclusions

Taken together, our study demonstrates how brain network architecture shapes the pattern of atrophy in PD.