Plasma and cerebrospinal fluid tau and neurofilament concentrations in rapidly progressive neurological syndromes: a neuropathology-based cohort

SNAP-25: A biomarker of synaptic loss in neurodegeneration

Synaptic dysfunction is one of the most important markers of neurodegenerative diseases, which contribute to cognitive decline and the loss of neurons. Synaptosomal-associated protein 25 (SNAP-25) is a member of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, which plays a significant role in the exocytosis of synaptic vesicles and the release of neurotransmitters. Recent studies have shown that expression levels of SNAP-25 are altered in various neurodegenerative disorders, including Alzheimer's disease (AD), Huntington's disease (HD), and Creutzfeldt-Jakob disease (CJD). These investigations led to the consideration of SNAP-25 as a potential biomarker of synaptic degeneration. Understanding the role of SNAP-25 in neurodegeneration will aid in early diagnosis, disease monitoring, and therapeutic development, and will also provide new insights into synaptic dysfunction as a main feature of neurodegenerative diseases. Therefore, this paper explores the physiological role of SNAP-25, its involvement in synaptic pathology, and the implications of its dysregulation in neurodegenerative conditions, such as AD, HD, and CJD. Literature regarding cerebrospinal fluid (CSF) SNAP-25 levels as a diagnostic marker were reviewed and its applications in detecting the progression of the disease have been discussed. Additionally, the limitations of SNAP-25 as a biomarker, including variability across studies and the need for further validation have been addressed.

Alzheimer's disease neuropathology and its estimation with fluid and imaging biomarkers

Alzheimer's disease (AD) is neuropathologically characterized by the extracellular deposition of the amyloid-β peptide (Aβ) and the intraneuronal accumulation of abnormal phosphorylated tau (τ)-protein (p-τ). Most frequently, these hallmark lesions are accompanied by other co-pathologies in the brain that may contribute to cognitive impairment, such as vascular lesions, intraneuronal accumulation of phosphorylated transactive-response DNA-binding protein 43 (TDP-43), and/or α-synuclein (αSyn) aggregates. To estimate the extent of these AD and co-pathologies in patients, several biomarkers have been developed. Specific tracers target and visualize Aβ plaques, p-τ and αSyn pathology or inflammation by positron emission tomography. In addition to these imaging biomarkers, cerebrospinal fluid, and blood-based biomarker assays reflecting AD-specific or non-specific processes are either already in clinical use or in development. In this review, we will introduce the pathological lesions of the AD brain, the related biomarkers, and discuss to what extent the respective biomarkers estimate the pathology determined at post-mortem histopathological analysis. It became evident that initial stages of Aβ plaque and p-τ pathology are not detected with the currently available biomarkers. Interestingly, p-τ pathology precedes Aβ deposition, especially in the beginning of the disease when biomarkers are unable to detect it. Later, Aβ takes the lead and accelerates p-τ pathology, fitting well with the known evolution of biomarker measures over time. Some co-pathologies still lack clinically established biomarkers today, such as TDP-43 pathology or cortical microinfarcts. In summary, specific biomarkers for AD-related pathologies allow accurate clinical diagnosis of AD based on pathobiological parameters. Although current biomarkers are excellent measures for the respective pathologies, they fail to detect initial stages of the disease for which post-mortem analysis of the brain is still required. Accordingly, neuropathological studies remain essential to understand disease development especially in early stages. Moreover, there is an urgent need for biomarkers reflecting co-pathologies, such as limbic predominant, age-related TDP-43 encephalopathy-related pathology, which is known to modify the disease by interacting with p-τ. Novel biomarker approaches such as extracellular vesicle-based assays and cryptic RNA/peptides may help to better detect these co-pathologies in the future.

Challenges and Revisions in Diagnostic Criteria: Advancing Early Detection of Prion Diseases

Prion diseases are fatal neurological disorders characterized by abnormal protein accumulation in the brain, leading to neurodegeneration, dementia, and ataxia. Sporadic Creutzfeldt-Jakob disease (sCJD), the most common form, accounts for 80-90% of cases and progresses rapidly, with most patients surviving <6 months to a year after symptom onset, indicating the importance of early diagnosis. The disease is classified into six subtypes based on PRNP gene polymorphisms, with differences in protein degradation patterns contributing to the diversity of clinical symptoms. However, diagnosis remains challenging because of the variability in clinical presentation and disease duration. Traditional diagnostic criteria established by the World Health Organization (WHO) rely on clinical findings, electroencephalogram, and cerebrospinal fluid tests, such as the 14-3-3 protein assay. However, these criteria require pathological confirmation, often delaying diagnosis. The recently proposed Hermann's criteria represent a significant advancement by incorporating newer biomarkers, including magnetic resonance imaging, real-time quaking-induced conversion assay, tau protein, and neurofilament light chain. These criteria improve diagnostic sensitivity and specificity but have a slightly higher risk of false positives. This review compares the effectiveness of these biomarkers with the WHO criteria and highlights the importance of early diagnosis for improving patient care.

Characterizing plasma and cerebrospinal fluid biomarkers relevant to neurodegeneration in captive olive baboons (Papio anubis)

Alzheimer's disease and related dementias (ADRD) present a significant global disease burden that is only expected to grow in the future. As such, there is a need to develop and investigate biomarkers that identify individuals at risk of developing ADRD with the goal of providing early interventions and treatments. Non-human primate (NHP) models of neurodegeneration present opportunities to examine such biomarkers in a preclinical model with the ability to control several confounding factors present in research with humans. Baboons naturally develop several ADRD-related neuropathologies that humans also exhibit, including age-related tau and amyloid deposition. However, to our knowledge, there are no data characterizing fluid biomarkers relevant to neurodegeneration or ADRD in baboons. We collected plasma (N = 139) and cerebrospinal fluid (CSF, N = 44) from captive baboons ranging in age from 3-19 years old. We characterized biomarkers as a function of age, sex, and rearing status in baboons using a bead-based bioplex human assay (Thermo Fisher Scientific's Neuroscience 18-Plex Human ProcartaPlex™ Panel). Fluid biomarkers were more detectable in CSF compared to plasma. Additionally, while sex and rearing did not significantly predict biomarkers in baboons, age significantly predicted levels of eight of the 12 biomarkers detected in the assay. Linear regressions showed that CSF levels of total tau, pTau181, NGF-beta, GFAP, NF-H, and S100B were higher in older baboons, as were plasma levels of NGF-beta. Lastly, older baboons showed a higher incidence of co-occurrence of multiple biomarkers as measured in CSF, but not in plasma. These data show that baboons exhibit age-dependent changes in biomarkers used in humans for clinical screening, diagnosis, and prognosis of ADRD, thereby further demonstrating the value of baboons as a model of aging and, possibly, ADRD.

Molecular mechanisms of neurofilament alterations and its application in assessing neurodegenerative disorders

Neurofilaments are intermediate filaments present in neurons. These provide structural support and maintain the size and shape of the neurons. Dysregulation, mutation, and aggregation of neurofilaments raise the levels of these proteins in the blood and cerebrospinal fluid (CSF), which are characteristic features of axonal damage and certain rare neurological diseases, such as Giant Axonal Neuropathy and Charcot-Mare-Tooth disease. Understanding the structure, dynamics, and function of neurofilaments has been greatly enhanced by a diverse range of biochemical and preclinical investigations conducted over more than four decades. Recently, there has been a resurgence of interest in post-translational modifications of neurofilaments, such as phosphorylation, aggregation, mutation, oxidation, etc. Over the past twenty years, several rare disorders have been studied from structural alterations of neurofilaments. These disorders are monitored by fluid biomarkers such as neurofilament light chains. Currently, there are many tools, such as Enzyme-Linked Immunosorbent Assay, Electrochemiluminescence Assay, Single-Molecule Array, Western/immunoblotting, etc., in use to assess the neurofilament proteins in Blood and CSF. However, all these techniques utilize expensive, non-specific, or antibody-based methods, which make them unsuitable for routine screening of neurodegenerative disorders. This provides room to search for newer sensitive, cost-effective, point-of-care tools for rapid screening of the disease. For a long time, the molecular mechanisms of neurofilaments have been poorly understood due to insufficient research attempts, and a deeper understanding of them remains elusive. Therefore, this review aims to highlight the available literature on molecular mechanisms of neurofilaments and the function of neurofilaments in axonal transport, axonal conduction, axonal growth, and neurofilament aggregation, respectively. Further, this review discusses the role of neurofilaments as potential biomarkers for the identification of several neurodegenerative diseases in clinical laboratory practice.

Multifocal motor neuropathy as a mimic of amyotrophic lateral sclerosis: Serum neurofilament light chain as a reliable diagnostic biomarker

INTRODUCTION/AIMS

The clinical presentation of multifocal motor neuropathy (MMN) may mimic early amyotrophic lateral sclerosis (ALS) with predominant lower motor neuron (LMN) involvement, posing a diagnostic challenge. Both diseases have specific treatments and prognoses, highlighting the importance of early diagnosis. The aim of this study was to assess the diagnostic value of serum neurofilament light chain (NfL) in differentiating MMN from LMN dominant ALS.

METHODS

NfL was measured in serum in n = 37 patients with MMN and n = 37 age- and sex-matched patients with LMN dominant ALS, to determine the diagnostic accuracy. Clinical and demographic data were obtained at the time of NfL sampling.

RESULTS

Serum NfL concentration was significantly lower in MMN patients compared to ALS patients (mean 20.7 pg/mL vs. 59.4 pg/mL, p < .01). NfL demonstrated good diagnostic value in discriminating the two groups (AUC 0.985 [95% CI 0.963-1.000], sensitivity 94.6%, specificity 100%, cut-off 44.00 pg/mL).

DISCUSSION

NfL could be a helpful tool in differentiating MMN from LMN dominant ALS in those patients in whom electrophysiological and clinical examinations remain inconclusive early in the diagnostic process.

Temporal serum neurofilament light chain concentrations in sheep inoculated with the agent of classical scrapie

OBJECTIVE

Neurofilament light chain (Nf-L) has been used to detect neuroaxonal damage in the brain caused by physical injury or disease. The purpose of this study was to determine if serum Nf-L could be used as a biomarker for pre-symptomatic detection of scrapie in sheep.

METHODS

Four sheep with prion protein genotype AVQQ were intranasally inoculated with the classical scrapie strain x124. Blood was collected every 4 weeks until 44 weeks post-inoculation, at which point weekly collection commenced. Serum was analyzed using single molecule array (Quanterix SR-X) to evaluate Nf-L concentrations.

RESULTS

Scrapie was confirmed in each sheep by testing homogenized brainstem at the level of the obex with a commercially available enzyme immunoassay. Increased serum Nf-L concentrations were identified above the determined cutoff during the last tenth of the respective incubation period for each sheep. Throughout the time course study, PrPSc accumulation was not detected antemortem by immunohistochemistry in rectal tissue at any timepoint for any sheep. RT-QuIC results were inconsistently positive throughout the timepoints tested for each sheep; however, each sheep had at least one timepoint detected positive. When assessing serum Nf-L utility using receiver operator characteristic curves against different clinical parameters, such as asymptomatic and symptomatic (pruritus or neurologic signs), results showed that Nf-L was most useful at being an indicator of disease only late in disease progression when neurologic signs were present.

CONCLUSION

Serum Nf-L concentrations in the cohort of sheep increased as disease progressed; however, serum Nf-L did not increase during the presymptomatic window. The levels increased substantially throughout the final 10% of the animals' scrapie incubation period when other clinical signs were present. Serum Nf-L is not a reliable biomarker for pre-clinical detection of scrapie.

Plasma levels of phosphorylated tau and neurofilament light chain as potential biomarkers for Alzheimer's disease: A biochemical analysis in Pakistani population

The National Institute on Aging-Alzheimer's Association's research framework in 2018 proposed a molecular construct for the diagnosis of Alzheimer's disease (AD). Nonetheless, the clinical exclusionary strategy is still the mainstay of AD diagnosis in Pakistan. We looked at the plasma levels of amyloid beta-42 (Aβ-42), phosphorylated tau (P-tau), and neurofilament light (NFL) in patients with Alzheimer's clinical syndrome (ACS) and healthy controls (HC) from the Pakistani population to keep pace with the global efforts towards establishing accessible and affordable biochemical diagnostic markers for AD in Pakistan. Consultant neurologists screened patients who presented with cognitive impairment to three large tertiary care hospitals in Karachi, and after receiving informed consent, recruited participants with ACS and HC from the same facilities. We collected 5cc of blood in EDTA tubes along with demographic and lifestyle information of the subjects. Plasma aliquots were stored at -80°C after centrifugation. For analysis it was thawed at 4℃ and levels of the three proteins were measured through ELISA. Data from 28 ACS patients and 28 age matched healthy controls were evaluated. Among demographic factors, education and depression were related with health status (p = 0.03 and 0.003, respectively). NFL and P-tau mean values demonstrated a significant difference between the ACS and control groups (p = 0.003 and 0.006), however Aβ42 did not (p = 0.114). ROC analysis showed that plasma P-tau and NFL, with AUCs of 0.717 and 0.735, respectively, could substantially distinguish ACS from the HC group (p = 0.007 and 0.003, respectively). Both plasma P-tau (r = -0.389; p = 0.004) and NFL (r = -0.424; p = 0.001) levels were significantly and negatively correlated with individuals' MMSE scores. NFL and plasma P-tau show promise in differentiating AD patients from healthy individuals. However, similar larger studies are needed to validate our findings.

Blood Neurofilament Light Chain in Different Types of Dementia

AIMS

The study aimed to evaluate diagnostic values of circulating neurofilament light chain (NFL) levels in different types of dementia.

BACKGROUND

Previous studies reported inconsistent change of blood NFL for different types of dementia, including Alzheimer's disease (AD), frontotemporal dementia (FTD), Parkinson's disease dementia (PDD) and Creutzfeldt-Jakob disease (CJD) and Lewy body dementia (LBD).

OBJECTIVE

Meta-analysis was conducted to summarize the results of studies evaluating diagnostic values of circulating NFL levels in different types of dementia to enhance the strength of evidence.

METHODS

Articles evaluating change in blood NFL levels in dementia and published before July 2022 were searched on the following databases (PubMed, Web of Science, EMBASE, Medline and Google Scholar). The computed results were obtained by using STATA 12.0 software.

RESULTS

AD patients showed increased NFL concentrations in serum and plasma, compared to healthy controls (HC) (standard mean difference (SMD) = 1.09, 95% confidence interval (CI): 0.48, 1.70, I2 = 97.4%, p < 0.001). In AD patients, higher NFL concentrations in serum and plasma were associated with reduced cerebrospinal fluid (CSF) Aβ1-42, increased CSF t-tau, increased CSF p-tau, reduced Mini-Mental State Examination (MMSE) and decreased memory. Additionally, mild cognitive impairment (MCI) showed elevated NFL concentrations in serum and plasma, compared to HC (SMD = 0.53, 95% CI: 0.18, 0.87, I2 = 93.8%, p < 0.001). However, in MCI, no significant association was found between NFL concentrations in serum, plasma and memory or visuospatial function. No significant difference was found between preclinical AD and HC (SMD = 0.18, 95% CI: -0.10, 0.47, I2 = 0.0%, p = 0.438). FTD patients showed increased NFL concentrations in serum and plasma, compared to HC (SMD = 1.08, 95% CI: 0.72, 1.43, I2 = 83.3%, p < 0.001). Higher NFL concentrations in serum and plasma were associated with increased CSF NFL in FTD. Additionally, the pooled parameters calculated were as follows: sensitivity, 0.82 (95% CI: 0.72, 0.90); specificity, 0.91 (95% CI: 0.83, 0.96). CJD patients showed increased NFL concentrations in serum and plasma, compared to HC. No significant difference in NFL level in serum and plasma was shown between AD and FTD (SMD = -0.03, 95% CI: -0.77, 0.72, I2 = 83.3%, p = 0.003).

CONCLUSION

In conclusion, the study suggested abnormal blood NFL level in AD and MCI, but not in preclinical AD. FTD and CJD showed abnormal blood NFL levels.

Development and Characterization of Mouse-Specific Anti-Tau Monoclonal Antibodies: Relevance for Analysis of Murine Tau in Cerebrospinal Fluid

BACKGROUND

Clearance of tau seeds by immunization with tau antibodies is currently evaluated as therapeutic strategy to block the spreading of tau pathology in Alzheimer's disease and other tauopathies. Preclinical evaluation of passive immunotherapy is performed in different cellular culture systems and in wild-type and human tau transgenic mouse models. Depending on the preclinical model used, tau seeds or induced aggregates can either be of mouse, human or mixed origin.

OBJECTIVE

We aimed to develop human and mouse tau-specific antibodies to discriminate between the endogenous tau and the introduced form in preclinical models.

METHODS

Using hybridoma technology, we developed human and mouse tau-specific antibodies that were then used to develop several assays to specifically detect mouse tau.

RESULTS

Four antibodies, mTau3, mTau5, mTau8, and mTau9, with a high degree of specificity for mouse tau were identified. Additionally, their potential application in highly sensitive immunoassays to measure tau in mouse brain homogenate and cerebrospinal fluid is illustrated, as well as their application for specific endogenous mouse tau aggregation detection.

CONCLUSION

The antibodies reported here can be very important tools to better interpret the results obtained from different model systems as well as to study the role of endogenous tau in tau aggregation and pathology observed in the diverse mouse models available.

Brain atrophy and white matter hyperintensities are independently associated with plasma neurofilament light chain in an Asian cohort of cognitively impaired patients with concomitant cerebral small vessel disease

Introduction

Plasma neurofilament light chain (NfL) is a potential biomarker for neurodegeneration in Alzheimer's disease (AD), ischemic stroke, and non-dementia cohorts with cerebral small vessel disease (CSVD). However, studies of AD in populations with high prevalence of concomitant CSVD to evaluate associations of brain atrophy, CSVD, and amyloid beta (Aβ) burden on plasma NfL are lacking.

Methods

Associations were tested between plasma NfL and brain Aβ, medial temporal lobe atrophy (MTA) as well as neuroimaging features of CSVD, including white matter hyperintensities (WMH), lacunes, and cerebral microbleeds.

Results

We found that participants with either MTA (defined as MTA score ≥2; neurodegeneration [N]+WMH-) or WMH (cut-off for log-transformed WMH volume at 50th percentile; N-WMH+) manifested increased plasma NfL levels. Participants with both pathologies (N+WMH+) showed the highest NfL compared to N+WMH-, N-WMH+, and N-WMH- individuals.

Discussion

Plasma NfL has potential utility in stratifying individual and combined contributions of AD pathology and CSVD to cognitive impairment.

Cerebrospinal fluid neurofilament dynamic profiles predict cognitive progression in individuals with de novo Parkinson's disease

Background

Neurofilament light chain protein (NfL) in cerebrospinal fluid (CSF) reflects the severity of neurodegeneration, with its altered concentrations discovered in Parkinson's disease (PD) and Parkinson's disease dementia (PD-D).

Objective

To determine whether CSF NfL, a promising biomarker of neuronal/axonal damage, can be used to monitor cognitive progression in de novo Parkinson's disease and predict future cognitive decline.

Methods

A total of 259 people were recruited in this study, including 85 healthy controls (HC) and 174 neonatal PD patients from the Parkinson's Progression Markers Initiative (PPMI). Multiple linear regression and linear mixed effects models were used to examine the associations of baseline/longitudinal CSF NfL with cognitive decline and other CSF biomarkers. Kaplan-Meier analysis and log-rank test were used to compare the cumulative probability risk of cognition progression during the follow-up. Multivariate cox regression was used to detect cognitive progression in de novo PD.

Results

We found PD patients with mild cognitive impairment (PD-MCI) was higher than with normal cognition (PD-NC) in terms of CSF NfL baseline levels (p = 0.003) and longitudinal increase rate (p = 0.034). Both baseline CSF NfL and its rate of change predicted measurable cognitive decline in de novo PD (MoCA, β = -0.010, p = 0.011; β = -0.0002, p < 0.001, respectively). The predictive effects in de novo PD patients aged >65, male, ill-educated (<13 years) and without carrying Apolipoprotein E ε4 (APOE ε4) seemed to be more obvious and reflected in more domains investigated. We also observed that CSF NfL levels predicted progression in de novo PD patients with different cognitive diagnosis and amyloid status. After an average follow-up of 6.66 ± 2.54 years, higher concentration above the median of baseline CSF NfL was associated with a future high risk of PD with dementia (adjusted HR 2.82, 95% CI: 1.11-7.20, p = 0.030).

Conclusion

Our results indicated that CSF NfL is a promising prognostic predictor of PD, and its concentration and dynamics can monitor the severity and progression of cognitive decline in de novo PD patients.

Cerebrospinal fluid neurofilament light chain differentiates primary psychiatric disorders from rapidly progressive, Alzheimer's disease and frontotemporal disorders in clinical settings

INTRODUCTION

Many patients with cognitive and neuropsychiatric symptoms face diagnostic delay and misdiagnosis. We investigated whether cerebrospinal fluid (CSF) neurofilament light (NfL) and total-tau (t-tau) could assist in the clinical scenario of differentiating neurodegenerative (ND) from psychiatric disorders (PSY), and rapidly progressive disorders.

METHODS

Biomarkers were examined in patients from specialist services (ND and PSY) and a national Creutzfeldt-Jakob registry (Creutzfeldt-Jakob disease [CJD] and rapidly progressive dementias/atypically rapid variants of common ND, RapidND).

RESULTS

A total of 498 participants were included: 197 ND, 67 PSY, 161 CJD, 48 RapidND, and 20 controls. NfL was elevated in ND compared to PSY and controls, with highest levels in CJD and RapidND. NfL distinguished ND from PSY with 95%/78% positive/negative predictive value, 92%/87% sensitivity/specificity, 91% accuracy. NfL outperformed t-tau in most real-life clinical diagnostic dilemma scenarios, except distinguishing CJD from RapidND.

DISCUSSION

We demonstrated strong generalizable evidence for the diagnostic utility of CSF NfL in differentiating ND from psychiatric disorders, with high accuracy.

Head-to-Head Comparison of Different Blood Collecting Tubes for Quantification of Alzheimer’s Disease Biomarkers in Plasma

To examine whether the type of blood collection tubes affects the quantification of plasma biomarkers for Alzheimer’s disease analyzed with a single-molecule array (Simoa), we recruited a healthy cohort (n = 34, 11 males, mean age = 28.7 ± 7.55) and collected plasma in the following tubes: dipotassium ethylenediaminetetraacetic acid (K2-EDTA), heparin lithium (Li-Hep), and heparin sodium (Na-Hep). Plasma tau, phosphorylated tau 181 (p-tau181), amyloid β (1–40) (Aβ40), and amyloid β (1–42) (Aβ42) were quantified using Simoa. We compared the value of plasma analytes, as well as the effects of sex on the measurements. We found that plasma collected in Li-Hep and Na-Hep tubes yielded significantly higher tau and p-tau181 levels compared to plasma collected in K2-EDTA tubes from the same person, but there was no difference in the measured values of the Aβ40, Aβ42, and Aβ42/40 ratio. Therefore, the type of blood collecting tubes should be considered when planning studies that measure plasma tau.

Neuro-Axonal Damage and Alteration of Blood–Brain Barrier Integrity in COVID-19 Patients

Neurofilament light chain (NfL) is a specific biomarker of neuro-axonal damage. Matrix metalloproteinases (MMPs) are zinc-dependent enzymes involved in blood–brain barrier (BBB) integrity. We explored neuro-axonal damage, alteration of BBB integrity and SARS-CoV-2 RNA presence in COVID-19 patients with severe neurological symptoms (neuro-COVID) as well as neuro-axonal damage in COVID-19 patients without severe neurological symptoms according to disease severity and after recovery, comparing the obtained findings with healthy donors (HD). Overall, COVID-19 patients (n = 55) showed higher plasma NfL levels compared to HD (n = 31) (p < 0.0001), especially those who developed ARDS (n = 28) (p = 0.0005). After recovery, plasma NfL levels were still higher in ARDS patients compared to HD (p = 0.0037). In neuro-COVID patients (n = 12), higher CSF and plasma NfL, and CSF MMP-2 levels in ARDS than non-ARDS group were observed (p = 0.0357, p = 0.0346 and p = 0.0303, respectively). SARS-CoV-2 RNA was detected in four CSF and two plasma samples. SARS-CoV-2 RNA detection was not associated to increased CSF NfL and MMP levels. During COVID-19, ARDS could be associated to CNS damage and alteration of BBB integrity in the absence of SARS-CoV-2 RNA detection in CSF or blood. CNS damage was still detectable after discharge in blood of COVID-19 patients who developed ARDS during hospitalization.

Tau and neurofilament light-chain as fluid biomarkers in spinocerebellar ataxia type 3

BACKGROUND AND PURPOSE

Clinical trials in spinocerebellar ataxia type 3 (SCA3) will require biomarkers for use as outcome measures.

METHODS

To evaluate total tau (t-tau), glial fibrillary acidic protein (GFAP), ubiquitin carboxy-terminal hydrolase L1 (UCHL1) and neurofilament light-chain (NfL) as fluid biomarkers in SCA3, ATXN3 mutation carriers (n = 143) and controls (n = 172) were clinically assessed, and the plasma concentrations of the four proteins were analysed on the Simoa HD-1 platform. Eleven ATXN3 mutation carrier cerebrospinal fluid samples were analysed for t-tau and phosphorylated tau (p-tau¹⁸¹ ). A transgenic SCA3 mouse model (MJDTg) was used to measure cerebellar t-tau levels.

RESULTS

Plasma t-tau levels were higher in mutation carriers below the age of 50 compared to controls, and the Inventory of Non-Ataxia Signs was associated with t-tau in ataxic patients (p = 0.004). Pre-ataxic carriers showed higher cerebrospinal fluid t-tau and p-tau¹⁸¹ concentrations compared to ataxic patients (p = 0.025 and p = 0.014, respectively). Cerebellar t-tau was elevated in MJDTg mice compared to wild-type (p = 0.033) only in the early stages of the disease. GFAP and UCHL1 did not show higher levels in mutation carriers compared to controls. Plasma NfL concentrations were higher in mutation carriers compared to controls, and differences were greater for younger carriers. The Scale for the Assessment and Rating of Ataxia was the strongest predictor of NfL in ataxic patients (p < 0.001).

CONCLUSION

Our results suggest that tau might be a marker of early disease stages in SCA3. NfL can discriminate mutation carriers from controls and is associated with different clinical variables. Longitudinal studies are required to confirm their potential role as biomarkers in clinical trials.

Atypical Case of VV1 Creutzfeldt–Jakob Disease Subtype: Case Report

Creutzfeldt–Jakob disease (CJD) is a rare form of rapidly progressive, neurodegenerative disease that results from the misfolding and accumulation of an aberrant, disease-associated prion protein (PrPD). CJD affects 1–1.5 cases per million per year with the sporadic-type accounting for an estimated 85% of these cases. Sporadic CJD (sCJD) is further subdivided into five subtypes based on genetic polymorphisms; the rarest subtype, sCJDVV1, occurs at a rate of 1 case per one-hundredth million population per year. Clinical characteristics of the sCJDVV1 subtype have been reported to show, early age of onset (44 years), average disease duration of 21 months, absent PSWCs on electroencephalography (EEG), and MRI hyperintensities in the cerebral cortex with usual negative signal in the basal ganglia or thalamus. We present a case of the sCJDVV1 subtype with uncommon features. Contrary to current data on sCJDVV1, our patient presented with an unusual age at onset (61 years) and longer disease duration (32 months). The highly sensitive and specific real-time quaking-induced conversion (RT-QuIC) assay was negative. Presenting clinical symptoms included paranoid thoughts and agitation, rapidly progressive memory decline, prosopagnosia, and late development of myoclonus and mutism. Other findings showed positive antithyroid peroxidase antibodies (anti-TPO), and absent PSWCs on EEG. High-dose steroid therapy treatment was administered based on positive anti-TPO findings, which failed to elicit any improvement and the patient continued to decline. To our knowledge, only four cases with the sCJDVV1 subtype, including our patient, have been reported to have a negative result on RT-QuIC. This may suggest varied sensitivity across sCJD subtypes. However, given the rarity of our patient's subtype, and the relatively novel RT-QuIC, current data are based on a small number of cases and larger cohorts of confirmed VV1 cases with RT-QuIC testing need to be reported.

Plasma Amyloid Beta, Total-Tau and Neurofilament Light Chain Levels and the Risk of Stroke: A Prospective Population-Based Study

BACKGROUND AND OBJECTIVES

To unravel whether Alzheimer's disease-related pathology or neurodegeneration play a role in stroke etiology, we determined the effect of plasma levels amyloid β (Aβ), total-tau and neurofilament light chain (NfL) on risk of stroke and its subtypes.

METHODS

Between 2002 and 2005, we measured plasma Aβ40, Aβ42, total-tau, and NfL in 4,661 stroke-free participants from the population-based Rotterdam Study. We used Cox proportional-hazards models to determine the association between these markers with incident stroke for the entire cohort, per stroke subtype, and by median age, sex, Apolipoprotein E (APOE) ε4 carriership, and education.

RESULTS

After a mean follow-up of 10.8 ± 3.3 years, 379 participants suffered a first-ever stroke. Log2 total-tau at baseline showed a non-linear association with risk of any stroke and ischemic stroke: compared to the first (lowest) quartile the adjusted hazard ratio for the highest quartile total-tau was 1.68, 95% CI: 1.18-2.40 for any stroke. Log2 NfL was associated with an increased risk of any stroke (HR per SD increase 1.27, 95% CI: 1.12-1.44), ischemic stroke, and hemorrhagic stroke (HR 1.56, 95% CI: 1.14-2.12). Log2 Aβ40, Aβ42, and Aβ42/40 ratio levels were not associated with stroke risk.Discussion Participants with higher total-tau and NfL at baseline had a higher risk of stroke and several stroke subtypes. These findings support the role of markers of neurodegeneration in the etiology of stroke.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that higher plasma levels of total-tau and NfL are associated with an increased risk of subsequent stroke.

CSF biomarkers for prion diseases

Recently, clinical trials of human prion disease (HPD) treatments have begun in many countries, and the therapeutic window of these trials focuses mainly on the early stage of the disease. Furthermore, few studies have examined the role of biomarkers at the early stage. According to the World Health Organization, the clinical diagnostic criteria for HPDs include clinical findings, cerebrospinal fluid (CSF) protein markers, and electroencephalography (EEG). In contrast, the UK and European clinical diagnostic criteria include a combination of clinical findings, 14-3-3 protein in the CSF, magnetic resonance imaging-diffusion-weighted imaging (MRI-DWI), and EEG. Moreover, recent advancements in laboratory testing and MRI-DWI have improved the accuracy of diagnostics used for prion diseases. However, according to MRI-DWI data, patients with rapidly progressing dementia are sometimes misdiagnosed with HPD due to the high-intensity areas detected in their brains. Thus, analyzing the CSF biomarkers is critical to diagnose accurately different diseases. CSF biomarkers are investigated using a biochemical approach or the protein amplification methods that utilize the unique properties of prion proteins and the ability of PrP^Sc to induce a conformational change. The biochemical markers include the 14-3-3 and total tau proteins of the CSF. In contrast, the protein amplification methods include the protein misfolding cyclic amplification assay and real-time quaking-induced conversion (RT-QuIC) assay. The RT-QuIC analysis of the CSF has been proved to be a highly sensitive and specific test for identifying sporadic HPD forms; for this reason, it was included in the diagnostic criteria.

Blood β-Synuclein and Neurofilament Light Chain During the Course of Prion Disease

BACKGROUND AND OBJECTIVES

For early diagnosis and disease monitoring of neurodegenerative diseases (NDs) reliable blood biomarkers are needed. Elevated levels of neurofilament light chain protein (NfL), an axonal damage marker, have been described across different NDs with highest values in prion diseases and amyotrophic lateral sclerosis (ALS). Synaptic degeneration is a common early feature in most NDs and seems to precede neuronal degeneration in prion disease. However, synaptic markers in blood are still missing. Here we investigated if the brain specific protein beta-synuclein might be a suitable blood biomarker for early diagnosis and evaluation of synaptic integrity in prion disease.

METHODS

We analyzed blood beta-synuclein with a newly established digital ELISA and NfL with single molecule array in samples obtained from human subjects and prion and ALS animal models. Furthermore, beta-synuclein was investigated in brain tissue of Creutzfeldt-Jakob disease (CJD) and control cases.

RESULTS

We investigated 308 patients including 129 prion disease cases, 8 presymptomatic PRNP mutation carriers, 60 ALS, 68 other ND and 43 control patients. In CJD symptomatic cases beta-synuclein and NfL were markedly increased compared to all other diagnostic groups (p<0.001). In the large majority of pre-symptomatic PRNP mutation carriers beta-synuclein and NfL levels were within normal range. In prion disease animal models, beta-synuclein and NfL displayed normal levels in the pre-symptomatic phase with a sudden elevation at disease onset and a plateau in the symptomatic phase. In contrast to NfL, beta-synuclein was neither elevated in symptomatic ALS patients nor in an ALS animal model. In the discrimination between prion disease and all other groups beta-synuclein (AUC: 0.97, 95% CI: 0.94-0.99, p<0.001) was superior to NfL (AUC: 0.91, 95% CI: 0.88-0.94, p<0.001). Additionally, brain tissue beta-synuclein showed significantly reduced levels in CJD compared to control patients (p<0.001).

DISCUSSION

Blood beta-synuclein was significantly elevated in CJD patients reflecting ongoing synaptic damage and showed good discriminative characteristics. We therefore propose it as a candidate blood marker for early diagnosis and monitoring of synaptic integrity in prion disease.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that serum beta synuclein concentration accurately distinguishes patients with symptomatic CJD from controls.

NT1-Tau Is Increased in CSF and Plasma of CJD Patients, and Correlates with Disease Progression

This study investigates the diagnostic and prognostic potential of different forms of tau in biofluids from patients with Creutzfeldt-Jakob disease (CJD). Extracellular tau, which is molecularly heterogeneous, was measured using ultra-sensitive custom-made Simoa assays for N-terminal (NT1), mid-region, and full-length tau. We assessed cross-sectional CSF and plasma from healthy controls, patients with Alzheimer’s disease (AD) and CJD patients. Then, we evaluated the correlation of the best-performing tau assay (NT1-tau) with clinical severity and functional decline (using the MRC Prion Disease Rating Scale) in a longitudinal CJD cohort (n = 145). In a cross-sectional study, tau measured in CSF with the NT1 and mid-region Simoa assays, separated CJD (n = 15) from AD (n = 18) and controls (n = 21) with a diagnostic accuracy (AUCs: 0.98–1.00) comparable to or better than neurofilament light chain (NfL; AUCs: 0.96–0.99). In plasma, NT1-measured tau was elevated in CJD (n = 5) versus AD (n = 15) and controls (n = 15). Moreover, in CJD plasma (n = 145) NT1-tau levels correlated with stage and rate of disease progression, and the effect on clinical progression was modified by the PRNP codon 129. Our findings suggest that plasma NT1-tau shows promise as a minimally invasive diagnostic and prognostic biomarker of CJD, and should be further investigated for its potential to monitor disease progression and response to therapies.

Sporadic Creutzfeldt-Jakob disease: Real-Time Quaking Induced Conversion (RT-QuIC) assay represents a major diagnostic advance

Sporadic Creutzfeldt-Jakob disease (sCJD) is a rare and fatal neurodegenerative disorder with an incidence of 1.5 to 2 cases per million population/year. The disease is caused by a proteinaceous infectious agent, named prion (or PrPSc), which arises from the conformational conversion of the cellular prion protein (PrPC). Once formed, PrPSc interacts with the normally folded PrPC coercing it to undergo similar structural rearrangement. The disease is highly heterogeneous from a clinical and neuropathological point of view. The origin of this variability lies in the aberrant structures acquired by PrPSc. At least six different sCJD phenotypes have been described and each of them is thought to be caused by a peculiar PrPSc strain. Definitive sCJD diagnosis requires brain analysis with the aim of identifying intracerebral accumulation of PrPSc which currently represents the only reliable biomarker of the disease. Clinical diagnosis of sCJD is very challenging and is based on the combination of several clinical, instrumental and laboratory tests representing surrogate disease biomarkers. Thanks to the advent of the ultrasensitive Real-Time Quaking-Induced Conversion (RT-QuIC) assay, PrPSc was found in several peripheral tissues of sCJD patients, sometimes even before the clinical onset of the disease. This discovery represents an important step forward for the clinical diagnosis of sCJD. In this manuscript, we present an overview of the current applications and future perspectives of RT-QuIC in the field of sCJD diagnosis.

Evaluation of plasma tau and neurofilament light chain biomarkers in a 12-year clinical cohort of human prion diseases

Prion diseases are fatal neurodegenerative conditions with highly accurate CSF and imaging diagnostic tests, but major unmet needs for blood biomarkers. Using ultrasensitive immuno-assays, we measured tau and neurofilament light chain (NfL) protein concentrations in 709 plasma samples taken from 377 individuals with prion disease during a 12 year prospective clinical study, alongside healthy and neurological control groups. This provides an unprecedented opportunity to evaluate their potential as biomarkers. Plasma tau and NfL were increased across all prion disease types. For distinguishing sCJD from control groups including clinically-relevant "CJD mimics", both show considerable diagnostic value. In sCJD, NfL was substantially elevated in every sample tested, including during early disease with minimal functional impairment and in all follow-up samples. Plasma tau was independently associated with rate of clinical progression in sCJD, while plasma NfL showed independent association with severity of functional impairment. In asymptomatic PRNP mutation carriers, plasma NfL was higher on average in samples taken within 2 years of symptom onset than in samples taken earlier. We present biomarker trajectories for nine mutation carriers healthy at enrolment who developed symptoms during follow-up. NfL started to rise as early as 2 years before onset in those with mutations typically associated with more slowly progressive clinical disease. This shows potential for plasma NfL as a "proximity marker", but further work is needed to establish predictive value on an individual basis, and how this varies across different PRNP mutations. We conclude that plasma tau and NfL have potential to fill key unmet needs for biomarkers in prion disease: as a secondary outcome for clinical trials (NfL and tau); for predicting onset in at-risk individuals (NfL); and as an accessible test for earlier identification of patients that may have CJD and require more definitive tests (NfL). Further studies should evaluate their performance directly in these specific roles.

Developing the ATX(N) classification for use across the Alzheimer disease continuum

Breakthroughs in the development of highly accurate fluid and neuroimaging biomarkers have catalysed the conceptual transformation of Alzheimer disease (AD) from the traditional clinical symptom-based definition to a clinical-biological construct along a temporal continuum. The AT(N) system is a symptom-agnostic classification scheme that categorizes individuals using biomarkers that chart core AD pathophysiological features, namely the amyloid-β (Aβ) pathway (A), tau-mediated pathophysiology (T) and neurodegeneration (N). This biomarker matrix is now expanding towards an ATX(N) system, where X represents novel candidate biomarkers for additional pathophysiological mechanisms such as neuroimmune dysregulation, synaptic dysfunction and blood-brain barrier alterations. In this Perspective, we describe the conceptual framework and clinical importance of the existing AT(N) system and the evolving ATX(N) system. We provide a state-of-the-art summary of the potential contexts of use of these systems in AD clinical trials and future clinical practice. We also discuss current challenges related to the validation, standardization and qualification process and provide an outlook on the real-world application of the AT(N) system.

Serum Neurofilament Dynamics Predicts Cognitive Progression in de novo Parkinson's Disease

BACKGROUND

Neurofilament light (NfL) can reflect the extent of neuron/axon damage, thus providing an opportunity to examine the severity and progression of the diseases with such damage.

OBJECTIVE

Whether serum NfL can be used as an indicator to monitor the cognitive progress of de novo Parkinson's disease (PD) remains unclear.

METHODS

In this research, 144 healthy controls and 301 de novo PD patients from Parkinson's Progression Markers Initiative (PPMI) were recruited. Linear mixed effects models were used to examine the associations of baseline/longitudinal serum NfL with cognitive decline. Cox regression was used to detect cognitive progression in PD participants.

RESULTS

We found PD patients had higher serum NfL than controls at baseline (p = 0.031), and NfL increase was faster in PD group (p < 0.001). Both baseline serum NfL and its rate of change predicted measurable cognitive decline in early PD (MoCA, β= -0.014, p < 0.001; β= -0.002, p < 0.001, respectively). Additionally, we observed that NfL levels were also able to predict progression in different diagnostic groups and Amyloid- PD and Amyloid+PD groups. After an average follow-up of 6.37±1.84 years, the baseline NfL of the third tertile of high concentrations was associated with a future high risk of PD dementia (adjusted HR 6.33, 95% CI 2.62-15.29, p < 0.001).

CONCLUSION

In conclusion, our results indicated that the serum NfL concentration could function as an easily accessible biomarker to monitor the severity and progression of cognitive decline in PD.

Diagnostic and prognostic performance of CSF α-synuclein in prion disease in the context of rapidly progressive dementia

INTRODUCTION

Surrogate cerebrospinal fluid (CSF) biomarkers of neurodegeneration still have a central role in the first-line screening of patients with suspected Creutzfeldt-Jakob disease (CJD). Recently, CSF α-synuclein, a marker of synaptic damage, showed a close to optimal performance in distinguishing between CJD and other neurodegenerative dementias.

METHODS

We evaluated the diagnostic value of CSF α-synuclein in patients with prion disease, non-prion rapidly progressive dementias, and non-neurodegenerative controls. Additionally, we studied its distribution across the different prion disease subtypes and evaluated its association with survival.

RESULTS

CSF α-synuclein levels were significantly higher in patients with prion disease than in the other groups but showed a lower diagnostic value than CSF total tau or 14-3-3. Moreover, CSF α-synuclein was significantly associated with survival in the whole prion cohort and the most frequent clinicopathological subtypes.

DISCUSSION

In the clinical setting, CSF α-synuclein does not exceed the diagnostic performance of currently used surrogate markers, but it might constitute a robust prognostic indicator.

TREM2 expression in the brain and biological fluids in prion diseases

Triggering receptor expressed on myeloid cells 2 (TREM2) is an innate immune cell surface receptor that regulates microglial function and is involved in the pathophysiology of several neurodegenerative diseases. Its soluble form (sTREM2) results from shedding of the TREM2 ectodomain. The role of TREM2 in prion diseases, a group of rapidly progressive dementias remains to be elucidated. In the present study, we analysed the expression of TREM2 and its main sheddase ADAM10 in the brain of sporadic Creutzfeldt-Jakob disease (sCJD) patients and evaluated the role of CSF and plasma sTREM2 as a potential diagnostic marker of prion disease. Our data indicate that, compared to controls, TREM2 is increased in sCJD patient brains at the mRNA and protein levels in a regional and subtype dependent fashion, and expressed in a subpopulation of microglia. In contrast, ADAM10 is increased at the protein, but not the mRNA level, with a restricted neuronal expression. Elevated CSF sTREM2 is found in sCJD, genetic CJD with mutations E200K and V210I in the prion protein gene (PRNP), and iatrogenic CJD, as compared to healthy controls (HC) (AUC = 0.78–0.90) and neurological controls (AUC = 0.73–0.85), while CSF sTREM2 is unchanged in fatal familial insomnia. sTREM2 in the CSF of cases with Alzheimer’s disease, and multiple sclerosis was not significantly altered in our series. CSF sTREM2 concentrations in sCJD are PRNP codon 129 and subtype-related, correlate with CSF 14-3-3 positivity, total-tau and YKL-40, and increase with disease progression. In plasma, sTREM2 is increased in sCJD compared with HC (AUC = 0.80), displaying positive correlations with plasma total-tau, neurofilament light, and YKL-40. We conclude that comparative study of TREM2 in brain and biological fluids of prion diseases reveals TREM2 to be altered in human prion diseases with a potential value in target engagement, patient stratification, and disease monitoring.

A neurologist's perspective on serum neurofilament light in the memory clinic: a prospective implementation study

Background

Neurofilament light in serum (sNfL) is a biomarker for axonal damage with elevated levels in many neurological disorders, including neurodegenerative dementias. Since within-group variation of sNfL is large and concentrations increase with aging, sNfL’s clinical use in memory clinic practice remains to be established. The objective of the current study was to evaluate the clinical use of serum neurofilament light (sNfL), a cross-disease biomarker for axonal damage, in a tertiary memory clinic cohort.

Methods

Six neurologists completed questionnaires regarding the usefulness of sNfL (n = 5–42 questionnaires/neurologist). Patients that visited the Alzheimer Center Amsterdam for the first time between May and October 2019 (n = 109) were prospectively included in this single-center implementation study. SNfL levels were analyzed on Simoa and reported together with normal values in relation to age, as part of routine diagnostic work-up and in addition to cerebrospinal fluid (CSF) biomarker analysis.

Results

SNfL was perceived as useful in 53% (n = 58) of the cases. SNfL was more often perceived as useful in patients < 62 years (29/48, 60%, p = 0.05) and males (41/65, 63%, p < 0.01). Availability of CSF biomarker results at time of result discussion had no influence. We observed non-significant trends for increased perceived usefulness of sNfL for patients with the diagnosis subjective cognitive decline (64%), psychiatric disorder (71%), or uncertain diagnosis (67%). SNfL was mostly helpful to neurologists in confirming or excluding neurodegeneration. Whether sNfL was regarded as useful strongly depended on which neurologist filled out the questionnaire (ranging from 0 to 73% of useful cases/neurologist).

Discussion

Regardless of the availability of CSF biomarker results, sNfL was perceived as a useful tool in more than half of the evaluated cases in a tertiary memory clinic practice. Based on our results, we recommend the analysis of the biomarker sNfL to confirm or exclude neurodegeneration in patients below 62 years old and in males.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00841-4.

Clinical Use of Improved Diagnostic Testing for Detection of Prion Disease

Prion diseases are difficult to recognize as many symptoms are shared among other neurologic pathologies and the full spectra of symptoms usually do not appear until late in the disease course. Additionally, many commonly used laboratory markers are non-specific to prion disease. The recent introduction of second-generation real time quaking induced conversion (RT-QuIC) has revolutionized pre-mortem diagnosis of prion disease due to its extremely high sensitivity and specificity. However, RT-QuIC does not provide prognostic data and has decreased diagnostic accuracy in some rarer, atypical prion diseases. The objective of this review is to provide an overview of the current clinical utility of fluid-based biomarkers, neurodiagnostic testing, and brain imaging in the diagnosis of prion disease and to suggest guidelines for their clinical use, with a focus on rarer prion diseases with atypical features. Recent advancements in laboratory-based testing and imaging criteria have shown improved diagnostic accuracy and prognostic potential in prion disease, but because these diagnostic tests are not sensitive in some prion disease subtypes and diagnostic test sensitivities are unknown in the event that CWD transmits to humans, it is important to continue investigations into the clinical utility of various testing modalities.

Diagnostic and prognostic value of plasma neurofilament light and total-tau in sporadic Creutzfeldt-Jakob disease

BACKGROUND

Blood neurofilament light (Nfl) and total-tau (t-tau) have been described to be increased in several neurological conditions, including prion diseases and other neurodegenerative dementias. Here, we aim to determine the accuracy of plasma Nfl and t-tau in the differential diagnosis of neurodegenerative dementias and their potential value as prognostic markers of disease severity.

METHODS

Plasma Nfl and t-tau were measured in healthy controls (HC, n = 70), non-neurodegenerative neurological disease with (NND-Dem, n = 17) and without dementia syndrome (NND, n = 26), Alzheimer's disease (AD, n = 44), Creutzfeldt-Jakob disease (CJD, n = 83), dementia with Lewy bodies/Parkinson's disease with dementia (DLB/PDD, n = 35), frontotemporal dementia (FTD, n = 12), and vascular dementia (VaD, n = 22). Biomarker diagnostic accuracies and cutoff points for the diagnosis of CJD were calculated, and associations between Nfl and t-tau concentrations with other fluid biomarkers, demographic, genetic, and clinical data in CJD cases were assessed. Additionally, the value of Nfl and t-tau predicting disease survival in CJD was evaluated.

RESULTS

Among diagnostic groups, highest plasma Nfl and t-tau concentrations were detected in CJD (fold changes of 38 and 18, respectively, compared to HC). Elevated t-tau was able to differentiate CJD from all other groups, whereas elevated Nfl concentrations were also detected in NND-Dem, AD, DLB/PDD, FTD, and VaD compared to HC. Both biomarkers discriminated CJD from non-CJD dementias with an AUC of 0.93. In CJD, plasma t-tau, but not Nfl, was associated with PRNP codon 129 genotype and CJD subtype. Positive correlations were observed between plasma Nfl and t-tau concentrations, as well as between plasma and CSF concentrations of both biomarkers (p < 0.001). Nfl was increased in rapidly progressive AD (rpAD) compared to slow progressive AD (spAD) and associated to Mini-Mental State Examination results. However, Nfl displayed higher accuracy than t-tau discriminating CJD from rpAD and spAD. Finally, plasma t-tau, but not plasma Nfl, was significantly associated with disease duration, offering a moderate survival prediction capacity.

CONCLUSIONS

Plasma Nfl and t-tau are useful complementary biomarkers for the differential diagnosis of CJD. Additionally, plasma t-tau emerges as a potential prognostic marker of disease duration.

Prediction of Outcome After Endovascular Embolectomy in Anterior Circulation Stroke Using Biomarkers

Stroke is a major public health problem that can cause a long-term disability or death due to brain damage. Serious stroke is frequently caused by a large vessel occlusion in the anterior circulation, which should be treated by endovascular embolectomy if possible. In this study, we investigated the use of the brain damage biomarkers tau, NFL, NSE, GFAp, and S100B to understand the progression of nervous tissue damage and their relationship to outcome in such stroke after endovascular treatment. Blood samples were taken from 90 patients pre-treatment and 2 h, 24 h, 48 h, 72 h and 3 months after endovascular treatment. Stroke-related neurological deficit was estimated using the National Institute of Health Stroke Scale (NIHSS) at admission and at 24 h. Neurological outcome was evaluated at 3 months. After stroke, tau, NFL, GFAp and S100B increased in a time dependent manner, while NSE remained constant over time. At 3 months, tau and GFAp levels were back to normal whereas NFL was still high. Tau, NFL and GFAp correlated well to outcome, as well as to infarct volume and NIHSS at 24 h. The best time for prediction of poor outcome was different for each biomarker. However, the combination of NIHSS at 24 h with either tau, NFL or GFAp at 48 h gave the best prediction. The use of biomarkers in the early setting after endovascular treatment of stroke will lead to a simplified and standardized way to estimate the nervous tissue damage and possibly complement the clinical judgement in foreseeing the need of rehabilitation measures.

Ultrasensitive assays for detection of plasma tau and phosphorylated tau 181 in Alzheimer's disease: a systematic review and meta-analysis

A lack of convenient and reliable biomarkers for diagnosis and prognosis is a common challenge for neurodegenerative diseases such as Alzheimer's disease (AD). Recent advancement in ultrasensitive protein assays has allowed the quantification of tau and phosphorylated tau proteins in peripheral plasma. Here we identified 66 eligible studies reporting quantification of plasma tau and phosphorylated tau 181 (ptau181) using four ultrasensitive methods. Meta-analysis of these studies confirmed that the AD patients had significantly higher plasma tau and ptau181 levels compared with controls, and that the plasma tau and ptau181 could predict AD with high-accuracy area under curve of the Receiver Operating Characteristic. Therefore, plasma tau and plasma ptau181 can be considered as biomarkers for AD diagnosis.

Cerebrospinal Fluid and Blood Neurofilament Light Chain Protein in Prion Disease and Other Rapidly Progressive Dementias: Current State of the Art

Rapidly progressive dementia (RPD) is an umbrella term referring to several conditions causing a rapid neurological deterioration associated with cognitive decline and short disease duration. They comprise Creutzfeldt–Jakob disease (CJD), the archetypal RPD, rapidly progressive variants of the most common neurodegenerative dementias (NDs), and potentially treatable conditions such as infectious or autoimmune encephalitis and cerebrovascular disease. Given the significant clinical and, sometimes, neuroradiological overlap between these different disorders, biofluid markers also contribute significantly to the differential diagnosis. Among them, the neurofilament light chain protein (NfL) has attracted growing attention in recent years as a biofluid marker of neurodegeneration due to its sensitivity to axonal damage and the reliability of its measurement in both cerebrospinal fluid (CSF) and blood. Here, we summarize current knowledge regarding biological and clinical implications of NfL evaluation in biofluids across RPDs, emphasizing CJD, and other prion diseases. In the latter, NfL demonstrated a good diagnostic and prognostic accuracy and a potential value as a marker of proximity to clinical onset in pre-symptomatic PRNP mutation carriers. Similarly, in Alzheimer’s disease and other NDs, higher NfL concentrations seem to predict a faster disease progression. While increasing evidence indicates a potential clinical value of NfL in monitoring cerebrovascular disease, the association between NfL and prediction of outcome and/or disease activity in autoimmune encephalitis and infectious diseases has only been investigated in few cohorts and deserves confirmatory studies. In the era of precision medicine and evolving therapeutic options, CSF and blood NfL might aid the diagnostic and prognostic assessment of RPDs and the stratification and management of patients according to disease progression in clinical trials.

Biomarkers and diagnostic guidelines for sporadic Creutzfeldt-Jakob disease

Sporadic Creutzfeldt-Jakob disease is a fatal neurodegenerative disease caused by misfolded prion proteins (PrP^Sc). Effective therapeutics are currently not available and accurate diagnosis can be challenging. Clinical diagnostic criteria use a combination of characteristic neuropsychiatric symptoms, CSF proteins 14-3-3, MRI, and EEG. Supportive biomarkers, such as high CSF total tau, could aid the diagnostic process. However, discordant studies have led to controversies about the clinical value of some established surrogate biomarkers. Development and clinical application of disease-specific protein aggregation and amplification assays, such as real-time quaking induced conversion (RT-QuIC), have constituted major breakthroughs for the confident pre-mortem diagnosis of sporadic Creutzfeldt-Jakob disease. Updated criteria for the diagnosis of sporadic Creutzfeldt-Jakob disease, including application of RT-QuIC, should improve early clinical confirmation, surveillance, assessment of PrP^Sc seeding activity in different tissues, and trial monitoring. Moreover, emerging blood-based, prognostic, and potentially pre-symptomatic biomarker candidates are under investigation.

Neuropathological and Biomarker Findings in Parkinson's Disease and Alzheimer's Disease: From Protein Aggregates to Synaptic Dysfunction

There is mounting evidence that Parkinson’s disease (PD) and Alzheimer’s disease (AD) share neuropathological hallmarks, while similar types of biomarkers are being applied to both. In this review we aimed to explore similarities and differences between PD and AD at both the neuropathology and the biomarker levels, specifically focusing on protein aggregates and synapse dysfunction. Thus, amyloid-β peptide (Aβ) and tau lesions of the Alzheimer-type are common in PD and α-synuclein Lewy-type aggregates are frequent findings in AD. Modern neuropathological techniques adding to routine immunohistochemistry might take further our knowledge of these diseases beyond protein aggregates and down to their presynaptic and postsynaptic terminals, with potential mechanistic and even future therapeutic implications. Translation of neuropathological discoveries to the clinic remains challenging. Cerebrospinal fluid (CSF) and positron emission tomography (PET) markers of Aβ and tau have been shown to be reliable for AD diagnosis. Conversely, CSF markers of α-synuclein have not been that consistent. In terms of PET markers, there is no PET probe available for α-synuclein yet, while the AD PET markers range from consistent evidence of their specificity (amyloid imaging) to greater uncertainty of their reliability due to off-target binding (tau imaging). CSF synaptic markers are attractive, still needing more evidence, which currently suggests those might be non-specific markers of disease progression. It can be summarized that there is neuropathological evidence that protein aggregates of AD and PD are present both at the soma and the synapse. Thus, a number of CSF and PET biomarkers beyond α-synuclein, tau and Aβ might capture these different faces of protein-related neurodegeneration. It remains to be seen what the longitudinal outcomes and the potential value as surrogate markers of these biomarkers are.

Association of Plasma Neurofilament Light With Small Vessel Disease Burden in Nondemented Elderly: A Longitudinal Study

BACKGROUND AND PURPOSE

Neurofilament light chain (NfL) is a promising predictive biomarker of active axonal injury and neuronal degeneration diseases. We aimed to evaluate if an increase in plasma NfL levels could play a monitoring role in the progression of cerebral small vessel disease (CSVD) among the nondemented elders, which are highly prevalent in elderly individuals and associated with an increased risk of stroke and dementia.

METHODS

The study included 496 nondemented participants from the Alzheimer disease neuroimaging initiative database. All participants underwent plasma NfL measurements and 3.0-Tesla magnetic resonance imaging of the brain; 387 (78.0%) underwent longitudinal measurements. The number of cerebral microbleeds, lacunar infarcts, and volumetric white matter hyperintensities, as well as Fazekas scores, were measured. Cross-sectional and longitudinal associations between CSVD burden and NfL levels were evaluated using multivariable-adjusted models.

RESULTS

Plasma NfL was higher in the moderate-severe CSVD burden group (45.2±16.0 pg/mL) than in the nonburden group (34.3±15.1 pg/mL; odds ratio [OR]=1.71 [95% CI, 1.24-2.35]) at baseline. NfL was positively associated with the presence of cerebral microbleeds (OR=1.29 [95% CI, 1.01-1.64]), lacunar infarcts (OR=1.43 [95% CI, 1.06-1.93]), and moderate-severe white matter hyperintensities (OR=1.67 [95% CI, 1.24-2.25]). Longitudinally, a higher change rate of NfL could predict more progression of CSVD burden (OR=1.38 [95% CI, 1.08-1.76]), white matter hyperintensities (OR=1.41 [95% CI, 1.10-1.79]), and lacunar infarcts (OR=1.99 [95% CI, 1.42-2.77]).

CONCLUSIONS

Plasma NfL level is a valuable noninvasive biomarker that supplements magnetic resonance imaging scans and possibly reflects the severity of CSVD burden. Furthermore, high plasma NfL levels tend to represent an increased CSVD risk, and dynamic increases in NfL levels might predict a greater progression of CSVD.

Serum levels of total human Tau associated with axonal damage among severe malaria patients in Central India

Tau is a microtubule-associated protein (MAP) that is abundant in the axonal part of neurons of the central nervous system. Previous studies among African children and Vietnamese adults suffering from cerebral malaria (CM) showed the pathological significance of measuring circulatory total Tau levels. A pilot investigation was carried out to better characterise neurological pathogenesis among severe malaria patients in Central India. Serum levels of total human Tau (pg/ml) were measured by ELISA following manufacturer guidelines among hospital admitted P. falciparum malaria patients classified with different degree of severity (mild malaria = MM, non-cerebral severe malaria = NCSM, cerebral malaria survivors = CM-S and cerebral malaria non-survivors = CM-NS) using WHO, 2000 definitions, including healthy controls (HC) enroled from the hospital's blood bank. Categorical and numerical variables were analysed by applying appropriate statistical test using Stata 11.0 software. A total of 139 subjects (14 HC, 25 MM, 29 NCSM, 44 CM-S and 27 CM-NS) were included in this preliminary investigation. Serum levels of total human Tau were detected in 0% HC, 4.0% MM, 20.7% NCSM, 43.2% CM-S and 48.2% CM-NS patients. Compared to MM, percent Tau detection was significantly higher among severe malaria patients (p = 0.001). Further, compared to NCSM,% Tau detection was significantly higher in CM-S patients (Chi² = 3.9, p = 0.048) & CM-NS patients (Chi² = 4.7, p = 0.030). Percent Tau detection was also significantly higher among severe malaria cases presenting with multiple complications compared to those without multiple complications (p = 0.006). ROC analysis of serum Tau levels (pg/ml) revealed a fair AUC value (0.75) to distinguish CM-NS group (but not CM-S) from NCSM group. In conclusion, serum percent detection of total human Tau is associated with axonal damage among patients with different degree of P. falciparum malaria severity in Central India.

Immunity and amyloid beta, total tau and neurofilament light chain: Findings from a community-based cohort study

Introduction

We investigated how components of immunity relate to biomarkers of Alzheimer's disease (AD) in plasma and explored the influence of AD genetic risk factors in the population‐based Rotterdam Study.

Methods

In 7397 persons, we calculated the granulocyte‐to‐lymphocyte ratio (GLR), platelet‐to‐lymphocyte ratio (PLR), and systemic immune‐inflammation index (SII). In 3615 of these persons, plasma amyloid‐beta (Aβ)42 and Aβ40 were measured. Next, we constructed an overall genetic risk score (GRS) based on genome‐wide significant variants, both including and excluding APOE ε4.

Results

All innate immunity phenotypes were related to higher Aβ, most strongly with a doubling in GLR leading to a 1.9% higher Aβ42 (95% confidence interval [95% CI] 0.4 to 3.3%) and 3.2% higher Aβ40 (95% CI 2.0 to 4.3%). Higher AD GRS including APOE ε4 was associated with higher immunity markers.

Discussion

Higher levels of immunity markers were associated with higher Aβ in plasma. Participants with a higher genetic predisposition to AD had higher immunity markers, where these effects were mainly driven by APOE ε4.

Comparison between plasma and cerebrospinal fluid biomarkers for the early diagnosis and association with survival in prion disease

OBJECTIVE

To compare the diagnostic accuracy and the prognostic value of blood and cerebrospinal fluid (CSF) tests across prion disease subtypes.

METHODS

We used a single-molecule immunoassay to measure tau and neurofilament light chain (NfL) protein levels in the plasma and assessed CSF total(t)-tau, NfL and protein 14-3-3 levels in patients with prion disease (n=336), non-prion rapidly progressive dementias (n=106) and non-neurodegenerative controls (n=37). We then evaluated each plasma and CSF marker for diagnosis and their association with survival, taking into account the disease subtype, which is a strong independent prognostic factor in prion disease.

RESULTS

Plasma tau and NfL concentrations were higher in patients with prion disease than in non-neurodegenerative controls and non-prion rapidly progressive dementias. Plasma tau showed higher diagnostic value than plasma NfL, but a lower accuracy than the CSF proteins t-tau and 14-3-3. In the whole prion cohort, both plasma (tau and NfL) and CSF (t-tau, 14-3-3 and NfL) markers were significantly associated with survival and showed similar prognostic values. However, the intrasubtype analysis revealed that only CSF t-tau in sporadic Creutzfeldt-Jakob disease (sCJD) MM(V)1, plasma tau and CSF t-tau in sCJD VV2, and plasma NfL in slowly progressive prion diseases were significantly associated with survival after accounting for covariates.

CONCLUSIONS

Plasma markers have lower diagnostic accuracy than CSF biomarkers. Plasma tau and NfL and CSF t-tau are significantly associated with survival in prion disease in a subtype-specific manner and can be used to improve clinical trial stratification and clinical care.

Different Clinical Contexts of Use of Blood Neurofilament Light Chain Protein in the Spectrum of Neurodegenerative Diseases

One of the most pressing challenges in the clinical research of neurodegenerative diseases (NDDs) is the validation and standardization of pathophysiological biomarkers for different contexts of use (CoUs), such as early detection, diagnosis, prognosis, and prediction of treatment response. Neurofilament light chain (NFL) concentration is a particularly promising candidate, an indicator of axonal degeneration, which can be analyzed in peripheral blood with advanced ultrasensitive methods. Serum/plasma NFL concentration is closely correlated with cerebrospinal fluid NFL and directly reflects neurodegeneration within the central nervous system. Here, we provide an update on the feasible CoU of blood NFL in NDDs and translate recent findings to potentially valuable clinical practice applications. As NFL is not a disease-specific biomarker, however, blood NFL is an easily accessible biomarker with promising different clinical applications for several NDDs: (1) early detection and diagnosis (i.e., amyotrophic lateral sclerosis, Creutzfeldt-Jakob disease, atypical parkinsonisms, sporadic late-onset ataxias), (2) prognosis (Huntington's disease and Parkinson's disease), and (3) prediction of time to symptom onset (presymptomatic mutation carriers in genetic Alzheimer's disease and spinocerebellar ataxia type 3).

High efavirenz levels but not neurofilament light plasma levels are associated with poor neurocognitive functioning in asymptomatic HIV patients

The aim of this study is to assess the effect of efavirenz exposure on neurocognitive functioning and investigate plasma neurofilament light (Nfl) as a biomarker for neurocognitive damage. Sub-analysis of the ESCAPE-study, a randomised controlled trial where virologically suppressed, cognitively asymptomatic HIV patients were randomised (2:1) to switch to rilpivirine or continue on efavirenz. At baseline and week 12, patients underwent an extensive neuropsychological assessment (NPA), and serum efavirenz concentration and plasma Nfl levels were measured. Subgroups of elevated (≥ 4.0 mg/L) and therapeutic (0.74 to< 4.0 mg/L) baseline efavirenz concentration were made. Differences between these groups in baseline NPA Z-scores and in delta scores after efavirenz discontinuation were assessed. Nfl level was measured using an ELISA analysis using single molecule array (Simoa) technology. Correlation of plasma NFL with NPA Z-scores was evaluated using a linear mixed model. The elevated group consisted of 6 patients and the therapeutic group of 48. At baseline, the elevated group showed lower composite Z-scores (median - 1.03; IQR 0.87 versus 0.27; 0.79. p 0.02). This effect was also seen on the subdomains verbal (p 0.01), executive functioning (p 0.02), attention (p < 0.01) and speed (p 0.01). In the switch group, the elevated group improved more on composite scores after discontinuing efavirenz (mean 0.58; SD 0.32 versus 0.22; 0.54, p 0.15). No association between plasma Nfl and composite Z-score was found. High efavirenz exposure is associated with worse cognitive functioning compared with patients with therapeutic concentrations. Plasma Nfl is not a suitable biomarker to measure cognitive damage in this group.

Association Between Longitudinal Plasma Neurofilament Light and Neurodegeneration in Patients With Alzheimer Disease

Importance

Plasma neurofilament light (NfL) has been suggested as a noninvasive biomarker to monitor neurodegeneration in Alzheimer disease (AD), but studies are lacking.

Objective

To examine whether longitudinal plasma NfL levels are associated with other hallmarks of AD.

Design, Setting, and Participants

This North American cohort study used data from 1583 individuals in the multicenter Alzheimer's Disease Neuroimaging Initiative study from September 7, 2005, through June 16, 2016. Patients were eligible for inclusion if they had NfL measurements. Annual plasma NfL samples were collected for up to 11 years and were analyzed in 2018.

Exposures

Clinical diagnosis, Aβ and tau cerebrospinal fluid (CSF) biomarkers, imaging measures (magnetic resonance imaging and fluorodeoxyglucose-positron emission tomography), and tests on cognitive scores.

Main Outcomes and Measures

The primary outcome was the association between baseline exposures (diagnosis, CSF biomarkers, imaging measures, and cognition) and longitudinal plasma NfL levels, analyzed by an ultrasensitive assay. The secondary outcomes were the associations between a multimodal classification scheme with Aβ, tau, and neurodegeneration (ie, the ATN system) and plasma NfL levels and between longitudinal changes in plasma NfL levels and changes in the other measures.

Results

Of the included 1583 participants, 716 (45.2%) were women, and the mean (SD) age was 72.9 (7.1) years; 401 had no cognitive impairment, 855 had mild cognitive impairment, and 327 had AD dementia. The NfL level was increased at baseline in patients with mild cognitive impairment and AD dementia (mean levels: cognitive unimpairment, 32.1 ng/L; mild cognitive impairment, 37.9 ng/L; and AD dementia, 45.9 ng/L; P < .001) and increased in all diagnostic groups, with the greatest increase in patients with AD dementia. A longitudinal increase in NfL level correlated with baseline CSF biomarkers (low Aβ42 [P = .001], high total tau [P = .02], and high phosphorylated tau levels [P = .02]), magnetic resonance imaging measures (small hippocampal volumes [P < .001], thin regional cortices [P = .009], and large ventricular volumes [P = .002]), low fluorodeoxyglucose-positron emission tomography uptake (P = .01), and poor cognitive performance (P < .001) for a global cognitive score. With use of the ATN system, increased baseline NfL levels were seen in A-T+N+ (P < .001), A+T-N+ (P < .001), and A+T+N+ (P < .001), and increased rates of NfL levels were seen in A-T+N- (P = .009), A-T+N+ (P = .02), A+T-N+ (P = .04), and A+T+N+ (P = .002). Faster increase in NfL levels correlated with faster increase in CSF biomarkers of neuronal injury, faster rates of atrophy and hypometabolism, and faster worsening in global cognition (all P < .05 in patients with mild cognitive impairment; associations differed slightly in cognitively unimpaired controls and patients with AD dementia).

Conclusions and Relevance

The findings suggest that plasma NfL can be used as a noninvasive biomarker associated with neurodegeneration in patients with AD and may be useful to monitor effects in trials of disease-modifying drugs.

Cerebrospinal fluid and plasma biomarkers in individuals at risk for genetic prion disease

BACKGROUND

Prion disease is neurodegenerative disease that is typically fatal within months of first symptoms. Clinical trials in this rapidly declining symptomatic patient population have proven challenging. Individuals at high lifetime risk for genetic prion disease can be identified decades before symptom onset and provide an opportunity for early therapeutic intervention. However, randomizing pre-symptomatic carriers to a clinical endpoint is not numerically feasible. We therefore launched a cohort study in pre-symptomatic genetic prion disease mutation carriers and controls with the goal of evaluating biomarker endpoints that may enable informative trials in this population.

METHODS

We collected cerebrospinal fluid (CSF) and blood from pre-symptomatic individuals with prion protein gene (PRNP) mutations (N = 27) and matched controls (N = 16), in a cohort study at Massachusetts General Hospital. We quantified total prion protein (PrP) and real-time quaking-induced conversion (RT-QuIC) prion seeding activity in CSF and neuronal damage markers total tau (T-tau) and neurofilament light chain (NfL) in CSF and plasma. We compared these markers cross-sectionally, evaluated short-term test-retest reliability over 2-4 months, and conducted a pilot longitudinal study over 10-20 months.

RESULTS

CSF PrP levels were stable on test-retest with a mean coefficient of variation of 7% for both over 2-4 months in N = 29 participants and over 10-20 months in N = 10 participants. RT-QuIC was negative in 22/23 mutation carriers. The sole individual with positive RT-QuIC seeding activity at two study visits had steady CSF PrP levels and slightly increased tau and NfL concentrations compared with the others, though still within the normal range, and remained asymptomatic 1 year later. T-tau and NfL showed no significant differences between mutation carriers and controls in either CSF or plasma.

CONCLUSIONS

CSF PrP will be interpretable as a pharmacodynamic readout for PrP-lowering therapeutics in pre-symptomatic individuals and may serve as an informative surrogate biomarker in this population. In contrast, markers of prion seeding activity and neuronal damage do not reliably cross-sectionally distinguish mutation carriers from controls. Thus, as PrP-lowering therapeutics for prion disease advance, "secondary prevention" based on prodromal pathology may prove challenging; instead, "primary prevention" trials appear to offer a tractable paradigm for trials in pre-symptomatic individuals.

Increased Noradrenaline as an Additional Cerebrospinal Fluid Biomarker in PSP-Like Parkinsonism

Academic centers utilize sequential clinical and neuroimaging assessments, including morphometric ratios, to obtain an unequivocal diagnosis of the non-synucleinopathic forms of Parkinsonism, such as progressive supranuclear palsy (PSP), however, a 1-2 year follow-up is required. The on-going long-lasting trials using anti-tau antibodies for PSP patients might therefore be biased by the incorrect enrollment of Parkinson's disease (PD) patients manifesting early axial signs. This perspective study aimed at achieving two major goals: first, to summarize the established biomarker candidates found in cerebrospinal fluid (CSF) in probable PSP patients, including low p-tau and altered neurofilaments. Second, we share our recent data, from CSF samples of well-selected PSP subjects, attributable to both main variants (and revisited in light of MDS criteria), who were followed for 1 year before and 2 years after lumbar puncture. We found a significantly high level of noradrenaline (NE) in these patients, similar to controls, when compared to PD patients. In contrast, CSF samples, in PD, showed a significant reduction in CSF NE and its major metabolite, which confirmed that PD is a multi-system disease involving several endogenous pathways. The NE axis impairments were prominent in PSP featuring worse NPI. It might represent a counterpart to the early and peculiar psycho-pathological profiles that are observed in tauopathies. In conclusion, we highlight that CSF biomarkers, which are easy to collect, can provide rapid insights as diagnostic tools. Early alterations in endogenous NE machinery in atypical Parkinsonism may represent a specific risk trait in forms characterized by a worse prognosis.

Longitudinal evaluation of the natural history of amyloid-β in plasma and brain

Plasma amyloid-β peptide concentration has recently been shown to have high accuracy to predict amyloid-β plaque burden in the brain. These amyloid-β plasma markers will allow wider screening of the population and simplify and reduce screening costs for therapeutic trials in Alzheimer's disease. The aim of this study was to determine how longitudinal changes in blood amyloid-β track with changes in brain amyloid-β. Australian Imaging, Biomarker and Lifestyle study participants with a minimum of two assessments were evaluated (111 cognitively normal, 7 mild cognitively impaired, 15 participants with Alzheimer's disease). Amyloid-β burden in the brain was evaluated through PET and was expressed in Centiloids. Total protein amyloid-β 42/40 plasma ratios were determined using ABtest® assays. We applied our method for obtaining natural history trajectories from short term data to measures of total protein amyloid-β 42/40 plasma ratios and PET amyloid-β. The natural history trajectory of total protein amyloid-β 42/40 plasma ratios appears to approximately mirror that of PET amyloid-β, with both spanning decades. Rates of change of 7.9% and 8.8%, were observed for total protein amyloid-β 42/40 plasma ratios and PET amyloid-β, respectively. The trajectory of plasma amyloid-β preceded that of brain amyloid-β by a median value of 6 years (significant at 88% confidence interval). These findings, showing the tight association between changes in plasma and brain amyloid-β, support the use of plasma total protein amyloid-β 42/40 plasma ratios as a surrogate marker of brain amyloid-β. Also, that plasma total protein amyloid-β 42/40 plasma ratios has potential utility in monitoring trial participants, and as an outcome measure.

Towards a treatment for genetic prion disease: trials and biomarkers

Prion disease is a rare, fatal, and exceptionally rapid neurodegenerative disease. Although incurable, prion disease follows a clear pathogenic mechanism, in which a single gene gives rise to a single prion protein (PrP) capable of converting into the sole causal disease agent, the misfolded prion. As efforts progress to leverage this mechanistic knowledge toward rational therapies, a principal challenge will be the design of clinical trials. Previous trials in prion disease have been done in symptomatic patients who are often profoundly debilitated at enrolment. About 15% of prion disease cases are genetic, creating an opportunity for early therapeutic intervention to delay or prevent disease. Highly variable age of onset and absence of established prodromal biomarkers might render infeasible existing models for testing drugs before disease onset. Advancement of near-term targeted therapeutics could crucially depend on thoughtful design of rigorous presymptomatic trials.

Diagnostic Accuracy of Prion Disease Biomarkers in Iatrogenic Creutzfeldt-Jakob Disease

Human prion diseases are classified into sporadic, genetic, and acquired forms. Within this last group, iatrogenic Creutzfeldt-Jakob disease (iCJD) is caused by human-to-human transmission through surgical and medical procedures. After reaching an incidence peak in the 1990s, it is believed that the iCJD historical period is probably coming to an end, thanks to lessons learnt from past infection sources that promoted new prion prevention and decontamination protocols. At this point, we sought to characterise the biomarker profile of iCJD and compare it to that of sporadic CJD (sCJD) for determining the value of available diagnostic tools in promptly recognising iCJD cases. To that end, we collected 23 iCJD samples from seven national CJD surveillance centres and analysed the electroencephalogram and neuroimaging data together with a panel of seven CSF biomarkers: 14-3-3, total tau, phosphorylated/total tau ratio, alpha-synuclein, neurofilament light, YKL-40, and real-time quaking induced conversion of prion protein. Using the cut-off values established for sCJD, we found the sensitivities of these biomarkers for iCJD to be similar to those described for sCJD. Given the limited relevant information on this issue to date, the present study validates the use of current sCJD biomarkers for the diagnosis of future iCJD cases.