Omar El-Agnaf - Academia.edu (original) (raw)
Papers by Omar El-Agnaf
Movement Disorders, 2021
A BS TRACT: Background: Tangible efforts have been made to identify biomarkers for Parkinson's di... more A BS TRACT: Background: Tangible efforts have been made to identify biomarkers for Parkinson's disease (PD) diagnosis and progression, with α-synuclein (α-syn) related biomarkers being at the forefront. Objectives: The objectives of this study were to explore whether cerebrospinal fluid (CSF) levels of total, oligomeric, phosphorylated Ser 129 α-synuclein, along with total tau, phosphorylated tau 181, and β-amyloid 1-42 are (1) informative as diagnostic markers for PD, (2) changed over disease progression, and/or (3) correlated with motor and cognitive indices of disease progression in the longitudinal De Novo Parkinson cohort. Methods: A total of 94 de novo PD patients and 52 controls at baseline and 24-and 48-month follow-up were included, all of whom had longitudinal lumbar punctures and clinical assessments for both cognitive and motor functions. Using our in-house enzymelinked immunosorbent assays and commercially available assays, different forms of α-synuclein, tau, and β-amyloid 1-42 were quantified in CSF samples from the De Novo Parkinson cohort. Results: Baseline CSF total α-synuclein was significantly lower in early de novo PD compared with healthy controls, whereas the ratio of oligomeric/total and phosphorylated/total were significantly higher in the PD group. CSF oligomeric-α-synuclein longitudinally increased over the 4-year follow-up in the PD group and correlated with PD motor progression. Patients at advanced stages of PD presented with elevated CSF oligomeric-α-synuclein levels compared with healthy controls. Conclusions: Longitudinal transitions of CSF biomarkers over disease progression might not occur linearly and are susceptible to disease state. CSF oligomeric-α-synuclein levels appear to increase with diseases severity and reflect PD motor rather than cognitive trajectories.
Frontiers in Aging Neuroscience, 2021
Background: The role of cerebrospinal fluid (CSF) alpha-synuclein as a potential biomarker has be... more Background: The role of cerebrospinal fluid (CSF) alpha-synuclein as a potential biomarker has been challenged mainly due to variable preanalytical measures between laboratories. To evaluate the impact of the preanalytical factors contributing to such variability, the different subforms of alpha-synuclein need to be studied individually.Method: We investigated the effect of exposing CSF samples to several preanalytical sources of variability: (1) different polypropylene (PP) storage tubes; (2) use of non-ionic detergents; (3) multiple tube transfers; (4) multiple freeze-thaw cycles; and (5) delayed storage. CSF oligomeric- and total-alpha-synuclein levels were estimated using our in-house sandwich-based enzyme-linked immunosorbent assays.Results: Siliconized tubes provided the optimal preservation of CSF alpha-synuclein proteins among other tested polypropylene tubes. The use of tween-20 detergent significantly improved the recovery of oligomeric-alpha-synuclein, while multiple free...
Translational Neurodegeneration, 2020
Background Asymptomatic carriers of leucine-rich repeat kinase 2 (LRRK2) gene mutations constitut... more Background Asymptomatic carriers of leucine-rich repeat kinase 2 (LRRK2) gene mutations constitute an ideal population for discovering prodromal biomarkers of Parkinson’s disease (PD). In this study, we aim to identify CSF candidate risk biomarkers of PD in individuals with LRRK2 mutation carriers. Methods We measured the levels of CSF total- (t-), oligomeric (o-) and phosphorylated S129 (pS129-) α-syn, total-tau (tTau), phosphorylated threonine 181 tau (pTau), amyloid-beta 40 (Aβ-40), amyloid-beta-42 (Aβ-42) and 40 inflammatory chemokines in symptomatic (n = 23) and asymptomatic (n = 51) LRRK2 mutation carriers, subjects with a clinical diagnosis of PD (n = 60) and age-matched healthy controls (n = 34). General linear models corrected for age and gender were performed to assess differences in CSF biomarkers between the groups. Markers that varied significantly between the groups were then analyzed using backward-elimination logistic regression analysis to identify an ideal biomarke...
Journal of Neurochemistry, 2019
Parkinson's disease is the second most common neurodegenerative disorder after Alzheimer's diseas... more Parkinson's disease is the second most common neurodegenerative disorder after Alzheimer's disease and is estimated to affect approximately 1-4% of individuals aged over 60 years old. Although considerable efforts have been invested into developing disease-modifying therapies for Parkinson's disease, such efforts have been confounded by the difficulty in accurately diagnosing Parkinson's disease during life to enable accurate patient stratification for clinical trialling of candidate therapeutics. Therefore, the search for effective biomarkers that can be accurately evaluated during life with non-invasive means is a pressing issue in the field. Since the discovery of α-synuclein as a protein linked to a familial form of Parkinson's disease, later identified as the major protein component of the neuropathological hallmark of idiopathic Parkinson's disease, considerable interest has focused on this protein and its distinct conformers. We describe here the progress that has been made in the area of Parkinson's disease biomarker discovery with a focus on α-synuclein. In particular, we highlight the novel assays that have been employed and the increasing complexity in evaluating α-synuclein with regard to the considerable diversity of conformers that exist in the biofluids and peripheral tissues under disease conditions. Abbreviations used α-syn-alpha-synuclein CSF-cerebrospinal fluid DATATOP-Deprenyl and tocopherol antioxidative therapy of parkinsonism DeNoPA-De novo parkinson's disease DLB-dementia with lewy bodies ELISA-enzyme linked immunosorbent assay LB-Lewy body o-α-syn-oligomeric α-syn PD-Parkinson's disease PMCA-protein misfolding cyclic amplification PPMI-Parkinson's progression markers initiative pS129 α-syn-phosphorylated α-syn at S129 PSP-progressive supranuclear palsy RT-QuIC-real-time quaking-induced conversion
Journal of neurochemistry, Jan 20, 2018
α-Synuclein is the major component of Lewy bodies (LBs) and a candidate biomarker for neurodegene... more α-Synuclein is the major component of Lewy bodies (LBs) and a candidate biomarker for neurodegenerative diseases in which LBs are common, including Parkinson's disease and dementia with Lewy bodies. A large body of literature suggests that these disorders are characterised by reduced concentrations of α-synuclein in cerebrospinal fluid (CSF), with overlapping concentrations compared to healthy controls and variability across studies. Several reasons can account for this variability, including technical ones, such as inter-assay and inter-laboratory variation (reproducibility). We compared four (4) immunochemical methods for the quantification of α-synuclein concentration in 50 unique CSF samples. All methods were designed to capture most of the existing α-synuclein forms in CSF ("total" α-synuclein). Each of the four methods showed high analytical precision, excellent correlation between laboratories (R 0.83-0.99) and good correlation with each other (R 0.64-0.93), alt...
Movement disorders : official journal of the Movement Disorder Society, Jan 22, 2017
Parkinson's disease biomarkers are needed to increase diagnostic accuracy, to objectively mon... more Parkinson's disease biomarkers are needed to increase diagnostic accuracy, to objectively monitor disease progression and to assess therapeutic efficacy as well as target engagement when evaluating novel drug and therapeutic strategies. This article summarizes perianalytical considerations for biomarker studies (based on immunoassays) in Parkinson's disease, with emphasis on quantifying total α-synuclein protein in biological fluids. Current knowledge and pitfalls are discussed, and selected perianalytical variables are presented systematically, including different temperature of sample collection and types of collection tubes, gradient sampling, the addition of detergent, aliquot volume, the freezing time, and the different thawing methods. We also discuss analytical confounders. We identify gaps in the knowledge and delineate specific areas that require further investigation, such as the need to identify posttranslational modifications of α-synuclein and antibody-independe...
Journal of neural transmission (Vienna, Austria : 1996), Jan 5, 2017
Braak and Del Tredici have proposed that typical Parkinson disease (PD) has its origins in the ol... more Braak and Del Tredici have proposed that typical Parkinson disease (PD) has its origins in the olfactory bulb and gastrointestinal tract. However, the role of the olfactory system has insufficiently been explored in the pathogeneses of PD and Alzheimer disease (AD) in laboratory models. Here, we demonstrate applications of a new method to process mouse heads for microscopy by sectioning, mounting, and staining whole skulls ('holocranohistochemistry'). This technique permits the visualization of the olfactory system from the nasal cavity to mitral cells and dopamine-producing interneurons of glomeruli in the olfactory bulb. We applied this method to two specific goals: first, to visualize PD- and AD-linked gene expression in the olfactory system, where we detected abundant, endogenous α-synuclein and tau expression in the olfactory epithelium. Furthermore, we observed amyloid-β plaques and proteinase-K-resistant α-synuclein species, respectively, in cranial nerve-I of APP- an...
PloS one, 2016
The quantification of four distinct proteins (α-synuclein, β-amyloid1-42, DJ-1, and total tau) in... more The quantification of four distinct proteins (α-synuclein, β-amyloid1-42, DJ-1, and total tau) in cerebrospinal fluid (CSF) has been proposed as a laboratory-based platform for the diagnosis of Parkinson's disease (PD) and Alzheimer's disease (AD). While there is some clinical utility in measuring these markers individually, their usage in routine clinical testing remains challenging, in part due to substantial overlap of concentrations between healthy controls and diseased subjects. In contrast, measurement of different analytes in a single sample from individual patients in parallel appears to considerably improve the accuracy of AD or PD diagnosis. Here, we report the development and initial characterization of a first, electrochemiluminescence-based multiplex immunoassay for the simultaneous quantification of all four proteins ('tetraplex') in as little as 50 μl of CSF. In analytical performance experiments, we assessed its sensitivity, spike-recovery rate, paral...
Biomarkers in Medicine, 2016
The discovery of α-synuclein (α-syn) as a major component of Lewy bodies, neuropathological hallm... more The discovery of α-synuclein (α-syn) as a major component of Lewy bodies, neuropathological hallmark of Parkinson's disease (PD), dementia with Lewy bodies and of glial inclusions in multiple system atrophy initiated the investigation of α-syn as a biomarker in cerebrospinal fluid (CSF). Due to the involvement of the periphery in PD the quantification of α-syn in peripheral fluids such as serum, plasma and saliva has been investigated as well. We review how the development of multiple assays for the quantification of α-syn has yielded novel insights into the variety of α-syn species present in the different fluids; the optimal preanalytical conditions required for robust quantification and the potential clinical value of α-syn as biomarker. We also suggest future approaches to use of CSF α-syn in neurodegenerative diseases.
Current Medicinal Chemistry-Immunology, Endocrine & Metabolic Agents, 2003
The deposition of abnormal protein fibrils is a prominent pathological feature of many different ... more The deposition of abnormal protein fibrils is a prominent pathological feature of many different 'protein conformational' diseases, including some important neurodegenerative diseases. Some of the fibril-forming proteins or peptides associated with these diseases have been shown to be toxic to cells in culture. A clear understanding of the molecular mechanisms responsible for this toxicity should shed light on the probable link between protein deposition and cell loss in these diseases. In the case of the β-amyloid (Aβ) peptide, which accumulates in the brain in Alzheimer's disease, there is good evidence that the toxic mechanism involves the production of reactive oxygen species (ROS). By means of an electron spin resonance (ESR) spin-trapping method, we have shown that solutions of Aβ liberate hydroxyl radicals when incubated in vitro, upon the addition of small amounts of Fe(II). We have also obtained similar results with α-synuclein, which accumulates in Lewy bodies in Parkinson's disease, and with the PrP (106-126) toxic fragment of the prion protein. It is becoming clear that some transition metal ions, especially Fe(III) and Cu(II), can bind to these aggregating peptides, and that some of them can reduce the oxidation state of Fe(III) and/or Cu(II). The data suggest that hydrogen peroxide accumulates during incubation of these various proteins and peptides, and is subsequently converted to hydroxyl radicals in the presence of redox-active transition metal ions. Consequently, a fundamental molecular mechanism underlying the pathogenesis of cell death in several different neurodegenerative diseases could be the direct production of ROS during formation of the abnormal protein aggregates.
Parkinsonism & Related Disorders, 2014
The quantification of a-synuclein (aSyn) in cerebrospinal fluid (CSF) has been proposed as a diag... more The quantification of a-synuclein (aSyn) in cerebrospinal fluid (CSF) has been proposed as a diagnostic biomarker for Parkinson's disease and other aSyn-related diseases, such as multiple system atrophy and dementia with Lewy bodies. Most studies show decreased levels of aSyn in diseased CSF samples compared to control samples, but discrepant findings and overlapping values have been a major limitation for the use of CSF aSyn as a biomarker. This review addresses the current knowledge and investigates whether CSF aSyn is an ideal biomarker that can detect fundamental neuropathology features. It will also discuss whether CSF aSyn has been validated in neuropathologically confirmed cases, whether it shows a diagnostic sensitivity and whether it has a specificity above 80%. The review of current literature will also determine if sampling CSF aSyn is reliable, reproducible, noninvasive, simple to perform, inexpensive, and whether it has been investigated by at least two independent studies. CSF aSyn appears to meet most of these criteria, which have been proposed for ideal biomarkers, but further validation of this and other markers is needed to best introduce a panel of biomarkers in the early and differential diagnosis of Parkinson's disease.
Neurobiology of Aging, 2000
Both environmental and genetic factors are involved in Alaheimer's disease etiology. Mutations in... more Both environmental and genetic factors are involved in Alaheimer's disease etiology. Mutations in APP and in PSI and PS2 genes are causing early-onset forms of the disease while the ApoE allele is a risk factor for AD. Overexpression of mutated forms of APP in transgenic animals has now been shown to lead to amyloid plaque formation and this phenotype was significantly accelerated by co-expression of mutated human presenilin. Mutations in APP and presenilin, both increase the amount of Abeta 1-42 which is likely to be a key player in the pathology of AD. Yet, the pathological mechanisms leading to neuronal loss observed in AD are still unknown but additional external stress factors like trauma or lesions further contribute to the development of AD in these animals. We have generated several human mutant APP transgenic mice with moderate to high expression levels of the tmnsgene and transgenic mice which express high levels of human presenilin protein in the brain. Abeta peptide production is clearly detected in these animals. Endoproteolytic processing of human PS Ml46L is clearly detectable in the transgenic mice. However, the combination of five PSI mutations in one single transgene does significantly alter the cleavage pattern of PSI. Combining overexpression of APP with mutant PSI significantly accelerates the onset of plaque formation in the brain of the double transgenic mice, resulting in Abeta deposition as early as nine month of age. Concommittant with the onset of plaque development, a strong increase of steady state levels of Abeta can be detected by Western-blot. The present results demonstrate that amyloid plaque development in transgenic mice correlates with the amount of Abeta and can be signifcantly accelerated by PSI mutations. This approach represents a model to detect a toxic gain-of-function of high Abeta concentration in the brain together wth abnormal high PSI concentrations in neumnal cells. A better understanding of PS and APP physiological functions and the mechanism(s) by which the mutations are leading to neurodegeneration will be a key issue to develop an effective therapeutic strategy against AD.
Neurobiology of Aging, 2000
Alrheimer's disease (AD) is a complex neurodegenerative disorder, for which several disease-assoc... more Alrheimer's disease (AD) is a complex neurodegenerative disorder, for which several disease-associated loci have been located on various chromosomes. In order to find novel susceptibility genes for late onset AD, we have performed a population based genome-wide search using linkage disequilibrium (LD) mapping. To avoid population stratification, 47 late onset AD patients and 51 age-matched controls were carefully chosen from the same geographical area in Eastern Finland, where the population is mainly descended from a small group of original founders who migrated to the region in the late 16th and early 17th century Initial genome-wide screening with 366 polymorphic microsatellite markers revealed 22 chromosomal loci associated with AD with Fischer s exact test P-values in the range of 0.05 > P > 0.001. Subsequent comparison of single allele frequencies of the microsatellite markers in the AD and control groups indicated the presence of risk alleles displaying suggestive association with AD (odds ratios ranging from 2.0 to 5.0). In addition, according to single allele tests, certain markers revealed significantly lower frequencies of particular alleles in the AD group than in the control group suggesting a protective effect for these alleles against the development of AD (odds rations ranging from 0.1 to 0.5). Screening of the 22 LD regions with additional microsatellite markers revealed eight chmmosomal loci in 1~36, 2~22, 3q28,4pl2-13, lOp13, 13q12, 18q12 and 19~13 to be associated with AD with more than one microsatellite marker and the sizes of these LD regions were estimated to be 0.2-2.7 centiMorgans. These data suggest that there exist several AD-associated chromosomal loci, which may encompass novel susceptibility genes for late onset AD. Therefore, extensive screening of the genes located in the vicinity of these LD regions is necessary to elucidate their role in AD.
The Lancet Neurology, 2003
Human Molecular Genetics, 2009
a-Synuclein (SNCA) gene has been implicated in the development of rare forms of familial Parkinso... more a-Synuclein (SNCA) gene has been implicated in the development of rare forms of familial Parkinson disease (PD). Recently, it was shown that an increase in SNCA copy numbers leads to elevated levels of wild-type SNCA-mRNA and protein and is sufficient to cause early-onset, familial PD. A critical question concerning the molecular pathogenesis of PD is what contributory role, if any, is played by the SNCA gene in sporadic PD. The expansion of SNCA-Rep1, an upstream, polymorphic microsatellite of the SNCA gene, is associated with elevated risk for sporadic PD. However, whether SNCA-Rep1 is the causal variant and the underlying mechanism with which its effect is mediated by remained elusive. We report here the effects of three distinct SNCA-Rep1 variants in the brains of 72 mice transgenic for the entire human SNCA locus. Human SNCA-mRNA and protein levels were increased 1.7-and 1.25-fold, respectively, in homozygotes for the expanded, PD risk-conferring allele compared with homozygotes for the shorter, protective allele. When adjusting for the total SNCA-protein concentration (endogenous mouse and transgenic human) expressed in each brain, the expanded risk allele contributed 2.6-fold more to the SNCA steady-state than the shorter allele. Furthermore, targeted deletion of Rep1 resulted in the lowest human SNCA-mRNA and protein concentrations in murine brain. In contrast, the Rep1 effect was not observed in blood lysates from the same mice. These results demonstrate that Rep1 regulates human SNCA expression by enhancing its transcription in the adult nervous system and suggest that homozygosity for the expanded Rep1 allele may mimic locus multiplication, thereby elevating PD risk.
Experimental Neurology, 2008
Because accumulation of α-synuclein (αS) in the brain is a hallmark of Parkinson disease (PD) and... more Because accumulation of α-synuclein (αS) in the brain is a hallmark of Parkinson disease (PD) and related disorders, we examined its occurrence in human cerebrospinal fluid (CSF). Following affinity enrichment and trypsin digestion of CSF collected from a neurologically healthy donor, we identified several αS-derived peptides by mass spectrometry. The concentration of αS amounted to b 0.001% of the CSF proteome. We then built, validated and optimized a sandwich-type, enzyme-linked immunoadsorbent assay (ELISA) to measure total αS levels in unconcentrated CSF. In a cross-sectional study of 100 living donors, we examined cell-free CSF samples from subjects clinically diagnosed with advanced PD, dementia with Lewy bodies (DLB), Alzheimer disease (AD), and a group of non-neurodegenerative disease controls (NCO). In these four groups the CSF αS concentrations ranged from 0.8 to 16.2 pg/μl. Mean CSF αS values were lower in donors with a primary synucleinopathy (PD, DLB: n = 57) than in the other two groups (AD, NCO: n = 35; p = 0.025). By contrast, living Creutzfeldt-Jakob disease patients showed markedly elevated CSF αS levels (n = 8; mean, 300 pg/μl; p b 0.001). Our results unequivocally confirm the presence of αS in adult human CSF. In a first feasibility study employing a novel ELISA, we found relatively low CSF αS concentrations in subjects with parkinsonism linked to synucleinopathy, PD and DLB. In definite prion disease cases, we recorded a marked rise in total CSF αS resulting from rapid cell death. Our results will likely aid future biomarker explorations in neurodegenerative conditions and facilitate target validation studies.
Biochemical and Biophysical Research Communications, 2006
There is ample biochemical, pathological, and genetic evidence that the metabolism of a-synuclein... more There is ample biochemical, pathological, and genetic evidence that the metabolism of a-synuclein (a-syn) plays a crucial role in the pathogenesis of Parkinson disease (PD). To examine whether quantification of a-syn in cerebrospinal fluid (CSF) is potentially informative in the diagnosis of PD, we developed a specific ELISA system and measured the concentration of a-syn in CSF from 33 patients with PD (diagnosed according to UK PD Society Brain Bank criteria) and 38 control subjects including 9 neurologically healthy individuals. We found that PD patients had significantly lower a-syn levels in their CSF than the control groups (p < 0.0001) even after adjusting for gender and age. Age was independently associated with lower a-syn levels. Logistic regression analysis showed that reduction in CSF asyn served as a significant predictor of PD beyond age and gender alone (area under ROC curve, c = 0.882). Furthermore, we observed a close inverse correlation between a-syn levels in CSF and assigned Hoehn and Yahr score in this cohort of 71 living subjects (p < 0.0001), even after adjusting for age. These findings identify in the quantification of a-syn from CSF a potential laboratory marker to aid the clinical diagnosis of PD.
Alzheimer's & Dementia, 2009
The FASEB Journal, 2006
To date there is no accepted clinical diagnostic test for Parkinson&amp;amp;amp;amp;amp;a... more To date there is no accepted clinical diagnostic test for Parkinson&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease (PD) based on biochemical analysis of blood or cerebrospinal fluid (CSF). alpha-Synuclein (alpha-syn) protein has been linked to the pathogenesis of PD with the discovery of mutations in the gene encoding alpha-syn in familial cases with early-onset PD. Lewy bodies and Lewy neurites, which constitute the main pathological features in the brains of patients with sporadic PD and dementia with Lewy bodies, are formed by the conversion of soluble monomers of alpha-syn into insoluble aggregates. We recently reported the presence of alpha-syn in normal human blood plasma and in postmortem CSF. Here, we investigated whether alpha-syn can be used as a biomarker for PD. We have developed a novel ELISA method that detects only oligomeric &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;soluble aggregates&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; of alpha-syn. Using this ELISA, we report the presence of significantly elevated (P=0.002) levels of oligomeric forms of alpha-syn in plasma samples obtained from 34 PD patients compared with 27 controls; 52% (95% confidence intervals 0.353-0.687) of the PD patients displayed signals &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;0.5 OD with our ELISA assay in comparison to only 14.8% (95% confidence intervals 0.014-0.281) for the control cases. An analysis of the test&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s diagnostic value revealed a specificity of 0.852 (95% confidence intervals 0.662-0.958), sensitivity of 0.529 (95% confidence intervals 0.351-0.702) and a positive predictive value of 0.818 (95% confidence intervals 0.597-0.948). These observations offer new opportunities for developing diagnostic tests for PD and related diseases and for testing therapeutic agents aimed at preventing or reversing the aggregation of alpha-syn.
Movement Disorders, 2021
A BS TRACT: Background: Tangible efforts have been made to identify biomarkers for Parkinson's di... more A BS TRACT: Background: Tangible efforts have been made to identify biomarkers for Parkinson's disease (PD) diagnosis and progression, with α-synuclein (α-syn) related biomarkers being at the forefront. Objectives: The objectives of this study were to explore whether cerebrospinal fluid (CSF) levels of total, oligomeric, phosphorylated Ser 129 α-synuclein, along with total tau, phosphorylated tau 181, and β-amyloid 1-42 are (1) informative as diagnostic markers for PD, (2) changed over disease progression, and/or (3) correlated with motor and cognitive indices of disease progression in the longitudinal De Novo Parkinson cohort. Methods: A total of 94 de novo PD patients and 52 controls at baseline and 24-and 48-month follow-up were included, all of whom had longitudinal lumbar punctures and clinical assessments for both cognitive and motor functions. Using our in-house enzymelinked immunosorbent assays and commercially available assays, different forms of α-synuclein, tau, and β-amyloid 1-42 were quantified in CSF samples from the De Novo Parkinson cohort. Results: Baseline CSF total α-synuclein was significantly lower in early de novo PD compared with healthy controls, whereas the ratio of oligomeric/total and phosphorylated/total were significantly higher in the PD group. CSF oligomeric-α-synuclein longitudinally increased over the 4-year follow-up in the PD group and correlated with PD motor progression. Patients at advanced stages of PD presented with elevated CSF oligomeric-α-synuclein levels compared with healthy controls. Conclusions: Longitudinal transitions of CSF biomarkers over disease progression might not occur linearly and are susceptible to disease state. CSF oligomeric-α-synuclein levels appear to increase with diseases severity and reflect PD motor rather than cognitive trajectories.
Frontiers in Aging Neuroscience, 2021
Background: The role of cerebrospinal fluid (CSF) alpha-synuclein as a potential biomarker has be... more Background: The role of cerebrospinal fluid (CSF) alpha-synuclein as a potential biomarker has been challenged mainly due to variable preanalytical measures between laboratories. To evaluate the impact of the preanalytical factors contributing to such variability, the different subforms of alpha-synuclein need to be studied individually.Method: We investigated the effect of exposing CSF samples to several preanalytical sources of variability: (1) different polypropylene (PP) storage tubes; (2) use of non-ionic detergents; (3) multiple tube transfers; (4) multiple freeze-thaw cycles; and (5) delayed storage. CSF oligomeric- and total-alpha-synuclein levels were estimated using our in-house sandwich-based enzyme-linked immunosorbent assays.Results: Siliconized tubes provided the optimal preservation of CSF alpha-synuclein proteins among other tested polypropylene tubes. The use of tween-20 detergent significantly improved the recovery of oligomeric-alpha-synuclein, while multiple free...
Translational Neurodegeneration, 2020
Background Asymptomatic carriers of leucine-rich repeat kinase 2 (LRRK2) gene mutations constitut... more Background Asymptomatic carriers of leucine-rich repeat kinase 2 (LRRK2) gene mutations constitute an ideal population for discovering prodromal biomarkers of Parkinson’s disease (PD). In this study, we aim to identify CSF candidate risk biomarkers of PD in individuals with LRRK2 mutation carriers. Methods We measured the levels of CSF total- (t-), oligomeric (o-) and phosphorylated S129 (pS129-) α-syn, total-tau (tTau), phosphorylated threonine 181 tau (pTau), amyloid-beta 40 (Aβ-40), amyloid-beta-42 (Aβ-42) and 40 inflammatory chemokines in symptomatic (n = 23) and asymptomatic (n = 51) LRRK2 mutation carriers, subjects with a clinical diagnosis of PD (n = 60) and age-matched healthy controls (n = 34). General linear models corrected for age and gender were performed to assess differences in CSF biomarkers between the groups. Markers that varied significantly between the groups were then analyzed using backward-elimination logistic regression analysis to identify an ideal biomarke...
Journal of Neurochemistry, 2019
Parkinson's disease is the second most common neurodegenerative disorder after Alzheimer's diseas... more Parkinson's disease is the second most common neurodegenerative disorder after Alzheimer's disease and is estimated to affect approximately 1-4% of individuals aged over 60 years old. Although considerable efforts have been invested into developing disease-modifying therapies for Parkinson's disease, such efforts have been confounded by the difficulty in accurately diagnosing Parkinson's disease during life to enable accurate patient stratification for clinical trialling of candidate therapeutics. Therefore, the search for effective biomarkers that can be accurately evaluated during life with non-invasive means is a pressing issue in the field. Since the discovery of α-synuclein as a protein linked to a familial form of Parkinson's disease, later identified as the major protein component of the neuropathological hallmark of idiopathic Parkinson's disease, considerable interest has focused on this protein and its distinct conformers. We describe here the progress that has been made in the area of Parkinson's disease biomarker discovery with a focus on α-synuclein. In particular, we highlight the novel assays that have been employed and the increasing complexity in evaluating α-synuclein with regard to the considerable diversity of conformers that exist in the biofluids and peripheral tissues under disease conditions. Abbreviations used α-syn-alpha-synuclein CSF-cerebrospinal fluid DATATOP-Deprenyl and tocopherol antioxidative therapy of parkinsonism DeNoPA-De novo parkinson's disease DLB-dementia with lewy bodies ELISA-enzyme linked immunosorbent assay LB-Lewy body o-α-syn-oligomeric α-syn PD-Parkinson's disease PMCA-protein misfolding cyclic amplification PPMI-Parkinson's progression markers initiative pS129 α-syn-phosphorylated α-syn at S129 PSP-progressive supranuclear palsy RT-QuIC-real-time quaking-induced conversion
Journal of neurochemistry, Jan 20, 2018
α-Synuclein is the major component of Lewy bodies (LBs) and a candidate biomarker for neurodegene... more α-Synuclein is the major component of Lewy bodies (LBs) and a candidate biomarker for neurodegenerative diseases in which LBs are common, including Parkinson's disease and dementia with Lewy bodies. A large body of literature suggests that these disorders are characterised by reduced concentrations of α-synuclein in cerebrospinal fluid (CSF), with overlapping concentrations compared to healthy controls and variability across studies. Several reasons can account for this variability, including technical ones, such as inter-assay and inter-laboratory variation (reproducibility). We compared four (4) immunochemical methods for the quantification of α-synuclein concentration in 50 unique CSF samples. All methods were designed to capture most of the existing α-synuclein forms in CSF ("total" α-synuclein). Each of the four methods showed high analytical precision, excellent correlation between laboratories (R 0.83-0.99) and good correlation with each other (R 0.64-0.93), alt...
Movement disorders : official journal of the Movement Disorder Society, Jan 22, 2017
Parkinson's disease biomarkers are needed to increase diagnostic accuracy, to objectively mon... more Parkinson's disease biomarkers are needed to increase diagnostic accuracy, to objectively monitor disease progression and to assess therapeutic efficacy as well as target engagement when evaluating novel drug and therapeutic strategies. This article summarizes perianalytical considerations for biomarker studies (based on immunoassays) in Parkinson's disease, with emphasis on quantifying total α-synuclein protein in biological fluids. Current knowledge and pitfalls are discussed, and selected perianalytical variables are presented systematically, including different temperature of sample collection and types of collection tubes, gradient sampling, the addition of detergent, aliquot volume, the freezing time, and the different thawing methods. We also discuss analytical confounders. We identify gaps in the knowledge and delineate specific areas that require further investigation, such as the need to identify posttranslational modifications of α-synuclein and antibody-independe...
Journal of neural transmission (Vienna, Austria : 1996), Jan 5, 2017
Braak and Del Tredici have proposed that typical Parkinson disease (PD) has its origins in the ol... more Braak and Del Tredici have proposed that typical Parkinson disease (PD) has its origins in the olfactory bulb and gastrointestinal tract. However, the role of the olfactory system has insufficiently been explored in the pathogeneses of PD and Alzheimer disease (AD) in laboratory models. Here, we demonstrate applications of a new method to process mouse heads for microscopy by sectioning, mounting, and staining whole skulls ('holocranohistochemistry'). This technique permits the visualization of the olfactory system from the nasal cavity to mitral cells and dopamine-producing interneurons of glomeruli in the olfactory bulb. We applied this method to two specific goals: first, to visualize PD- and AD-linked gene expression in the olfactory system, where we detected abundant, endogenous α-synuclein and tau expression in the olfactory epithelium. Furthermore, we observed amyloid-β plaques and proteinase-K-resistant α-synuclein species, respectively, in cranial nerve-I of APP- an...
PloS one, 2016
The quantification of four distinct proteins (α-synuclein, β-amyloid1-42, DJ-1, and total tau) in... more The quantification of four distinct proteins (α-synuclein, β-amyloid1-42, DJ-1, and total tau) in cerebrospinal fluid (CSF) has been proposed as a laboratory-based platform for the diagnosis of Parkinson's disease (PD) and Alzheimer's disease (AD). While there is some clinical utility in measuring these markers individually, their usage in routine clinical testing remains challenging, in part due to substantial overlap of concentrations between healthy controls and diseased subjects. In contrast, measurement of different analytes in a single sample from individual patients in parallel appears to considerably improve the accuracy of AD or PD diagnosis. Here, we report the development and initial characterization of a first, electrochemiluminescence-based multiplex immunoassay for the simultaneous quantification of all four proteins ('tetraplex') in as little as 50 μl of CSF. In analytical performance experiments, we assessed its sensitivity, spike-recovery rate, paral...
Biomarkers in Medicine, 2016
The discovery of α-synuclein (α-syn) as a major component of Lewy bodies, neuropathological hallm... more The discovery of α-synuclein (α-syn) as a major component of Lewy bodies, neuropathological hallmark of Parkinson's disease (PD), dementia with Lewy bodies and of glial inclusions in multiple system atrophy initiated the investigation of α-syn as a biomarker in cerebrospinal fluid (CSF). Due to the involvement of the periphery in PD the quantification of α-syn in peripheral fluids such as serum, plasma and saliva has been investigated as well. We review how the development of multiple assays for the quantification of α-syn has yielded novel insights into the variety of α-syn species present in the different fluids; the optimal preanalytical conditions required for robust quantification and the potential clinical value of α-syn as biomarker. We also suggest future approaches to use of CSF α-syn in neurodegenerative diseases.
Current Medicinal Chemistry-Immunology, Endocrine & Metabolic Agents, 2003
The deposition of abnormal protein fibrils is a prominent pathological feature of many different ... more The deposition of abnormal protein fibrils is a prominent pathological feature of many different 'protein conformational' diseases, including some important neurodegenerative diseases. Some of the fibril-forming proteins or peptides associated with these diseases have been shown to be toxic to cells in culture. A clear understanding of the molecular mechanisms responsible for this toxicity should shed light on the probable link between protein deposition and cell loss in these diseases. In the case of the β-amyloid (Aβ) peptide, which accumulates in the brain in Alzheimer's disease, there is good evidence that the toxic mechanism involves the production of reactive oxygen species (ROS). By means of an electron spin resonance (ESR) spin-trapping method, we have shown that solutions of Aβ liberate hydroxyl radicals when incubated in vitro, upon the addition of small amounts of Fe(II). We have also obtained similar results with α-synuclein, which accumulates in Lewy bodies in Parkinson's disease, and with the PrP (106-126) toxic fragment of the prion protein. It is becoming clear that some transition metal ions, especially Fe(III) and Cu(II), can bind to these aggregating peptides, and that some of them can reduce the oxidation state of Fe(III) and/or Cu(II). The data suggest that hydrogen peroxide accumulates during incubation of these various proteins and peptides, and is subsequently converted to hydroxyl radicals in the presence of redox-active transition metal ions. Consequently, a fundamental molecular mechanism underlying the pathogenesis of cell death in several different neurodegenerative diseases could be the direct production of ROS during formation of the abnormal protein aggregates.
Parkinsonism & Related Disorders, 2014
The quantification of a-synuclein (aSyn) in cerebrospinal fluid (CSF) has been proposed as a diag... more The quantification of a-synuclein (aSyn) in cerebrospinal fluid (CSF) has been proposed as a diagnostic biomarker for Parkinson's disease and other aSyn-related diseases, such as multiple system atrophy and dementia with Lewy bodies. Most studies show decreased levels of aSyn in diseased CSF samples compared to control samples, but discrepant findings and overlapping values have been a major limitation for the use of CSF aSyn as a biomarker. This review addresses the current knowledge and investigates whether CSF aSyn is an ideal biomarker that can detect fundamental neuropathology features. It will also discuss whether CSF aSyn has been validated in neuropathologically confirmed cases, whether it shows a diagnostic sensitivity and whether it has a specificity above 80%. The review of current literature will also determine if sampling CSF aSyn is reliable, reproducible, noninvasive, simple to perform, inexpensive, and whether it has been investigated by at least two independent studies. CSF aSyn appears to meet most of these criteria, which have been proposed for ideal biomarkers, but further validation of this and other markers is needed to best introduce a panel of biomarkers in the early and differential diagnosis of Parkinson's disease.
Neurobiology of Aging, 2000
Both environmental and genetic factors are involved in Alaheimer's disease etiology. Mutations in... more Both environmental and genetic factors are involved in Alaheimer's disease etiology. Mutations in APP and in PSI and PS2 genes are causing early-onset forms of the disease while the ApoE allele is a risk factor for AD. Overexpression of mutated forms of APP in transgenic animals has now been shown to lead to amyloid plaque formation and this phenotype was significantly accelerated by co-expression of mutated human presenilin. Mutations in APP and presenilin, both increase the amount of Abeta 1-42 which is likely to be a key player in the pathology of AD. Yet, the pathological mechanisms leading to neuronal loss observed in AD are still unknown but additional external stress factors like trauma or lesions further contribute to the development of AD in these animals. We have generated several human mutant APP transgenic mice with moderate to high expression levels of the tmnsgene and transgenic mice which express high levels of human presenilin protein in the brain. Abeta peptide production is clearly detected in these animals. Endoproteolytic processing of human PS Ml46L is clearly detectable in the transgenic mice. However, the combination of five PSI mutations in one single transgene does significantly alter the cleavage pattern of PSI. Combining overexpression of APP with mutant PSI significantly accelerates the onset of plaque formation in the brain of the double transgenic mice, resulting in Abeta deposition as early as nine month of age. Concommittant with the onset of plaque development, a strong increase of steady state levels of Abeta can be detected by Western-blot. The present results demonstrate that amyloid plaque development in transgenic mice correlates with the amount of Abeta and can be signifcantly accelerated by PSI mutations. This approach represents a model to detect a toxic gain-of-function of high Abeta concentration in the brain together wth abnormal high PSI concentrations in neumnal cells. A better understanding of PS and APP physiological functions and the mechanism(s) by which the mutations are leading to neurodegeneration will be a key issue to develop an effective therapeutic strategy against AD.
Neurobiology of Aging, 2000
Alrheimer's disease (AD) is a complex neurodegenerative disorder, for which several disease-assoc... more Alrheimer's disease (AD) is a complex neurodegenerative disorder, for which several disease-associated loci have been located on various chromosomes. In order to find novel susceptibility genes for late onset AD, we have performed a population based genome-wide search using linkage disequilibrium (LD) mapping. To avoid population stratification, 47 late onset AD patients and 51 age-matched controls were carefully chosen from the same geographical area in Eastern Finland, where the population is mainly descended from a small group of original founders who migrated to the region in the late 16th and early 17th century Initial genome-wide screening with 366 polymorphic microsatellite markers revealed 22 chromosomal loci associated with AD with Fischer s exact test P-values in the range of 0.05 > P > 0.001. Subsequent comparison of single allele frequencies of the microsatellite markers in the AD and control groups indicated the presence of risk alleles displaying suggestive association with AD (odds ratios ranging from 2.0 to 5.0). In addition, according to single allele tests, certain markers revealed significantly lower frequencies of particular alleles in the AD group than in the control group suggesting a protective effect for these alleles against the development of AD (odds rations ranging from 0.1 to 0.5). Screening of the 22 LD regions with additional microsatellite markers revealed eight chmmosomal loci in 1~36, 2~22, 3q28,4pl2-13, lOp13, 13q12, 18q12 and 19~13 to be associated with AD with more than one microsatellite marker and the sizes of these LD regions were estimated to be 0.2-2.7 centiMorgans. These data suggest that there exist several AD-associated chromosomal loci, which may encompass novel susceptibility genes for late onset AD. Therefore, extensive screening of the genes located in the vicinity of these LD regions is necessary to elucidate their role in AD.
The Lancet Neurology, 2003
Human Molecular Genetics, 2009
a-Synuclein (SNCA) gene has been implicated in the development of rare forms of familial Parkinso... more a-Synuclein (SNCA) gene has been implicated in the development of rare forms of familial Parkinson disease (PD). Recently, it was shown that an increase in SNCA copy numbers leads to elevated levels of wild-type SNCA-mRNA and protein and is sufficient to cause early-onset, familial PD. A critical question concerning the molecular pathogenesis of PD is what contributory role, if any, is played by the SNCA gene in sporadic PD. The expansion of SNCA-Rep1, an upstream, polymorphic microsatellite of the SNCA gene, is associated with elevated risk for sporadic PD. However, whether SNCA-Rep1 is the causal variant and the underlying mechanism with which its effect is mediated by remained elusive. We report here the effects of three distinct SNCA-Rep1 variants in the brains of 72 mice transgenic for the entire human SNCA locus. Human SNCA-mRNA and protein levels were increased 1.7-and 1.25-fold, respectively, in homozygotes for the expanded, PD risk-conferring allele compared with homozygotes for the shorter, protective allele. When adjusting for the total SNCA-protein concentration (endogenous mouse and transgenic human) expressed in each brain, the expanded risk allele contributed 2.6-fold more to the SNCA steady-state than the shorter allele. Furthermore, targeted deletion of Rep1 resulted in the lowest human SNCA-mRNA and protein concentrations in murine brain. In contrast, the Rep1 effect was not observed in blood lysates from the same mice. These results demonstrate that Rep1 regulates human SNCA expression by enhancing its transcription in the adult nervous system and suggest that homozygosity for the expanded Rep1 allele may mimic locus multiplication, thereby elevating PD risk.
Experimental Neurology, 2008
Because accumulation of α-synuclein (αS) in the brain is a hallmark of Parkinson disease (PD) and... more Because accumulation of α-synuclein (αS) in the brain is a hallmark of Parkinson disease (PD) and related disorders, we examined its occurrence in human cerebrospinal fluid (CSF). Following affinity enrichment and trypsin digestion of CSF collected from a neurologically healthy donor, we identified several αS-derived peptides by mass spectrometry. The concentration of αS amounted to b 0.001% of the CSF proteome. We then built, validated and optimized a sandwich-type, enzyme-linked immunoadsorbent assay (ELISA) to measure total αS levels in unconcentrated CSF. In a cross-sectional study of 100 living donors, we examined cell-free CSF samples from subjects clinically diagnosed with advanced PD, dementia with Lewy bodies (DLB), Alzheimer disease (AD), and a group of non-neurodegenerative disease controls (NCO). In these four groups the CSF αS concentrations ranged from 0.8 to 16.2 pg/μl. Mean CSF αS values were lower in donors with a primary synucleinopathy (PD, DLB: n = 57) than in the other two groups (AD, NCO: n = 35; p = 0.025). By contrast, living Creutzfeldt-Jakob disease patients showed markedly elevated CSF αS levels (n = 8; mean, 300 pg/μl; p b 0.001). Our results unequivocally confirm the presence of αS in adult human CSF. In a first feasibility study employing a novel ELISA, we found relatively low CSF αS concentrations in subjects with parkinsonism linked to synucleinopathy, PD and DLB. In definite prion disease cases, we recorded a marked rise in total CSF αS resulting from rapid cell death. Our results will likely aid future biomarker explorations in neurodegenerative conditions and facilitate target validation studies.
Biochemical and Biophysical Research Communications, 2006
There is ample biochemical, pathological, and genetic evidence that the metabolism of a-synuclein... more There is ample biochemical, pathological, and genetic evidence that the metabolism of a-synuclein (a-syn) plays a crucial role in the pathogenesis of Parkinson disease (PD). To examine whether quantification of a-syn in cerebrospinal fluid (CSF) is potentially informative in the diagnosis of PD, we developed a specific ELISA system and measured the concentration of a-syn in CSF from 33 patients with PD (diagnosed according to UK PD Society Brain Bank criteria) and 38 control subjects including 9 neurologically healthy individuals. We found that PD patients had significantly lower a-syn levels in their CSF than the control groups (p < 0.0001) even after adjusting for gender and age. Age was independently associated with lower a-syn levels. Logistic regression analysis showed that reduction in CSF asyn served as a significant predictor of PD beyond age and gender alone (area under ROC curve, c = 0.882). Furthermore, we observed a close inverse correlation between a-syn levels in CSF and assigned Hoehn and Yahr score in this cohort of 71 living subjects (p < 0.0001), even after adjusting for age. These findings identify in the quantification of a-syn from CSF a potential laboratory marker to aid the clinical diagnosis of PD.
Alzheimer's & Dementia, 2009
The FASEB Journal, 2006
To date there is no accepted clinical diagnostic test for Parkinson&amp;amp;amp;amp;amp;a... more To date there is no accepted clinical diagnostic test for Parkinson&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s disease (PD) based on biochemical analysis of blood or cerebrospinal fluid (CSF). alpha-Synuclein (alpha-syn) protein has been linked to the pathogenesis of PD with the discovery of mutations in the gene encoding alpha-syn in familial cases with early-onset PD. Lewy bodies and Lewy neurites, which constitute the main pathological features in the brains of patients with sporadic PD and dementia with Lewy bodies, are formed by the conversion of soluble monomers of alpha-syn into insoluble aggregates. We recently reported the presence of alpha-syn in normal human blood plasma and in postmortem CSF. Here, we investigated whether alpha-syn can be used as a biomarker for PD. We have developed a novel ELISA method that detects only oligomeric &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;soluble aggregates&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; of alpha-syn. Using this ELISA, we report the presence of significantly elevated (P=0.002) levels of oligomeric forms of alpha-syn in plasma samples obtained from 34 PD patients compared with 27 controls; 52% (95% confidence intervals 0.353-0.687) of the PD patients displayed signals &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;0.5 OD with our ELISA assay in comparison to only 14.8% (95% confidence intervals 0.014-0.281) for the control cases. An analysis of the test&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s diagnostic value revealed a specificity of 0.852 (95% confidence intervals 0.662-0.958), sensitivity of 0.529 (95% confidence intervals 0.351-0.702) and a positive predictive value of 0.818 (95% confidence intervals 0.597-0.948). These observations offer new opportunities for developing diagnostic tests for PD and related diseases and for testing therapeutic agents aimed at preventing or reversing the aggregation of alpha-syn.