Serum B-cell activating factor is not a potential biomarker for disease activity in chronic inflammatory demyelinating polyneuropathy.

B-cell activating factor (BAFF) is a crucial cytokine for differentiation and survival of B-cells and correlates to disease activity in some auto-immune diseases. To evaluate BAFF as a biomarker for disease activity in chronic inflammatory demyelinating polyneuropathy (CIDP), serum BAFF levels were measured at varying disease stages: patients starting treatment, patients starting treatment withdrawal, patients in remission and healthy controls. Serum BAFF levels were elevated in patients compared to healthy controls, but did not differ between patients starting treatment and patients in remission. Serum BAFF levels did not change with or predict treatment response or relapse. Serum BAFF is not a responsive biomarker reflecting disease activity in CIDP.

Long-term tactile hypersensitivity after nerve crush injury in mice is characterized by the persistence of intact sensory axons.

ABSTRACT: Traumatic peripheral nerve injuries are at high risk of neuropathic pain for which novel effective therapies are urgently needed. Preclinical models of neuropathic pain typically involve irreversible ligation and/or nerve transection (neurotmesis). However, translation of findings to the clinic has so far been unsuccessful, raising questions on injury model validity and clinically relevance. Traumatic nerve injuries seen in the clinic commonly result in axonotmesis (ie, crush), yet the neuropathic phenotype of "painful" nerve crush injuries remains poorly understood. We report the neuropathology and sensory symptoms of a focal nerve crush injury using custom-modified hemostats resulting in either complete ("full") or incomplete ("partial") axonotmesis in adult mice. Assays of thermal and mechanically evoked pain-like behavior were paralleled by transmission electron microscopy, immunohistochemistry, and anatomical tracing of the peripheral nerve. In both crush models, motor function was equally affected early after injury; by contrast, partial crush of the nerve resulted in the early return of pinprick sensitivity, followed by a transient thermal and chronic tactile hypersensitivity of the affected hind paw, which was not observed after a full crush injury. The partially crushed nerve was characterized by the sparing of small-diameter myelinated axons and intraepidermal nerve fibers, fewer dorsal root ganglia expressing the injury marker activating transcription factor 3, and lower serum levels of neurofilament light chain. By day 30, axons showed signs of reduced myelin thickness. In summary, the escape of small-diameter axons from Wallerian degeneration is likely a determinant of chronic pain pathophysiology distinct from the general response to complete nerve injury.

C1q is increased in cerebrospinal fluid-derived extracellular vesicles in Alzheimer's disease: A multi-cohort proteomics and immuno-assay validation study.

INTRODUCTION: Extracellular vesicles (EVs) may propagate and modulate Alzheimer's disease (AD) pathology. We aimed to comprehensively characterize the proteome of cerebrospinal fluid (CSF) EVs to identify proteins and pathways altered in AD. METHODS: CSF EVs were isolated by ultracentrifugation (Cohort 1) or Vn96 peptide (Cohort 2) from non-neurodegenerative controls (n = 15, 16) and AD patients (n = 22, 20, respectively). EVs were subjected to untargeted quantitative mass spectrometry-based proteomics. Results were validated by enzyme-linked immunosorbent assay (ELISA) in Cohorts 3 and 4, consisting of controls (n = 16, n = 43, (Cohort3, Cohort4)), and patients with AD (n = 24, n = 100). RESULTS: We found > 30 differentially expressed proteins in AD CSF EVs involved in immune-regulation. Increase of C1q levels in AD compared to non-demented controls was validated by ELISA (∼ 1.5 fold, p (Cohort 3) = 0.03, p (Cohort 4) = 0.005). DISCUSSION: EVs may be utilized as a potential biomarker and may play a so far unprecedented role in immune-regulation in AD.

Neuroaxonal and Glial Markers in Patients of the Same Age With Multiple Sclerosis.

BACKGROUND AND OBJECTIVES: The specificity of novel blood biomarkers for multiple sclerosis (MS)-related neurodegeneration is unclear because neurodegeneration also occurs during normal aging. To understand which aspects of neurodegeneration the serum biomarkers neurofilament light (sNfL), serum glial fibrillary acidic protein (sGFAP), and serum contactin-1 (sCNTN1) reflect, we here explore their cross-sectional association with disability outcome measures and MRI volumes in a unique cohort of people with MS (PwMS) of the same age. METHODS: sNfL, sGFAP (both singe-molecule array technology) and sCNTN1 (Luminex) were measured in serum samples of 288 PwMS and 125 healthy controls (HCs) of the Project Y cohort, a population-based cross-sectional study of PwMS born in the Netherlands in 1966 and age-matched HC. RESULTS: sNfL (9.83 pg/mL [interquartile range {IQR}: 7.8-12.0]) and sGFAP (63.7 pg/mL [IQR: 48.5-84.5]) were higher in PwMS compared with HC (sNfL: 8.8 pg/mL [IQR: 7.0-10.5]; sGFAP: 51.7 pg/mL [IQR: 40.1-68.3]) (p < 0.001), whereas contactin-1 (7,461.3 pg/mL [IQR: 5,951.8-9,488.6]) did not significantly differ between PwMS compared with HC (7,891.2 pg/mL [IQR: 6,120.0-10,265.8]) (p = 0.068). sNfL and sGFAP levels were 1.2-fold higher in secondary progressive patients (SPMS) compared with relapsing remitting patients (p = 0.009 and p = 0.043). Stratified by MS subtype, no relations were seen for CNTN1, whereas sNfL and sGFAP correlated with the Expanded Disability Status Scale (ρ = 0.43 and ρ = 0.39), Nine-Hole Peg Test, Timed 25-Foot Walk Test, and Symbol Digit Modalities Test (average ρ = 0.38) only in patients with SPMS. Parallel to these clinical findings, correlations were only found for sNfL and sGFAP with MRI volumes. The strongest correlations were observed between sNfL and thalamic volume (ρ = -0.52) and between sGFAP with deep gray matter volume (ρ = - 0.56) in primary progressive patients. DISCUSSION: In our cohort of patients of the same age, we report consistent correlations of sNfL and sGFAP with a range of metrics, especially in progressive MS, whereas contactin-1 was not related to clinical or MRI measures. This demonstrates the potential of sNfL and sGFAP as complementary biomarkers of neurodegeneration, reflected by disability, in progressive MS.

Pre-analytical stability of serum biomarkers for neurological disease: neurofilament-light, glial fibrillary acidic protein and contactin-1.

OBJECTIVES: Neurofilament-light (NfL), glial fibrillary acidic protein (GFAP) and contactin-1 (CNTN1) are blood-based biomarkers that could contribute to monitoring and prediction of disease and treatment outcomes in neurological diseases. Pre-analytical sample handling might affect results, which could be disease-dependent. We tested common handling variations in serum of volunteers as well as in a defined group of patients with multiple sclerosis (pwMS). METHODS: Sample sets from 5 pwMS and 5 volunteers at the outpatient clinic were collected per experiment. We investigated the effect of the following variables: collection tube type, delayed centrifugation, centrifugation temperature, delayed storage after centrifugation and freeze-thawing. NfL and GFAP were measured by Simoa and CNTN1 by Luminex. A median recovery of 90-110% was considered stable. RESULTS: For most pre-analytical variables, serum NfL and CNTN1 levels remained unaffected. In the total group, NfL levels increased (121%) after 6 h of delay at 2-8 °C until centrifugation, while no significant changes were observed after 24 h delay at room temperature (RT). In pwMS specifically, CNTN1 levels increased from additional freeze-thaw cycles number 2 to 4 (111%-141%), whereas volunteer levels remained stable. GFAP showed good stability for all pre-analytical variables. CONCLUSIONS: Overall, the serum biomarkers tested were relatively unaffected by variations in sample handling. For serum NfL, we recommend storage at RT before centrifugation at 2-8 °C up to 6 h or at RT up to 24 h. For serum CNTN1, we advise a maximum of two freeze-thaw cycles. Our results confirm and expand on recently launched consensus standardized operating procedures.

Serum neurofilament light chain, contactin-1 and complement activation in anti-MAG IgM paraprotein-related peripheral neuropathy.

INTRODUCTION: In anti-myelin-associated glycoprotein IgM paraprotein-related peripheral neuropathy (anti-MAG PN), there is a lack of reliable biomarkers to select patients eligible for therapy and for evaluating treatment effects, both in routine practice and in clinical trials. Neurofilament light chain (NfL) and contactin-1 (CNTN1) can serve as markers of axonal and paranodal damage. Complement activation is involved in the pathogenesis in anti-MAG PN. We, therefore, hypothesized that serum NfL, CNTN1, C3b/c and C4b/c may function as biomarkers of disease activity in anti-MAG PN. METHODS: In this prospective cohort study, we included 24 treatment-naïve patients with anti-MAG PN (mean age 69 years, 57% male) that had IgM paraproteinemia, a high IgM MAG-antibody, and clinical diagnosis of anti-MAG PN by a neurologist specialized in peripheral nerve disorders. We measured serum NfL, CNTN1, C3b/c and C4b/c, reference values were based on healthy controls. As controls, 10 treatment-naïve patients with IgM Monoclonal gammopathy of undetermined significance (MGUS) or Waldenström's Macroglobulinemia (mean age 69 years, 60% male) without signs of neuropathy were included (non-PN). RESULTS: NfL, CNTN1 levels in serum were mostly normal in anti-MAG PN patients and comparable to non-PN patients. C3b/c and C4b/c levels were normal in anti-MAG PN patients. CONCLUSION: Our results do not support serum NfL, CNTN1, and C3b/c and C4b/c as potential biomarkers in anti-MAG PN, although we cannot exclude that subgroups or subtle abnormalities could be found in a much larger cohort with longitudinal follow-up.

Serum contactin-1 as a biomarker of long-term disease progression in natalizumab-treated multiple sclerosis.

BACKGROUND: Natalizumab treatment provides a model for non-inflammation-induced disease progression in multiple sclerosis (MS). OBJECTIVE: To study serum contactin-1 (sCNTN1) as a novel biomarker for disease progression in natalizumab-treated relapsing-remitting MS (RRMS) patients. METHODS: Eighty-nine natalizumab-treated RRMS patients with minimum follow-up of 3 years were included. sCNTN1 was analyzed at baseline (before natalizumab initiation), 3, 12, 24 months (M) and last follow-up (median 5.2 years) and compared to 222 healthy controls (HC) and 15 primary progressive MS patients (PPMS). Results were compared between patients with progressive, stable, or improved disability according to EDSS-plus criteria. RESULTS: Median sCNTN1 levels (ng/mL,) in RRMS (baseline: 10.7, 3M: 9.7, 12M: 10.4, 24M: 10.8; last follow-up: 9.7) were significantly lower compared to HC (12.5; p ⩽ 0.001). It was observed that 48% of patients showed progression during follow-up, 11% improved, and 40% remained stable. sCNTN1 levels were significantly lower in progressors both at baseline and at 12M compared to non-progressors. A 1 ng/mL decrease in baseline sCNTN1 was consistent with an odds ratio of 1.23 (95% confidence interval 1.04-1.45) (p = 0.017) for progression during follow-up. CONCLUSION: Lower baseline sCNTN1 concentrations were associated with long-term disability progression during natalizumab treatment, making it a possible blood-based prognostic biomarker for RRMS.

Serum Contactin-1 in CIDP: A Cross-Sectional Study.

OBJECTIVE: To investigate whether serum levels of contactin-1, a paranodal protein, correlate with paranodal injury as seen in patients with CIDP with antibodies targeting the paranodal region. METHODS: Serum contactin-1 levels were measured in 187 patients with CIDP and 222 healthy controls. Paranodal antibodies were investigated in all patients. RESULTS: Serum contactin-1 levels were lower in patients (N = 41) with paranodal antibodies compared with patients (N = 146) without paranodal antibodies (p < 0.01) and showed good discrimination between these groups (area under the curve 0.84; 95% CI: 0.76-0.93). CONCLUSIONS: These findings suggest that serum contactin-1 levels have the potential to serve as a possible diagnostic biomarker of paranodal injury in CIDP. CLASSIFICATION OF EVIDENCE: This study provides class II evidence that serum contactin-1 levels can discriminate between patients with CIDP with or without paranodal antibodies with a sensitivity of 71% (95% CI: 56%-85%) and a specificity of 97% (95% CI: 83%-100%).

Ultrasensitive immunoassay allows measurement of serum neurofilament heavy in multiple sclerosis.

BACKGROUND: Neurofilament heavy (NfH) is a promising biomarker for neuro-axonal damage in Multiple Sclerosis (MS). We compared the performance of high-sensitivity serum-NfH immunoassays, with as aim to investigate the value of serum-NfH as biomarker for MS. METHODS: We measured serum-NfH in 76 MS patients with Simoa (one commercial, one in-house) or Luminex assays. Serum-NfH measured by the immunoassay with greatest sensitivity was related to clinical and radiological outcomes with age and sex-adjusted linear regression analysis, and to biological outcomes cerebrospinal fluid (CSF)-NfH, serum neurofilament light (NfL) and CSF-NfL with Spearman's correlation analysis. RESULTS: With the commercial Simoa assay, we obtained 100% serum-NfH detectability (in-house Simoa: 70%, Luminex: 61%), with lowest coefficient of variation (CV) between duplicates of 11%CV (in-house Simoa: 22%CV, Luminex: 30%CV). Serum-NfH quantified with the commercial Simoa assay was associated with disease duration (standardized beta (sß) = 0.28, p = 0.034), T2 lesion volume (sß = 0.23, p = 0.041), and tended to associate with black hole count (sß = 0.21, p = 0.084) but not with Expanded Disease Disability Score (EDSS) or normalized brain volume (all: p>0.10). Furthermore, serum-NfH showed correlations with CSF-NfH (rho = 0.27, p = 0.018) and serum-NfL (rho=0.44, p < 0.001), but not with CSF-NfL. CONCLUSIONS: Serum-NfH can be quantified with high-sensitivity technology. Cross-sectionally, we observed some weak correlations of serum-NfH with MS disease burden parameters, suggesting there might be some utility for serum-NfH as biomarker for MS disease burden.

A multi-center study of neurofilament assay reliability and inter-laboratory variability.

Objectives: Significantly elevated levels of neurofilament light chain (NfL) and phosphorylated neurofilament heavy chain (pNfH) have been described in the blood and cerebrospinal fluid (CSF) of amyotrophic lateral sclerosis (ALS) patients. The aim of this study was to evaluate the analytical performance of different neurofilament assays in a round robin with 10 centers across Europe/U.S. Methods: Serum, plasma and CSF samples from a group of five ALS and five neurological control patients were distributed across 10 international specialist neurochemical laboratories for analysis by a range of commercial and in-house neurofilament assays. The performance of all assays was evaluated for their ability to differentiate between the groups. The inter-assay coefficient of variation was calculated where appropriate from sample measurements performed across multiple laboratories using the same assay. Results: All assays could differentiate ALS patients from controls in CSF. Inter-assay coefficient of variation of analytical platforms performed across multiple laboratories varied between 6.5% and 41.9%. Conclusions: This study is encouraging for the growing momentum toward integration of neurofilament measurement into the specialized ALS clinic. It demonstrates the importance of 'round robin' studies necessary to ensure the analytical quality required for translation to the routine clinical setting. A standardized neurofilament probe is needed which can be used as international benchmark for analytical performance in ALS.

Identification of novel cerebrospinal fluid biomarker candidates for dementia with Lewy bodies: a proteomic approach.

BACKGROUND: Diagnosis of dementia with Lewy bodies (DLB) is challenging, largely due to a lack of diagnostic tools. Cerebrospinal fluid (CSF) biomarkers have been proven useful in Alzheimer's disease (AD) diagnosis. Here, we aimed to identify novel CSF biomarkers for DLB using a high-throughput proteomic approach. METHODS: We applied liquid chromatography/tandem mass spectrometry with label-free quantification to identify biomarker candidates to individual CSF samples from a well-characterized cohort comprising patients with DLB (n = 20) and controls (n = 20). Validation was performed using (1) the identical proteomic workflow in an independent cohort (n = 30), (2) proteomic data from patients with related neurodegenerative diseases (n = 149) and (3) orthogonal techniques in an extended cohort consisting of DLB patients and controls (n = 76). Additionally, we utilized random forest analysis to identify the subset of candidate markers that best distinguished DLB from all other groups. RESULTS: In total, we identified 1995 proteins. In the discovery cohort, 69 proteins were differentially expressed in DLB compared to controls (p < 0.05). Independent cohort replication confirmed VGF, SCG2, NPTX2, NPTXR, PDYN and PCSK1N as candidate biomarkers for DLB. The downregulation of the candidate biomarkers was somewhat more pronounced in DLB in comparison with related neurodegenerative diseases. Using random forest analysis, we identified a panel of VGF, SCG2 and PDYN to best differentiate between DLB and other clinical groups (accuracy: 0.82 (95%CI: 0.75-0.89)). Moreover, we confirmed the decrease of VGF and NPTX2 in DLB by ELISA and SRM methods. Low CSF levels of all biomarker candidates, except PCSK1N, were associated with more pronounced cognitive decline (0.37 < r < 0.56, all p < 0.01). CONCLUSION: We identified and validated six novel CSF biomarkers for DLB. These biomarkers, particularly when used as a panel, show promise to improve diagnostic accuracy and strengthen the importance of synaptic dysfunction in the pathophysiology of DLB.

VGF Peptides in Cerebrospinal Fluid of Patients with Dementia with Lewy Bodies.

In a previous proteomic study, we identified the neurosecretory protein VGF (VGF) as a potential biomarker for dementia with Lewy bodies (DLB). Here, we extended the study of VGF by comparing levels in cerebrospinal fluid (CSF) from 44 DLB patients, 20 Alzheimer's disease (AD) patients, and 22 cognitively normal controls selected from the Amsterdam Dementia Cohort. CSF was analyzed using two orthogonal analytical methods: (1) In-house-developed quantitative ELISA and (2) selected reaction monitoring (SRM). We further addressed associations of VGF with other CSF biomarkers and cognition. VGF levels were lower in CSF from patients with DLB compared to either AD patients or controls. VGF was positively correlated with CSF tau and α-synuclein (0.55 < r < 0.75), but not with Aß1-42. In DLB patients, low VGF levels were related to a more advanced cognitive decline at time of first presentation, whereas high levels of VGF were associated with steeper subsequent longitudinal cognitive decline. Hence, CSF VGF levels were lower in DLB compared to both AD and controls across different analytical methods. The strong associations with cognitive decline further points out VGF as a possible disease stage or prognostic marker for DLB.

No Plasmatic Proteomic Signature at Clinical Disease Onset Associated With 11 Year Clinical, Cognitive and MRI Outcomes in Relapsing-Remitting Multiple Sclerosis Patients.

Background: The clinical course of relapsing-remitting multiple sclerosis (RRMS) is highly heterogeneous and prognostic biomarkers at time of diagnosis are lacking. Objective: We investigated the predictive value of the plasma proteome at time of diagnosis in RRMS patients. Methods: The plasma proteome was interrogated using a novel aptamer-based proteomics platform, which allows to measure the levels of a predefined set of 1310 proteins. Results: In 67 clinically and radiologically well characterized RRMS patients, we found no association between the plasma proteome at diagnosis and clinical, cognitive or MRI outcomes after 11 years. Conclusions: Proteomics studies on cerebrospinal fluid may be better suited to identify prognostic biomarkers in early RRMS.

Tracking disease progression non-invasively in Duchenne and Becker muscular dystrophies.

BACKGROUND: Analysis of muscle biopsies allowed to characterize the pathophysiological changes of Duchenne and Becker muscular dystrophies (D/BMD) leading to the clinical phenotype. Muscle tissue is often investigated during interventional dose finding studies to show in situ proof of concept and pharmacodynamics effect of the tested drug. Less invasive readouts are needed to objectively monitor patients' health status, muscle quality, and response to treatment. The identification of serum biomarkers correlating with clinical function and able to anticipate functional scales is particularly needed for personalized patient management and to support drug development programs. METHODS: A large-scale proteomic approach was used to identify serum biomarkers describing pathophysiological changes (e.g. loss of muscle mass), association with clinical function, prediction of disease milestones, association with in vivo 31 P magnetic resonance spectroscopy data and dystrophin levels in muscles. Cross-sectional comparisons were performed to compare DMD patients, BMD patients, and healthy controls. A group of DMD patients was followed up for a median of 4.4 years to allow monitoring of individual disease trajectories based on yearly visits. RESULTS: Cross-sectional comparison enabled to identify 10 proteins discriminating between healthy controls, DMD and BMD patients. Several proteins (285) were able to separate DMD from healthy, while 121 proteins differentiated between BMD and DMD; only 13 proteins separated BMD and healthy individuals. The concentration of specific proteins in serum was significantly associated with patients' performance (e.g. BMP6 serum levels and elbow flexion) or dystrophin levels (e.g. TIMP2) in BMD patients. Analysis of longitudinal trajectories allowed to identify 427 proteins affected over time indicating loss of muscle mass, replacement of muscle by adipose tissue, and cardiac involvement. Over-representation analysis of longitudinal data allowed to highlight proteins that could be used as pharmacodynamic biomarkers for drugs currently in clinical development. CONCLUSIONS: Serum proteomic analysis allowed to not only discriminate among DMD, BMD, and healthy subjects, but it enabled to detect significant associations with clinical function, dystrophin levels, and disease progression.

Contactin-1 and contactin-2 in cerebrospinal fluid as potential biomarkers for axonal domain dysfunction in multiple sclerosis.

BACKGROUND: Contactin-1 and contactin-2 are important for the maintenance of axonal integrity. OBJECTIVE: To investigate the cerebrospinal fluid levels of contactin-1 and contactin-2 in multiple sclerosis patients and controls, and their potential use as prognostic markers for neurodegeneration. METHODS: Cerebrospinal fluid contactin-1 and contactin-2 were measured in relapsing-remitting multiple sclerosis (n = 41), secondary progressive multiple sclerosis (n = 26) and primary progressive multiple sclerosis patients (n = 13) and controls (n = 18), and in a second cohort with clinically isolated syndrome patients (n = 88, median clinical follow-up period of 2.3 years) and controls (n = 20). Correlations/linear regressions were analysed with other baseline cerebrospinal fluid axonal damage markers and cross-sectional/longitudinal magnetic resonance imaging features. RESULTS: Contactin-1 and contactin-2 levels were up to 1.4-fold reduced in relapsing-remitting multiple sclerosis (contactin-1: p = 0.01, contactin-2: p = 0.02) and secondary progressive multiple sclerosis (contactin-1: p = 0.05, contactin-2: p = 0.02) compared to controls. In clinically isolated syndrome patients, contactin-1 tended to increase when compared to controls (p = 0.07). Both contactin-1 and contactin-2 correlated with neurofilament light, neurofilament heavy and magnetic resonance imaging metrics differently depending on the disease stage. In clinically isolated syndrome patients, baseline contactin-2 level (ß = -0.42, p = 0.04) predicted the longitudinal decline in cortex volume. CONCLUSION: Cerebrospinal fluid contactin-1 and contactin-2 reveal axonal dysfunction in various stages of multiple sclerosis and their inclusion to the biomarker panel may provide better insight into the extent of axonal damage/dysfunction.

Memory Correlates of Alzheimer's Disease Cerebrospinal Fluid Markers: A Longitudinal Cohort Study.

BACKGROUND: Performance on episodic, semantic, and working memory tests is impaired in Alzheimer's disease (AD)-type dementia, but it is unclear which type of memory test is most strongly associated with early AD biomarkers in cerebrospinal fluid (CSF), and most useful for monitoring disease progression. OBJECTIVE: To examine the association between amyloid-ß 1-42 (Aß42) and tau in CSF with performance on different memory domains at baseline, and how these CSF markers are related with memory decline. METHODS: We included 263 individuals with normal cognition, mild cognitive impairment, AD-type dementia, and non-AD dementia from the European EDAR study. Assessment included CSF Aß42 and t-tau analyses with INNO-BIA AlzBio3 Luminex assay, the CERAD wordlist learning and delayed recall, animal fluency test, and the CANTAB Paired Associates Learning (PAL) and Spatial Working Memory tasks. Follow-up assessments were performed within 3 years after baseline. RESULTS: At baseline, decreased CSF Aß42 correlated most strongly with the PAL total errors adjusted and the wordlist delayed recall and increased CSF t-tau with the wordlist delayed recall. Over time, decreased CSF Aß42 was associated with decline on the wordlist learning, whereas increased CSF t-tau were associated with decline in scores on the wordlist learning, wordlist delayed recall, and animal fluency. Associations were independent of baseline diagnosis. CONCLUSION: Tests assessing episodic verbal and visuospatial memory are most useful for detection of AD pathology. Tests for episodic verbal memory and semantic memory are most useful for tracking memory decline.

Relation of Odor Identification with Alzheimer's Disease Markers in Cerebrospinal Fluid and Cognition.

BACKGROUND: Impaired olfactory function is an early characteristic of Alzheimer's disease (AD), but it remains unclear if odor identification also relates to early markers of AD in cerebrospinal fluid (CSF). OBJECTIVE: To investigate the association between odor identification and amyloid-ß 1-42 (Aß42) and total tau (t-tau) concentrations in CSF. In addition, to examine the relation between odor identification and cognitive function at baseline and at follow-up, and whether these associations are moderated by CSF Aß42 and t-tau and apolipoprotein E (APOE) genotype. METHODS: We included 160 individuals (40 with normal cognition, 45 with mild cognitive impairment (MCI), 42 with AD-type dementia, and 26 individuals with non-AD dementia) from the EDAR study. Individuals were recruited from six memory clinics across Europe. Odor identification was tested with the brief University of Pennsylvania Smell Identification Test. CSF Aß42 and t-tau were assessed with INNO-BIA AlzBio3 Luminex assay. Neuropsychological assessment included tests for verbal memory, verbal fluency, attention, executive function, and visuoconstruction. Follow-up was performed within 3 years after baseline. RESULTS: Lower odor identification scores correlated with increased CSF t-tau concentrations and with lower scores on all cognitive measures at baseline independent of diagnostic group. Lower odor identification scores predicted decline on the MMSE in the total group, and decline on wordlist learning and delayed recall in APOE ɛ4 carriers and in individuals with abnormal Aß42. CONCLUSION: Odor identification impairment may be an indicator of neuronal injury rather than amyloid pathology.

Detection of contactin-2 in cerebrospinal fluid (CSF) of patients with Alzheimer's disease using Fluorescence Correlation Spectroscopy (FCS).

OBJECTIVES: Alzheimer's disease (AD) is the most common cause of dementia in the world. As many AD biomarkers occur at rather low abundances in CSF or blood, techniques of very high sensitivity and accuracy are important as diagnostic tools in the clinic. Here, we aimed to provide proof of concept of the use of a single molecule detection technique, Fluorescence Correlation Spectroscopy (FCS) for detection of novel candidate biomarkers for AD. DESIGN AND METHODS: FCS detects the diffusion times of the antigen-antibody complexes in highly diluted sample solutions, thus eliminating the need of large sample volumes and allows estimating the concentration of the target antigen. We developed a FCS set-up for contactin-2, a neuronal cell adhesion molecule and a ligand of beta-secretase 1 (BACE1) and amyloid precursor protein (APP), the latter proteins being important players in AD. With this method, we investigated whether contactin-2 concentrations are changed after delayed storage and in patients with Alzheimer's disease. RESULTS: The FCS set-up for measuring contactin-2 in CSF had a lower limit of quantification (LLOQ) of 0.2ng/ml and intra- and inter-assay coefficients of variation (CVs) of 12.2% and 14.6% respectively. Contactin-2 levels were stable up to one week storage of CSF (n=3) at RT and 4°C. Further, contactin-2 levels were similar in probable AD patients (n=34, p=0.27) compared to patients with subjective cognitive decline (SCD) (n=11). CONCLUSIONS: FCS is a sensitive tool, which can be used for detecting biomarkers in the clinical setting using very low sample volumes (10µl) and can measure proteins in their native conformations in the body fluid.

Multicenter Analytical Validation of Aß40 Immunoassays.

BACKGROUND: Before implementation in clinical practice, biomarker assays need to be thoroughly analytically validated. There is currently a strong interest in implementation of the ratio of amyloid-ß peptide 1-42 and 1-40 (Aß42/Aß40) in clinical routine. Therefore, in this study, we compared the analytical performance of six assays detecting Aß40 in cerebrospinal fluid (CSF) in six laboratories according to a recently standard operating procedure (SOP) developed for implementation of ELISA assays for clinical routine. METHODS: Aß40 assays of six vendors were validated in up to three centers per assay according to recently proposed international consensus validation protocols. The performance parameters included sensitivity, precision, dilutional linearity, recovery, and parallelism. Inter-laboratory variation was determined using a set of 20 CSF samples. In addition, test results were used to critically evaluate the SOPs that were used to validate the assays. RESULTS: Most performance parameters of the different Aß40 assays were similar between labs and within the predefined acceptance criteria. The only exceptions were the out-of-range results of recovery for the majority of experiments and of parallelism by three laboratories. Additionally, experiments to define the dilutional linearity and hook-effect were not executed correctly in part of the centers. The inter-laboratory variation showed acceptable low levels for all assays. Absolute concentrations measured by the assays varied by a factor up to 4.7 for the extremes. CONCLUSION: All validated Aß40 assays appeared to be of good technical quality and performed generally well according to predefined criteria. A novel version of the validation SOP is developed based on these findings, to further facilitate implementation of novel immunoassays in clinical practice.

Glutaminyl cyclase activity correlates with levels of Aß peptides and mediators of angiogenesis in cerebrospinal fluid of Alzheimer's disease patients.

BACKGROUND: Pyroglutamylation of truncated Aß peptides, which is catalysed by enzyme glutaminyl cyclase (QC), generates pE-Aß species with enhanced aggregation propensities and resistance to most amino-peptidases and endo-peptidases. pE-Aß species have been identified as major constituents of Aß plaques and reduction of pE-Aß species is associated with improvement of cognitive tasks in animal models of Alzheimer's disease (AD). Pharmacological inhibition of QC has thus emerged as a promising therapeutic approach for AD. Here, we question whether cerebrospinal fluid (CSF) QC enzymatic activity differs between AD patients and controls and whether inflammatory or angiogenesis mediators, some of which are potential QC substrates, and/or Aß peptides may serve as pharmacodynamic read-outs for QC inhibition. METHODS: QC activity, Aß peptides and inflammatory or angiogenesis mediators were measured in CSF of a clinically well-characterized cohort of 20 mild AD patients, 20 moderate AD patients and 20 subjective memory complaints (SMC) controls. Correlation of these parameters with core diagnostic CSF AD biomarkers (Aß42, tau and p-tau) and clinical features was evaluated. RESULTS: QC activity shows a tendency to decrease with AD progression (p = 0.129). The addition of QC activity to biomarkers tau and p-tau significantly increases diagnostic power (ROC-AUCTAU = 0.878, ROC-AUCTAU&QC = 0.939 and ROC-AUCpTAU = 0.820, ROC-AUCpTAU&QC = 0.948). In AD and controls, QC activity correlates with Aß38 (r = 0.83, p < 0.0001) and Aß40 (r = 0.84, p < 0.0001), angiogenesis mediators (Flt1, Tie2, VEGFD, VCAM-1 and ICAM-1, r > 0.5, p < 0.0001) and core diagnostic biomarkers (r > 0.35, p = <0.0057). QC activity does not correlate with MMSE or ApoE genotype. CONCLUSIONS: Aß38, Aß40 and angiogenesis mediators (Flt1, Tie2, VEGFD, VCAM-1 and ICAM-1) are potential pharmacodynamic markers of QC inhibition, because their levels closely correlate with QC activity in AD patients. The addition of QC activity to core diagnostic CSF biomarkers may be of specific interest in clinical cases with discordant imaging and biochemical biomarker results.