The impact of pre-analytical variables on the stability of neurofilament proteins in CSF, determined by a novel validated SinglePlex Luminex assay and ELISA

Diagnostic value of neurofilaments in differentiating motor neuron disease from multifocal motor neuropathy

OBJECTIVE

To evaluate the performance of serum neurofilament light chain (NfL) and cerebrospinal fluid (CSF) phosphorylated neurofilament heavy chain (pNfH) as diagnostic biomarkers for the differentiation between motor neuron disease (MND) and multifocal motor neuropathy (MMN).

METHODS

This retrospective, monocentric study included 16 patients with MMN and 34 incident patients with MND. A subgroup of lower motor neuron (MN) dominant MND patients (n = 24) was analyzed separately. Serum NfL was measured using Ella automated immunoassay, and CSF pNfH was measured using enzyme-linked immunosorbent assay. Area under the curve (AUC), optimal cutoff values (Youden's index), and correlations with demographic characteristics were calculated.

RESULTS

Neurofilament concentrations were significantly higher in MND compared to MMN (p < 0.001), and serum NfL and CSF pNfH correlated strongly with each other (Spearman's rho 0.68, p < 0.001). Serum NfL (AUC 0.946, sensitivity and specificity 94%) and CSF pNfH (AUC 0.937, sensitivity 90.0%, specificity 100%) performed excellent in differentiating MND from MMN. Optimal cutoff values were ≥ 44.15 pg/mL (serum NfL) and ≥ 715.5 pg/mL (CSF pNfH), respectively. Similar results were found when restricting the MND cohort to lower MN dominant patients. Only one MMN patient had serum NfL above the cutoff. Two MND patients presented with neurofilament concentrations below the cutoffs, both featuring a slowly progressive disease.

CONCLUSION

Neurofilaments are valuable supportive biomarkers for the differentiation between MND and MMN. Serum NfL and CSF pNfH perform similarly well and elevated neurofilaments in case of diagnostic uncertainty underpin MND diagnosis.

Plasma and cerebrospinal fluid concentrations of neurofilament light protein correlate in patients with idiopathic normal pressure hydrocephalus

BACKGROUND

Neurofilament light chain protein (NFL), a marker of neuronal axonal degeneration, is increased in cerebrospinal fluid (CSF) of patients with idiopathic normal pressure hydrocephalus (iNPH). Assays for analysis of NFL in plasma are now widely available but plasma NFL has not been reported in iNPH patients. Our aim was to examine plasma NFL in iNPH patients and to evaluate the correlation between plasma and CSF levels, and whether NFL levels are associated with clinical symptoms and outcome after shunt surgery.

METHODS

Fifty iNPH patients with median age 73 who had their symptoms assessed with the iNPH scale and plasma and CSF NFL sampled pre- and median 9 months post-operatively. CSF plasma was compared with 50 healthy controls (HC) matched for age and gender. Concentrations of NFL were determined in plasma using an in-house Simoa method and in CSF using a commercially available ELISA method.

RESULTS

Plasma NFL was elevated in patients with iNPH compared to HC (iNPH: 45 (30-64) pg/mL; HC: 33 (26-50) (median; Q1-Q3), p = 0.029). Plasma and CSF NFL concentrations correlated in iNPH patients both pre- and postoperatively (r = 0.67 and 0.72, p < 0.001). We found only weak correlations between plasma or CSF NFL and clinical symptoms and no associations with outcome. A postoperative NFL increase was seen in CSF but not in plasma.

CONCLUSIONS

Plasma NFL is increased in iNPH patients and concentrations correlate with CSF NFL implying that plasma NFL can be used to assess evidence of axonal degeneration in iNPH. This finding opens a window for plasma samples to be used in future studies of other biomarkers in iNPH. NFL is probably not a very useful marker of symptomatology or for prediction of outcome in iNPH.

Pre-analytical long-term stability of neopterin and neurofilament light in stored cerebrospinal fluid samples

OBJECTIVES

The aim of this study was to evaluate the impact of long-term sample storage on the concentrations of neopterin and neurofilament light (Nfl) in cerebrospinal fluid (CSF) samples. These are useful markers of neuroinflammation and neuronal damage and have been applied as biomarkers for several neurological diseases. However, different pre-analytical variables have potential to influence results.

METHODS

Twenty-one CSF samples donated by patients with HTLV-1-associated myelopathy (HAM) and stored for up to 11 years at -80 °C were retested after three-years for neopterin (n=10) and Nfl (n=11) by ELISA.

RESULTS

There was a strong correlation between the paired results (r>0.98, p<0.0001). Neopterin concentrations (nmol/L) ranged from 12.4 to 64 initially and from 11.5 to 64.4 when retested, with means (SD) of 30 (18.4) 1st test and 33 (19.1) 2nd test. Nfl concentrations (pg/mL) ranged from 79.9 to 3,733 initially and from 86.3 to 3,332, when retested with means (SD) of 1,138 (1,272) 1st test and 1,009 (1,114) at re-test.

CONCLUSIONS

Storing CSF samples at -80 °C appears not to impact the quantification of neopterin and Nfl allowing confidence in the reporting of archived samples.

Review and standard operating procedures for collection of biospecimens and analysis of biomarkers in new onset refractory status epilepticus

New onset refractory status epilepticus (NORSE), including its subtype with a preceding febrile illness known as febrile infection-related epilepsy syndrome (FIRES), is one of the most severe forms of status epilepticus. The exact causes of NORSE are currently unknown, and there is so far no disease-specific therapy. Identifying the underlying pathophysiology and discovering specific biomarkers, whether immunologic, infectious, genetic, or other, may help physicians in the management of patients with NORSE. A broad spectrum of biomarkers has been proposed for status epilepticus patients, some of which were evaluated for patients with NORSE. Nonetheless, none has been validated, due to significant variabilities in study cohorts, collected biospecimens, applied analytical methods, and defined outcome endpoints, and to small sample sizes. The NORSE Institute established an open NORSE/FIRES biorepository for health-related data and biological samples allowing the collection of biospecimens worldwide, promoting multicenter research and sharing of data and specimens. Here, we suggest standard operating procedures for biospecimen collection and biobanking in this rare condition. We also propose criteria for the appropriate use of previously collected biospecimens. We predict that the widespread use of standardized procedures will reduce heterogeneity, facilitate the future identification of validated biomarkers for NORSE, and provide a better understanding of the pathophysiology and best clinical management for these patients.

Molecular biomarkers and cognitive impairment in multiple sclerosis: State of the field, limitations, and future direction - A systematic review and meta-analysis

OBJECTIVE

Multiple sclerosis (MS) is associated with cognitive impairment (CI) such as slowed information processing speed (IPS). Currently, no immunocellular or molecular markers have been established in cerebrospinal fluid and serum analysis as surrogate biomarkers with diagnostic or predictive value for the development of CI. This systematic review and meta-analysis aims to sum up the evidence regarding currently discussed markers for CI in MS.

METHODS

A literature search was conducted on molecular biomarkers of CI in MS, such as neurofilament light chain, chitinases, and vitamin D.

RESULTS

5543 publications were screened, of which 77 entered the systematic review. 13 studies were included in the meta-analysis. Neurofilament light chain (CSF: r_p = -0.294, p = 0.003; serum: r_p = -0.137, p = 0.001) and serum levels of vitamin D (r_p = 0.190, p = 0.014) were associated with IPS outcomes.

CONCLUSIONS

Neurofilament light chain and vitamin D are promising biomarkers to track impairments in IPS in MS. Further longitudinal research is needed to establish the use of molecular biomarkers to monitor cognitive decline.

Differences between blood and cerebrospinal fluid glial fibrillary Acidic protein levels: The effect of sample stability

INTRODUCTION

Recent evidence has shown that the marker of reactive astrogliosis, glial fibrillary acidic protein (GFAP), has a stronger relationship with cerebral amyloid beta (Aβ) pathology in blood than in cerebrospinal fluid (CSF). This study investigates if pre-analytical treatment of blood and CSF contribute to these unexpected findings.

METHODS

Paired CSF and serum samples from 49 individuals (Aβ-negative = 28; Aβ-positive = 21) underwent a series of seven freeze-thaw cycles (FTCs). All samples were analyzed for GFAP and neurofilament light (NfL) using single molecule array technology including a fresh unfrozen sample from each patient.

RESULTS

FTC significantly affected CSF GFAP concentration (-188.12 pg/ml per FTC) but not serum GFAP. In the same samples, NfL remained stable. Serum GFAP had a higher discrimination of Aβ burden than CSF GFAP, irrespective of FTC, which also included unfrozen samples.

DISCUSSION

This study demonstrates large stability differences of GFAP in CSF and serum. However, this disparity does not seem to fully explain the stronger association of serum GFAP with Aβ pathology. Further work should investigate mechanisms of GFAP release into the bloodstream under pathological conditions.

The Feasibility of Early Alzheimer’s Disease Diagnosis Using a Neural Network Hybrid Platform

Early diagnosis of Alzheimer’s Disease (AD) is critical for disease prevention and cure. However, currently, techniques with the required high sensitivity and specificity are lacking. Recently, with the advances and increased accessibility of data analysis tools, such as machine learning, research efforts have increasingly focused on using these computational methods to solve this challenge. Here, we demonstrate a convolutional neural network (CNN)-based AD diagnosis approach using the surface-enhanced Raman spectroscopy (SERS) fingerprints of human cerebrospinal fluid (CSF). SERS and CNN were combined for biomarker detection to analyze disease-associated biochemical changes in the CSF. We achieved very high reproducibility in double-blind experiments for testing the feasibility of our system on human samples. We achieved an overall accuracy of 92% (100% for normal individuals and 88.9% for AD individuals) based on the clinical diagnosis. Further, we observed an excellent correlation coefficient between our test score and the Clinical Dementia Rating (CDR) score. Our findings offer a substantial indication of the feasibility of detecting AD biomarkers using the innovative combination of SERS and machine learning. We are hoping that this will serve as an incentive for future research in the field.

Serum Phosphorylated Neurofilament Heavy subunit levels and its association with the Risk for Catastrophic Injury in Thoroughbred Racehorses

Neurofilaments are structural proteins that are concentrated in the body and axons of neurons. Damage to the neurons or axons as a result of trauma or infectious diseases leads to the release of neurofilaments into blood and cerebrospinal fluid (CSF). This case-control study was carried out to compare serum levels of phosphorylated neurofilament heavy chain (pNF-H) between clinically healthy Thoroughbred (TB) horses and TB horses that suffered catastrophic musculoskeletal injuries (cMSI), and to investigate the correlation between putative risk factors and serum concentrations of pNF-H in injured horses. Blood samples were collected from clinically healthy horses and from horses that suffered cMSI. The concentration of pNF-H in serum samples was determined using the Phosphorylated Neurofilament H Sandwich enzyme-linked immunosorbent assay kit. A total of 343 horses were enrolled in the study (148 cases and 195 controls). The median serum concentration of pNF-H for controls was 0.0 ng/ml and for cases was 0.07 ng/ml. No significant difference was observed between the two groups in racing. The number of lifetime starts was correlated with serum pNF-H concentration in case horses. The serum concentration of pNF-H was higher in case horses that experienced cMSI while training than while racing. The number of lifetime starts is a proxy measure for several risk factors related to cumulative exercise load during the career of racehorses. Measurement of serum concentrations of pNF-H in TB racehorses does not support the hypothesis that subclinical neurologic injury or conditions are associated with catastrophic injury of TB racehorses.

Phosphorylated Neurofilament Heavy Chain: A Potential Diagnostic Biomarker in Amyotrophic Lateral Sclerosis

Neuroaxonal damage is a feature of various neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Phosphorylated neurofilament heavy chain (pNfH) is a cytoskeletal structural protein released as a result of axonal damage into the CSF, and subsequently into the blood. Due to high specificity for neuronal cell damage, pNfH is advantageous over other biomarkers, for ALS disease identification. Here, we review the structure and function of neurofilaments and their role in detection of various neurodegenerative conditions. Additionally, a retrospective meta-analysis was performed to depict the significance of pNfH as a valuable diagnostic and prognostic biomarker in ALS.

Neurofilaments can differentiate ALS subgroups and ALS from common diagnostic mimics

Delayed diagnosis and misdiagnosis are frequent in people with amyotrophic lateral sclerosis (ALS), the most common form of motor neuron disease (MND). Neurofilament light chain (NFL) and phosphorylated neurofilament heavy chain (pNFH) are elevated in ALS patients. We retrospectively quantified cerebrospinal fluid (CSF) NFL, CSF pNFH and plasma NFL in stored samples that were collected at the diagnostic work-up of ALS patients (n = 234), ALS mimics (n = 44) and controls (n = 9). We assessed the diagnostic performance, prognostication value and relationship to the site of onset and genotype. CSF NFL, CSF pNFH and plasma NFL levels were significantly increased in ALS patients compared to patients with neuropathies & myelopathies, patients with myopathies and controls. Furthermore, CSF pNFH and plasma NFL levels were significantly higher in ALS patients than in patients with other MNDs. Bulbar onset ALS patients had significantly higher plasma NFL levels than spinal onset ALS patients. ALS patients with C9orf72HRE mutations had significantly higher plasma NFL levels than patients with SOD1 mutations. Survival was negatively correlated with all three biomarkers. Receiver operating characteristics showed the highest area under the curve for CSF pNFH for differentiating ALS from ALS mimics and for plasma NFL for estimating ALS short and long survival. All three biomarkers have diagnostic value in differentiating ALS from clinically relevant ALS mimics. Plasma NFL levels can be used to differentiate between clinical and genetic ALS subgroups.

Neurofilament Proteins as Biomarkers to Monitor Neurological Diseases and the Efficacy of Therapies

Biomarkers of neurodegeneration and neuronal injury have the potential to improve diagnostic accuracy, disease monitoring, prognosis, and measure treatment efficacy. Neurofilament proteins (NfPs) are well suited as biomarkers in these contexts because they are major neuron-specific components that maintain structural integrity and are sensitive to neurodegeneration and neuronal injury across a wide range of neurologic diseases. Low levels of NfPs are constantly released from neurons into the extracellular space and ultimately reach the cerebrospinal fluid (CSF) and blood under physiological conditions throughout normal brain development, maturation, and aging. NfP levels in CSF and blood rise above normal in response to neuronal injury and neurodegeneration independently of cause. NfPs in CSF measured by lumbar puncture are about 40-fold more concentrated than in blood in healthy individuals. New ultra-sensitive methods now allow minimally invasive measurement of these low levels of NfPs in serum or plasma to track disease onset and progression in neurological disorders or nervous system injury and assess responses to therapeutic interventions. Any of the five Nf subunits - neurofilament light chain (NfL), neurofilament medium chain (NfM), neurofilament heavy chain (NfH), alpha-internexin (INA) and peripherin (PRPH) may be altered in a given neuropathological condition. In familial and sporadic Alzheimer's disease (AD), plasma NfL levels may rise as early as 22 years before clinical onset in familial AD and 10 years before sporadic AD. The major determinants of elevated levels of NfPs and degradation fragments in CSF and blood are the magnitude of damaged or degenerating axons of fiber tracks, the affected axon caliber sizes and the rate of release of NfP and fragments at different stages of a given neurological disease or condition directly or indirectly affecting central nervous system (CNS) and/or peripheral nervous system (PNS). NfPs are rapidly emerging as transformative blood biomarkers in neurology providing novel insights into a wide range of neurological diseases and advancing clinical trials. Here we summarize the current understanding of intracellular NfP physiology, pathophysiology and extracellular kinetics of NfPs in biofluids and review the value and limitations of NfPs and degradation fragments as biomarkers of neurodegeneration and neuronal injury.

Neurofilament light chain and glial fibrillary acidic protein levels in metachromatic leukodystrophy

Metachromatic leukodystrophy is a lethal metabolic leukodystrophy, with emerging treatments for early disease stages. Biomarkers to measure disease activity are required for clinical assessment and treatment follow-up.

This retrospective study compared neurofilament light chain and glial fibrillary acidic protein (GFAP) levels in CSF (n = 11) and blood (n = 92) samples of 40 patients with metachromatic leukodystrophy (aged 0–42 years) with 38 neurologically healthy children (aged 0–17 years) and 38 healthy adults (aged 18–45 years), and analysed the associations between these levels with clinical phenotype and disease evolution in untreated and transplanted patients. Metachromatic leukodystrophy subtype was determined based on the (expected) age of symptom onset. Disease activity was assessed by measuring gross motor function deterioration and brain MRI. Longitudinal analyses with measurements up to 23 years after diagnosis were performed using linear mixed models.

CSF and blood neurofilament light chain and GFAP levels in paediatric controls were negatively associated with age (all P < 0.001). Blood neurofilament light chain level at diagnosis (median, interquartile range; picograms per millilitre) was significantly increased in both presymptomatic (14.7, 10.6–56.7) and symptomatic patients (136, 40.8–445) compared to controls (5.6, 4.5–7.1), and highest among patients with late-infantile (456, 201–854) or early-juvenile metachromatic leukodystrophy (291.0, 104–445) and those ineligible for treatment based on best practice (291, 57.4–472). GFAP level (median, interquartile range; picogram per millilitre) was only increased in symptomatic patients (591, 224–1150) compared to controls (119, 78.2–338) and not significantly associated with treatment eligibility (P = 0.093). Higher blood neurofilament light chain and GFAP levels at diagnosis were associated with rapid disease progression in late-infantile (P = 0.006 and P = 0.051, respectively) and early-juvenile patients (P = 0.048 and P = 0.039, respectively). Finally, blood neurofilament light chain and GFAP levels decreased during follow-up in untreated and transplanted patients but remained elevated compared with controls. Only neurofilament light chain levels were associated with MRI deterioration (P < 0.001).

This study indicates that both proteins may be considered as non-invasive biomarkers for clinical phenotype and disease stage at clinical assessment, and that neurofilament light chain might enable neurologists to make better informed treatment decisions. In addition, neurofilament light chain holds promise assessing treatment response. Importantly, both biomarkers require paediatric reference values, given that their levels first decrease before increasing with advancing age.

Increased GFAP concentrations in the cerebrospinal fluid of patients with unipolar depression

Inflammatory processes involving altered microglial activity may play a relevant role in the pathophysiology of depressive disorders. Glial fibrillary acidic protein (GFAP) and calcium-binding protein S100B are considered microglial markers. To date, their role has been studied in the serum and tissue material of patients with unipolar depression but not in the cerebrospinal fluid (CSF). Therefore, the aim of the current study was to examine GFAP and S100B levels in the CSF of patients with major depression to better understand their role in affective disorders. In this retrospective study, 102 patients with unipolar depression and 39 mentally healthy controls with idiopathic intracranial hypertension were investigated. GFAP and S100B levels were measured using commercially available ELISA kits. CSF routine parameters were collected during routine clinical care. The mean values of GFAP and S100B were compared using age (and sex) corrected ANOVAs. Matched subgroups were analyzed by using an independent sample t-test. In addition, correlation analyses between GFAP/S100B levels and CSF routine parameters were performed within the patient group. Patients with unipolar depression had significantly higher levels of GFAP than controls (733.22 pg/ml vs. 245.56 pg/ml, p < 0.001). These results remained significant in a sub-analysis in which all controls were compared with patients suffering from depression matched 1:1 by age and sex (632.26 pg/ml vs. 245.56 pg/ml, p < 0.001). Levels of S100B did not differ significantly between patients and controls (1.06 ng/ml vs. 1.17 ng/ml, p = 0.385). GFAP levels correlated positively with albumin quotients (p < 0.050), S100B levels correlated positively with white blood cell counts (p = 0.001), total protein concentrations (p < 0.001), and albumin quotients (p = 0.001) in the CSF. The significance of the study is limited by its retrospective and open design, methodological aspects, and the control group with idiopathic intracranial hypertension. In conclusion, higher GFAP levels in patients with depression may be indicative of altered microglia activity, especially in astrocytes, in patients with unipolar depression. In addition, correlation analyses support the idea that S100B levels could be related to the integrity of the blood-brain/CSF barrier. Further multimodal and longitudinal studies are necessary to validate these findings and clarify the underlying biological processes.

Transcriptional profiling and circRNA-miRNA-mRNA network analysis identify the biomarkers in Sheng-ji Hua-yu formula treated diabetic wound healing

ETHNOPHARMACOLOGICAL RELEVANCE

Sheng-ji Hua-yu (SJHY) formula is a traditional Chinese herbal which is effective in treating diabetic ulcers. It has been indicated to accelerate re-epithelialization and healing time of cutaneous wounds in a Streptozotocin (STZ)-induced diabetic mouse model. However, its mechanisms remain undetermined.

AIM OF THE STUDY

To reveal the molecular mechanisms of SJHY formula in treating diabetic wounds through transcriptional profiling and circRNA-miRNA-mRNA network analysis clues.

MATERIALS AND METHODS

Protein expressions of tumor necrosis factor (TNF-α), interleukin (IL)-6, IL-1β in skin tissues of wounds from SJHY formula-treated and untreated mice were analyzed by Bio-Plex assay. Differentially expressed (DE) genes were detected by whole transcriptome sequencing (RNA-seq). Using predicted miRNA targets, circRNA-miRNA-mRNA networks were constructed. Furthermore, quantitative real-time PCR (qRT-PCR) was utilized to validate the circRNA-miRNA-mRNA networks.

RESULTS

Bio-Plex assay illustrated that the protein expressions of TNF-α, IL-1β, IL-6 were downregulated in SJHY formula-treated diabetic wounds compared with untreated wounds. RNA-seq identified 11 DE circRNAs and 476 DE mRNAs between SJHY formula-treated and diabetic mice, including 4 upregulated and 7 downregulated circRNAs, 311 upregulated and 165 downregulated mRNAs. CircRNA-Krt13/miR-665-3p/Itga3 and circRNA-Krt14/miR-706/Mylk4 pathways were built, which may contribute to the healing of SJHY formula-treated diabetic wounds.

CONCLUSIONS

Overall, this study suggests that these 2 circRNA-miRNA-mRNA networks are potential biomarkers for evaluation of SJHY formula efficacy in diabetic wound healing, which provides evidence to support its clinical applications.

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 (sβ) = 0.28, p = 0.034), T2 lesion volume (sβ = 0.23, p = 0.041), and tended to associate with black hole count (sβ = 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.

Neurofilament Proteins as Prognostic Biomarkers in Neurological Disorders

Neurofilaments: light, medium, and heavy (abbreviated as NF-L, NF-M, and NF-H, respectively), which belong to Type IV intermediate filament family (IF), are neuron-specific cytoskeletal components. Neurofilaments are axonal structural components and integral components of synapses, which are important for neuronal electric signal transmissions along the axons and post-translational modification. Abnormal assembly of neurofilaments is found in several human neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), infantile spinal muscular atrophy (SMA), and hereditary sensory-motor neuropathy (HSMN). In addition, those pathological neurofilament accumulations are known in α-synuclein in Parkinson's disease (PD), Aβ and tau in Alzheimer's disease (AD), polyglutamine in CAG trinucleotide repeat disorders, superoxide dismutase 1 (SOD1), TAR DNA-binding protein 43 (TDP43), neuronal FUS proteins, optineurin (OPTN), ubiquilin 2 (UBQLN2), and dipeptide repeat protein (DRP) in amyotrophic lateral sclerosis (ALS). When axon damage occurs in central nervous disorders, neurofilament proteins are released and delivered into cerebrospinal fluid (CSF), which are then circulated into blood. New quantitative analyses and assay techniques are well-developed for the detection of neurofilament proteins, particularly NF-L and the phosphorylated NF-H (pNF-H) in CSF and serum. This review discusses the potential of using peripheral blood NF quantities and evaluating the severity of damage in the nervous system. Intermediate filaments could be promising biomarkers for evaluating disease progression in different nervous system disorders.

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.

Location matters: highly divergent protein levels in samples from different CNS compartments in a clinical trial of rituximab for progressive MS

Background

The relationship between proteins in different CNS extracellular compartments is unknown. In this study the levels of selected proteins in three compartments in people with progressive multiple sclerosis (PMS) were compared.

Methods

During an open label, phase 1b study on intraventricular administration of rituximab for PMS, samples were collected from the interstitial space (ISS) of the brain through microdialysis. Samples were also obtained from ventricular and lumbar cerebrospinal fluid (CSF). These samples were analyzed with a multiplexed proximity extension assay, measuring the levels of 180 proteins split equally between two panels, detecting proteins associated with immunology and neurology, respectively.

Results

Considerable differences in concentrations were observed between the three analyzed compartments. Compared to ventricular CSF, ISS fluid contained statistically significant higher levels of 25 proteins (84% immunology panel and 16% neurology panel). Ventricular CSF contained significantly higher levels of 54 proteins (31% immunology panel and 69% neurology panel) compared to ISS fluid, and 17 proteins (76% immunology panel and 24% neurology panel) compared to lumbar CSF. Lumbar CSF showed significantly higher levels of 115 proteins (32% immunology panel and 68% neurology panel) compared to ventricular CSF. The three compartments displayed poor correlation with a median Spearman’s rho of -0.1 (IQR 0.4) between ISS and ventricular CSF and 0.3 (IQR 0.4) between ventricular and lumbar CSF.

Conclusion

A substantial heterogeneity in the protein levels of samples obtained from different CNS compartments was seen. Therefore, data obtained from analysis of lumbar CSF should be interpreted with caution when making conclusions about pathophysiological processes in brain tissue.

Blood and cerebrospinal fluid neurofilament light differentially detect neurodegeneration in early Alzheimer's disease

Cerebrospinal fluid (CSF) neurofilament light (NfL) concentration has reproducibly been shown to reflect neurodegeneration in brain disorders, including Alzheimer's disease (AD). NfL concentration in blood correlates with the corresponding CSF levels, but few studies have directly compared the reliability of these 2 markers in sporadic AD. Herein, we measured plasma and CSF concentrations of NfL in 478 cognitively unimpaired (CU) subjects, 227 patients with mild cognitive impairment, and 113 patients with AD dementia. We found that the concentration of NfL in CSF, but not in plasma, was increased in response to Aβ pathology in CU subjects. Both CSF and plasma NfL concentrations were increased in patients with mild cognitive impairment and AD dementia. Furthermore, only NfL in CSF was associated with reduced white matter microstructure in CU subjects. Finally, in a transgenic mouse model of AD, CSF NfL increased before serum NfL in response to the development of Aβ pathology. In conclusion, NfL in CSF may be a more reliable biomarker of neurodegeneration than NfL in blood in preclinical sporadic AD.

Revisiting the Cerebrospinal Fluid Biomarker Profile in Idiopathic Normal Pressure Hydrocephalus: The Bologna Pro-Hydro Study

Cerebrospinal fluid (CSF) biomarkers have been extensively investigated in idiopathic normal pressure hydrocephalus (iNPH) with the aim of a better differential diagnosis, but the pathophysiological mechanisms underlying CSF biomarker changes and the relationship between biomarker levels and clinical variables are still a matter of debate. We evaluated CSF amyloid-β (Aβ)42 and Aβ40, total (t)-tau, phosphorylated (p)-tau, total prion protein (t-PrP), and neurofilament light chain protein (NfL) in healthy controls (n = 50) and subjects with iNPH (n = 71), Alzheimer's disease (AD) (n = 60), and several other subtypes of dementia (n = 145). Patients with iNPH showed significantly lower levels of Aβ42, Aβ40, t-tau, and p-tau compared to controls. Similarly, t-PrP values showed a trend toward lower levels in iNPH patients than in controls. At variance, NfL levels were increased in iNPH as in all other neurodegenerative dementias, with no significant difference between "pure" iNPH cases and those with vascular or AD comorbidities. The Aβ42/Aβ40 ratio showed higher diagnostic value than Aβ42 alone in the differential diagnosis between iNPH and AD. There were no clinically relevant associations between neuroimaging markers, scores at clinical and cognitive scales/tests, or rates of response at tap test and CSF biomarker results. In summary, the CSF biomarker signature in patients with iNPH is mainly characterized by reduced CSF concentrations of Aβ- and tau-related proteins. The assessment of CSF neurodegenerative biomarker profile in iNPH, including the Aβ42/Aβ40 ratio, contributes to the differential diagnosis with AD and other dementias but shows poor associations with clinical variables.

An update on blood-based biomarkers for non-Alzheimer neurodegenerative disorders

Cerebrospinal fluid analyses and neuroimaging can identify the underlying pathophysiology at the earliest stage of some neurodegenerative disorders, but do not have the scalability needed for population screening. Therefore, a blood-based marker for such pathophysiology would have greater utility in a primary care setting and in eligibility screening for clinical trials. Rapid advances in ultra-sensitive assays have enabled the levels of pathological proteins to be measured in blood samples, but research has been predominantly focused on Alzheimer disease (AD). Nonetheless, proteins that were identified as potential blood-based biomarkers for AD, for example, amyloid-β, tau, phosphorylated tau and neurofilament light chain, are likely to be relevant to other neurodegenerative disorders that involve similar pathological processes and could also be useful for the differential diagnosis of clinical symptoms. This Review outlines the neuropathological, clinical, molecular imaging and cerebrospinal fluid features of the most common neurodegenerative disorders outside the AD continuum and gives an overview of the current status of blood-based biomarkers for these disorders.

Cerebrospinal fluid cytokines and chemokines in children with Lyme neuroborreliosis; pattern and diagnostic utility

BACKGROUND

Lyme neuroborreliosis (LNB) is characterized by cerebrospinal fluid (CSF) inflammation with several cytokines/chemokines and B-lymphocytes. Clinically, LNB in children may be difficult to discriminate from non-Lyme aseptic meningitis (NLAM). We aimed to identify CSF cytokine/chemokine patterns in children with LNB, NLAM and controls and elucidate the diagnostic value of these cytokines/chemokines alone or in combination to discriminate between LNB and NLAM.

METHODS

Children with symptoms suggestive of LNB were included prospectively and categorized as LNB, NLAM or controls (no pleocytosis). Cytokines/chemokines in CSF were measured by multiplex bead assays and levels were compared between the three groups by nonparametric statistical tests. Previous results from the same children on the established biomarker, CXCL13, were included in the statistical analyses. The diagnostic properties of cytokines/chemokines to discriminate between LNB and NLAM were determined by receiver operating characteristic curve analyses with estimates of area under curve (AUC). To explore diagnostic properties of combinations of cytokines/chemokines, prediction models based on logistic regression were used.

RESULTS

We included 195 children with LNB (n = 77), NLAM (n = 12) and controls (n = 106). Children with LNB had higher CSF levels of CCL19, CCL22 and CXCL13 compared to NLAM and controls, whereas INFγ was higher in NLAM than in LNB and controls. CXCL13 was the superior single cytokine/chemokine to discriminate LNB from NLAM (AUC 0.978). The combination CXCL13/CCL19 (AUC 0.992) may possibly improve the specificity for LNB, especially for children with moderate CXCL13 levels.

CONCLUSIONS

The intrathecal immune reaction in LNB is characterized by B cell associated chemokines. Whether the combination CXCL13/CCL19 further improves discrimination between LNB and NLAM beyond the diagnostic improvements by CXCL13 alone needs to be tested in new studies.

Molecular biomarkers in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory-neurodegenerative disease of the central nervous system presenting with significant inter- and intraindividual heterogeneity. However, the application of clinical and imaging biomarkers is currently not able to allow individual characterization and prediction. Complementary, molecular biomarkers which are easily quantifiable come from the areas of immunology and neurobiology due to the causal pathomechanisms and can excellently complement other disease characteristics. Only a few molecular biomarkers have so far been routinely used in clinical practice as their validation and transfer take a long time. This review describes the characteristics that an ideal MS biomarker should have and the challenges of establishing new biomarkers. In addition, clinically relevant and promising biomarkers from the blood and cerebrospinal fluid are presented which are useful for MS diagnosis and prognosis as well as for the assessment of therapy response and side effects.

Cerebrospinal Fluid Biomarkers in Patients with Frontotemporal Dementia Spectrum: A Single-Center Study

Cerebrospinal fluid (CSF) neurofilament light chain protein (NfL) and Alzheimer's disease (AD) core biomarker levels have been evaluated in cohorts of patients with frontotemporal dementia spectrum (FTD), but the distribution of values across the different clinical syndromes and underlying proteinopathies, and the relative diagnostic accuracy appear discordant among studies. We measured CSF NfL, total (t)-tau, phosphorylated (p)-tau, and amyloid-β (Aβ)42 in healthy controls (n = 38) and subjects with a clinical, genetic, CSF biomarker-based, and/or neuropathological diagnosis of FTD (n = 141) or AD (n = 60). Sub-analyses were conducted in a proportion of subjects with definite and/or probable frontotemporal lobar degeneration with tau (FTLD-TAU) (n = 42) or TDP43 pathology (FTLD-TDP) (n = 36). Both FTD and AD groups showed significantly increased CSF NfL levels in comparison to controls (p < 0.001). CSF NfL levels were significantly higher in FTD patients than in AD (p < 0.001), reaching the highest values in amyotrophic lateral sclerosis associated with FTD. Patients with probable and definite FTLD-TDP had significantly higher NfL levels (p < 0.001) and lower p-tau/t-tau values (p < 0.001) in comparison with probable and definite FTLD-TAU cases. NfL showed good diagnostic accuracy in the distinction between FTD and controls (AUC 0.862±0.027) and yielded an accuracy (AUC 0.861±0.045) comparable to that of the p-tau/t-tau ratio (AUC 0.814±0.050), with 80.0% sensitivity and 81.0% specificity, in the discrimination between probable/definite FTLD-TAU and FTLD-TDP. Our data further validate CSF NfL as a surrogate biomarker of neurodegeneration and disease severity in patients with FTD spectrum. Moreover, they demonstrate a good diagnostic value for NfL and p-tau/t-tau ratio in the discrimination between FTLD-TAU and FTLD-TDP.

Clinical value of cerebrospinal fluid neurofilament light chain in semantic dementia

BACKGROUND

Semantic dementia (SD) is a neurodegenerative disorder characterised by progressive language problems falling within the clinicopathological spectrum of frontotemporal lobar degeneration (FTLD). The development of disease-modifying agents may be facilitated by the relative clinical and pathological homogeneity of SD, but we need robust monitoring biomarkers to measure their efficacy. In different FTLD subtypes, neurofilament light chain (NfL) is a promising marker, therefore we investigated the utility of cerebrospinal fluid (CSF) NfL in SD.

METHODS

This large retrospective multicentre study compared cross-sectional CSF NfL levels of 162 patients with SD with 65 controls. CSF NfL levels of patients were correlated with clinical parameters (including survival), neuropsychological test scores and regional grey matter atrophy (including longitudinal data in a subset).

RESULTS

CSF NfL levels were significantly higher in patients with SD (median: 2326 pg/mL, IQR: 1628-3593) than in controls (577 (446-766), p<0.001). Higher CSF NfL levels were moderately associated with naming impairment as measured by the Boston Naming Test (rs =-0.32, p=0.002) and with smaller grey matter volume of the parahippocampal gyri (rs =-0.31, p=0.004). However, cross-sectional CSF NfL levels were not associated with progression of grey matter atrophy and did not predict survival.

CONCLUSION

CSF NfL is a promising biomarker in the diagnostic process of SD, although it has limited cross-sectional monitoring or prognostic abilities.

Correlations between serum and CSF pNfH levels in ALS, FTD and controls: a comparison of three analytical approaches

Background

Phosphorylated neurofilament heavy (pNfH), a neuronal cytoskeleton protein, might provide a promising blood biomarker of neuronal damage in neurodegenerative diseases (NDDs). The best analytical approaches to measure pNfH levels and whether serum levels correlate with cerebrospinal fluid (CSF) levels in NDDs remain to be determined.

Methods

We here compared analytical sensitivity and reliability of three novel analytical approaches (homebrew Simoa, commercial Simoa and ELISA) for quantifying pNfH in both CSF and serum in samples of amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD) and control subjects.

Results

While all three assays showed highly correlated CSF measurements, Simoa assays also yielded high between-assay correlations for serum measurements (ϱ = 0.95). Serum levels also correlated strongly with CSF levels for Simoa-based measurements (both ϱ = 0.62). All three assays allowed distinguishing ALS from controls by increased CSF pNfH levels, and Simoa assays also by increased serum pNfH levels. pNfH levels were also increased in FTD.

Conclusions

pNfH concentrations in CSF and, if measured by Simoa assays, in blood might provide a sensitive and reliable biomarker of neuronal damage, with good between-assay correlations. Serum pNfH levels measured by Simoa assays closely reflect CSF levels, rendering serum pNfH an easily accessible blood biomarker of neuronal damage in NDDs.

Diagnostic and Prognostic Performance of Neurofilaments in ALS

There is a need for biomarkers for amyotrophic lateral sclerosis (ALS), to support the diagnosis of the disease, to predict disease progression and to track disease activity and treatment responses. Over the last decade multiple studies have investigated the potential of neurofilament levels, both in cerebrospinal fluid and blood, as biomarker for ALS. The most widely studied neurofilament subunits are neurofilament light chain (NfL) and phosphorylated neurofilament heavy chain (pNfH). Neurofilament levels are reflecting neuronal injury and therefore potentially of value in ALS and other neurological disorders. In this mini-review, we summarize and discuss the available evidence about neurofilaments as diagnostic and prognostic biomarker for human ALS.

Guidelines for CSF Processing and Biobanking: Impact on the Identification and Development of Optimal CSF Protein Biomarkers

The field of neurological diseases strongly needs biomarkers for early diagnosis and optimal stratification of patients in clinical trials or to monitor disease progression. Cerebrospinal fluid (CSF) is one of the main sources for the identification of novel protein biomarkers for neurological diseases. Despite the enormous efforts employed to identify novel CSF biomarkers, the high variability observed across different studies has hampered their validation and implementation in clinical practice. Such variability is partly caused by the effect of different pre-analytical confounding factors on protein stability, highlighting the importance to develop and comply with standardized operating procedures. In this chapter, we describe the international consensus pre-analytical guidelines for CSF processing and biobanking that have been established during the last decade, with a special focus on the influence of pre-analytical confounders on the global CSF proteome. In addition, we provide novel results on the influence of different delayed storage and freeze/thaw conditions on the CSF proteome using two novel large multiplex protein arrays (SOMAscan and Olink). Compliance to consensus guidelines will likely facilitate the successful development and implementation of CSF protein biomarkers in both research and clinical settings, ultimately facilitating the successful development of disease-modifying therapies.

Tear Luminex Analysis in Dry Eye Patients

Background

The purpose of this study was to analyze tear inflammatory cytokines of different subclasses of dry eye disease (DED) patients using Luminex technology.

Material/Methods

Forty-five DED patients including 20 Sjogren syndrome aqueous tear deficiency (SS-ATD) patients, 20 non-Sjogren syndrome aqueous tear deficiency (NSS-ATD) patients, 15 meibomian gland dysfunction (MGD) patients, and 15 normal participants were enrolled in this study. Concentrations of 11 inflammatory cytokines in tear samples of study participants were measured by Luminex assay; ELISA assay was further applied for validation.

Results

The levels of cytokines were mostly increased (TNF-α, IL-1α, IL-1β, IL-6, IL-8, IL-12P70, IL-13, IFN-γ, and MIP-1α) in DED patients compared with normal participants. And the levels of TNF-α, IL-6, IL-8, and IL-12P70 were significantly elevated in tears of the patient groups compared to tears of participants in the normal group (P<0.05). Statistical differences were also observed among the patient groups (SS-ATD, NSS-ATD, and MGD) for the level of IL-8 and TNF-α. The results of ELISA assay demonstrated the consistence with Luminex assay, confirming the practicality of Luminex technology for the analysis of multiple cytokines in DED patient tears.

Conclusions

The levels of inflammatory cytokines were mostly elevated in DED patients, and statistical differences of some cytokines were also found between SS-ATD, NSS-ATD, and MGD groups, suggesting that inflammatory cytokines could be potential supplements for the diagnosis of DED subclasses and therapeutic targets for DED patients.

Stability of blood-based biomarkers of Alzheimer's disease over multiple freeze-thaw cycles

Introduction

Freeze-thaw instability may contribute to preanalytical variation in blood-based biomarker studies. We investigated the effects of up to four freeze-thaw cycles on single molecule array immunoassays of serum neurofilament light chain and plasma total tau, amyloid β 1–40 (Aß₄₀), and Aβ 1–42 (Aβ₄₂).

Methods

Individuals who had peripheral venepuncture during investigation of suspected neurodegenerative disease were recruited. After standardized preprocessing, 200 μL of plasma and serum aliquots were stored at −80°C within 60 minutes. Aliquots underwent one to four freeze-thaw cycles.

Results

There was no significant difference across four freeze-thaw cycles for serum neurofilament light chain (n = 12), plasma total tau (n = 11), or plasma Aβ₄₂ (n = 12). For plasma Aβ₄₀ (n = 14), there were significant median reductions by ratios of .96 and .92 at the third and fourth cycles, respectively.

Discussion

Up to four freeze-thaw cycles do not influence single molecule array blood biomarkers of neurofilament light chain, total tau, or Aβ₄₂, with at most minor reductions in Aβ₄₀.

Serum neurofilament light chain in progressive supranuclear palsy

INTRODUCTION

Neurofilament light chain (NfL) is a promising biomarker in neurodegenerative diseases. Elevated NfL levels in CSF and blood have been observed in a growing number of neurodegenerative disorders, including frontotemporal dementia and Alzheimer's disease. We studied serum NfL levels in patients with progressive supranuclear palsy (PSP) in relation to disease severity and survival.

METHODS

Serum NfL levels were determined cross-sectionally in a retrospective cohort of 131 patients with PSP and 95 healthy controls. Detailed clinical examination was performed and disease severity was assessed by several rating scales.

RESULTS

We found that serum NfL levels in PSP were twice as high as those in controls, and that NfL levels correlated with worse functional, motor and cognitive functioning. During follow-up, 119 PSP patients had died, and higher NfL levels were associated with a shorter survival.

CONCLUSION

This study provides evidence that serum NfL is a relevant and promising biomarker in PSP for disease severity, and may be used as a prognostic tool to predict survival in clinical practice.

Blood-based cerebral biomarkers in preeclampsia: Plasma concentrations of NfL, tau, S100B and NSE during pregnancy in women who later develop preeclampsia - A nested case control study

Objective

To evaluate if concentrations of the neuronal proteins neurofilament light chain and tau are changed in women developing preeclampsia and to evaluate the ability of a combination of neurofilament light chain, tau, S100B and neuron specific enolase in identifying neurologic impairment before diagnosis of preeclampsia.

Methods

A nested case-control study within a longitudinal study cohort was performed. 469 healthy pregnant women were enrolled between 2004–2007 and plasma samples were collected at gestational weeks 10, 25, 28, 33 and 37. Plasma concentrations of tau and neurofilament light chain were analyzed in 16 women who eventually developed preeclampsia and 36 controls throughout pregnancy with single molecule array (Simoa) method and compared within and between groups. S100B and NSE had been analyzed previously in the same study population. A statistical model with receiving characteristic operation curve was constructed with the four biomarkers combined.

Results

Plasma concentrations of neurofilament light chain were significantly increased in women who developed preeclampsia in gestational week 33 (11.85 ng/L, IQR 7.48–39.93 vs 6.80 ng/L, IQR 5.65–11.40) and 37 (22.15 ng/L, IQR 10.93–35.30 vs 8.40 ng/L, IQR 6.40–14.30) and for tau in gestational week 37 (4.33 ng/L, IQR 3.97–12.83 vs 3.77 ng/L, IQR 1.91–5.25) in contrast to healthy controls. A combined model for preeclampsia with tau, neurofilament light chain, S100B and neuron specific enolase in gestational week 25 displayed an area under the curve of 0.77, in week 28 it was 0.75, in week 33 it was 0.89 and in week 37 it was 0.83. Median week for diagnosis of preeclampsia was at 38 weeks of gestation.

Conclusion

Concentrations of both tau and neurofilament light chain are increased in the end of pregnancy in women developing preeclampsia in contrast to healthy pregnancies. Cerebral biomarkers might reflect cerebral involvement before onset of disease.

The CSF neurofilament light signature in rapidly progressive neurodegenerative dementias

Background

Neurofilament light chain protein (NfL) is a surrogate biomarker of neurodegeneration that has never been systematically tested, either alone or in combination with other biomarkers, in atypical/rapidly progressive neurodegenerative dementias (NDs).

Methods

Using validated, commercially available enzyme-linked immunosorbent assay kits, we measured cerebrospinal fluid (CSF) NfL, total tau (t-tau), phosphorylated tau, and β-amyloid 42 in subjects with a neuropathological or clinical diagnosis of prion disease (n = 141), Alzheimer’s disease (AD) (n = 73), dementia with Lewy bodies (DLB) (n = 35), or frontotemporal lobar degeneration (FTLD) (n = 44). Several cases with an atypical/rapidly progressive course were included in each group. We evaluated the diagnostic accuracy of every CSF biomarker and their combinations by ROC curve analyses.

Results

In each patient group CSF NfL showed higher levels than in control subjects, reaching the highest values in those with Creutzfeldt-Jakob disease (CJD). In the latter, NfL showed a divergent, subtype-specific correlation with t-tau, depending on the degree of subcortical involvement and disease duration. Most significantly, patients with classic sporadic CJD (sCJD) MM1 showed a significantly lower concentration of CSF NfL than those with sCJD MV2, despite the much higher t-tau levels and the more rapid clinical course. High NfL levels were also detected in most atypical CJD cases, showing a disease duration longer than 2 years and/or borderline/negative results in other CSF assays (e.g., 14-3-3, t-tau, and prion real-time quaking-induced conversion). Rapidly progressive/atypical cases showed higher NfL levels than typical patients in FTLD, but not in AD or DLB. NfL showed accuracy similar to that of t-tau in discriminating CJD from other NDs, but it had higher efficacy in differentiating atypical forms, especially in regard to Alzheimer’s disease.

Conclusions

The present data indicate that CSF NfL and t-tau levels reflect distinct pathophysiological mechanisms of neurodegeneration and support the clinical use of NfL as a fast screening biomarker for the differential diagnosis of atypical/rapidly progressive NDs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-017-0331-1) contains supplementary material, which is available to authorized users.

Cerebrospinal Fluid B-lymphocyte Chemoattractant CXCL13 in the Diagnosis of Acute Lyme Neuroborreliosis in Children

BACKGROUND

Current markers of Lyme neuroborreliosis (LNB) in children have insufficient sensitivity in the early stage of disease. The B-lymphocyte chemoattractant CXCL13 in the cerebrospinal fluid (CSF) may be useful in diagnosing LNB, but its specificity has not been evaluated in studies including children with clinically relevant differential diagnoses. The aim of this study was to elucidate the diagnostic value of CSF CXCL13 in children with symptoms suggestive of LNB.

METHODS

Children with symptoms suggestive of LNB were included prospectively into predefined groups with a high or low likelihood of LNB based on CSF pleocytosis and the detection of Borrelia antibodies or other causative agents. CSF CXCL13 levels were compared between the groups, and receiver-operating characteristic analyses were performed to indicate optimal cutoff levels to discriminate LNB from non-LNB conditions.

RESULTS

Two hundred and ten children were included. Children with confirmed LNB (n=59) and probable LNB (n=18) had higher CSF CXCL13 levels than children with possible LNB (n=7), possible peripheral LNB (n=7), non-Lyme aseptic meningitis (n=12), non-meningitis (n=91) and negative controls (n=16). Using 18 pg/mL as a cutoff level, both the sensitivity and specificity of CSF CXCL13 for LNB (confirmed and probable) were 97%. Comparing only children with LNB and non-Lyme aseptic meningitis, the sensitivity and specificity with the same cutoff level were 97% and 83%, respectively.

CONCLUSION

CSF CXCL13 is a sensitive marker of LNB in children. The specificity to discriminate LNB from non-Lyme aseptic meningitis may be more moderate, suggesting that CSF CXCL13 should be used together with other variables in diagnosing LNB in children.

The role of blood and CSF biomarkers in the evaluation of new treatments against multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is an immune-mediated chronic neurodegenerative disease of the central nervous system (CNS). Therapeutic interventions with immunomodulatory agents reduce disease activity and disability development, which are monitored clinically and by magnetic resonance imaging (MRI). However, these measures largely lack information on the impact from these therapies on inflammation, demyelination and axonal injury, the essential pathophysiological features of MS. Several biomarkers for inflammation and neurodegeneration have been detected in cerebrospinal fluid (CSF). In MS, some of these biomarkers seem to reflect disease activity, disability progression, and therapeutic response. Areas covered: In this review, we describe the most promising CSF biomarkers of inflammation and degeneration for monitoring therapeutic interventions in MS. We also describe the evolution of highly sensitive immunoassays that enable determination of neuron-specific biomarkers in blood. Expert commentary: Together with clinical and MRI measures, CSF biomarkers may improve the assessment of therapeutic efficacy and make personalized treatment possible. One disadvantage has been the need of repetitive lumbar punctures to obtain CSF. However, the technical development of highly sensitive immunoassays allows determination of extremely low quantities of neuron-specific proteins in blood. This will potentially open a new era for monitoring disease activity and treatment response in MS.

Cerebrospinal fluid biomarker examination as a tool to discriminate behavioral variant frontotemporal dementia from primary psychiatric disorders

INTRODUCTION

To prospectively determine the diagnostic value of cerebrospinal fluid (CSF) levels total-tau (tau) to amyloid-β_1-42 ratio (Aβ_1-42) ratio (tau/Aβ_1-42 ratio), phosphorylated-tau (p-tau) to tau ratio (p-tau/tau ratio), neurofilament light chain (NfL) and YKL40 in the late-onset frontal lobe syndrome, in particular for the differential diagnosis of behavioral variant frontotemporal dementia (bvFTD) versus primary psychiatric disorders (PSY).

METHOD

We included patients with a multidisciplinary 2-year-follow-up diagnosis of probable/definite bvFTD (n = 22) or PSY (n = 25), who underwent a detailed neuropsychiatric clinical examination, neuropsychological test battery, and magnetic resonance imaging at baseline. In all cases, CSF was collected through lumbar puncture at baseline. We compared CSF biomarker levels between the two groups and measured the diagnostic accuracy for probable/definite bvFTD, using the follow-up diagnosis as the reference standard.

RESULTS

The best discriminators between probable/definite bvFTD and PSY were the levels of CSF NfL (area under the curve [AUC] 0.93, P < .001, 95% confidence interval [CI] 0.85-1.00), p-tau/tau ratio (AUC 0.87, P < .001, 95% CI 0.77-0.97), and YKL40 (AUC 0.82, P = .001, 95% CI 0.68-0.97). The combination of these three biomarkers had a sensitivity of 91% (95% CI 66%-100%) at a specificity of 83% (95% CI 65%-95%) with an AUC of 0.94 (P < .001, 95% CI 0.87-1.00) for bvFTD. CSF tau/Aβ_1-42 ratio was less accurate in differentiating between bvFTD and PSY.

DISCUSSION

We found a good diagnostic accuracy for higher levels of CSF NfL and YKL40 and reduced p-tau/tau ratio in distinguishing bvFTD from PSY. We advocate the use of these CSF biomarkers as potential additional tools to neuroimaging in the diagnosis of bvFTD versus PSY.

Neurofilaments in CSF As Diagnostic Biomarkers in Motor Neuron Disease: A Meta-Analysis

Objective: Neurofilaments in CSF are promising biomarkers which might help in the diagnosis of motor neuron disease (MND). We aim to assess the diagnostic value of neurofilaments in CSF for MND.

Methods: Pubmed, Emabase, and Web of Science were searched for relevant studies systematically. Articles in English that evaluated the utility of neurofilaments in CSF in the diagnosis of MND were included. Data were extracted by two independent investigators. Diagnostic indexes for neurofilament light chain (NFL) and phosphorylated neurofilament heavy chain (pNFH) were calculated separately. Stata 12.0 software with a bivariate mixed-effects model was used to summarize the diagnostic indexes from eligible studies.

Results: Five studies on NFL and eight studies on pNFH met inclusion criteria. For NFL, the pooled sensitivity and specificity were 81% (95% confidence interval [CI], 72–88%) and 85% (95% CI, 76–91%), respectively; the positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 5.5 (95% CI, 3.1–9.8) and 0.22 (95% CI, 0.14–0.35), respectively; the summary diagnostic odds ratio (DOR) was 25 (95% CI, 9–70), and the area under summary receiver operator characteristic curve (AUC) was 0.90 (95% CI, 0.87–0.92). For pNFH, the pooled sensitivity, specificity, PLR and NLR were 85% (95% CI, 80–88%), 85% (95% CI, 77–90%), 5.5 (95% CI, 3.6–8.4), and 0.18 (95% CI, 0.13–0.25), respectively; the DOR was 30 (95% CI, 16–58), and the AUC was 0.91 (95% CI, 0.88–0.93).

Conclusion: Neurofilaments in CSF have a high value in the diagnosis of MND, though the optimal cutoff value remains to be further investigated.

Multicenter immunoassay validation of cerebrospinal fluid neurofilament light: a biomarker for neurodegeneration

AIM

Neurofilament light (NfL) chain, a putative cerebrospinal fluid biomarker, can support neurodegenerative disease diagnosis and indicate disease severity and prognosis. Universal validation protocols when used to measure biomarkers can reduce pre and analytical laboratory variation, thus increasing end-user confidence in the consistency of validation data across sites.

METHODOLOGY

Here, a commercially available NfL ELISA (UmanDiagnostics, Umeå, Sweden) was validated in a multicentered setting using comprehensive newly developed standard operating procedures.

RESULTS

The data showed good assay sensitivity and intra and interassay precision. Interlaboratory precision was, however, suboptimal.

CONCLUSION

The UmanDiagnostics assay is suitable for the quantification of NfL in human cerebrospinal fluid. However, sources of interlaboratory variation in the data require further investigation.

Neurofilament light chain: a biomarker for genetic frontotemporal dementia

Objective

To evaluate cerebrospinal fluid (CSF) and serum neurofilament light chain (NfL) levels in genetic frontotemporal dementia (FTD) as a potential biomarker in the presymptomatic stage and during the conversion into the symptomatic stage. Additionally, to correlate NfL levels to clinical and neuroimaging parameters.

Methods

In this multicenter case–control study, we investigated CSF NfL in 174 subjects (48 controls, 40 presymptomatic carriers and 86 patients with microtubule‐associated protein tau (MAPT), progranulin (GRN), and chromosome 9 open reading frame 72 (C9orf72) mutations), and serum NfL in 118 subjects (39 controls, 44 presymptomatic carriers, 35 patients). In 55 subjects both CSF and serum was determined. In two subjects CSF was available before and after symptom onset (converters). Additionally, NfL levels were correlated with clinical parameters, survival, and regional brain atrophy.

Results

CSF NfL levels in patients (median 6762 pg/mL, interquartile range 3186–9309 pg/mL) were strongly elevated compared with presymptomatic carriers (804 pg/mL, 627–1173 pg/mL, P < 0.001), resulting in a good diagnostic performance to discriminate both groups. Serum NfL correlated highly with CSF NfL (r_s= 0.87, P < 0.001) and was similarly elevated in patients. Longitudinal samples in the converters showed a three‐ to fourfold increase in CSF NfL after disease onset. Additionally, NfL levels in patients correlated with disease severity, brain atrophy, annualized brain atrophy rate and survival.

Interpretation

NfL in both serum and CSF has the potential to serve as a biomarker for clinical disease onset and has a prognostic value in genetic FTD.

Neurometabolite Alterations Associated With Cognitive Performance in Perinatally HIV-Infected Children

Despite treatment with combination antiretroviral therapy (cART), cognitive impairment is still observed in perinatally HIV-infected children. We aimed to evaluate potential underlying cerebral injury by comparing neurometabolite levels between perinatally HIV-infected children and healthy controls. This cross-sectional study evaluated neurometabolites, as measured by Magnetic Resonance Spectroscopy (MRS), in perinatally HIV-infected children stable on cART (n = 26) and healthy controls (n = 36).Participants were included from a cohort of perinatally HIV-infected children and healthy controls, matched group-wise for age, gender, ethnicity, and socio-economic status. N-acetylaspartate (NAA), glutamate (Glu), myo-inositol (mI), and choline (Cho) levels were studied as ratios over creatine (Cre). Group differences and associations with HIV-related parameters, cognitive functioning, and neuronal damage markers (neurofilament and total Tau proteins) were determined using age-adjusted linear regression analyses.HIV-infected children had increased Cho:Cre in white matter (HIV-infected = 0.29 ± 0.03; controls = 0.27 ± 0.03; P value = 0.045). Lower nadir CD4+ T-cell Z-scores were associated with reduced neuronal integrity markers NAA:Cre and Glu:Cre. A Centers for Disease Control and Prevention (CDC) stage C diagnosis was associated with higher glial markers Cho:Cre and mI:Cre. Poorer cognitive performance was mainly associated with higher Cho:Cre in HIV-infected children, and with lower NAA:Cre and Glu:Cre in healthy controls. There were no associations between neurometabolites and neuronal damage markers in blood or CSF.Compared to controls, perinatally HIV-infected children had increased Cho:Cre in white matter, suggestive of ongoing glial proliferation. Levels of several neurometabolites were associated with cognitive performance, suggesting that MRS may be a useful method to assess cerebral changes potentially linked to cognitive outcomes.

Developing Biomarkers for MS

Existing clinical outcomes of disease activity, including relapse rates, are inherently insensitive to the underlying pathological process in MS. Moreover, it is extremely difficult to measure clinical disability in patients, which is often a retrospective assessment, and definitely not within the time frame of a clinical trial. Biomarkers , conversely are more specific for a pathologic process and if used correctly can prove invaluable in the diagnosis, stratification and monitoring of disease activity, including any subclinical activity which is not visible to the naked eye. In this chapter, we discuss the development of neurofilaments as surrogate outcomes of disability in MS. The validation and qualification are vital steps in biomarker development and to gaining acceptance in scientific community, and the pitfalls leading up to this are also discussed.

Discriminative and prognostic potential of cerebrospinal fluid phosphoTau/tau ratio and neurofilaments for frontotemporal dementia subtypes

INTRODUCTION

A decreased cerebrospinal fluid (CSF) p-Tau181 to total tau ratio (p/t-tau) is a biomarker for frontotemporal lobar degeneration with TDP43 inclusions (FTLD-TDP) and for amyotrophic lateral sclerosis (ALS). CSF light chain neurofilaments (NfL) are increased in ALS. We examined whether CSF p/t-tau and NfL are related to ALS status in FTLD-TDP.

METHODS

We compared CSF p/t-tau and NfL levels between patients with FTLD-TDP with ALS (n = 15), FTLD-TDP without ALS (n = 17), FTLD-Tau (n = 6), Alzheimer's disease (AD; n = 25), and subjective memory complaints (SMC, n = 24).

RESULTS

Apart from FTLD-Tau, all groups differed significantly with increasing p/t-tau ratios from FTLD-TDP with ALS to FTLD-TDP without ALS to AD and SMC. CSF NfL was very high in FTLD-TDP with ALS followed by FTLD-TDP without ALS, AD, and SMC. Both biomarkers correlated with survival.

DISCUSSION

CSF p/t-tau ratio and NfL levels are strongly driven by ALS status. These markers, therefore, appear to be more of prognostic than diagnostic significance.

Facilitating the Validation of Novel Protein Biomarkers for Dementia: An Optimal Workflow for the Development of Sandwich Immunoassays

Different neurodegenerative disorders, such as Alzheimer’s disease (AD) and frontotemporal dementia (FTD), lead to dementia syndromes. Dementia will pose a huge impact on society and thus it is essential to develop novel tools that are able to detect the earliest, most sensitive, discriminative, and dynamic biomarkers for each of the disorders. To date, the most common assays used in large-scale protein biomarker analysis are enzyme-linked immunosorbent assays (ELISA), such as the sandwich immunoassays, which are sensitive, practical, and easily implemented. However, due to the novelty of many candidate biomarkers identified during proteomics screening, such assays or the antibodies that specifically recognize the desired marker are often not available. The development and optimization of a new ELISA should be carried out with considerable caution since a poor planning can be costly, ineffective, time consuming, and it may lead to a misinterpretation of the findings. Previous guidelines described either the overall biomarker development in more general terms (i.e., the process from biomarker discovery to validation) or the specific steps of performing an ELISA procedure. However, a workflow describing and guiding the main issues in the development of a novel ELISA is missing. Here, we describe a specific and detailed workflow to develop and validate new ELISA for a successful and reliable validation of novel dementia biomarkers. The proposed workflow highlights the main issues in the development of an ELISA and covers several critical aspects, including production, screening, and selection of specific antibodies until optimal fine-tuning of the assay. Although these recommendations are designed to analyze novel biomarkers for dementia in cerebrospinal fluid, they are generally applicable for the development of immunoassays for biomarkers in other human body fluids or tissues. This workflow is designed to maximize the quality of the developed ELISA using a time- and cost-efficient strategy. This will facilitate the validation of the dementia biomarker candidates ultimately allowing accurate diagnostic conclusions.

Validation of a quantitative cerebrospinal fluid alpha-synuclein assay in a European-wide interlaboratory study

Decreased levels of alpha-synuclein (aSyn) in cerebrospinal fluid (CSF) in Parkinson's disease and related synucleinopathies have been reported, however, not consistently in all cross-sectional studies. To test the performance of one recently released human-specific enzyme-linked immunosorbent assay (ELISA) for the quantification of aSyn in CSF, we carried out a round robin trial with 18 participating laboratories trained in CSF ELISA analyses within the BIOMARKAPD project in the EU Joint Program - Neurodegenerative Disease Research. CSF samples (homogeneous aliquots from pools) and ELISA kits (one lot) were provided centrally and data reported back to one laboratory for data analysis. Our study showed that although factors such as preanalytical sample handling and lot-to-lot variability were minimized by our study design, we identified high variation in absolute values of CSF aSyn even when the same samples and same lots of assays were applied. We further demonstrate that although absolute concentrations differ between laboratories the quantitative results are comparable. With further standardization this assay may become an attractive tool for comparing aSyn measurements in diverse settings. Recommendations for further validation experiments and improvement of the interlaboratory results obtained are given.

Biobanking of Cerebrospinal Fluid for Biomarker Analysis in Neurological Diseases

Cerebrospinal fluid (CSF) reflects pathophysiological aspects of neurological diseases, where neuroprotective strategies and biomarkers are urgently needed. Therefore, biobanking is very relevant for biomarker discovery and evaluation for these neurological diseases.An important aspect of CSF biobanking is quality control, needed for e.g. consistent patient follow-up and the exchange of patient samples between research centers. Systematic studies to address effects of pre-analytical and storage variation on a broad range of CSF proteins are needed and initiated.Important features of CSF biobanking are intensive collaboration in international networks and the tight application of standardized protocols. The current adoption of standardized protocols for CSF and blood collection and for biobanking of these samples, as presented in this chapter, enables biomarker studies in large cohorts of patients and controls.In conclusion, biomarker research in neurodegenerative diseases has entered a new era due to the collaborative and multicenter efforts of many groups. The streamlining of biobanking procedures, including sample collection, quality control, and the selection of optimal control groups for investigating biomarkers is an important improvement to perform high quality biomarker studies.

Biomarkers of therapeutic response in multiple sclerosis: current status

Multiple sclerosis (MS) is an autoimmune disease of unknown cause, in which chronic inflammation drives multifocal demyelination of axons in both white and gray matter in the CNS. The pathological course of the disease is heterogeneous and involves an early, predominantly inflammatory demyelinating disease phase of relapsing-remitting MS (RRMS), which, over a variable period of time, evolves into a progressively degenerative stage associated with axonal loss and scar formation, causing physical and cognitive disability. For patients with RRMS, there is a growing arsenal of disease-modifying agents (DMAs), with varying degrees of efficacy, as defined by reduced relapse rates, improved magnetic resonance imaging outcomes, and preservation of neurological function. Establishment of personalized treatment plans remains one of the biggest challenges in therapeutic decision-making in MS because the disease prognosis and individual therapeutic outcomes are extremely difficult to predict. Current research is aimed at discovery and validation of biomarkers that reliably measure disease progression and effective therapeutic intervention. Individual biomarker candidates with evident clinical utility are highlighted in this review and include neutralizing autoantibodies against DMAs, fetuin-A, osteopontin, isoprostanes, chemokine (C-X-C motif) ligand 13 (CXCL13), neurofilament light and heavy, and chitinase 3-like protein. In addition, application of more advanced screening technologies has opened up new categories of biomarkers that move beyond detection of individual soluble proteins, including gene expression and autoantibody arrays, microRNAs, and circulating microvesicles/exosomes. Development of clinically useful biomarkers in MS will not only shape the practice of personalized medicine but will also serve as surrogate markers to enable investigation of innovative treatments within clinical trials that are less costly, are of shorter duration, and have more certainty of outcomes.