Validation of electrochemiluminescence assays for highly sensitive and reproducible quantification of α-synuclein in cerebrospinal fluid

Comparison of biospecimens for α-synuclein seed amplification assays in Parkinson's disease: A systematic review and network meta-analysis

BACKGROUND AND PURPOSE

Alpha-synuclein seed amplification assays (α-syn SAAs) are promising diagnostic methods for Parkinson's disease (PD) and other synucleinopathies. However, there is limited consensus regarding the diagnostic and differential diagnostic performance of α-syn SAAs on biofluids and peripheral tissues.

METHODS

A comprehensive research was performed in PubMed, Web of Science, Embase and Cochrane Library. Meta-analysis was performed using a random-effects model. A network meta-analysis based on an ANOVA model was conducted to compare the relative accuracy of α-syn SAAs with different specimens.

RESULTS

The pooled sensitivity and specificity of α-syn SAAs in distinguishing PD from healthy controls or non-neurodegenerative neurological controls were 0.91 (95% confidence interval [CI] 0.89-0.92) and 0.95 (95% CI 0.94-0.96) for cerebrospinal fluid (CSF); 0.91 (95% CI 0.86-0.94) and 0.92 (95% CI 0.87-0.95) for skin; 0.80 (95% CI 0.66-0.89) and 0.87 (95% CI 0.69-0.96) for submandibular gland; 0.44 (95% CI 0.30-0.59) and 0.92 (95% CI 0.79-0.98) for gastrointestinal tract; 0.79 (95% CI 0.70-0.86) and 0.88 (95% CI 0.77-0.95) for saliva; and 0.51 (95% CI 0.39-0.62) and 0.91 (95% CI 0.84-0.96) for olfactory mucosa (OM). The pooled sensitivity and specificity were 0.91 (95% CI 0.89-0.93) and 0.50 (95% CI 0.44-0.55) for CSF, 0.92 (95% CI 0.83-0.97) and 0.22 (95% CI 0.06-0.48) for skin, and 0.55 (95% CI 0.42-0.68) and 0.50 (95% CI 0.35-0.65) for OM in distinguishing PD from multiple system atrophy. The pooled sensitivity and specificity were 0.92 (95% CI 0.89-0.94) and 0.84 (95% CI 0.73-0.91) for CSF, 0.92 (95% CI 0.83-0.97) and 0.88 (95% CI 0.64-0.99) for skin and 0.63 (95% CI 0.52-0.73) and 0.86 (95% CI 0.64-0.97) for OM in distinguishing PD from progressive supranuclear palsy. The pooled sensitivity and specificity were 0.94 (95% CI 0.90-0.97) and 0.95 (95% CI 0.77-1.00) for CSF and 0.94 (95% CI 0.84-0.99) and 0.86 (95% CI 0.42-1.00) for skin in distinguishing PD from corticobasal degeneration.

CONCLUSIONS

α-Synuclein SAAs of CSF, skin, saliva, submandibular gland, gastrointestinal tract and OM are promising diagnostic assays for PD, with CSF and skin α-syn SAAs demonstrating higher diagnostic performance.

A Phase Ib Trial of AVID200, a TGFβ 1/3 Trap, in Patients with Myelofibrosis

PURPOSE

Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by systemic symptoms, cytopenias, organomegaly, and bone marrow fibrosis. JAK2 inhibitors afford symptom and spleen burden reduction but do not alter the disease course and frequently lead to thrombocytopenia. TGFβ, a pleiotropic cytokine elaborated by the MF clone, negatively regulates normal hematopoiesis, downregulates antitumor immunity, and promotes bone marrow fibrosis. Our group previously showed that AVID200, a potent and selective TGFβ 1/3 trap, reduced TGFβ1-induced proliferation of human mesenchymal stromal cells, phosphorylation of SMAD2, and collagen expression. Moreover, treatment of MF mononuclear cells with AVID200 led to increased numbers of progenitor cells (PC) with wild-type JAK2 rather than JAK2V617F.

PATIENTS AND METHODS

We conducted an investigator-initiated, multicenter, phase Ib trial of AVID200 monotherapy in 21 patients with advanced MF.

RESULTS

No dose-limiting toxicity was identified at the three dose levels tested, and grade 3/4 anemia and thrombocytopenia occurred in 28.6% and 19.0% of treated patients, respectively. After six cycles of therapy, two patients attained a clinical benefit by IWG-MRT criteria. Spleen and symptom benefits were observed across treatment cycles. Unlike other MF-directed therapies, increases in platelet counts were noted in 81% of treated patients with three patients achieving normalization. Treatment with AVID200 resulted in potent suppression of plasma TGFβ1 levels and pSMAD2 in MF cells.

CONCLUSIONS

AVID200 is a well-tolerated, rational, therapeutic agent for the treatment of patients with MF and should be evaluated further in patients with thrombocytopenic MF in combination with agents that target aberrant MF intracellular signaling pathways.

Alpha-Synuclein species in oral mucosa as potential biomarkers for multiple system atrophy

Background

The definitive diagnosis of Multiple system atrophy (MSA) requires the evidence of abnormal deposition of α-Synuclein (α-Syn) through brain pathology which is unable to achieve in vivo. Deposition of α-Syn is not limited to the central nervous system (CNS), but also extended to peripheral tissues. Detection of pathological α-Syn deposition in extracerebral tissues also contributes to the diagnosis of MSA. We recently reported the increased expressions of α-Syn, phosphorylated α-Synuclein at Ser129 (pS129), and α-Syn aggregates in oral mucosal cells of Parkinson’s disease (PD), which serve as potential biomarkers for PD. To date, little is known about the α-Syn expression pattern in oral mucosa of MSA which is also a synucleinopathy. Here, we intend to investigate whether abnormal α-Syn deposition occurs in oral mucosal cells of MSA, and to determine whether α-Syn, pS129, and α-Syn aggregates in oral mucosa are potential biomarkers for MSA.

Methods

The oral mucosal cells were collected by using cytobrush from 42 MSA patients (23 MSA-P and 19 MSA-C) and 47 age-matched healthy controls (HCs). Immunofluorescence analysis was used to investigate the presence of α-Syn, pS129, and α-Syn aggregates in the oral mucosal cells. Then, the concentrations of α-Syn species in oral mucosa samples were measured using electrochemiluminescence assays.

Results

Immunofluorescence images indicated elevated α-Syn, pS129, and α-Syn aggregates levels in oral mucosal cells of MSA than HCs. The concentrations of three α-Syn species were significantly higher in oral mucosal cells of MSA than HCs (α-Syn, p < 0.001; pS129, p = 0.042; α-Syn aggregates, p < 0.0001). In MSA patients, the oral mucosa α-Syn levels negatively correlated with disease duration (r = −0.398, p = 0.009). The area under curve (AUC) of receiver operating characteristic (ROC) analysis using an integrative model including age, gender, α-Syn, pS129, and α-Syn aggregates for MSA diagnosis was 0.825, with 73.8% sensitivity and 78.7% specificity.

Conclusion

The α-Syn levels in oral mucosal cells elevated in patients with MSA, which may be promising biomarkers for MSA.

Detection and assessment of alpha-synuclein in Parkinson disease

PURPOSE

Different studies have reported varying alpha-synuclein values in the cerebrospinal fluid (CSF), serum, and plasma, making determination of the alpha-synuclein cutoff value for Parkinson's disease difficult and rendering identifying the cause of variation essential.

METHOD

We searched PubMed from inception to June 2021 and identified 76 eligible studies. Included studies reported data on total, phosphorylated, and oligomeric alpha-synuclein in the CSF, serum, or plasma from individuals with Parkinson's disease and healthy controls. The mean or median alpha-synuclein values from the included studies were summarized and categorized through laboratory assays to visualize potential trends.

RESULTS

The enzyme-linked immunosorbent assay (ELISA) is the most common assay used to determine alpha-synuclein concentrations. Less common assays include Luminex, single molecule arrays, electrochemiluminescence, and immunomagnetic reduction (IMR). IMR is a single-antibody and wash-free immunoassay designed for determining the extremely low concentration of bio-molecules. For patients with Parkinson's disease, the median or mean testing values ranged from 60.9 to 55,000 pg/mL in the CSF, 0.446 to 1,777,100 pg/mL in plasma, and 0.0292 to 38,200,000 pg/mL in serum. The antibody selection was diverse between studies. The tendency of distribution was more centralized among studies that used the same kit. Studies adopting specific antibodies or in-house assays contribute to the extreme values. Only a few studies on phosphorylated and oligomeric alpha-synuclein were included.

CONCLUSION

The type of assay and antibody selection in the laboratory played major roles in the alpha-synuclein variation. Studies that used the same assay and kit yielded relatively unanimous results. Furthermore, IMR may be a promising assay for plasma and serum alpha-synuclein quantification. A consensus on sample preparation and testing protocol unification is warranted in the future.

A Proposed Roadmap for Parkinson's Disease Proof of Concept Clinical Trials Investigating Compounds Targeting Alpha-Synuclein

The convergence of human molecular genetics and Lewy pathology of Parkinson's disease (PD) have led to a robust, clinical-stage pipeline of alpha-synuclein (α-syn)-targeted therapies that have the potential to slow or stop the progression of PD and other synucleinopathies. To facilitate the development of these and earlier stage investigational molecules, the Michael J. Fox Foundation for Parkinson's Research convened a group of leaders in the field of PD research from academia and industry, the Alpha-Synuclein Clinical Path Working Group. This group set out to develop recommendations on preclinical and clinical research that can de-risk the development of α-syn targeting therapies. This consensus white paper provides a translational framework, from the selection of animal models and associated end-points to decision-driving biomarkers as well as considerations for the design of clinical proof-of-concept studies. It also identifies current gaps in our biomarker toolkit and the status of the discovery and validation of α-syn-associated biomarkers that could help fill these gaps. Further, it highlights the importance of the emerging digital technology to supplement the capture and monitoring of clinical outcomes. Although the development of disease-modifying therapies targeting α-syn face profound challenges, we remain optimistic that meaningful strides will be made soon toward the identification and approval of disease-modifying therapeutics targeting α-syn.

Blood Contamination in CSF and Its Impact on Quantitative Analysis of Alpha-Synuclein

Analysis of cerebrospinal fluid (CSF) is important for diagnosis of neurological diseases. Especially for neurodegenerative diseases, abnormal protein abundance in CSF is an important biomarker. However, the quality of CSF is a key factor for the analytic outcome. Any external contamination has tremendous impact on the analysis and the reliability of the results. In this study, we evaluated the effect of blood contamination in CSF with respect to protein biomarker identification. We compared three distinct measures: Combur10-Test^® strips, a specific hemoglobin ELISA, and bottom-up mass spectrometry (MS)-based proteomics for the determination of the general blood contamination level. In parallel, we studied the impact of blood contamination on the detectability of alpha-synuclein (aSyn), a highly abundant protein in blood/erythrocytes and a potential biomarker for Parkinson’s disease. Comparable results were achieved, with all three approaches enabling detection of blood levels in CSF down to 0.001%. We found higher aSyn levels with increasing blood contamination, highlighting the difficulty of authentic quantification of this protein in CSF. Based on our results, we identified other markers for blood contamination beyond hemoglobin and defined a grading system for blood levels in CSF samples, including a lower limit of tolerable blood contamination for MS-based biomarker studies.