Oligomeric α-synuclein and β-amyloid variants as potential biomarkers for Parkinson's and Alzheimer's diseases

• Published in: The European journal of neuroscience Vol. 43; no. 1; pp. 3 - 16
• Main Authors: Williams, Stephanie M., Schulz, Philip, Sierks, Michael R.
• Format: Journal Article
• Language: English
• Published: France Blackwell Publishing Ltd 01.01.2016
• Subjects: Aged; Aged, 80 and over; alpha-Synuclein - blood; alpha-Synuclein - cerebrospinal fluid; alpha-Synuclein - metabolism; Alzheimer Disease - blood; Alzheimer Disease - cerebrospinal fluid; Alzheimer Disease - diagnosis; Alzheimer Disease - metabolism; Amyloid beta-Peptides - blood; Amyloid beta-Peptides - cerebrospinal fluid; Amyloid beta-Peptides - metabolism; Biomarkers - blood; Biomarkers - cerebrospinal fluid; Biomarkers - metabolism; brain tissue; cerebrospinal fluid; Enzyme-Linked Immunosorbent Assay - methods; Female; Humans; Male; Parkinson Disease - blood; Parkinson Disease - cerebrospinal fluid; Parkinson Disease - diagnosis; Parkinson Disease - metabolism; Peptide Fragments - blood; Peptide Fragments - cerebrospinal fluid; Peptide Fragments - metabolism; phage capture enzyme-linked immunosorbent assay; Sensitivity and Specificity; serum; single-chain variable fragments; Temporal Lobe - metabolism; brain tissue; serum; phage capture enzyme-linked immunosorbent assay; cerebrospinal fluid; single-chain variable fragments
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/ejn.13056

Oligomeric forms of α‐synuclein and β‐amyloid are toxic protein variants that are thought to contribute to the onset and progression of Parkinson's disease (PD) and Alzheimer's disease (AD), respectively. The detection of toxic variants in human cerebrospinal fluid (CSF) and blood has great promise for facilitating early and accurate diagnoses of these devastating diseases. Two hurdles that have impeded the use of these protein variants as biomarkers are the availability of reagents that can bind the different variants and a sensitive assay to detect their very low concentrations. We previously isolated antibody‐based reagents that selectively bind two different oligomeric variants of α‐synuclein and two of β‐amyloid, and developed a phage‐based capture enzyme‐linked immunosorbent assay (ELISA) with subfemtomolar sensitivity to quantify their presence. Here, we used these reagents to show that these oligomeric α‐synuclein variants are preferentially present in PD brain tissue, CSF and serum, and that the oligomeric β‐amyloid variants are preferentially present in AD brain tissue, CSF, and serum. Some AD samples also had α‐synuclein pathology and some PD samples also had β‐amyloid pathology, and, very intriguingly, these PD cases also had a history of dementia. Detection of different oligomeric α‐synuclein and β‐amyloid species is an effective method for identifying tissue, CSF and sera from PD and AD samples, respectively, and samples that also contained early stages of other protein pathologies, indicating their potential value as blood‐based biomarkers for neurodegenerative diseases. Anti‐oligomeric alpha‐synuclein antibodies preferentially recognized PD cases, whereas anti‐oligomeric beta‐amyloid antibodies favored AD cases. Oligomeric protein variants were identified in human brain tissue, CSF and sera using the corresponding antibodies. Multiple protein pathologies were also detected in some cases. Recognition in sera indicates the sensitivity of our phage ELISA technology and its potential to simplify future diagnostic procedures.