The development of therapeutics for neurodegenerative diseases requires the establishment of biomarker assays to enable stratifying patients, monitoring disease progression, and assessing target engagement. Several therapeutic approaches are currently being pursued to target the protein α-Synuclein (αSYN), all of which require sensitive assays for accurate assessment of αSYN levels to assess target engagement and therapeutic efficacy. Nevertheless, the accurate detection and quantification of total αSYN and its pathologically relevant variants continues to represent a major challenge as demonstrated by marked discrepancies in αSYN levels reported by different studies and laboratories. The reasons underlying these discrepancies could include, amongst others, the heterogeneity of patients and sample-handling procedures, as well as the possibility that the antibodies deployed in immuno-assays might not capture the complexity of αSYN in biological fluids, such as splicing isoforms and proteolytic fragments of αSYN, or post-translationally modified (PTM) forms of αSYN.

In this recent study published in the Journal of Parkinson’s disease, ND Biosciences in collaboration with the Lashuel lab at the EPFL and ADX NeuroScience investigated whether the three commercial assays that have been extensively used for total αSYN quantification in human biological fluids (from Euroimmun, MSD, and Biolegend) are capable of capturing the diversity and complexity of relevant αSYN proteoforms. This thorough comparison, which was supported by the Michael J Fox Foundation for Parkinson’s Research (MJFF), showed that none of the tested immunoassays accurately capture the totality of relevant αSYN species, and that these assays are unable to recognize most disease-associated C-terminally truncated variants of αSYN.

This work provides new insights into why the current diagnostic assays based on detecting levels of the aSYN protein may have yielded inconsistent results, and provides tangible recommendations on needed upcoming steps to overcome this challenge. The authors discuss the importance of early and thorough antibody pre-assay characterization, and recommend the use of a comprehensive library of proteins that capture the complexity of aSYN as a critical approach for the development of accurate diagnostics and biomarker assays for aSYN. On the basis of these findings ND Biosciences has since received a new grant from the MJFF to develop a novel immunoassay that allows accurate quantification of total αSYN by capturing the diversity of both modified and aggregated forms of αSYN (link to announcement). 

Article Reference:

Petricca, L., Chiki, N., Hanna-El-Daher, L., Aeschbach, L., Burai, R., Stoops, E., Fares, M. B., and Lashuel, H. A. (2022). Comparative Analysis of Total Alpha-Synuclein (αSYN) Immunoassays Reveals That They Do Not Capture the Diversity of Modified αSYN Proteoforms. Journal of Parkinson’s disease, 12(5), 1449–1462. https://doi.org/10.3233/JPD-223285