Objective: Utilize a cell-based assay to determine whether a-syn seeding activity can be amplified and  detected from blood components from patients with Parkinson’s disease (PD) and multiple system atrophy (MSA).

Background: One major obstacle to advancement of diagnosis and therapies in Parkinson’s disease is the lack of a blood-based biomarker. Pathogenic forms of a-syn capable of inducing further aggregation of a-syn or “seeding activity” have been found in brain and CSF. Although a-syn has been detected in various blood components including red blood cells, plasma and platelets, the aggregation potential or pathogenicity of these forms of a-syn is not known. In prior studies of PD and MSA, we utilized a cell-based a-syn-A53T CFP/YFP assay to detect and quantify a-syn seeding activity present in both PD and MSA brain extracts [1]. Recent amplification-based techniques including quaking-induced conversion methods utilize thioflavin T to detect fibrillar forms of a-syn in CSF, but have not yet detected a-syn aggregation from blood samples.

Method: Blood was drawn from patients with diagnoses of PD or non-synucleinopathy (control). A limited number of samples from probable MSA patients were also obtained. Blood was separated into plasma and red blood cells (RBC) by centrifugation. A separate tube of blood was processed for extraction of platelets. a-Syn from these blood components were amplified using a quaking conversion method and then assayed for a-syn seeding activity utilizing a-syn-A53T CFP/YFP cells. Immunoblot and immunofluorescence methods were utilized to assess a-syn concentration.

Results: We were able to detect a-syn in isolated platelets and red blood cell samples from patients both with PD and non-synucleinopathy controls. RBCs from MSA patients demonstrated early and robust a-syn seeding activity when amplified utilizing a quaking conversion method. PD RBCs and control RBCs had less robust activity. Platelets were also capable of inducing a-syn aggregation in biosensor cells after amplification, however, there was not significant ability to distinguish between PD, MSA, and control in this small subset.

Conclusion: The results of these studies support the idea that a-syn seeding activity is present in blood components of patients with synucleinopathies and suggest the ability to differentiate PD from MSA. However, further studies are needed to determine whether this will be a viable biomarker for the disease process.

References: 1. Yamasaki, T.R., Holmes, B.B., Furman, J.L. Dhavale, D.D., Su, B.W., Song E.S., Cairns, N.J., Kotzbauer, P.T., and Diamond M.I. (2019). Parkinson’s disease and multiple system atrophy have distinct alpha-synuclein seed characteristics. Journal of Biological Chemistry 18:294(3) 1045-1058. PMCID: PMC6341389

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MDS Abstracts - https://www.mdsabstracts.org/abstract/alpha-synuclein-seeding-activity-in-blood-samples-from-synucleinopathy-patients/