Measurements of auto-antibodies to -synuclein in the serum and cerebral spinal fluids of patients with Parkinson's disease

Biomarkers for -synuclein are needed for diagnosis and prognosis in Parkinson's disease (PD). Endogenous auto-antibodies to -synuclein could serve as biomarkers for underlying synucleinopathy, but previous assessments of auto-antibodies have shown variability and inconsistent clinical correlations. We hypothesized that auto-antibodies to -synuclein could be diagnostic for PD and explain its clinical heterogeneity. To test this hypothesis, we developed an enzyme-linked immunosorbent assay for measuring -synuclein auto-antibodies in human samples. We evaluated 69 serum samples (16 healthy controls (HC) and 53 PD patients) and 145 CSF samples (52 HC and 93 PD patients) from our Institution. Both serum and CSF were available for 24 participants. Males had higher auto-antibody levels than females in both fluids. CSF auto-antibody levels were significantly higher in PD patients as compared with HC, whereas serum levels were not significantly different. CSF auto-antibody levels did not associate with amyloid-(1-42), total tau, or phosphorylated tau. CSF auto-antibody levels correlated with performance on the Montreal Cognitive Assessment, even when controlled for CSF amyloid(1-42). CSF hemoglobin levels, as a proxy for contamination of CSF by blood during lumbar puncture, did not influence these observations. Using recombinant -synuclein with N- and C-terminal truncations, we found that CSF auto-antibodies target amino acids 100 through 120 of -synuclein. We conclude that endogenous CSF auto-antibodies are significantly higher in PD patients as compared with HC, suggesting that they could indicate the presence of underlying synucleinopathy. These auto-antibodies associate with poor cognition, independently of CSF amyloid(1-42), and target a select C-terminal region of -synuclein.