Alpha-Synuclein-Specific Naturally Occurring Antibodies Inhibit Aggregation In Vitro and In Vivo

Parkinson's disease (PD) is associated with motor and non-motor symptoms and characterized by aggregates of alpha-synuclein (alpha Syn). Naturally occurring antibodies (nAbs) are part of the innate immune system, produced without prior contact to their specific antigen, and polyreactive. The abundance of nAbs against alpha Syn is altered in patients with PD. In this work, we biophysically characterized nAbs against alpha Syn (nAbs-alpha Syn) and determined their biological effects. nAbs-alpha Syn were isolated from commercial intravenous immunoglobulins using column affinity purification. Biophysical properties were characterized using a battery of established in vitro assays. Biological effects were characterized in HEK293T cells transiently transfected with fluorescently tagged alpha Syn. Specific binding of nAbs-alpha Syn to monomeric alpha Syn was demonstrated by Dot blot, ELISA, and Surface Plasmon Resonance. nAbs-alpha Syn did not affect viability of HEK293T cells as reported by Cell Titer Blue and LDH Assays. nAbs-alpha Syn inhibited fibrillation of alpha Syn reported by the Thioflavin T aggregation assay. Altered fibril formation was confirmed with atomic force microscopy. In cells transfected with EGFP-tagged alpha Syn we observed reduced formation of aggresomes, perinuclear accumulations of alpha Syn aggregates. The results demonstrate that serum of healthy individuals contains nAbs that specifically bind alpha Syn and inhibit aggregation of alpha Syn in vitro. The addition of nAbs-alpha Syn to cultured cells affects intracellular alpha Syn aggregates. These findings help understanding the role of the innate immune systems for the pathogenesis of PD and suggest that systemic alpha Syn binding agents could potentially affect neuronal alpha Syn pathology.

Automated summary

Parkinson's disease is associated with changes in the abundance of naturally occurring antibodies (nAbs) against alpha-synuclein (α Syn). In this study, nAbs-alpha Syn were found to specifically bind monomeric α Syn and inhibit its aggregation in vitro. Additionally, the addition of nAbs-alpha Syn to cultured cells affected intracellular α Syn aggregates.