A Single Chain Fragment Variant Binding Misfolded Alpha-Synuclein Exhibits Neuroprotective and Antigen-Specific Anti-Inflammatory Properties

Introduction. Alpha synuclein (alpha Syn) misfolding plays a requisite role in the pathogenesis of synucleinopathies. Direct toxicity to neurons, triggering neuroinflammation as well as the spreading and seeding of alpha Syn pathology are essential pathogenetic underlying mechanisms. Immunotherapy in experimental Parkinson's disease (PD) has been shown to be consistently effective in preclinical models, yet the initial clinical trials with monoclonal antibodies (mAbs) yielded marginal results if any. Aiming to overcome some of the limitation of this approach, we aimed to select an alpha Syn binding scFv antibody format and test it in multiple experimental PD in vivo models. Methods. We cloned the lead alpha Syn scFv based on preselection of human phage display libraries of human Fab. The selected of scFv targeting both oligomers and pre-formed fibrils (PFF) of alpha Syn were tested for their ability to protect neurons from triggered toxicity, influence their uptake to microglia, and accelerate misfolded alpha Syn degradation. The lead scFv- sMB08, was also tested for its ability to impact alpha Syn aggregation as well as spreading and seeding. Results. sMB08 was shown to protect neurons from misfolded alpha Syn mediated toxicity, promote its intracellular degradation, and to reduce its uptake by microglia. sMB08 exhibited anti-inflammatory properties, including its ability to attenuate adaptive alpha Syn autoimmunity and ameliorate proinflammatory cytokine expression in brains of mice stereotactically injected with PFF. Employing three experimental models of PD, intranasal treatment with sMB08 attenuated motoric dysfunction and achieved acceptable brain levels by pharmacokinetic analysis, leading to significant preservation of dopaminergic n neurons. Conclusion: sMB08, a scFv targeting both alpha Syn oligomers and PFF, due to its small size facilitating paraneural brain penetration and avoidance of nonspecific inflammation, appears as an attractive approach to test in patients with PD by addressing the major mechanisms that mediate misfolded alpha Syn driven pathology.

Automated summary

The study found that the antibody sMB08 can protect neurons from the toxic effects of alpha Syn and promote its degradation, while reducing its uptake by microglia. When applied in experimental models, sMB08 can alleviate motor dysfunction in Parkinson's disease and preserve dopaminergic neurons.