Combined Active Humoral and Cellular Immunization Approaches for the Treatment of Synucleinopathies

Dementia with Lewy bodies, Parkinson's disease, and Multiple System Atrophy are age-related neurodegenerative disorders characterized by progressive accumulation of α-synuclein (α-syn) and jointly termed synucleinopathies. Currently, no disease-modifying treatments are available for these disorders. Previous preclinical studies demonstrate that active and passive immunizations targeting α-syn partially ameliorate behavioral deficits and α-syn accumulation; however, it is unknown whether combining humoral and cellular immunization might act synergistically to reduce inflammation and improve microglial-mediated α-syn clearance. Since combined delivery of antigen plus rapamycin (RAP) in nanoparticles is known to induce antigen-specific regulatory T cells (Tregs), we adapted this approach to α-syn using the antigen-presenting cell-targeting glucan microparticle (GP) vaccine delivery system. PDGF-α-syn transgenic (tg) male and female mice were immunized with GP-alone, GP-α-syn (active humoral immunization), GP+RAP, or GP+RAP/α-syn (combined active humoral and Treg) and analyzed using neuropathological and biochemical markers. Active immunization resulted in higher serological total IgG, IgG1, and IgG2a anti-α-syn levels. Compared with mice immunized with GP-alone or GP-α-syn, mice vaccinated with GP+RAP or GP+RAP/α-syn displayed increased numbers of CD25-, FoxP3-, and CD4-positive cells in the CNS. GP-α-syn or GP+RAP/α-syn immunizations resulted in a 30-45% reduction in α-syn accumulation, neuroinflammation, and neurodegeneration. Mice immunized with GP+RAP/α-syn further rescued neurons and reduced neuroinflammation. Levels of TGF-β1 were increased with GP+RAP/α-syn immunization, while levels of TNF-α and IL-6 were reduced. We conclude that the observed effects of GP+RAP/α-syn immunization support the hypothesis that cellular immunization may enhance the effects of active immunotherapy for the treatment of synucleinopathies. We show that a novel vaccination modality combining an antigen-presenting cell-targeting glucan particle (GP) vaccine delivery system with encapsulated antigen (α-synuclein) + rapamycin (RAP) induced both strong anti-α-synuclein antibody titers and regulatory T cells (Tregs). This vaccine, collectively termed GP+RAP/α-syn, is capable of triggering neuroprotective Treg responses in synucleinopathy models, and the combined vaccine is more effective than the humoral or cellular immunization alone. Together, these results support the further de