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 alpha-synuclein (alpha-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 alpha-syn partially ameliorate behavioral deficits and alpha-syn accumulation; however, it is unknown whether combining humoral and cellular immunization might act synergistically to reduce inflammation and improve microglial-mediated alpha-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 alpha-syn using the antigen-presenting cell-targeting glucan microparticle(GP) vaccine delivery system. PDGF-alpha-syn transgenic(tg) male and female mice were immunized with GP-alone, GP-alpha-syn (active humoral immunization), GP+RAP, or GP+RAP/alpha-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-alpha-syn levels. Compared with mice immunized with GP-alone or GP-alpha-syn, mice vaccinated with GP+RAP or GP+RAP/alpha-syn displayed increased numbers of CD25-, FoxP3-, and CD4-positive cells in the CNS. GP-alpha-syn or GP+RAP/alpha-syn immunizations resulted in a 30-45% reduction in alpha-syn accumulation, neuroinflammation, and neurodegeneration. Mice immunized with GP+RAP/alpha-syn further rescued neurons and reduced neuroinflammation. Levels of TGF-alpha 1 were increased with GP+RAP/alpha-syn immunization, while levels of TNF-alpha and IL-6 were reduced. We conclude that the observed effects of GP+RAP/alpha-syn immunization support the hypothesis that cellular immunization may enhance the effects of active immunotherapy for the treatment of synucleinopathies.