Title: α-Synuclein Autoimmunity in Parkinson’s Disease
Description: Parkinson’s disease (PD) is a multi-organ disorder. It is diagnosed from motor impairments that arise from neurodegeneration in the midbrain. However, the disease begins decades earlier in the gut prior to involvement of the brain. PD is characterized by persistent inflammation, both in the brain and in the periphery in addition to neurodegeneration. Here, I investigate the role of the adaptive immune system in disease pathogenesis and as a driver of prodromal symptoms of PD in both humans and mice. In Chapter 1, I introduce Parkinson’s disease, its pathological hallmarks and the progression of the symptoms, and discuss genetic and environmental influences. Then, I elaborate on the inflammatory phenotypes observed in the disease and recent work describing the role of inflammation in animal models for PD. In Chapter 2, I examine the autoimmune features of Parkinson’s disease from analysis of patients’ blood. I found that approximately 40% of PD patients possess aspects of autoimmunity against α-synuclein.

By screening peripheral blood mononuclear cells of patients and healthy controls for potential neoantigens derived from α-synuclein protein, I identified two antigenic regions of the protein that elicit an immune response. The immune responses to a specific α-synuclein neo-antigens were linked to unique HLAs that are over-represented in our PD cohort and are associated with PD in genome wide association studies (GWAS). In Chapters 3 and 4, I describe the effects of recapitulating α-synuclein autoimmunity in a humanized mouse strain expressing the HLA allele risk for PD. In Chapter 3, I show that the humoral and cellular immunity is mounted against α-synuclein in the humanized mice, similar to what is observed in PD patients; however, there is no inflammation or immune response toward the brain. In Chapter 4, I show how the autoimmune response to α-synuclein induces inflammation and neurodegeneration in the gut leading to constipation in mice, recapitulating the prodromal aspects of the human disease.

Finally, in Chapter 5, I discuss the implications of these findings for α-synuclein autoimmunity in the periphery, gut and brain in Parkinson’s disease. I also elaborate on the implications of these findings for potential future diagnostic screening and treatments for Parkinson’s disease.