ABBV-0805, a novel antibody selective for soluble aggregated α-synuclein, prolongs lifespan and prevents buildup of α-synuclein pathology in mouse models of Parkinson's disease.

A growing body of evidence suggests that aggregated α-synuclein, the major constituent of Lewy bodies, plays a key role in the pathogenesis of Parkinson's disease and related α-synucleinopathies. Immunotherapies, both active and passive, against α-synuclein have been developed and are promising novel treatment strategies for such disorders. Here, we report on the humanization and pharmacological characteristics of ABBV-0805, a monoclonal antibody that exhibits a high selectivity for human aggregated α-synuclein and very low affinity for monomers. ABBV-0805 binds to a broad spectrum of soluble aggregated α-synuclein, including small and large aggregates of different conformations. Binding of ABBV-0805 to pathological α-synuclein was demonstrated in Lewy body-positive post mortem brains of Parkinson's disease patients. The functional potency of ABBV-0805 was demonstrated in several cellular assays, including Fcγ-receptor mediated uptake of soluble aggregated α-synuclein in microglia and inhibition of neurotoxicity in primary neurons. In vivo, the murine version of ABBV-0805 (mAb47) displayed significant dose-dependent decrease of α-synuclein aggregates in brain in several mouse models, both in prophylactic and therapeutic settings. In addition, mAb47 treatment of α-synuclein transgenic mice resulted in a significantly prolonged survival. ABBV-0805 selectively targets soluble toxic α-synuclein aggregates with a picomolar affinity and demonstrates excellent in vivo efficacy. Based on the strong preclinical findings described herein, ABBV-0805 has been progressed into clinical development as a potential disease-modifying treatment for Parkinson's disease.

Region-Specific Effects of Immunotherapy With Antibodies Targeting α-synuclein in a Transgenic Model of Synucleinopathy.

Synucleinopathies represent a group of neurodegenerative disorders which are characterized by intracellular accumulation of aggregated α-synuclein. α-synuclein misfolding and oligomer formation is considered a major pathogenic trigger in these disorders. Therefore, targeting α-synuclein species represents an important candidate therapeutic approach. Our aim was to analyze the biological effects of passive immunization targeting α-synuclein and to identify the possible underlying mechanisms in a transgenic mouse model of oligodendroglial α-synucleinopathy. We used PLP-α-synuclein mice overexpressing human α-synuclein in oligodendrocytes. The animals received either antibodies that recognize α-synuclein or vehicle. Passive immunization mitigated α-synuclein pathology and resulted in reduction of total α-synuclein in the hippocampus, reduction of intracellular accumulation of aggregated α-synuclein, particularly significant in the spinal cord. Lowering of the extracellular oligomeric α-synuclein was associated with reduction of the density of activated iba1-positive microglia profiles. However, a shift toward phagocytic microglia was seen after passive immunization of PLP-α-synuclein mice. Lowering of intracellular α-synuclein was mediated by autophagy degradation triggered after passive immunization in PLP-α-synuclein mice. In summary, the study provides evidence for the biological efficacy of immunotherapy in a transgenic mouse model of oligodendroglial synucleinopathy. The different availability of the therapeutic antibodies and the variable load of α-synuclein pathology in selected brain regions resulted in differential effects of the immunotherapy that allowed us to propose a model of the underlying mechanisms of antibody-aided α-synuclein clearance.

Human Astrocytes Transfer Aggregated Alpha-Synuclein via Tunneling Nanotubes.

Many lines of evidence suggest that the Parkinson's disease (PD)-related protein α-synuclein (α-SYN) can propagate from cell to cell in a prion-like manner. However, the cellular mechanisms behind the spreading remain elusive. Here, we show that human astrocytes derived from embryonic stem cells actively transfer aggregated α-SYN to nearby astrocytes via direct contact and tunneling nanotubes (TNTs). Failure in the astrocytes' lysosomal digestion of excess α-SYN oligomers results in α-SYN deposits in the trans-Golgi network followed by endoplasmic reticulum swelling and mitochondrial disturbances. The stressed astrocytes respond by conspicuously sending out TNTs, enabling intercellular transfer of α-SYN to healthy astrocytes, which in return deliver mitochondria, indicating a TNT-mediated rescue mechanism. Using a pharmacological approach to inhibit TNT formation, we abolished the transfer of both α-SYN and mitochondria. Together, our results highlight the role of astrocytes in α-SYN cell-to-cell transfer, identifying possible pathophysiological events in the PD brain that could be of therapeutic relevance.SIGNIFICANCE STATEMENT Astrocytes are the major cell type in the brain, yet their role in Parkinson's disease progression remains elusive. Here, we show that human astrocytes actively transfer aggregated α-synuclein (α-SYN) to healthy astrocytes via direct contact and tunneling nanotubes (TNTs), rather than degrade it. The astrocytes engulf large amounts of oligomeric α-SYN that are subsequently stored in the trans-Golgi network region. The accumulation of α-SYN in the astrocytes affects their lysosomal machinery and induces mitochondrial damage. The stressed astrocytes respond by sending out TNTs, enabling intercellular transfer of α-SYN to healthy astrocytes. Our findings highlight an unexpected role of astrocytes in the propagation of α-SYN pathology via TNTs, revealing astrocytes as a potential target for therapeutic intervention.

Low molar excess of 4-oxo-2-nonenal and 4-hydroxy-2-nonenal promote oligomerization of alpha-synuclein through different pathways.

Aggregated alpha-synuclein is the main component of Lewy bodies, intraneuronal inclusions found in brains with Parkinson's disease and dementia with Lewy bodies. A body of evidence implicates oxidative stress in the pathogenesis of these diseases. For example, a large excess (30:1, aldehyde:protein) of the lipid peroxidation end products 4-oxo-2-nonenal (ONE) or 4-hydroxy-2-nonenal (HNE) can induce alpha-synuclein oligomer formation. The objective of the study was to investigate the effect of these reactive aldehydes on alpha-synuclein at a lower molar excess (3:1) at both physiological (7.4) and acidic (5.4) pH. As observed by size-exclusion chromatography, ONE rapidly induced the formation of alpha-synuclein oligomers at both pH values, but the effect was less pronounced under the acidic condition. In contrast, only a small proportion of alpha-synuclein oligomers were formed with low excess HNE-treatment at physiological pH and no oligomers at all under the acidic condition. With prolonged incubation times (up to 96h), more alpha-synuclein was oligomerized at physiological pH for both ONE and HNE. As determined by Western blot, ONE-oligomers were more SDS-stable and to a higher-degree cross-linked as compared to the HNE-induced oligomers. However, as shown by their greater sensitivity to proteinase K treatment, ONE-oligomers, exhibited a less compact structure than HNE-oligomers. As indicated by mass spectrometry, ONE modified most Lys residues, whereas HNE primarily modified the His50 residue and fewer Lys residues, albeit to a higher degree than ONE. Taken together, our data show that the aldehydes ONE and HNE can modify alpha-synuclein and induce oligomerization, even at low molar excess, but to a higher degree at physiological pH and seemingly through different pathways.

Extensive uptake of α-synuclein oligomers in astrocytes results in sustained intracellular deposits and mitochondrial damage.

The presence of Lewy bodies, mainly consisting of aggregated α-synuclein, is a pathological hallmark of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). The α-synuclein inclusions are predominantly found in neurons, but also appear frequently in astrocytes. However, the pathological significance of α-synuclein inclusions in astrocytes and the capacity of glial cells to clear toxic α-synuclein species remain unknown. In the present study we investigated uptake, degradation and toxic effects of oligomeric α-synuclein in a co-culture system of primary neurons, astrocytes and oligodendrocytes. Alpha-synuclein oligomers were found to co-localize with the glial cells and the astrocytes were found to internalize particularly large amounts of the protein. Following ingestion, the astrocytes started to degrade the oligomers via the lysosomal pathway but, due to incomplete digestion, large intracellular deposits remained. Moreover, the astrocytes displayed mitochondrial abnormalities. Taken together, our data indicate that astrocytes play an important role in the clearance of toxic α-synuclein species from the extracellular space. However, when their degrading capacity is overburdened, α-synuclein deposits can persist and result in detrimental cellular processes.

Mapping of Surface-Exposed Epitopes of In Vitro and In Vivo Aggregated Species of Alpha-Synuclein.

Aggregated alpha-synuclein is the main component of Lewy bodies, intraneuronal deposits observed in Parkinson's disease and dementia with Lewy bodies. The objective of the study was to identify surface-exposed epitopes of alpha-synuclein in vitro and in vivo formed aggregates. Polyclonal immunoglobulin Y antibodies were raised against short linear peptides of the alpha-synuclein molecule. An epitope in the N-terminal region (1-10) and all C-terminal epitopes (90-140) were found to be exposed in an indirect enzyme-linked immunosorbent assay (ELISA) using recombinant monomeric, oligomeric, and fibrillar alpha-synuclein. In a phospholipid ELISA, the N-terminus and mid-region of alpha-synuclein (i.e., 1-90) were associated with phosphatidylserine and thus occluded from antibody binding. The antibodies that reacted most strongly with epitopes in the in vitro aggregates (i.e., 1-10 and epitopes between positions 90-140) also labeled alpha-synuclein inclusions in brains from transgenic (Thy-1)-h[A30P] alpha-synuclein mice and Lewy bodies and Lewy neurites in brains of patients with alpha-synucleinopathies. However, differences in reactivity were observed with the C-terminal antibodies when brain tissue from human and transgenic mice was compared. Taken together, the study shows that although similar epitopes are exposed in both in vitro and in vivo formed alpha-synuclein inclusions, structural heterogeneity can be observed between different molecular species.