Targeting amyotrophic lateral sclerosis by neutralizing seeding-competent TDP-43 in CSF.

In amyotrophic lateral sclerosis, a disease driven by abnormal transactive response DNA-binding protein of 43 kDa aggregation, CSF may contain pathological species of transactive response DNA-binding protein of 43 kDa contributing to the propagation of pathology and neuronal toxicity. These species, released in part by degenerating neurons, would act as a template for the aggregation of physiological protein contributing to the spread of pathology in the brain and spinal cord. In this study, a robust seed amplification assay was established to assess the presence of seeding-competent transactive response DNA-binding protein of 43 kDa species in CSF of apparently sporadic amyotrophic lateral sclerosis patients. These samples resulted in a significant acceleration of substrate aggregation differentiating the kinetics from healthy controls. In parallel, a second assay was developed to determine the level of target engagement that would be necessary to neutralize such species in human CSF by a therapeutic monoclonal antibody targeting transactive response DNA-binding protein of 43 kDa. For this, evaluation of the pharmacokinetic/pharmacodynamic effect for the monoclonal antibody, ACI-5891.9, in vivo and in vitro confirmed that a CSF concentration of ≍1100 ng/mL would be sufficient for sustained target saturation. Using this concentration in the seed amplification assay, ACI-5891.9 was able to neutralize the transactive response DNA-binding protein of 43 kDa pathogenic seeds derived from amyotrophic lateral sclerosis patient CSF. This translational work adds to the evidence of transmission of transactive response DNA-binding protein of 43 kDa pathology via CSF that could contribute to the non-contiguous pattern of clinical manifestations observed in amyotrophic lateral sclerosis and demonstrates the ability of a therapeutic monoclonal antibody to neutralize the toxic, extracellular seeding-competent transactive response DNA-binding protein of 43 kDa species in the CSF of apparently sporadic amyotrophic lateral sclerosis patients.

Immunotherapy targeting the C-terminal domain of TDP-43 decreases neuropathology and confers neuroprotection in mouse models of ALS/FTD.

Effective therapies are urgently needed to safely target TDP-43 pathology as it is closely associated with the onset and development of devastating diseases such as frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP) and amyotrophic lateral sclerosis (ALS). In addition, TDP-43 pathology is present as a co-pathology in other neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Our approach is to develop a TDP-43-specific immunotherapy that exploits Fc gamma-mediated removal mechanisms to limit neuronal damage while maintaining physiological TDP-43 function. Thus, using both in vitro mechanistic studies in conjunction with the rNLS8 and CamKIIa inoculation mouse models of TDP-43 proteinopathy, we identified the key targeting domain in TDP-43 to accomplish these therapeutic objectives. Targeting the C-terminal domain of TDP-43 but not the RNA recognition motifs (RRM) reduces TDP-43 pathology and avoids neuronal loss in vivo. We demonstrate that this rescue is dependent on Fc receptor-mediated immune complex uptake by microglia. Furthermore, monoclonal antibody (mAb) treatment enhances phagocytic capacity of ALS patient-derived microglia, providing a mechanism to restore the compromised phagocytic function in ALS and FTD patients. Importantly, these beneficial effects are achieved while preserving physiological TDP-43 activity. Our findings demonstrate that a mAb targeting the C-terminal domain of TDP-43 limits pathology and neurotoxicity, enabling clearance of misfolded TDP-43 through microglia engagement, and supporting the clinical strategy to target TDP-43 by immunotherapy. SIGNIFICANCE STATEMENT: TDP-43 pathology is associated with various devastating neurodegenerative disorders with high unmet medical needs such as frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS) and Alzheimer's disease. Thus, safely and effectively targeting pathological TDP-43 represents a key paradigm for biotechnical research as currently there is little in clinical development. After years of research, we have determined that targeting the C-terminal domain of TDP-43 rescues multiple patho-mechanisms involved in disease progression in two animal models of FTD/ALS. In parallel, importantly, our studies establish that this approach does not alter the physiological functions of this ubiquitously expressed and indispensable protein. Together, our findings substantially contribute to the understanding of TDP-43 pathobiology and support the prioritization for clinical testing of immunotherapy approaches targeting TDP-43.

An integrated genomic approach to dissect the genetic landscape regulating the cell-to-cell transfer of α-synuclein.

Neuropathological and experimental evidence suggests that the cell-to-cell transfer of α-synuclein has an important role in the pathogenesis of Parkinson's disease (PD). However, the mechanism underlying this phenomenon is not fully understood. We undertook a small interfering RNA (siRNA), genome-wide screen to identify genes regulating the cell-to-cell transfer of α-synuclein. A genetically encoded reporter, GFP-2A-αSynuclein-RFP, suitable for separating donor and recipient cells, was transiently transfected into HEK cells stably overexpressing α-synuclein. We find that 38 genes regulate the transfer of α-synuclein-RFP, one of which is ITGA8, a candidate gene identified through a recent PD genome-wide association study (GWAS). Weighted gene co-expression network analysis (WGCNA) and weighted protein-protein network interaction analysis (WPPNIA) show that those hits cluster in networks that include known PD genes more frequently than expected by random chance. The findings expand our understanding of the mechanism of α-synuclein spread.

Sensory neurons accelerate skin reepithelialization via substance P in an innervated tissue-engineered wound healing model.

Keratinocytes are responsible for reepithelialization and restoration of the epidermal barrier during wound healing. The influence of sensory neurons on this mechanism is not fully understood. We tested whether sensory neurons influence wound closure via the secretion of the neuropeptide substance P (SP) with a new tissue-engineered wound healing model made of an upper-perforated epidermal compartment reconstructed with human keratinocytes expressing green fluorescent protein, stacked over a dermal compartment, innervated or not with sensory neurons. We showed that sensory neurons secreted SP in the construct and induced a two times faster wound closure in vitro. This effect was partially reproduced by addition of SP in the model without neurons, and completely blocked by a treatment with a specific antagonist of the SP receptor neurokinin-1 expressed by keratinocytes. However, this antagonist did not compromise wound closure compared with the control. Similar results were obtained when the model with or without neurons was transplanted on CD1 mice, while wound closure occurred faster. We conclude that sensory neurons play an important, but not essential, role in wound healing, even in absence of the immune system. This model is promising to study the influence of the nervous system on reepithelialization in normal and pathological conditions.