Effects of alpha-synuclein immunization in a mouse model of Parkinson's disease

The humoral immune landscape in Parkinson's disease: Unraveling antibody and B cell changes

Parkinson's disease (PD) is a complex neurodegenerative disorder characterized by the accumulation of α-synuclein (α-syn) in the brain and progressive loss of dopaminergic neurons in the substantia nigra (SN) region of the brain. Although the role of neuroinflammation and cellular immunity in PD has been extensively studied, the involvement of humoral immunity mediated by antibodies and B cells has received less attention. This article provides a comprehensive review of the current understanding of humoral immunity in PD. Here, we discuss alterations in B cells in PD, including changes in their number and phenotype. Evidence mostly indicates a decrease in the quantity of B cells in PD, accompanied by a shift in the population from naïve to memory cells. Furthermore, the existence of autoantibodies that target several antigens in PD has been investigated (i.e., anti-α-syn autoantibodies, anti-glial-derived antigen antibodies, anti-Tau antibodies, antineuromelanin antibodies, and antibodies against the renin-angiotensin system). Several autoantibodies are generated in PD, which may either provide protection or have harmful effects on disease progression. Furthermore, we have reviewed studies focusing on the utilization of antibodies as a potential treatment for PD, both in animal and clinical trials. This review sheds light on the intricate interplay between antibodies and the pathological processes in PD, including complement system activation.

Indoleamine 2,3-dioxygenase (IDO1) - Can dendritic cells and monocytes expressing this moonlight enzyme change the phase of Parkinson's Disease?

Parkinson's Disease (PD) is the second most common neurodegenerative disease where central and peripheral immune dysfunctions have been pointed out as a critical component of susceptibility and progression of this disease. Dendritic cells (DCs) and monocytes are key players in promoting immune response regulation and can induce the enzyme indoleamine 2,3-dioxygenase 1 (IDO1) under pro-inflammatory environments. This enzyme with catalytic and signaling activity supports the axis IDO1-KYN-aryl hydrocarbon receptor (AhR), promoting disease-specific immunomodulatory effects. IDO1 is a rate-limiting enzyme of the kynurenine pathway (KP) that begins tryptophan (Trp) catabolism across this pathway. The immune functions of the pathway, which are extensively described in cancer, have been forgotten so far in neurodegenerative diseases, where a chronic inflammatory environment underlines the progression of the disease. Despite dysfunctions of KP have been described in PD, these are mainly associated with neurotoxic functions. With this review, we aim to focus on the immune properties of IDO1+DCs and IDO1+monocytes as a possible strategy to balance the pro-inflammatory profile described in PD. We also highlight the importance of exploring the role of dopaminergic therapeutics in IDO1 modulation to possibly optimize current PD therapeutic strategies.

LETC inhibits α-Syn aggregation and ameliorates motor deficiencies in the L62 mouse model of synucleinopathy

Alpha-Synuclein (α-Syn) aggregation is a pathological feature of synucleinopathies, neurodegenerative disorders that include Parkinson's disease (PD). Here, we explored the efficacy of N,N,N',N'-tetraethyl-10H-phenothiazine-3,7-diamine dihydrochloride (LETC), a protein aggregation inhibitor, on α-Syn aggregation. In both cellular models and transgenic mice, α-Syn aggregation was achieved by the overexpression of full-length human α-Syn fused with a signal sequence peptide. α-Syn accumulated in transfected DH60.21 neuroblastoma cells and α-Syn aggregation was inhibited by LETC with an EC50 of 0.066 ± 0.047 μM. Full-length human α-Syn overexpressing Line 62 (L62) mice accumulated neuronal α-Syn that was associated with a decreased motor performance in the open field and automated home cage. LETC, administered orally for 6 weeks at 10 mg/kg significantly decreased α-Syn-positive neurons in multiple brain regions and this resulted in a rescue of movement deficits in the open field in these mice. LETC however, did not improve activity deficits of L62 mice in the home cage environment. The results suggest that LETC may provide a potential disease modification therapy in synucleinopathies through the inhibition of α-Syn aggregation.

Nonintuitive Immunogenicity and Plasticity of Alpha-Synuclein Conformers: A Paradigm for Smart Delivery of Neuro-Immunotherapeutics

Despite the extensive research successes and continuous developments in modern medicine in terms of diagnosis, prevention, and treatment, the lack of clinically useful disease-modifying drugs or immunotherapeutic agents that can successfully treat or prevent neurodegenerative diseases is an ongoing challenge. To date, only one of the 244 drugs in clinical trials for the treatment of neurodegenerative diseases has been approved in the past decade, indicating a failure rate of 99.6%. In corollary, the approved monoclonal antibody did not demonstrate significant cognitive benefits. Thus, the prevalence of neurodegenerative diseases is increasing rapidly. Therefore, there is an urgent need for creative approaches to identifying and testing biomarkers for better diagnosis, prevention, and disease-modifying strategies for the treatment of neurodegenerative diseases. Overexpression of the endogenous α-synuclein has been identified as the driving force for the formation of the pathogenic α-synuclein (α-Syn) conformers, resulting in neuroinflammation, hypersensitivity, endogenous homeostatic responses, oxidative dysfunction, and degeneration of dopaminergic neurons in Parkinson's disease (PD). However, the conformational plasticity of α-Syn proffers that a certain level of α-Syn is essential for the survival of neurons. Thus, it exerts both neuroprotective and neurotoxic (regulatory) functions on neighboring neuronal cells. Furthermore, the aberrant metastable α-Syn conformers may be subtle and difficult to detect but may trigger cellular and molecular events including immune responses. It is well documented in literature that the misfolded α-Syn and its conformers that are released into the extracellular space from damaged or dead neurons trigger the innate and adaptive immune responses in PD. Thus, in this review, we discuss the nonintuitive plasticity and immunogenicity of the α-Syn conformers in the brain immune cells and their physiological and pathological consequences on the neuroimmune responses including neuroinflammation, homeostatic remodeling, and cell-specific interactions that promote neuroprotection in PD. We also critically reviewed the novel strategies for immunotherapeutic delivery interventions in PD pathogenesis including immunotherapeutic targets and potential nanoparticle-based smart drug delivery systems. It is envisioned that a greater understanding of the nonintuitive immunogenicity of aberrant α-Syn conformers in the brain's microenvironment would provide a platform for identifying valid therapeutic targets and developing smart brain delivery systems for clinically effective disease-modifying immunotherapeutics that can aid in the prevention and treatment of PD in the future.

Tau Immunotherapies for Alzheimer's Disease and Related Tauopathies: Status of Trials and Insights from Preclinical Studies

 The tau protein undergoes pathological changes in Alzheimer's disease and other tauopathies that eventually lead to functional impairments. Over the years, several therapeutic approaches have been examined to slow or halt the progression of tau pathology but have yet to lead to an approved disease-modifying treatment. Of the drugs in clinical trials that directly target tau, immunotherapies are the largest category and mostly consist of antibodies in different stages of development. There is a reasonable optimism that at least some of these compounds will have a clinically meaningful efficacy. This view is based on the significant although modest efficacy of some antibodies targeting amyloid-β in Alzheimer's disease and the fact that tau pathology correlates much better with the degree of dementia than amyloid-β lesions. In Alzheimer's disease, clearing pathological tau may therefore improve function later in the disease process than when removing amyloid-β. This review provides a brief update on the active and passive clinical tau immunization trials with insight from preclinical studies. Various epitopes are being targeted and some of the antibodies are said to target extracellular tau but because almost all of pathological tau is found intracellularly, the most efficacious antibodies should be able to enter the cell.

Immunization Effects of a Novel α-Synuclein-Based Peptide Epitope Vaccine in Parkinson's Disease-Associated Pathology

Parkinson's disease (PD) is a chronic neurodegenerative disease that affects the central nervous system, specifically the motor system. It is mainly caused by the loss of dopamine due to the accumulation of α-synuclein (α-syn) protein in the striatum and substantia nigra pars compacta (SNpc). Previous studies have reported that immunization may be a potential preventive strategy for neurodegenerative diseases such as Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). Therefore, the aim of the study was to design an α-syn specific epitope vaccine and investigate its effect in PD-related pathophysiology using an α-syn-induced mouse model. We used an in silico model to identify and design a non-toxic α-syn-based peptide epitope vaccine and, to overcome poor immunogenicity, the vaccine was coupled with immunogenic carrier proteins, i.e., ovalbumin (OVA) and keyhole limpet haemocyanin (KLH). Our results showed that vaccinated PD mouse models, especially with vaccines with carrier proteins, improved in motor functions compared with the non-vaccinated PD model. Additionally, the vaccinated groups showed increased immunoglobulin G (IgG) levels in the spleen and plasma as well as decreased interleukin-10 (IL-10) levels in the plasma. Furthermore, vaccinated groups, especially OVA and KLH groups, showed decrease in α-syn levels and increased dopamine-related markers, i.e., tyrosine hydroxylase (TH), vesicle monoamine transporter 2 (VMAT2), and dopamine transporter (DAT), and autophagy activities in the striatum and SNpc. Lastly, our data showed decreased neuroinflammation by reducing the activation of microglia and astrocytes and pro-inflammatory cytokines in the immunized groups, especially with OVA and KLH carrier proteins. Overall, these results suggest that vaccination, especially with immunogenic carrier proteins, is effective in reducing the accumulation of α-syn aggregates in the brain and ameliorate PD-related pathophysiology. Hence, further development of this approach might have a potential role in preventing the development of PD.

Tau-targeting therapies for Alzheimer disease: current status and future directions

Alzheimer disease (AD) is the most common cause of dementia in older individuals. AD is characterized pathologically by amyloid-β (Aβ) plaques and tau neurofibrillary tangles in the brain, with associated loss of synapses and neurons, which eventually results in dementia. Many of the early attempts to develop treatments for AD focused on Aβ, but a lack of efficacy of these treatments in terms of slowing disease progression led to a change of strategy towards targeting of tau pathology. Given that tau shows a stronger correlation with symptom severity than does Aβ, targeting of tau is more likely to be efficacious once cognitive decline begins. Anti-tau therapies initially focused on post-translational modifications, inhibition of tau aggregation and stabilization of microtubules. However, trials of many potential drugs were discontinued because of toxicity and/or lack of efficacy. Currently, the majority of tau-targeting agents in clinical trials are immunotherapies. In this Review, we provide an update on the results from the initial immunotherapy trials and an overview of new therapeutic candidates that are in clinical development, as well as considering future directions for tau-targeting therapies.

Differential involvement of amyloidogenic evolvability in oligodendropathies; Multiple Sclerosis and Multiple System Atrophy

Although multiple sclerosis (MS) and multiple system atrophy (MSA) are both characterized by impaired oligodendrocytes (OLs), the aetiological relevance remains obscure. Given inherent stressors affecting OLs, the objective of the present study was to discuss the possible role of amyloidogenic evolvability (aEVO) in these conditions. Hypothetically, in aEVO, protofibrils of amyloidogenic proteins (APs), including β-synuclein and β-amyloid, might form in response to diverse stressors in parental brain. Subsequently, the AP protofibrils might be transmitted to offspring via germ cells in a prion-like fashion. By virtue of the stress information conferred by protofibrillar APs, the OLs in offspring's brain might be more resilient to forthcoming stressors, perhaps reducing MS risk. aEVO could be comparable to a gene for the inheritance of acquired characteristics. On the contrary, during ageing, MSA risk is increased through antagonistic pleiotropy. Consistently, the expression levels of APs are reduced in MS, but are increased in MSA compared to controls. Furthermore, β-synuclein, the non-amyloidogenic homologue of β-synuclein, might exert a buffering effect on aEVO, and abnormal β-synuclein could also increase MS and MSA disease activity. Collectively, a better understanding of the role of aEVO in the OL diseases might lead to novel interventions for such chronic degenerative conditions.

Production and characterization of a chimeric protein targeting synuclein epitopes for immunotherapy against synucleinopathies

The aggregation and spread of alpha-synuclein (αSyn) is associated with several pathogenic pathways that lead to neurodegeneration and, ultimately, to synucleinopathies development. Hence, the establishment of a safe and effective disease-modifying therapy that limits or prevents the spread of toxic αSyn aggregation could lead to positive clinical outcomes. A rational vaccine design can be focused on the selection of specific epitopes able to induce the immune response desired, for example, antibodies able to mediate the clearance of αSyn aggregates without the induction of inflammatory responses. To develop a rapid system for the evaluation of a vaccine candidate against synucleinopathies, rLTB-Syn (an antigen based on three B cell epitopes from αSyn and the B subunit of the heat-labile Escherichia coli enterotoxin [LTB] as adjuvant/carrier) was produced using recombinant E. coli (Rosetta DE3) as the expression host. The bacterial version of rLTB-Syn was produced as soluble protein at yields up to 1.72 mg/g biomass. A method for the purification of rLTB-Syn (~18 kDa) was developed based on ion exchange chromatography, reaching purity >93% with a final concentration of 82.6 μg/mL. Furthermore, the purified soluble rLTB-Syn retained GM1 binding activity, suggesting proper folding and pentameric structure. The results from this study establish a fast and effective method to obtain rLTB-Syn, making it useful in the design of novel vaccine formulations targeting synucleinopathies.

Dopaminergic regulation of inflammation and immunity in Parkinson's disease: friend or foe?

Parkinson's disease (PD) is a neurodegenerative disease affecting 7-10 million people worldwide. Currently, there is no treatment available to prevent or delay PD progression, partially due to the limited understanding of the pathological events which lead to the death of dopaminergic neurons in the substantia nigra in the brain, which is known to be the cause of PD symptoms. The current available treatments aim at compensating dopamine (DA) deficiency in the brain using its precursor levodopa, dopaminergic agonists and some indirect dopaminergic agents. The immune system is emerging as a critical player in PD. Therefore, immune-based approaches have recently been proposed to be used as potential antiparkinsonian agents. It has been well-known that dopaminergic pathways play a significant role in regulating immune responses in the brain. Although dopaminergic agents are the primary antiparkinsonian treatments, their immune regulatory effect has yet to be fully understood. The present review summarises the current available evidence of the immune regulatory effects of DA and its mimics and discusses dopaminergic agents as antiparkinsonian drugs. Based on the current understanding of their involvement in the regulation of neuroinflammation in PD, we propose that targeting immune pathways involved in PD pathology could offer a better treatment outcome for PD patients.

Peptide immunization against the C-terminal of alpha-synuclein reduces locomotor activity in mice overexpressing alpha-synuclein

Abnormal accumulation of alpha-synuclein (αSyn) in the remaining nigra dopaminergic neurons is a common neuropathological feature found in patients with Parkinson's disease (PD). Antibody-based immunotherapy has been considered a potential approach for PD treatment. This study aims to investigate the effectiveness of active immunization against αSyn in a mouse model of PD. Adult mice were immunized with or without a synthetic peptide containing the C-terminal residues of human αSyn and activation epitopes, followed by an intranigral injection of adeno-associated virus vectors for overexpressing human αSyn. Upon the peptide injection, αSyn-specific antibodies were raised, accompanied by degeneration of dopaminergic neurons and motor deficits. Furthermore, the induction of neuroinflammation was postulated by the elevation of astroglial and microglial markers in the immunized mice. Instead of lessening αSyn toxicity, this peptide vaccine caused an increase in the pathogenic species of αSyn. Our data demonstrated the potential adverse effects of active immunization to raise antibodies against the C-terminal fragment of αSyn. This drawback highlights the need for further investigation to weigh the pros and cons of immunotherapy in PD. Applying the αSyn C-terminal peptide vaccine for PD treatment should be cautiously exercised. This study provides valuable insights into the intricate interplay among immune intervention, αSyn accumulation, and neurodegeneration.

Nicotine-mediated effects in neuronal and mouse models of synucleinopathy

Introduction

Alpha-synuclein (α-Syn) aggregation, transmission, and contribution to neurotoxicity represent central mechanisms underlying Parkinson's disease. The plant alkaloid "nicotine" was reported to attenuate α-Syn aggregation in different models, but its precise mode of action remains unclear.

Methods

In this study, we investigated the effect of 2-week chronic nicotine treatment on α-Syn aggregation, neuroinflammation, neurodegeneration, and motor deficits in D-line α-Syn transgenic mice. We also established a novel humanized neuronal model of α-Syn aggregation and toxicity based on treatment of dopaminergic neurons derived from human induced pluripotent stem cells (iPSC) with α-Syn preformed fibrils (PFF) and applied this model to investigate the effects of nicotine and other compounds and their modes of action.

Results and discussion

Overall, our results showed that nicotine attenuated α-Syn-provoked neuropathology in both models. Moreover, when investigating the role of nicotinic acetylcholine receptor (nAChR) signaling in nicotine's neuroprotective effects in iPSC-derived dopaminergic neurons, we observed that while α4-specific antagonists reduced the nicotine-induced calcium response, α4 agonists (e.g., AZD1446 and anatabine) mediated similar neuroprotective responses against α-Syn PFF-provoked neurodegeneration. Our results show that nicotine attenuates α-Syn-provoked neuropathology in vivo and in a humanized neuronal model of synucleinopathy and that activation of α4β2 nicotinic receptors might mediate these neuroprotective effects.

Identification of novel immune-related biomarker and therapeutic drugs in Parkinson disease via integrated bioinformatics analysis

BACKGROUND

The present study was designed to identify immune-related biomarker and candidate drugs for Parkinson disease (PD) by weighted gene co-expression network analysis.

METHODS

Differentially expressed genes were identified in PD and healthy samples in the Gene Expression Omnibus (GEO) database. Besides, immune-related genes were obtained from the immunology database. Then, a co-expression network was constructed by the weighted gene co-expression network analysis package. Diagnostic model for PD was constructed by Lasso and multivariate Cox regression. Furthermore, differentially expressed genes (DEGs) were used to establish PPI and competing endogenous RNA (ceRNA) networks. Functional enrichment and pathway analysis were performed. Drug-hub gene interaction analysis was performed via DGIdb database.

RESULTS

PD samples and normal samples were found to have 220 upregulated genes and 216 downregulated genes in the GSE6613 dataset. The differentially expressed genes contained 50 immune-related genes, with 40 upregulated genes and 10 downregulated genes. We obtained 7 hub genes by intersecting the DEGs and candidate hub genes. As potential diagnostic markers, 2 immune-related DEGs were identified among the 7 hub genes. According to functional enrichment analysis, these DEGs were mainly enriched in immune response, inflammatory response, and cytokine-cytokine receptor interactions. Totally, we obtained 182 drug-gene interaction pairs in Drug-Gene Interaction database (DGIdb).

CONCLUSION

Our results revealed crucial genes and candidate drugs for PD patients and deepen our understanding of the molecular mechanisms involved in PD.

Reduction of brain stem pathology and transient amelioration of early cognitive symptoms in transgenic mice treated with a monoclonal antibody against α-synuclein oligomers/protofibrils

Immunotherapy against alpha-synuclein (α-syn) is a promising novel treatment strategy for Parkinson's disease (PD) and related α-synucleinopathies. We have previously shown that systemic treatment with the monoclonal oligomer/protofibril-selective antibody mAb47 targeting cytotoxic α-syn leads to reduced central nervous system levels of such species as well as an indication of reduced late-stage symptoms in aged (Thy-1)-h[A30P] α-syn transgenic mice. Here, we performed an early-onset long-term treatment study with this antibody to evaluate effects on brain pathology and behavioral outcomes in the same mouse model. Compared to the placebo group, the treatment strongly reduced phosphorylated α-syn (pS129 α-syn) pathology in the upper brain stem. Moreover, a preserved recognition memory and risk assessment behavior could be seen in antibody-treated mice at six months of age, even although these effects were no longer significant at eleven months of age. Importantly, no evidence of inflammatory responses or other potential toxic effects was seen with the treatment. Taken together, this study supports the strategy to target α-syn oligomers/protofibrils with monoclonal antibodies to counteract early symptoms and slow down the progression of PD and other α-synucleinopathies.

Role of neuroinflammation in neurodegeneration development

Studies in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and Amyotrophic lateral sclerosis, Huntington's disease, and so on, have suggested that inflammation is not only a result of neurodegeneration but also a crucial player in this process. Protein aggregates which are very common pathological phenomenon in neurodegeneration can induce neuroinflammation which further aggravates protein aggregation and neurodegeneration. Actually, inflammation even happens earlier than protein aggregation. Neuroinflammation induced by genetic variations in CNS cells or by peripheral immune cells may induce protein deposition in some susceptible population. Numerous signaling pathways and a range of CNS cells have been suggested to be involved in the pathogenesis of neurodegeneration, although they are still far from being completely understood. Due to the limited success of traditional treatment methods, blocking or enhancing inflammatory signaling pathways involved in neurodegeneration are considered to be promising strategies for the therapy of neurodegenerative diseases, and many of them have got exciting results in animal models or clinical trials. Some of them, although very few, have been approved by FDA for clinical usage. Here we comprehensively review the factors affecting neuroinflammation and the major inflammatory signaling pathways involved in the pathogenicity of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. We also summarize the current strategies, both in animal models and in the clinic, for the treatment of neurodegenerative diseases.

Salivary Biomarkers: Noninvasive Ways for Diagnosis of Parkinson's Disease

Finding reliable biomarkers has a crucial role in Parkinson's disease (PD) assessments. Saliva is a bodily fluid, which might be used as a source of biomarkers for PD. Our article has reviewed several publications on salivary proteins in PD patients and their potential as biomarkers. We find out that α-Syn's proportion in oligomeric form is higher in PD patients' saliva, which is potent to use as a biomarker for PD. The salivary concentration of DJ-1 and alpha-amylase is lower in PD patients. Also, substance P level is more moderate in PD patients. Although salivary flow rate is decreased in PD patients, high levels of heme oxygenase and acetylcholinesterase might be used as noninvasive biomarkers. Salivary miRNAs (miR-153, miR-223, miR-874, and miR-145-3p) are novel diagnostic biomarkers that should be given more attention.

Are Therapies That Target α-Synuclein Effective at Halting Parkinson's Disease Progression? A Systematic Review

There are currently no pharmacological treatments available that completely halt or reverse the progression of Parkinson's Disease (PD). Hence, there is an unmet need for neuroprotective therapies. Lewy bodies are a neuropathological hallmark of PD and contain aggregated α-synuclein (α-syn) which is thought to be neurotoxic and therefore a suitable target for therapeutic interventions. To investigate this further, a systematic review was undertaken to evaluate whether anti-α-syn therapies are effective at preventing PD progression in preclinical in vivo models of PD and via current human clinical trials. An electronic literature search was performed using MEDLINE and EMBASE (Ovid), PubMed, the Web of Science Core Collection, and Cochrane databases to collate clinical evidence that investigated the targeting of α-syn. Novel preclinical anti-α-syn therapeutics provided a significant reduction of α-syn aggregations. Biochemical and immunohistochemical analysis of rodent brain tissue demonstrated that treatments reduced α-syn-associated pathology and rescued dopaminergic neuronal loss. Some of the clinical studies did not provide endpoints since they had not yet been completed or were terminated before completion. Completed clinical trials displayed significant tolerability and efficacy at reducing α-syn in patients with PD with minimal adverse effects. Collectively, this review highlights the capacity of anti-α-syn therapies to reduce the accumulation of α-syn in both preclinical and clinical trials. Hence, there is potential and optimism to target α-syn with further clinical trials to restrict dopaminergic neuronal loss and PD progression and/or provide prophylactic protection to avoid the onset of α-syn-induced PD.

The Mechanisms of the Roles of α-Synuclein, Amyloid-β, and Tau Protein in the Lewy Body Diseases: Pathogenesis, Early Detection, and Therapeutics

Lewy body diseases (LBD) are pathologically defined as the accumulation of Lewy bodies composed of an aggregation of α-synuclein (αSyn). In LBD, not only the sole aggregation of αSyn but also the co-aggregation of amyloidogenic proteins, such as amyloid-β (Aβ) and tau, has been reported. In this review, the pathophysiology of co-aggregation of αSyn, Aβ, and tau protein and the advancement in imaging and fluid biomarkers that can detect αSyn and co-occurring Aβ and/or tau pathologies are discussed. Additionally, the αSyn-targeted disease-modifying therapies in clinical trials are summarized.

AAV-mediated expression of a new conformational anti-aggregated α-synuclein antibody prolongs survival in a genetic model of α-synucleinopathies

Prion-like transmission of pathology in α-synucleinopathies like Parkinson's disease or multiple system atrophy is increasingly recognized as one potential mechanism to address disease progression. Active and passive immunotherapies targeting insoluble, aggregated α-synuclein are already being actively explored in the clinic with mixed outcomes so far. Here, we report the identification of 306C7B3, a highly selective, aggregate-specific α-synuclein antibody with picomolar affinity devoid of binding to the monomeric, physiologic protein. 306C7B3 binding is Ser129-phosphorylation independent and shows high affinity to several different aggregated α-synuclein polymorphs, increasing the likelihood that it can also bind to the pathological seeds assumed to drive disease progression in patients. In support of this, highly selective binding to pathological aggregates in postmortem brains of MSA patients was demonstrated, with no staining in samples from other human neurodegenerative diseases. To achieve CNS exposure of 306C7B3, an adeno-associated virus (AAV) based approach driving expression of the secreted antibody within the brain of (Thy-1)-[A30P]-hα-synuclein mice was used. Widespread central transduction after intrastriatal inoculation was ensured by using the AAV2HBKO serotype, with transduction being spread to areas far away from the inoculation site. Treatment of (Thy-1)-[A30P]-hα-synuclein mice at the age of 12 months demonstrated significantly increased survival, with 306C7B3 concentration reaching 3.9 nM in the cerebrospinal fluid. These results suggest that AAV-mediated expression of 306C7B3, targeting extracellular, presumably disease-propagating aggregates of α-synuclein, has great potential as a disease-modifying therapy for α-synucleinopathies as it ensures CNS exposure of the antibody, thereby mitigating the selective permeability of the blood-brain barrier.

Parkinson's disease therapy: what lies ahead?

The worldwide prevalence of Parkinson's disease (PD) has been constantly increasing in the last decades. With rising life expectancy, a longer disease duration in PD patients is observed, further increasing the need and socioeconomic importance of adequate PD treatment. Today, PD is exclusively treated symptomatically, mainly by dopaminergic stimulation, while efforts to modify disease progression could not yet be translated to the clinics. New formulations of approved drugs and treatment options of motor fluctuations in advanced stages accompanied by telehealth monitoring have improved PD patients care. In addition, continuous improvement in the understanding of PD disease mechanisms resulted in the identification of new pharmacological targets. Applying novel trial designs, targeting of pre-symptomatic disease stages, and the acknowledgment of PD heterogeneity raise hopes to overcome past failures in the development of drugs for disease modification. In this review, we address these recent developments and venture a glimpse into the future of PD therapy in the years to come.

Single-domain antibody-based noninvasive in vivo imaging of α-synuclein or tau pathology

Intracellular deposition of α-synuclein and tau are hallmarks of synucleinopathies and tauopathies, respectively. Recently, several dye-based imaging probes with selectivity for tau aggregates have been developed, but suitable imaging biomarkers for synucleinopathies are still unavailable. Detection of both of these aggregates early in the disease process may allow for prophylactic therapies before functional impairments have manifested, highlighting the importance of developing specific imaging probes for these lesions. In contrast to the β sheet dyes, single-domain antibodies, found in camelids and a few other species, are highly specific, and their small size allows better brain entry and distribution than whole antibodies. Here, we have developed such imaging ligands via phage display libraries derived from llamas immunized with α-synuclein and tau preparations, respectively. These probes allow noninvasive and specific in vivo imaging of α-synuclein versus tau pathology in mice, with the brain signal correlating strongly with lesion burden. These small antibody derivatives have great potential for in vivo diagnosis of these diseases.

Toll-like receptors in pathogenesis of neurodegenerative diseases and their therapeutic potential

Toll-like receptors (TLRs) are a family of pattern-recognition receptors triggered by pathogen-derived and tissue-damage-related ligands. TLRs were previously believed to only be expressed in immune cells. However, it is now confirmed that they are ubiquitously expressed in cells within the body including neurons, astrocytes, and microglia of the central nervous system (CNS). Activation of TLRs is capable of inducing immunologic and inflammatory responses to injury or infection of CNS. This response is self-limiting that usually resolves once the infection has been eradicated or the tissue damage has been repaired. However, the persistence of inflammation-inducing insults or a failure in normal resolution mechanisms may result in overwhelming inflammation which may induce neurodegeneration. This implies that TLRs may play a role in mediating the link between inflammation and neurodegenerative diseases namely Alzheimer's disease, Parkinson's disease, Huntington's disease, stroke, and amyotrophic lateral sclerosis. So, new therapeutic approaches that specifically target TLRs may be developed by better understanding TLR expression mechanisms in the CNS and their connections to particular neurodegenerative disorders. Therefore, this review paper discussed the role of TLRs in neurodegenerative diseases.

Alpha Synuclein: Neurodegeneration and Inflammation

Alpha-Synuclein (α-Syn) is one of the most important molecules involved in the pathogenesis of Parkinson's disease and related disorders, synucleinopathies, but also in several other neurodegenerative disorders with a more elusive role. This review analyzes the activities of α-Syn, in different conformational states, monomeric, oligomeric and fibrils, in relation to neuronal dysfunction. The neuronal damage induced by α-Syn in various conformers will be analyzed in relation to its capacity to spread the intracellular aggregation seeds with a prion-like mechanism. In view of the prominent role of inflammation in virtually all neurodegenerative disorders, the activity of α-Syn will also be illustrated considering its influence on glial reactivity. We and others have described the interaction between general inflammation and cerebral dysfunctional activity of α-Syn. Differences in microglia and astrocyte activation have also been observed when in vivo the presence of α-Syn oligomers has been combined with a lasting peripheral inflammatory effect. The reactivity of microglia was amplified, while astrocytes were damaged by the double stimulus, opening new perspectives for the control of inflammation in synucleinopathies. Starting from our studies in experimental models, we extended the perspective to find useful pointers to orient future research and potential therapeutic strategies in neurodegenerative disorders.

Disease mechanisms as subtypes: Immune dysfunction in Parkinson's disease

In recent years, the contraposition between inflammatory and neurodegenerative processes has been increasingly challenged. Inflammation has been emphasized as a key player in the onset and progression of Parkinson disease (PD) and other neurodegenerative disorders. The strongest indicators of the involvement of the immune system derived from evidence of microglial activation, profound imbalance in phenotype and composition of peripheral immune cells, and impaired humoral immune responses. Moreover, peripheral inflammatory mechanisms (e.g., involving the gut-brain axis) and immunogenetic factors are likely to be implicated. Even though several lines of preclinical and clinical studies are supporting and defining the complex relationship between the immune system and PD, the exact mechanisms are currently unknown. Similarly, the temporal and causal connections between innate and adaptive immune responses and neurodegeneration are unsettled, challenging our ambition to define an integrated and holistic model of the disease. Despite these difficulties, current evidence is providing the unique opportunity to develop immune-targeted approaches for PD, thus enriching our therapeutic armamentarium. This chapter aims to provide an extensive overview of past and present studies that explored the implication of the immune system in neurodegeneration, thus paving the road for the concept of disease modification in PD.

Translational molecular imaging and drug development in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder that primarily affects elderly people and constitutes a major source of disability worldwide. Notably, the neuropathological hallmarks of PD include nigrostriatal loss and the formation of intracellular inclusion bodies containing misfolded α-synuclein protein aggregates. Cardinal motor symptoms, which include tremor, rigidity and bradykinesia, can effectively be managed with dopaminergic therapy for years following symptom onset. Nonetheless, patients ultimately develop symptoms that no longer fully respond to dopaminergic treatment. Attempts to discover disease-modifying agents have increasingly been supported by translational molecular imaging concepts, targeting the most prominent pathological hallmark of PD, α-synuclein accumulation, as well as other molecular pathways that contribute to the pathophysiology of PD. Indeed, molecular imaging modalities such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) can be leveraged to study parkinsonism not only in animal models but also in living patients. For instance, mitochondrial dysfunction can be assessed with probes that target the mitochondrial complex I (MC-I), while nigrostriatal degeneration is typically evaluated with probes designed to non-invasively quantify dopaminergic nerve loss. In addition to dopaminergic imaging, serotonin transporter and N-methyl-D-aspartate (NMDA) receptor probes are increasingly used as research tools to better understand the complexity of neurotransmitter dysregulation in PD. Non-invasive quantification of neuroinflammatory processes is mainly conducted by targeting the translocator protein 18 kDa (TSPO) on activated microglia using established imaging agents. Despite the overwhelming involvement of the brain and brainstem, the pathophysiology of PD is not restricted to the central nervous system (CNS). In fact, PD also affects various peripheral organs such as the heart and gastrointestinal tract - primarily via autonomic dysfunction. As such, research into peripheral biomarkers has taken advantage of cardiac autonomic denervation in PD, allowing the differential diagnosis between PD and multiple system atrophy with probes that visualize sympathetic nerve terminals in the myocardium. Further, α-synuclein has recently gained attention as a potential peripheral biomarker in PD. This review discusses breakthrough discoveries that have led to the contemporary molecular concepts of PD pathophysiology and how they can be harnessed to develop effective imaging probes and therapeutic agents. Further, we will shed light on potential future trends, thereby focusing on potential novel diagnostic tracers and disease-modifying therapeutic interventions.

Anti-α-synuclein c-terminal antibodies block PFF uptake and accumulation of phospho-synuclein in preclinical models of Parkinson's disease

Parkinson's disease (PD), a neurodegenerative disease affecting dopaminergic (DA) neurons, is characterized by decline of motor function and cognition. Dopaminergic cell loss is associated with accumulation of toxic alpha synuclein aggregates. As DA neuron death occurs late in the disease, therapeutics that block the spread of alpha synuclein may offer functional benefit and delay disease progression. To test this hypothesis, we generated antibodies to the C terminal region of synuclein with high nanomolar affinity and characterized them in in vitro and in vivo models of spread. Interestingly, we found that only antibodies with high affinity to the distal most portion of the C-terminus robustly reduced uptake of alpha synuclein preformed fibrils (PFF) and accumulation of phospho (S129) alpha synuclein in cell culture. Additionally, the antibody treatment blocked the spread of phospho (S129) alpha synuclein associated-pathology in a mouse model of synucleinopathy. Blockade of neuronal PFF uptake by different antibodies was more predictive of in vivo activity than their binding potency to monomeric or oligomeric forms of alpha synuclein. These data demonstrate that antibodies directed to the C-terminus of the alpha synuclein have differential effects on target engagement and efficacy. Furthermore, our data provides additional support for the development of alpha synuclein antibodies as a therapeutic strategy for PD patients.

Novel naturally occurring autoantibodies attenuate α-synuclein pathology in a mouse model of Parkinson's disease

AIMS

Accumulation and propagation of pathological α-synuclein (α-Syn) are the major contributing factors to the pathogenesis of Parkinson's disease (PD). Therapy to halt the spreading of α-Syn pathology needs to be established.

METHODS

After phage display and affinity maturation, human-derived anti-α-Syn autoantibodies were selected and applied to biochemical, cellular and animal models of PD.

RESULTS

The novel naturally occurring anti-α-Syn autoantibodies (α-Syn-nAbs), P21 and P22, selectively bind α-Syn preformed fibrils (PFFs), recognise Lewy bodies (LBs) and Lewy neurites (LNs) in human PD brains, block α-Syn fibrillization and inhibit the seeding of α-Syn PFFs. Moreover, systematic administration of P21 and P22 attenuates α-Syn pathology, degeneration of the nigrostriatal pathway and motor deficits in mice injected with α-Syn PFFs.

CONCLUSIONS

P21 and P22 attenuate α-synuclein pathology and are promising candidates for PD treatment.

Development of an Antigen Detection Kit Capable of Discriminating the Omicron Mutants of SARS-CoV-2

INTRODUCTION

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread around the world, caused millions of deaths and a severe illness which poses a serious threat to human health.

OBJECTIVE

To develop an antigen detection kit that can identify Omicron novel coronavirus mutants.

METHODS

BALB/c mice were immunized with the nucleocapsid protein of SARS-CoV-2 Omicron mutant treated with β-propiolactone. After fusion of myeloma cells with immune cells, Elisa was used to screen the cell lines capable of producing monoclonal antibodies. The detection kit was prepared by colloidal gold immunochromatography. Finally, the sensitivity, specificity and anti-interference of the kit were evaluated by simulating positive samples.

RESULTS

The sensitivity of the SARS-CoV-2 antigen detection kit can reach 62.5 TCID₅₀/mL, and it has good inclusiveness for different SARS-CoV-2 strains. The kit had no cross-reaction with common respiratory pathogens, and its sensitivity was still not affected under the action of different concentrations of interferences, indicating that it had good specificity and stability.

CONCLUSION

In this study, monoclonal antibodies with high specificity to the N protein of the Omicron mutant strain were obtained by monoclonal antibody screening technology. Colloidal gold immunochromatography technology was used to prepare an antigen detection kit with high sensitivity to detect and identify the mutant Omicron strain.

Evaluation of an Adoptive Cellular Therapy-Based Vaccine in a Transgenic Mouse Model of α-synucleinopathy

Aggregated α-synuclein, a major constituent of Lewy bodies plays a crucial role in the pathogenesis of α-synucleinopathies (SPs) such as Parkinson's disease (PD). PD is affected by the innate and adaptive arms of the immune system, and recently both active and passive immunotherapies targeted against α-synuclein are being trialed as potential novel treatment strategies. Specifically, dendritic cell-based vaccines have shown to be an effective treatment for SPs in animal models. Here, we report on the development of adoptive cellular therapy (ACT) for SP and demonstrate that adoptive transfer of pre-activated T-cells generated from immunized mice can improve survival and behavior, reduce brain microstructural impairment via magnetic resonance imaging (MRI), and decrease α-synuclein pathology burden in a peripherally induced preclinical SP model (M83) when administered prior to disease onset. This study provides preclinical evidence for ACT as a potential immunotherapy for LBD, PD and other related SPs, and future work will provide necessary understanding of the mechanisms of its action.

Antiparkinsonian Agents in Investigational Polymeric Micro- and Nano-Systems

Parkinson's disease (PD) is a devastating neurodegenerative disease characterized by progressive destruction of dopaminergic tissue in the central nervous system (CNS). To date, there is no cure for the disease, with current pharmacological treatments aimed at controlling the symptoms. Therefore, there is an unmet need for new treatments for PD. In addition to new therapeutic options, there exists the need for improved efficiency of the existing ones, as many agents have difficulties in crossing the blood-brain barrier (BBB) to achieve therapeutic levels in the CNS or exhibit inappropriate pharmacokinetic profiles, thereby limiting their clinical benefits. To overcome these limitations, an interesting approach is the use of drug delivery systems, such as polymeric microparticles (MPs) and nanoparticles (NPs) that allow for the controlled release of the active ingredients targeting to the desired site of action, increasing the bioavailability and efficacy of treatments, as well as reducing the number of administrations and adverse effects. Here we review the polymeric micro- and nano-systems under investigation as potential new therapies for PD.

Establishment of the Carrot-Made LTB-Syn Antigen Cell Line in Shake Flask and Airlift Bioreactor Cultures

Carrot (Daucus carota) cells have been used to effectively manufacture recombinant biopharmaceuticals such as cytokines, vaccines, and antibodies. We generated the carrot cell line Z4, genetically modified to produce the LTB-Syn antigen, which is a fusion protein proposed for immunotherapy against synucleinopathies. In this work, the Z4 cell suspension line was cultivated to produce the LTB-Syn protein in a 250 mL shake flask and 2 L airlift bioreactor cultures grown for 45 and 30 days, respectively. Maximum biomass was obtained on day 15 in both the airlift bioreactor (35.00 ± 0.04 g/L DW) and shake flasks (17.00 ± 0.04 g/L DW). In the bioreactor, the highest LTB-Syn protein yield (1.52 ± 0.03 µg/g FW) was obtained on day 15; while the same occurred on day 18 for shake flasks (0.92 ± 0.02 µg/g FW). LTB-Syn protein levels were analyzed by GM1-ELISA and western blot. PCR analysis confirmed the presence of the transgene in the Z4 line. The obtained data demonstrate that the carrot Z4 cell suspension line grown in airlift bioreactors shows promise for a scale-up cultivation producing an oral LTB-Syn antigen.

Neuroinflammation and Parkinson's Disease-From Neurodegeneration to Therapeutic Opportunities

Parkinson’s disease (PD) is the second most prevalent neurodegenerative disorder worldwide. Clinically, it is characterized by a progressive degeneration of dopaminergic neurons (DAn), resulting in severe motor complications. Preclinical and clinical studies have indicated that neuroinflammation can play a role in PD pathophysiology, being associated with its onset and progression. Nevertheless, several key points concerning the neuroinflammatory process in PD remain to be answered. Bearing this in mind, in the present review, we cover the impact of neuroinflammation on PD by exploring the role of inflammatory cells (i.e., microglia and astrocytes) and the interconnections between the brain and the peripheral system. Furthermore, we discuss both the innate and adaptive immune responses regarding PD pathology and explore the gut–brain axis communication and its influence on the progression of the disease.

Alpha-synuclein Immunization Strategies for Synucleinopathies in Clinical Studies: A Biological Perspective

The therapeutic strategies currently available for neurodegenerative diseases such as Parkinson's disease target only the symptoms of the disease. Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy can be summarized as synucleinopathies, as they are all characterized by the aggregation and accumulation of alpha-synuclein (α-syn) in the brain. Targeting α-syn by its formation and progression opens a new and promising disease-modifying therapeutic strategy. Thus, several distinct immunotherapeutic approaches are currently being evaluated in clinical trials. The objective of this article is to review, from a biological perspective, the most important properties of these passive and active immunotherapies to point out their relevance and suitability for the treatment of synucleinopathies.

A Novel C-Type Lectin Receptor-Targeted α-Synuclein-Based Parkinson Vaccine Induces Potent Immune Responses and Therapeutic Efficacy in Mice

The progressive accumulation of misfolded α-synuclein (α-syn) in the brain is widely considered to be causal for the debilitating clinical manifestations of synucleinopathies including, most notably, Parkinson's disease (PD). Immunotherapies, both active and passive, against α-syn have been developed and are promising novel treatment strategies for such disorders. To increase the potency and specificity of PD vaccination, we created the 'Win the Skin Immune System Trick' (WISIT) vaccine platform designed to target skin-resident dendritic cells, inducing superior B and T cell responses. Of the six tested WISIT candidates, all elicited higher immune responses compared to conventional, aluminum adjuvanted peptide-carrier conjugate PD vaccines, in BALB/c mice. WISIT-induced antibodies displayed higher selectivity for α-syn aggregates than those induced by conventional vaccines. Additionally, antibodies induced by two selected candidates were shown to inhibit α-syn aggregation in a dose-dependent manner in vitro. To determine if α-syn fibril formation could also be inhibited in vivo, WISIT candidate type 1 (CW-type 1) was tested in an established synucleinopathy seeding model and demonstrated reduced propagation of synucleinopathy in vivo. Our studies provide proof-of-concept for the efficacy of the WISIT vaccine technology platform and support further preclinical and clinical development of this vaccine candidate.

Trial of Prasinezumab in Early-Stage Parkinson's Disease

BACKGROUND

Aggregated α-synuclein plays an important role in the pathogenesis of Parkinson's disease. The monoclonal antibody prasinezumab, directed at aggregated α-synuclein, is being studied for its effect on Parkinson's disease.

METHODS

In this phase 2 trial, we randomly assigned participants with early-stage Parkinson's disease in a 1:1:1 ratio to receive intravenous placebo or prasinezumab at a dose of 1500 mg or 4500 mg every 4 weeks for 52 weeks. The primary end point was the change from baseline to week 52 in the sum of scores on parts I, II, and III of the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS; range, 0 to 236, with higher scores indicating greater impairment). Secondary end points included the dopamine transporter levels in the putamen of the hemisphere ipsilateral to the clinically more affected side of the body, as measured by ¹²³I-ioflupane single-photon-emission computed tomography (SPECT).

RESULTS

A total of 316 participants were enrolled; 105 were assigned to receive placebo, 105 to receive 1500 mg of prasinezumab, and 106 to receive 4500 mg of prasinezumab. The baseline mean MDS-UPDRS scores were 32.0 in the placebo group, 31.5 in the 1500-mg group, and 30.8 in the 4500-mg group, and mean (±SE) changes from baseline to 52 weeks were 9.4±1.2 in the placebo group, 7.4±1.2 in the 1500-mg group (difference vs. placebo, -2.0; 80% confidence interval [CI], -4.2 to 0.2; P = 0.24), and 8.8±1.2 in the 4500-mg group (difference vs. placebo, -0.6; 80% CI, -2.8 to 1.6; P = 0.72). There was no substantial difference between the active-treatment groups and the placebo group in dopamine transporter levels on SPECT. The results for most clinical secondary end points were similar in the active-treatment groups and the placebo group. Serious adverse events occurred in 6.7% of the participants in the 1500-mg group and in 7.5% of those in the 4500-mg group; infusion reactions occurred in 19.0% and 34.0%, respectively.

CONCLUSIONS

Prasinezumab therapy had no meaningful effect on global or imaging measures of Parkinson's disease progression as compared with placebo and was associated with infusion reactions. (Funded by F. Hoffmann-La Roche and Prothena Biosciences; PASADENA ClinicalTrials.gov number, NCT03100149.).

Diagnostic and therapeutic agents that target alpha-synuclein in Parkinson's disease

The development of disease-modifying drugs and differential diagnostic agents is an urgent medical need in Parkinson’s disease. Despite the complex pathophysiological pathway, the misfolding of alpha-synuclein has been identified as a putative biomarker for detecting the onset and progression of the neurodegeneration associated with Parkinson’s disease. Identifying the most appropriate alpha-synuclein-based diagnostic modality with clinical translation will revolutionize the diagnosis of Parkinson’s. Likewise, molecules that target alpha-synuclein could alter the disease pathway that leads to Parkinson’s and may serve as first-in class therapeutics compared to existing treatment options such as levodopa and dopamine agonist that do not necessarily modify the disease pathway. Notwithstanding the promising benefits that alpha-synuclein presents to therapeutics and diagnostics development for Parkinson’s disease, finding ways to address potential challenges such as inadequate preclinical models, safety and efficacy will be paramount to achieving clinical translation. In this comprehensive review paper, we described the role of alpha-synuclein in the pathogenesis of Parkinson’s disease, as well as how its structure and function relationship delineate disease onset and progression. We further discussed different alpha-synuclein-based diagnostic modalities including biomolecular assays and molecular imaging. Finally, we presented current small molecules and biologics that are being developed as disease-modifying drugs or positron emission tomography imaging probes for Parkinson’s disease.

Reduction of αSYN Pathology in a Mouse Model of PD Using a Brain-Penetrating Bispecific Antibody

Immunotherapy targeting aggregated alpha-synuclein (αSYN) is a promising approach for the treatment of Parkinson’s disease. However, brain penetration of antibodies is hampered by their large size. Here, RmAbSynO2-scFv8D3, a modified bispecific antibody that targets aggregated αSYN and binds to the transferrin receptor for facilitated brain uptake, was investigated to treat αSYN pathology in transgenic mice. Ex vivo analyses of the blood and brain distribution of RmAbSynO2-scFv8D3 and the unmodified variant RmAbSynO2, as well as in vivo analyses with microdialysis and PET, confirmed fast and efficient brain uptake of the bispecific format. In addition, intravenous administration was shown to be superior to intraperitoneal injections in terms of brain uptake and distribution. Next, aged female αSYN transgenic mice (L61) were administered either RmAbSynO2-scFv8D3, RmAbSynO2, or PBS intravenously three times over five days. Levels of TBS-T soluble aggregated αSYN in the brain following treatment with RmAbSynO2-scFv8D3 were decreased in the cortex and midbrain compared to RmAbSynO2 or PBS controls. Taken together, our results indicate that facilitated brain uptake of αSYN antibodies can improve treatment of αSYN pathology.

Gene Therapy in Amyotrophic Lateral Sclerosis

Since the discovery of Cu/Zn superoxide dismutase (SOD1) gene mutation, in 1993, as the first genetic abnormality in amyotrophic lateral sclerosis (ALS), over 50 genes have been identified as either cause or modifier in ALS and ALS/frontotemporal dementia (FTD) spectrum disease. Mutations in C9orf72, SOD1, TAR DNA binding protein 43 (TARDBP), and fused in sarcoma (FUS) genes are the four most common ones. During the last three decades, tremendous effort has been made worldwide to reveal biological pathways underlying the pathogenesis of these gene mutations in ALS/FTD. Accordingly, targeting etiologic genes (i.e., gene therapies) to suppress their toxic effects have been investigated widely. It includes four major strategies: (i) removal or inhibition of abnormal transcribed RNA using microRNA or antisense oligonucleotides (ASOs), (ii) degradation of abnormal mRNA using RNA interference (RNAi), (iii) decrease or inhibition of mutant proteins (e.g., using antibodies against misfolded proteins), and (iv) DNA genome editing with methods such as clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (CRISPR/Cas). The promising results of these studies have led to the application of some of these strategies into ALS clinical trials, especially for C9orf72 and SOD1. In this paper, we will overview advances in gene therapy in ALS/FTD, focusing on C9orf72, SOD1, TARDBP, and FUS genes.

Targeting tau only extracellularly is likely to be less efficacious than targeting it both intra- and extracellularly

Aggregation of the tau protein is thought to be responsible for the neurodegeneration and subsequent functional impairments in diseases that are collectively named tauopathies. Alzheimer's disease is the most common tauopathy, but the group consists of over 20 different diseases, many of which have tau pathology as their primary feature. The development of tau therapies has mainly focused on preventing the formation of and/or clearing these aggregates. Of these, immunotherapies that aim to either elicit endogenous tau antibodies or deliver exogenous ones are the most common approach in clinical trials. While their mechanism of action can involve several pathways, both extra- and intracellular, pharmaceutical companies have primarily focused on antibody-mediated clearance of extracellular tau. As we have pointed out over the years, this is rather surprising because it is well known that most of pathological tau protein is found intracellularly. It has been repeatedly shown by several groups over the past decades that antibodies can enter neurons and that their cellular uptake can be enhanced by various means, particularly by altering their charge. Here, we will briefly describe the potential extra- and intracellular mechanisms involved in antibody-mediated clearance of tau pathology, discuss these in the context of recent failures of some of the tau antibody trials, and finally provide a brief overview of how the intracellular efficacy of tau antibodies can potentially be further improved by certain modifications that aim to enhance tau clearance via specific intracellular degradation pathways.

Targeting alpha-synuclein or tau for treating neurodegenerative movement disorders

The two commonest groups of neurodegenerative disorders causing movement disorders are synucleinopathies and tauopathies. These disorders are characterised by the accumulation of abnormally misfolded forms of α-synuclein and tau proteins. Our current understanding of their pathogenesis suggests that extracellular forms of these proteins are of major relevance to the mechanism of pathology propagation throughout the brain and disease progression. The most novel approaches to find disease-modifying therapies aim to reduce or block these forms of tau and α-synuclein. This article reviews therapeutic strategies targeting α-synuclein and tau protein which have entered clinical development.

Alpha-Synuclein Targeting Therapeutics for Parkinson's Disease and Related Synucleinopathies

α-Synuclein (asyn) is a key pathogenetic factor in a group of neurodegenerative diseases generically known as synucleinopathies, including Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). Although the initial triggers of pathology and progression are unclear, multiple lines of evidence support therapeutic targeting of asyn in order to limit its prion-like misfolding. Here, we review recent pre-clinical and clinical work that offers promising treatment strategies to sequester, degrade, or silence asyn expression as a means to reduce the levels of seed or substrate. These diverse approaches include removal of aggregated asyn with passive or active immunization or by expression of vectorized antibodies, modulating kinetics of misfolding with small molecule anti-aggregants, lowering asyn gene expression by antisense oligonucleotides or inhibitory RNA, and pharmacological activation of asyn degradation pathways. We also discuss recent technological advances in combining low intensity focused ultrasound with intravenous microbubbles to transiently increase blood-brain barrier permeability for improved brain delivery and target engagement of these large molecule anti-asyn biologics.

Autoantibodies targeting neuronal proteins as biomarkers for neurodegenerative diseases

Neurodegenerative diseases (NDDs) are associated with the accumulation of a range of misfolded proteins across the central nervous system and related autoimmune responses, including the generation of antibodies and the activation of immune cells. Both innate and adaptive immunity become mobilized, leading to cellular and humoral effects. The role of humoral immunity in disease onset and progression remains to be elucidated with rising evidence suggestive of positive (protection, repair) and negative (injury, toxicity) outcomes. In this study, we review advances in research of neuron-targeting autoantibodies in the most prevalent NDDs. We discuss their biological origin, molecular diversity and changes in the course of diseases, consider their relevance to the initiation and progression of pathology as well as diagnostic and prognostic significance. It is suggested that the emerging autoimmune aspects of NDDs not only could facilitate the early detection but also might help to elucidate previously unknown facets of pathobiology with relevance to the development of precision medicine.

Propagation of tau and α-synuclein in the brain: therapeutic potential of the glymphatic system

Many neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease, are characterised by the accumulation of misfolded protein deposits in the brain, leading to a progressive destabilisation of the neuronal network and neuronal death. Among the proteins that can abnormally accumulate are tau and α-synuclein, which can propagate in a prion-like manner and which upon aggregation, represent the most common intracellular proteinaceous lesions associated with neurodegeneration. For years it was thought that these intracellular proteins and their accumulation had no immediate relationship with extracellular homeostasis pathways such as the glymphatic clearance system; however, mounting evidence has now suggested that this is not the case. The involvement of the glymphatic system in neurodegenerative disease is yet to be fully defined; however, it is becoming increasingly clear that this pathway contributes to parenchymal solute clearance. Importantly, recent data show that proteins prone to intracellular accumulation are subject to glymphatic clearance, suggesting that this system plays a key role in many neurological disorders. In this review, we provide a background on the biology of tau and α-synuclein and discuss the latest findings on the cell-to-cell propagation mechanisms of these proteins. Importantly, we discuss recent data demonstrating that manipulation of the glymphatic system may have the potential to alleviate and reduce pathogenic accumulation of propagation-prone intracellular cytotoxic proteins. Furthermore, we will allude to the latest potential therapeutic opportunities targeting the glymphatic system that might have an impact as disease modifiers in neurodegenerative diseases.

Alpha-Synuclein-Specific Naturally Occurring Antibodies Inhibit Aggregation In Vitro and In Vivo

Parkinson’s disease (PD) is associated with motor and non-motor symptoms and characterized by aggregates of alpha-synuclein (αSyn). Naturally occurring antibodies (nAbs) are part of the innate immune system, produced without prior contact to their specific antigen, and polyreactive. The abundance of nAbs against αSyn is altered in patients with PD. In this work, we biophysically characterized nAbs against αSyn (nAbs-αSyn) and determined their biological effects. nAbs-αSyn were isolated from commercial intravenous immunoglobulins using column affinity purification. Biophysical properties were characterized using a battery of established in vitro assays. Biological effects were characterized in HEK293T cells transiently transfected with fluorescently tagged αSyn. Specific binding of nAbs-αSyn to monomeric αSyn was demonstrated by Dot blot, ELISA, and Surface Plasmon Resonance. nAbs-αSyn did not affect viability of HEK293T cells as reported by Cell Titer Blue and LDH Assays. nAbs-αSyn inhibited fibrillation of αSyn reported by the Thioflavin T aggregation assay. Altered fibril formation was confirmed with atomic force microscopy. In cells transfected with EGFP-tagged αSyn we observed reduced formation of aggresomes, perinuclear accumulations of αSyn aggregates. The results demonstrate that serum of healthy individuals contains nAbs that specifically bind αSyn and inhibit aggregation of αSyn in vitro. The addition of nAbs-αSyn to cultured cells affects intracellular αSyn aggregates. These findings help understanding the role of the innate immune systems for the pathogenesis of PD and suggest that systemic αSyn binding agents could potentially affect neuronal αSyn pathology.

Passive Immunization in Alpha-Synuclein Preclinical Animal Models

Alpha-synucleinopathies include Parkinson’s disease, dementia with Lewy bodies, pure autonomic failure and multiple system atrophy. These are all progressive neurodegenerative diseases that are characterized by pathological misfolding and accumulation of the protein alpha-synuclein (αsyn) in neurons, axons or glial cells in the brain, but also in other organs. The abnormal accumulation and propagation of pathogenic αsyn across the autonomic connectome is associated with progressive loss of neurons in the brain and peripheral organs, resulting in motor and non-motor symptoms. To date, no cure is available for synucleinopathies, and therapy is limited to symptomatic treatment of motor and non-motor symptoms upon diagnosis. Recent advances using passive immunization that target different αsyn structures show great potential to block disease progression in rodent studies of synucleinopathies. However, passive immunotherapy in clinical trials has been proven safe but less effective than in preclinical conditions. Here we review current achievements of passive immunotherapy in animal models of synucleinopathies. Furthermore, we propose new research strategies to increase translational outcome in patient studies, (1) by using antibodies against immature conformations of pathogenic αsyn (monomers, post-translationally modified monomers, oligomers and protofibrils) and (2) by focusing treatment on body-first synucleinopathies where damage in the brain is still limited and effective immunization could potentially stop disease progression by blocking the spread of pathogenic αsyn from peripheral organs to the brain.

Efficacy and immunogenicity of MultiTEP-based DNA vaccines targeting human α-synuclein: prelude for IND enabling studies

Accumulation of misfolded proteins such as amyloid-β (Aβ), tau, and α-synuclein (α-Syn) in the brain leads to synaptic dysfunction, neuronal damage, and the onset of relevant neurodegenerative disorder/s. Dementia with Lewy bodies (DLB) and Parkinson’s disease (PD) are characterized by the aberrant accumulation of α-Syn intracytoplasmic Lewy body inclusions and dystrophic Lewy neurites resulting in neurodegeneration associated with inflammation. Cell to cell propagation of α-Syn aggregates is implicated in the progression of PD/DLB, and high concentrations of anti-α-Syn antibodies could inhibit/reduce the spreading of this pathological molecule in the brain. To ensure sufficient therapeutic concentrations of anti-α-Syn antibodies in the periphery and CNS, we developed four α-Syn DNA vaccines based on the universal MultiTEP platform technology designed especially for the elderly with immunosenescence. Here, we are reporting on the efficacy and immunogenicity of these vaccines targeting three B-cell epitopes of hα-Syn aa85–99 (PV-1947D), aa109–126 (PV-1948D), aa126–140 (PV-1949D) separately or simultaneously (PV-1950D) in a mouse model of synucleinopathies mimicking PD/DLB. All vaccines induced high titers of antibodies specific to hα-Syn that significantly reduced PD/DLB-like pathology in hα-Syn D line mice. The most significant reduction of the total and protein kinase resistant hα-Syn, as well as neurodegeneration, were observed in various brain regions of mice vaccinated with PV-1949D and PV-1950D in a sex-dependent manner. Based on these preclinical data, we selected the PV-1950D vaccine for future IND enabling preclinical studies and clinical development.

Strong Predictive Algorithm of Pathogenesis-Based Biomarkers Improves Parkinson's Disease Diagnosis

Easily accessible and accurate biomarkers can aid Parkinson's disease diagnosis. We investigated whether combining plasma levels of α-synuclein, anti-α-synuclein, and/or their ratios to amyloid beta-40 correlated with clinical diagnosis. The inclusion of amyloid beta-40 (Aβ40) is novel. Plasma levels of biomarkers were quantified with ELISA. Using receiver operating characteristic (ROC) curve analysis, levels of α-synuclein, anti-α-synuclein, and their ratios with Aβ40 were analyzed in an initial training set of cases and controls. Promising biomarkers were then used to build a diagnostic algorithm. Verification of the results of biomarkers and the algorithm was performed in an independent set. The training set consisted of 50 cases (age 65.2±9.3, range 44-83, female:male=21:29) with 50 age- and gender-matched controls (67.1±10.0, range 45-96 years; female:male=21:29). ROC curve analysis yielded the following area under the curve results: anti-α-synuclein=0.835, α-synuclein=0.738, anti-α-synuclein/Aβ40=0.737, and α-synuclein/Aβ40=0.663. A 2-step diagnostic algorithm was built: either α-synuclein or anti-α-synuclein was ≥2 times the means of controls (step-1), resulting in 74% sensitivity; and adding α-synuclein/Aβ40 or anti-α-synuclein/Aβ40 (step-2) yielded better sensitivity (82%) while using step-2 alone yielded good specificity in controls (98%). The results were verified in an independent sample of 46 cases and 126 controls, with sensitivity reaching 91.3% and specificity 90.5%. The algorithm was equally sensitive in Parkinson's disease of ≤5-year duration with 92.6% correctly identified in the training set and 90% in the verification set. With two independent samples totaling 272 subjects, our study showed that combination of biomarkers of α-synuclein, anti-α-synuclein, and their ratios to Aβ40 showed promising sensitivity and specificity.