Evaluation of an α synuclein sensitized dendritic cell based vaccine in a transgenic mouse model of Parkinson disease

Dendritic cells in Parkinson's disease: Regulatory role and therapeutic potential

Parkinson's Disease (PD) is a debilitating neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons and the presence of Lewy bodies. While the traditional focus has been on neuronal and glial cell dysfunction, recent research has shifted towards understanding the role of the immune system, particularly dendritic cells (DCs), in PD pathogenesis. As pivotal antigen-presenting cells, DCs are traditionally recognized for initiating and regulating immune responses. In PD, DCs contribute to disease progression through the presentation of α-synuclein to T cells, leading to an adaptive immune response against neuronal elements. This review explores the emerging role of DCs in PD, highlighting their potential involvement in antigen presentation and T cell immune response modulation. Understanding the multifaceted functions of DCs could reveal novel insights into PD pathogenesis and open new avenues for therapeutic strategies, potentially altering the course of this devastating disease.

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.

Immunotherapy: An emerging treatment option for neurodegenerative diseases

Accumulation of misfolded proteins and protein aggregates leading to degeneration of neurons is a hallmark of several neurodegenerative diseases. Therapy mostly relies on symptomatic relief. Immunotherapy offers a promising approach for the development of disease-modifying routes. Such strategies have shown remarkable results in oncology, and this promise is increasingly being realized for neurodegenerative diseases in advanced preclinical and clinical studies. This review highlights cases of passive and active immunotherapies in Parkinson's and Alzheimer's diseases. The reasons for success and failure, wherever available, and strategies to cross the blood-brain barrier, are discussed. The need for conditional modulation of the immune response is also reflected on.

Inhibition of Protein Aggregation and Endoplasmic Reticulum Stress as a Targeted Therapy for α-Synucleinopathy

α-synuclein (α-syn) is an intrinsically disordered protein abundant in the central nervous system. Physiologically, the protein regulates vesicle trafficking and neurotransmitter release in the presynaptic terminals. Pathologies related to misfolding and aggregation of α-syn are referred to as α-synucleinopathies, and they constitute a frequent cause of neurodegeneration. The most common α-synucleinopathy, Parkinson's disease (PD), is caused by abnormal accumulation of α-syn in the dopaminergic neurons of the midbrain. This results in protein overload, activation of endoplasmic reticulum (ER) stress, and, ultimately, neural cell apoptosis and neurodegeneration. To date, the available treatment options for PD are only symptomatic and rely on dopamine replacement therapy or palliative surgery. As the prevalence of PD has skyrocketed in recent years, there is a pending issue for development of new disease-modifying strategies. These include anti-aggregative agents that target α-syn directly (gene therapy, small molecules and immunization), indirectly (modulators of ER stress, oxidative stress and clearance pathways) or combine both actions (natural compounds). Herein, we provide an overview on the characteristic features of the structure and pathogenic mechanisms of α-syn that could be targeted with novel molecular-based therapies.

Pathological mechanisms of neuroimmune response and multitarget disease-modifying therapies of mesenchymal stem cells in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by the degeneration of dopaminergic neurons in the substantia nigra (SN); the etiology and pathological mechanism of the disease are still unclear. Recent studies have shown that the activation of a neuroimmune response plays a key role in the development of PD. Alpha-synuclein (α-Syn), the primary pathological marker of PD, can gather in the SN and trigger a neuroinflammatory response by activating microglia which can further activate the dopaminergic neuron's neuroimmune response mediated by reactive T cells through antigen presentation. It has been shown that adaptive immunity and antigen presentation processes are involved in the process of PD and further research on the neuroimmune response mechanism may open new methods for its prevention and therapy. While current therapeutic regimens are still focused on controlling clinical symptoms, applications such as immunoregulatory strategies can delay the symptoms and the process of neurodegeneration. In this review, we summarized the progression of the neuroimmune response in PD based on recent studies and focused on the use of mesenchymal stem cell (MSC) therapy and challenges as a strategy of disease-modifying therapy with multiple targets.

Immunity orchestrates a bridge in gut-brain axis of neurodegenerative diseases

Neurodegenerative diseases, in particular for Alzheimer's disease (AD), Parkinson's disease (PD) and Multiple sclerosis (MS), are a category of diseases with progressive loss of neuronal structure or function (encompassing neuronal death) leading to neuronal dysfunction, whereas the underlying pathogenesis remains to be clarified. As the microbiological ecosystem of the intestinal microbiome serves as the second genome of the human body, it is strongly implicated as an essential element in the initiation and/or progression of neurodegenerative diseases. Nevertheless, the precise underlying principles of how the intestinal microflora impact on neurodegenerative diseases via gut-brain axis by modulating the immune function are still poorly characterized. Consequently, an overview of initiating the development of neurodegenerative diseases and the contribution of intestinal microflora on immune function is discussed in this review.

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.

Multifunctional role of natural products for the treatment of Parkinson's disease: At a glance

Natural substances originating from plants have long been used to treat neurodegenerative disorders (NDs). Parkinson's disease (PD) is a ND. The deterioration and subsequent cognitive impairments of the midbrain nigral dopaminergic neurons distinguish by this characteristic. Various pathogenic mechanisms and critical components have been reported, despite the fact that the origin is unknown, such as protein aggregation, iron buildup, mitochondrial dysfunction, neuroinflammation and oxidative stress. Anti-Parkinson drugs like dopamine (DA) agonists, levodopa, carbidopa, monoamine oxidase type B inhibitors and anticholinergics are used to replace DA in the current treatment model. Surgery is advised in cases where drug therapy is ineffective. Unfortunately, the current conventional treatments for PD have a number of harmful side effects and are expensive. As a result, new therapeutic strategies that control the mechanisms that contribute to neuronal death and dysfunction must be addressed. Natural resources have long been a useful source of possible treatments. PD can be treated with a variety of natural therapies made from medicinal herbs, fruits, and vegetables. In addition to their well-known anti-oxidative and anti-inflammatory capabilities, these natural products also play inhibitory roles in iron buildup, protein misfolding, the maintenance of proteasomal breakdown, mitochondrial homeostasis, and other neuroprotective processes. The goal of this research is to systematically characterize the currently available medications for Parkinson's and their therapeutic effects, which target diverse pathways. Overall, this analysis looks at the kinds of natural things that could be used in the future to treat PD in new ways or as supplements to existing treatments. We looked at the medicinal plants that can be used to treat PD. The use of natural remedies, especially those derived from plants, to treat PD has been on the rise. This article examines the fundamental characteristics of medicinal plants and the bioactive substances found in them that may be utilized to treat PD.

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.

Sequestration of Inflammation in Parkinson's Disease via Stem Cell Therapy

Parkinson’s disease is the second most common neurodegenerative disease. Insidious and progressive, this disorder is secondary to the gradual loss of dopaminergic signaling and worsening neuroinflammation, affecting patients’ motor capabilities. Gold standard treatment includes exogenous dopamine therapy in the form of levodopa–carbidopa, or surgical intervention with a deep brain stimulator to the subcortical basal ganglia. Unfortunately, these therapies may ironically exacerbate the already pro-inflammatory environment. An alternative approach may involve cell-based therapies. Cell-based therapies, whether endogenous or exogenous, often have anti-inflammatory properties. Alternative strategies, such as exercise and diet modifications, also appear to play a significant role in facilitating endogenous and exogenous stem cells to induce an anti-inflammatory response, and thus are of unique interest to neuroinflammatory conditions including Parkinson’s disease. Treating patients with current gold standard therapeutics and adding adjuvant stem cell therapy, alongside the aforementioned lifestyle modifications, may ideally sequester inflammation and thus halt neurodegeneration.

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.

Targeting alpha-synuclein via the immune system in Parkinson's disease: Current vaccine therapies

Parkinson's disease (PD) is the second most common neurodegenerative disorder and is defined pathologically by the abnormal accumulation of the presynaptic protein alpha-synuclein (aSyn) in the form of Lewy bodies and Lewy neurites and loss of midbrain dopaminergic neurons in the substantia nigra pars compacta. Because of aSyn's involvement in both sporadic and familial forms of PD, it has become a key target for the development of novel therapeutics. Aberrant aSyn is associated with multiple mechanisms of neuronal dysfunction and degeneration including inflammation, impaired mitochondrial function, altered protein degradation systems, and oxidative stress. Inflammation, in particular, has emerged as a potential significant contributor early in the disease making it an attractive target for disease modification and neuroprotection. Thus, immunotherapies targeting aSyn are currently being investigated in pre-clinical and clinical trials. The focus of this review is to highlight the role of aSyn in neuroinflammation and discuss the current status of aSyn-directed immunotherapies in pre-clinical and clinical trials for PD.

Parkinson Disease: Translating Insights from Molecular Mechanisms to Neuroprotection

Parkinson disease (PD) used to be considered a nongenetic condition. However, the identification of several autosomal dominant and recessive mutations linked to monogenic PD has changed this view. Clinically manifest PD is then thought to occur through a complex interplay between genetic mutations, many of which have incomplete penetrance, and environmental factors, both neuroprotective and increasing susceptibility, which variably interact to reach a threshold over which PD becomes clinically manifested. Functional studies of PD gene products have identified many cellular and molecular pathways, providing crucial insights into the nature and causes of PD. PD originates from multiple causes and a range of pathogenic processes at play, ultimately culminating in nigral dopaminergic loss and motor dysfunction. An in-depth understanding of these complex and possibly convergent pathways will pave the way for therapeutic approaches to alleviate the disease symptoms and neuroprotective strategies to prevent disease manifestations. This review is aimed at providing a comprehensive understanding of advances made in PD research based on leveraging genetic insights into the pathogenesis of PD. It further discusses novel perspectives to facilitate identification of critical molecular pathways that are central to neurodegeneration that hold the potential to develop neuroprotective and/or neurorestorative therapeutic strategies for PD. SIGNIFICANCE STATEMENT: A comprehensive review of PD pathophysiology is provided on the complex interplay of genetic and environmental factors and biologic processes that contribute to PD pathogenesis. This knowledge identifies new targets that could be leveraged into disease-modifying therapies to prevent or slow neurodegeneration in PD.

The role of immune cells in the course of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease in the central nervous system. The pathological manifestations mainly consist of α-synuclein accumulation, degeneration and death of dopaminergic neurons, and insufficient dopamine secretion. There are many pathophysiological mechanisms leading to these pathological changes. The role of autoimmunity in Parkinson's disease is one of the academic hotspots in recent years. Many types of immune cells actively participate in the pathogenesis of Parkinson's disease, such as dendritic cells, microglia, T lymphocytes, B lymphocytes and natural killer (NK) cells, which lead to abnormal immune response in Parkinson's disease patients. Therefore, this paper focuses on reviewing the research progress of immune cells in Parkinson's disease.

Modification of Glial Cell Activation through Dendritic Cell Vaccination: Promises for Treatment of Neurodegenerative Diseases

Accumulation of misfolded tau, amyloid β (Aβ), and alpha-synuclein (α-syn) proteins is the fundamental contributor to many neurodegenerative diseases, namely Parkinson's (PD) and AD. Such protein aggregations trigger activation of immune mechanisms in neuronal and glial, mainly M1-type microglia cells, leading to release of pro-inflammatory mediators, and subsequent neuronal dysfunction and apoptosis. Despite the described neurotoxic features for glial cells, recruitment of peripheral leukocytes to the brain and their conversion to neuroprotective M2-type microglia can mitigate neurodegeneration by clearing extracellular protein accumulations or residues. Based on these observations, it was speculated that Dendritic cell (DC)-based vaccination, by making use of DCs as natural adjuvants, could be used for treatment of neurodegenerative disorders. DCs potentiated by disease-specific antigens can also enhance T helper 2 (Th2)-specific immune response and by production of specific antibodies contribute to clearance of intracellular aggregations, as well as enhancing regulatory T cell response. Thus, enhancement of immune response by DC vaccine therapy can potentially augment glial polarization into the neuroprotective phenotype, enhance antibody production, and at the same time balance neuronal cells' repair, renewal, and protection. The characteristic feature of this method of treatment is to maintain the equilibrium in the immune response rather than targeting a single mediator in the disease and their application in other neurodegenerative diseases should be addressed. However, the safety of these methods should be investigated by clinical trials.

Treating Parkinson's Disease with Antibodies: Previous Studies and Future Directions

Parkinson's disease is a neurodegenerative disorder mainly characterized by the degeneration of dopaminergic neurons in the substantia nigra. Degenerating neurons contain abnormal aggregates called Lewy bodies, that are predominantly composed of the misfolded and/or mutated alpha-synuclein protein. Post-translational modifications, cellular stress, inflammation and gene mutations are thought to trigger its pathological misfolding and aggregation. With alpha-synuclein pathology being strongly associated with dopaminergic neuronal toxicity, strategies aimed to reduce its burden are expected to be beneficial in slowing disease progression. Moreover, multiple sources of evidence suggest a cell-to-cell transmission of pathological alpha-synuclein in a prion-like manner. Therefore, antibodies targeting extra- or intracellular alpha-synuclein could be efficient in limiting the aggregation and transmission. Several active and passive immunization strategies have been explored to target alpha-synuclein. Here, we summarize immunotherapeutic approaches that were tested in pre-clinical or clinical studies in the last two decades in an attempt to treat Parkinson's disease.

Targeting α-synuclein for PD Therapeutics: A Pursuit on All Fronts

Parkinson's Disease (PD) is characterized both by the loss of dopaminergic neurons in the substantia nigra and the presence of cytoplasmic inclusions called Lewy Bodies. These Lewy Bodies contain the aggregated α-synuclein (α-syn) protein, which has been shown to be able to propagate from cell to cell and throughout different regions in the brain. Due to its central role in the pathology and the lack of a curative treatment for PD, an increasing number of studies have aimed at targeting this protein for therapeutics. Here, we reviewed and discussed the many different approaches that have been studied to inhibit α-syn accumulation via direct and indirect targeting. These analyses have led to the generation of multiple clinical trials that are either completed or currently active. These clinical trials and the current preclinical studies must still face obstacles ahead, but give hope of finding a therapy for PD with time.

Immunotherapies in Huntington's disease and α-Synucleinopathies

Modulation of immune activation using immunotherapy has attracted considerable attention for many years as a potential therapeutic intervention for several inflammation-associated neurodegenerative diseases. However, the efficacy of single-target immunotherapy intervention has shown limited or no efficacy in alleviating disease burden and restoring functional capacity. Marked immune system activation and neuroinflammation are important features and prodromal signs in polyQ repeat disorders and α-synucleinopathies. This review describes the current status and future directions of immunotherapies in proteinopathy-induced neurodegeneration with emphasis on preclinical and clinical efficacies of several anti-inflammatory compounds and antibody-based therapies for the treatment of Huntington's disease and α-synucleinopathies. The review concludes with how disease modification and functional restoration could be achieved by using targeted multimodality therapy to target multiple factors.

Novel approaches to counter protein aggregation pathology in Parkinson's disease

The primary neuropathological characteristics of the Parkinsonian brain are the loss of nigral dopamine neurons and the aggregation of alpha synuclein protein. Efforts to development potentially disease-modifying treatments have largely focused on correcting these aspects of the condition. In the last decade treatments targeting protein aggregation have entered the clinical pipeline. In this chapter we provide an overview of ongoing clinical trial programs for different therapies attempting to reduce protein aggregation pathology in Parkinson's disease. We will also briefly consider various novel approaches being proposed-and being developed preclinically-to inhibit/reduce aggregated protein pathology in Parkinson's.

Peripheral Immunity, Immunoaging and Neuroinflammation in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder among elderly population, characterized by the progressive degeneration of dopaminergic neurons in the midbrain. To date, exact cause remains unknown and the mechanism of neurons death uncertain. It is typically considered as a disease of central nervous system (CNS). Nevertheless, numerous evidence has been accumulated in several past years testifying undoubtedly about the principal role of neuroinflammation in progression of PD. Neuroinflammation is mainly associated with presence of activated microglia in brain and elevated levels of cytokine levels in CNS. Nevertheless, active participation of immune system as well has been noted, such as, elevated levels of cytokine levels in blood, the presence of auto antibodies, and the infiltration of T cell in CNS. Moreover, infiltration and reactivation of those T cells could exacerbate neuroinflammation to greater neurotoxic levels. Hence, peripheral inflammation is able to prime microglia into pro-inflammatory phenotype, which can trigger stronger response in CNS further perpetuating the on-going neurodegenerative process. In the present review, the interplay between neuroinflammation and the peripheral immune response in the pathobiology of PD will be discussed. First of all, an overview of regulation of microglial activation and neuroinflammation is summarized and discussed. Afterwards, we try to collectively analyze changes that occurs in peripheral immune system of PD patients, suggesting that these peripheral immune challenges can exacerbate the process of neuroinflammation and hence the symptoms of the disease. In the end, we summarize some of proposed immunotherapies for treatment of PD.

Identifying the Pathological Domain of Alpha- Synuclein as a Therapeutic for Parkinson's Disease

Alpha-synuclein is considered the major pathological protein associated with Parkinson's disease, but there is still no effective immunotherapy which targets alpha-synuclein. In order to create a safer and more effective therapy against PD, we are targeting an epitope of alpha-synuclein rather than full-length alpha-synuclein. We have selected several antigenic domains (B-cell epitope) through antigenicity prediction, and also made several recombinant protein fragments from alpha-synuclein upon antigenicity prediction in an E. coli system. We then tested the function of each of the peptides and recombinant fragments in aggregation, their toxicity and antigenicity. We have discovered that the full-length recombinant (aa1-140) can aggregate into oligomers or even fibrils, and fragment aa15-65 can promote the aggregation of aa1-140. It is worth noting that it not only promotes whole protein aggregation, but also self-aggregates as seen by western blotting and silver staining assays. We have tested all candidates on primary neurons for their toxicity and discovered that aa15-65 is the most toxic domain compared to all other fragments. The antibody targeting this domain also showed both anti-aggregation activity and some therapeutic effect. Therefore, we believe that we have identified the most potent therapeutic domain of alpha synuclein as a therapeutic target.

Progress of immunotherapy of anti-α-synuclein in Parkinson's disease

Many neurodegenerative diseases are characterized by progressive loss of neurons and abnormal protein accumulation, including amyloid (A)β and tau in Alzheimer's disease and Lewy bodies and α-synuclein (α-syn) in Parkinson's disease (PD). Recent evidence suggests that adaptive immunity plays an important role in PD, and that anti-α-syn antibodies can be used as therapy in neurodegenerative diseases; monoclonal antibodies were shown to inhibit α-syn propagation and aggregation in PD models and patients. In this review, we summarize the different pathological states of α-syn, including gene mutations, truncation, phosphorylation, and the high molecular weight form, and describe the specific antibodies that recognize the α-syn monomer or oligomer, some of which have been tested in clinic trials. We also discuss future research directions and potential targets in PD therapy.

Vaccination strategies in tauopathies and synucleinopathies

Vaccination therapies constitute potential treatment options in neurodegenerative disorders such as Alzheimer disease or Parkinson disease. While a lot of research has been performed on vaccination against extracellular amyloid β, the focus recently shifted toward vaccination against the intracellular proteins tau and α-synuclein, with promising results in terms of protein accumulation reduction. In this review, we briefly summarize lessons to be learned from clinical vaccination trials in Alzheimer disease that target amyloid β. We then focus on tau and α-synuclein. For both proteins, we provide important data on protein immunogenicity, and put them into context with data available from both animals and human vaccination trials targeted at tau and α-synuclein. Together, we give a comprehensive overview about current clinical data, and discuss associated problems.

Targets and Mechanisms in Prevention of Parkinson's Disease through Immunomodulatory Treatments

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world; however, there is no cure for it. Current treatments only relieve some of the symptoms, without ceasing the disease, and lose efficacy with prolonged treatment. Considerable evidence shows that persistent inflammatory responses, involving T cell infiltration and glial cell activation, are common characteristics of human patients and play a crucial role in the degeneration of dopaminergic neurons. Therefore, it is important to develop therapeutic strategies that can impede or halt the disease through the modulation of the peripheral immune system by aiming at controlling the existing neuroinflammation. Most of the immunomodulatory therapies designed for the treatment of Parkinson's disease are based on vaccines using AS or antibodies against it; yet, it is of significant interest to explore other formulations that could be used as therapeutic agents. Several vaccination procedures have shown that inducing regulatory T cells in the periphery is protective in PD animal models. In this regard, the formulation glatiramer acetate (Copaxone^® ), extensively used for the treatment of multiple sclerosis, could be a suitable candidate due to its capability to increase the number and suppressor capacity of regulatory T cells. In this review, we will present some of the recent immunomodulatory therapies for PD including vaccinations with AS or glatiramoids, or both, as treatments of PD pathology.

LTB-Syn: a recombinant immunogen for the development of plant-made vaccines against synucleinopathies

A recombinant antigen targeting α-synuclein was produced in the plant cell rendering an immunogenic protein capable to induce humoral responses in mice upon oral administration. Synucleinopathies are neurodegenerative diseases characterized by the abnormal accumulation of α-synuclein (α-Syn, a 140 amino acid protein that normally plays various neurophysiologic roles) aggregates. Parkinson's disease (PD) is the synucleinopathy with the highest epidemiologic impact and although its etiology remains unknown, α-Syn aggregation during disease progression pointed out α-Syn as target in the development of immunotherapies. Herein a chimeric protein, comprising the B subunit of the enterotoxin from enterotoxigenic Escherichia coli and α-Syn epitopes, was expressed in the plant cell having the potential to induce humoral responses following oral immunization. This approach will serve as the basis for the development of oral plant-based vaccines against PD with several potential advantages such as low cost, easy scale-up during production, and easy administration.

Gene-based vaccines and immunotherapeutic strategies against neurodegenerative diseases: Potential utility and limitations

There has been a recent expansion of vaccination and immunotherapeutic strategies from controlling infectious diseases to the targeting of non-infectious conditions including neurodegenerative disorders. In addition to conventional vaccine and immunotherapeutic modalities, gene-based methods that express antigens for presentation to the immune system by either live viral vectors or non-viral naked DNA plasmids have been developed and evaluated. This mini-review/commentary summarizes the advantages and disadvantages, as well as the research findings to date, of both of these gene-based vaccination approaches in terms of how they can be targeted against appropriate antigens within the Alzheimer and Parkinson disease pathogenesis processes as well as potentially against targets in other neurodegenerative diseases. Most recently, the novel utilization of these viral vector and naked DNA gene-based technologies includes the delivery of immunoglobulin genes from established biologically active monoclonal antibodies. This modified passive immunotherapeutic strategy has recently been applied to deliver passive antibody immunotherapy against the pathologically relevant amyloid β protein in Alzheimer disease. The advantages and disadvantages of this technological application of gene-based immune interventions, as well as research findings to date are also summarized. In sum, it is suggested that further evaluation of gene based vaccines and immunotherapies against neurodegenerative diseases are warranted to determine their potential clinical utility.

Pathological and clinical aspects of alpha/beta synuclein in Parkinson's disease and related disorders

Parkinson's disease (PD) and related synucleinopathies are characterized by extensive neuronal cell loss, which is potentially triggered by α-synuclein misfolding and aggregation. Therefore it is reasonable to suggest that treatments targeting α-synuclein could reduce its levels and toxicity, rescue neuronal cells and halt the neurodegeneration process. Several approaches to decrease α-synuclein levels were employed thus far, mainly by using β-synuclein, another protein from the same family, or immunotherapies. These treatments demonstrated some positive results in preclinical studies, which may pave the road to the development of new promising disease-modifying therapies (DMTs). This approach should be further examined in preclinical and clinical settings, together with a clear process in order to advance candidates, enable the ability to define when there are target engagements and to detect what is a meaningful pharmacological response, and how it will be translated in clinical efficacy.

Myeloid Dendritic Cells are Potential Players in Human Neurodegenerative Diseases

Alzheimer’s diseases (AD) and Parkinson’s diseases (PD) are devastating neurodegenerative disturbances, wherein neuroinflammation is a chronic pathogenic process with high therapeutic potential. Major mediators of AD/PD neuroimmune processes are resident immune cells, but immune cells derived from periphery may also participate and to some extent modify neuroinflammation. Specifically, blood borne myeloid cells emerge as crucial components of AD/PD progression and susceptibility. Among these, dendritic cells (DCs) are key immune orchestrators and players of brain immune surveillance; we candidate them as potential mediators of both AD and PD and as relevant cell model for unraveling myeloid cell role in neurodegeneration. Hence, we recapitulate and discuss emerging data suggesting that blood-derived DCs play a role in experimental and human neurodegenerative diseases. In humans, in particular, DCs are modified by in vitro culture with neurodegeneration-associated pathogenic factors and dysregulated in AD patients, while the levels of DC precursors are decreased in AD and PD patients’ blood, possibly as an index of their recruitment to the brain. Overall, we emphasize the need to explore the impact of DCs on neurodegeneration to uncover peripheral immune mechanisms of pathogenic importance, recognize potential biomarkers, and improve therapeutic approaches for neurodegenerative diseases.

Active immunization therapies for Parkinson's disease and multiple system atrophy

Vaccination is increasingly being investigated as a potential treatment for synucleinopathies, a group of neurodegenerative diseases including Parkinson's disease, multiple system atrophy, and dementia with Lewy bodies associated with α-synuclein pathology. All lack a causal therapy. Development of novel, disease-altering treatment strategies is urgently needed. Vaccination has positioned itself as a prime strategy for addressing these diseases because it is broadly applicable, requires infrequent administration, and maintains low production costs for treating a large population or as a preventive measure. Current evidence points to a causal role of misfolded α-synuclein in the development and progression of synucleinopathies. In the past decade, significant progress in active immunization against α-synuclein has been shown both in preclinical animal models and in early clinical development. In this review, we describe the state-of-the-art in active immunization approaches to synucleinopathies, with a focus on advances in Parkinson's disease (PD) and multiple-system atrophy (MSA). We first review preclinical animal models, highlighting their progress in translation to the clinical setting. We then discuss current clinical applications, stressing different approaches taken to address α-synuclein pathology. Finally, we address challenges, trends, and future perspectives of current vaccination programs.