Intravenous immunoglobulins containing antibodies against beta-amyloid for the treatment of Alzheimer's disease

Blood-based therapies to combat neurodegenerative diseases

Neurodegeneration, known as the progressive loss of neurons in terms of their structure and function, is the principal pathophysiological change found in the majority of brain-related disorders. Ageing has been considered the most well-established risk factor in most common neurodegenerative diseases, such as Parkinson's disease (PD) and Alzheimer's disease (AD). There is currently no effective treatment or cure for these diseases; the approved therapeutic options to date are only for palliative care. Ageing and neurodegenerative diseases are closely intertwined; reversing the aspects of brain ageing could theoretically mitigate age-related neurodegeneration. Ever since the regenerative properties of young blood on aged tissues came to light, substantial efforts have been focused on identifying and characterizing the circulating factors in the young and old systemic milieu that may attenuate or accentuate brain ageing and neurodegeneration. Later studies discovered the superiority of old plasma dilution in tissue rejuvenation, which is achieved through a molecular reset of the systemic proteome. These findings supported the use of therapeutic blood exchange for the treatment of degenerative diseases in older individuals. The first objective of this article is to explore the rejuvenating properties of blood-based therapies in the ageing brains and their therapeutic effects on AD. Then, we also look into the clinical applications, various limitations, and challenges associated with blood-based therapies for AD patients.

Recent Trends in Active and Passive Immunotherapies of Alzheimer's Disease

In the elderly, a debilitating condition known as dementia, which is a major health concern, is caused by Alzheimer's disease (AD). Despite promising advances by researchers, there is currently no way to completely cure this devastating disease. It is illustrated by the deposition of amyloid β-peptide (Aβ) plaques that are followed by neural dysfunction and cognitive decline. Responses against AD activate an immune system that contributes to and accelerates AD pathogenesis. Potential efforts in the field of pathogenesis have prompted researchers to explore novel therapies such as active and passive vaccines against Aβ proteins (Aβ immunotherapy), intravenous immunoglobulin, and tau immunotherapy, as well as targets that include microglia and several cytokines for the treatment of AD. Aims are now underway by experts to begin immunotherapies before the clinical manifestation, which is made possible by improving the sensitivity of biomarkers used for the diagnosis of AD to have better outcome measures. This review provides an overview of approved immunotherapeutic strategies for AD and those currently being investigated in clinical trials. We examine their mechanisms of action and discuss the potential perspectives and challenges associated with immunotherapies for AD.

Geroprotective interventions in the 3xTg mouse model of Alzheimer's disease

Alzheimer's disease (AD) is an age-associated neurodegenerative disease. As the population ages, the increasing prevalence of AD threatens massive healthcare costs in the coming decades. Unfortunately, traditional drug development efforts for AD have proven largely unsuccessful. A geroscience approach to AD suggests that since aging is the main driver of AD, targeting aging itself may be an effective way to prevent or treat AD. Here, we discuss the effectiveness of geroprotective interventions on AD pathology and cognition in the widely utilized triple-transgenic mouse model of AD (3xTg-AD) which develops both β-amyloid and tau pathologies characteristic of human AD, as well as cognitive deficits. We discuss the beneficial impacts of calorie restriction (CR), the gold standard for geroprotective interventions, and the effects of other dietary interventions including protein restriction. We also discuss the promising preclinical results of geroprotective pharmaceuticals, including rapamycin and medications for type 2 diabetes. Though these interventions and treatments have beneficial effects in the 3xTg-AD model, there is no guarantee that they will be as effective in humans, and we discuss the need to examine these interventions in additional animal models as well as the urgent need to test if some of these approaches can be translated from the lab to the bedside for the treatment of humans with AD.

An Exploratory Study Provides Insights into MMP9 and Aβ Levels in the Vitreous and Blood across Different Ages and in a Subset of AMD Patients

Matrix metalloproteinase-9 (MMP9) and total amyloid-beta (Aβ) are prospective biomarkers of ocular ageing and retinopathy. These were quantified by ELISA in the vitreous and blood from controls (n = 55) and in a subset of age-related macular degeneration (AMD) patients (n = 12) for insights and possible additional links between the ocular and systemic compartments. Vitreous MMP9 levels in control and AMD groups were 932.5 ± 240.9 pg/mL and 813.7 ± 157.6 pg/mL, whilst serum levels were 2228 ± 193 pg/mL and 2386.8 ± 449.4 pg/mL, respectively. Vitreous Aβ in control and AMD groups were 1173.5 ± 117.1 pg/mL and 1275.6 ± 332.9 pg/mL, whilst plasma Aβ were 574.3 ± 104.8 pg/mL and 542.2 ± 139.9 pg/mL, respectively. MMP9 and Aβ showed variable levels across the lifecourse, indicating no correlation to each other or with age nor AMD status, though the smaller AMD cohort was a limiting factor. Aβ and MMP9 levels in the vitreous and blood were unrelated to mean arterial pressure. Smoking, another modifiable risk, showed no association with vitreous Aβ. However, smoking may be linked with vitreous (p = 0.004) and serum (p = 0.005) MMP9 levels in control and AMD groups, though this did not reach our elevated (p = 0.001) significance. A bioinformatics analysis revealed promising MMP9 and APP/Aβ partners for further scrutiny, many of which are already linked with retinopathy.

Investigating Changes in the Serum Inflammatory Factors in Alzheimer's Disease and Their Correlation with Cognitive Function

BACKGROUND

Serum levels of inflammatory factors, such as C3, C4, C-reactive protein (CRP), immunoglobulin (Ig) G, IgA, and IgM, in patients with Alzheimer's disease (AD) and their correlation with cognitive function remain unexplored.

OBJECTIVE

To investigate the expression of serum inflammatory factors in patients with AD and its correlation with cognitive function.

METHODS

Serum levels of C3, C4, CRP, IgG, IgA, and IgM in 200 patients with AD (mild, moderate, and severe) and those in 174 normal controls were assessed. Spearman's rank correlation analysis was used to explore the relationships among biomarker levels, cognitive function, and activities of daily living (ADL).

RESULTS

Among these inflammatory factors, C3 and CRP levels were significantly lower, and IgG and IgA levels were significantly higher in the AD group than in the control group (p < 0.05). There were no significant differences in C4 and IgM levels between the two groups (p > 0.05). In all participants, CRP level was positively correlated with the Mini-Mental State Examination and Montreal Cognitive Assessment scores (p < 0.05). In the AD group, IgA level was negatively associated with ADL scores (p < 0.05). No significant correlation was detected between the other factors and different cognitive scores (p > 0.05).

CONCLUSION

Inflammatory factors C3, CRP, IgG, and IgA have the potential to serve as biomarkers for AD. Furthermore, serum IgA was not only correlated with AD but also with ADL. These results support the hypothesis that inflammation is involved in the occurrence and development of AD.

Update on Intravenous Immunoglobulin in Neurology: Modulating Neuro-autoimmunity, Evolving Factors on Efficacy and Dosing and Challenges on Stopping Chronic IVIg Therapy

In the last 25 years, intravenous immunoglobulin (IVIg) has had a major impact in the successful treatment of previously untreatable or poorly controlled autoimmune neurological disorders. Derived from thousands of healthy donors, IVIg contains IgG1 isotypes of idiotypic antibodies that have the potential to bind pathogenic autoantibodies or cross-react with various antigenic peptides, including proteins conserved among the "common cold"-pre-pandemic coronaviruses; as a result, after IVIg infusions, some of the patients' sera may transiently become positive for various neuronal antibodies, even for anti-SARS-CoV-2, necessitating caution in separating antibodies derived from the infused IVIg or acquired humoral immunity. IVIg exerts multiple effects on the immunoregulatory network by variably affecting autoantibodies, complement activation, FcRn saturation, FcγRIIb receptors, cytokines, and inflammatory mediators. Based on randomized controlled trials, IVIg is approved for the treatment of GBS, CIDP, MMN and dermatomyositis; has been effective in, myasthenia gravis exacerbations, and stiff-person syndrome; and exhibits convincing efficacy in autoimmune epilepsy, neuromyelitis, and autoimmune encephalitis. Recent evidence suggests that polymorphisms in the genes encoding FcRn and FcγRIIB may influence the catabolism of infused IgG or its anti-inflammatory effects, impacting on individualized dosing or efficacy. For chronic maintenance therapy, IVIg and subcutaneous IgG are effective in controlled studies only in CIDP and MMN preventing relapses and axonal loss up to 48 weeks; in practice, however, IVIg is continuously used for years in all the aforementioned neurological conditions, like is a "forever necessary therapy" for maintaining stability, generating challenges on when and how to stop it. Because about 35-40% of patients on chronic therapy do not exhibit objective neurological signs of worsening after stopping IVIg but express subjective symptoms of fatigue, pains, spasms, or a feeling of generalized weakness, a conditioning effect combined with fear that discontinuing chronic therapy may destabilize a multi-year stability status is likely. The dilemmas of continuing chronic therapy, the importance of adjusting dosing and scheduling or periodically stopping IVIg to objectively assess necessity, and concerns in accurately interpreting IVIg-dependency are discussed. Finally, the merit of subcutaneous IgG, the ineffectiveness of IVIg in IgG4-neurological autoimmunities, and genetic factors affecting IVIg dosing and efficacy are addressed.

Alzheimer's disease neuropathology is exacerbated following traumatic brain injury. Neuroprotection by co-administration of nanowired mesenchymal stem cells and cerebrolysin with monoclonal antibodies to amyloid beta peptide

Military personnel are prone to traumatic brain injury (TBI) that is one of the risk factors in developing Alzheimer's disease (AD) at a later stage. TBI induces breakdown of the blood-brain barrier (BBB) to serum proteins into the brain and leads to extravasation of plasma amyloid beta peptide (ΑβP) into the brain fluid compartments causing AD brain pathology. Thus, there is a need to expand our knowledge on the role of TBI in AD. In addition, exploration of the novel roles of nanomedicine in AD and TBI for neuroprotection is the need of the hour. Since stem cells and neurotrophic factors play important roles in TBI and in AD, it is likely that nanodelivery of these agents exert superior neuroprotection in TBI induced exacerbation of AD brain pathology. In this review, these aspects are examined in details based on our own investigations in the light of current scientific literature in the field. Our observations show that TBI exacerbates AD brain pathology and TiO₂ nanowired delivery of mesenchymal stem cells together with cerebrolysin-a balanced composition of several neurotrophic factors and active peptide fragments, and monoclonal antibodies to amyloid beta protein thwarted the development of neuropathology following TBI in AD, not reported earlier.

Five-year outcomes after IVIG for mild cognitive impairment due to alzheimer disease

Background

The purpose of this study was to assess the five-year treatment effects of a short course of intravenous immunoglobulin (IVIG) in subjects with mild cognitive impairment (MCI) due to Alzheimer disease (AD).

Methods

Fifty subjects 50 to 84 years of age with MCI due to AD were administered 0.4 g/kg 10% IVIG or 0.9% saline every two weeks x five doses in a randomized double-blinded design as part of a two-year study. Twenty-seven subjects completed an additional three-year extension study. MRI brain imaging, cognitive testing, and conversion to dementia were assessed annually. Participants were stratified into early MCI (E-MCI) and late MCI (L-MCI). The primary endpoint was brain atrophy measured as annualized percent change in ventricular volume (APCV) annually for five years. ANOVA was used to compare annualized percent change in ventricular volume from baseline between the groups adjusting for MCI status (E-MCI, L-MCI).

Results

Differences in brain atrophy between the groups, which were statistically significant after one year, were no longer significant after five years. IVIG-treated L-MCI subjects did demonstrate a delay in conversion to dementia of 21.4 weeks.

Conclusion

An eight-week course of IVIG totaling 2 g/kg in MCI is safe but is not sufficient to sustain an initial reduction in brain atrophy or a temporary delay in conversion to dementia at five years. Other dosing strategies of IVIG in the early stages of AD should be investigated to assess more sustainable disease-modifying effects.

Trial registration ClinicalTrials.gov NCT01300728. Registered 23 February 2011.

Advances in Drug Therapy for Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disease that mainly causes dementia. It is a serious threat to the health of the global elderly population. Considerable money and effort has been invested in the development of drug therapy for AD worldwide. Many drug therapies are currently under development or in clinical trials, based on two known mechanisms of AD, namely, Aβ toxicity and the abnormal Tau hyperphosphorylation. Numerous drugs are also being developed for other AD associated mechanisms such as neuroinflammation, neurotransmitter imbalance, oxidative damage and mitochondrial dysfunction, neuron loss and degeneration. Even so, the number of drugs that can successfully improve symptoms or delay the progression of the disease remains very limited. However, multi-drug combinations may provide a new avenue for drug therapy for AD. In addition, early diagnosis of AD and timely initiation of treatment may allow drugs that act on the early pathological processes of AD to help improve the symptoms and prevent the progression of the condition.

Alzheimer's Disease: New Concepts on the Role of Autoimmunity and NLRP3 Inflammasome in the Pathogenesis of the Disease

Alzheimer's disease (AD), recognized as the most common neurodegenerative disorder, is clinically characterized by the presence of extracellular beta-amyloid (Aβ) plaques and by intracellular neurofibrillary tau tangles, accompanied by glial activation and neuroinflammation. Increasing evidence suggests that self-misfolded proteins stimulate an immune response mediated by glial cells, inducing the release of inflammatory mediators and the recruitment of peripheral macrophages into the brain, which in turn aggravate AD pathology. The present review aims to update the current knowledge on the role of autoimmunity and neuroinflammation in the pathogenesis of the disease, indicating a new target for therapeutic intervention. We mainly focused on the NLRP3 microglial inflammasome as a critical factor in stimulating innate immune responses, thus sustaining chronic inflammation. Additionally, we discussed the involvement of the NLRP3 inflammasome in the gut-brain axis. Direct targeting of the NLRP3 inflammasome and the associated receptors could be a potential pharmacological strategy since its inhibition would selectively reduce AD neuroinflammation.

Effect of Different Aβ Aggregates as Antigen on the Measure of Naturally Occurring Autoantibodies against Amyloid-β40/42 in IVIG

BACKGROUND

The specific Intravenous Immunoglobulin (IVIG) for Alzheimer's Disease (AD) is developing, which contains a high level of naturally occurring autoantibodies against amyloid-β (nAbs-Aβ), and the measure of nAbs-Aβ content is greatly essential. Though Enzyme-Linked Immunosorbent Assay (ELISA) has been widely used in detecting the nAbs-Aβ content, the impact of Aβ aggregates species chosen as antigen in ELISA on this measure has not been evaluated.

OBJECTIVE

To clarify the influence of different Aβ40/42 aggregates as antigen during ELISA on the content of nAbs-Aβ40/42 measured in IVIG.

METHOD

Preparation of various Aβ40/42 aggregates was performed by different aggregation solutions and various lengths of time, and analyzed by western blot. Different Aβ40/42 aggregates as antigen were adopted to measure the nAbs-Aβ40/42 content in IVIG by ELISA, and the control was carried out to reduce interference of nonspecific binding. The Bonferroni and Dunnett's T3 were used for statistical analysis.

RESULTS

The duration for the formation of Aβ40/42 aggregates had more effect on detecting nAbs-Aβ40/42 content in IVIG than the aggregation solution. Higher content of nAbs-Aβ40/42 in the same IVIG was displayed when measured with Aβ40/42 aggregates at day 3, instead of at day 0.5 and day 7.0. The nAbs- Aβ40/42 contents in the same IVIG measured with Aβ40/42 aggregates prepared in different solutions were obviously different, but there was no significant regularity among them.

CONCLUSION

The nAbs-Aβ40/42 content in the same IVIG is significantly different when measured with Aβ40/42 aggregated under different conditions. The nAbs-Aβ40/42 content in IVIG by antigen-dependent measures, like ELISA, is uncertain.

Content of anti-β-amyloid42 oligomers antibodies in multiple batches from different immunoglobulin preparations

Immunoglobulin preparations are one of the promising drugs for Alzheimer's disease (AD). Anti-β-amyloid (Aβ) oligomers antibodies in immunoglobulin preparations are considered to be critical for the therapeutic effect against Alzheimer's disease. However, the antibodies content in immunoglobulin preparations varies greatly. In order to determine which factor contributes to the difference of the antibodies content, the content of anti-Aβ oligomers antibodies in multiple batches of immunoglobulin preparations from two manufacturers were measured by enzyme-linked immunosorbent assay. The results showed that no significant difference was found in the antibodies content among different bathes of normal immunoglobulin preparations prepared by the same process from the same manufacturer, whereas significant difference was found in the antibodies content between normal immunoglobulin preparations prepared by ethanol fractionation and those by chromatography process from the same manufacturer. In addition, significant variation existed in the antibodies content between normal immunoglobulin preparations and specific immunoglobulin preparations that are produced by plasma pool of immunized donors. Based on analysis of these results, the preparation process and raw plasma could be the main contributing factors affecting the content of anti-Aβ oligomers antibodies in immunoglobulin preparations. This finding might help to develop AD-specific immunoglobulin preparation containing higher content of anti-Aβ oligomers antibodies.

Recent advances in the design and applications of amyloid-β peptide aggregation inhibitors for Alzheimer's disease therapy

Alzheimer's disease (AD) is an irreversible neurological disorder that progresses gradually and can cause severe cognitive and behavioral impairments. This disease is currently considered a social and economic incurable issue due to its complicated and multifactorial characteristics. Despite decades of extensive research, we still lack definitive AD diagnostic and effective therapeutic tools. Consequently, one of the most challenging subjects in modern medicine is the need for the development of new strategies for the treatment of AD. A large body of evidence indicates that amyloid-β (Aβ) peptide fibrillation plays a key role in the onset and progression of AD. Recent studies have reported that amyloid hypothesis-based treatments can be developed as a new approach to overcome the limitations and challenges associated with conventional AD therapeutics. In this review, we will provide a comprehensive view of the challenges in AD therapy and pathophysiology. We also discuss currently known compounds that can inhibit amyloid-β (Aβ) aggregation and their potential role in advancing current AD treatments. We have specifically focused on Aβ aggregation inhibitors including metal chelators, nanostructures, organic molecules, peptides (or peptide mimics), and antibodies. To date, these molecules have been the subject of numerous in vitro and in vivo assays as well as molecular dynamics simulations to explore their mechanism of action and the fundamental structural groups involved in Aβ aggregation. Ultimately, the aim of these studies (and current review) is to achieve a rational design for effective therapeutic agents for AD treatment and diagnostics.

Anti-Aβ drug candidates in clinical trials and plasmonic nanoparticle-based drug-screen for Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of neurodegenerative disorder in elderly people, and has become a social problem in aging societies globally. Amyloid-β (Aβ) aggregates (i.e., Aβ fibrils and plaques) present in the brains of AD patients are hallmarks of AD. Although various promising anti-Aβ drugs have been tested in pre-clinical and randomized controlled trials, the trial results have not yet been translated into clinical practice due to increasing time and cost of drug development. Recent investigations have addressed how the formation of Aβ aggregates is influenced by the surface of gold nanoparticles (AuNPs) to obtain a detailed understanding of the in vivo process of amyloid formation. Particularly, AuNPs catalytically provide nucleation sites to accelerate the formation of Aβ aggregates. Moreover, AuNPs have great potential as a sensing tool due to their optical property. Employing this dual function (i.e., catalytic and optical property), AuNP-based colorimetry is highlighted as a simple and innovative method for monitoring the efficacy of anti-Aβ reagents. In this review, we briefly survey important developments and designs of anti-Aβ drugs. The significance and perspectives of AuNP-based drug-screening in pharmacologic research are also discussed.

The impact of self-replicating proteins on inflammation, autoimmunity and neurodegeneration-An untraveled path

The central nervous system (CNS) in neurodegenerative diseases is a battlefield in which microglia fight a highly atypical battle. During the inflammatory process microglia themselves become dysfunctional and even with all the available immune arsenal including cytokine or/and antibody production, the battle is eventually lost. A closer look into the picture will reveal the fact that this is mainly due to the atypical characteristics of the infectious agent. The supramolecular assemblies of misfolded proteins carry unique features not encountered in any of the common pathogens. Through misfolding, proteins undergo conformational changes which make them become immunogenic, neurotoxic and highly infective. The immunogenicity appears to be triggered by the exposure of previously hidden hydrophobic portions in proteins which act as damage-associated molecular patters (DAMPs) for the immune system. The neurotoxicity and infectivity are promoted by the small oligomeric forms of misfolded proteins/peptides. Oligomers adopt conformations such as tubular-like, beta-barrel-like, etc., that penetrate cell membranes through their hydrophobic surfaces, thus destabilizing ionic homeostasis. At the same time, oligomers act as a seed for protein misfolding through a prion/prion-like mechanism. Here, we propose the hypothesis that oligomers have catalytic surfaces and exercise their capacity to infect native proteins through specific characteristics such as hydrophobic, electrostatic and π-π stacking interactions as well as the specific surface area (SSA), surface curvature and surface chemistry of their nanoscale supramolecular assemblies. All these are the key elements for prion/prion-like mechanism of self-replication and disease spreading within the CNS. Thus, understanding the mechanism of prion's templating activity may help us in the prevention and development of novel therapeutic strategies for neurodegenerative diseases.

Biomarkers in Neurodegenerative Diseases

The past decade has seen tremendous efforts in biomarker discovery and validation for neurodegenerative diseases. The source and type of biomarkers has continued to grow for central nervous system diseases, from biofluid-based biomarkers (blood or cerebrospinal fluid (CSF)), to nucleic acids, tissue, and imaging. While DNA remains a predominant biomarker used to identify familial forms of neurodegenerative diseases, various types of RNA have more recently been linked to familial and sporadic forms of neurodegenerative diseases during the past few years. Imaging approaches continue to evolve and are making major contributions to target engagement and early diagnostic biomarkers. Incorporation of biomarkers into drug development and clinical trials for neurodegenerative diseases promises to aid in the development and demonstration of target engagement and drug efficacy for neurologic disorders. This review will focus on recent advancements in developing biomarkers for clinical utility in Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS).

Mechanisms of action of intravenous immunoglobulin in septic encephalopathy

Acute brain dysfunction associated with sepsis is a serious complication that results in morbidity and mortality. Intravenous immunoglobulin (IVIg) treatment is known to alleviate behavioral deficits in the experimentally induced model of sepsis. To delineate the mechanisms by which IVIg treatment prevents neuronal dysfunction, an array of immunological and apoptosis markers was investigated. Our results suggest that IVIgG and IgGAM administration ameliorates neuronal dysfunction and behavioral deficits by reducing apoptotic cell death and glial cell proliferation. IgGAM treatment might suppress classical complement pathway by reducing C5a activity and proapoptotic NF-κB and Bax expressions, thereby, inhibiting major inflammation and apoptosis cascades. Future animal model experiments performed with specific C5aR and NF-κB agonists/antagonists or C5aR-deficient mice might more robustly disclose the significance of these pathways. C5a, C5aR, and NF-κB, which were shown to be the key molecules in brain injury pathogenesis in sepsis, might also be utilized as potential targets for future treatment trials of septic encephalopathy.

IVIG Delays Onset in a Mouse Model of Gerstmann-Sträussler-Scheinker Disease

Our previous studies showed that intravenous immunoglobulin (IVIG) contained anti-Aβ autoantibodies that might be able to treat Alzheimer's disease (AD). Recently, we identified and characterized naturally occurring autoantibodies against PrP from IVIG. Although autoantibodies in IVIG blocked PrP fibril formation and PrP neurotoxicity in vitro, it remained unknown whether IVIG could reduce amyloid plaque pathology in vivo and be used to effectively treat animals with prion diseases. In this study, we used Gerstmann-Sträussler-Scheinker (GSS)-Tg (PrP-A116V) transgenic mice to test IVIG efficacy since amyloid plaque formation played an important role in GSS pathogenesis. Here, we provided strong evidence that demonstrates how IVIG could significantly delay disease onset, elongate survival, and improve clinical phenotype in Tg (PrP-A116V) mice. Additionally, in treated animals, IVIG could markedly inhibit PrP amyloid plaque formation and attenuate neuronal apoptosis at the age of 120 days in mice. Our results indicate that IVIG may be a potential, effective therapeutic treatment for GSS and other prion diseases.

Intravenous immunoglobulin ameliorates motor and cognitive deficits and neuropathology in R6/2 mouse model of Huntington's disease by decreasing mutant huntingtin protein level and normalizing NF-κB signaling pathway

Huntington's disease (HD) is a fatal neurodegenerative disorder characterized by progressive movement disorders and cognitive deficits, which is caused by a CAG-repeat expansion encoding an extended polyglutamine (polyQ) tract in the huntingtin protein (HTT). Reduction of mutant HTT levels and inhibition of neuroinflammation has been proposed as a major therapeutic strategy in treating HD. Intravenous immunoglobulin (IVIg) therapy has been firmly established for the treatment of several autoimmune or inflammatory neurological diseases, either as adjunctive treatment or as first-line therapy. However, whether IVIg has therapeutic potential on HD remains unclear. Here we for the first time demonstrated that IVIg treatment remarkably rescued motor and cognitive deficits, prevented synaptic degeneration, attenuated neuroinflammation and oxidative stress in R6/2 mouse model. Further investigation showed that the beneficial effects of IVIg resulted from the reduced levels of mutant HTT and inhibition of NF-κB signalling pathway. These findings suggest that IVIg is a promising therapeutic potential for HD.

Toward a Rational Design to Regulate β-Amyloid Fibrillation for Alzheimer's Disease Treatment

The last decades have witnessed a growing global burden of Alzheimer's disease (AD). Evidence indicates that the onset and progression of AD is associated with β-amyloid (Aβ) peptide fibrillation. As such, there is a strong passion with discovering potent Aβ fibrillation inhibitors that can be developed into anti-amyloiddogenic agents for AD treatment. Current challenges that have arisen with this development involve with Aβ oligomer toxicity suppression and Blood Brain Barrier penetration capability. Considering most natural or biological events, one would observe that there is usually a "seed" to direct natural materials to assemble in response to a certain stimulation. Inspired by this, several materials or compounds, including nanoparticle, peptide or peptide mimics, and organic molecules, have been designed for the purpose of redirecting or impeding Aβ aggregation. Achieving these tasks requires comprehensive understanding on (1) initial Aβ assembly into insoluble deposits, (2) main concerns with fibrillation inhibition, and (3) current major methodologies to disrupt the aggregation. Herein, the objective of this review is to address these three areas, and enable the pathway for a promising therapeutic agent design for AD treatment.

Modulators of IgG penetration through the blood-brain barrier: Implications for Alzheimer's disease immunotherapy

This review serves to highlight approaches that may improve the access of antibody drugs to regions of the brain affected by Alzheimer's Disease. While previous antibody drugs have been unsuccessful in treating Alzheimer's disease, recent work demonstrates that Alzheimer's pathology can be modified if these drugs can penetrate the brain parenchyma with greater efficacy. Research in antibody blood-brain barrier drug delivery predominantly follows one of three distinct directions: (1) enhancing influx with reduced antibody size, addition of Trojan horse modules, or blood-brain barrier disruption; (2) modulating trancytotic equilibrium and/or kinetics of the neonatal Fc Receptor; and (3) manipulation of antibody glycan carbohydrate composition. In addition to these topics, recent studies are discussed that reveal a role of glycan sialic acid in suppressing antibody efflux from the brain.

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.

Microglia: An Interface between the Loss of Neuroplasticity and Depression

Depression has been widely accepted as a major psychiatric disease affecting nearly 350 million people worldwide. Research focus is now shifting from studying the extrinsic and social factors of depression to the underlying molecular causes. Microglial activity is shown to be associated with pathological conditions, such as psychological stress, pathological aging, and chronic infections. These are primary immune effector cells in the CNS and regulate the extensive dialogue between the nervous and the immune systems in response to different immunological, physiological, and psychological stressors. Studies have suggested that during stress and pathologies, microglia play a significant role in the disruption of neuroplasticity and have detrimental effects on neuroprotection causing neuroinflammation and exacerbation of depression. After a systematic search of literature databases, relevant articles on the microglial regulation of bidirectional neuroimmune pathways affecting neuroplasticity and leading to depression were reviewed. Although, several hypotheses have been proposed for the microglial role in the onset of depression, it is clear that all molecular pathways to depression are linked through microglia-associated neuroinflammation and hippocampal degeneration. Molecular factors such as an excess of glucocorticoids and changes in gene expression of neurotrophic factors, as well as neuro active substances secreted by gut microbiota have also been shown to affect microglial morphology and phenotype resulting in depression. This review aims to critically analyze the various molecular pathways associated with the microglial role in depression.

The antigen-binding fragment of human gamma immunoglobulin prevents amyloid β-peptide folding into β-sheet to form oligomers

The amyloid beta-peptide (Aβ) plays a leading role in Alzheimer's disease (AD) physiopathology. Even though monomeric forms of Aβ are harmless to cells, Aβ can aggregate into β-sheet oligomers and fibrils, which are both neurotoxic. Therefore, one of the main therapeutic approaches to cure or delay AD onset and progression is targeting Aβ aggregation. In the present study, we show that a pool of human gamma immunoglobulins (IgG) protected cortical neurons from the challenge with Aβ oligomers, as assayed by MTT reduction, caspase-3 activation and cytoskeleton integrity. In addition, we report the inhibitory effect of IgG on Aβ aggregation, as shown by Thioflavin T assay, size exclusion chromatography and atomic force microscopy. Similar results were obtained with Palivizumab, a human anti-sincitial virus antibody. In order to dissect the important domains, we cleaved the pool of human IgG with papain to obtain Fab and Fc fragments. Using these cleaved fragments, we functionally identified Fab as the immunoglobulin fragment inhibiting Aβ aggregation, a result that was further confirmed by an in silico structural model. Interestingly, bioinformatic tools show a highly conserved structure able to bind amyloid in the Fab region. Overall, our data strongly support the inhibitory effect of human IgG on Aβ aggregation and its neuroprotective role.

Antibody blood-brain barrier efflux is modulated by glycan modification

BACKGROUND

Drug delivery to the brain is a major roadblock to treatment of Alzheimer's disease. Recent results of the PRIME study indicate that increasing brain penetration of antibody drugs improves Alzheimer's treatment outcomes. New approaches are needed to better accomplish this goal. Based on prior evidence, the hypothesis that glycan modification alters antibody blood-brain barrier permeability was tested here.

METHODS

The blood-brain barrier permeability coefficient Pe of different glycosylated states of anti-amyloid IgG was measured using in vitro models of brain microvascular endothelial cells. Monoclonal antibodies 4G8, with sialic acid, and 6E10, lacking sialic acid, were studied. The amount of sialic acid was determined using quantitative and semi-quantitative surface plasmon resonance methods.

RESULTS

Influx of IgG was not saturable and was largely insensitive to IgG species and glycosylation state. By contrast, efflux of 4G8 efflux was significantly lower than both albumin controls and 6E10. Removal of α2,6-linked sialic acid group present on 12% of 4G8 completely restored efflux to that of 6E10 but increasing the α2,6-sialylated fraction to 15% resulted in no change. Removal of the Fc glycan from 4G8 partially restored efflux. Alternate sialic acid groups with α2,3 and α2,8 linkages, nor on the Fc glycan, were not detected at significant levels on either 4G8 or 6E10.

CONCLUSIONS

These results support a model in which surface-sialylated 4G8 inhibits its own efflux and that of asialylated 4G8.

GENERAL SIGNIFICANCE

Glycan modification has the potential to increase antibody drug penetration into the brain through efflux inhibition.

Aβ levels in the jugular vein and high molecular weight Aβ oligomer levels in CSF can be used as biomarkers to indicate the anti-amyloid effect of IVIg for Alzheimer's disease

Intravenous immunoglobulin (IVIg) has been a candidate as a potential anti-amyloid immunotherapy for Alzheimer disease (AD) because it contains anti-amyloid β (Aβ) antibodies. Although several studies with IVIg in AD have been published, changing levels of Aβ efflux from the brain, or disaggregation of Aβ species induced by immunotherapy, have not been properly investigated. Here, we carried out an open label study of therapy with IVIg in five patients with AD. We collected plasma from a peripheral vein (peripheral-plasma) and from the internal jugular vein (jugular-plasma) to estimate directly the efflux of soluble Aβ from the brain. We also measured high molecular weight (HMW) Aβ oligomers in CSF as a marker to detect disaggregated Aβ. IVIg infusions were well tolerated in the majority of cases. However, one study subject had epileptic seizures after IVIg. Levels of HMW CSF Aβ oligomers in all participants were significantly increased after IVIg. Aβ40 and Aβ42 levels in jugular-plasma were continuously or temporarily elevated after treatment in three of five patients who showed preserved cognitive function, whereas levels of those in peripheral-plasma did not correlate with reactivity to the treatment. Other conventional biomarkers including 11C-Pittsburgh compound B retention were not altered after the treatment. These findings imply that HMW Aβ oligomer levels could be a better biomarker to reflect the anti-amyloid effects of IVIg than conventional Aβ species; moreover, Aβ in jugular-plasma seems to be a more direct and precise biomarker to estimate clearance of Aβ from the brain rather than Aβ in peripheral-plasma.

TRIAL REGISTRATION

UMIN000022319.

A phase 3 trial of IV immunoglobulin for Alzheimer disease

OBJECTIVE

We tested biweekly infusions of IV immunoglobulin (IVIg) as a possible treatment for mild to moderate Alzheimer disease (AD) dementia.

METHODS

In a phase 3, double-blind, placebo-controlled trial, we randomly assigned 390 participants with mild to moderate AD to receive placebo (low-dose albumin) or IVIg (Gammagard Liquid; Baxalta, Bannockburn, IL) administered IV at doses of 0.2 or 0.4 g/kg every 2 weeks for 18 months. The primary cognitive outcome was change from baseline to 18 months on the 11-item cognitive subscale of the Alzheimer's Disease Assessment Scale; the primary functional outcome was 18-month change on the Alzheimer's Disease Cooperative Study-Activities of Daily Living Inventory. Safety and tolerability data, as well as serial MRIs and plasma samples, were collected throughout the study from all enrolled participants.

RESULTS

No beneficial effects were observed in the dual primary outcome measures for the 2 IVIg doses tested. Significant decreases in plasma Aβ42 (but not Aβ40) levels were observed in IVIg-treated participants. Analysis of safety data showed no difference between IVIg and placebo in terms of the rate of occurrence of amyloid-related imaging abnormalities (brain edema or microhemorrhage). IVIg-treated participants had more systemic reactions (chills, rashes) but fewer respiratory infections than participants receiving placebo.

CONCLUSIONS

Participants with mild to moderate AD showed good tolerability of treatment with low-dose human IVIg for 18 months but did not show beneficial effects on cognition or function relative to participants who received placebo.

CLINICALTRIALSGOV IDENTIFIER

NCT00818662.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that IVIg infusions performed every 2 weeks do not improve cognition or function at 18 months in patients with mild to moderate AD.

IVIG treatment of mild cognitive impairment due to Alzheimer's disease: a randomised double-blinded exploratory study of the effect on brain atrophy, cognition and conversion to dementia

OBJECTIVE

To determine the effect of intravenous immunoglobulin (IVIG) on brain atrophy and cognitive function in mild cognitive impairment (MCI) due to Alzheimer's disease (AD).

METHODS

50 participant 50-84 years of age with amnestic MCI were administered 0.4 g/kg 10% IVIG or 0.9% saline every 2 weeks for a total of 5 infusions (2 g/kg total dose) in a randomised double-blinded design. MRI brain was completed at baseline, 12  and 24 months. Cognitive testing was completed at baseline and every 4 months. Participants were stratified into early and late (LMCI) MCI stages. Average annualised per cent change in ventricular volume was computed as a measure of brain atrophy.

RESULTS

There was significantly less brain atrophy (p=0.037, adjusted for MCI status) in the IVIG group (5.87%) when compared with placebo (8.14%) at 12 months; at 24 months, the reduction in brain atrophy no longer reached statistical significance. The LMCI participants who received IVIG performed better on Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-Cog; p=0.011) and Mini-Mental State Examination (MMSE; p=0.004) at 1 year; these differences were not present after 2 years. There was no difference in conversion to AD dementia between the treatment and control groups after 2 years; however, at 1 year, there were fewer conversions from LMCI to AD dementia in the IVIG group (33.3%) when compared with control group (58.3%).

CONCLUSIONS

This exploratory study provides limited evidence that a short course of IVIG administered in the MCI stage of AD reduces brain atrophy, prevents cognitive decline in LMCI and delays conversion to AD dementia for at least 1 year; however, this effect of IVIG appears to wane by 2 years.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov, NCT01300728.

Association between naturally occurring anti-amyloid β autoantibodies and medial temporal lobe atrophy in Alzheimer's disease

BACKGROUND

Naturally occurring autoantibodies against amyloid β (Aβ) peptide exist in the serum and cerebrospinal fluid (CSF) of healthy individuals. Recently, it was reported that administration of intravenous immunoglobulin at the mild cognitive impairment (MCI) stage of Alzheimer's disease (AD) reduces brain atrophy.

OBJECTIVE

To examine the association between naturally occurring anti-Aβ autoantibodies and brain atrophy in patients with cognitive impairment.

METHODS

Serum and CSF levels of anti-Aβ autoantibodies and CSF biomarkers were evaluated in 68 patients with cognitive impairment, comprising 44 patients with AD, 19 patients with amnestic MCI and five patients with non-Alzheimer's dementia. The degree of brain atrophy was assessed using the voxel-based specific regional analysis system for AD, which targets the volume of interest (VOI) in medial temporal structures, including the whole hippocampus, entorhinal cortex and amygdala.

RESULTS

CSF levels of anti-Aβ autoantibodies were inversely correlated with the extent and severity of VOI atrophy, and the ratio of VOI/grey matter atrophy in patients with AD, but not in MCI or non-AD patients. Serum levels of anti-Aβ autoantibodies were not associated with these parameters in any of the patient groups.

CONCLUSIONS

These results indicate that CSF levels of naturally occurring anti-Aβ autoantibodies are inversely associated with the degree of the VOI atrophy in patients with AD. Although the mechanism is unclear, CSF levels of naturally occurring anti-Aβ autoantibodies may be implicated in the progression of atrophy of the whole hippocampus, entorhinal cortex and amygdala, in AD.

Biomarkers for the Early Detection and Progression of Alzheimer's Disease

The recent failures of potential disease-modifying drugs for Alzheimer's disease (AD) may reflect the fact that the enrolled participants in clinical trials are already too advanced to derive a clinical benefit. Thus, well-validated biomarkers for the early detection and accurate diagnosis of the preclinical stages of AD will be crucial for therapeutic advancement. The combinatorial use of biomarkers derived from biological fluids, such as cerebrospinal fluid (CSF), with advanced molecular imaging and neuropsychological testing may eventually achieve the diagnostic sensitivity and specificity necessary to identify people in the earliest stages of the disease when drug modification is most likely possible. In this regard, positive amyloid or tau tracer retention on positron emission tomography imaging, low CSF concentrations of the amyloid-β 1-42 peptide, high CSF concentrations in total tau and phospho-tau, mesial temporal lobe atrophy on magnetic resonance imaging, and temporoparietal/precuneus hypometabolism or hypoperfusion on 18F-fluorodeoxyglucose positron emission tomography have all emerged as biomarkers for the progression to AD. However, the ultimate AD biomarker panel will likely involve the inclusion of novel CSF and blood biomarkers more precisely associated with confirmed pathophysiologic mechanisms to improve its reliability for detecting preclinical AD. This review highlights advancements in biological fluid and imaging biomarkers that are moving the field towards achieving the goal of a preclinical detection of AD.

Update on the use of immunoglobulin in human disease: A review of evidence

Human immunoglobulin preparations for intravenous or subcutaneous administration are the cornerstone of treatment in patients with primary immunodeficiency diseases affecting the humoral immune system. Intravenous preparations have a number of important uses in the treatment of other diseases in humans as well, some for which acceptable treatment alternatives do not exist. We provide an update of the evidence-based guideline on immunoglobulin therapy, last published in 2006. Given the potential risks and inherent scarcity of human immunoglobulin, careful consideration of its indications and administration is warranted.

Herpes Simplex Virus Type 1 and Other Pathogens are Key Causative Factors in Sporadic Alzheimer's Disease

This review focuses on research in epidemiology, neuropathology, molecular biology, and genetics regarding the hypothesis that pathogens interact with susceptibility genes and are causative in sporadic Alzheimer's disease (AD). Sporadic AD is a complex multifactorial neurodegenerative disease with evidence indicating coexisting multi-pathogen and inflammatory etiologies. There are significant associations between AD and various pathogens, including Herpes simplex virus type 1 (HSV-1), Cytomegalovirus, and other Herpesviridae, Chlamydophila pneumoniae, spirochetes, Helicobacter pylori, and various periodontal pathogens. These pathogens are able to evade destruction by the host immune system, leading to persistent infection. Bacterial and viral DNA and RNA and bacterial ligands increase the expression of pro-inflammatory molecules and activate the innate and adaptive immune systems. Evidence demonstrates that pathogens directly and indirectly induce AD pathology, including amyloid-β (Aβ) accumulation, phosphorylation of tau protein, neuronal injury, and apoptosis. Chronic brain infection with HSV-1, Chlamydophila pneumoniae, and spirochetes results in complex processes that interact to cause a vicious cycle of uncontrolled neuroinflammation and neurodegeneration. Infections such as Cytomegalovirus, Helicobacter pylori, and periodontal pathogens induce production of systemic pro-inflammatory cytokines that may cross the blood-brain barrier to promote neurodegeneration. Pathogen-induced inflammation and central nervous system accumulation of Aβ damages the blood-brain barrier, which contributes to the pathophysiology of AD. Apolipoprotein E4 (ApoE4) enhances brain infiltration by pathogens including HSV-1 and Chlamydophila pneumoniae. ApoE4 is also associated with an increased pro-inflammatory response by the immune system. Potential antimicrobial treatments for AD are discussed, including the rationale for antiviral and antibiotic clinical trials.

Demonstration of safety of intravenous immunoglobulin in geriatric patients in a long-term, placebo-controlled study of Alzheimer's disease

INTRODUCTION

We present safety results from a study of Gammagard Liquid intravenous immunoglobulin (IGIV) in patients with probable Alzheimer's disease.

METHODS

This was a placebo-controlled double-blind study. Subjects were randomized to 400 mg/kg (n = 127), 200 mg/kg (n = 135) IGIV, or to 0.25% human albumin (n = 121) administered every 2 weeks ± 7 days for 18 months.

RESULTS

Elevated risk ratios of IGIV versus placebo included chills (3.85) in 9.5% of IGIV-treated subjects (all doses), compared to 2.5% of placebo-treated subjects, and rash (3.08) in 15.3% of IGIV-treated subjects versus 5.0% of subjects treated with placebo. Subjects in the highest IGIV dose group had the lowest proportion of SAEs considered related to product (2 of 127 [1.6%]). Subjects treated with IGIV experienced a lower rate of respiratory and all other infections compared to placebo.

DISCUSSION

IGIV-treated subjects did not experience higher rates of renal failure, lung injury, or thrombotic events than the placebo group. There were no unexpected safety findings. IGIV was well tolerated throughout 18 months of treatment in subjects aged 50-89 years.

Naturally occurring autoantibodies against Aβ oligomers exhibited more beneficial effects in the treatment of mouse model of Alzheimer's disease than intravenous immunoglobulin

Alzheimer's disease (AD) is characterized by memory loss, intracellular neurofibrillary tangles, and extracellular plaque deposits composed of β-amyloid (Aβ). Previous reports showed that naturally occurring autoantibodies, such as intravenous immunoglobulin (IVIG), benefited patients with moderate-stage AD who carried an APOE-ε4 allele. However, the mechanism underlying the role of IVIG remains unclear. In this study, we identified naturally occurring autoantibodies against Aβ oligomers (NAbs-Aβo), which were purified by Aβ42 oligomer or Cibacron Blue affinity chromatography from IVIG and termed as Oli-NAbs and Blue-NAbs, respectively. Oli-NAbs and Blue-NAbs recognized Aβ42 oligomers or both Aβ40 and 42 oligomers, differently. Both antibodies inhibited Aβ42 aggregation and attenuated Aβ42-induced cytotoxicity. Compared with vehicles, Oli-NAbs, Blue-NAbs and IVIG significantly improved the memory and cognition, and reduced the soluble and oligomeric Aβ levels in APPswe/PS1dE9 transgenic mice. Further investigation showed that Blue-NAbs at increased doses effectively decreased plaque burden and insoluble Aβ levels, whereas Oli-NAbs significantly declined the microgliosis and astrogliosis, as well as the production of proinflammatory cytokines in vivo. Therefore, high levels of these antibodies against oligomeric Aβ40 or Aβ42 were required, correspondingly, to achieve the optimal effect. NAbs-Aβo could be condensed to a high concentration by affinity chromatography and its isolation from IVIG may not interfere with the normal function of conventional IVIG as its concentration is very low. Thus, the isolated NAbs-Aβo as an extra product of plasma required low cost and the enriched NAbs-Aβo may be more feasible than IVIG for the treatment of AD.

Autoantibodies in Alzheimer's disease: potential biomarkers, pathogenic roles, and therapeutic implications

Alzheimer’s disease (AD) is a prevalent and debilitating neurodegenerative disorder in the elderly. The etiology of AD has not been fully defined and currently there is no cure for this devastating disease. Compelling evidence suggests that the immune system plays a critical role in the pathophysiology of AD. Autoantibodies against a variety of molecules have been associated with AD. The roles of these autoantibodies in AD, however, are not well understood. This review attempts to summarize recent findings on these autoantibodies and explore their potential as diagnostic/ prognostic biomarkers for AD, their roles in the pathogenesis of AD, and their implications in the development of effective immunotherapies for AD.

Probabilistic Cost-Effectiveness Analysis of Vaccination for Mild or Moderate Alzheimer's Disease

BACKGROUND

Studies on the immunotherapy for Alzheimer's disease (AD) have increasingly gained attention since 1990s. However, there are pros (preventing of AD) and cons (incurred cost and side effects) regarding the administration of immunotherapy. Up to date, there has been lacking of economic evaluation for immunotherapy of AD. We aimed to assess the cost-effectiveness analysis of the vaccination for AD.

METHODS

A meta-analysis of randomized control trials after systemic review was conducted to evaluate the efficacy of the vaccine. A Markov decision model was constructed and applied to a 120,000-Taiwanese cohort aged ≥65 years. Person years and quality-adjusted life years (QALY) were computed between the vaccinated group and the the unvaccinated group. Economic evaluation was performed to calculate the incremental cost-effectiveness ratio (ICER) and cost-effectiveness acceptability curve (CEAC).

RESULTS

Vaccinated group gained an additional 0.84 life years and 0.56 QALYs over 10-years and an additional 0.35 life years and 0.282 QALYs over 5-years of follow-up. The vaccinated group dominated the unvaccinated group by ICER over 5-years of follow-up. The ICERs of 10-year follow-up for the vaccinated group against the unvaccinated group were $13,850 per QALY and $9,038 per life year gained. Given the threshold of $20,000 of willingness to pay (WTP), the CEAC showed the probability of being cost-effective for vaccination with QALY was 70.7% and 92% for life years gained after 10-years of follow-up. The corresponding figures were 87.3% for QALY and 93.5% for life years gained over 5-years follow-up.

CONCLUSION

The vaccination for AD was cost-effective in gaining QALY and life years compared with no vaccination, under the condition of a reasonable threshold of WTP.

Stress Granules Modulate SYK to Cause Microglial Cell Dysfunction in Alzheimer's Disease

Microglial cells in the brains of Alzheimer's patients are known to be recruited to amyloid-beta (Aβ) plaques where they exhibit an activated phenotype, but are defective for plaque removal by phagocytosis. In this study, we show that microglia stressed by exposure to sodium arsenite or Aβ(1–42) peptides or fibrils form extensive stress granules (SGs) to which the tyrosine kinase, SYK, is recruited. SYK enhances the formation of SGs, is active within the resulting SGs and stimulates the production of reactive oxygen and nitrogen species that are toxic to neuronal cells. This sequestration of SYK inhibits the ability of microglial cells to phagocytose Escherichia coli or Aβ fibrils. We find that aged microglial cells are more susceptible to the formation of SGs; and SGs containing SYK and phosphotyrosine are prevalent in the brains of patients with severe Alzheimer's disease. Phagocytic activity can be restored to stressed microglial cells by treatment with IgG, suggesting a mechanism to explain the therapeutic efficacy of intravenous IgG. These studies describe a mechanism by which stress, including exposure to Aβ, compromises the function of microglial cells in Alzheimer's disease and suggest approaches to restore activity to dysfunctional microglial cells.

•

Chronic stress promotes the formation of large, persistent stress granules in microglial cells.

•

SYK is recruited to stress granules, which promotes inflammatory responses and inhibits phagocytosis.

•

Phagocytic activity of stressed cells can be recovered by treatment with IgG.

Microglial cells in the brains of patients with Alzheimer's disease are activated, but are defective at phagocytosis of amyloid plaques. Activation and phagocytosis require the SYK tyrosine kinase. Chronic exposure to amyloid-beta promotes the formation of persistent stress granules to which active SYK binds and these are found in the brains of patients with severe Alzheimer's disease. This activation and sequestration of SYK promotes inflammation and inhibits phagocytosis. Phagocytic activity can be recovered by treatment with IgG, which causes a redistribution of SYK within the cell, suggesting potential therapeutic approaches to restoring microglial cell function to diseased or aged brains.

Identification of target antigens of naturally occurring autoantibodies in cerebrospinal fluid

Naturally occurring autoantibodies have natural physiologic functions related to normal cell processes. However, the repertoire of naturally occurring autoantibodies against neuronal antigens in CSF is unclear. The purpose of this study was to identify naturally occurring autoantibodies against neuronal antigens in CSF from patients with various neurologic diseases by proteomics-based analysis. The CSF samples were collected from 77 patients with various neurologic disorders. The antigen source for 2-dimensional immunoblotting was the SH-SY5Y human neuroblastoma cell line. There were 8 spots recognized in CSF from more than one-fourth of the 77 patients including all patient groups and these spots were recognized in intravenous immunoglobulin preparations. These antigen spots were identified as heat shock 105-kDa/110-kDa protein 1, isoform CRA_b, 78-kDa glucose-regulated protein, heat shock cognate 71-kDa protein, tubulin beta chain, vimentin (2 spots), and 60-kDa heat shock protein, mitochondrial; we could not identify the protein name corresponding to 1 of the 8 spots. In summary, there were 6 proteins identified that were main target antigens that reacted with naturally occurring autoantibodies in CSF from patients with varied neurologic disorders; the functions of autoantibodies against the identified antigens are unknown and may be clarified with further studies.

BIOLOGICAL SIGNIFICANCE

Naturally occurring autoantibodies may have important functions in tissue homeostasis. In this study, we identified 6 common target antigens that reacted with autoantibodies in cerebrospinal fluid (CSF) from patients, independent of disease type. These findings may clarify the importance of naturally occurring autoantibodies in CSF and the use of these antibodies potentially may be a novel therapy for various neurologic disorders.

Long-term treatment with active Aβ immunotherapy with CAD106 in mild Alzheimer's disease

Introduction

CAD106 is designed to stimulate amyloid-β (Aβ)-specific antibody responses while avoiding T-cell autoimmune responses. The CAD106 first-in-human study demonstrated a favorable safety profile and promising antibody response. We investigated long-term safety, tolerability and antibody response after repeated CAD106 injections.

Methods

Two phase IIa, 52-week, multicenter, randomized, double-blind, placebo-controlled core studies (2201; 2202) and two 66-week open-label extension studies (2201E; 2202E) were conducted in patients with mild Alzheimer’s disease (AD) aged 40 to 85 years. Patients were randomized to receive 150μg CAD106 or placebo given as three subcutaneous (2201) or subcutaneous/intramuscular (2202) injections, followed by four injections (150 μg CAD106; subcutaneous, 2201E1; intramuscular, 2202E1). Our primary objective was to evaluate the safety and tolerability of repeated injections, including monitoring cerebral magnetic resonance imaging scans, adverse events (AEs) and serious AEs (SAEs). Further objectives were to assess Aβ-specific antibody response in serum and Aβ-specific T-cell response (core only). Comparable Aβ-immunoglobulin G (IgG) exposure across studies supported pooled immune response assessments.

Results

Fifty-eight patients were randomized (CAD106, n = 47; placebo, n = 11). Baseline demographics and characteristics were balanced. Forty-five patients entered extension studies. AEs occurred in 74.5% of CAD106-treated patients versus 63.6% of placebo-treated patients (core), and 82.2% experienced AEs during extension studies. Most AEs were mild to moderate in severity, were not study medication-related and did not require discontinuation. SAEs occurred in 19.1% of CAD106-treated patients and 36.4% of placebo-treated patients (core). One patient (CAD106-treated; 2201) reported a possibly study drug-related SAE of intracerebral hemorrhage. Four patients met criteria for amyloid-related imaging abnormalities (ARIA) corresponding to microhemorrhages: one was CAD106-treated (2201), one placebo-treated (2202) and two open-label CAD106-treated. No ARIA corresponded to vasogenic edema. Two patients discontinued extension studies because of SAEs (rectal neoplasm and rapid AD progression, respectively). Thirty CAD106-treated patients (63.8%) were serological responders. Sustained Aβ-IgG titers and prolonged time to decline were observed in extensions versus core studies. Neither Aβ_1–6 nor Aβ_1–42 induced specific T-cell responses; however, positive control responses were consistently detected with the CAD106 carrier.

Conclusions

No unexpected safety findings or Aβ-specific T-cell responses support the CAD106 favorable tolerability profile. Long-term treatment-induced Aβ-specific antibody titers and prolonged time to decline indicate antibody exposure may increase with additional injections. CAD106 may be a valuable therapeutic option in AD.

Trial registration

ClinicalTrials.gov identifiers: NCT00733863, registered 8 August 2008; NCT00795418, registered 10 November 2008; NCT00956410, registered 10 August 2009; NCT01023685, registered 1 December 2009.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-015-0108-3) contains supplementary material, which is available to authorized users.

Kinetic analysis of IgG antibodies to beta-amyloid oligomers with surface plasmon resonance

Surface plasmon resonance was used to investigate the kinetics, affinity, and specificity of binding between anti-Aβ (beta-amyloid) IgG antibodies and oligomeric Aβ. Two factors were needed to accurately characterize the IgG binding kinetics. First, a bivalent model was necessary to properly fit the kinetic association and dissociation sensograms. Second, a high concentration of IgG was necessary to overcome a significant mass transport limitation that existed regardless of oligomer density on the sensor surface. Using high IgG concentrations and bivalent fits, consistent kinetic parameters were found at varying sensor surface ligand densities. A comparison of binding specificity, affinity, and kinetic flux between monoclonal and natural human anti-Aβ IgG antibodies revealed the following findings. First, monoclonal antibodies 6E10 and 4G8 single-site binding affinity is similar between Aβ oligomers and monomers. Second, natural human anti-Aβ IgG binding readily binds Aβ oligomers but does not bind monomers. Third, natural human anti-Aβ IgG binds Aβ oligomers with a higher affinity and kinetic flux than 6E10 and 4G8. Both the current analytical methodology and antibody binding profiles are important for advances in antibody drug development and kinetic biomarker applications for Alzheimer's disease.

Anti-aβ oligomer IgG and surface sialic acid in intravenous immunoglobulin: measurement and correlation with clinical outcomes in Alzheimer's disease treatment

The fraction of IgG antibodies with anti-oligomeric Aβ affinity and surface sialic acid was compared between Octagam and Gammagard intravenous immunoglobulin (IVIG) using two complementary surface plasmon resonance methods. These comparisons were performed to identify if an elevated fraction existed in Gammagard, which reported small putative benefits in a recent Phase III clinical trial for Alzheimer’s Disease. The fraction of anti-oligomeric Aβ IgG was found to be higher in Octagam, for which no cognitive benefits were reported. The fraction and location of surface-accessible sialic acid in the Fab domain was found to be similar between Gammagard and Octagam. These findings indicate that anti-oligomeric Aβ IgG and total surface sialic acid alone cannot account for reported clinical differences in the two IVIG products. A combined analysis of sialic acid in anti-oligomeric Aβ IgG did reveal a notable finding that this subgroup exhibited a high degree of surface sialic acid lacking the conventional α2,6 linkage. These results demonstrate that the IVIG antibodies used to engage oligomeric Aβ in both Gammagard and Octagam clinical trials did not possess α2,6-linked surface sialic acid at the time of administration. Anti-oligomeric Aβ IgG with α2,6 linkages remains untested as an AD treatment.

Longitudinal effects of intravenous immunoglobulin on Alzheimer's cerebrospinal fluid proteome

Intravenous immunoglobulin (IVIg) therapy has shown promise in the treatment of Alzheimer's disease (AD). In this study, serial cerebrospinal fluid (CSF) samples from a group of subjects with AD undergoing IVIg immunotherapy are analyzed to identify IVIg-related changes. CSF samples from eight subjects were collected before therapy, after 6 months of therapy, and after a 3-month drug washout period. Samples were analyzed using a gel-based proteomics strategy and IVIg-related changes were determined by gel spot percent volumes. An initial assessment of the data revealed consistent and considerable change in 69 spots. A statistical analysis revealed 79 protein spots with a significant change after 6 months; furthermore, in a subset of these (25), the percent volume change was either maintained or reversed in the washout samples. The proteins that showed a significant change during IVIg therapy, including Ig molecules, gelsolin, transferrin, and transthyretin, have been previously implicated in AD. This study provides preliminary findings regarding a group of CSF proteins that may be associated with the treatment of AD, as well as the potential use of IVIg as an AD immunotherapy.

Role of cerebrospinal fluid biomarkers in clinical trials for Alzheimer's disease modifying therapies

Until now, a disease-modifying therapy (DMT) that has an ability to slow or arrest Alzheimer's disease (AD) progression has not been developed, and all clinical trials involving AD patients enrolled by clinical assessment alone also have not been successful. Given the growing consensus that the DMT is likely to require treatment initiation well before full-blown dementia emerges, the early detection of AD will provide opportunities to successfully identify new drugs that slow the course of AD pathology. Recent advances in early detection of AD and prediction of progression of the disease using various biomarkers, including cerebrospinal fluid (CSF) Aβ_1-42, total tau and p-tau₁₈₁ levels, and imagining biomarkers, are now being actively integrated into the designs of AD clinical trials. In terms of therapeutic mechanisms, monitoring these markers may be helpful for go/no-go decision making as well as surrogate markers for disease severity or progression. Furthermore, CSF biomarkers can be used as a tool to enrich patients for clinical trials with prospect of increasing statistical power and reducing costs in drug development. However, the standardization of technical aspects of analysis of these biomarkers is an essential prerequisite to the clinical uses. To accomplish this, global efforts are underway to standardize CSF biomarker measurements and a quality control program supported by the Alzheimer's Association. The current review summarizes therapeutic targets of developing drugs in AD pathophysiology, and provides the most recent advances in the