Effects of human intravenous immunoglobulin on amyloid pathology and neuroinflammation in a mouse model 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.

Antibody-Mediated Clearance of Brain Amyloid-β: Mechanisms of Action, Effects of Natural and Monoclonal Anti-Aβ Antibodies, and Downstream Effects

Immunotherapeutic efforts to slow the clinical progression of Alzheimer's disease (AD) by lowering brain amyloid-β (Aβ) have included Aβ vaccination, intravenous immunoglobulin (IVIG) products, and anti-Aβ monoclonal antibodies. Neither Aβ vaccination nor IVIG slowed disease progression. Despite conflicting phase III results, the monoclonal antibody Aducanumab received Food and Drug Administration (FDA) approval for treatment of AD in June 2021. The only treatments unequivocally demonstrated to slow AD progression to date are the monoclonal antibodies Lecanemab and Donanemab. Lecanemab received FDA approval in January 2023 based on phase II results showing lowering of PET-detectable Aβ; phase III results released at that time indicated slowing of disease progression. Topline results released in May 2023 for Donanemab's phase III trial revealed that primary and secondary end points had been met. Antibody binding to Aβ facilitates its clearance from the brain via multiple mechanisms including promoting its microglial phagocytosis, activating complement, dissolving fibrillar Aβ, and binding of antibody-Aβ complexes to blood-brain barrier receptors. Antibody binding to Aβ in peripheral blood may also promote cerebral efflux of Aβ by a peripheral sink mechanism. According to the amyloid hypothesis, for Aβ targeting to slow AD progression, it must decrease downstream neuropathological processes including tau aggregation and phosphorylation and (possibly) inflammation and oxidative stress. This review discusses antibody-mediated mechanisms of Aβ clearance, findings in AD trials involving Aβ vaccination, IVIG, and anti-Aβ monoclonal antibodies, downstream effects reported in those trials, and approaches which might improve the Aβ-clearing ability of monoclonal antibodies.

A Comparison Between 1 Day versus 7 Days of Sepsis in Mice with the Experiments on LPS-Activated Macrophages Support the Use of Intravenous Immunoglobulin for Sepsis Attenuation

Background

Because survival and death after sepsis are partly due to a proper immune adaptation and immune dysregulation, respectively, survivors and moribund mice after cecal ligation and puncture (CLP) sepsis surgery and in vitro macrophage experiments were explored.

Methods

Characteristics of mice at 1-day and 7-days post-CLP, the representative of moribund mice (an innate immune hyper-responsiveness) and survivors (a successful control on innate immunity), respectively. In parallel, soluble heat aggregated immunoglobulin (sHA-Ig), a representative of immune complex, was tested in lipopolysaccharide (LPS)-activated macrophages together with a test of intravenous immunoglobulin (IVIG), a molecule of adaptive immunity, on CLP sepsis mice.

Results

Except for a slight increase in alanine transaminase (liver injury), IL-10, endotoxemia, and gut leakage (FITC-dextran assay), most of the parameters in survivors (7-days post-CLP) were normalized, with enhanced adaptive immunity, including serum immunoglobulin (using serum protein electrophoresis) and activated immune cells in spleens (flow cytometry analysis). The addition of sHA-Ig in LPS-activated macrophages reduced supernatant cytokines, cell energy (extracellular flux analysis), reactive oxygen species (ROS), several cell activities (proteomic analysis), and Fc gamma receptors (FcgRs) expression. The loss of anti-inflammatory effect of sHA-Ig in LPS-activated macrophages from mice with a deficiency on Fc gamma receptor IIb (FcgRIIb-/-), the only inhibitory signaling of FcgRs family, when compared with wild-type macrophages, implying the FcgRIIb-dependent mechanism. Moreover, IVIG attenuated sepsis severity in CLP mice as evaluated by serum creatinine, liver enzyme (alanine transaminase), serum cytokines, spleen apoptosis, and abundance of dendritic cells in the spleen (24-h post-CLP) and survival analysis.

Conclusion

Immunoglobulin attenuated LPS-activated macrophages, partly, through the reduced cell energy of macrophages and might play a role in sepsis immune hyper-responsiveness. Despite the debate over IVIG’s use in sepsis, IVIG might be beneficial in sepsis with certain conditions.

Clinically approved IVIg delivered to the hippocampus with focused ultrasound promotes neurogenesis in a model of Alzheimer's disease

Preclinical and clinical data support the use of focused ultrasound (FUS), in the presence of intravenously injected microbubbles, to safely and transiently increase the permeability of the blood-brain barrier (BBB). FUS-induced BBB permeability has been shown to enhance the bioavailability of administered intravenous therapeutics to the brain. Ideal therapeutics candidates for this mode of delivery are those capable of inducing benefits peripherally following intravenous injection and in the brain at FUS-targeted areas. In Alzheimer's disease, intravenous immunoglobulin (IVIg), a fractionated human blood product containing polyclonal antibodies, act as immunomodulator peripherally and centrally, and it can reduce amyloid pathology in the brain. Using the TgCRND8 mouse model of amyloidosis, we tested whether FUS can improve the delivery of IVIg, administered intravenously (0.4 g/kg), to the hippocampus and reach an effective dose to reduce amyloid plaque pathology and promote neurogenesis. Our results show that FUS-induced BBB permeability is required to deliver a significant amount of IVIg (489 ng/mg) to the targeted hippocampus of TgCRN8 mice. Two IVIg-FUS treatments, administered at days 1 and 8, significantly increased hippocampal neurogenesis by 4-, 3-, and 1.5-fold in comparison to saline, IVIg alone, and FUS alone, respectively. Amyloid plaque pathology was significantly reduced in all treatment groups: IVIg alone, FUS alone, and IVIg-FUS. Putative factors promoting neurogenesis in response to IVIg-FUS include the down-regulation of the proinflammatory cytokine TNF-α in the hippocampus. In summary, FUS was required to deliver an effective dose of IVIg to promote hippocampal neurogenesis and modulate the inflammatory milieu.

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.

Long-term human IgG treatment improves heart and muscle function in a mouse model of Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disease caused by mutations in the dystrophin gene, which leads to structural instability of the dystrophin-glycoprotein-complex with subsequent muscle degeneration. In addition, muscle inflammation has been implicated in disease progression and therapeutically addressed with glucocorticosteroids. These have numerous adverse effects. Treatment with human immunoglobulin G (IgG) improved clinical and para-clinical parameters in the early disease phase in the well-established mdx mouse model. The aim of the present study was to confirm the efficacy of IgG in a long-term pre-clinical study in mdx mice.

METHODS

IgG (2 g/kg body weight) or NaCl solution as control was administered monthly over 18 months by intraperitoneal injection in mdx mice beginning at 3 weeks of age. Several clinical outcome measures including endurance, muscle strength, and echocardiography were assessed. After 18 months, the animals were sacrificed, blood was collected for analysis, and muscle samples were obtained for ex vivo muscle contraction tests, quantitative PCR, and histology.

RESULTS

IgG significantly improved the daily voluntary running performance (1.9 m more total daily running distance, P < 0.0001) and slowed the decrease in grip strength by 0.1 mN, (P = 0.018). IgG reduced fatigability of the diaphragm (improved ratio to maximum force by 0.09 ± 0.04, P = 0.044), but specific tetanic force remained unchanged in the ex vivo muscle contraction test. Cardiac function was significantly better after IgG, especially fractional area shortening (P = 0.012). These results were accompanied by a reduction in cardiac fibrosis and the infiltration of T cells (P = 0.0002) and macrophages (P = 0.0027). In addition, treatment with IgG resulted in a significant reduction of the infiltration of T cells (P ≤ 0.036) in the diaphragm, gastrocnemius, quadriceps, and a similar trend in tibialis anterior and macrophages (P ≤ 0.045) in gastrocnemius, quadriceps, tibialis anterior, and a similar trend in the diaphragm, as well as a decrease in myopathic changes as reflected by a reduced central nuclear index in the diaphragm, tibialis anterior, and quadriceps (P ≤ 0.002 in all).

CONCLUSIONS

The present study underscores the importance of an inflammatory contribution to the disease progression of DMD. The data demonstrate the long-term efficacy of IgG in the mdx mouse. IgG is well tolerated by humans and could preferentially complement gene therapy in DMD. The data call for a clinical trial with IgG in DMD.

PPARβ/δ-agonist GW0742 ameliorates dysfunction in fatty acid oxidation in PSEN1ΔE9 astrocytes

Astrocytes are the gatekeepers of neuronal energy supply. In neurodegenerative diseases, bioenergetics demand increases and becomes reliant upon fatty acid oxidation as a source of energy. Defective fatty acid oxidation and mitochondrial dysfunctions correlate with hippocampal neurodegeneration and memory deficits in Alzheimer's disease (AD), but it is unclear whether energy metabolism can be targeted to prevent or treat the disease. Here we show for the first time an impairment in fatty acid oxidation in human astrocytes derived from induced pluripotent stem cells of AD patients. The impairment was corrected by treatment with a synthetic peroxisome proliferator activated receptor delta (PPARβ/δ) agonist GW0742 which acts to regulate an array of genes governing cellular metabolism. GW0742 enhanced the expression of CPT1a, the gene encoding for a rate-limiting enzyme of fatty acid oxidation. Similarly, treatment of a mouse model of AD, the APP/PS1-mice, with GW0742 increased the expression of Cpt1a and concomitantly reversed memory deficits in a fear conditioning test. Although the GW0742-treated mice did not show altered astrocytic glial fibrillary acidic protein-immunoreactivity or reduction in amyloid beta (Aβ) load, GW0742 treatment increased hippocampal neurogenesis and enhanced neuronal differentiation of neuronal progenitor cells. Furthermore, GW0742 prevented Aβ-induced impairment of long-term potentiation in hippocampal slices. Collectively, these data suggest that PPARβ/δ-agonism alleviates AD related deficits through increasing fatty acid oxidation in astrocytes and improves cognition in a transgenic mouse model of AD.

Candidate SNP Markers of Familial and Sporadic Alzheimer's Diseases Are Predicted by a Significant Change in the Affinity of TATA-Binding Protein for Human Gene Promoters

While year after year, conditions, quality, and duration of human lives have been improving due to the progress in science, technology, education, and medicine, only eight diseases have been increasing in prevalence and shortening human lives because of premature deaths according to the retrospective official review on the state of US health, 1990-2010. These diseases are kidney cancer, chronic kidney diseases, liver cancer, diabetes, drug addiction, poisoning cases, consequences of falls, and Alzheimer's disease (AD) as one of the leading pathologies. There are familial AD of hereditary nature (~4% of cases) and sporadic AD of unclear etiology (remaining ~96% of cases; i.e., non-familial AD). Therefore, sporadic AD is no longer a purely medical problem, but rather a social challenge when someone asks oneself: “What can I do in my own adulthood to reduce the risk of sporadic AD at my old age to save the years of my lifespan from the destruction caused by it?” Here, we combine two computational approaches for regulatory SNPs: Web service SNP_TATA_Comparator for sequence analysis and a PubMed-based keyword search for articles on the biochemical markers of diseases. Our purpose was to try to find answers to the question: “What can be done in adulthood to reduce the risk of sporadic AD in old age to prevent the lifespan reduction caused by it?” As a result, we found 89 candidate SNP markers of familial and sporadic AD (e.g., rs562962093 is associated with sporadic AD in the elderly as a complication of stroke in adulthood, where natural marine diets can reduce risks of both diseases in case of the minor allele of this SNP). In addition, rs768454929, and rs761695685 correlate with sporadic AD as a comorbidity of short stature, where maximizing stature in childhood and adolescence as an integral indicator of health can minimize (or even eliminate) the risk of sporadic AD in the elderly. After validation by clinical protocols, these candidate SNP markers may become interesting to the general population [may help to choose a lifestyle (in childhood, adolescence, and adulthood) that can reduce the risks of sporadic AD, its comorbidities, and complications in the elderly].

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.

Effective anti-Alzheimer Aβ therapy involves depletion of specific Aβ oligomer subtypes

BACKGROUND

Recent studies have implicated specific assembly subtypes of β-amyloid (Aβ) peptide, specifically soluble oligomers (soAβ) as disease-relevant structures that may underlie memory loss in Alzheimer disease. Removing existing soluble and insoluble Aβ assemblies is thought to be essential for any attempt at stabilizing brain function and slowing cognitive decline in Alzheimer disease. IV immunoglobulin (IVIg) therapies have been shown to contain naturally occurring polyclonal antibodies that recognize conformational neoepitopes of soluble or insoluble Aβ assemblies including soAβ. These naturally occurring polyclonal antibodies have been suggested to underlie the apparent clinical benefits of IVIg. However, direct evidence linking anti-Aβ antibodies to the clinical bioactivity of IVIg has been lacking.

METHODS

Five-month-old female Dutch APP E693Q mice were treated for 3 months with neat IVIg or with IVIg that had been affinity-depleted over immobilized Aβ conformers in 1 of 2 assembly states. Memory was assessed in a battery of tests followed by quantification of brain soAβ levels using standard anti-soAβ antibodies.

RESULTS

We provide evidence that NU4-type soAβ (NU4-soAβ) assemblies accumulate in the brains of Dutch APP E693Q mice and are associated with defects in memory, even in the absence of insoluble Aβ plaques. Memory benefits were associated with depletion from APP E693Q mouse brain of NU4-soAβ and A11-soAβ but not OC-type fibrillar Aβ oligomers.

CONCLUSIONS

We propose that targeting of specific soAβ assembly subtypes may be an important consideration in the therapeutic and/or prophylactic benefit of anti-Aβ antibody drugs.

Immunotherapies in Alzheimer's disease: Too much, too little, too late or off-target?

Years of research have highlighted the importance of the immune system in Alzheimer's disease (AD), a system that, if manipulated during strategic time windows, could potentially be tackled to treat this disorder. However, to minimize adverse effects, it is essential to first grasp which exact aspect of it may be targeted. Several clues have been collected over the years regarding specific immune players strongly modulated during different stages of AD progression. However, the inherent complexity of the immune system as well as conflicting data make it quite challenging to pinpoint a specific immune target in AD. In this review, we discuss immune-related abnormalities observed in the periphery as well as in the brain of AD patients, in relation to known risk factors of AD such as genetics, type-2 diabetes or obesity, aging, physical inactivity and hypertension. Although not investigated yet in clinical trials, C5 complement system component, CD40/CD40L interactions and the CXCR2 pathway are altered in AD patients and may represent potential therapeutic targets. Immunotherapies tested in a clinical context, those aiming to attenuate the innate immune response and those used to facilitate the removal of pathological proteins, are further discussed to try and understand the causes of the limited success reached. The prevailing eagerness to move basic research data to clinic should not overshadow the fact that a careful preclinical characterization of a drug is still required to ultimately improve the chance of clinical success. Finally, specific elements to consider prior to initiate large-scale trials are highlighted and include the replication of preclinical data, the use of small-scale human studies, the sub-typing of AD patients and the determination of pharmacokinetic and pharmacodynamics parameters such as brain bioavailability and target engagement.

Tackling amyloidogenesis in Alzheimer's disease with A2V variants of Amyloid-β

We developed a novel therapeutic strategy for Alzheimer’s disease (AD) exploiting the properties of a natural variant of Amyloid-β (Aβ) carrying the A2V substitution, which protects heterozygous carriers from AD by its ability to interact with wild-type Aβ, hindering conformational changes and assembly thereof. As prototypic compound we designed a six-mer mutated peptide (Aβ1-6_A2V), linked to the HIV-related TAT protein, which is widely used for brain delivery and cell membrane penetration of drugs. The resulting molecule [Aβ1-6_A2VTAT(D)] revealed strong anti-amyloidogenic effects in vitro and protected human neuroblastoma cells from Aβ toxicity. Preclinical studies in AD mouse models showed that short-term treatment with Aβ1-6_A2VTAT(D) inhibits Aβ aggregation and cerebral amyloid deposition, but a long treatment schedule unexpectedly increases amyloid burden, although preventing cognitive deterioration. Our data support the view that the Aβ_A2V-based strategy can be successfully used for the development of treatments for AD, as suggested by the natural protection against the disease in human A2V heterozygous carriers. The undesirable outcome of the prolonged treatment with Aβ1-6_A2VTAT(D) was likely due to the TAT intrinsic attitude to increase Aβ production, avidly bind amyloid and boost its seeding activity, warning against the use of the TAT carrier in the design of AD therapeutics.

Deletion of Nuclear Factor kappa B p50 Subunit Decreases Inflammatory Response and Mildly Protects Neurons from Transient Forebrain Ischemia-induced Damage

Transient forebrain ischemia induces delayed death of the hippocampal pyramidal neurons, particularly in the CA2 and medial CA1 area. Early pharmacological inhibition of inflammatory response can ameliorate neuronal death, but it also inhibits processes leading to tissue regeneration. Therefore, research efforts are now directed to modulation of post-ischemic inflammation, with the aim to promote beneficial effects of inflammation and limit adverse effects. Transcription factor NF-κB plays a key role in the inflammation and cell survival/apoptosis pathways. In the brain, NF-κB is predominantly found in the form of a heterodimer of p65 (RelA) and p50 subunit, where p65 has a transactivation domain while p50 is chiefly involved in DNA binding. In this study, we subjected middle-aged Nfkb1 knockout mice (lacking p50 subunit) and wild-type controls of both sexs to 17 min of transient forebrain ischemia and assessed mouse performance in a panel of behavioral tests after two weeks of post-operative recovery. We found that ischemia failed to induce clear memory and motor deficits, but affected spontaneous locomotion in genotype- and sex-specific way. We also show that both the lack of the NF-κB p50 subunit and female sex independently protected CA2 hippocampal neurons from ischemia-induced cell death. Additionally, the NF-κB p50 subunit deficiency significantly reduced ischemia-induced microgliosis, astrogliosis, and neurogenesis. Lower levels of hippocampal microgliosis significantly correlated with faster spatial learning. We conclude that NF-κB regulates the outcome of transient forebrain ischemia in middle-aged subjects in a sex-specific way, having an impact not only on neuronal death but also specific inflammatory responses and neurogenesis.

Paeoniflorin Atttenuates Amyloidogenesis and the Inflammatory Responses in a Transgenic Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is associated with the inflammatory response in response to amyloid β-peptide (Aβ). Previous studies have suggested that paeoniflorin (PF) shows anti-inflammatory and neuroprotective effects in inflammation-related diseases. However, the impacts of PF on AD have not been investigated. In the present study, we showed that a 4-week treatment with PF could significantly inhibit Aβ burden, Aβ-induced over activation of astrocytes and microglia, downregulation of proinflammatory cytokines, and upregulation of anti-inflammatory cytokines in the brain. In addition, we demonstrated that chronic treatment with PF inhibited the activation of glycogen synthase kinase 3β (GSK-3β) and reversed neuroinflammtory-induced activation of nuclear factor-kappa B (NF-κB) signaling pathways. Moreover, PF exerted inhibitory effects on NALP3 inflammasome, caspase-1, and IL-1β. Collectively, in the present study, we demonstrated that PF exhibits neuroprotective effects in amyloid precursor protein (APP) and presenilin 1 (PS1) double-transgenic (APP/PS1) mice via inhibiting neuroinflammation mediated by the GSK-3β and NF-κB signaling pathways and nucleotide-binding domain-like receptor protein 3 inflammasome. Thus, these results suggest that PF might be useful to intervene in development or progression of neurodegeneration in AD through its anti-inflammatory and anti-amyloidogenic effects.

Intravenous immunoglobulin reduces tau pathology and preserves neuroplastic gene expression in the 3xTg mouse model of Alzheimer's disease

Despite recent negative results of the Gammaglobulin Alzheimer's Partnership (GAP) trial, the good tolerability to intravenous immunoglobulin (IVIG) and its potential benefit for patient subpopulations have highlighted the importance of understanding IVIG's mechanism of action. IVIG contains antibodies to amyloid suggesting an amyloid clearance mechanism. However, the suboptimal results of the amyloid immunotherapy trials suggest an additional mechanism. Therefore, we tested whether IVIG alters the expression of tau neurofibrillary tangle (NFT)-like deposits within hippocampal CA1 neurons of the 3xTg mouse model of AD. Three-month-old mice were treated intravenously with IVIG (10%, 400 mg/kg) or placebo (10% BSA/saline) every two weeks for either three or six months. At sacrifice, plasma was isolated for gene expression profiling and brains were processed for immunohistochemistry using the AT-180 antibody, which recognizes hyperphosphorylated tau in NFTs. Stereologic analysis of CA1 neurons following three months of treatment revealed no difference in AT-180+ neuron number but a significant 15-20% decrease in AT-180 intraneuronal optical density with IVIG compared to placebo. By contrast, the number of AT-180+ CA1 neurons was reduced by 25-30% following six months of IVIG treatment compared to placebo. Expression profiling studies showed that IVIG treatment resulted in a significant 40-50% increase in plasma levels of genes regulating neuronal cytoskeletal plasticity function and calcium-mediated signaling compared to placebo. Moreover, several transcripts encoding protein phosphatase subunits were 40-50% higher in IVIG-treated mice. Hence, IVIG reduces hippocampal NFT pathology in the 3xTg mouse through a mechanism that may involve preservation of neuronal plasticity and tau phosphorylation homeostasis.

Should development of Alzheimer's disease-specific intravenous immunoglobulin be considered?

Recent phase II and III studies with intravenous immunoglobulin (IVIG) in patients with Alzheimer's disease (AD) did not find evidence for the slowing of AD progression compared to placebo-treated patients, in contrast to encouraging results in pilot studies. An additional phase III trial is ongoing. If negative results are found, then further AD studies with IVIG are unlikely unless a manufacturer opts for a trial with high-dose IVIG, which would increase its anti-inflammatory effects but also the risk for adverse events. An alternative approach could be an AD-specific IVIG, supplementing IVIG with higher concentrations of selected antibodies purified from it or produced via recombinant polyclonal antibody technology. These antibodies could include those to amyloid-beta (Aβ, tau protein, inflammatory cytokines, complement activation proteins, and the receptor for advanced glycation end products. IgG fragment crystallizable (Fc) fragments containing terminal sialic acid could be added to increase anti-inflammatory effects. While this product might be more effective in slowing AD clinical progression than current IVIG, there are difficulties with this approach. Preclinical studies would be required to determine which of the antibodies of interest for supplementing current IVIG (for example, antibodies to phosphorylated or oligomeric tau) are actually present (and, therefore, available for purification) in IVIG, and the effects of the product in mouse models of AD. An Investigational New Drug application for an AD-specific IVIG would require United States Food and Drug Administration approval. If the drug would be found to benefit AD patients, meeting the increased demand for IVIG would be challenging.

Association of CD33 polymorphism rs3865444 with Alzheimer's disease pathology and CD33 expression in human cerebral cortex

Recent findings identified the minor A allele present in the single-nucleotide polymorphism rs3865444 in the CD33 gene as being associated with the reduced risk of developing Alzheimer's disease (AD). CD33 (Siglec-3) is an immune function protein with anti-inflammatory signaling, cell adhesion, and endocytosis functions with sialic acid-modified proteins or lipids as ligands. Its involvement in AD pathologic mechanisms is still unclear; so, the goal of this study was to investigate if the rs3865444 polymorphism affects the development of AD pathology and the expression of CD33 messenger RNA (mRNA) and protein. For this study, we used DNA from 96 nondemented (ND) and 97 AD neuropathologically diagnosed cases to identify the different rs3865444 alleles and correlate with different measures of AD pathology. Using semiquantitative histologic measures of plaque and tangle pathology, we saw no significant differences between the different genotypes within these disease groups. However, increased expression of CD33 mRNA was associated with increasing AD pathology in temporal cortex brain samples. We also showed that cases with A/A alleles had reduced levels of CD33 protein in temporal cortex but increased levels of the microglia protein IBA-1. Using immunohistochemistry on temporal cortex sections, CD33 was selectively localized to microglia, with greater expression in activated microglia. The factors causing increased CD33 expression by microglia in brain are still unclear, although both genetic and disease factors are involved. Treatment of human microglia isolated from autopsy brains with amyloid-beta peptide and a range of other inflammatory activating agents resulted in reduced CD33 mRNA and protein levels.

Behavioral and neuropathological consequences of transient global ischemia in APP/PS1 Alzheimer model mice

Alzheimer's disease (AD) typically manifests in elderly people with several co-morbidities, especially cardiovascular, whereas transgenic mouse models of this disease usually employ middle-aged animals that have a good general health status. To assess the combined effect of compromised cerebral blood circulation and brain amyloid pathology we induced transient (17min) global ischemia (TGI) to young adult APPswe/PS1dE9 (APdE9) mice modeling AD amyloid pathology, and assessed the outcome on behavior two weeks and on histopathology five weeks after the ischemic insult. Ischemic injury resulted in reduced motor coordination and impaired spatial learning and memory. Neuropathological examination revealed circumscribed sites of neuronal loss in ischemic mice, including hippocampal CA2, lateral CA3 and medial CA1 pyramidal cell layer, and superficial layers of cortical patches. Notably, Fluoro-Jade staining revealed dying neurons as late as five weeks after the initial insult, and staining for active microglia and astrocytes confirmed the presence of inflammatory reaction. The extent of neuronal loss in CA2 and CA1 correlated significantly with impairment in spatial memory. There was no genotype difference in either behavioral or neuropathological consequences of TGI. However, the post-operative survival of transgenic animals was greatly reduced compared to wild type animals. APdE9 mice at a pre-plaque age appear to be more sensitive than wild-type mice to TGI in terms of post-operative recovery but the surviving APdE9 mice do not display more severe neurological deficits than wild-type mice.

Intravenous immunoglobulin (IVIG) treatment exerts antioxidant and neuropreservatory effects in preclinical models of Alzheimer's disease

Intravenous immunoglobulin (IVIG) has shown limited promise so far in human clinical studies on Alzheimer's disease (AD), yet overwhelmingly positive preclinical work in animals and human brain cultures support the notion that the therapy remains potentially efficacious. Here, we elaborate on IVIG neuropreservation by demonstrating that IVIG protects human primary neurons against oxidative stress in vitro and that IVIG preserves antioxidant defense mechanisms in vivo. Based on these results, we propose the following translational impact: If the dosage and treatment conditions are adequately optimized, then IVIG treatment could play a significant role in preventing and/or delaying the progression of neurodegenerative diseases, such as AD. We suggest that IVIG warrants further investigation to fully exploit its potential as an anti-oxidant, neuroprotective and synapto-protecting agent.

Immunomodulation and AD--down but not out

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and is the most common cause of dementia in the elderly. Interventions that remove existing fibrillar and oligomeric amyloid-β (Aβ) are believed to be essential for the success of any attempt at stabilization of brain function and mitigation of cognitive decline. Many of these strategies have focused on Aβ vaccination and administration of anti-Aβ antibodies. Both active and passive immunotherapies have been successful in mouse models, but both have had limited effect in clinical trials. Intravenous immunoglobulin (IVIG) has been proposed as a potential treatment for AD following evidence for behavioral benefit in AD models and cognitive benefit in early phase 1 and phase 2 clinical trials. A phase 3 trial IVIG trial failed to meet its primary outcomes. While there was a statistically significant benefit in moderate stage AD patients who carried an APOE ε4 allele, this stabilization of cognition was evident only on neuropsychological examination. No benefit on activities of daily living was evident, therefore failing to qualify AD as a new indication for IVIG. Identifying the biologically active component (s) responsible for the neuropsychological benefit in APOE ε4-positive AD patients could enable the development of a compound with greater potency that would qualify for FDA (US Food and Drug Administration) registration.

Clinical trials of intravenous immunoglobulin for Alzheimer's disease

The human polyclonal IgG antibody preparation known as Intravenous Immunoglobulin (IVIG) has been under study as a potential treatment for Alzheimer's disease (AD) since 2002. Preclinical and clinical studies have shown that IVIG has anti-amyloid and immune modulatory properties relevant to treating neurodegenerative disorders. In early stage AD clinical trials, IVIG was found to reduce cognitive decline and increase brain glucose metabolism. Unfortunately, IVIG failed to meet primary outcome objectives in the North American Phase 3 clinical trial in mild to moderate AD. However, positive cognitive signals were observed in pre-planned subgroup analyses among APOE-ε4 carriers and moderately impaired AD patients. Biomarker studies revealed dose dependent increases in plasma and CSF immunoglobulins and decreases in beta amyloid-42 levels. In addition, IVIG treatment was generally safe and well-tolerated. These findings suggest that naturally occurring human anti-amyloid antibodies may play a physiologic role in the clearance of aggregated amyloid proteins. While the results of clinical trials to date do not provide support for the use of IVIG to treat AD at the doses tested, additional studies of IVIG's mechanisms are warranted and may guide the development of more effective therapies for AD in the future.

Susceptibility to focal and global brain ischemia of Alzheimer mice displaying aβ deposits: effect of immunoglobulin

Cerebral ischemia is a risk factor for Alzheimer's disease (AD). Moreover, recent evidence indicates that it is a two-way street as the incidence rate of stroke is significantly higher in AD patients than those without the disease. Here we investigated the interaction of ischemic brain insults and AD in 9-month-old ApdE9 mice, which show full-blown accumulation of Aβ deposits and microgliosis in the brain. Permanent occlusion of the middle cerebral artery (pMCAo) resulted in 36% larger infarct in ApdE9 mice compared to their wild-type (wt) controls. This was not due to differences in endothelium-dependent vascular reactivity. Treatment with human intravenous immunoglobulin (IVIG) reduced the infarct volumes and abolished the increased vulnerability of ApdE9 mice to pMCAo induced brain ischemia. When the mice were exposed to global brain ischemia (GI), an insult of hippocampal cells, ApdE9 mice showed increased neuronal loss in CA2 and CA3 subregions compared to their wt controls. GI was associated with increased microgliosis, astrogliosis, infiltration of blood-derived monocytic cells, and neurogenesis without clear differences between the genotypes. IVIG treatment prevented the GI-induced neuron loss in hippocampal CA1 and CA3 regions in ApdE9 mice. IVIG treatment increased microgliosis in wt but not in ApdE9 mice. Finally, GI induced 60% reduction in the hippocampal Aβ burden in ApdE9 mice, which was not affected by IVIG treatment. The results indicate that the AD pathology with Aβ deposits and microgliosis increases ischemic vulnerability in various brain areas. Moreover, IVIG treatment may be beneficial especially in patients suffering from both acute ischemic insult and AD.

IVIg protects the 3xTg-AD mouse model of Alzheimer's disease from memory deficit and Aβ pathology

Background

Intravenous immunoglobulin (IVIg) is currently in clinical study for Alzheimer’s disease (AD). However, preclinical investigations are required to better understand AD-relevant outcomes of IVIg treatment and develop replacement therapies in case of unsustainable supply.

Methods

We investigated the effects of IVIg in the 3xTg-AD mouse model, which reproduces both Aβ and tau pathologies. Mice were injected twice weekly with 1.5 g/kg IVIg for 1 or 3 months.

Results

IVIg induced a modest but significant improvement in memory in the novel object recognition test and attenuated anxiety-like behavior in 3xTg-AD mice. We observed a correction of immunologic defects present in 3xTg-AD mice (−22% CD4/CD8 blood ratio; −17% IL-5/IL-10 ratio in the cortex) and a modulation of CX3CR1⁺ cell population (−13% in the bone marrow). IVIg treatment led to limited effects on tau pathology but resulted in a 22% reduction of the soluble Aβ42/Aβ40 ratio and a 60% decrease in concentrations of 56 kDa Aβ oligomers (Aβ*56).

Conclusion

The memory-enhancing effect of IVIg reported here suggests that Aβ oligomers, effector T cells and the fractalkine pathway are potential pharmacological targets of IVIg in AD.

Interpreting Alzheimer's disease clinical trials in light of the effects on amyloid-β

The failure of several potential Alzheimer’s disease therapeutics in mid- to late-stage clinical development has provoked significant discussion regarding the validity of the amyloid hypothesis. In this review, we propose a minimum criterion of 25% for amyloid-β (Aβ) lowering to achieve clinically meaningful slowing of disease progression. This criterion is based on genetic, risk factor, clinical and preclinical studies. We then compare this minimum criterion with the degree of Aβ lowering produced by the potential therapies that have failed in clinical trials. If the proposed minimum Aβ lowering criterion is used, then the amyloid hypothesis has yet to be adequately tested in the clinic. Therefore, we believe that the amyloid hypothesis remains valid and remains to be confirmed or refuted in future clinical trials.

Compound danshen tablet ameliorated aβ25-35-induced spatial memory impairment in mice via rescuing imbalance between cytokines and neurotrophins

Background

Compound Danshen Tablet (CDT), a Traditional Chinese Medicine, has recently been reported to improve spatial cognition in a rat model of Alzheimer’s disease. However, in vivo neuroprotective mechanism of the CDT in models of spatial memory impairment is not yet evaluated. The present study is aimed to elucidate the cellular mechanism of CDT on Aβ_25-35-induced cognitive impairment in mice.

Methods

Mice were randomly divided into 5 groups: the control group (sham operated), the Aβ_25-35 treated group, the positive drug group, and large and small dosage of the CDT groups, respectively. CDT was administered at a dose of 0.81 g/kg and 0.405 g/kg for 3 weeks. The mice in the positive drug group were treated with 0.4 mg/kg of Huperzine A, whereas the mice of the control and Aβ_25-35 treated groups were administrated orally with equivalent saline. After 7 days of preventive treatment, mice were subjected to lateral ventricle injection of Aβ_25-35 to establish the mice model of Alzheimer’s disease. Spatial memory impairment was evaluated by Morris water maze test. Choline acetyltransferase (ChAT) contents in hippocampus and cortex were quantified by ELISA. The levels of cytokines, receptor of activated protein kinase C1 (RACK1) and brain-derived neurotrophic factor (BDNF) in hippocampus were measured by RT-PCR and ELISA.

Results

The results showed that Aβ_25-35 caused spatial memory impairment as demonstrated by performance in the Morris water maze test. CDT was able to confer a significant improvement in spatial memory, and protect mice from Aβ_25-35-induced neurotoxicity. Additionally, CDT also inhibited the increase of TNF-α and IL-6 level, and increased the expression of choline acetyltransferase (ChAT), receptor of activated protein kinase C1 (RACK1) and brain-derived neurotrophic factor (BDNF) in brain as compared to model mice.

Conclusion

These findings strongly implicate that CDT may be a useful treatment against learning and memory deficits in mice by rescuing imbalance between cytokines and neurotrophins.

Intravenous immunoglobulin and Alzheimer's disease: what now?

Intravenous immunoglobulin (IVIG) products are prepared from purified plasma immunoglobulins from large numbers of healthy donors. Pilot studies with the IVIG preparations Octagam and Gammagard in individuals with mild-to-moderate Alzheimer’s disease (AD) suggested stabilization of cognitive functioning in these patients, and a phase II trial with Gammagard reported similar findings. However, subsequent reports from Octagam’s phase II trial and Gammagard’s phase III trial found no evidence for slowing of AD progression. Although these recent disappointing results have reduced enthusiasm for IVIG as a possible treatment for AD, it is premature to draw final conclusions; a phase III AD trial with the IVIG product Flebogamma is still in progress. IVIG was the first attempt to use multiple antibodies to treat AD. This approach should be preferable to administration of single monoclonal antibodies in view of the multiple processes that are thought to contribute to AD neuropathology. Development of “AD-specific” preparations with higher concentrations of selected human antibodies and perhaps modified in other ways (such as increasing their anti-inflammatory effects and/or ability to cross the blood–brain barrier) should be considered. Such preparations, if generated with recombinant technology, could overcome the problems of high cost and limited supplies, which have been major concerns relating to the possible widespread use of IVIG in AD patients. This review summarizes the recent AD IVIG trials and discusses the major issues relating to possible use of IVIG for treating AD, as well as the critical questions which remain.

Intravenous immunglobulin binds beta amyloid and modifies its aggregation, neurotoxicity and microglial phagocytosis in vitro

Intravenous Immunoglobulin (IVIG) has been proposed as a potential therapeutic for Alzheimer's disease (AD) and its efficacy is currently being tested in mild-to-moderate AD. Earlier studies reported the presence of anti-amyloid beta (Aβ) antibodies in IVIG. These observations led to clinical studies investigating the potential role of IVIG as a therapeutic agent in AD. Also, IVIG is known to mediate beneficial effects in chronic inflammatory and autoimmune conditions by interfering with various pathological processes. Therefore, we investigated the effects of IVIG and purified polyclonal Aβ -specific antibodies (pAbs-Aβ) on aggregation, toxicity and phagocytosis of Aβ in vitro, thus elucidating some of the potential mechanisms of action of IVIG in AD patients. We report that both IVIG and pAbs-Aβ specifically bound to Aβ and inhibited its aggregation in a dose-dependent manner as measured by Thioflavin T assay. Additionally, IVIG and the purified pAbs-Aβ inhibited Aβ-induced neurotoxicity in the SH-SY5Y human neuroblastoma cell line and prevented Aβ binding to rat primary cortical neurons. Interestingly, IVIG and pAbs-Aβ also increased the number of phagocytosing cells as well as the amount of phagocytosed fibrillar Aβ by BV-2 microglia. Phagocytosis of Aβ depended on receptor-mediated endocytosis and was accompanied by upregulation of CD11b expression. Importantly, we could also show that Privigen dose-dependently reversed Aβ-mediated LTP inhibition in mouse hippocampal slices. Therefore, our in vitro results suggest that IVIG may have an impact on different processes involved in AD pathogenesis, thereby promoting further understanding of the effects of IVIG observed in clinical studies.

Mechanisms of action of naturally occurring antibodies against β-amyloid on microglia

BACKGROUND

Naturally occurring autoantibodies against amyloid-β (nAbs-Aβ) have been shown to exert beneficial effects on transgenic Alzheimer's disease (AD) animals in vivo and on primary neurons in vitro. Not much is known about their effect on microglial cells. Our aim was to investigate the effect of nAbs-Aβ on amyloid-β (Aβ)-treated microglial cells in vitro with respect to cell viability, stress pathways, cytokine production and phagocytotic abilities and whether these effects can be conveyed to neurons.

METHODS

Primary microglial cells isolated from Swiss Webster mouse mesencephalons on embryonic day 13.5 were pretreated with nAbs-Aβ and then treated with Aβ oligomers. After 3 hours, phagocytosis as well as western blot analysis were evaluated to measure the amount of phagocytized Aβ. Cell viability was analyzed using an MTT assay 24 hours after treatment. Pro-inflammatory cytokines in the supernatants were analyzed with ELISAs and then we treated primary neuronal cells with these conditioned microglia supernatants. Twenty-four hours later we did a MTT assay of the treated neurons. We further investigated the effect of a single nAbs-Aβ administration on Tg2576 mice in vivo.

RESULTS

Upon co-administration of Aβ and nAbs-Aβ no change in microglia viability was observed. However, there was an increase in phosphorylated p38 protein level, an increase in the pro-inflammatory cytokines TNF-α and IL-6 and an increase in Aβ uptake by microglial cells. Treatment of primary neurons with conditioned microglia medium led to a 10% improvement in cell viability when nAbs-Aβ were co-administered compared to Aβ-treated cells alone. We were unable to detect changes in cytokine production in brain lysates of Tg2576 mice.

CONCLUSIONS

We provide evidence on the mechanism of action of nAbs-Aβ on microglia in vitro. Interestingly, our in vivo data indicate that nAbs-Aβ administration should be considered as a therapeutic strategy in AD, since there is no inflammatory reaction.

Anti-inflammatory and anti-amyloidogenic effects of a small molecule, 2,4-bis(p-hydroxyphenyl)-2-butenal in Tg2576 Alzheimer's disease mice model

BACKGROUND

Alzheimer's disease (AD) is pathologically characterized by excessive accumulation of amyloid-beta (Aβ) fibrils within the brain and activation of astrocytes and microglial cells. In this study, we examined anti-inflammatory and anti-amyloidogenic effects of 2,4-bis(p-hydroxyphenyl)-2-butenal (HPB242), an anti-inflammatory compound produced by the tyrosine-fructose Maillard reaction.

METHODS

12-month-old Tg2576 mice were treated with HPB242 (5 mg/kg) for 1 month and then cognitive function was assessed by the Morris water maze test and passive avoidance test. In addition, western blot analysis, Gel electromobility shift assay, immunostaining, immunofluorescence staining, ELISA and enzyme activity assays were used to examine the degree of Aβ deposition in the brains of Tg2576 mice. The Morris water maze task was analyzed using two-way ANOVA with repeated measures. Otherwise were analyzed by one-way ANOVA followed by Dunnett's post hoc test.

RESULTS

Treatment of HPB242 (5 mg/kg for 1 month) significantly attenuated cognitive impairments in Tg2576 transgenic mice. HPB242 also prevented amyloidogenesis in Tg2576 transgenic mice brains. This can be evidenced by Aβ accumulation, BACE1, APP and C99 expression and β-secretase activity. In addition, HPB242 suppresses the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) as well as activation of astrocytes and microglial cells. Furthermore, activation of nuclear factor-kappaB (NF-κB) and signal transducer and activator of transcription 1/3 (STAT1/3) in the brain was potently inhibited by HPB242.

CONCLUSIONS

Thus, these results suggest that HPB242 might be useful to intervene in development or progression of neurodegeneration in AD through its anti-inflammatory and anti-amyloidogenic effects.

Human anti-Aβ IgGs target conformational epitopes on synthetic dimer assemblies and the AD brain-derived peptide

Soluble non-fibrillar assemblies of amyloid-beta (Aβ) and aggregated tau protein are the proximate synaptotoxic species associated with Alzheimer's disease (AD). Anti-Aβ immunotherapy is a promising and advanced therapeutic strategy, but the precise Aβ species to target is not yet known. Previously, we and others have shown that natural human IgGs (NAbs) target diverse Aβ conformers and have therapeutic potential. We now demonstrate that these antibodies bound with nM avidity to conformational epitopes on plate-immobilized synthetic Aβ dimer assemblies, including synaptotoxic protofibrils, and targeted these conformers in solution. Importantly, NAbs also recognized Aβ extracted from the water-soluble phase of human AD brain, including species that migrated on denaturing PAGE as SDS-stable dimers. The critical reliance on Aβ's conformational state for NAb binding, and not a linear sequence epitope, was confirmed by the antibody's nM reactivity with plate-immobilized protofibrills, and weak uM binding to synthetic Aβ monomers and peptide fragments. The antibody's lack of reactivity against a linear sequence epitope was confirmed by our ability to isolate anti-Aβ NAbs from intravenous immunoglobulin using affinity matrices, immunoglobulin light chain fibrils and Cibacron blue, which had no sequence similarity with the peptide. These findings suggest that further investigations on the molecular basis and the therapeutic/diagnostic potential of anti-Aβ NAbs are warranted.

Impact of intravenous immunoglobulin on the dopaminergic system and immune response in the acute MPTP mouse model of Parkinson's disease

Intravenous immunoglobulin (IVIg) is a blood-derived product, used for the treatment of immunodeficiency and autoimmune diseases. Since a range of immunotherapies have recently been proposed as a therapeutic strategy for Parkinson’s disease (PD), we investigated the effects of an IVIg treatment in a neurotoxin-induced animal model of PD. Mice received four injections of MPTP (15 mg/kg) at 2-hour intervals followed by a 14-day IVIg treatment, which induced key immune-related changes such as increased regulatory T-cell population and decreased CD4⁺/CD8⁺ ratio. The MPTP treatment induced significant 80% and 84% decreases of striatal dopamine concentrations (P < 0.01), as well as 33% and 40% reductions in the number of nigral dopaminergic neurons (P < 0.001) in controls and IVIg-treated mice, respectively. Two-way analyses of variance further revealed lower striatal tyrosine hydroxylase protein levels, striatal homovanillic acid concentrations and nigral dopaminergic neurons (P < 0.05) in IVIg-treated animals. Collectively, our results fail to support a neurorestorative effect of IVIg on the nigrostriatal system in the MPTP-treated mice and even suggest a trend toward a detrimental effect of IVIg on the dopaminergic system. These preclinical data underscore the need to proceed with caution before initiating clinical trials of IVIg in PD patients.