anti-Aβ Immunotherapy Research Articles

Cerebral amyloid angiopathy and Alzheimer disease - one peptide, two pathways.

The shared role of amyloid-β (Aβ) deposition in cerebral amyloid angiopathy (CAA) and Alzheimer disease (AD) is arguably the clearest instance of crosstalk between neurodegenerative and cerebrovascular processes. The pathogenic pathways of CAA and AD intersect at the levels of Aβ generation, its circulation within the interstitial fluid and perivascular drainage pathways and its brain clearance, but diverge in their mechanisms of brain injury and disease presentation. Here, we review the evidence for and the pathogenic implications of interactions between CAA and AD. Both pathologies seem to be driven by impaired Aβ clearance, creating conditions for a self-reinforcing cycle of increased vascular Aβ, reduced perivascular clearance and further CAA and AD progression. Despite the close relationship between vascular and plaque Aβ deposition, several factors favour one or the other, such as the carboxy-terminal site of the peptide and specific co-deposited proteins. Amyloid-related imaging abnormalities that have been seen in trials of anti-Aβ immunotherapy are another probable intersection between CAA and AD, representing overload of perivascular clearance pathways and the effects of removing Aβ from CAA-positive vessels. The intersections between CAA and AD point to a crucial role for improving vascular function in the treatment of both diseases and indicate the next steps necessary for identifying therapies.

Early active immunization with Aβ3-10-KLH vaccine reduces tau phosphorylation in the hippocampus and protects cognition of mice.

Active and passive anti-Aβ immunotherapies have successfully been used for the prevention and treatment of Alzheimer's disease animal models. However, clinical use of these immunotherapies is not effective, because the vaccination is administered too late. At 1 month of age, 100 μL of Aβ3-10-KLH peptide (vaccine, 2 μg/μL) was subcutaneously injected into the neck of an amyloid precursor protein/presenilin-1/tau transgenic (3×Tg-AD) mouse model. Aβ3-10-KLH peptide was re-injected at 1.5, 2.5, 3.5, 4.5, 5.5, and 6.5 months of age. Serum levels of Aβ antibody were detected by enzyme-linked immunosorbent assay, while spatial learning and memory ability were evaluated by Morris water maze. Immunohistochemistry was used to detect total tau with HT7 and phosphorylated tau with AT8 (phosphorylation sites Ser202 and Thr205) and AT180 (phosphorylation site Thr231) antibodies in the hippocampus. In addition, western blot analysis was used to quantify AT8 and AT180 expression in the hippocampus. The results showed that after vaccine injection, mice produced high levels of Aβ antibody, cognitive function was significantly improved, and total tau and phosphorylated tau levels were significantly reduced. These findings suggest that early active immunization with Aβ3-10-KLH vaccine can greatly reduce tau phosphorylation, thereby mitigating the cognitive decline of 3×Tg-AD mice. This study was approved by the Animal Ethics Committee of China Medical University, China (approval No. 103-316) on April 2, 2016.

Differential effects of apoE and apoJ mimetic peptides on the action of an anti-Aβ scFv in 3xTg-AD mice

Anti-Aβ immunotherapy has emerged as a promising approach to treat Alzheimer’s disease (AD). The single-chain variable fragment scFv-h3D6 is an anti-Aβ antibody fragment that lacks the Fc region, which is associated with the induction of microglial reactivity by the full-length monoclonal antibody bapineuzumab. ScFv-h3D6 was previously shown to restore the levels of apolipoprotein E (apoE) and apolipoprotein J (apoJ) in a triple-transgenic-AD (3xTg-AD) mouse model. Since apoE and apoJ play an important role in the development of AD, we aimed to study the in vivo effect of the combined therapy of scFv-h3D6 with apoE and apoJ mimetic peptides (MPs). Four-and-a-half-month-old 3xTg-AD mice were treated for six weeks with scFv-h3D6, apoE-MP, apoJ-MP, or a combination of scFv-h3D6 with each of the MPs, or a vehicle, and then the results were compared to non-transgenic mice. Magnetic Resonance Imaging showed a general tendency of the different treatments to protect against the reduction in brain volume. Aβ burden decreased after treatment with scFv-h3D6, apoE-MP, or apoJ-MP, but the effect was not as evident with the combined therapies. In terms of glial reactivity, apoE-MP showed a potent anti-inflammatory effect that was eased by the presence of scFv-h3D6, whereas the combination of apoJ-MP and scFv-h3D6 was not detrimental. ScFv-h3D6 alone did not induce microglial reactivity, as full-length antibodies do; rather, it reduced it. Endogenous apoE and apoJ levels were decreased by scFv-h3D6, but the MPs lead to a simultaneous increase of both apolipoproteins. While apoE-MP and apoJ-MP demonstrated different effects in the combined therapies with scFv-h3D6, they did not improve the overall protective effect of scFv-h3D6 in reducing the Aβ burden, apolipoproteins levels or microglial reactivity.

Structural aspects of Alzheimer's disease immunotherapy targeted against amyloid-beta peptide.

Alzheimer's disease is the most prominent neurodegenerative disease and has no efficient therapies available so far. Immunotherapy against amyloid-β (Aβ) peptide is one of the currently tested therapeutic approaches. Here we have reviewed the available structural knowledge about antibodies tested as passive anti-Aβ immunotherapy in clinical trials. The therapeutic anti-Aβ antibodies differ in their epitope specificity and in recognition and affinity to different Aβ species present in vivo (Tab. 1, Fig. 1, Ref. 17).

Prophylactic active immunization with a novel epitope vaccine improves cognitive ability by decreasing amyloid plaques and neuroinflammation in APP/PS1 transgenic mice

Both amyloid-β peptide (Aβ) deposition and neuroinflammation are considered to be early events that play pivotal roles in Alzheimer’s disease (AD) pathogenesis and its associated cognitive impairment. Prophylactic anti-Aβ active immunotherapy is a promising therapeutic strategy for AD, if the Aβ-specific autoimmune responses to self T cell epitopes of Aβ can be avoided. This can be achieved by the use of antigen, which contains the B cell epitope of Aβ and excludes the Aβ-specific T cell epitope. In this study, we developed a novel peptide epitope vaccine, Aβ3-10-KLH, by coupling the B cell epitope Aβ3-10 to keyhole limpet hemocyanin (KLH) as the carrier protein, and subcutaneously injected it into 2.5-month-old APP/PS1 transgenic mice. Aβ3-10-KLH immunization induced high levels of anti-Aβ antibodies and significantly improved cognitive ability in APP/PS1 transgenic mice. Immunohistochemistry and immunofluorescence revealed that Aβ3-10-KLH immunization significantly reduced cerebral amyloid plaque formation and alleviated gliosis. The results indicate that Aβ3-10-KLH immunization successfully rescued cognitive impairment in APP/PS1 transgenic mice via decreasing cerebral Aβ deposition and neuroinflammation. Aβ3-10-KLH may potentially be safe and effective for prevention and treatment of AD.

Reduced Efficacy of Anti-Aβ Immunotherapy in a Mouse Model of Amyloid Deposition and Vascular Cognitive Impairment Comorbidity.

Vascular cognitive impairment and dementia (VCID) is the second most common form of dementia behind Alzheimer's disease (AD). It is estimated that 40% of AD patients also have some form of VCID. One promising therapeutic for AD is anti-Aβ immunotherapy, which uses antibodies against Aβ to clear it from the brain. While successful in clearing Aβ and improving cognition in mice, anti-Aβ immunotherapy failed to reach primary cognitive outcomes in several different clinical trials. We hypothesized that one potential reason the anti-Aβ immunotherapy clinical trials were unsuccessful was due to this high percentage of VCID comorbidity in the AD population. We used our unique model of VCID-amyloid comorbidity to test this hypothesis. We placed 9-month-old wild-type and APP/PS1 mice on either a control diet or a diet that induces hyperhomocysteinemia (HHcy). After being placed on the diet for 3 months, the mice then received intraperotineal injections of either IgG2a control or 3D6 for another 3 months. While we found that treatment of our comorbidity model with 3D6 resulted in decreased total Aβ levels, there was no cognitive benefit of the anti-Aβ immunotherapy in our AD/VCID mice. Further, microhemorrhages were increased by 3D6 in the APP/PS1/control but further increased in an additive fashion when 3D6 was administered to the APP/PS1/HHcy mice. This suggests that the use of anti-Aβ immunotherapy in patients with both AD and VCID would be ineffective on cognitive outcomes. Despite significant mouse model data demonstrating both pathological and cognitive efficacy of anti-Aβ immunotherapy for the treatment of Alzheimer's disease, clinical trial outcomes have been underwhelming, failing to meet any primary endpoints. We show here that vascular cognitive impairment and dementia (VCID) comorbidity eliminates cognitive efficacy of anti-Aβ immunotherapy, despite amyloid clearance. Further, cerebrovascular adverse events of the anti-Aβ immunotherapy are significantly exacerbated by the VCID comorbidity. These data suggest that VCID comorbidity with Alzheimer's disease may mute the response to anti-Aβ immunotherapy.

Reduced efficacy of anti-Aβ immunotherapy in a mouse model of amyloid deposition and vascular cognitive impairment co-morbidity

Reduced efficacy of anti-Aβ immunotherapy in a mouse model of amyloid deposition and vascular cognitive impairment co-morbidity

Anti-Aβ immunotherapy modulates the neuroinflammatory state of the brain, and the extent of modulation is variable depending on isotype and epitope

Anti-Aβ immunotherapy modulates the neuroinflammatory state of the brain, and the extent of modulation is variable depending on isotype and epitope

Prodromal Alzheimer's Disease Presenting as Cerebral Amyloid Angiopathy-Related Inflammation with Spontaneous Amyloid-Related Imaging Abnormalities and High Cerebrospinal Fluid Anti-Aβ Autoantibodies

Cerebral amyloid angiopathy-related inflammation (CAA-ri), a rare form of vasculitis associated with amyloid-β (Aβ) deposition in vessel walls, has been proposed as a spontaneous human model of the amyloid-related imaging abnormalities (ARIA) occurring after anti-Aβ immunotherapy for the treatment of Alzheimer's disease (AD). We describe a case of a patient with biopsy-proven CAA-ri and prodromal AD, confirmed by means of neuropsychological examination after 20 months follow-up, presenting with ARIA and high levels of cerebrospinal fluid anti-Aβ autoantibodies. This case further supports the analogies between the inflammatory response driven by anti-Aβ immunotherapy and that spontaneously occurring in CAA-ri.

Microglia constitute a barrier that prevents neurotoxic protofibrillar Aβ42 hotspots around plaques.

In Alzheimer’s disease (AD), β-amyloid (Aβ) plaques are tightly enveloped by microglia processes, but the significance of this phenomenon is unknown. Here we show that microglia constitute a barrier with profound impact on plaque composition and toxicity. Using high-resolution confocal and in vivo two-photon imaging in AD mouse models, we demonstrate that this barrier prevents outward plaque expansion and leads to compact plaque microregions with low Aβ42 affinity. Areas uncovered by microglia are less compact but have high Aβ42 affinity, leading to formation of protofibrillar Aβ42 hotspots that are associated with more severe axonal dystrophy. In aging, microglia coverage is reduced, leading to enlarged protofibrillar Aβ42 hotspots and more severe neuritic dystrophy. CX3CR1 gene deletion or anti-Aβ immunotherapy causes expansion of microglia coverage and reduced neuritic dystrophy. Failure of the microglia barrier and the accumulation of neurotoxic protofibrillar Aβ hotspots may constitute novel therapeutic and clinical imaging targets for AD.

Structural biology of Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease in humans with age being the biggest risk factor. The mechanisms by which the disease progresses to cognitive decline in the sufferer are complex and not fully elucidated. A defining pathological feature is the deposition of extracellular plaques composed primarily of misfolded amyloid beta (Aβ) peptide: a proteolytic breakdown product of the much larger Amyloid Precursor Protein. While Aβ peptides are the main constituents of amyloid plaques that burden the diseased brain, plaque burden correlates poorly with the severity of the disease. There is accumulating evidence that a prefibrillar or protofibrillar soluble form of Aβ can compromise neuronal functions and trigger cell death. Immunotherapy targeting Abeta is a promising direction in AD research with active and passive immunotherapies shown to lower cerebral Aβ levels and rescue cognitive function in animal models. Anti-Aβ immunotherapies are a significant class of AD therapeutics currently in human clinical trials. We have been examining the molecular basis of antibody engagement of Aβ epitopes to inform the analysis of clinical trial data and to guide the engineering of anti-Aβ antibodies with optimised specificity and affinity. We have determined the structures of three different AD antibodies in complex with Ab peptides: (1) WO2, which recognises the N-terminus of Aβ, (2) Mab 2286, which like the AD immunotherapeutic Ponezumab (Pfizer), shows specificity for the C-terminus of Aβ40 but has no significant cross-reactivity with Aβ42/43, and (3) Bapineuzumab, a humanized antibody developed by Pfizer and Johnson & Johnson which recognises the N-terminus of Aβ but cannot recognize N-terminally modified or truncated Aβ peptides (1). All these studies reveal surprising aspects of Aβ peptide recognition by the antibodies and suggest new avenues for AD antibody development.

Amyloid imaging in Alzheimer's disease: a literature review.

Therapies targeting amyloid-β peptide currently represent approximately 50% of drugs now being developed for Alzheimer's disease. Some, including active and passive anti-Aβ immunotherapy, directly target the amyloid plaques. The new amyloid tracers are increasingly being included in the proposed updated diagnostic criteria, and may allow earlier diagnosis. Those targeting amyloid-β peptide allow identification of amyloid plaques in vivo. We need to gain insight into all aspects of their application. As florbetapir (Amyvid™) and flutemetamol (Vizamyl™) have received marketing authorization, clinicians require deeper knowledge to be rationally used in diagnosis. In this paper, we review both completed and ongoing observational, longitudinal and interventional studies of these tracers, our main objective being to show the performance of the four most commonly used tracers and their validation.

The combined treatment of amyloid-β1-42-stimulated bone marrow–derived dendritic cells plus splenocytes from young mice prevents the development of Alzheimer's disease in APPswe/PSENldE9 mice

Anti-amyloid-β (Aβ) immunotherapy is a potential therapeutic strategy to reduce amyloid plaques and amyloid-associated pathologies in Alzheimer's disease (AD). Immune senescence with aging has also played a crucial role in AD pathogenesis and influences the effect of anti-Aβ immunotherapy. In this study, a combined treatment of Aβ1-42-bone marrow–derived dendritic cells (BMDCs) with intraperitoneal injection of splenocytes from young mice was designed as a novel immunotherapy for AD in APPswe/PSEN1de9 transgenic mice models. The results showed that the combined treatment not only elevated the level of anti-Aβ antibodies but also reduced amyloid plaques in brain and finally ameliorated deterioration of spatial learning and memory in AD mice. Additionally, the results revealed an increase of CD68 positive microglial cells in the vicinity of amyloid plaques in the mouse brain, which was responsible for the enhanced phagocytosis of Aβ plaques. In conclusion, the Aβ1-42-BMDCs plus splenocytes treatment improved the phagocytosis of microglia and prevented AD pathology more effectively. This combined immunotherapy provided a promising treatment in preventing the progression of AD in clinical studies in the near future.

Mild to moderate Alzheimer dementia with insufficient neuropathological changes

Recently, ~16% of participants in an anti-Aβ passive immunotherapy trial for mild-to-moderate Alzheimer disease (AD) had a negative baseline amyloid positron emission tomography (PET) scan. Whether they have AD or are AD clinical phenocopies remains unknown. We examined the 2005-2013 National Alzheimer's Coordinating Center autopsy database and found that ~14% of autopsied subjects clinically diagnosed with mild-to-moderate probable AD have no or sparse neuritic plaques, which would expectedly yield a negative amyloid PET scan. More than half of these "Aβ-negative" subjects have low neurofibrillary tangle Braak stages. These findings support the implementation of a positive amyloid biomarker as an inclusion criterion in future anti-Aβ drug trials.

Is there still any hope for amyloid-based immunotherapy for Alzheimer's disease?

We reviewed clinical trials on active and passive anti-β-amyloid (Aβ) immunotherapy for the treatment of Alzheimer's disease with a particular focus on monoclonal antibodies against Aβ. Studies on anti-Alzheimer's disease immunotherapy published in the period from January 2012 to October 2013 were reviewed. Both active and passive anti-Aβ immunotherapies were shown to clear brain Aβ deposits. However, an active anti-Aβ vaccine (AN1792) has been discontinued because it caused meningoencephalitis in 6% of Alzheimer's disease patients treated. Among passive immunotherapeutics, two Phase III clinical trials in mild-to-moderate Alzheimer's disease patients with bapineuzumab, a humanized monoclonal antibody directed at the N-terminal sequence of Aβ, were disappointing. Another antibody, solanezumab, directed at the mid-region of Aβ, failed in two Phase III clinical trials in mild-to-moderate Alzheimer's disease patients. A third Phase III study with solanezumab is ongoing in mildly affected Alzheimer's disease patients based on encouraging results in this subgroup of patients. Second-generation active Aβ vaccines (ACC-001, CAD106, and Affitope AD02) and new passive anti-Aβ immunotherapies (gantenerumab and crenezumab) are being tested in prodromal Alzheimer's disease patients, in presymptomatic individuals with Alzheimer's disease-related mutations, or in asymptomatic individuals at risk of developing Alzheimer's disease to definitely test the Aβ cascade hypothesis of Alzheimer's disease.

Open questions for Alzheimer’s disease immunotherapy

Perhaps more definitively than any other class of novel Alzheimer’s disease (AD) therapy, pre-clinical studies in mouse models of amyloid β (Aβ) deposition have established the disease-modifying potential of anti-Aβ immunotherapy. Despite disappointing results to date from anti-Aβ immunotherapy therapeutic trials, there is continued hope that such immunotherapies, especially if used in the preclinical stages, could prove to be the first disease-modifying therapies available for AD. The general optimism that Aβ-targeting and emerging tau-targeting immunotherapies may prove to be disease modifying is tempered by many unanswered questions regarding these therapeutic approaches, including but not limited to i) lack of precise understanding of mechanisms of action, ii) the factors that regulate antibody exposure in the brain, iii) the optimal target epitope, and iv) the mechanisms underlying side effects. In this review I discuss how answering these and other questions could increase the likelihood of therapeutic success. As passive immunotherapies are also likely to be extremely expensive, I also raise questions relating to cost-benefit of biologic-based therapies for AD that could limit future impact of these therapies by limiting access due to economic constraints.

Harnessing endogenous pathways and metabolites to treat or prevent neurodegenerative disease

As the field moves towards earlier interventions in preclinical stages of AD or even envisions true primary prevention strategies, the therapeutic strategies employed must be “safe enough”. Whether any current therapeutic (e.g., β-secretase inhibitors, γ-secretase modulators (GSM) or anti-Aβ immunotherapies) being tested for disease modification is sufficiently safe is not known. In order to try and identify “safe enough” therapeutics, we have been evaluating whether endogenous regulators of Aβ can be harnessed as therapeutics. We have identified a cholesterol metabolite, cholestenoic acid (CA), as potent GSM, and have genetic data from mice that are consistent with a role for CA in regulating Aβ42 levels in the brain. We will discuss our ongoing studies exploring how we might utilize CA or the CA metabolic pathway to safely lower Aβ42 levels. In addition, we have been evaluating how we can use soluble forms of endogenous innate immune receptors to alter Aβ deposition and modulate neuroinflammation in mouse models of AD. We have also been exploring the utility of such strategy in other neurodegenerative models. Effects of soluble toll-like receptors and soluble TREM2 will be presented. Our current data establish that soluble TLR4 and 5 both dramatically inhibit Aβ deposition but that soluble TLR2 and 6 do not. We also have data that suggest the utility of these soluble receptors in α-synucleinopathies. By using endogenous metabolites and receptors, we hope that the likelihood of adverse toxicities will be diminished and that these or endogenous factors can be safely developed for prophylactic or early intervention in AD and perhaps other neurodegenerative disorders.

Anti-amyloid beta to tau - based immunization: Developments in immunotherapy for Alzheimer disease.

Immunotherapy might provide an effective treatment for Alzheimer’s disease (AD). A unique feature of AD immunotherapies is that an immune response against a self-antigen needs to be elicited without causing adverse autoimmune reactions. Current research is focused on two possible targets in this regard. One is the inhibition of accumulation and deposition of amyloid beta 1–42 (Aβ42), which is one of the major peptides found in senile plaques, and the second target is hyperphosphorylated tau, which forms neurofibrillary tangles inside the nerve cell and shows association with the progression of dementia. Mouse models have shown that immunotherapy targeting Aβ42 as well as tau with the respective anti-Aβ or anti-tau antibodies can provide significant improvements in these mice. While anti-Aβ immunotherapy (active and passive immunizations) is already in several stages of clinical trials, tau-based immunizations have been analyzed only in mouse models. Recently, as a significant correlation of progression of dementia and levels of phosphorylated tau have been found, high interest has again focused on further development of tau-based therapies. While Aβ immunotherapy might delay the onset of AD, immunotherapy targeting tau might provide benefits in later stages of this disease. Last but not least, targeting Aβ and tau simultaneously with immunotherapy might provide additional therapeutic effects, as these two pathologies are likely synergistic; this is an approach that has not been tested yet. In this review, we will summarize animal models used to test possible therapies for AD, some of the facts about Aβ42 and tau biology, and present an overview on halted, ongoing, and upcoming clinical trials together with ongoing preclinical studies targeting tau or Aβ42.

Systemic vaccination with anti‐oligomeric monoclonal antibodies improves cognitive function by reducing Aβ deposition and tau pathology in 3xTg‐AD mice

Alzheimer's disease (AD) is a devastating disorder that is clinically characterized by a comprehensive cognitive decline. Accumulation of the amyloid-beta (Aβ) peptide plays a pivotal role in the pathogenesis of AD. In AD, the conversion of Aβ from a physiological soluble monomeric form into insoluble fibrillar conformation is an important event. The most toxic form of Aβ is oligomers, which is the intermediate step during the conversion of monomeric form to fibrillar form. There are at least two types of oligomers: oligomers that are immunologically related to fibrils and those that are not. In transgenic AD animal models, both active and passive anti-Aβ immunotherapies improve cognitive function and clear the parenchymal accumulation of amyloid plaques in the brain. In this report we studied effect of immunotherapy of two sequence-independent non-fibrillar oligomer specific monoclonal antibodies on the cognitive function, amyloid load and tau pathology in 3xTg-AD mice. Anti-oligomeric monoclonal antibodies significantly reduce the amyloid load and improve the cognition. The clearance of amyloid load was significantly correlated with reduced tau hyperphosphorylation and improvement in cognition. These results demonstrate that systemic immunotherapy using oligomer-specific monoclonal antibodies effectively attenuates behavioral and pathological impairments in 3xTg-AD mice. These findings demonstrate the potential of using oligomer specific monoclonal antibodies as a therapeutic approach to prevent and treat Alzheimer's disease.

Vascular alterations in PDAPP mice after anti-Aβ immunotherapy: Implications for amyloid-related imaging abnormalities

BackgroundClinical studies of β-amyloid (Aβ) immunotherapy in Alzheimer's disease (AD) patients have demonstrated reduction of central Aβ plaque by positron emission tomography (PET) imaging and the appearance of amyloid-related imaging abnormalities (ARIA). To better understand the relationship between ARIA and the pathophysiology of AD, we undertook a series of studies in PDAPP mice evaluating vascular alterations in the context of central Aβ pathology and after anti-Aβ immunotherapy. MethodsWe analyzed PDAPP mice treated with either 3 mg/kg/week of 3D6, the murine form of bapineuzumab, or isotype control antibodies for periods ranging from 1 to 36 weeks and evaluated the vascular alterations in the context of Aβ pathology and after anti-Aβ immunotherapy. The number of mice in each treatment group ranged from 26 to 39 and a total of 345 animals were analyzed. ResultsThe central vasculature displayed morphological abnormalities associated with vascular Aβ deposits. Treatment with 3D6 antibody induced clearance of vascular Aβ that was spatially and temporally associated with a transient increase in microhemorrhage and in capillary Aβ deposition. Microhemorrhage resolved over a time period that was associated with a recovery of vascular morphology and a decrease in capillary Aβ accumulation. ConclusionsThese data suggest that vascular leakage events, such as microhemorrhage, may be related to the removal of vascular Aβ. With continued treatment, this initial susceptibility period is followed by restoration of vascular morphology and reduced vulnerability to further vascular leakage events. The data collectively suggested a vascular amyloid clearance model of ARIA, which accounts for the currently known risk factors for the incidence of ARIA in clinical studies.