Immunotherapy, vascular pathology, and microhemorrhages in transgenic mice

Immunotherapy in Alzheimer's disease: focusing on the efficacy of gantenerumab on amyloid-β clearance and cognitive decline

Gantenerumab, a human monoclonal antibody (mAb), has been thought of as a potential agent to treat Alzheimer's disease (AD) by specifically targeting regions of the amyloid-β (Aβ) peptide sequence. Aβ protein accumulation in the brain leads to amyloid plaques, causing neuroinflammation, oxidative stress, neuronal damage, and neurotransmitter dysfunction, thereby causing cognitive decline in AD. Gantenerumab involves disrupting Aβ aggregation and promoting the breakdown of larger Aβ aggregates into smaller fragments, which facilitates the action of Aβ-degrading enzymes in the brain, thus slowing down the progression of AD. Moreover, Gantenerumab acts as an opsonin, coating Aβ plaques and enhancing their recognition by immune cells, which, combined with its ability to improve the activity of microglia, makes it an intriguing candidate for promoting Aβ plaque clearance. Indeed, the multifaceted effects of Gantenerumab, including Aβ disaggregation, enhanced immune recognition, and improved microglia activity, may position it as a promising therapeutic approach for AD. Of note, reports suggest that Gantenerumab, albeit its capacity to reduce or eliminate Aβ, has not demonstrated effectiveness in reducing cognitive decline. This review, after providing an overview of immunotherapy approaches that target Aβ in AD, explores the efficacy of Gantenerumab in reducing Aβ levels and cognitive decline.

Receptor-mediated drug delivery of bispecific therapeutic antibodies through the blood-brain barrier

Therapeutic antibody drug development is a rapidly growing sector of the pharmaceutical industry. However, antibody drug development for the brain is a technical challenge, and therapeutic antibodies for the central nervous system account for ~3% of all such agents. The principal obstacle to antibody drug development for brain or spinal cord is the lack of transport of large molecule biologics across the blood-brain barrier (BBB). Therapeutic antibodies can be made transportable through the blood-brain barrier by the re-engineering of the therapeutic antibody as a BBB-penetrating bispecific antibody (BSA). One arm of the BSA is the therapeutic antibody and the other arm of the BSA is a transporting antibody. The transporting antibody targets an exofacial epitope on a BBB receptor, and this enables receptor-mediated transcytosis (RMT) of the BSA across the BBB. Following BBB transport, the therapeutic antibody then engages the target receptor in brain. RMT systems at the BBB that are potential conduits to the brain include the insulin receptor (IR), the transferrin receptor (TfR), the insulin-like growth factor receptor (IGFR) and the leptin receptor. Therapeutic antibodies have been re-engineered as BSAs that target the insulin receptor, TfR, or IGFR RMT systems at the BBB for the treatment of Alzheimer's disease and Parkinson's disease.

IgG Fusion Proteins for Brain Delivery of Biologics via Blood-Brain Barrier Receptor-Mediated Transport

The treatment of neurological disorders with large-molecule biotherapeutics requires that the therapeutic drug be transported across the blood–brain barrier (BBB). However, recombinant biotherapeutics, such as neurotrophins, enzymes, decoy receptors, and monoclonal antibodies (MAb), do not cross the BBB. These biotherapeutics can be re-engineered as brain-penetrating bifunctional IgG fusion proteins. These recombinant proteins comprise two domains, the transport domain and the therapeutic domain, respectively. The transport domain is an MAb that acts as a molecular Trojan horse by targeting a BBB-specific endogenous receptor that induces receptor-mediated transcytosis into the brain, such as the human insulin receptor (HIR) or the transferrin receptor (TfR). The therapeutic domain of the IgG fusion protein exerts its pharmacological effect in the brain once across the BBB. A generation of bifunctional IgG fusion proteins has been engineered using genetically engineered MAbs directed to either the BBB HIR or TfR as the transport domain. These IgG fusion proteins were validated in animal models of lysosomal storage disorders; acute brain conditions, such as stroke; or chronic neurodegeneration, such as Parkinson’s disease and Alzheimer’s disease. Human phase I–III clinical trials were also completed for Hurler MPSI and Hunter MPSII using brain-penetrating IgG-iduronidase and -iduronate-2-sulfatase fusion protein, respectively.

Improving mouse models for the study of Alzheimer's disease

Alzheimer's disease (AD) is a complex neurodegenerative disease whose risk is influenced by genetic and environmental factors. Although a number of pathological hallmarks have been extensively studied over the last several decades, a complete picture of disease initiation and progression remains unclear. We now understand that numerous cell types and systems are involved in AD pathogenesis, and that this cellular profile may present differently for each individual, making the creation of relevant mouse models challenging. However, with increasingly diverse data made available by genome-wide association studies, we can identify and examine new genes and pathways involved in genetic risk for AD, many of which involve vascular health and inflammation. When developing mouse models, it is critical to assess (1) an aging timeline that represents onset and progression in humans, (2) genetic variants and context, (3) environmental factors present in human populations that result in both neuropathological and functional changes-themes that we address in this chapter.

An Immunomodulatory Therapeutic Vaccine Targeting Oligomeric Amyloid-β

BACKGROUND

Aging is considered the most important risk factor for Alzheimer's disease (AD). Recent research supports the theory that immunotherapy targeting the "oligomeric" forms of amyloid-β (Aβ) may halt the progression of AD. However, previous clinical trial of the vaccine against Aβ, called AN1792, was suspended due to cases of meningoencephalitis in patients.

OBJECTIVE

To develop a peptide sensitized dendritic cells (DCs) vaccine that would target oligomer Aβ and prevent an autoimmune response.

METHODS

Double transgenic APPswe/PS1ΔE9 (Tg) and C57BL/6J control mice were used in this study. Cytokine expression profile detection, characterization of antisera, brain GSK-3β, LC3 expression, and spatial working memory testing before and post-vaccination were obtained.

RESULTS

Epitope prediction indicated that E22W42 could generate 13 new T cell epitopes which can strengthen immunity in aged subjects and silence several T cell epitopes of the wild type Aβ. The silenced T cell epitope could help avoid the autoimmune response that was seen in some patients of the AN-1792 vaccine. The E22W42 not only helped sensitize bone marrow-derived DCs for the development of an oligomeric Aβ-specific antibody, but also delayed memory impairment in the APP/PS1 mouse model. Most importantly, this E22W42 peptide will not alter the DC's natural immunomodulatory properties.

CONCLUSION

The E22W42 vaccine is possibly safer for patients with impaired immune systems. Since there is increasing evidence that oligomeric form of Aβ are the toxic species to neurons, the E22W42 antibody's specificity for these "oligomeric" Aβ species could provide the opportunity to produce some clinical benefits in AD subjects.

Innate immunity stimulation via CpG oligodeoxynucleotides ameliorates Alzheimer's disease pathology in aged squirrel monkeys

Alzheimer's disease is the most common cause of dementia and the only illness among the top 10 causes of death for which there is no disease-modifying therapy. The failure rate of clinical trials is very high, in part due to the premature translation of successful results in transgenic mouse models to patients. Extensive evidence suggests that dysregulation of innate immunity and microglia/macrophages plays a key role in Alzheimer's disease pathogenesis. Activated resident microglia and peripheral macrophages can display protective or detrimental phenotypes depending on the stimulus and environment. Toll-like receptors (TLRs) are a family of innate immune regulators known to play an important role in governing the phenotypic status of microglia. We have shown in multiple transgenic Alzheimer's disease mouse models that harnessing innate immunity via TLR9 agonist CpG oligodeoxynucleotides (ODNs) modulates age-related defects associated with immune cells and safely reduces amyloid plaques, oligomeric amyloid-β, tau pathology, and cerebral amyloid angiopathy (CAA) while promoting cognitive benefits. In the current study we have used a non-human primate model of sporadic Alzheimer's disease pathology that develops extensive CAA-elderly squirrel monkeys. The major complications in current immunotherapeutic trials for Alzheimer's disease are amyloid-related imaging abnormalities, which are linked to the presence and extent of CAA; hence, the prominence of CAA in elderly squirrel monkeys makes them a valuable model for studying the safety of the CpG ODN-based concept of immunomodulation. We demonstrate that long-term use of Class B CpG ODN 2006 induces a favourable degree of innate immunity stimulation without producing excessive or sustained inflammation, resulting in efficient amelioration of both CAA and tau Alzheimer's disease-related pathologies in association with behavioural improvements and in the absence of microhaemorrhages in aged elderly squirrel monkeys. CpG ODN 2006 has been well established in numerous human trials for a variety of diseases. The present evidence together with our earlier, extensive preclinical research, validates the beneficial therapeutic outcomes and safety of this innovative immunomodulatory approach, increasing the likelihood of CpG ODN therapeutic efficacy in future clinical trials.

Contrasting Metabolic Insufficiency in Aging and Dementia

Metabolic insufficiency and neuronal dysfunction occur in normal aging but is exaggerated in dementia and Alzheimer's disease (AD). Metabolic insufficiency includes factors important for both substrate supply and utilization in the brain. Metabolic insufficiency occurs through a number of serial mechanisms, particularly changes in cerebrovascular supply through blood vessel abnormalities (ie, small and large vessel vasculopathy, stroke), alterations in neurovascular coupling providing dynamic blood flow supply in relation to neuronal demand, abnormalities in blood brain barrier including decreased glucose and amino acid transport, altered glymphatic flow in terms of substrate supply across the extracellular space to cells and drainage into CSF of metabolites, impaired transport into cells, and abnormal intracellular metabolism with more reliance on glycolysis and less on mitochondrial function. Recent studies have confirmed abnormal neurovascular coupling in a mouse model of AD in response to metabolic challenges, but the supply chain from the vascular system into neurons is disrupted much earlier in dementia than in equivalently aged individuals, contributing to the progressive neuronal degeneration and cognitive dysfunction associated with dementia. We discuss several metabolic treatment approaches, but these depend on characterizing patients as to who would benefit the most. Surrogate biomarkers of metabolism are being developed to include dynamic estimates of neuronal demand, sufficiency of neurovascular coupling, and glymphatic flow to supplement traditional static measurements. These surrogate biomarkers could be used to gauge efficacy of metabolic treatments in slowing down or modifying dementia time course.

Molecular Pathobiology of the Cerebrovasculature in Aging and in Alzheimers Disease Cases With Cerebral Amyloid Angiopathy

Cerebrovascular dysfunction and cerebral amyloid angiopathy (CAA) are hallmark features of Alzheimer's disease (AD). Molecular damage to cerebrovessels in AD may result in alterations in vascular clearance mechanisms leading to amyloid deposition around blood vessels and diminished neurovascular-coupling. The sequelae of molecular events leading to these early pathogenic changes remains elusive. To address this, we conducted a comprehensive in-depth molecular characterization of the proteomic changes in enriched cerebrovessel fractions isolated from the inferior frontal gyrus of autopsy AD cases with low (85.5 ± 2.9 yrs) vs. high (81 ± 4.4 yrs) CAA score, aged-matched control (87.4 ± 1.5 yrs) and young healthy control (47 ± 3.3 yrs) cases. We employed a 10-plex tandem isobaric mass tag approach in combination with our ultra-high pressure liquid chromatography MS/MS (Q-Exactive) method. Enriched cerebrovascular fractions showed very high expression levels of proteins specific to endothelial cells, mural cells (pericytes and smooth muscle cells), and astrocytes. We observed 150 significantly regulated proteins in young vs. aged control cerebrovessels. The top pathways significantly modulated with aging included chemokine, reelin, HIF1α and synaptogenesis signaling pathways. There were 213 proteins significantly regulated in aged-matched control vs. high CAA cerebrovessels. The top three pathways significantly altered from this comparison were oxidative phosphorylation, Sirtuin signaling pathway and TCA cycle II. Comparison between low vs. high CAA cerebrovessels identified 84 significantly regulated proteins. Top three pathways significantly altered between low vs. high CAA cerebrovessels included TCA Cycle II, Oxidative phosphorylation and mitochondrial dysfunction. Notably, high CAA cases included more advanced AD pathology thus cerebrovascular effects may be driven by the severity of amyloid and Tangle pathology. These descriptive proteomic changes provide novel insights to explain the age-related and AD-related cerebrovascular changes contributing to AD pathogenesis. Particularly, disturbances in energy bioenergetics and mitochondrial biology rank among the top AD pathways altered in cerebrovessels. Targeting these failed mechanisms in endothelia and mural cells may provide novel disease modifying targets for developing therapeutic strategies against cerebrovascular deterioration and promoting cerebral perfusion in AD. Our future work will focus on interrogating and validating these novel targets and pathways and their functional significance.

Effect of Experimental Ischemic Stroke and PGE2 EP1 Selective Antagonism in Alzheimer's Disease Mouse Models

BACKGROUND

Neuroinflammation has been recognized as an important factor in the pathogenesis of Alzheimer's disease (AD). One of the most recognized pathways in mediating neuroinflammation is the prostaglandin E2-EP1 receptor pathway.

OBJECTIVE

Here, we examined the efficacy of the selective EP1 antagonist ONO-8713 in limiting amyloid-β (Aβ), lesion volumes, and behavioral indexes in AD mouse models after ischemic stroke.

METHODS

Transgenic APP/PS1, 3xTgAD, and wildtype (WT) mice were subjected to permanent distal middle cerebral artery occlusion (pdMCAO) and sham surgeries. Functional outcomes, memory, anatomical outcomes, and Aβ concentrations were assessed 14 days after surgery.

RESULTS

pdMCAO resulted in significant deterioration in functional and anatomical outcomes in the transgenic mice compared with the WT mice. No relevant differences were observed in the behavioral tests when comparing the ONO-8713 and vehicle-treated groups. Significantly lower cavitation (p = 0.0373) and percent tissue loss (p = 0.0247) were observed in APP/PS1 + ONO-8713 mice compared with the WT + ONO-8713 mice. However, the percent tissue injury was significantly higher in APP/PS1 + ONO-8713 mice compared with the WT + ONO-8713 group (p = 0.0373). Percent tissue loss was also significantly lower in the 3xTgAD + ONO-8713 mice than in the WT + ONO-8713 mice (p = 0.0185). ONO-8713 treatment also attenuated cortical microgliosis in APP/PS1 mice as compared with the vehicle (p = 0.0079); however, no differences were observed in astrogliosis across the groups. Finally, APP/PS1 mice presented with characteristic Aβ load in the cortex while 3xTgAD mice exhibited very low Aβ levels.

CONCLUSION

In conclusion, under the experimental conditions, EP1 receptor antagonist ONO-8713 showed modest benefits in anatomical outcomes after stroke, mainly in APP/PS1 mice.

The Neurovascular Unit Dysfunction in Alzheimer's Disease

Alzheimer’s disease (AD) is the most common neurodegenerative disease worldwide. Histopathologically, AD presents with two hallmarks: neurofibrillary tangles (NFTs), and aggregates of amyloid β peptide (Aβ) both in the brain parenchyma as neuritic plaques, and around blood vessels as cerebral amyloid angiopathy (CAA). According to the vascular hypothesis of AD, vascular risk factors can result in dysregulation of the neurovascular unit (NVU) and hypoxia. Hypoxia may reduce Aβ clearance from the brain and increase its production, leading to both parenchymal and vascular accumulation of Aβ. An increase in Aβ amplifies neuronal dysfunction, NFT formation, and accelerates neurodegeneration, resulting in dementia. In recent decades, therapeutic approaches have attempted to decrease the levels of abnormal Aβ or tau levels in the AD brain. However, several of these approaches have either been associated with an inappropriate immune response triggering inflammation, or have failed to improve cognition. Here, we review the pathogenesis and potential therapeutic targets associated with dysfunction of the NVU in AD.

Intramuscular injection of vectorized-scFvMC1 reduces pathological tau in two different tau transgenic models

With evidence supporting the prion-like spreading of extracellular tau as a mechanism for the initiation and progression of Alzheimer's disease (AD), immunotherapy has emerged as a potential disease-modifying strategy to target tau. Many studies have proven effective to clear pathological tau species in animal models of AD, and several clinical trials using conventional immunotherapy with anti-tau native antibodies are currently active. We have previously generated a vectorized scFv derived from the conformation-dependent anti-tau antibody MC1, scFvMC1, and demonstrated that its intracranial injection was able to prevent tau pathology in adult tau mice. Here, we show that, in a prevention paradigm and in two different tau transgenic models (JNPL3 and P301S), a one-time intramuscular injection of AAV1-scFvMC1 generated a long-lasting peripheral source of anti-tau scFvMC1 and significantly reduced insoluble and soluble tau species in the brain. Moreover, our data showed that scFvMC1 was internalized by the microglia, in the absence of overt inflammation. This study demonstrates the efficacy of intramuscular delivery of vectorized scFv to target tau, and suggests a new potential application to treat AD and the other tauopathies.

Brain Penetrating Bifunctional Erythropoietin-Transferrin Receptor Antibody Fusion Protein for Alzheimer's Disease

Erythropoietin (EPO), a glycoprotein cytokine essential to hematopoiesis, has neuroprotective effects in rodent models of Alzheimer's disease (AD). However, high therapeutic doses or invasive routes of administration of EPO are required to achieve effective brain concentrations due to low blood-brain barrier (BBB) penetrability, and high EPO doses result in hematopoietic side effects. These obstacles can be overcome by engineering a BBB-penetrable analog of EPO, which is rapidly cleared from the blood, by fusing EPO to a chimeric monoclonal antibody targeting the transferrin receptor (cTfRMAb), which acts as a molecular Trojan horse to ferry the EPO into the brain via the transvascular route. In the current study, we investigated the effects of the BBB-penetrable analog of EPO on AD pathology in a double transgenic mouse model of AD. Five and a half month old male APPswe/PSEN1dE9 (APP/PS1) transgenic mice were treated with saline ( n = 10) or the BBB-penetrable EPO ( n = 10) 3 days/week intraperitoneally for 8 weeks, compared to same-aged C57BL/6J wild-type mice treated with saline ( n = 8) with identical regiment. At 9 weeks following treatment initiation, exploration and spatial memory were assessed with the open-field and Y-maze test, mice were sacrificed, and brains were evaluated for Aβ peptide load, synaptic loss, BBB disruption, microglial activation, and microhemorrhages. APP/PS1 mice treated with the BBB-penetrable cTfRMAb-EPO fusion protein had significantly lower cortical and hippocampal Aβ peptide number ( p < 0.05) and immune-positive area ( p < 0.05), a decrease in hippocampal synaptic loss ( p < 0.05) and cortical microglial activation ( p < 0.001), and improved spatial memory ( p < 0.05) compared with APP/PS1 saline controls. BBB-penetrating EPO was not associated with microhemorrhage development. The cTfRMAb-EPO fusion protein offers therapeutic benefits by targeting multiple targets of AD pathogenesis and progression (Aβ load, synaptic loss, microglial activation) and improving spatial memory in the APP/PS1 mouse model of AD.

Anti-tau conformational scFv MC1 antibody efficiently reduces pathological tau species in adult JNPL3 mice

Tau, the main component of the neurofibrillary tangles (NFTs), is an attractive target for immunotherapy in Alzheimer's disease (AD) and other tauopathies. MC1/Alz50 are currently the only antibodies targeting a disease-specific conformational modification of tau. Passive immunization experiments using intra-peritoneal injections have previously shown that MC1 is effective at reducing tau pathology in the forebrain of tau transgenic JNPL3 mice. In order to reach a long-term and sustained brain delivery, and avoid multiple injection protocols, we tested the efficacy of the single-chain variable fragment of MC1 (scFv-MC1) to reduce tau pathology in the same animal model, with focus on brain regional differences. ScFv-MC1 was cloned into an AAV delivery system and was directly injected into the hippocampus of adult JNPL3 mice. Specific promoters were employed to selectively target neurons or astrocytes for scFv-MC1 expression. ScFv-MC1 was able to decrease soluble, oligomeric and insoluble tau species, in our model. The effect was evident in the cortex, hippocampus and hindbrain. The astrocytic machinery appeared more efficient than the neuronal, with significant reduction of pathology in areas distant from the site of injection. To our knowledge, this is the first evidence that an anti-tau conformational scFv antibody, delivered directly into the mouse adult brain, is able to reduce pathological tau, providing further insight into the nature of immunotherapy strategies.

Antibody Engineering for Optimized Immunotherapy in Alzheimer's Disease

There are nearly 50 million people with Alzheimer's disease (AD) worldwide and currently no disease modifying treatment is available. AD is characterized by deposits of Amyloid-β (Aβ), neurofibrillary tangles, and neuroinflammation, and several drug discovery programmes studies have focussed on Aβ as therapeutic target. Active immunization and passive immunization against Aβ leads to the clearance of deposits in humans and transgenic mice expressing human Aβ but have failed to improve memory loss. This review will discuss the possible explanations for the lack of efficacy of Aβ immunotherapy, including the role of a pro-inflammatory response and subsequent vascular side effects, the binding site of therapeutic antibodies and the timing of the treatment. We further discuss how antibodies can be engineered for improved efficacy.

Monitoring Blood-Brain Barrier Integrity Following Amyloid-β Immunotherapy Using Gadolinium-Enhanced MRI in a PDAPP Mouse Model

BACKGROUND

Amyloid-related imaging abnormalities (ARIA) have been reported with some anti-amyloid-β (Aβ) immunotherapy trials. They are detected with magnetic resonance imaging (MRI) and thought to represent transient accumulation of fluid/edema (ARIA-E) or microhemorrhages (ARIA-H). Although the clinical significance and pathophysiology are unknown, it has been proposed that anti-Aβimmunotherapy may affect blood-brain barrier (BBB) integrity.

OBJECTIVE

To examine vascular integrity in aged (12-16 months) PDAPP and wild type mice (WT), we performed a series of longitudinal in vivo MRI studies.

METHODS

Mice were treated on a weekly basis using anti-Aβimmunotherapy (3D6) and follow up was done longitudinally from 1-12 weeks after treatment. BBB-integrity was assessed using both visual assessment of T1-weighted scans and repeated T1 mapping in combination with gadolinium (Gd-DOTA).

RESULTS

A subset of 3D6 treated PDAPP mice displayed numerous BBB disruptions, whereas WT and saline-treated PDAPP mice showed intact BBB integrity under the conditions tested. In addition, the contrast induced decrease in T1 value was observed in the meningeal and midline area. BBB disruption events occurred early during treatment (between 1 and 5 weeks), were transient, and resolved quickly. Finally, BBB-leakages associated with microhemorrhages were confirmed by Perls'Prussian blue histopathological analysis.

CONCLUSION

Our preclinical findings support the hypothesis that 3D6 leads to transient leakage from amyloid-positive vessels. The current study has provided valuable insights on the time course of vascular alterations during immunization treatment and supports further research in relation to the nature of ARIA and the utility of in vivo repeated T1 MRI as a translational tool.

Lymphatic drainage system of the brain: A novel target for intervention of neurological diseases

The belief that the vertebrate brain functions normally without classical lymphatic drainage vessels has been held for many decades. On the contrary, new findings show that functional lymphatic drainage does exist in the brain. The brain lymphatic drainage system is composed of basement membrane-based perivascular pathway, a brain-wide glymphatic pathway, and cerebrospinal fluid (CSF) drainage routes including sinus-associated meningeal lymphatic vessels and olfactory/cervical lymphatic routes. The brain lymphatic systems function physiological as a route of drainage for interstitial fluid (ISF) from brain parenchyma to nearby lymph nodes. Brain lymphatic drainage helps maintain water and ion balance of the ISF, waste clearance, and reabsorption of macromolecular solutes. A second physiological function includes communication with the immune system modulating immune surveillance and responses of the brain. These physiological functions are influenced by aging, genetic phenotypes, sleep-wake cycle, and body posture. The impairment and dysfunction of the brain lymphatic system has crucial roles in age-related changes of brain function and the pathogenesis of neurovascular, neurodegenerative, and neuroinflammatory diseases, as well as brain injury and tumors. In this review, we summarize the key component elements (regions, cells, and water transporters) of the brain lymphatic system and their regulators as potential therapeutic targets in the treatment of neurologic diseases and their resulting complications. Finally, we highlight the clinical importance of ependymal route-based targeted gene therapy and intranasal drug administration in the brain by taking advantage of the unique role played by brain lymphatic pathways in the regulation of CSF flow and ISF/CSF exchange.

The association between vertebrobasilar insufficiency and the risk of dementia: a nationwide register-based retrospective cohort study in Taiwan

OBJECTIVES

Neurodegenerative disorders are reportedly characterised by decreased regional cerebral blood flow. However, the association between vertebrobasilar insufficiency (VBI) and dementia remains unclear. In this nationwide, population-based, retrospective cohort study, we explored the potential association between VBI and dementia.

DESIGN

Nationwide population-based cohort study.

SETTING

Patients with VBI were newly diagnosed between 2000 and 2005 from the Taiwan National Health Insurance Research Database.

PARTICIPANTS

We included 3642 subjects as the VBI group. The control cohort included 14 568 randomly selected age-matched and sex-matched VBI-free individuals.

OUTCOME MEASURES

All subjects were followed until the diagnosis of dementia, death or the end of 2010. Patients with VBI, dementia (viz, vascular and non-vascular, including Alzheimer's) subtypes and other confounding factors were identified according to the International Classification of Diseases Clinical Modification Codes. Cox proportional hazards regression analysis was employed to examine adjusted HRs after adjusting for confounding factors.

RESULTS

Patients with VBI had a 1.807-fold (95% CI 1.643 to 1.988, p<0.001) higher risk to develop all-cause dementia than individuals without VBI. The risk was significantly higher in the VBI group than in the non-VBI group regardless of age (<65 years: HR: 2.997, 95% CI 1.451 to 6.454, p<0.001; ≥65 years: HR: 1.752, 95% CI 1.584 to 1.937, p<0.001). The VBI group had a higher risk of all-cause dementia than the non-VBI group regardless of sex and follow-up time intervals (<1 year, 1-2 years and≥2 years).

CONCLUSION

Patients with VBI appear to have an increased risk of developing dementia. Further research is needed to investigate the underlying pathophysiology.

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.

SIGNIFICANCE STATEMENT

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.

Innate Immunity Stimulation via Toll-Like Receptor 9 Ameliorates Vascular Amyloid Pathology in Tg-SwDI Mice with Associated Cognitive Benefits

Alzheimer's disease (AD) is characterized by the presence of parenchymal amyloid-β (Aβ) plaques, cerebral amyloid angiopathy (CAA) and neurofibrillary tangles. Currently there are no effective treatments for AD. Immunotherapeutic approaches under development are hampered by complications related to ineffectual clearance of CAA. Genome-wide association studies have demonstrated the importance of microglia in AD pathogenesis. Microglia are the primary innate immune cells of the brain. Depending on their activation state and environment, microglia can be beneficial or detrimental. In our prior work, we showed that stimulation of innate immunity with Toll-like receptor 9 agonist, class B CpG (cytosine-phosphate-guanine) oligodeoxynucleotides (ODNs), can reduce amyloid and tau pathologies without causing toxicity in Tg2576 and 3xTg-AD mouse models. However, these transgenic mice have relatively little CAA. In the current study, we evaluated the therapeutic profile of CpG ODN in a triple transgenic mouse model, Tg-SwDI, with abundant vascular amyloid, in association with low levels of parenchymal amyloid deposits. Peripheral administration of CpG ODN, both before and after the development of CAA, negated short-term memory deficits, as assessed by object-recognition tests, and was effective at improving spatial and working memory evaluated using a radial arm maze. These findings were associated with significant reductions of CAA pathology lacking adverse effects. Together, our extensive evidence suggests that this innovative immunomodulation may be a safe approach to ameliorate all hallmarks of AD pathology, supporting the potential clinical applicability of CpG ODN.

SIGNIFICANCE STATEMENT

Recent genetic studies have underscored the emerging role of microglia in Alzheimer's disease (AD) pathogenesis. Microglia lose their amyloid-β-clearing capabilities with age and as AD progresses. Therefore, the ability to modulate microglia profiles offers a promising therapeutic avenue for reducing AD pathology. Current immunotherapeutic approaches have been limited by poor clearance of a core AD lesion, cerebral amyloid angiopathy (CAA). The present study used Tg-SwDI mice, which have extensive CAA. We found that stimulation of the innate immune system and microglia/macrophage activation via Toll-like receptor 9 using CpG (cytosine-phosphate-guanine) oligodeoxynucleotides (ODNs) leads to cognitive improvements and CAA reduction, without associated toxicity. Our data indicate that this novel concept of immunomodulation represents a safer method to reduce all aspects of AD pathology and provide essential information for potential clinical use of CpG ODN.

A vaccine with Aβ oligomer-specific mimotope attenuates cognitive deficits and brain pathologies in transgenic mice with Alzheimer's disease

Background

β-Amyloid peptide (Aβ) oligomers are initial factors used to induce Alzheimer’s disease (AD) development, and Aβ monomers have normal physiological function. The antibodies or vaccines against Aβ monomers have serious problems, such as side effects and low curative effects. Therefore, it is essential to specifically target Aβ oligomers rather than monomers for the treatment of AD.

Methods

The mimotopes of Aβ oligomers were obtained by panning the phage-displayed random peptide libraries using oligomer-specific antibodies as targets and expressed on the surface of EBY100 Saccharomyces cerevisiae to generate yeast cell base vaccines. One vaccine (AOE1) induced antibodies specifically against Aβ oligomers and was selected for further study. The APP/PS1 mice were subcutaneously immunized with AOE1 eight times. The levels and characteristics of antibodies induced by AOE1 were determined by enzyme-linked immunosorbent assay. The effect of AOE1 on the cognitive deficits of AD mice was tested by novel object recognition (NOR) and Y-maze. Dot blot analysis, Western blot analysis, and immunohistochemistry were applied to measure the effects of AOE1 on Aβ pathologies, neuroinflammation, and microhemorrhages in the brains of AD mice.

Results

Eight mimotope candidates of Aβ oligomers were selected and expressed on EBY100 S. cerevisiae. Only AOE1 vaccine containing mimotope L2 induced antibodies that specifically recognized Aβ42 oligomers rather than monomers. AOE1 immunization significantly increased the AD mice’s exploration times for the novel object in the NOR test and the choices for new arms in the Y-maze test, and it reduced levels of Aβ oligomers and glial activation in the AD mouse brains. No activation of Aβ-specific T cells and microhemorrhages was observed in their brains following AOE1 vaccination.

Conclusions

AOE1 is the first vaccine applying the oligomer-specific mimotope as an immunogen, which could induce antibodies with high specificity to Aβ oligomers. AOE1 immunization attenuated Aβ pathologies and cognitive deficits in AD mice, decreased the overactivation of glial cells, and did not induce microhemorrhage in the brains of AD mice. These findings suggest that AOE1 may be a safer and more effective vaccine for AD treatment.

Blood-Brain Barrier Penetrating Biologic TNF-α Inhibitor for Alzheimer's Disease

Tumor necrosis factor alpha (TNF-α) driven processes are involved at multiple stages of Alzheimer's disease (AD) pathophysiology and disease progression. Biologic TNF-α inhibitors (TNFIs) are the most potent class of TNFIs but cannot be developed for AD since these macromolecules do not cross the blood-brain barrier (BBB). A BBB-penetrating TNFI was engineered by the fusion of the extracellular domain of the type II human TNF receptor (TNFR) to a chimeric monoclonal antibody (mAb) against the mouse transferrin receptor (TfR), designated as the cTfRMAb-TNFR fusion protein. The cTfRMAb domain functions as a molecular Trojan horse, binding to the mouse TfR and ferrying the biologic TNFI across the BBB via receptor-mediated transcytosis. The aim of the study was to examine the effect of this BBB-penetrating biologic TNFI in a mouse model of AD. Six-month-old APPswe, PSEN 1dE9 (APP/PS1) transgenic mice were treated with saline (n = 13), the cTfRMAb-TNFR fusion protein (n = 12), or etanercept (non-BBB-penetrating biologic TNFI; n = 11) 3 days per week intraperitoneally. After 12 weeks of treatment, recognition memory was assessed using the novel object recognition task, mice were sacrificed, and brains were assessed for amyloid beta (Aβ) load, neuroinflammation, BBB damage, and cerebral microhemorrhages. The cTfRMAb-TNFR fusion protein caused a significant reduction in brain Aβ burden (both Aβ peptide and plaque), neuroinflammatory marker ICAM-1, and a BBB disruption marker, parenchymal IgG, and improved recognition memory in the APP/PS1 mice. Fusion protein treatment resulted in low antidrug-antibody formation with no signs of either immune reaction or cerebral microhemorrhage development with chronic 12-week treatment. Chronic treatment with the cTfRMAb-TNFR fusion protein, a BBB-penetrating biologic TNFI, offers therapeutic benefits by targeting Aβ pathology, neuroinflammation, and BBB-disruption, overall improving recognition memory in a transgenic mouse model of AD.

Regulatory Forum Opinion Piece*: Use and Utility of Animal Models of Disease for Nonclinical Safety Assessment: A Pharmaceutical Industry Survey

An Innovation and Quality (IQ) Consortium focus group conducted a cross-company survey to evaluate current practices and perceptions around the use of animal models of disease (AMDs) in nonclinical safety assessment of molecules in clinical development. The IQ Consortium group is an organization of pharmaceutical and biotechnology companies with the mission of advancing science and technology. The survey queried the utilization of AMDs during drug discovery in which drug candidates are evaluated in efficacy models and limited short-duration non-Good Laboratory Practices (GLP) toxicology testing and during drug development in which drug candidates are evaluated in GLP toxicology studies. The survey determined that the majority of companies used AMDs during drug discovery primarily as a means for proactively assessing potential nonclinical safety issues prior to the conduct of toxicology studies, followed closely by the use of AMDs to better understand toxicities associated with exaggerated pharmacology in traditional toxicology models or to derisk issues when the target is only expressed in the disease state. In contrast, the survey results indicated that the use of AMDs in development is infrequent, being used primarily to investigate nonclinical safety issues associated with targets expressed only in disease states and/or in response to requests from global regulatory authorities.

Aβ vaccination in combination with behavioral enrichment in aged beagles: effects on cognition, Aβ, and microhemorrhages

Beta-amyloid (Aβ) immunotherapy is a promising intervention to slow Alzheimer's disease. Aging dogs naturally accumulate Aβ and show cognitive decline. An active vaccine against fibrillar Aβ 1-42 (VAC) in aged beagles resulted in maintenance but not improvement of cognition along with reduced brain Aβ. Behavioral enrichment (ENR) led to cognitive benefits but no reduction in Aβ. We hypothesized cognitive outcomes could be improved by combining VAC with ENR in aged dogs. Aged dogs (11-12 years) were placed into 4 groups: (1) control/control (C/C); (2) control/VAC (C/V); (3) ENR/control (E/C); and (4) ENR/VAC (E/V) and treated for 20 months. VAC decreased brain Aβ, pyroglutamate Aβ, increased cerebrospinal fluid Aβ 42 and brain-derived neurotrophic factor RNA levels but also increased microhemorrhages. ENR reduced brain Aβ and prevented microhemorrhages. The combination treatment resulted in a significant maintenance of learning over time, reduced Aβ, and increased brain-derived neurotrophic factor mRNA despite increased microhemorrhages; however, there were no benefits to memory. These results suggest that the combination of immunotherapy with behavioral enrichment leads to cognitive maintenance associated with reduced neuropathology that may benefit people with Alzheimer's disease.

Asiatic acid influences parasitaemia reduction and ameliorates malaria anaemia in P. berghei infected Sprague-Dawley male rats

BACKGROUND

Current malaria treatment is either "anti-parasitic", "anti-infectivity" or both without addressing the pathophysiological derangement (anti-disease aspect) associated with the disease. Asiatic acid is a natural phytochemical with oxidant, antioxidant and anti-inflammatory properties whose effect on malarial and accompanying pathophysiology are yet to be investigated. Asiatic acid influence in P. berghei-infected Sprague Dawley rats on %parasitaemia and malarial anaemia were investigated.

METHODS

Plasmodium berghei-infected rats (90-120 g) were orally administered with Asiatic acid (5, 10, 20 mg/kg) and 30 mg/kg chloroquine as a positive control. Changes in %parasitaemia and haematological parameters in Asiatic acid administered rats were monitored in a 21 day study and compared to controls.

RESULTS

All animals developed stable parasitaemia (15-20 %) by day 7. Asiatic acid doses suppressed parasitaemia, normalised haematological measurements and influenced biophysical characteristics changes. Most positive changes were associated with intragastric administration of 10 mg/kg Asiatic acid dose. Peak %parasitaemia in Asiatic acid administration occurred at days 12 with a shorter time course compared to day 9 for chloroquine (30 mg/kg) treatment with a longer time course.

CONCLUSIONS

Oral Asiatic acid administration influenced %parasitaemia suppression, ameliorated malarial anaemia and increased biophysical properties on infected animals. Asiatic acid may be a replacement alternative for chloroquine treatment with concomitant amelioration of malaria pathophysiology. Due to different action time courses, Asiatic acid and chloroquine may be possible candidates in combination therapy.

A murine model of inflammation-induced cerebral microbleeds

BACKGROUND

Cerebral microhemorrhages (CMH) are tiny deposits of blood degradation products in the brain and are pathological substrates of cerebral microbleeds. The existing CMH animal models are β-amyloid-, hypoxic brain injury-, or hypertension-induced. Recent evidence shows that CMH develop independently of hypoxic brain injury, hypertension, or amyloid deposition and CMH are associated with normal aging, sepsis, and neurodegenerative conditions. One common factor among the above pathologies is inflammation, and recent clinical studies show a link between systemic inflammation and CMH. Hence, we hypothesize that inflammation induces CMH development and thus, lipopolysaccharide (LPS)-induced CMH may be an appropriate model to study cerebral microbleeds.

METHODS

Adult C57BL/6 mice were injected with LPS (3 or 1 mg/kg, i.p.) or saline at 0, 6, and 24 h. At 2 or 7 days after the first injection, brains were harvested. Hematoxylin and eosin (H&E) and Prussian blue (PB) were used to stain fresh (acute) hemorrhages and hemosiderin (sub-acute) hemorrhages, respectively. Brain tissue ICAM-1, IgG, Iba1, and GFAP immunohistochemistry were used to examine endothelium activation, blood-brain barrier (BBB) disruption, and neuroinflammation. MRI and fluorescence microscopy were used to further confirm CMH development in this model.

RESULTS

LPS-treated mice developed H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. No surface and negligible H&E-positive CMH were observed in saline-treated mice (n = 12). LPS (3 mg/kg; n = 10) produced significantly higher number, size, and area of H&E-positive CMH at 2 days. LPS (1 mg/kg; n = 9) produced robust development of PB-positive CMH at 7 days, with significantly higher number and area compared with saline (n = 9)-treated mice. CMH showed the highest distribution in the cerebellum followed by the sub-cortex and cortex. LPS-induced CMH were predominantly adjacent to cerebral capillaries, and CMH load was associated with indices of brain endothelium activation, BBB disruption, and neuroinflammation. Fluorescence microscopy confirmed the extravasation of red blood cells into the brain parenchyma, and MRI demonstrated the presence of cerebral microbleeds.

CONCLUSIONS

LPS produced rapid and robust development of H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. The ease of development of both H&E- and PB-positive CMH makes the LPS-induced mouse model suitable to study inflammation-induced CMH.

Intracerebral haemorrhage in Down syndrome: protected or predisposed?

Down syndrome (DS), which arises from trisomy of chromosome 21, is associated with deposition of large amounts of amyloid within the central nervous system. Amyloid accumulates in two compartments: as plaques within the brain parenchyma and in vessel walls of the cerebral microvasculature. The parenchymal plaque amyloid is thought to result in an early onset

Alzheimer’s disease (AD) dementia, a phenomenon so common amongst people with DS that it could be considered a defining feature of the condition. The amyloid precursor protein ( APP) gene lies on chromosome 21 and its presence in three copies in DS is thought to largely drive the early onset AD. In contrast, intracerebral haemorrhage (ICH), the main clinical consequence of vascular amyloidosis, is a more poorly defined feature of DS. We review recent epidemiological data on stroke (including haemorrhagic stroke) in order to make comparisons with a rare form of familial AD due to duplication (i.e. having three copies) of the APP region on chromosome 21, here called ‘dup-APP’, which is associated with more frequent and severe ICH. We conclude that although people with DS are at increased risk of ICH, this is less common than in dup-APP, suggesting the presence of mechanisms that act protectively. We review these mechanisms and consider comparative research into DS and dup-APP that may yield further pathophysiological insight.

Vascular cognitive impairment and dementia

Vascular contributions to cognitive impairment are receiving heightened attention as potentially modifiable factors for dementias of later life. These factors have now been linked not only to vascular cognitive disorders but also Alzheimer's disease. In this chapter we review 3 related topics that address vascular contributions to cognitive impairment: 1. vascular pathogenesis and mechanisms; 2. neuropsychological and neuroimaging phenotypic manifestations of cerebrovascular disease; and 3. prospects for prevention of cognitive impairment of later life based on cardiovascular and stroke risk modification. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

White matter changes in dementia: role of impaired drainage of interstitial fluid

White matter abnormalities on magnetic resonance imaging (MRI) are associated with dementia and include white matter hyperintensities (WMH; also termed leukoaraiosis) and visible perivascular spaces (PVS). We review the potential role of impaired drainage of interstitial fluid in the pathogenesis of WMH and PVS. Whereas the volume of extracellular space in the grey matter is tightly controlled, fluid accumulates and expands the extracellular spaces of the white matter in acute hydrocephalus, vasogenic edema and WMH. Although there are no conventional lymphatic vessels in the brain, there is very effective lymphatic drainage for fluid and solutes along restricted pathways in the basement membranes of cerebral capillaries and arteries in young individuals. Lymphatic drainage of the brain is impaired with age and in association with apolipoprotein E ε4, risk factors for Alzheimer's disease and cerebral amyloid angiopathy (CAA). Deposition of proteins in the lymphatic drainage pathways in the walls of cerebral arteries with age is recognized as protein elimination failure angiopathy (PEFA), as in CAA and cerebral autosomal dominant arteriopathy and leukoencephalopathy (CADASIL). Facilitating perivascular lymphatic drainage from the aging brain may play a significant role in the prevention of CAA, WMH and Alzheimer's disease and may enhance the efficacy of immunotherapy for Alzheimer's disease.

Failure of perivascular drainage of β-amyloid in cerebral amyloid angiopathy

In Alzheimer's disease, amyloid-β (Aβ) accumulates as insoluble plaques in the brain and deposits in blood vessel walls as cerebral amyloid angiopathy (CAA). The severity of CAA correlates with the degree of cognitive decline in dementia. The distribution of Aβ in the walls of capillaries and arteries in CAA suggests that Aβ is deposited in the perivascular pathways by which interstitial fluid drains from the brain. Soluble Aβ from the extracellular spaces of gray matter enters the basement membranes of capillaries and drains along the arterial basement membranes that surround smooth muscle cells toward the leptomeningeal arteries. The motive force for perivascular drainage is derived from arterial pulsations combined with the valve effect of proteins present in the arterial basement membranes. Physical and biochemical changes associated with arteriosclerosis, aging and possession of apolipoprotein E4 genotype lead to a failure of perivascular drainage of soluble proteins, including Aβ. Perivascular cells associated with arteries and the lymphocytes recruited in the perivenous spaces contribute to the clearance of Aβ. The failure of perivascular clearance of Aβ may be a major factor in the accumulation of Aβ in CAA and may have significant implications for the design of therapeutics for the treatment of Alzheimer's disease.

Targeting human central nervous system protein kinases: An isoform selective p38αMAPK inhibitor that attenuates disease progression in Alzheimer's disease mouse models

The first kinase inhibitor drug approval in 2001 initiated a remarkable decade of tyrosine kinase inhibitor drugs for oncology indications, but a void exists for serine/threonine protein kinase inhibitor drugs and central nervous system indications. Stress kinases are of special interest in neurological and neuropsychiatric disorders due to their involvement in synaptic dysfunction and complex disease susceptibility. Clinical and preclinical evidence implicates the stress related kinase p38αMAPK as a potential neurotherapeutic target, but isoform selective p38αMAPK inhibitor candidates are lacking and the mixed kinase inhibitor drugs that are promising in peripheral tissue disease indications have limitations for neurologic indications. Therefore, pursuit of the neurotherapeutic hypothesis requires kinase isoform selective inhibitors with appropriate neuropharmacology features. Synaptic dysfunction disorders offer a potential for enhanced pharmacological efficacy due to stress-induced activation of p38αMAPK in both neurons and glia, the interacting cellular components of the synaptic pathophysiological axis, to be modulated. We report a novel isoform selective p38αMAPK inhibitor, MW01-18-150SRM (=MW150), that is efficacious in suppression of hippocampal-dependent associative and spatial memory deficits in two distinct synaptic dysfunction mouse models. A synthetic scheme for biocompatible product and positive outcomes from pharmacological screens are presented. The high-resolution crystallographic structure of the p38αMAPK/MW150 complex documents active site binding, reveals a potential low energy conformation of the bound inhibitor, and suggests a structural explanation for MW150’s exquisite target selectivity. As far as we are aware, MW150 is without precedent as an isoform selective p38MAPK inhibitor or as a kinase inhibitor capable of modulating in vivo stress related behavior.

A comparative evaluation of a novel vaccine in APP/PS1 mouse models of Alzheimer's disease

Immunization against amyloid-beta-peptide (Aβ) has been widely investigated as a potential immunotherapeutic approach for Alzheimer's disease (AD). With the aim of developing an active immunogenic vaccine without need of coadjuvant modification for human trials and therefore avoiding such side effects, we designed the Aβ_1–42 vaccine (EB101), delivered in a liposomal matrix, that based on our previous studies significantly prevents and reverses the AD neuropathology, clearing Aβ plaques while markedly reducing neuronal degeneration, behavioral deficits, and minimizing neuroinflammation in APP/PS1 transgenic mice. Here, the efficacy of our immunogenic vaccine EB101 was compared with the original immunization vaccine cocktail Aβ₄₂ + CFA/IFA (Freund's adjuvant), in order to characterize the effect of sphingosine-1-phosphate (S1P) in the immunotherapeutic response. Quantitative analysis of amyloid burden showed a notable decrease in the neuroinflammation reaction against Aβ plaques when S1P was compared with other treatments, suggesting that S1P plays a key role as a neuroprotective agent. Moreover, EB101 immunized mice presented a protective immunogenic reaction resulting in the increase of Aβ-specific antibody response and decrease of reactive glia in the affected brain areas, leading to a Th2 immunological reaction.

Tailoring the antibody response to aggregated Aß using novel Alzheimer-vaccines

Recent evidence suggests Alzheimer-Disease (AD) to be driven by aggregated Aß. Capitalizing on the mechanism of molecular mimicry and applying several selection layers, we screened peptide libraries for moieties inducing antibodies selectively reacting with Aß-aggregates. The technology identified a pool of peptide candidates; two, AFFITOPES AD01 and AD02, were assessed as vaccination antigens and compared to Aβ1-6, the targeted epitope. When conjugated to Keyhole Limpet Hemocyanin (KLH) and adjuvanted with aluminum, all three peptides induced Aß-targeting antibodies (Abs). In contrast to Aß1-6, AD01- or AD02-induced Abs were characterized by selectivity for aggregated forms of Aß and absence of reactivity with related molecules such as Amyloid Precursor Protein (APP)/ secreted APP-alpha (sAPPa). Administration of AFFITOPE-vaccines to APP-transgenic mice was found to reduce their cerebral amyloid burden, the associated neuropathological alterations and to improve their cognitive functions. Thus, the AFFITOME-technology delivers vaccines capable of inducing a distinct Ab response. Their features may be beneficial to AD-patients, a hypothesis currently tested within a phase-II-study.

Neuroinflammation in Alzheimer's disease; A source of heterogeneity and target for personalized therapy

Neuroinflammation has long been known as an accompanying pathology of Alzheimer's disease. Microglia surrounding amyloid plaques in the brain of Auguste D were described in the original publication of Alois Alzheimer. It is only quite recently, however, that we have a more complete appreciation for the diverse roles of neuroinflammation in neurodegenerative disorders such as Alzheimer's. While gaps in our knowledge remain, and conflicting data are abound in the field, our understanding of the complexities and heterogeneous functions of the inflammatory response in Alzheimer's is vastly improved. This review article will discuss some of the roles of neuroinflammation in Alzheimer's disease, in particular, how understanding heterogeneity in the individual inflammatory response can be used in therapeutic development and as a mechanism of personalizing our treatment of the disease.

A coimmunization vaccine of Aβ42 ameliorates cognitive deficits without brain inflammation in an Alzheimer's disease model

INTRODUCTION

Vaccination against amyloid-β protein (Aβ42) induces high levels of antibody, making it a promising strategy for treating Alzheimer's disease (AD). One drawback in the past was that clinical trial approval was withheld because of speculation that the Aβ42 vaccine induces CD4(+) T cell infiltrations into the central nervous system. To reduce T-cell activation while concomitantly maintaining high anti-Aβ42 titers is a great challenge in immunology.

METHODS

We aimed to demonstrate that coimmunization with Aβ42 protein and expression plasmid can be beneficial in a mouse AD model and can prevent inflammation. We immunized the AD mice with the coimmunization vaccine and assessed behavior change and Aβ42 deposition. Furthermore, to determine the safety of the coimmunization vaccine, we used an induced Aβ42-EAE model to mimic the meningoencephalitis that happened in the AN-1792 vaccine clinical phase II trial and tested whether the coimmunization vaccine could ameliorate T-cell-mediated brain inflammation.

RESULTS

The coimmunization vaccination reduced Aβ plaques and significantly ameliorated cognitive deficit while inhibiting T-cell-mediated brain inflammation and infiltration. These studies demonstrate that the coimmunization strategy that we describe in this article can ameliorate AD pathology without notable adverse effects in mice.

CONCLUSIONS

A coimmunization strategy leading to the development of a safe immunotherapeutic/preventive protocol against AD in humans is warranted.

Immunotherapy in Alzheimer's disease: do we have all the pieces of the puzzle?

Results of Phase III studies involving a large number of Alzheimer's disease (AD) patients treated by passive immunotherapy with humanized anti-amyloid β monoclonal antibodies have recently been released. These approaches failed to show a significant clinical benefit in patients with mild to moderate AD. The most considered explanation is that the patients have been treated too late. Whereas targeting patients at asymptomatic stages of the disease is a critical step in the goal of improving the efficacy of such antibody-based strategies, several other important factors should be considered in the development and clinical evaluation of anti-amyloid β immunotherapies, including the as yet poorly understood relationship of AD with the immune system and the importance of cerebral amyloid angiopathy. Better understanding the role of immune responses in AD and their impact on immunotherapy appears essential in the design of alternative or combinatorial immunotherapy approaches in AD, which may imply effectors other than antibodies and even additional antigenic targets.

Disaggregation of amyloid plaque in brain of Alzheimer's disease transgenic mice with daily subcutaneous administration of a tetravalent bispecific antibody that targets the transferrin receptor and the Abeta amyloid peptide

Anti-amyloid antibodies (AAA) are under development as new therapeutics that disaggregate the amyloid plaque in brain in Alzheimer's disease (AD). However, the AAAs are large molecule drugs that do not cross the blood-brain barrier (BBB), in the absence of BBB disruption. In the present study, an AAA was re-engineered for receptor-mediated transport across the BBB via the endogenous BBB transferrin receptor (TfR). A single chain Fv (ScFv) antibody form of an AAA was fused to the carboxyl terminus of each heavy chain of a chimeric monoclonal antibody (mAb) against the mouse TfR, and this produced a tetravalent bispecific antibody designated the cTfRMAb-ScFv fusion protein. Unlike a conventional AAA, which has a plasma half-time of weeks, the cTfRMAb-ScFv fusion protein is cleared from plasma in mice with a mean residence time of about 3 h. Therefore, a novel protocol was developed for the treatment of one year old presenilin (PS)-1/amyloid precursor protein (APP) AD double transgenic PSAPP mice, which were administered daily subcutaneous (sc) injections of 5 mg/kg of the cTfRMAb-ScFv fusion protein for 12 consecutive weeks. At the end of the treatment, brain amyloid plaques were quantified with confocal microscopy using both Thioflavin-S staining and immunostaining with the 6E10 antibody against Abeta amyloid fibrils. Fusion protein treatment caused a 57% and 61% reduction in amyloid plaque in the cortex and hippocampus, respectively. No increase in plasma immunoreactive Abeta amyloid peptide, and no cerebral microhemorrhage, was observed. Chronic daily sc treatment of the mice with the fusion protein caused no immune reactions and only a low titer antidrug antibody response. In conclusion, re-engineering AAAs for receptor-mediated BBB transport allows for reduction in brain amyloid plaque without cerebral microhemorrhage following daily sc treatment for 12 weeks.

Intracranial injection of Gammagard, a human IVIg, modulates the inflammatory response of the brain and lowers Aβ in APP/PS1 mice along a different time course than anti-Aβ antibodies

Gammagard IVIg is a therapeutic approach to treat Alzheimer's disease currently in phase 3 clinical trials. Despite the reported efficacy of the approach the mechanism of action is poorly understood. We have previously shown that intracranial injection of anti-Aβ antibodies into the frontal cortex and hippocampus reveals important information regarding the time course of events once the agent is in the brain. In the current study we compared IVIg, mouse-pooled IgG, and the anti-Aβ antibody 6E10 injected intracranially into the frontal cortex and hippocampus of 7-month-old APP/PS1 mice. We established a time course of events ranging from 1 to 21 d postinjection. IVIg and pooled mouse IgG both significantly reduced Aβ deposition to the same degree as the 6E10 anti-Aβ antibody; however, the clearance was much slower to occur, happening between the 3 and 7 d time points. In contrast, as we have previously shown, Aβ reductions were apparent with the 6E10 anti-Aβ group at the 1 d time point. Also, neuroinflammatory profiles were significantly altered by the antibody treatments. APP/PS1 transgenic mice at 7 months of age typically exhibit an M2a inflammatory phenotype. All antibody treatments stimulated an M2b response, yet anti-Aβ antibody was a more rapid change. Because the neuroinflammatory switch occurs before the detectable reductions in amyloid deposition, we hypothesize that the IVIg and pooled mouse IgG act as immune modulators and this immune modulation is responsible for the reductions in amyloid pathology.

A shift in microglial β-amyloid binding in Alzheimer's disease is associated with cerebral amyloid angiopathy

Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA) are two common pathologies associated with β-amyloid (Aβ) accumulation and inflammation in the brain; neither is well understood. The objective of this study was to evaluate human post-mortem brains from AD subjects with purely parenchymal pathology, and those with concomitant CAA (and age-matched controls) for differential expression of microglia-associated Aβ ligands thought to mediate Aβ clearance and the association of these receptors with complement activation. Homogenates of brain parenchyma and enriched microvessel fractions from occipital cortex were probed for levels of C3b, membrane attack complex (MAC), CD11b and α-2-macroglobulin and immunoprecipitation was used to immunoprecipitate (IP) CD11b complexed with C3b and Aβ. Both C3b and MAC were significantly increased in CAA compared to AD-only and controls and IP showed significantly increased CD11b/C3b complexes with Aβ in AD/CAA subjects. Confocal microscopy was used to visualize these interactions. MAC was remarkably associated with CAA-affected blood vessels compared to AD-only and control vessels. These findings are consistent with an Aβ clearance mechanism via microglial CD11b that delivers Aβ and C3b to blood vessels in AD/CAA, which leads to Aβ deposition and propagation of complement to the cytolytic MAC, possibly leading to vascular fragility.

Four-dimensional microglia response to anti-Aβ treatment in APP/PS1xCX3CR1/GFP mice

Senile plaques, mainly composed of amyloid-β (Aβ), are a major hallmark of Alzheimer disease (AD), and immunotherapy is a leading therapeutic approach for Aβ clearance. Although the ultimate mechanisms for Aβ clearance are not well known, characteristic microglia clusters are observed in the surround of senile plaques, and are implicated both in the elimination of Aβ as well as the deleterious inflammatory effects observed in AD patients after active immunization. Therefore, analyzing the direct effect of immunotherapy on microglia, using longitudinal in vivo multiphoton microscopy can provide important information regarding the role of microglia in immunotherapy. While microglia were observed to surround senile plaques, topical anti-Aβ antibody administration, which led to a reduction in plaque size, directed microglia toward senile plaques, and the overall size of microglia and number of processes were increased. In some cases, we observed clusters of microglia in areas of the brain that did not have detectable amyloid aggregates, but this did not predict the deposition of new plaques in the area within a week of imaging, indicating that microglia react to but do not precipitate amyloid aggregation. The long-term presence of large microglial clusters in the surrounding area of senile plaques suggests that microglia cannot effectively remove Aβ unless anti-Aβ antibody is administered. All together, these data suggest that although there is a role for microglia in Aβ clearance, it requires an intervention like immunotherapy to be effective.

Traffic jam at the blood-brain barrier promotes greater accumulation of Alzheimer's disease amyloid-β proteins in the cerebral vasculature

Amyloid-β (Aβ) deposition in the brain vasculature results in cerebral amyloid angiopathy (CAA), which occurs in about 80% of Alzheimer's disease (AD) patients. While Aβ42 predominates parenchymal amyloid plaques in AD brain, Aβ40 is prevalent in the cerebrovascular amyloid. Dutch mutation of Aβ40 (E22Q) promotes aggressive cerebrovascular accumulation and leads to severe CAA in the mutation carriers; knowledge of how DutchAβ40 drives this process more efficiently than Aβ40 could reveal various pathophysiological events that promote CAA. In this study we have demonstrated that DutchAβ40 shows preferential accumulation in the blood-brain-barrier (BBB) endothelial cells due to its inefficient blood-to-brain transcytosis. Consequently, DutchAβ40 establishes a permeation barrier in the BBB endothelium, prevents its own clearance from the brain, and promotes the formation of amyloid deposits in the cerebral microvessels. The BBB endothelial accumulation of native Aβ40 is not robust enough to exercise such a significant impact on its brain clearance. Hence, the cerebrovascular accumulation of Aβ40 is slow and may require other copathologies to precipitate into CAA. In conclusion, the magnitude of Aβ accumulation in the BBB endothelial cells is a critical factor that promotes CAA; hence, clearing vascular endothelium of Aβ proteins may halt or even reverse CAA.

Perspectives in molecular imaging using staging biomarkers and immunotherapies in Alzheimer's disease

Sporadic Alzheimer's disease (AD) is an emerging chronic illness characterized by a progressive pleiotropic pathophysiological mode of actions triggered during the senescence process and affecting the elderly worldwide. The complex molecular mechanisms of AD not only are supported by cholinergic, beta-amyloid, and tau theories but also have a genetic basis that accounts for the difference in symptomatology processes activation among human population which will evolve into divergent neuropathological features underlying cognitive and behaviour alterations. Distinct immune system tolerance could also influence divergent responses among AD patients treated by immunotherapy. The complexity in nature increases when taken together the genetic/immune tolerance with the patient's brain reserve and with neuropathological evolution from early till advance AD clinical stages. The most promising diagnostic strategies in today's world would consist in performing high diagnostic accuracy of combined modality imaging technologies using beta-amyloid 42 peptide-cerebrospinal fluid (CSF) positron emission tomography (PET), Pittsburgh compound B-PET, fluorodeoxyglucose-PET, total and phosphorylated tau-CSF, and volumetric magnetic resonance imaging hippocampus biomarkers for criteria evaluation and validation. Early diagnosis is the challenge task that needs to look first at plausible mechanisms of actions behind therapies, and combining them would allow for the development of efficient AD treatment in a near future.

Intracerebral immune complex formation induces inflammation in the brain that depends on Fc receptor interaction

In this study, we investigate the underlying mechanisms of antibody-mediated inflammation in the brain. We show that immune complexes formed in the brain parenchyma generate a robust and long-lasting inflammatory response, characterized by increased expression of the microglia markers CD11b, CD68 and FcRII/III, but no neutrophil recruitment. In addition to these histological changes, we observed transient behavioural changes that coincided with the inflammatory response in the brain. The inflammatory and behavioural changes were absent in Fc-gamma chain (Fcγ)-deficient mice, while C1q-deficient mice were not different from wild-type mice. We conclude that, in the presence of antigen, antibodies can lead to a local immune complex-mediated inflammatory reaction in the brain parenchyma and indirectly induce neuronal tissue damage through recruitment and activation of microglia via Fcγ receptors. These observations may have important implications for the development of therapeutic antibodies directed against neuronal antigens used for therapeutic intervention in neurological diseases.

Proliferative and nonproliferative lesions of the rat and mouse central and peripheral nervous systems

Harmonization of diagnostic nomenclature used in the pathology analysis of tissues from rodent toxicity studies will enhance the comparability and consistency of data sets from different laboratories worldwide. The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of four major societies of toxicologic pathology to develop a globally recognized nomenclature for proliferative and nonproliferative lesions in rodents. This article recommends standardized terms for classifying changes observed in tissues of the mouse and rat central (CNS) and peripheral (PNS) nervous systems. Sources of material include academic, government, and industrial histopathology databases from around the world. Covered lesions include frequent, spontaneous, and aging-related changes as well as principal toxicant-induced findings. Common artifacts that might be confused with genuine lesions are also illustrated. The neural nomenclature presented in this document is also available electronically on the Internet at the goRENI website (http://www.goreni.org/).

Vaccination with a non-human random sequence amyloid oligomer mimic results in improved cognitive function and reduced plaque deposition and micro hemorrhage in Tg2576 mice

Background

It is well established that vaccination of humans and transgenic animals against fibrillar Aβ prevents amyloid accumulation in plaques and preserves cognitive function in transgenic mouse models. However, autoimmune side effects have halted the development of vaccines based on full length human Aβ. Further development of an effective vaccine depends on overcoming these side effects while maintaining an effective immune response.

Results

We have previously reported that the immune response to amyloid oligomers is largely directed against generic epitopes that are common to amyloid oligomers of many different proteins and independent of a specific amino acid sequence. Here we have examined whether we can exploit this generic immune response to develop a vaccine that targets amyloid oligomers using a non-human random sequence amyloid oligomer. In order to study the effect of vaccination against generic oligomer epitopes, a random sequence oligomer (3A) was selected as it forms oligomers that react with the oligomer specific A11 antibody. Oligomer mimics from 3A peptide, Aβ, islet amyloid polypeptide (IAPP), and Aβ fibrils were used to vaccinate Tg2576 mice, which develop a progressive accumulation of plaques and cognitive impairment. Vaccination with the 3A random sequence antigen was just as effective as vaccination with the other antigens in improving cognitive function and reducing total plaque load (Aβ burden) in the Tg2576 mouse brains, but was associated with a much lower incidence of micro hemorrhage than Aβ antigens.

Conclusion

These results shows that the amyloid Aβ sequence is not necessary to produce a protective immune response that specifically targets generic amyloid oligomers. Using a non-human, random sequence antigen may facilitate the development of a vaccine that avoids autoimmune side effects.

Alzheimer's-related peptide amyloid-β plays a conserved role in angiogenesis

Alzheimer's disease research has been at an impasse in recent years with lingering questions about the involvement of Amyloid-β (Aβ). Early versions of the amyloid hypothesis considered Aβ something of an undesirable byproduct of APP processing that wreaks havoc on the human neocortex, yet evolutionary conservation--over three hundred million years--indicates this peptide plays an important biological role in survival and reproductive fitness. Here we describe how Aβ regulates blood vessel branching in tissues as varied as human umbilical vein and zebrafish hindbrain. High physiological concentrations of Aβ monomer induced angiogenesis by a conserved mechanism that blocks γ-secretase processing of a Notch intermediate, NEXT, and reduces the expression of downstream Notch target genes. Our findings allude to an integration of signaling pathways that utilize γ-secretase activity, which may have significant implications for our understanding of Alzheimer's pathogenesis vis-à-vis vascular changes that set the stage for ensuing neurodegeneration.