29946700
Immunization in Alzheimer's disease: naïve hope or realistic clinical potential?
There has been considerable recent interest in vaccination of patients by immunotherapy as a potentially clinically useful methodology for combating histopathological changes in Alzheimer's disease (AD). The focus of the majority of this research has been on (1) active immunotherapy using the pre-aggregated synthetic β-amyloid (Aβ) 42 preparation AN1792 vaccine (QS-21), or (2) passive immunization using injections of already prepared polyclonal anti-Aβ antibodies (intravenous immunoglobulin). These two clinical approaches to the treatment of patients with AD represent the focus of this review. We conclude here that, with certain caveats, immunization offers further potential as a technique for the treatment (and possible prevention) of AD. New studies are seeking to develop and apply safer vaccines that do not result in toxicity and neuroinflammation. Nevertheless, caution is warranted, and future clinical investigations are required to tackle key outstanding issues. These include the need to demonstrate efficacy in humans as well as animal models (especially with respect to the potentially toxic side effects of immunotherapy), and fine-tuning in safely guiding the immune response. The issue of defining necessary and sufficient criteria for determining clinical efficacy remains an additional important issue for future immunization trials. The vaccination methodology appears to offer substantial current promise for clearing both soluble and aggregated amyloid in AD. However, it remains to be determined whether this approach will help to repair already damaged neural systems in the disease, and the extent to which vaccination-driven amyloid clearance will impact beneficially on patients' neurocognitive capacity and their functional status. The outcomes of future studies will be important both clinically and scientifically: an important further test of the validity of the amyloid hypothesis of AD is to evaluate the impact of an effective anti-amyloid strategy on the functional status of patients with this disease.
20156799
Current pharmacotherapy for Alzheimer's disease.
Alzheimer's disease (AD) is an age-related neurodegenerative disease that affects approximately 4.5 million people in the United States. The mainstays of current pharmacotherapy for AD are compounds aimed at increasing the levels of acetylcholine in the brain, thereby facilitating cholinergic neurotransmission through inhibition of the cholinesterases. These drugs, known as acetylcholinesterase inhibitors (AChEIs), were first approved by the U.S. Food and Drug Administration (FDA) in 1995 based on clinical trials showing modest symptomatic benefit on cognitive, behavioral, and global measures. In 2004 the FDA approved memantine, an NMDA antagonist, for treating dementia symptoms in moderate to severe AD cases. In clinical practice, memantine may be co-administered with an AChEI, although neither drug individually or in combination affects the underlying pathophysiology of dementia. Dementia in AD results from progressive synaptic loss and neuronal death. As knowledge of the mechanisms responsible for neurodegeneration in AD increases, it is anticipated that neuroprotective drugs to slow or prevent neuronal dysfunction and death will be developed to complement current symptomatic treatments.
15150253
The Amyloid Hypothesis of Alzheimer's Disease: Progress and Problems on the Road to Therapeutics
It has been more than 10 years since it was first proposed that the neurodegeneration in Alzheimer's disease (AD) may be caused by deposition of amyloid β-peptide (Aβ) in plaques in brain tissue. According to the amyloid hypothesis, accumulation of Aβ in the brain is the primary influence driving AD pathogenesis. The rest of the disease process, including formation of neurofibrillary tangles containing tau protein, is proposed to result from an imbalance between Aβ production and Aβ clearance.
10478592
Biomarkers of neurodegeneration for diagnosis and monitoring therapeutics
Rapid progress towards understanding the molecular underpinnings of neurodegenerative disorders such as Alzheimer's disease is revolutionizing drug discovery for these conditions. Furthermore, the development of models for these disorders is accelerating efforts to translate insights related to neurodegenerative mechanisms into disease-modifying therapies. However, there is an urgent need for biomarkers to diagnose neurodegenerative disorders early in their course, when therapy is likely to be most effective, and to monitor responses of patients to new therapies. As research related to this need is currently most advanced for Alzheimer's disease, this Review focuses on progress in the development and validation of biomarkers to improve the diagnosis and treatment of Alzheimer's disease and related disorders.
36647451
Toward a Comprehensive Theory for Alzheimer's Disease. Hypothesis: Alzheimer's Disease Is Caused by the Cerebral Accumulation and Cytotoxicity of Amyloid β‐Protein
Abstract: A central challenge of research on Alzheimer's disease (AD) is to assemble the enormous body of scientific observations about the disorder, some of them seemingly in conflict with others, into a coherent and credible mechanism of pathogenesis. In this article, I attempt to synthesize the disparate findings on AD into a unified sequence that essentially begins with alterations in the production or clearance of the amyloid β‐protein (Aβ). Mounting evidence from many laboratories supports an Aβ accumulation in limbic and association cortices as the fundamental initiator of the disease, with attendant therapeutic implications.
10165633
Ineffective phagocytosis of amyloid-beta by macrophages of Alzheimer's disease patients.
The defective clearance of amyloid-beta (Abeta) in the brain of Alzheimer's disease (AD) patients is unexplained. The immunohistochemical studies of the frontal lobe and hippocampus show perivascular and intraplaque infiltration by blood-borne macrophages containing intracellular Abeta but only inefficient clearance of beta deposits. Neurons and neuronal nuclei, respectively, express interleukin-1beta and the chemokine RANTES, which could induce the inflammatory cell infiltration. To clarify the pathophysiology ofbeta clearance, we examined Abeta phagocytosis by monocytes and macrophages isolated from the blood of age-matched patients and controls. Control monocytes display excellent differentiation into macrophages and intracellular phagocytosis of Abeta followed by beta degradation or export. AD monocytes show poor differentiation and only surface uptake of Abeta and suffer apoptosis. HLA DR and cyclooxygenase-2 are abnormally expressed on neutrophils and monocytes of AD patients. AD patients have higher levels of intracellular cytokines compared to controls. Thus Abeta clearance is not restricted to brain microglia and involves systemic innate immune responses. In AD, however, macrophage phagocytosis is defective, which may elicit compensatory response by the adaptive immune system.
38571933
General risk factors for dementia: A systematic evidence review
This review identifies and quantifies general (ie, nongenetic) risk factors for all‐cause dementia, Alzheimer's disease, and vascular dementia specifically.
26080281
Apolipoprotein E, cholesterol metabolism, diabetes, and the convergence of risk factors for Alzheimer's disease and cardiovascular disease
High fat diets and sedentary lifestyles are becoming major concerns for Western countries. They have led to a growing incidence of obesity, dyslipidemia, high blood pressure, and a condition known as the insulin-resistance syndrome or metabolic syndrome. These health conditions are well known to develop along with, or be precursors to atherosclerosis, cardiovascular disease, and diabetes. Recent studies have found that most of these disorders can also be linked to an increased risk of Alzheimer's disease (AD). To complicate matters, possession of one or more apolipoprotein E ɛ4 (APOE ɛ4) alleles further increases the risk or severity of many of these conditions, including AD. ApoE has roles in cholesterol metabolism and Aβ clearance, both of which are thought to be significant in AD pathogenesis. The apparent inadequacies of ApoE ɛ4 in these roles may explain the increased risk of AD in subjects carrying one or more APOE ɛ4 alleles. This review describes some of the physiological and biochemical changes that the above conditions cause, and how they are related to the risk of AD. A diversity of topics is covered, including cholesterol metabolism, glucose regulation, diabetes, insulin, ApoE function, amyloid precursor protein metabolism, and in particular their relevance to AD. It can be seen that abnormal lipid, cholesterol and glucose metabolism are consistently indicated as central in the pathophysiology, and possibly the pathogenesis of AD. As diagnosis of mild cognitive impairment and early AD are becoming more reliable, and as evidence is accumulating that health conditions such as diabetes, obesity, and coronary artery disease are risk factors for AD, appropriate changes to diets and lifestyles will likely reduce AD risk, and also improve the prognosis for people already suffering from such conditions.
39846558
Risk and protective factors for sporadic Alzheimer's disease.
Alzheimer's disease (AD) is the most common form of senile dementia. There are 24.3 million people suffering from this progressive neurodegenerative disorder worldwide. A century ago, AD was characterized with regard to the clinical manifestations and pathology for the first time. Up till now, there is a lack of full understanding of the underlying causes and molecular mechanisms leading to this progressive form of dementia. The majority of AD cases occur sporadically, what suggested that they could arise through interactions among various genetic and environmental factors. Current epidemiological investigations show that midlife hypertension, cardiovascular diseases, hypercholesterolemia, diabetes, obesity, inflammation, and viral infections can significantly contribute to the development and progression of AD, whereas active engagement in social, mental and physical activities may delay the onset of the disease. Apolipoprotein E (ApoE) is considered as the main genetic risk factor in the sporadic AD that is closely connected to lipid metabolism. Other genes involved in the disease pathways related to AD pathology in addition to cholesterol metabolism, neuroinflammation, amyloid and tau cascade, neuronal signalling, and plasticity are under investigation. In spite of the significant progress achieved, it is still not clear how genetic vulnerability and environmental exposures may contribute to the susceptibility of the disease. Therefore, understanding the role of disease-related risk factors for AD pathogenesis may help to identify specific modifiable risk factors that could provide possibility for the prevention of Alzheimer's dementia.
4418088
Immunization with amyloid-β attenuates Alzheimer-disease-like pathology in the PDAPP mouse
Amyloid-β peptide (Aβ) seems to have a central role in the neuropathology of Alzheimer's disease (AD). Familial forms of the disease have been linked to mutations in the amyloid precursor protein (APP) and the presenilin genes,. Disease-linked mutations in these genes result in increased production of the 42-amino-acid form of the peptide (Aβ42), which is the predominant form found in the amyloid plaques of Alzheimer's disease,. The PDAPP transgenic mouse, which overexpresses mutant human APP (in which the amino acid at position 717 is phenylalanine instead of the normal valine), progressively develops many of the neuropathological hallmarks of Alzheimer's disease in an age- and brain-region-dependent manner,. In the present study, transgenic animals were immunized with Aβ42, either before the onset of AD-type neuropathologies (at 6 weeks of age) or at an older age (11 months), when amyloid-β deposition and several of the subsequent neuropathological changes were well established. We report that immunization of the young animals essentially prevented the development of β-amyloid-plaque formation, neuritic dystrophy and astrogliosis. Treatment of the older animals also markedly reduced the extent and progression of these AD-like neuropathologies. Our results raise the possibility that immunization with amyloid-β may be effective in preventing and treating Alzheimer's disease.
39249375
A beta peptide immunization reduces behavioural impairment and plaques in a model of Alzheimer's disease.
Much evidence indicates that abnormal processing and extracellular deposition of amyloid-beta peptide (A beta), a proteolytic derivative of the beta-amyloid precursor protein (betaAPP), is central to the pathogenesis of Alzheimer's disease (reviewed in ref. 1). In the PDAPP transgenic mouse model of Alzheimer's disease, immunization with A beta causes a marked reduction in burden of the brain amyloid. Evidence that A beta immunization also reduces cognitive dysfunction in murine models of Alzheimer's disease would support the hypothesis that abnormal A beta processing is essential to the pathogenesis of Alzheimer's disease, and would encourage the development of other strategies directed at the 'amyloid cascade'. Here we show that A beta immunization reduces both deposition of cerebral fibrillar A beta and cognitive dysfunction in the TgCRND8 murine model of Alzheimer's disease without, however, altering total levels of A beta in the brain. This implies that either a approximately 50% reduction in dense-cored A beta plaques is sufficient to affect cognition, or that vaccination may modulate the activity/abundance of a small subpopulation of especially toxic A beta species.
21422356
A beta peptide vaccination prevents memory loss in an animal model of Alzheimer's disease.
Vaccinations with amyloid-beta peptide (A beta) can dramatically reduce amyloid deposition in a transgenic mouse model of Alzheimer's disease. To determine if the vaccinations had deleterious or beneficial functional consequences, we tested eight months of A beta vaccination in a different transgenic model for Alzheimer's disease in which mice develop learning deficits as amyloid accumulates. Here we show that vaccination with A beta protects transgenic mice from the learning and age-related memory deficits that normally occur in this mouse model for Alzheimer's disease. During testing for potential deleterious effects of the vaccine, all mice performed superbly on the radial-arm water-maze test of working memory. Later, at an age when untreated transgenic mice show memory deficits, the A beta-vaccinated transgenic mice showed cognitive performance superior to that of the control transgenic mice and, ultimately, performed as well as nontransgenic mice. The A beta-vaccinated mice also had a partial reduction in amyloid burden at the end of the study. This therapeutic approach may thus prevent and, possibly, treat Alzheimer's dementia.
21579664
Peripheral anti-A beta antibody alters CNS and plasma A beta clearance and decreases brain A beta burden in a mouse model of Alzheimer's disease.
Active immunization with the amyloid beta (A beta) peptide has been shown to decrease brain A beta deposition in transgenic mouse models of Alzheimer's disease and certain peripherally administered anti-A beta antibodies were shown to mimic this effect. In exploring factors that alter A beta metabolism and clearance, we found that a monoclonal antibody (m266) directed against the central domain of A beta was able to bind and completely sequester plasma A beta. Peripheral administration of m266 to PDAPP transgenic mice, in which A beta is generated specifically within the central nervous system (CNS), results in a rapid 1,000-fold increase in plasma A beta, due, in part, to a change in A beta equilibrium between the CNS and plasma. Although peripheral administration of m266 to PDAPP mice markedly reduces A beta deposition, m266 did not bind to A beta deposits in the brain. Thus, m266 appears to reduce brain A beta burden by altering CNS and plasma A beta clearance.
5701343
Therapeutically effective antibodies against amyloid-beta peptide target amyloid-beta residues 4-10 and inhibit cytotoxicity and fibrillogenesis.
Immunization of transgenic mouse models of Alzheimer disease using amyloid-beta peptide (Abeta) reduces both the Alzheimer disease-like neuropathology and the spatial memory impairments of these mice. However, a therapeutic trial of immunization with Abeta42 in humans was discontinued because a few patients developed significant meningo-encephalitic cellular inflammatory reactions. Here we show that beneficial effects in mice arise from antibodies selectively directed against residues 4-10 of Abeta42, and that these antibodies inhibit both Abeta fibrillogenesis and cytotoxicity without eliciting an inflammatory response. These findings provide the basis for improved immunization antigens as well as attempts to design small-molecule mimics as alternative therapies.
12850827
Anti-Abeta antibody treatment promotes the rapid recovery of amyloid-associated neuritic dystrophy in PDAPP transgenic mice.
Neuritic plaques are a defining feature of Alzheimer disease (AD) pathology. These structures are composed of extracellular accumulations of amyloid-beta peptide (Abeta) and other plaque-associated proteins, surrounded by large, swollen axons and dendrites (dystrophic neurites) and activated glia. Dystrophic neurites are thought to disrupt neuronal function, but whether this damage is static, dynamic, or reversible is unknown. To address this, we monitored neuritic plaques in the brains of living PDAPP;Thy-1:YFP transgenic mice, a model that develops AD-like pathology and also stably expresses yellow fluorescent protein (YFP) in a subset of neurons in the brain. Using multiphoton microscopy, we observed and monitored amyloid through cranial windows in PDAPP;Thy-1:YFP double-transgenic mice using the in vivo amyloid-imaging fluorophore methoxy-X04, and individual YFP-labeled dystrophic neurites by their inherent fluorescence. In vivo studies using this system suggest that amyloid-associated dystrophic neurites are relatively stable structures in PDAPP;Thy-1:YFP transgenic mice over several days. However, a significant reduction in the number and size of dystrophic neurites was seen 3 days after Abeta deposits were cleared by anti-Abeta antibody treatment. This analysis suggests that ongoing axonal and dendritic damage is secondary to Abeta and is, in part, rapidly reversible.
23965747
Current Concepts and Future Prospects for Alzheimer Disease Vaccines
Alzheimer disease (AD) is the most prevalent form of dementia worldwide and is characterized by the progressive accumulation of the 42-residue amyloid β protein (Aβ) in brain regions serving memory and cognition. Only a few years ago, the proposition that AD may be amenable to any kind of therapy would have met with considerable skepticism. Yet, recent, exciting developments appear to suggest that immunizing against Aβ may bear some potential for arresting or even curing AD. However, a clinical trial of vaccination with synthetic human Aβ in AD patients was halted because of the development of meningoencephalitis in some patients. Further studies aimed at elucidating the mechanism of Aβ clearance upon Aβ immunization are needed. Such knowledge might facilitate the design of specific vaccination regimens, allowing exclusive targeting of Aβ plaques without inducing detrimental side effects.
43409846
The Memory Deficits in Alzheimer-Type Dementia: A Review
This review is an account of recent experimental studies of memory deficits at the early stages of Alzheimer-type dementia, evaluating these studies in relation to current theories of memory functioning in humans. Whilst memory deficits are found to be widespread, some aspects are more resilient to impairment than others. For example, the processes associated with articulatory rehearsal in working memory are unimpaired despite a reduction in performance on most tests of primary memory. The “implicit” aspects of secondary memory appear to remain unimpaired, in contrast to a marked decline in “explicit” or “episodic” memory. In addition, there is evidence that the rate of forgetting from secondary memory is normal. Some aspects of episodic and semantic memory are found to be impaired as a consequence of a decline in the efficient organisation and processing of verbal material at encoding or retrieval. It is concluded that the deficits share particular features found in organic amnesia, but with additional deficits which relate to impairments in other domains of functioning.
10535941
Effects of Aβ immunization (AN1792) on MRI measures of cerebral volume in Alzheimer disease
Background: Alzheimer disease (AD) is characterized by progressive cerebral atrophy that may be measured using MRI. Reported are MRI findings of a Phase IIa immunotherapy trial in AD prematurely terminated owing to meningoencephalitis in a subset of patients. Objective: To assess cerebral volume changes in patients immunized with AN1792 (β-amyloid [Aβ] 1 to 42) who were antibody responders (anti-AN1792 IgG titer of ≥1:2,200) compared with placebo patients. Methods: This randomized, multicenter, placebo-controlled, double-blind trial of AN1792 225 μg plus QS-21 50 μg included 372 patients with probable AD. Patients received one to three injections of AN1792/QS-21 or saline and were assessed for 12 months. Volumetric MRI was performed pre dose and at month 12 or early termination. Brain, ventricular, and hippocampal volume changes were measured from registered scan pairs. Results: Two hundred eighty-eight patients had paired scans (mean interval 10.9 months). Antibody responders (n = 45) had greater brain volume decrease (3.12 ± 1.98 vs 2.04 ± 1.74%; p = 0.007), greater ventricular enlargement as a percentage of baseline brain volume (1.10 ± 0.75 vs 0.48 ± 0.40%; p < 0.001), and a nonsignificant greater hippocampal volume decrease (3.78 ± 2.63 vs 2.86 ± 3.19%; p = 0.124) than placebo patients (n = 57). Increased losses in brain volume were not reflected in worsening cognitive performance; a composite z score across a Neuropsychological Test Battery showed differences favoring antibody responders over placebo (0.03 ± 0.39 vs −0.24 ± 0.45; p = 0.008). Conclusions: A dissociation between brain volume loss and cognitive function was observed in AN1792/QS-21 antibody responders. The reasons for this remain unclear but include the possibility that volume changes were due to amyloid removal and associated cerebral fluid shifts.
19875625
Neuropathology of human Alzheimer disease after immunization with amyloid-β peptide: a case report
Amyloid-β peptide (Aβ) has a key role in the pathogenesis of Alzheimer disease (AD). Immunization with Aβ in a transgenic mouse model of AD reduces both age-related accumulation of Aβ in the brain and associated cognitive impairment. Here we present the first analysis of human neuropathology after immunization with Aβ (AN-1792). Comparison with unimmunized cases of AD (n = 7) revealed the following unusual features in the immunized case, despite diagnostic neuropathological features of AD: (i) there were extensive areas of neocortex with very few Aβ plaques; (ii) those areas of cortex that were devoid of Aβ plaques contained densities of tangles, neuropil threads and cerebral amyloid angiopathy (CAA) similar to unimmunized AD, but lacked plaque-associated dystrophic neurites and astrocyte clusters; (iii) in some regions devoid of plaques, Aβ-immunoreactivity was associated with microglia; (iv) T-lymphocyte meningoencephalitis was present; and (v) cerebral white matter showed infiltration by macrophages. Findings (i)–(iii) strongly resemble the changes seen after Aβ immunotherapy in mouse models of AD and suggest that the immune response generated against the peptide elicited clearance of Aβ plaques in this patient. The T-lymphocyte meningoencephalitis is likely to correspond to the side effect seen in some other patients who received AN-1792 (refs. 7–9).
25336770
Neuropathology and Pathogenesis of Encephalitis following Amyloid β Immunization in Alzheimer's Disease
Immunizing transgenic PDAPP mice, which overexpress mutant APP and develop β‐amyloid deposition resembling plaques in Alzheimer's disease (AD), results in a decrease of amyloid burden when compared with non treated transgenic animals im‐munization with amyloid β peptide has been initiated in a randomised pilot study in AD. Yet a minority of patients developed a neurological complication consistent with meningoencephalitis and one patient died; the trial has been stopped. Neuropathological examination in that patient showed meningoencephalitis and focal atypically low numbers of diffuse and neuritic plaques but not of vascular amyloid nor regression of tau pathology in neurofibrillary tangles and neuropil threads. The present neuropathological study reports the second case of menigoencephalitis following immunization with amyloid‐β peptide in AD, and has been directed toward exploring mechanisms underlying decreased tau pathology in relation‐ with amyliod deposit regression, and possible molecular bases involved in the inflammatory response following immunization. Inflammatory infiltrates were composed of CD8+, CD3+, CD5+ and, rarely, CD7+ lymphocytes, whereas B lymphocytes and T cytotoxic cells CD16, CD57, TIA and graenzyme were negative. Characteristic neuropathological findings were focal depletion of diffuse and neuritic plaques, but not of amyloid angiopathy, and the presence of small numbers of extremely dense(collapsed) plaques surrounded by active microglia, and multinucleated giant cells filled with dense Aβ42and Aβ40, in addition to severe small cerebral blood Reduced amyloid burden was accompanied by low amyloid‐associated oxidative stress responses (reduced superoxide dismutase‐1:SOD‐1 expression) and by local inhibition of the stress‐activated protein kinase/c‐Jun N‐terminal kinase (SAPK/JNK) and p38 kinase which are involved in tau phosphorylation. These results support the amyloid cascade of tau phosphorylation in AD regarding phosphorylation of tau in neurofibrillary tangles and β‐amyloid deposition in neuritic plaques, but not of tau in neurofibrillary tangles and threads. Furthermore, amyloid reduction was accompanied by increased expression of the PA28α/β inductor, and of LMP7, LMP2 and MECL1 subunits of the immunopro‐teasome in microglial and inflammatory cells surrounding collapsed plaques, and in multinucleated giant cells.Immunoproteasome subunit expression was accompanied by local presentation of MHC class molecules. Release of antigenic peptides derived from β‐amyloid processing may enhance T‐cell inflammatory responses accounting for the meningoencephalitis following amyloid‐β peptide immunization
22930840
Lessons from the AN 1792 Alzheimer vaccine: lest we forget
Recent clinical and neuropathological data show that the AN 1792 vaccine enhanced the production of Abeta antibodies in the sera of Alzheimer's disease (AD) patients, but it appears to have been ineffective at stimulating the removal of Abeta deposits from the brain or at slowing the rate of cognitive decline. The 19 cases of meningoencephalitis were not linked in an obvious way to serum antibody titre, but they may have been linked to infiltration of the brain by antibodies and/or T-cells. Brain imaging indicated that oedema associated with the neuroinflammation did not reflect the typical distribution of neuritic plaques in AD. These outcomes were not anticipated by experiments on transgenic mice because compared to humans, these mice have less genetic variability, and their plaques have a different chemical composition, making them far more soluble and easier to remove. Furthermore, the consequences of vaccination are different. Vaccination of transgenic mice removes superfluous human Abeta while leaving endogenous mouse Abeta intact, whereas in humans the immune response is directed against an endogenous target that occurs naturally and is present in healthy brain tissue. The most important lesson to be learned from the AN 1792 trials is that new strategies for treating AD should not be tested on humans until they have been extensively tested on non-murine species.
6905030
Generation of antibodies specific for β-amyloid by vaccination of patients with Alzheimer disease
To characterize antibodies produced in humans in response to Aβ42 vaccination, we carried out immunohistochemical examinations of the brains of both transgenic mice and human patients with β-amyloid pathology. We collected sera from patients with Alzheimer disease who received a primary injection of pre-aggregated Aβ42 followed by one booster injection in a placebo-controlled study. Antibodies in immune sera recognized β-amyloid plaques, diffuse Aβ deposits and vascular β-amyloid in brain blood vessels. The antibodies did not cross-react with native full-length β-amyloid precursor protein or its physiological derivatives, including soluble Aβ42. These findings indicate that vaccination of AD patients with Aβ42 induces antibodies that have a high degree of selectivity for the pathogenic target structures. Whether vaccination to produce antibodies against β-amyloid will halt the cognitive decline in AD will depend upon clinical assessments over time.
19339379
Antibodies against beta-amyloid slow cognitive decline in Alzheimer's disease.
To test whether antibodies against beta-amyloid are effective in slowing progression of Alzheimer's disease, we assessed cognitive functions in 30 patients who received a prime and a booster immunization of aggregated Abeta(42) over a 1 year period in a placebo-controlled, randomized trial. Twenty patients generated antibodies against beta-amyloid, as determined by tissue amyloid plaque immunoreactivity assay. Patients who generated such antibodies showed significantly slower rates of decline of cognitive functions and activities of daily living, as indicated by the Mini Mental State Examination, the Disability Assessment for Dementia, and the Visual Paired Associates Test of delayed recall from the Wechsler Memory Scale, as compared to patients without such antibodies. These beneficial clinical effects were also present in two of three patients who had experienced transient episodes of immunization-related aseptic meningoencephalitis. Our results establish that antibodies against beta-amyloid plaques can slow cognitive decline in patients with Alzheimer's disease.
35177297
Combination Therapy of Donepezil and Vitamin E in Alzheimer Disease
&NA; A retrospective chart review was performed on 130 patients from the Ohio State University Memory Disorders Clinic to examine the long‐term effects of combination therapy with donepezil and vitamin E on patients with Alzheimer disease. Subjects were included if they met National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer's Disease and Related Disorders Association criteria for probable Alzheimer disease, had taken at least 5 mg donepezil and at least 1000 U vitamin E daily, had at least a 1‐year follow‐up while continuing these medications, and had a Mini‐Mental State Examination score of 10–24. The Mini‐Mental State Examination was then recorded annually thereafter. These data were compared with the Consortium to Establish a Registry for Alzheimer's Disease database for patients collected prior to the availability of these treatment options. Patients declined at a significantly lower rate as compared with the Consortium to Establish a Registry for Alzheimer's Disease data. The long‐term combination therapy of donepezil and vitamin E appears beneficial for patients with Alzheimer disease. Future prospective studies would be needed to compare combination treatment to vitamin E and donepezil alone.
26120821
A 1-year, randomized, placebo-controlled study of donepezil in patients with mild to moderate AD
Objective: To evaluate the long-term clinical efficacy and safety of donepezil versus placebo over 1 year in patients with mild to moderate AD. Methods: Patients (n = 286; mean age, 72.5 years) with possible or probable AD from five Northern European countries were randomized to receive either donepezil (n = 142; 5 mg/day for 28 days, followed by 10 mg/day) or placebo (n = 144) for 1 year. Results: The study was completed by 66.9% of the donepezil- and 67.4% of the placebo-treated patients. The benefit of donepezil over placebo was demonstrated by the Gottfries-Bråne-Steen (a global assessment for rating dementia symptoms) total score at weeks 24, 36, and 52 (p < 0.05) and at the study end point (week 52, last observation carried forward; p = 0.054). Advantages of donepezil over placebo were also observed in cognition and activities of daily living (ADL) assessed by the Mini-Mental State Examination at weeks 24, 36, and 52, and the end point (p < 0.02) and by the Progressive Deterioration Scale at week 52 and the end point (p < 0.05). Adverse events (AE) were recorded for 81.7% of donepezil- and 75.7% of placebo-treated patients, with 7% of donepezil- and 6.3% of placebo-treated patients discontinuing because of AE. Treatment response to donepezil was not predicted by APOE genotype or sex in this population. Conclusion: As the first 1-year, multinational, double-blinded, placebo-controlled study of a cholinesterase inhibitor in AD, these data support donepezil as a well tolerated and effective long-term treatment for patients with AD, with benefits over placebo on global assessment, cognition, and ADL.
18340153
Long-term effects of Aβ42 immunisation in Alzheimer's disease: follow-up of a randomised, placebo-controlled phase I trial
BACKGROUND
Immunisation of patients with Alzheimer's disease with full-length amyloid-beta peptide (Abeta(42)) can clear amyloid plaques from the brain. Our aim was to assess the relation between Abeta(42) immune response, degree of plaque removal, and long-term clinical outcomes.


METHODS
In June, 2003, consent for long-term clinical follow-up, post-mortem neuropathological examination, or both, was sought from 80 patients (or their carers) who had entered a phase I randomised, placebo-controlled trial of immunisation with Abeta(42) (AN1792, Elan Pharmaceuticals) in September, 2000. The follow-up study was completed in September, 2006. Plaques were assessed in terms of the percentage area of the cortex with Abeta immunostaining (Abeta load) and in terms of characteristic histological features reflecting plaque removal. Survival of all 80 individuals until severe dementia or death was assessed with a Cox proportional hazard model.


FINDINGS
20 participants--15 in the AN1792 group, five in the placebo group--died before follow-up started. A further 22 patients--19 in the AN1792 group, three in the placebo group--died during follow-up. Nine of the deceased patients, all in the AN1792 group, had given consent for post-mortem analysis; one of these who did not die with Alzheimer's disease was excluded. In the remaining eight participants who received immunisation and who were examined neuropathologically, mean Abeta load was lower than in an unimmunised control group that was matched for age at death (2.1% [SE 0.7] in treated participants vs 5.1% [0.9] in controls; mean difference 3.0%, 95% CI 0.6-5.4; p=0.02). Although there was considerable variation in Abeta load and degree of plaque removal among immunised participants, the degree of plaque removal varied significantly with mean antibody response attained during the treatment study period (Kruskal-Wallis p=0.02). Seven of the eight immunised patients who underwent post-mortem assessment, including those with virtually complete plaque removal, had severe end stage dementia before death. In the whole cohort, there was no evidence of improved survival (hazard ratio 0.93, 95% CI 0.43-3.11; p=0.86) or of an improvement in the time to severe dementia (1.18, 0.45-3.11; p=0.73) in the AN1792 group versus the placebo group.


INTERPRETATION
Although immunisation with Abeta(42) resulted in clearance of amyloid plaques in patients with Alzheimer's disease, this clearance did not prevent progressive neurodegeneration.
28895177
Copolymer 1 reduces relapse rate and improves disability in relapsing‐remitting multiple sclerosis
we studied copolymer 1 (Copaxone) in a multicenter (11-university) phase III trial of patients with relapsing-remitting multiple sclerosis (MS). Two hundred fifty-one patients were randomized to receive copolymer 1 (n = 125) or placebo (n = 126) at a dosage of 20 mg by daily subcutaneous injection for 2 years. The primary end point was a difference in the MS relapse rate. The final 2-year relapse rate was 1.19 ± 0.13 for patients receiving copolymer 1 and 1.68 ± 0.13 for those receiving placebo, a 29% reduction in favor of copolymer 1 (p = 0.007) (annualized rates = 0.59 for copolymer 1 and 0.84 for placebo). Trends in the proportion of relapse-free patients and median time to first relapse favored copolymer 1. Disability was measured by the Expanded Disability Status Scale (EDSS), using a two-neurologist (examining and treating) protocol. When the proportion of patients who improved, were unchanged, or worsened by ≥1 EDSS step from baseline to conclusion (2 years) was evaluated, significantly more patients receiving copolymer 1 were found to have improved and more receiving placebo worsened (p = 0.037). Patient withdrawals were 19 (15.2%) from the copolymer 1 group and 17 (13.5%) from the placebo group at approximately the same intervals. The treatment was well tolerated. The most common adverse experience was an injection-site reaction. Rarely, a transient self-limited systemic reaction followed the injection in 15.2% of those receiving copolymer 1 and 3.2% of those receiving placebo. This reaction was characterized by flushing or chest tightness with palpitations, anxiety, or dyspnea and commonly lasted for 30 seconds to 30 minutes. This rigorous study confirmed the findings of a previous pilot trial and demonstrated that copolymer 1 treatment can significantly and beneficially alter the course of relapsing-remitting MS in a well-tolerated fashion.
45614988
Nasal vaccination with a proteosome-based adjuvant and glatiramer acetate clears beta-amyloid in a mouse model of Alzheimer disease.
Amyloid beta-peptide (Abeta) appears to play a key pathogenic role in Alzheimer disease (AD). Immune therapy in mouse models of AD via Abeta immunization or passive administration of Abeta antibodies markedly reduces Abeta levels and reverses behavioral impairment. However, a human trial of Abeta immunization led to meningoencephalitis in some patients and was discontinued. Here we show that nasal vaccination with a proteosome-based adjuvant that is well tolerated in humans plus glatiramer acetate, an FDA-approved synthetic copolymer used to treat multiple sclerosis, potently decreases Abeta plaques in an AD mouse model. This effect did not require the presence of antibody, as it was observed in B cell-deficient (Ig mu-null) mice. Vaccinated animals developed activated microglia that colocalized with Abeta fibrils, and the extent of microglial activation correlated strongly with the decrease in Abeta fibrils. Activation of microglia and clearing of Abeta occurred with the adjuvant alone, although to a lesser degree. Our results identify a novel approach to immune therapy for AD that involves clearing of Abeta through the utilization of compounds that have been safely tested on or are currently in use in humans.
21593244
Prototype Alzheimer’s Disease Vaccine Using the Immunodominant B Cell Epitope from β-Amyloid and Promiscuous T Cell Epitope Pan HLA DR-Binding Peptide1
Immunization of amyloid precursor protein transgenic mice with fibrillar β-amyloid (Aβ) prevents Alzheimer’s disease (AD)-like neuropathology. The first immunotherapy clinical trial used fibrillar Aβ, containing the B and T cell self epitopes of Aβ, as the immunogen formulated with QS21 as the adjuvant in the vaccine. Unfortunately, the clinical trial was halted during the phase II stage when 6% of the participants developed meningoencephalitis. The cause of the meningoencephalitis in the patients that received the vaccine has not been definitively determined; however, analysis of two case reports from the AN-1792 vaccine trial suggest that the meningoencephalitis may have been caused by a T cell-mediated autoimmune response, whereas production of anti-Aβ Abs may have been therapeutic to the AD patients. Therefore, to reduce the risk of an adverse T cell-mediated immune response to Aβ immunotherapy we have designed a prototype epitope vaccine that contains the immunodominant B cell epitope of Aβ in tandem with the synthetic universal Th cell pan HLA DR epitope, pan HLA DR-binding peptide (PADRE). Importantly, the PADRE-Aβ1–15 sequence lacks the T cell epitope of Aβ. Immunization of BALB/c mice with the PADRE-Aβ1–15 epitope vaccine produced high titers of anti-Aβ Abs. Splenocytes from immunized mice showed robust T cell stimulation in response to peptides containing PADRE. However, splenocytes from immunized mice were not reactivated by the Aβ peptide. New preclinical trials in amyloid precursor protein transgenic mouse models may help to develop novel immunogen-adjuvant configurations with the potential to avoid the adverse events that occurred in the first clinical trial.
24200961
Intravenous immunoglobulin enhances the clearance of fibrillar amyloid-beta peptide.
Intravenous immunoglobulin (IVIg), a purified immunoglobulin fraction manufactured from the blood of healthy humans, is an FDA-approved treatment for many immune and inflammatory diseases. Recent studies have demonstrated that IVIg therapy has several positive effects on patients with Alzheimer's disease (AD). These include improving cognitive functions and lowering the level of soluble amyloid-beta peptide (AbetaP) in the brain. Nonetheless, the mechanism by which IVIg mediates the clearance of AbetaP from the AD brain currently remains unknown. In this study we investigated the molecular basis for the direct and indirect effects of IVIg on AbetaP clearance using the BV-2 cellular microglia line. Specifically, we show that IVIg dissolves preformed AbetaP fibrils in vitro. Moreover, IVIg increases cellular tolerance to AbetaP, enhances microglial migration toward AbetaP deposits, and mediates phagocytosis of AbetaP. Thus, several mechanisms can be considered when examining the effects of IVIg. Our work supports the hypothesis that IVIg interferes by more than one mechanism in clearing AbetaP from the brains of Alzheimer's patients.
12920580
Antibodies against beta-amyloid reduce Abeta oligomers, glycogen synthase kinase-3beta activation and tau phosphorylation in vivo and in vitro.
Although active and passive immunization against the beta-amyloid peptide (Abeta) of amyloid plaque-bearing transgenic mice markedly reduces amyloid plaque deposition and improves cognition, the mechanisms of neuroprotection and impact on toxic oligomer species are not understood. We demonstrate that compared to control IgG2b, passive immunization with intracerebroventricular (icv) anti-Abeta (1-15) antibody into the AD HuAPPsw (Tg2576) transgenic mouse model reduced specific oligomeric forms of Abeta, including the dodecamers that correlate with cognitive decline. Interestingly, the reduction of soluble Abeta oligomers, but not insoluble Abeta, significantly correlated with reduced tau phosphorylation by glycogen synthase kinase-3beta (GSK-3beta), a major tau kinase implicated previously in mediating Abeta toxicity. A conformationally-directed antibody against amyloid oligomers (larger than tetramer) also reduced Abeta oligomer-induced activation of GSK3beta and protected human neuronal SH-SY5Y cells from Abeta oligomer-induced neurotoxicity, supporting a role for Abeta oligomers in human tau kinase activation. These data suggest that antibodies that are highly specific for toxic oligomer subspecies may reduce toxicity via reduction of GSK-3beta, which could be an important strategy for Alzheimer's disease (AD) therapeutics.
27815828
Imaging of amyloid-β deposits in brains of living mice permits direct observation of clearance of plaques with immunotherapy
Imaging of amyloid-β deposits in brains of living mice permits direct observation of clearance of plaques with immunotherapy
25255471
Peripherally administered antibodies against amyloid β-peptide enter the central nervous system and reduce pathology in a mouse model of Alzheimer disease
One hallmark of Alzheimer disease is the accumulation of amyloid β-peptide in the brain and its deposition as plaques. Mice transgenic for an amyloid β precursor protein (APP) mini-gene driven by a platelet-derived (PD) growth factor promoter (PDAPP mice), which overexpress one of the disease-linked mutant forms of the human amyloid precursor protein, show many of the pathological features of Alzheimer disease, including extensive deposition of extracellular amyloid plaques, astrocytosis and neuritic dystrophy. Active immunization of PDAPP mice with human amyloid β-peptide reduces plaque burden and its associated pathologies. Several hypotheses have been proposed regarding the mechanism of this response. Here we report that peripheral administration of antibodies against amyloid β-peptide, was sufficient to reduce amyloid burden. Despite their relatively modest serum levels, the passively administered antibodies were able to enter the central nervous system, decorate plaques and induce clearance of preexisting amyloid. When examined in an ex vivo assay with sections of PDAPP or Alzheimer disease brain tissue, antibodies against amyloid β-peptide triggered microglial cells to clear plaques through Fc receptor-mediated phagocytosis and subsequent peptide degradation. These results indicate that antibodies can cross the blood–brain barrier to act directly in the central nervous system and should be considered as a therapeutic approach for the treatment of Alzheimer disease and other neurological disorders.
7788624
Intravenous immunoglobulins containing antibodies against β-amyloid for the treatment of Alzheimer’s disease
Objective: Active or passive immunisation can mitigate plaque pathology in murine models of Alzheimer’s disease (AD). Recently, it has been shown that antibodies against β-amyloid (Aβ) are present in human immunoglobulin preparations (IVIgG), which specifically recognise and inhibit the neurotoxic effects of Aβ. This study reports the results from a pilot study using IVIgG in patients with AD. Methods: Five patients with AD were enrolled and received monthly IVIgG over a 6 month period. Efficacy assessment included total Aβ/Aβ1–42 measured in the CSF/serum as well as effects on cognition (ADAS-cog; CERAD) at baseline and at 6 months following IVIgG. Results: Following IVIgG, total Aβ levels in the CSF decreased by 30.1% (17.3–43.5%) compared to baseline (p<0.05). Total Aβ increased in the serum by 233% (p<0.05). No significant change was found in Aβ1–42 levels in the CSF/serum. Using ADAS-cog, an improvement of 3.7±2.9 points was detected. Scores in the MMSE were essentially unchanged (improved in four patients, stable in one patient) following IVIgG compared to baseline. Conclusion: Although the sample size of this pilot study is too small to draw a clear conclusion, the results of this pilot study provide evidence for a more detailed investigation of IVIgG for the treatment of AD.
31018114
Amyloid beta peptide as a vaccine for Alzheimer's disease involves receptor-mediated transport at the blood-brain barrier.
Much research is now focused on a potential vaccine for Alzheimer's disease (AD). Current studies involve administering the amyloid beta peptide (Abeta) in Freund's complete adjuvant, which cannot be used in humans. Our studies show that the immune complex of Abeta is taken up by a receptor-mediated process at the blood-brain barrier (BBB). The success of immunization for AD, therefore, may be critically dependent on circulating Abeta levels which are lower in AD patients compared to AD transgenic mice. Moreover, we have found that modifying the antibody with polyamine increases its BBB permeability and may provide a better approach to passive immunization for Alzheimer's disease.
42802255
Anti-amyloid beta protein antibody passage across the blood–brain barrier in the SAMP8 mouse model of Alzheimer's disease: An age-related selective uptake with reversal of learning impairment
Amyloid beta protein (Abeta) levels are elevated in the brain of Alzheimer's disease patients. Anti-Abeta antibodies can reverse the histologic and cognitive impairments in mice which overexpress Abeta. Passive immunization appears safer than vaccination and treatment of patients will likely require human rather than xenogenic antibodies. Effective treatment will likely require antibody to cross the blood-brain barrier (BBB). Unfortunately, antibodies typically cross the BBB very poorly and accumulate less well in brain than even albumin, a substance nearly totally excluded from the brain. We compared the ability of two anti-Abeta human monoclonal IgM antibodies, L11.3 and HyL5, to cross the BBB of young CD-1 mice to that of young and aged SAMP8 mice. The SAMP8 mouse has a spontaneous mutation that induces an age-related, Abeta-dependent cognitive deficit. There was preferential uptake of intravenously administered L11.3 in comparison to HyL5, albumin, and a control human monoclonal IgM (RF), especially by hippocampus and olfactory bulb in aged SAMP8 mice. Injection of L11.3 into the brains of aged SAMP8 mice reversed both learning and memory impairments in aged SAMP8 mice, whereas IgG and IgM controls were ineffective. Pharmacokinetic analysis predicted that an intravenous dose 1000 times higher than the brain injection dose would reverse cognitive impairments. This predicted intravenous dose reversed the impairment in learning, but not memory, in aged SAMP8 mice. In conclusion, an IgM antibody was produced that crosses the BBB to reverse cognitive impairment in a murine model of Alzheimer's disease.
25585741
Passive Immunization against β-Amyloid Peptide Protects Central Nervous System (CNS) Neurons from Increased Vulnerability Associated with an Alzheimer's Disease-causing Mutation*
To characterize the effects of the familial Alzheimer's disease-causing Swedish mutations of amyloid precursor protein (SwAPP) on the vulnerability of central nervous system neurons, we induced epileptic seizures in transgenic mice expressing SwAPP. The transgene expression did not change the seizure threshold, but consistently more neurons degenerated in brains of SwAPP mice as compared with wild-type littermates. The degenerating neurons were stained both by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling and by Gallyas silver impregnation. A susceptible population of neurons accumulated intracellular Aβ and immunoreacted with antibodies against activated caspase-3. To demonstrate that increased Aβ levels mediated the increased vulnerability, we infused antibodies against Aβ and found a significant reduction in neuronal loss that was paralleled by decreased brain levels of Aβ. Because the SwAPP mice exhibited no amyloid plaques at the age of these experiments, transgenic overproduction of Aβ in brain rendered neurons susceptible to damage much earlier than the onset of amyloid plaque formation. Our data underscore the possibility that Aβ is toxic, that it increases the vulnerability of neurons to excitotoxic events produced by seizures, and that lowering Aβ by passive immunization can protect neurons from Aβ-related toxicity.
23543249
Modulation of microglial activation state following passive immunization in amyloid depositing transgenic mice
Alzheimer's disease is a large and growing health problem. Several lines of transgenic mice overexpressing the amyloid precursor protein (APP) develop both diffuse and compacted amyloid deposits which increase in size and number with age. In the vicinity of compacted deposits, these mice develop neuritic dystrophy and activation of glia. Ultimately, these mice also develop memory deficits. Immunotherapy against the Abeta peptide has been effective in both clearing amyloid deposits from the brain, and improving the mnemonic performance of the transgenic mice. Associated with these actions, are changes in the expression of microglial markers. In some cases, the glial activation markers decline, consistent with reduced provocation from amyloid deposits. However, in a time course study, we found that some markers of microglial activation increase transiently once the immunotherapy is initiated. Still another marker continues to rise for up to 3 months of treatment, and remains elevated even after the parenchymal amyloid deposits are largely removed. These changes are consistent with a shift in the microglial phenotype, transitioning from a condition associated with inflammation and ineffective in clearing Abeta deposits to one with reduced inflammation, and capable of clearing deposited amyloid.
38365675
Human monoclonal antibodies against amyloid-beta from healthy adults
Two anti-amyloid-beta human antibody-producing cell lines were established from amyloid-beta (Abeta)-selected lymphocytes from peripheral blood of healthy adults. ELISA and Western blot analysis showed that the monoclonal antibodies bound with high affinity to the 43 amino acid-long amyloid-beta peptide. The antigen epitope of these antibodies encountered within amino acids 1-16 of the amyloid-beta peptide. The antibodies did not bind to several immunoglobulin light chain amyloids (AL) and amylin. One of the monoclonals was tested by immunohistochemistry for the binding to frozen sections of brains derived from patients with Alzheimer's disease. It specifically and intensively stained diffuse and core amyloid-beta plaques; whereas, sections from normal brains were not stained. Concomitant staining with a commercial mouse anti-amyloid-beta monoclonal antibody co-localized with that of the human antibody. Simultaneous staining with the human antibody and Congo red implied that the antibody binds primarily to an early immature form of beta-amyloid. Human monoclonal antibodies, which resemble physiologically normal non-pathogenic and possibly protective antibodies in healthy adults, might be attractive candidates for immune therapy of Alzheimer's disease.
46290628
The F(ab)'2 fragment of an Abeta-specific monoclonal antibody reduces Abeta deposits in the brain.
This work examines whether administering the F(ab' )2 fragment of an IgG1 monoclonal antibody (mAb) targeting the N-terminal 1-13 amino acids of the beta-amyloid peptide (Abeta mAb) reduces amyloid deposition in Alzheimer's disease (AD). The F(ab')2 fragment was injected intraperitoneally or intracranially into Tg2576 mice, a murine model of human AD. Both routes of administration significantly reduced Abeta plaque formation in the brain, as determined immunohistochemically and by monitoring levels of Abeta1-40 and Abeta1-42 peptide. Use of the F(ab')2 fragment significantly reduced phagocytic infiltration in the CNS when compared to intact mAb. Since IgG1 Abs do not fix complement, these findings suggest that effective in vivo clearance of amyloid deposits can be achieved without stimulation of FcR-reactive phagocytes or activation of the complement cascade.
23569553
Targeting amyloid-beta peptide (Abeta) oligomers by passive immunization with a conformation-selective monoclonal antibody improves learning and memory in Abeta precursor protein (APP) transgenic mice.
Passive immunization of murine models of Alzheimer disease amyloidosis reduces amyloid-beta peptide (Abeta) levels and improves cognitive function. To specifically address the role of Abeta oligomers in learning and memory, we generated a novel monoclonal antibody, NAB61, that preferentially recognizes a conformational epitope present in dimeric, small oligomeric, and higher order Abeta structures but not full-length amyloid-beta precursor protein or C-terminal amyloid-beta precursor protein fragments. NAB61 also recognized a subset of brain Abeta deposits, preferentially mature senile plaques, and amyloid angiopathy. Using NAB61 as immunotherapy, we showed that aged Tg2576 transgenic mice treated with NAB61 displayed significant improvements in spatial learning and memory relative to control mice. These data implicated Abeta oligomers as a pathologic substrate for cognitive decline in Alzheimer disease.
20419987
In vivo targeting of antibody fragments to the nervous system for Alzheimer’s disease immunotherapy and molecular imaging of amyloid plaques
Targeting therapeutic or diagnostic proteins to the nervous system is limited by the presence of the blood–brain barrier. We report that a F(ab′)2 fragment of a monoclonal antibody against fibrillar human Aβ42 that is polyamine (p)‐modified has increased permeability at the blood–brain barrier, comparable binding to the antigen, and comparable in vitro binding to amyloid plaques in Alzheimer’s disease (AD) transgenic mouse brain sections. Intravenous injection of the pF(ab′)24.1 in the AD transgenic mouse demonstrated efficient targeting to amyloid plaques throughout the brain, whereas the unmodified fragment did not. Removal of the Fc portion of this antibody derivative will minimize the inflammatory response and cerebral hemorrhaging associated with passive immunization and provide increased therapeutic potential for treating AD. Coupling contrast agents/radioisotopes might facilitate the molecular imaging of amyloid plaques with magnetic resonance imaging/positron emission tomography. The efficient delivery of immunoglobulin G fragments may also have important applications to other neurodegenerative disorders or for the generalized targeting of nervous system antigens.
45540538
Monoclonal antibodies that target pathological assemblies of Aβ
Amyloid beta (Aβ) immunotherapy for Alzheimer's disease has shown initial success in mouse models of Alzheimer's disease and in human patients. However, because of meningoencephalitis in clinical trials of active vaccination, approaches using therapeutic antibodies may be preferred. As a novel antigen to generate monoclonal antibodies, the current study has used Aβ oligomers (amyloid β‐derived diffusible ligands, ADDLs), pathological assemblies known to accumulate in Alzheimer's disease brain. Clones were selected for the ability to discriminate Alzheimer's disease from control brains in extracts and tissue sections. These antibodies recognized Aβ oligomers and fibrils but not the physiologically prevalent Aβ monomer. Discrimination derived from an epitope found in assemblies of Aβ1–28 and ADDLs but not in other sequences, including Aβ1–40. Immunoneutralization experiments showed that toxicity and attachment of ADDLs to synapses in culture could be prevented. ADDL‐induced reactive oxygen species (ROS) generation was also inhibited, establishing this response to be oligomer‐dependent. Inhibition occurred whether ADDLs were prepared in vitro or obtained from Alzheimer's disease brain. As conformationally sensitive monoclonal antibodies that selectively immunoneutralize binding and function of pathological Aβ assemblies, these antibodies provide tools by which pathological Aβ assemblies from Alzheimer's disease brain might be isolated and evaluated, as well as offering a valuable prototype for new antibodies useful for Alzheimer's disease therapeutics.
6501823
Meningoencephalitis associated with passive immunization of a transgenic murine model of Alzheimer's amyloidosis
Immunization against the Aβ peptide reverses the pathologic and behavioral manifestations of Alzheimer's disease in murine models. Since active immunization is associated with an autoimmune meningoencephalitis in a subset of humans, passive transfer of anti‐Aβ immunoglobulin is being pursued as a potentially safer alternative. We have identified cases of meningoencephalitis subsequent to peripheral and intracerebral passive immunization of Tg2576 mice. The vasocentric mononuclear infiltrate localized only to brain regions affected by Aβ amyloid deposits suggesting that the inflammatory reaction was Aβ specific. This report indicates that current passive immunization in humans should proceed with careful regard for autoimmune complications.
453000
HSV amplicon-mediated Aβ vaccination in Tg2576 mice: differential antigen-specific immune responses
Given the participation of amyloid beta (Abeta) in Alzheimer's disease (AD) pathogenesis the derivation of experimental therapeutics to prevent Abeta fibrillogenesis and/or enhance removal of parenchymal amyloid deposits represent viable disease-modifying approaches. Active Abeta-based immunotherapies have shown promise in mouse AD models, but application in human trials was accompanied by moderate brain inflammation in a subset of patients. Immune-shaping vaccine platforms may mitigate adverse effects. Herein, we describe the use of herpes simplex virus (HSV)-derived amplicons to elicit distinctive immune responses against Abeta. Two vaccine vectors were constructed: one expressing Abeta1-42 alone (HSVAbeta), and a second expressing Abeta1-42 fused with the molecular adjuvant tetanus toxin Fragment C (HSVAbeta/TtxFC). Peripheral administration of these vaccines augmented humoral responses to Abeta and reduced CNS Abeta deposition in Tg2576 AD mice. Interestingly and unexpectedly, HSVAbeta vaccination was uniquely toxic and incited the expression of pro-inflammatory molecule transcripts within the hippocampi of Tg2576 mice, suggesting that this paradigm may serve as a relevant model to study Abeta vaccine-elicited CNS inflammatory syndromes.
619427
Is there a future for vaccination as a treatment for Alzheimer’s disease?
Vaccination of APP transgenic mice with Abeta has been shown to prevent amyloid deposits. A clinical trial of Abeta vaccination in Alzheimer's disease (AD) was halted due to serious neurological complications developing in some patients. Such complications were not observed in transgenic mice. Since human APP is not a mouse self-protein, vaccination of mice with Abeta should not produce an autoimmune reaction although this would be anticipated in AD. Moreover, mouse C1q poorly recognizes human Abeta so complement activation is much weaker in transgenic mice than in AD. Vaccination will increase complement activation through formation of antigen-antibody complexes. In mice this will enhance phagocytosis. But in AD, where complement is already overactivated, and where the senile plaques are relatively insoluble, this stimulation should increase production of the membrane attack complex, adding to the autodestruction of neurons. The future of vaccination as a therapy for AD will require surmounting the problems of autoimmune reactions generally and autotoxic complement activation specifically.
14004286
Research criteria for the diagnosis of Alzheimer's disease: genetic risk factors, blood biomarkers and olfactory dysfunction
We note with interest the recently proposed new diagnostic framework published in Lancet Neurology entitled “Research criteria for the diagnosis of Alzheimer's disease: revising the NINCDS-ADRDA criteria” by Dubois et al. (2007).