Abeta42 gene vaccine prevents Abeta42 deposition in brain of double transgenic mice

DNA Aβ42 immunization via needle-less Jet injection in mice and rabbits as potential immunotherapy for Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia found in the elderly and disease progression is associated with accumulation of Amyloid beta 1-42 (Aβ42) in brain. An immune-mediated approach as a preventive intervention to reduce amyloid plaques without causing brain inflammation is highly desirable for future clinical use. Genetic immunization, in which the immunizing agent is DNA encoding Aβ42, has great potential because the immune response to DNA delivered into the skin is generally non-inflammatory, and thus differs quantitatively and qualitatively from immune responses elicited by peptides, which are inflammatory with production of IFNγ and IL-17 cytokines by activated T cells. DNA immunization has historically been proven difficult to apply to larger mammals. A potential barrier to use DNA immunization in large mammals is the method for delivery of the DNA antigen. We tested jet injection in mice and rabbits and found good antibody production and safe immune responses (no inflammatory cytokines). We found significant reduction of amyloid plaques and Aβ peptides in brains of the DNA Aβ42 immunized 3xTg-AD mouse model. This study was designed to optimize DNA delivery for possible testing of the DNA Aβ42 vaccine for AD prevention in a clinical trial.

A Review of Brain-Targeted Nonviral Gene-Based Therapies for the Treatment of Alzheimer's Disease

Diseases of the central nervous system (CNS) are difficult to treat owing to the complexity of the brain and the presence of a natural blood-brain-barrier (BBB). Alzheimer's disease (AD) is one of the major progressive and currently incurable neurodegenerative disorders of the CNS, which accounts for 60-80% of cases of dementia. The pathophysiology of AD involves the accumulation of amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs) in the brain. Additionally, synaptic loss and imbalance of neuronal signaling molecules are characterized as important markers of AD. Existing treatments of AD help in the management of its symptoms and aim toward the maintenance of cognitive functions, behavior, and attenuation of gradual memory loss. Over the past decade, nonviral gene therapy has attracted increasing interest due to its various advantages over its viral counterparts. Moreover, advancements in nonviral gene technology have led to their increasing contributions in clinical trials. However, brain-targeted nonviral gene delivery vectors come across various extracellular and intracellular barriers, limiting their ability to transfer the therapeutic gene into the target cells. Chief barriers to nonviral gene therapy have been discussed briefly in this review. We have also highlighted the rapid advancement of several nonviral gene therapies for AD, which are broadly categorized into physical and chemical methods. These methods aim to modulate Aβ, beta-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1), apolipoprotein E, or neurotrophic factors' expression in the CNS. Overall, this review discusses challenges and recent advancements of nonviral gene therapy for AD.

Reactive astrocytes as treatment targets in Alzheimer's disease-Systematic review of studies using the APPswePS1dE9 mouse model

Astrocytes regulate synaptic communication and are essential for proper brain functioning. In Alzheimer's disease (AD) astrocytes become reactive, which is characterized by an increased expression of intermediate filament proteins and cellular hypertrophy. Reactive astrocytes are found in close association with amyloid-beta (Aβ) deposits. Synaptic communication and neuronal network function could be directly modulated by reactive astrocytes, potentially contributing to cognitive decline in AD. In this review, we focus on reactive astrocytes as treatment targets in AD in the APPswePS1dE9 AD mouse model, a widely used model to study amyloidosis and gliosis. We first give an overview of the model; that is, how it was generated, which cells express the transgenes, and the effect of its genetic background on Aβ pathology. Subsequently, to determine whether modifying reactive astrocytes in AD could influence pathogenesis and cognition, we review studies using this mouse model in which interventions were directly targeted at reactive astrocytes or had an indirect effect on reactive astrocytes. Overall, studies specifically targeting astrocytes to reduce astrogliosis showed beneficial effects on cognition, which indicates that targeting astrocytes should be included in developing novel therapies for AD.

Active full-length DNA Aβ42 immunization in 3xTg-AD mice reduces not only amyloid deposition but also tau pathology

Background

Alzheimer’s disease (AD) is the most well-known and most common type of age-related dementia. Amyloid deposition and hyperphosphorylation of tau protein are both pathological hallmarks of AD. Using a triple-transgenic mouse model (3xTg-AD) that develops plaques and tangles in the brain similar to human AD, we provide evidence that active full-length DNA amyloid-β peptide 1–42 (Aβ₄₂) trimer immunization leads to reduction of both amyloid and tau aggregation and accumulation.

Methods

Immune responses were monitored by enzyme-linked immunosorbent assay (ELISA) (antibody production) and enzyme-linked immunospot (cellular activation, cytokine production). Brains from 20-month-old 3x Tg-AD mice that had received DNA Aβ₄₂ immunotherapy were compared with brains from age- and gender-matched transgenic Aβ₄₂ peptide-immunized and control mice by histology, Western blot analysis, and ELISA. Protein kinase activation and kinase levels were studied in Western blots from mouse hemibrain lysates.

Results

Quantitative ELISA showed a 40% reduction of Aβ₄₂ peptide and a 25–50% reduction of total tau and different phosphorylated tau molecules in the DNA Aβ₄₂ trimer-immunized 3xTg-AD mice compared with nonimmunized 3xTg-AD control animals. Plaque and Aβ peptide reductions in the brain were due to the anti-Aβ antibodies generated following the immunizations. Reductions of tau were likely due to indirect actions such as less Aβ in the brain resulting in less tau kinase activation.

Conclusions

The significance of these findings is that DNA Aβ₄₂ trimer immunotherapy targets two major pathologies in AD—amyloid plaques and neurofibrillary tangles—in one vaccine without inducing inflammatory T-cell responses, which carry the danger of autoimmune inflammation, as found in a clinical trial using active Aβ₄₂ peptide immunization in patients with AD (AN1792).

Intradermal active full-length DNA Aβ42 immunization via electroporation leads to high anti-Aβ antibody levels in wild-type mice

Aβ immunotherapies with anti-Aβ antibody responses have high potential as possible prevention treatment for Alzheimer's disease. We have previously shown that active DNA Aβ1-42 immunization via gene gun delivery led to a non-inflammatory immune response resulting in decreased Aβ levels in brains of an immunized AD mouse model. To make DNA vaccination more applicable for clinical use, we used here intradermal electroporation. With fine tuning of the electropulse parameters, high antibody levels and low levels of inflammatory cytokines in the cellular immunoassays were observed. Full-length DNA Aβ1-42 immunization delivered via electroporation has potential to be used in the clinical setting.

Astrocytes with previous chronic exposure to amyloid β-peptide fragment 1-40 suppress excitatory synaptic transmission

Synaptic dysfunction and neuronal death are responsible for cognitive and behavioral deficits in Alzheimer's disease (AD). It is well known that such neurological abnormalities are preceded by long-term exposure of amyloid β-peptide (Aβ) and/or hyperphosphorylated tau prior. In addition to the neurological deficit, astrocytes as a major glial cell type in the brain, significantly participate in the neuropathogenic mechanisms underlying synaptic modulation. Although astrocytes play a significant key role in modulating synaptic transmission, little is known on whether astrocyte dysfunction caused by such long-term Aβ exposure affects synapse formation and function. Here, we show that synapse formation and synaptic transmission are attenuated in hippocampal-naïve neurons co-cultured with astrocytes that have previously experienced chronic Aβ_1-40 exposure. In this abnormal astrocytic condition, hippocampal neurons exhibit decrements of evoked excitatory post-synaptic currents (EPSCs) and miniature EPSC frequency. Furthermore, size of readily releasable synaptic pools and number of excitatory synapses were also significantly decreased. Contrary to these negative effects, release probability at individual synapses was significantly increased in the same astrocytic condition. Taken together, our data indicate that lower synaptic transmission caused by astrocytes previously, and chronically, exposed to Aβ1-40 is attributable to a small number of synapses with higher release probability.

Genomics of Alzheimer Disease: A Review

IMPORTANCE

To provide a comprehensive review of knowledge of the genomics of Alzheimer disease (AD) and DNA amyloid β 42 (Aβ42) vaccination as a potential therapy.

OBSERVATIONS

Genotype-phenotype correlations of AD are presented to provide a comprehensive appreciation of the spectrum of disease causation. Alzheimer disease is caused in part by the overproduction and lack of clearance of Aβ protein. Oligomer Aβ, the most toxic species of Aβ, causes direct injury to neurons, accompanied by enhanced neuroinflammation, astrocytosis and gliosis, and eventually neuronal loss. The strongest genetic evidence supporting this hypothesis derives from mutations in the amyloid precursor protein (APP) gene. A detrimental APP mutation at the β-secretase cleavage site linked to early-onset AD found in a Swedish pedigree enhances Aβ production, in contrast to a beneficial mutation 2 residues away in APP that reduces Aβ production and protects against the onset of sporadic AD. A number of common variants associated with late-onset AD have been identified including apolipoprotein E, BIN1, ABC7, PICALM, MS4A4E/MS4A6A, CD2Ap, CD33, EPHA1, CLU, CR1, and SORL1. One or 2 copies of the apolipoprotein E ε4 allele are a major risk factor for late-onset AD. With DNA Aβ42 vaccination, a Th2-type noninflammatory immune response was achieved with a downregulation of Aβ42-specific effector (Th1, Th17, and Th2) cell responses at later immunization times. DNA Aβ42 vaccination upregulated T regulator cells (CD4+, CD25+, and FoxP3+) and its cytokine interleukin 10, resulting in downregulation of T effectors.

CONCLUSIONS AND RELEVANCE

Mutations in APP and PS-1 and PS-2 genes that are associated with early-onset, autosomal, dominantly inherited AD, in addition to the at-risk gene polymorphisms responsible for late-onset AD, all indicate a direct and early role of Aβ in the pathogenesis of AD. A translational result of genomic research has been Aβ-reducing therapies including DNA Aβ42 vaccination as a promising approach to delay or prevent this disease.

Evaluation of a DNA Aβ42 vaccine in adult rhesus monkeys (Macaca mulatta): antibody kinetics and immune profile after intradermal immunization with full-length DNA Aβ42 trimer

Background

Aggregated amyloid-β peptide 1–42 (Aβ42), derived from the cellular amyloid precursor protein, is one of the pathological hallmarks of Alzheimer’s disease (AD). Although active immunization against Aβ42 peptide was successful in AD mouse models and led to removal of plaques and improved memory, a similar clinical trial in humans (Aβ42 peptide immunization with QS-21 adjuvant) was stopped in phase II, when 6% of the treated patients developed encephalitis. Currently ongoing passive immunizations with the injection of preformed monoclonal antibodies against different epitopes within the Aβ_1–42 peptide, which do not lead to activation of the immune system, have shown some effects in slowing AD pathology. Active DNA Aβ42 immunizations administered with the gene gun into the skin are noninflammatory because they activate a different T-cell population (Th2) with different cytokine responses eliciting a different humoral immune response. We present our findings in rhesus macaques that underwent the DNA Aβ42 immunization via gene gun delivery into the skin.

Methods

Six rhesus monkeys received two different doses of a DNA Aβ42 trimer vaccine. The humoral immune response was analyzed from blood throughout the study, and cellular immune responses were determined in peripheral blood mononuclear cells (PBMCs) after three and six immunizations.

Results

DNA Aβ42 trimer immunization led to high titer antibody responses in the nonhuman primate (NHP) model. Antibodies generated in the rhesus monkeys following DNA Aβ42 immunization detected amyloid plaques consisting of human Aβ42 peptide in the brain of the triple-transgenic AD mouse model. T-cell responses showed no interferon (IFN)-γ- and interleukin (IL)-17-producing cells from PBMCs in Enzyme-Linked ImmunoSpot assays after three immunization time points. At six immunization time points, IFN-γ- and IL-17-producing cells were found in immunized animals as well as in control animals and were thus considered nonspecific and not due to the immunization regimen. IFN-γ and IL-17 secretion in response to Aβ42 peptide restimulation became undetectable after a 3-month rest period.

Conclusions

Intradermal DNA Aβ42 immunization delivered with the gene gun produces a high antibody response in NHPs and is highly likely to be effective and safe in a clinical AD prevention trial in patients.

Evaluation of a DNA Aβ42 Vaccine in Aged NZW Rabbits: Antibody Kinetics and Immune Profile after Intradermal Immunization with Full-Length DNA Aβ42 Trimer

A pathological hallmark of Alzheimer's disease (AD) are amyloid plaques in the brain consisting of aggregated amyloid-β 42 peptide (Aβ42) derived from cellular amyloid-β protein precursor (AβPP). Based on successful experiments in mouse AD models, active immunization with Aβ42 peptide and passive immunizations with anti-Aβ42 antibodies were started in clinical trials. Active Aβ42 peptide immunization in humans had led to an inflammatory autoimmune response, and the trial was stopped. Passive immunizations had shown some effects in slowing AD pathology. Active DNA Aβ42 immunizations administered with the gene gun into the skin elicits a different immune response and is non-inflammatory. While in rodents, good responses had been found for this type of immunization, positive results in larger mammals are missing. We present here results from sixteen New Zealand White Rabbits, which underwent intradermal DNA Aβ42 immunization via gene gun. The humoral immune response was analyzed from blood throughout the study, and cellular immune responses were determined from spleens at the end of the study. A good anti-Aβ antibody response was found in the rabbit model. The T cell response after re-stimulation in cell culture showed no IFNγ producing cells when ELISPOT assays were analyzed from PBMC, but low numbers of IFNγ and IL-17 producing cells were found in ELISPOTS from spleens (both 5 immunizations). Brains from immunized rabbits showed no signs of encephalitis. Based on these results, DNA Aβ42 immunization is highly likely to be safe and effective to test in a possible clinical AD prevention trial in patients.

The DIAN-TU Next Generation Alzheimer's prevention trial: Adaptive design and disease progression model

INTRODUCTION

The Dominantly Inherited Alzheimer Network Trials Unit (DIAN-TU) trial is an adaptive platform trial testing multiple drugs to slow or prevent the progression of Alzheimer's disease in autosomal dominant Alzheimer's disease (ADAD) families. With completion of enrollment of the first two drug arms, the DIAN-TU now plans to add new drugs to the platform, designated as the Next Generation (NexGen) prevention trial.

METHODS

In collaboration with ADAD families, philanthropic organizations, academic leaders, the DIAN-TU Pharma Consortium, the National Institutes of Health, and regulatory colleagues, the DIAN-TU developed innovative clinical study designs for the DIAN-TU NexGen prevention trial.

RESULTS

Our expanded trial toolbox consists of a disease progression model for ADAD, primary end point DIAN-TU cognitive performance composite, biomarker development, self-administered cognitive assessments, adaptive dose adjustments, and blinded data collection through the last participant completion.

CONCLUSION

These steps represent elements to improve efficacy of the adaptive platform trial and a continued effort to optimize prevention and treatment trials in ADAD.

Amyloid-β immunization enhances neurogenesis and cognitive ability in neonatal mice

Whether Aβ actually has a physiological as well as a pathological role is not known. In order to investigate the effect of endogenous Aβ, wild type C57BL/6 mice were immunized with human or mouse derived Aβ1-42. The anti-Aβ antibody concentrations were increased in both treated groups. Compared to the human Aβ1-42 treated group, level of serum Aβ significantly decreased in mouse Aβ1-42 treated group. Western blot results revealed that these two derived Aβ1-42 had no cross-reaction. The new dentate granule survival cells increased in Aβ1-42 immunization groups, indicated by more BrdU+/NeuN+ and BrdU+/DCX+ cells as compared to PBS-treated group, accompanied by behavioral performance improving in a hippocampus-dependent learning task. Immunohistochemical analysis showed that BrdU+/Iba1+ cells also increased, however new born astrocytes (BrdU+/GFAP+) were unaffected in all treated mice. Interestingly, according the results of ELISA analysis both vaccines up-regulated IL-4 and IFN-γ levels in the brains and sera, but the TNF-α level did not changed. Of note, human Aβ1-42 immunization in neonatal mice enhanced neurogenesis and cognitive ability, might via Aβ immune response rather than cleaning endogenous Aβ.

A noninflammatory immune response in aged DNA Aβ42-immunized mice supports its safety for possible use as immunotherapy in AD patients

Aging in the immune system results in tendency to proinflammatory responses. Intradermal DNA immunization showed Th2 polarized noninflammatory immune responses. We tested here 18-month-old mice which were immunized with Aβ42 peptide, DNA Aβ42 trimer, or 2 different prime boost protocols identical to previous experiments. High Aβ42 antibody levels were found in aged mice which had received peptide immunizations (900 μg/mL plasma), and in mice which had received peptide prime and DNA boost immunizations (500 μg/mL), compared with antibodies in DNA Aβ42 immunized mice with 50 μg/mL. Although we found T-cell proliferation and inflammatory cytokines in mice which had received peptide or prime boost immunization, these were not found in DNA-immunized mice. The results are concordant with proinflammatory responses because of immunosenescence and contraindicate the use of Aβ42 peptide immunizations or prime boost immunization protocols for the use in elderly Alzheimer's disease patients. DNA Aβ42 immunization only on the other hand does lead to effective levels of antibodies without inflammatory cytokine or T-cell responses in the aged animal model tested.

Co-stimulation with TNF receptor superfamily 4/25 antibodies enhances in-vivo expansion of CD4+CD25+Foxp3+ T cells (Tregs) in a mouse study for active DNA Aβ42 immunotherapy

The study was designed to test DNA Aβ42 immunization in mice as alternative approach for possible active immunotherapy in Alzheimer patients. As results, we found polarized Th2 immune responses, efficient Aβ42 antibody levels, and disappearance of antigen specific T cells. In-vivo TNFRSF4/25 antibody co-stimulation enhanced Aβ42 specific T cell responses with initial Th2 expansion and subsequent development of Aβ42 specific CD4+CD25+Foxp3+ cells. It showed that Th2 biased responses due to gene gun immunizations propagate the development of regulatory T cells. In conclusion, full-length DNA Aβ42 immunization into skin results in a regulatory response with minimal risk of inflammation and autoimmunity.

Epitope-based DNA vaccine for Alzheimer's disease: translational study in macaques

BACKGROUND

Clinical trials with passive and active Alzheimer's disease (AD) vaccines suggest that early interventions are needed for improvement of cognitive and/or functional performance in patients, providing impetus for the development of safe and immunologically potent active vaccines targeting amyloid β (Aβ). The AN-1792 trial has indicated that Aβ-specific T cells may be unsafe for humans; therefore, other vaccines based on small Aβ epitopes are undergoing preclinical and clinical testing.

METHODS

Humoral and cellular immune responses elicited in response to a novel DNA epitope-based vaccine (AV-1955) delivered to rhesus macaques using the TriGrid electroporation device were evaluated. Functional activities of anti-Aβ antibodies generated in response to vaccination were assessed in vitro.

RESULTS

AV-1955 generates long-term, potent anti-Aβ antibodies and cellular immune responses specific to foreign T-helper epitopes but not to self-Aβ.

CONCLUSIONS

This translational study demonstrates that a DNA-based epitope vaccine for AD could be appropriate for human clinical testing.

The MultiTEP platform-based Alzheimer's disease epitope vaccine activates a broad repertoire of T helper cells in nonhuman primates

BACKGROUND

As a prelude to clinical trials we have characterized B- and T-cell immune responses in macaques to AD vaccine candidates: AV-1955 and its slightly modified version, AV-1959 (with 3 additional promiscuous Th epitopes).

METHODS

T- and B-cell epitope mapping was performed using the ELISPOT assay and competition ELISA, respectively.

RESULTS

AV-1955 and AV-1959 did not stimulate potentially harmful autoreactive T cells, but instead activated a broad but individualized repertoire of Th cells specific to the MultiTEP platform in macaques. Although both vaccines induced robust anti-Aβ antibody responses without producing antibodies specific to Th epitopes of MultiTEP platforms, analyses of cellular immune responses in macaques demonstrated that the addition of Th epitopes in the case of AV-1959 created a more potent, superior vaccine.

CONCLUSION

AV-1959 is a promising vaccine candidate capable of producing therapeutically potent anti-amyloid antibody in a broader population of vaccinated subjects with high MHC class II gene polymorphisms.

Immunogenicity of DNA- and recombinant protein-based Alzheimer disease epitope vaccines

Alzheimer disease (AD) process involves the accumulation of amyloid plaques and tau tangles in the brain, nevertheless the attempts at targeting the main culprits, neurotoxic β-amyloid (Aβ) peptides, have thus far proven unsuccessful for improving cognitive function. Important lessons about anti-Aβ immunotherapeutic strategies were learned from the first active vaccination clinical trials. AD progression could be safely prevented or delayed if the vaccine (1) induces high titers of antibodies specific to toxic forms of Aβ; (2) does not activate the harmful autoreactive T cells that may induce inflammation; (3) is initiated before or at least at the early stages of the accumulation of toxic forms of Aβ. Data from the recent passive vaccination trials with bapineuzumab and solanezumab also indicated that anti-Aβ immunotherapy might be effective in reduction of the AD pathology and even improvement of cognitive and/or functional performance in patients when administered early in the course of the disease. For the prevention of AD the active immunization strategy may be more desirable than passive immunotherapy protocol and it can offer the potential for sustainable clinical and commercial advantages. Here we discuss the active vaccine approaches, which are still in preclinical development and vaccines that are already in clinical trials.

Active immunotherapy options for Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia and a major contributor to disability and dependency among older people. AD pathogenesis is associated with the accumulation of amyloid-beta protein (Aβ) and/or hyperphosphorylated tau protein in the brain. At present, current therapies provide temporary symptomatic benefit, but do not treat the underlying disease. Recent research has thus focused on investigating the molecular and cellular pathways and processes involved in AD pathogenesis to support the development of effective disease-modifying agents. In accordance with the existing Aβ-cascade hypothesis for AD pathogenesis, immunotherapy has been the most extensively studied approach in Aβ-targeted therapy. Both passive and active immunotherapies have been shown to effectively reduce Aβ accumulation and prevent downstream pathology in preclinical models. Following AN1792, second-generation active immunotherapies have shown promising results in terms of antibody response and safety. Comparatively, tau immunotherapy is not as advanced, but preclinical data support its development into clinical trials. Results from active amyloid-based immunotherapy studies in preclinical models indicate that intervention appears to be more effective in early stages of amyloid accumulation, highlighting the importance of diagnosing AD as early as possible and undertaking clinical trials at this stage. This strategy, combined with improving our understanding of the complex AD pathogenesis, is imperative to the successful development of these disease-modifying agents. This paper will review the active immunotherapies currently in development, including the benefits and challenges associated with this approach.

Pharmacogenomics of Alzheimer's disease: novel therapeutic strategies for drug development

Alzheimer's disease (AD) is a major problem of health and disability, with a relevant economic impact on our society. Despite important advances in pathogenesis, diagnosis, and treatment, its primary causes still remain elusive, accurate biomarkers are not well characterized, and the available pharmacological treatments are not cost-effective. As a complex disorder, AD is a polygenic and multifactorial clinical entity in which hundreds of defective genes distributed across the human genome may contribute to its pathogenesis. Diverse environmental factors, cerebrovascular dysfunction, and epigenetic phenomena, together with structural and functional genomic dysfunctions, lead to amyloid deposition, neurofibrillary tangle formation, and premature neuronal death, the major neuropathological hallmarks of AD. Future perspectives for the global management of AD predict that genomics and proteomics may help in the search for reliable biomarkers. In practical terms, the therapeutic response to conventional drugs (cholinesterase inhibitors, multifactorial strategies) is genotype-specific. Genomic factors potentially involved in AD pharmacogenomics include at least five categories of gene clusters: (1) genes associated with disease pathogenesis; (2) genes associated with the mechanism of action of drugs; (3) genes associated with drug metabolism (phase I and II reactions); (4) genes associated with drug transporters; and (5) pleiotropic genes involved in multifaceted cascades and metabolic reactions. The implementation of pharmacogenomic strategies will contribute to optimize drug development and therapeutics in AD and related disorders.

Personalized Medicine of Alzheimer’s Disease

Alzheimer’s disease (AD) is a major problem of health and disability, with a relevant economic impact on society (e.g., €177 billion in Europe). Despite important advances in pathogenesis, diagnosis, and treatment, The primary causes of AD remain elusive, accurate biomarkers are not well characterized, and available pharmacological treatments are not cost-effective. As a complex disorder, AD is polygenic and multifactorial: hundreds of defective genes distributed across the human genome may contribute to its pathogenesis (with the participation of diverse environmental factors, cerebrovascular dysfunction, and epigenetic phenomena) and lead to amyloid deposition, neurofibrillary tangle formation, and premature neuronal death. Future perspectives for the global management of AD predict that structural and functional genomics and proteomics may help in the search for reliable biomarkers, and that pharmacogenomics may be an option in optimizing drug development and therapeutics.

Immunotherapeutic efficiency of a tetravalent Aβ1-15 vaccine in APP/PS1 transgenic mice as mouse model for Alzheimer's disease

Immunization with synthetic, preaggregated β-amyloid (Aβ) was the first treatment approach able to dramatically reduce brain Aβ pathology in Alzheimer's disease (AD) animal models. For the development of a safe vaccine, we investigated whether 4Aβ1-15 (four tandem repeats of GPGPG-linked Aβ1-15 sequences) had therapeutic effects in the APP/PS1 transgenic mice model of AD. We described the production of anti-Aβ antibodies in APP/PS1 mice immunized with 4Aβ1-15 mixed with MF59 adjuvant. The anti-Aβ antibody concentrations were increased which bound to AD plaques, markedly reduced Aβ pathology in transgenic AD mice and levels of intracerebral Aβ (soluble and insoluble), whereas increased serum Aβ levels. Immunization via 4Aβ1-15 (mainly of the IgG1 Class) may induce a non-inflammatory Th2 reaction. Immunohistochemistry analysis of MHC Class II and CD45 revealed that microglial cells were in a less activated state. Of note, 4Aβ1-15-immunized mice showed improved acquisition of memory compared with controls in a reference-memory Morris water-maze behavior test. The data identify the novel immunogen 4Aβ1-15 as a promising new tool for AD immunotherapy.

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

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

Advances in the development of vaccines for Alzheimer's disease

One of the challenges of our society is to find a treatment or cure for Alzheimer's disease (AD). AD is the leading form of age-related dementia and with the increase of life expectancy worldwide, the social and economic burden from this disease will increase dramatically. It is a progressive and, in regard to clinical scores, a highly variable disease. AD pathogenesis has been associated with the accumulation, aggregation, and deposition of amyloid beta (Abeta) peptides in the brain. Hallmarks of AD are the amyloid plaques consisting of fibrillar Abeta and neurofibrillary tangles which are intracellular fibrils of hyperphosphorylated tau protein that develop later in this disease. The amyloid cascade hypothesis postulates that Abeta deposition is an initial event in the multifactorial pathogenesis and Abeta deposition may precede AD symptoms in some patients by at least 20 years. Amyloid beta therapy with active and passive immunizations against Abeta has a high possibility to be effective in removing Abeta from brain and might thus prevent the downstream pathology. Since 2000 a number of clinical trials for AD immunotherapy have started, have failed, and are continuing to be pursued. This article will review these clinical trials and ongoing research in this regard.

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.

Feasibility of an early Alzheimer's disease immunosignature diagnostic test

A practical diagnostic test is needed for early Alzheimer's disease (AD) detection. Immunosignaturing, a technology that employs antibody binding to a random-sequence peptide microarray, generates profiles that distinguish transgenic mice engineered with familial AD mutations (APPswe/PSEN1-dE9) from non-transgenic littermates. It can also detect an AD-like signature in humans. Here, we assess the changes in the immunosignature at different time points of the disease in mice and humans. We also evaluate the accuracy of the late-stage signature as a test to discriminate between young mice with familial AD mutations from non-transgenic littermates. Plasma samples from AD patients were assayed 3-12 months apart, while APPswe/PSEN1-dE9 and non-transgenic controls supplied plasma at monthly intervals until they reached 15 months of age. Microarrays with 10,000 random-sequence peptides were used to compare antibody binding patterns. These patterns gradually changed over the life-span of mice. Strong, characteristic signatures were observed in transgenic mice at early, mid and late stages, but these profiles had minimal overlap. The signature of young transgenic mice had an error rate of 18% at classifying plasma samples from late-stage transgenic mice. Conversely, the late-stage transgenic mice signature discriminated between young transgenic mice and littermates with an error rate of 21%. Less distinctive profiles were recognizable throughout the transgenic mice lifespan, being detectable as early as 2 months. The human signature had minimal change on short-term follow-up. Our results call for a reappraisal of the way incipient AD is studied, as biomarkers seen in late-stages of the disease may not be relevant in earlier stages.

A peptide prime-DNA boost immunization protocol provides significant benefits as a new generation Aβ42 DNA vaccine for Alzheimer disease

Immunotherapy has the potential to provide a possible treatment therapy to prevent or delay Alzheimer disease. In a clinical trial (AN1792) in which patients received this immunotherapy and received active Aβ1-42 peptide immunizations, treatment was stopped when 6% of patients showed signs of meningoencephalitis. Follow up on these patients led to the conclusion that the antibody response was beneficial in removing Aβ1-42 from brain but an accompanying inflammatory Th1 T cell response was harmful. As a safe alternative treatment targeting the same self protein, Aβ1-42, in brain, we and others are working on a DNA Aβ1-42 immunization protocol as the immune response to DNA immunizations differs in many aspects from immunizations with peptide antigens. Because the immune response to DNA vaccination has different kinetics and has a significantly lower antibody production, we evaluated two different prime boost regimens, Aβ1-42 DNA prime/Aβ1-42 peptide boost and Aβ1-42 peptide prime/Aβ1-42 DNA boost for their effectiveness in antibody production and possible side effects due to inflammatory T cell responses. While both boost regimes significantly enhanced the specific antibody production with comparable antibody concentrations, the absence of the Aβ1-42 T cell response (no proliferation and no cytokine production) is consistent with our previous findings using this DNA Aβ1-42 trimer immunization and greatly enhances the safety aspect for possible clinical use.

Developing an international network for Alzheimer research: The Dominantly Inherited Alzheimer Network

The Dominantly Inherited Alzheimer Network (DIAN) is a collaborative effort of international Alzheimer disease (AD) centers that are conducting a multifaceted prospective biomarker study in individuals at-risk for autosomal dominant AD (ADAD). DIAN collects comprehensive information and tissue in accordance with standard protocols from asymptomatic and symptomatic ADAD mutation carriers and their non-carrier family members to determine the pathochronology of clinical, cognitive, neuroimaging, and fluid biomarkers of AD. This article describes the structure, implementation, and underlying principles of DIAN, as well as the demographic features of the initial DIAN cohort.

Yeast expressed foldable quadrivalent Aβ15 elicited strong immune response against Aβ without Aβ-specific T cell response in wild C57BL/6 mice

Active and passive immunizations with Aβ and Aβ antibodies successfully reduced AD pathology and improved cognitive functions in an AD mouse model. However, human clinical trials of vaccination with synthetic Aβ(AN1792), were halted due to brain inflammation, presumably induced by T cell-mediated immune response. In this study, we used Picha pastoris to produce a recombinant peptide vaccine, r4 × Aβ15(recombinant 4 × Aβ15), four tandem repeats of Aβ(1-15) interlinked by spacers . Wild-type mice were injected subcutaneously with CFA/IFA as adjuvant. r4 × Aβ15 vaccine elicited high titer anti-Aβ antibodies which bound to Aβ plaque in brain tissue from Tg2576 mouse. The antibody isotype was mainly IgG(1), indicating anti-inflammatory Th2 type. There was no splenocyte proliferation against Aβ peptide, which indicates that the r4 × Aβ15 vaccine does not induce Aβ-specific T cellular immune response. Thus, r4 × Aβ15 vaccine may be a safe and efficient vaccine for AD.

Active DNA Aβ42 vaccination as immunotherapy for Alzheimer disease

As a neurodegenerative disorder, Alzheimer disease (AD) is the most common form of dementia found in the aging population. Immunotherapy with passive or active immunizations targeting amyloid beta (Aβ) build-up in the brain may provide a possible treatment option and may help prevent AD from progressing. A number of passive immunizations with anti-Aβ42 antibodies are in different phases of clinical trials. One active immunization approach, AN-1792, was stopped after the development of autoimmune encephalitis in 6% of patients and a second one, CAD106, in which a small Aβ epitope is used, is currently in safety and tolerability studies. Besides active immunizations with proteins or peptides, active immunizations using DNA which codes for the protein against which the immune response will be directed, so called genetic immunizations, provide additional safety as the immune response in DNA immunizations differs quantitatively and qualitatively from the response elicited by peptide immunizations. In this review, we summarize our data using DNA Aβ42 immunizations in mouse models and discuss the results together with the results presented by other groups working on a DNA vaccine as treatment option for AD.

Immunization with a new DNA vaccine for Alzheimer's disease elicited Th2 immune response in BALB/c mice by in vivo electroporation

Immunization with synthetic amyloid β-protein (Aβ) peptide has resulted in preventing and clearing Aβ deposits as well as improving cognitive function in transgenic mouse models of Alzheimer's disease (AD). But similar immunization studies in humans were halted due to the risk of inducing T cell-mediated meningoencephalitis. A safe and effective vaccine for AD requires not only therapeutic levels of anti-Aβ antibodies but also the prevention of an adverse T cell-mediated, proinflammatory autoimmune response. In this study, we developed a DNA vaccine, p(Aβ(3-10))(10)-IL-4, encoding ten tandem repeats of Aβ(3-10) fused with mouse cytokine interleukin-4 (IL-4) as a molecular adjuvant. Wild-type mice were injected intramuscularly with p(Aβ(3-10))(10)-IL-4 followed by in vivo electroporation. The p(Aβ(3-10))(10)-IL-4 vaccine elicited high titer anti-Aβ antibodies which bound to Aβ plaque in brain tissue from a ten-month-old APP/PS1 transgenic mouse. The antibody isotype was mainly IgG(1) and the IgG(1)/IgG(2a) ratio in the p(Aβ(3-10))(10)-IL-4 group was approximately eight times greater than that of the Aβ(42) group. Ex vivo cultured splenocytes isolated from mice immunized with p(Aβ(3-10))(10)-IL-4 exhibited a low IFN-γ response and a high IL-4 response compared with the control group. These results indicate that immunization with the p(Aβ(3-10))(10)-IL-4 vaccine induced effective anti-Aβ antibodies and elicited a Th2-polarized immune response that had a lower potential to cause an inflammatory T cell response. Thus, the DNA vaccine, p(Aβ(3-10))(10)-IL-4, may be a safe and efficient vaccine for AD.

Application of immunosignatures to the assessment of Alzheimer's disease

OBJECTIVE

Accurate assessment of Alzheimer's disease (AD), both presymptomatically and at different disease stages, will become increasingly important with the expanding elderly population. There are a number of indications that the immune system is engaged in AD. Here we explore the ability of an antibody-profiling technology to characterize AD and screen for peptides that may be used for a simple diagnostic test.

METHODS

We developed an array-based system to profile the antibody repertoire of transgenic mice with cerebral amyloidosis (TG) and elderly individuals with or without AD. The array consists of 10,000 random sequence peptides (20-mers) capable of detecting antibody binding patterns, allowing the identification of peptides that mimic epitopes targeted by a donor's serum.

RESULTS

TG mice exhibited a distinct immunoprofile compared to nontransgenic littermates. Further, we show that dementia patients, including autopsy-confirmed AD subjects, have distinguishable profiles compared to age-matched nondemented people. Using antibodies to different forms of Aβ peptide and blocking protocols, we demonstrate that most of this signature is not due to the subject's antibodies raised against Aβ.

INTERPRETATION

We propose that "immunosignaturing" technology may have potential as a diagnostic tool in AD.

DNA immunization against amyloid beta 42 has high potential as safe therapy for Alzheimer's disease as it diminishes antigen-specific Th1 and Th17 cell proliferation

The pathogenesis of Alzheimer's disease (AD) has been strongly associated with the accumulation of amyloid beta (Aβ) peptides in brain, and immunotherapy targeting Aβ provides potential for AD prevention. A clinical trial in which AD patients were immunized with Aβ42 peptide was stopped when 6% of participants showed meningoencephalitis, apparently due to an inflammatory Th1 immune response. Previously, we and other have shown that Aβ42 DNA vaccination via gene gun generates a Th2 cellular immune response, which was shown by analyses of the respective antibody isotype profiles. We also determined that in vitro T cell proliferation in response to Aβ42 peptide re-stimulation was absent in DNA Aβ42 trimer-immunized mice when compared to Aβ42 peptide-immunized mice. To further characterize this observation prospectively and longitudinally, we analyzed the immune response in wild-type mice after vaccination with Aβ42 trimer DNA and Aβ42 peptide with Quil A adjuvant. Wild-type mice were immunized with short-term (1-3× vaccinations) or long-term (6× vacinations) immunization strategies. Antibody titers and isotype profiles of the Aβ42 specific antibodies, as well as cytokine profiles and cell proliferation studies from this longitudinal study were determined. Sufficient antibody titers to effectively reduce Aβ42, but an absent T cell proliferative response and no IFNγ or IL-17 secretion after Aβ42 DNA trimer immunization minimizes the risk of inflammatory activities of the immune system towards the self antigen Aβ42 in brain. Therefore, Aβ42 DNA trimer immunization has a high probability to be effective and safe to treat patients with early AD.

Analysis of three plasmid systems for use in DNA A beta 42 immunization as therapy for Alzheimer's disease

In an effort to optimize DNA immunization-elicited antibody production responses against A beta 1-42 (A beta 42) as a therapy for Alzheimer's disease (AD), comparisons were made between three distinct plasmid systems using gene gun delivery. Plasmids encoding A beta 42 monomer and a novel A beta 42 trimeric fusion protein were evaluated in conjunction with CMV or Gal4/UAS promoter elements. It was found that vaccination A beta 42 trimer under the Gal4/UAS promoter elicited high levels of anti-A beta 42 antibody production. Serum antibody levels from Gal4/UAS-A beta 42 trimer immunized mice were found to be 16.6+/-5.5 microg/ml compared to 6.5+/-2.5 microg/ml with Gal4/UAS-A beta 42 monomer or even less with CMV-A beta 42 trimer. As compared to monomeric A beta 42 or A beta 42 trimer expressed under the CMV promoter, injection of the Gal4/UAS-A beta 42 trimer induced high levels of A beta 42 antigen expression in tissue suggesting a mechanism for the increase in anti-A beta 42 antibody. Antibodies were found to be primarily IgG1 suggesting a predominant Th2 response (IgG1/IgG2a ratio of 9). Serum from A beta 42 trimer-vaccinated mice was also found to identify amyloid plaques in the brains of APP/PS1 transgenic mice. These results demonstrate the potential therapeutic use of Gal4/UAS DNA A beta 42 trimer immunization in preventing Alzheimer's disease.

Immunization with the SDPM1 peptide lowers amyloid plaque burden and improves cognitive function in the APPswePSEN1(A246E) transgenic mouse model of Alzheimer's disease

Vaccination has become an important therapeutic approach to the treatment of Alzheimer's disease (AD), however, immunization with Abeta amyloid can have unwanted, potentially lethal, side effects. Here we demonstrate an alternative peptide-mimotope vaccine strategy using the SDPM1 peptide. SDPM1 is a 20 amino acid peptide bounded by cysteines that binds tetramer forms of Abeta(1-40)- and Abeta(1-42)-amyloids and blocks subsequent Abeta amyloid aggregation. Immunization of mice with SDPM1 induced peptide-mimotope antibodies with the same biological activity as the SDPM1 peptide. When done prior to the onset of amyloid plaque formation, SDPM1 vaccination of APPswePSEN1(A246E) transgenic mice reduced amyloid plaque burden and Abeta(1-40) and Abeta(1-42) levels in the brain, improved cognitive performance in Morris water maze tests, and resulted in no increased T cell responses to immunogenic or Abeta peptides or brain inflammation. When done after plaque burden was already significant, SDPM1 immunization still significantly reduced amyloid plaque burden and Abeta(1-40/1-42) peptide levels in APPswePSEN1(A246E) brain without inducing encephalitogenic T cell responses or brain inflammation, but treatment at this stage did not improve cognitive function. These experiments demonstrate the efficacy of a novel vaccine approach for Alzheimer's disease where immunization with an Abeta(1-40/1-42) amyloid-specific binding and blocking peptide is used to inhibit the development of neuropathology and cognitive dysfunction.

DNA beta-amyloid(1-42) trimer immunization for Alzheimer disease in a wild-type mouse model

CONTEXT

DNA beta-amyloid(1-42) (Abeta42) trimer immunization was developed to produce specific T helper 2 cell (T(H)2)-type antibodies to provide an effective and safe therapy for Alzheimer disease (AD) by reducing elevated levels of Abeta42 peptide that occur in the brain of patients with AD.

OBJECTIVE

To compare the immune response in wild-type mice after immunization with DNA Abeta42 trimer and Abeta42 peptide.

DESIGN AND INTERVENTION

Wild-type mice received either 4 microg of DNA Abeta42 trimer immunization administered with gene gun (n = 8) or intraperitoneal injection of 100 microg of human Abeta42 peptide with the adjuvant Quil A (n = 8). Titers, epitope mapping, and isotypes of the Abeta42-specific antibodies were analyzed.

MAIN OUTCOME MEASURES

Antibody titers, mapping of binding sites (epitopes), isotype profiles of the Abeta42-specific antibodies, and T-cell activation.

RESULTS

DNA Abeta42 trimer immunization resulted in antibody titers with a mean of 15 microg per milliliter of plasma. The isotype profile of the antibodies differed markedly. A predominant IgG1 antibody response was found in the DNA-immunized mice, indicating a T(H)2 type of immune response (IgG1/IgG2a ratio of 10). The peptide-immunized mice showed a mixed T(H)1/T(H)2 immune response (IgG1/IgG2a ratio of 1) (P < .001). No increased T-cell proliferation was observed in the DNA-immunized mice (P = .03).

CONCLUSION

In this preliminary study in a wild-type mouse model, DNA Abeta42 trimer immunization protocol produced a T(H)2 immune response and appeared to have low potential to cause an inflammatory T-cell response.

Binding and uptake of A beta1-42 by primary human astrocytes in vitro

Clearance of the amyloid-beta peptide (A beta) as a remedy for Alzheimer's disease (AD) is a major target in on-going clinical trials. In vitro studies confirmed that A beta is taken up by rodent astrocytes, but knowledge on human astrocyte-mediated A beta clearance is sparse. Therefore, by means of flow cytometry and confocal laser scanning microscopy (CLSM), we evaluated the binding and internalization of A beta1-42 by primary human fetal astrocytes and adult astrocytes, isolated from nondemented subjects (n = 8) and AD subjects (n = 6). Furthermore, we analyzed whether alpha1-antichymotrypsin (ACT), which is found in amyloid plaques and can influence A beta fibrillogenesis, affects the A beta uptake by human astrocytes. Upon over night exposure of astrocytes to FAM-labeled A beta1-42 (10 microM) preparations, (80.7 +/- 17.7)% fetal and (52.9 +/- 20.9)% adult A beta-positive astrocytes (P = 0.018) were observed. No significant difference was found in A beta1-42 uptake between AD and non-AD astrocytes, and no influence of ApoE genotype on A beta1-42 uptake was observed in any group. There was no difference in the percentage of A beta-positive cells upon exposure to A beta1-42 (10 microM) combined with ACT (1,000:1, 100:1, and 10:1 molar ratio), versus A beta1-42 alone. CLSM revealed binding of A beta1-42 to the cellular surfaces and cellular internalization of smaller A beta1-42 fragments. Under these conditions, there was no increase in cellular release of the proinflammatory chemokine monocyte-chemoattractant protein 1, as compared with nontreated control astrocytes. Thus, primary human astrocytes derived from different sources can bind and internalize A beta1-42, and fetal astrocytes were more efficient in A beta1-42 uptake than adult astrocytes.

Neutralization of granulocyte macrophage colony-stimulating factor decreases amyloid beta 1-42 and suppresses microglial activity in a transgenic mouse model of Alzheimer's disease

The purpose of our study was to investigate microglia and astrocytes that are associated with human mutant amyloid precursor protein and amyloid beta (Abeta). We investigated whether the anti-granulocyte-macrophage-colony stimulating factor (GM-CSF) antibody can suppress microglial activity and decrease Abeta production in Alzheimer's disease transgenic mice (Tg2576 line). An antibody to mouse GM-CSF was introduced by intracerebroventricular (ICV) injections into the brains of 10-month-old Tg2576 male mice. We assessed the effect of several GM-CSF-associated cytokines on microglial activities and their association with Abeta using quantitative real-time RT-PCR, immunoblotting, immunohistochemistry analyses in anti-GM-CSF antibody-injected Tg2576 mice. Using sandwich ELISA technique, we measured intraneuronal Abeta in Tg2576 mice injected with GM-CSF antibody and PBS vehicle-injected control Tg2576 mice. Using double-labeling immunofluorescence analysis of intraneuronal Abeta, Abeta deposits and pro-inflammatory cytokines, we assessed the relationship between Abeta deposits and microglial markers in the Tg2576 mice, and also in the anti-GM-CSF antibody-injected Tg2576 mice. Our real-time RT-PCR analysis showed an increase in the mRNA expression of IL6, CD11c, IL1beta, CD40 and CD11b in the cerebral cortices of the Tg2576 mice compared with their littermate non-transgenic controls. Immunohistochemistry findings of microglial markers agreed with our real-time RT-PCR results. Interestingly, we found significantly decreased levels of activated microglia and Abeta deposits in anti-GM-CSF antibody-injected Tg2576 mice compared with PBS vehicle-injected Tg2576 mice. Findings from our real-time RT-PCR and immunoblotting analysis agreed with immunohistochemistry results. Our double-labeling analyses of intraneuronal Abeta and CD40 revealed that intraneuronal Abeta is associated with neuronal expression of CD40 in Tg2576 mice. Our quantitative sandwich ELISA analysis revealed decreased levels of soluble Abeta1-42 and increased levels of Abeta1-40 in Tg2576 mice injected with the anti-GM-CSF antibody, suggesting that anti-GM-CSF antibody alone decreases soluble Abeta1-42 production and suppresses microglial activity in Tg2576 mice. These findings indicating the ability of the anti-GM-CSF antibody to reduce Abeta1-42 and microglial activity in Tg2576 mice may have therapeutic implications for Alzheimer's disease.

Vaccination of Alzheimer's model mice with adenovirus vector containing quadrivalent foldable Abeta(1-15) reduces Abeta burden and behavioral impairment without Abeta-specific T cell response

Active amyloid beta (Abeta) vaccination has been shown to be effective in clearing cerebral Abeta and improving cognitive function in mouse models of Alzheimer's disease (AD). The meningoencephalitis observed in AD vaccination trial was likely related to excessive T cell-mediated immunity caused by the immunogen Abeta(1-42). To avoid this toxicity, previous researchers have been using synthetic truncated Abeta derivatives that promote humoral immunity. In this study, we develop a novel adenovirus vaccine, which can express quadrivalent foldable Abeta(1-15) (4 x Abeta(15)) and gene adjuvant GM-CSF in vivo. Importantly, the 4 x Abeta(15) sequence includes an Abeta-specific B cell epitope but lacks the reported T cell epitope. The 4 x Abeta(15) adenovirus vaccine induces an Abeta-specific IgG1 predominant humoral immune response, and reduces brain Abeta deposition and cognition deficits in Tg2576 mice. Detection of IL-4 and IFN-gamma in restimulated splenocytes shows a significant Th2-polarized immune response. Stimulation of splenocytes with 4 x Abeta(15) peptides results in robust proliferative responses, whereas proliferation is absent after stimulation with full-length Abeta, which indicates that the 4 x Abeta(15) adenovirus vaccine does not induce Abeta-specific T cellular immune response. Thus, our results raise the possibility that adenovirus vector encoding 4 x Abeta(15) would be a promising candidate for future AD vaccination program.