Abeta vaccine therapy for Alzheimer's disease]

In 1999, Schenk et al reported that vaccination of PDAPP-transgenic mice with synthetic Abeta42 in complete Freund's adjuvant showed markedly decrease of the amyloid burden in the brain. The second trial of vaccine, AN1792, for Alzheimer's patients was halted because of meningoencephalitis found in 6% of patients and one autopsy case was reported. Here, we comment the methods and the immunological mechanisms of Abeta vaccine therapy and discuss the pathological changes in the brain and side effects after AN1792 treatment. Furthermore, we present an oral Abeta vaccine therapy for Alzheimer's disease with the recombinant adeno-associated virus (AAV) vector that we developed.     

Microtubular reorganization and dendritic growth response in Alzheimer's disease

Cytoskeletal disruption is a key pathological feature of Alzheimer's disease (AD). We used refined immunocytochemical techniques to define the range of abnormalities affecting the microtubule system in AD hippocampus. Minimal tau and tubulin immunoreactivity was granular and accumulated in otherwise normal neuronal perikarya. As tau-reactive neurofibrillary tangles formed, granular tau and tubulin staining diminished, and ubiquitin reactivity developed. In regions of high neurofibrillary tangle density, microtubule-associated protein 2 (MAP2) histochemical features of remaining nontangled neurons included apical dendritic degeneration with proliferation of basal dendrites. In addition to perisomatic dendritic proliferation, there was massive sprouting of tau-immunoreactive distal dystrophic neurites. Sprouting proximal dendrites and dystrophic neurites often demonstrated growth-cone-like lamellipodia and filopodia. Degeneration of the perisomatic proliferating dendrites was characterized by the accumulation of fibrillar tau immunoreactivity. The colocalization of MAP2 and tau in growth structures recapitulated their codistribution in developing neurites. The data suggest that extensive plasticity and growth response occur in tandem with neuronal degeneration in AD, and that reorganization of the cytoskeletal microtubule system may underlie these proliferative changes.     

Alzheimer's disease as a polygenic disease

Recent advances in molecular genetics have enabled the identification of the causative genes for early-onset familial Alzheimer's disease (AD). However, sporadic and late-onset familial AD, the most common forms of AD, are considered to be polygenic disorders. The presence of APOE4, one of the specific alleles of the apolipoprotein E gene, has been established as a major genetic risk factor for the development of AD. Additional risk factors are under active investigation. Such new approaches are expected to establish preventive measures or treatments for AD.     

Cultured cells as a screen for novel treatments of Alzheimer's disease

Two easily measured abnormal properties of fibroblasts from patients with Alzheimer's disease have been utilized to develop an in vitro test system for screening novel therapeutic agents for Alzheimer's disease. The abnormal properties selected for study were increased isoproterenol-stimulated cyclic adenosine monophosphate production and decreased pH (measured by the weak-acid distribution method). L-Carnitine was tested as a potential therapeutic agent, since it has been used to treat a variety of experimental metabolic encephalopathies. The addition of L-carnitine normalized both of these properties in the Alzheimer cells. Tissue culture may aid as a preliminary screen for identifying novel approaches to the treatment of Alzheimer's disease.     

Selective ablation of bone marrow-derived dendritic cells increases amyloid plaques in a mouse Alzheimer's disease model

We have recently shown that the ability of microglia to effectively fight off aggregated beta-amyloid plaque formation and cognitive loss in transgenic mouse models of Alzheimer's disease (Tg-AD), is augmented in response to T-cell-based immunization, using glatiramer acetate (GA). The immunization increases incidence of local CD11c+ dendritic-like cells. It is unclear, however, whether these dendritic cells are derived from resident microglia or from the bone marrow. To determine the origin of this dendritic-cell population, we used chimeric mice whose bone marrow-derived cells express a transgene that allows the cells to be specifically ablated by diphtheria toxin. We show here that T-cell-based immunization of these mice, using GA, induced the recruitment of bone marrow-derived dendritic cells. Depletion of the dendritic cells by systemic injection of diphtheria toxin resulted in significantly increased formation of amyloid plaques. Thus, recruitment of bone marrow-derived dendritic cells evidently plays a role in reducing plaque formation in a mouse model of Alzheimer's disease.     

Transneuronally altered dendritic processing of tangle-free neurons in Alzheimer's disease

In Alzheimer's disease (AD), changes in dendritic morphology can be regarded as a result of an inherent disease-specific process associated with the formation of neurofibrillary tangles. Using three-dimensional morphometrical techniques and neuropatholologically staged tissue (Braak classification) of 32 cases, we demonstrate alterations in the dendritic length, branch order and number of segments of a tangle-free neuronal population in the AD-afflicted hippocampus, i.e. parvalbumin-containing cells of the fascia dentata. These alterations occurred primarily on the apical dendritic tree, the target of the entorhinal input. Mean of relative dendritic length, branch order and number of dendritic segments of apical dendrites decreased significantly, by 40-70% comparing stage V to stages 0 or I. In contrast, basal dendrites receiving no entorhinal input did not show significant changes. Entorhinal neurons projecting to the hippocampus are the first to be affected in AD and the first to die, resulting in hippocampal deafferentation. Therefore, this input-specific dendritic alteration of tangle-free neurons suggests that AD is confounded with a transneuronal component resulting from deafferentation. Experiments showed that deafferentation results in altered dendritic geometry causing an impaired signal integration. Thus, transneuronally altered dendritic signal integration might occur in neurons devoid of the major intraneuronal hallmark of AD, i.e. the neurofibrillary tangle.     

Immunotherapy as treatment for Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized pathologically by the deposition of beta-amyloid (A beta)-containing extracellular neuritic plaques, intracellular neurofibrillary tangles and neuronal loss. Much evidence supports the hypothesis that A beta peptide aggregation contributes to AD pathogenesis, however, currently approved therapeutic treatments do nothing to stop or reverse A beta deposition. The success of active and passive anti-A beta immunotherapies in both preventing and clearing parenchymal amyloid in transgenic mouse models led to the initiation of an active anti-A beta vaccination (AN1792) trial in human patients with mild-to-moderate AD, but was prematurely halted when 6% of inoculated patients developed aseptic meningoencephalitis. Autopsy results from the brains of four individuals treated with AN1792 revealed decreased plaque burden in select brain areas, as well as T-cell lymphocytes in three of the patients. Furthermore, antibody responders showed some improvement in memory task measures. These findings indicated that anti-A beta therapy might still be a viable option for the treatment of AD, if potentially harmful proinflammatory processes can be avoided. Over the past 6 years, this target has led to the development of novel experimental immunization strategies, including selective A beta epitope targeting, antibody and adjuvant modifications, as well as alternative routes and mechanisms of vaccine delivery, to generate anti-A beta antibodies that selectively target and remove specific A beta species without evoking autoimmunity. Results from the passive vaccination AD clinical trials that are currently underway will provide invaluable information about both the effectiveness of newly improved anti-A beta vaccines in clinical treatment, as well as the role of the A beta peptide in the pathogenesis of the disease.     

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.     

热诱导凋亡胶质瘤细胞致敏树突状细胞疫苗的制备与鉴定

目的 制备热诱导凋亡胶质瘤细胞致敏树突状细胞疫苗,探讨其增强树突状细胞抗原递呈、诱导细胞毒性T淋巴细胞产生更强肿瘤细胞杀伤作用的机制.方法 采用改良Inaba法,在重组小鼠粒细胞巨噬细胞集落刺激因子(rmGM-CSF)和重组小鼠白细胞介素-4(rmIL-4)作用下,体外诱导扩增小鼠骨髓来源的树突状细胞,电子显微镜和流式细胞术检测其生物学特征;分别以不同加热温度处理U251细胞,制备凋亡U251细胞致敏树突状细胞疫苗,3H-TdR掺入法和MTT法检测T淋巴细胞增殖能力和活化细胞毒性T淋巴细胞杀伤率.结果 在rmGM-CSF和rmIL-4作用下,小鼠骨髓来源细胞体外培养6～7 d即可诱导出树突状细胞,经倒置相差显微镜和电子显微镜证实细胞表面呈典型树突状结构;流式细胞术检测证实其表达特异性表面标记物CD11c,同时表达功能相关性抗原CD80、CD86和MHCⅡ.倒置相差显微镜和流式细胞术确定热诱导U251细胞凋亡的最佳条件为:44℃处理3 h再常规培养12 h,凋亡U251细胞可更好地负载树突状细胞,负载的树突状细胞可以激发T淋巴细胞增殖,诱导活化细胞毒性T淋巴细胞具有更强的杀伤肿瘤细胞的能力.结论 在rmGM-CSF和rmIL-4作用下,经体外成功制备的小鼠骨髓来源的树突状细胞,可热诱导凋亡胶质瘤细胞敏敏树突状细胞疫苗于体外有效激发T淋巴细胞增殖,诱导细胞毒性T淋巴细胞产生较强的杀伤肿瘤细胞能力.     

Down's dyndrome and Alzheimer's disease: dendritic spine counts in the hippocampus

Summary Samples of the hippocampus of four patients with Down's syndrome [two men aged 35 and 36 years with no evidence of Alzheimer's disease (AD) and two patients aged 47 and 55 years with associated AD] were obtained at post mortem and processed according to the rapid Golgi method. A significant reduction in the number of dendritic spines (DS) was found in the apical (middle, distal and oblique segments) and basilar (thick and thin segments) dendritic arbors of CA₁ and CA_2–3 pyramidal neurons in patients with Down's syndrome and no AD when compared to age-matched controls. An additional decrease of DS in every segment occurred in Down's patients with associated AD when compared to agematched controls and Down's patients with no AD. In Down's syndrome (either associated or not to AD) thin basilar dendrites were the most severely involved; in AD patients CA₁ pyramids were more severely affected than pyramidal neurons of the CA_2–3 subfield.     

Developing novel immunogens for an effective, safe Alzheimer's disease vaccine

Active amyloid beta (A beta) vaccination has been shown to be effective in clearing cerebral A beta and improving cognitive function in mouse models of Alzheimer's disease. However, an A beta vaccine clinical trial was suspended after meningoencephalitis was detected in a subset of subjects. Passive immunization has been suggested to be a safer alternative to active A beta immunization but there are reports of increased risk of microhemorrhages associated with its administration in aged beta-amyloid precursor protein transgenic mice bearing abundant vascular amyloid deposition. In addition, the cost may be prohibitive for large-scale clinical use. Therefore, we are designing novel A beta immunogens that encompass the B cell epitope of A beta but lack the T cell-reactive sites. These immunogens induced the production of A beta-specific antibodies in the absence of an A beta-specific cellular immune response in wild-type mice and are being tested in beta-amyloid precursor protein transgenic mice. These data together with published reports from several other groups suggest that a safe, active A beta vaccine is a tenable goal.     

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

BackgroundClinical 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.MethodsHumoral 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.ResultsAV-1955 generates long-term, potent anti-Aβ antibodies and cellular immune responses specific to foreign T-helper epitopes but not to self-Aβ.ConclusionsThis translational study demonstrates that a DNA-based epitope vaccine for AD could be appropriate for human clinical testing.     

Alzheimer's disease presenting as corticobasal syndrome.

A 60-year-old man presented with slowly progressive left hemi-Parkinsonism, left hand apraxia, myoclonus, dystonia, visuospatial disturbances, and alien limb phenomenon, resembling corticobasal syndrome. Eight years later, neuropathology revealed features of Alzheimer's disease, with asymmetrical (right more than left) cortical tau burden with image analysis. The videotaped clinical features, neuropsychological aspects, and neuropathological correlates are presented and discussed.     

Scales as outcome measures for Alzheimer's disease

The assessment of patient outcomes in clinical trials of new therapeutics for Alzheimer's disease (AD) continues to evolve. In addition to assessing drugs for symptomatic relief, an increasing number of trials are focusing on potential disease-modifying agents. Moreover, participants with AD are being studied earlier in their course of disease. As a result, the limitations of current outcome measures have become more apparent, as has the need for better instruments. In recognition of the need to review and possibly revise current assessment measures, the Alzheimer's Association, in cooperation with industry leaders and academic investigators, convened a Research Roundtable meeting devoted to scales as outcome measures for AD clinical trials. The meeting included a discussion of methodological issues in the use of scales in AD clinical trials, including cross-cultural issues. Specific topics related to the use of cognitive, functional, global, and neuropsychiatric scales were also presented. Speakers also addressed academic and industry initiatives for pooling data from untreated and placebo-treated patients in clinical trials. A number of regulatory topics were also discussed with agency representatives. Panel discussions highlighted areas of controversy, in an effort to gain consensus on various topics.     

Human IMR-32 neuroblastoma cells as a model cell line in Alzheimer's disease research

The present study investigated expression and processing of amyloid precursor protein by neuronally differentiated IMR-32 neuroblastoma cells. APP mRNA in these cells was found to consist of approximately 58% APP₆₉₅, 38% APP₇₅₁, and <4% APP₇₇₀. APP-immunoreactive bands detected in western blots of cellular protein extracts were only detected by anti-APP antibodies to peptides with strong homology to APLP2, suggesting that these bands represent APP-like proteins and not APP itself. This result suggests that previous studies claiming immunodetection of cellular forms of APP may have to be re-evaluated. Four main species of C-terminal truncated, secreted APP were detected in blots of protein extracts from medium conditioned by these cells. The immunoreactive profile of these bands suggested a cleavage site N-terminal to the Lys¹⁶-Leu¹⁷ bond of α-secretase. This, together with differences in number and molecular mass of APP-immunoreactive bands between secreted APP from IMR-32 cells and that from the commonly used PC-12 cells, suggests differences in APP processing between these two neuronally differentiated cell lines. In theory, IMR-32 cells being of human neuronal origin may be a more appropriate cell line to study APP-processing in relation to Alzheimer's disease than the rat phaeo-chromocytoma PC-12 cell line. Therefore, these detected differences warrant further investigation. Additionally IMR-32 cells under certain tissue culture conditions can form intracellular fibrillary material that reacts with anti-PHF specific antibodies. Neuronally differentiated IMR-32 cells could therefore be used as a model system to investigate possible interactions between APP-processing and PHF formation. © 1994 Wiley-Liss, Inc.