Faculty Bibliography

We have been developing Abeta derivative vaccines with the objective to improve the safety of Abeta targeting immunotherapy. Our Abeta homologs are designed to have less direct toxicity and to produce a modified immune response compared to Abeta. In extensive mouse studies, all our vaccines have improved cognition in transgenic mice while eliciting different immune responses and reducing brain amyloid burden to a variable degree. While we are continuing to characterize these vaccines in mice, in preparation for studies in old primates and for human trials we assessed their effect in young lemur primates (n=25) that with age develop Abeta plaques and tau aggregates as seen in Alzheimer's disease. In the primates, all the peptides administered with alum adjuvant elicited a moderate to robust anti-Abeta IgM response. Abeta1-42, K6Abeta1-30 and K6Abeta1-30[E(18)E(19)] resulted in a high anti-Abeta IgG response, whereas Abeta1-30[E(18)E(19)] produced a weaker more variable IgG titer. Notably, 22 weeks after the 3rd immunization, IgM and IgG levels in derivative-vaccinated primates were similar to preimmune values whereas Abeta1-42 treated primates maintained a moderate IgG titer. The increase in antibodies that recognized Abeta1-40 often correlated with increase in Abeta1-40 in plasma, which suggests that the antibodies were binding to Abeta in vivo. Interestingly, significant transient weight gain was observed (K6Abeta1-30-, Abeta1-30[E(18)E(19)]- and Abeta1-42-treated) or a trend in the same direction (K6Abeta1-30[E(18)E(19)]-treated, adjuvant controls) following the injections. Based on these findings, we have chosen K6Abeta1-30 for immunizations in old primates as the antibody response to this vaccine was less variable compared to other Abeta derivatives. Our present findings indicate that most of our Abeta derivatives elicit a substantial antibody response in primates, and importantly this effect is reversible which enhances the safety profile of our approach

Immunotherapy holds great promise for Alzheimer's disease (AD) and other conformational disorders but certain adverse reactions need to be overcome. Prior to the side effects in the first Elan/Wyeth AD vaccine trial, we proposed using amyloid-beta (Abeta) derivatives as a safer approach. The route of administration may also affect vaccine safety. To assess the feasibility of oral immunization that promotes mucosal immunity, Tg2576 AD model mice were treated prophylactically three times over 6 weeks starting at 3-5 months of age with a Salmonella vaccine expressing K6Abeta<formula> _{1-30}</formula>. At 22-24 months of age, cortical Abeta plaque burden and total Abeta<formula>_{40}</formula>/<formula>_{42}</formula> levels were reduced by 48-75% in the immunized mice compared to controls, which received unmodified Salmonella. Plaque clearance was not associated with increased microglial activation which may be explained by the long treatment period. Furthermore, cerebral microhemorrhages were not increased in the treated mice in contrast to several passive Abeta antibody studies. These results further support our findings with this immunogen delivered subcutaneously and demonstrate its efficacy when given orally which may provide added benefits for human use

The present invention relates to immunogenic but non-depositing-forming polypeptides or peptides homologous to amyloid beta, prion, amylin or alpha-synuclein which can be used alone or conjugated to an immunostimulatory molecule in an immunizing composition for inducing an immune response to amyloid beta peptides and amyloid deposits, to prion protein and prion deposits, to amylin and amylin deposits, to alpha-synuclein and deposits containing alpha-synuclein, or to polyglutamine repeats and deposits of proteins containing polyglutamine repeats. Described are also antibodies directed against such peptides, their generation, and their use in methods of passive immunization to such peptides and deposits

Immunotherapies that target the amyloid-beta (Abeta) peptide in Alzheimer's disease (AD) have shown promise in animal and human studies. Although the first clinical trial was halted because of adverse reactions, this approach has been refined and additional trials are underway. Another important target in AD is the neurofibrillary tangles, composed primarily of hyperphosphorylated tau proteins, which correlate well with the degree of dementia. As Abeta and tau pathologies are likely synergistic, targeting both should be more effective and may be essential as early diagnosis prior to cognitive decline is currently not available. Also, Abeta immunotherapy only results in a very limited indirect clearance of tau aggregates in dystrophic neurites, showing the importance of developing a separate therapy that directly targets pathological tau. Our findings in two tangle mouse models indicate that immunization with a phospho-tau derivative reduces aggregated tau in the brain and slows progression of the tangle-related behavioral phenotype. These antibodies enter the brain and bind to pathological tau within neurons. We are currently clarifying further the mechanism of action of this promising therapeutic approach and determining its epitope specificity

Memantine, an N-methyl-D-aspartate (NMDA) receptor antagonist, has been shown to improve learning and memory in several preclinical models of Alzheimer's disease (AD). Memantine has also been shown to reduce the levels of amyloid beta (Abeta) peptides in human neuroblastoma cells as well as to inhibit Abeta oligomer-induced synaptic loss. In this study, we assessed whether NMDA receptor inhibition by memantine in transgenic mice expressing human amyloid-beta precursor protein (APP) and presenilin 1 (PS1) is associated with cognitive benefit and amyloid burden reduction by using object recognition, micromagnetic resonance imaging (muMRI), and histology. APP/PS1 Tg mice were treated either with memantine or with vehicle for a period of 4 months starting at 3 months of age. After treatment, the mice were subjected to an object recognition test and analyzed by ex vivo muMRI, and histological examination of amyloid burden. muMRI was performed following injection with gadolinium-DTPA-Abeta(1-40). We found that memantine-treated Tg mice performed the same as wild-type control mice, whereas the performance of vehicle-treated Tg mice was significantly impaired (P = 0.0081, one-way ANOVA). Compared with vehicle-treated animals, memantine-treated Tg mice had a reduced plaque burden, as determined both histologically and by muMRI. This reduction in amyloid burden correlates with an improvement in cognitive performance. Thus, our findings provide further evidence of the potential role of NMDA receptor antagonists in ameliorating AD-related pathology. In addition, our study shows, for the first time, the utility of muMRI in conjunction with gadolinium-labeled Abeta labeling agents to monitor the therapeutic response to amyloid-reducing agents. (c) 2008 Wiley-Liss, Inc

Amyloid plaques are a characteristic feature in Alzheimer's disease (AD). A novel non-toxic contrast agent is presented, Gd-DTPA-K6Abeta1-30, which is homologous to Abeta, and allows plaque detection in vivo. muMRI was performed on AD model mice and controls prior to and following intracarotid injection with Gd-DTPA-K6Abeta1-30 in mannitol solution, to transiently open the blood-brain barrier. A gradient echo T2(*)-weighted sequence was used to provide 100mum isotropic resolution with imaging times of 115min. The scans were examined with voxel-based analysis (VBA) using statistical parametric mapping, for un-biased quantitative comparison of ligand-injected mice and controls. The results indicate that: (1) Gd-DTPA-K6Abeta1-30 is an effective, non-toxic, ligand for plaque detection when combined with VBA (p</=0.01-0.001), comparing pre and post-ligand injection scans. (2) Large plaques can be detected without the use of a contrast agent and this detection co-localizes with iron deposition. (3) Smaller, earlier plaques require contrast ligand for MRI visualization. Our ligand when combined with VBA may be useful for following therapeutic approaches targeting amyloid in transgenic mouse models

Significant outbreaks of prion disease linked to oral exposure of the prion agent have occurred in animal and human populations. These disorders are associated with a conformational change of a normal protein, PrP(C) (C for cellular), to a toxic and infectious form, PrP(Sc) (Sc for scrapie). None of the prionoses currently have an effective treatment. Some forms of prion disease are thought to be spread by oral ingestion of PrP(Sc), such as chronic wasting disease and variant Creutzfeldt-Jakob disease. Attempts to obtain an active immunization in wild-type animals have been hampered by auto-tolerance to PrP and potential toxicity. Previously, we demonstrated that it is possible to overcome tolerance and obtain a specific anti-PrP antibody response by oral inoculation of the PrP protein expressed in an attenuated Salmonella vector. This past study showed that 30% of vaccinated animals were free of disease more than 350 days post-challenge. In the current study we have both optimized the vaccination protocol and divided the vaccinated mice into low and high immune responder groups prior to oral challenge with PrP(Sc) scrapie strain 139A. These methodological refinements led to a significantly improved therapeutic response. 100% of mice with a high mucosal anti-PrP titer immunoglobulin (Ig) A and a high systemic IgG titer, prior to challenge, remained without symptoms of PrP infection at 400 days (log-rank test P<0.0001 versus sham controls). The brains from these surviving clinically asymptomatic mice were free of PrP(Sc) infection by Western blot and histological examination. These promising findings suggest that effective mucosal vaccination is a feasible and useful method for overcoming tolerance to PrP and preventing prion infection via an oral route