Faculty Bibliography

ABSTRACT: BACKGROUND: Alzheimer's Disease (AD) is the most common of the conformational neurodegenerative disorders characterized by the conversion of a normal biological protein into a beta-sheet-rich pathological isoform. In AD the normal soluble Abeta (sAbeta) forms oligomers and fibrils which assemble into neuritic plaques. The most toxic form of Abeta is thought to be oligomeric. A recent study reveals the cellular prion protein, PrPC, to be a receptor for Abeta oligomers. Abeta oligomers suppress LTP signal in murine hippocampal slices but activity remains when pretreated with the PrP monoclonal anti-PrP antibody, 6D11. We hypothesized that targeting of PrPC to prevent Abeta oligomer-related cognitive deficits is a potentially novel therapeutic approach. APP/PS1 transgenic mice aged 8 months were intraperitoneally (i.p.) injected with 1 mg 6D11 for 5 days/week for 2 weeks. Two wild-type control groups were given either the same 6D11 injections or vehicle solution. Additional groups of APP/PS1 transgenic mice were given either i.p. injections of vehicle solution or the same dose of mouse IgG over the same period. The mice were then subjected to cognitive behavioral testing using a radial arm maze, over a period of 10 days. At the conclusion of behavioral testing, animals were sacrificed and brain tissue was analyzed biochemically or immunohistochemically for the levels of amyloid plaques, PrPC, synaptophysin, Abeta40/42 and Abeta oligomers. RESULTS: Behavioral testing showed a marked decrease in errors in 6D11 treated APP/PS1 Tg mice compared with the non-6D11 treated Tg groups (p < 0.0001). 6D11 treated APP/PS1 Tg mice behaved the same as wild-type controls indicating a recovery in cognitive learning, even after this short term 6D11 treatment. Brain tissue analysis from both treated and vehicle treated APP/PS1 groups indicate no significant differences in amyloid plaque burden, Abeta40/42, PrPC or Abeta oligomer levels. 6D11 treated APP/PS1 Tg mice had significantly greater synaptophysin immunoreactivity in the dentate gyrus molecular layer of the hippocampus compared to vehicle treated APP/PS1 Tg mice (p < 0.05). CONCLUSIONS: Even short term treatment with monoclonal antibodies such as 6D11 or other compounds which block the binding of Abeta oligomers to PrPC can be used to treat cognitive deficits in aged AD transgenic mice

Many neurodegenerative diseases are characterized by the conformational change of normal self-proteins into amyloidogenic, pathological conformers, which share structural properties such as high beta-sheet content and resistance to degradation. The most common is Alzheimer's disease (AD) where the normal soluble amyloid beta (sAbeta) peptide is converted into highly toxic oligomeric Abeta and fibrillar Abeta that deposits as neuritic plaques and congophilic angiopathy. Currently, there is no highly effective treatment for AD, but immunotherapy is emerging as a potential disease modifying intervention. A major problem with most active and passive immunization approaches for AD is that both the normal sAbeta and pathogenic forms are equally targeted with the potential of autoimmune inflammation. In order to avoid this pitfall, we have developed a novel immunomodulatory method that specifically targets the pathological conformations, by immunizing with polymerized British amyloidosis (pABri) related peptide which has no sequence homology to Abeta or other human proteins. We show that the pABri peptide through conformational mimicry induces a humoral immune response not only to the toxic Abeta in APP/PS1 AD transgenic mice but also to paired helical filaments as shown on AD human tissue samples. Treated APP/PS1 mice had a cognitive benefit compared to controls (p<0.0001), associated with a reduction in the amyloid burden (p = 0.0001) and Abeta40/42 levels, as well as reduced Abeta oligomer levels. This type of immunomodulation has the potential to be a universal beta-sheet disrupter, which could be useful for the prevention or treatment of a wide range of neurodegenerative diseases

Prion diseases are a unique category of illness, affecting both animals and humans, where the underlying pathogenesis is related to a conformational change of a normal self protein called cellular prion protein to a pathological and infectious conformer known as scrapie prion protein (PrP(Sc)). Currently, all prion diseases lack effective treatment and are universally fatal. Past experiences with bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease mainly in Europe, as well as the current epidemic of chronic wasting disease in North America, have highlighted the need to develop prophylactic and/or therapeutic approaches. In Alzheimer's disease that, like prion disease, is a conformational neurodegenerative disorder, both passive and active immunization has been shown to be highly effective in model animals at preventing disease and cognitive deficits, with emerging data from human trials suggesting that this approach is able to reduce amyloid-related pathology. However, any immunomodulatory approach aimed at a self-antigen has to finely balance an effective humoral immune response with potential autoimmune toxicity. The prion diseases most commonly acquired by infection typically have the alimentary tract as a portal of infectious agent entry. This makes mucosal immunization a potentially attractive method to produce a local immune response that partially or completely prevents prion entry across the gut barrier, while at the same time producing modulated systemic immunity that is unlikely to be associated with toxicity. Our results using an attenuated Salmonella vaccine strain expressing the prion protein showed that mucosal vaccination can protect against prion infection from a peripheral source, suggesting the feasibility of this approach. It is also possible to develop active and/or passive immunomodulatory approaches that more specifically target PrP(Sc) or target the shared pathological conformer found in numerous conformational disorders. Such approaches could have a significant impact on many of the common age-associated dementias

Background: PS1 mutations may increase Abeta production but their effect on tau expressionphosphorylation and/or aggregation has not been thoroughly assessed.We have previously shown that the M146L mutation does not lead to tau pathology in mice expressing one isoform of wild-type human tau (ON3R) but it does promote tau phosphorylation and aggregation inmice expressing all six isoforms of wild-type human tau on a mouse tau knock-out background (htau/PS1/mtau-/-). Methods: We have now analyzed further this accelerated pathologyand its time-dependence compared to htau/mtau-/- littermatesand are studying the possible pathways involved in this important interaction. The mice were killed at 2-35-6 and 8-9 months for brain analyses. Results: Pathological tau was observed on brain sections in the htau/PS1/mtau-/- mice but not in controls as early as at 2 months of ageit increased with ageand was routinely positive with Thioflavin S and occasionally with Gallyas silver stain. Total tau levels did not differ between the groups at any age but human tau CP27 bands shifted to a higher MW (hyperphosphorylation) in the new model compared to controls. Also, in those animals PHF1 IR soluble tau was increased by 142% and 219% compared to their htau/mtau-/- littermates at 5-6 months (p<0.02) and 8-9 months (p<0.002), respectively. Likewise, IHC analysis revealed an 83% increase in PHF1 IR tau in the pyriform cortex at 8-9 months, (p=0.02), and a comparable increase at 5-6 months and in AT8 IR (IHC and Western) that are being quantitated. Importantly, the htau/PS1/mtau-/- mice were more cognitively impaired than controls in the Radial Arm Maze (p<0.03). Analyses of other cortical and hippocampal regions with advanced tau pathology, with other tau antibodies as well as of insoluble tau is underway. Further-more, older animals, tau-related pathology and the potential involvement of various signaling pathways are being assessed. Conclusions: The M146L mutation promotes age-related tau phosphorylation and aggregation, and impairs cognition compared to controls, suggesting that PS1/tau interaction may be important in the etiology and/or pathogenesis of AD. This novel model can be very useful for studying the onset and progression of AD as well as for therapeutic studies

Background: Manipulation of the immune system is becoming a promising treatment approach for Alzheimer's disease (AD). However, when this approach was tried in humans, in contrast to results in AD animal models, encephalitis emerged as a significant form of toxicity in some patients. Vaccination studies have so far mainly targeted the adaptive immune system. Our research group postulated stimulation of the innate immune system as possible alternative method for ameliorating AD related pathology, without associated toxicity. Our prior work in prion disease, suggested that this could be done effectively via Toll-like receptor 9 (TLR9). Objective: To assess the utility of TLR 9 agonist CpG ODN to stimulate the innate immune system and prevent AD pathology in a mouse model. Methods: Female Tg2576 mice were injected with either the TLR9 agonist type B CpG oligodeoxynucleotide 1826 or vehicle beginning at 6 weeks of age, and once a month thereafter for a total of 14 injections. Controls were non-transgenic C57BL/6 x SJL mice injected with vehicle on the same schedule. At the age of sixteen months, the mice were subjected to behav-ioral testing. Results: No difference between Tg groups was found in any of the locomotor parameters. CpG treatment led to working memory improvement in APP Tg2576 mice as indicated by radial arm maze testing (two-way ANOVA p = 0.019, post-hoc Tg-CpG vs Tg-vehicle, p = 0.026). In evaluating the efficacy of CpG ODN peripheral administration in AD mice, we found that stimulation of TLR9 signaling led to 66%(p = 0.0001) reduction in cortical and 59% (p = 0.002) reduction in hippocampal amyloid burden compared to vehicle treated Tg animals. This re-markable reduction of amyloid burden was paralleled by a reduction in the numbers of activated microglia and astrocytes. When analyzed sepa-rately, we observed a significant decrease in vascular amyloid burden with-out any evidence of increased cerebral microhemmorhages. Furthermore, treatment with CpG ODN was highly effective at reducing the brain Abeta levels along with Abeta oligomers. Conclusions: These results validate the feasibility of TLR9 ligand CpG ODN currently in clinical trials for a variety of other diseases as a new highly effective agent for the prevention and/or treatment of AD

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

OBJECTIVES:: Magnetic resonance (MRI) studies rely on sulcal boundaries to delineate the human entorhinal cortex (EC) and typically show that EC size is reduced in Alzheimer's disease (AD) and a predictor of future dementia. However, it is unknown if variations in the EC sulcal patterns are associated with AD. We classified the lateral EC sulcal boundary as either a rhinal or collateral pattern and tested the hypotheses that the rhinal pattern was (1) more common in AD and (2) associated with a smaller EC size. EXPERIMENTAL DESIGN:: MRI was used to determine the prevalence of the rhinal and collateral EC patterns in 421 subjects (212 AD, 107 old normal (ONL), and 102 young NL (YNL). Anatomical validation studies of normal subjects were conducted at postmortem in 34 brain hemispheres and in vivo with 21 MRI volume studies. EC pattern reliability was studied with MRI in both cross-sectional and longitudinal designs. PRINCIPAL OBSERVATIONS:: The rhinal pattern was more frequent in the right hemisphere in AD (47%) compared with ONL (28%, odds ratio = 2.25, P = 0.001). EC pattern was not related to ApoE genotype. The validations showed that the EC sulcal pattern was not associated with the neuronal number, surface area, or volume of the EC. In patients with antemortem MRI studied at postmortem it was equivalently determined, that EC patterns are reliably determined on MRI and do not change with the progressive atrophy of AD. CONCLUSIONS:: The data indicate that the right hemisphere rhinal pattern is over represented in AD as compared with control. However, in normal subjects the EC rhinal pattern is not associated with a diminished EC tissue size. It remains to be demonstrated if the right EC rhinal sulcus pattern association with AD reflects genetic or developmental influences. Hum Brain Mapp, 2008. (c) 2008 Wiley-Liss, Inc

PURPOSE: We report the first clinicopathological series of longitudinal FDG-PET scans in post-mortem (PM) verified cognitively normal elderly (NL) followed to the onset of Alzheimer's-type dementia (DAT), and in patients with mild DAT with progressive cognitive deterioration. METHODS: Four NL subjects and three patients with mild DAT received longitudinal clinical, neuropsychological and dynamic FDG-PET examinations with arterial input functions. NL subjects were followed for 13 +/- 5 years, received FDG-PET examinations over 7 +/- 2 years, and autopsy 6 +/- 3 years after the last FDG-PET. Two NL declined to mild cognitive impairment (MCI), and two developed probable DAT before death. DAT patients were followed for 9 +/- 3 years, received FDG-PET examinations over 3 +/- 2 years, and autopsy 7 +/- 1 years after the last FDG-PET. Two DAT patients progressed to moderate-to-severe dementia and one developed vascular dementia. RESULTS: The two NL subjects who declined to DAT received a PM diagnosis of definite AD. Their FDG-PET scans indicated a progression of deficits in the cerebral metabolic rate for glucose (CMRglc) from the hippocampus to the parietotemporal and posterior cingulate cortices. One DAT patient showed AD with diffuse Lewy body disease (LBD) at PM, and her last in vivo PET was indicative of possible LBD for the presence of occipital as well as parietotemporal hypometabolism. CONCLUSION: Progressive CMRglc reductions on FDG-PET occur years in advance of clinical DAT symptoms in patients with pathologically verified disease. The FDG-PET profiles in life were consistent with the PM diagnosis