Faculty Bibliography

Background: Active anti-amyloid immunotherapy is a strategy developed againstAlzheimer's disease.ApproacheswithAs1-42 orK6As1-30 immunogens in an adjuvant decrease amyloid-s burden and prevent cognitive decline in transgenic mice (Asuni et al, 2006). However, clinical trials of As1-42 immunotherapy have induced side effects like encephalitis and possibly microhemorrhages (Orgogozo et al, 2003; Ferrer et al, 2004). Mouse lemurs can develop As plaques with age (Mestre-Frances et al, 2000). Such a primate modelmay be more predictive than rodents of human side effects.We studied, by magnetic resonance imaging (MRI), immunotherapies in these primates. Methods: A first cohort was used to compare K6As1-30 (n = 4; 5.8 6 0.2years) and As1-42 (n = 4; 5.96 0.2years) immunogens in alumadjuvant. Asecond cohortwas used to evaluate K6As1-30 (n=6; 4.660.2years) compared to adjuvant alone (n = 6; 4.7 6 0.3years). All the animals were followed- up by MRI (7T PharmaScan-Bruker) to evaluate neuroinflammation, microhemorrhages and other forms of iron deposition, with T2-weighted and T2*-weighted sequences (resolution = (234x234x234)Amm3). The hypointense regions from T2*-weighted images were quantified and evaluate by histology. A complementary study of age effect was performed with twenty other naive animals (1.5 to 4.9years). Results: TheT2-weighted images did not show any neuroinflammation during immunization, irrespective of the immunogen. Microhemorrhages were detected in the cerebral parenchyma at the histological analysis of the first cohort. The animals treated with K6As1-30 presented less microhemorrhages compared to those treated with As1-42 vaccine (Mann-Whitney, p < 0.05). These small microhemorrhages were not detected on the T2*-weighted images. However hypointense signal was detected onMRI and corresponded to iron deposits in the choroid plexus. Its volume increased with natural aging (r=0.60; p<0.001) and with As1-42 compared toK6As1-30 treatment (ANOVA, p<0.05).No difference was detected between K6As1-30 and adjuvant alone. Conclusions: The immunotherapies studied in the mouse lemur primate did not lead to any MRI sign of neuroinflammation. The K6As1-30 strategy appears to be safer than the As1-42 strategy as it provokes less microhemorrhages in the cerebral parenchyma and less iron deposits in the choroid plexus

Background: Active anti-amyloid immunotherapy is a strategy developed against Alzheimer's disease.ApproacheswithAs1-42 orK6As1-30 immunogens in an adjuvant decrease amyloid-s burden and prevent cognitive decline in transgenic mice (Asuni et al, 2006). However, clinical trials of As1-42 immunotherapy have induced side effects like encephalitis and possibly microhemorrhages (Orgogozo et al, 2003; Ferrer et al, 2004). Mouse lemurs can develop As plaques with age (Mestre-Frances et al, 2000). Such a primate modelmay bemore predictive than rodents of human side effects.We studied, by magnetic resonance imaging (MRI), immunotherapies in these primates. Methods: A first cohort was used to compare K6As1-30 (n = 4; 5.8 +/- 0.2 years) and As1-42 (n = 4; 5.9 +/- 0.2 years) immunogens in alum adjuvant. Asecond cohortwas used to evaluateK6As1-30 (n=6; 4.660.2 years) compared to adjuvant alone (n = 6; 4.7 +/- 0.3 years). All the animals were followed- up by MRI (7T PharmaScan-Bruker) to evaluate neuroinflammation, microhemorrhages and other forms of iron deposition, with T2-weighted and T2*-weighted sequences (resolution=(234x234x234)mm³). The hypointense regions from T2*-weighted images were quantified and evaluate by histology. A complementary study of age effectwas performedwith twenty other naive animals (1.5 to 4.9 years). Results: The T2-weighted images did not show any neuroinflammation during immunization, irrespective of the immunogen. Microhemorrhages were detected in the cerebral parenchyma at the histological analysis of the first cohort. The animals treated with K6As1-30 presented less microhemorrhages compared to those treated with As1-42 vaccine (Mann-Whitney, p < 0.05). These small microhemorrhages were not detected on the T2*-weighted images. However hypointense signalwas detected on MRI and corresponded to iron deposits in the choroid plexus. Its volume increasedwith natural aging (r= 0.60; p< 0.001) and withAs1-42 compared to K6As1-30 treatment (ANOVA, p < 0.05). No difference was detected between K6As1-30 and adjuvant alone. Conclusions: The immunotherapies studied in the mouse lemur primate did not lead to any MRI sign of neuroinflammation. The K6As1-30 strategy appears to be safer than theAs1-42 strategy as it provokes less microhemorrhages in the cerebral parenchyma and less iron deposits in the choroid plexus

Harnessing the immune system to clear protein aggregates is emerging as a promising approach to treat various neurodegenerative diseases. In Alzheimer's disease (AD), several clinical trials are ongoing using active and passive immunotherapy targeting the amyloid-beta (Abeta) peptide. Limited emphasis has been put into clearing tau/tangle pathology, another major hallmark of the disease. Recent findings from the first Abeta vaccination trial suggest that this approach has limited effect on tau pathology and that Abeta plaque clearance may not halt or slow the progression of dementia in individuals with mild-to-moderate AD. To assess within a reasonable timeframe whether targeting tau pathology with immunotherapy could prevent cognitive decline, we developed a new model with accelerated tangle development. It was generated by crossing available strains that express all six human tau isoforms and the M146L presenilin mutation. Here, we show that this unique approach completely prevents severe cognitive impairment in three different tests. This remarkable effect correlated well with extensive clearance of abnormal tau within the brain. Overall, our findings indicate that immunotherapy targeting pathological tau is very feasible for tauopathies, and should be assessed in clinical trials in the near future

Alzheimer's disease (AD) is one of the categories of neurodegenerative diseases characterized by a conformational change of a normal protein into a pathological conformer with a high beta-sheet content that renders it resistant to degradation and neurotoxic. In AD, the normal soluble amyloid beta (sAbeta) peptide is converted into oligomeric/fibrillar Abeta. The oligomeric forms of Abeta are thought to be the most toxic, while fibrillar Abeta becomes deposited as amyloid plaques and congophilic angiopathy, which both serve as neuropathological markers of the disease. An additional important feature of AD is the accumulation of abnormally phosphorylated tau as soluble toxic oligomers and as neurofibrillary tangles. Many therapeutic interventions are under investigation to prevent and treat AD. The testing of these diverse approaches to ameliorate AD pathology has been made possible by the existence of numerous transgenic mouse models which each mirror specific aspects of AD pathology. None of the current murine models is a perfect match of the human disease. Perhaps the most exciting of the therapeutic approaches being developed is immunomodulation targeting the aggregating proteins, Abeta and tau. This type of AD therapy is currently being assessed in many transgenic mouse models, and promising findings have led to clinical trials. However, there is a discrepancy between results in murine models and ongoing clinical trials, which highlight the limitations of these models and also of our understanding of the underlying etiology and pathogenesis of AD. Because of these uncertainties, Tg models for AD are continuously being refined with the aim to better understand the disease and to enhance the predictive validity of potential treatments such as immunotherapies

Immunotherapies targeting the amyloid-beta (Abeta) peptide in Alzheimer's disease (AD) have consistently been effective in mouse studies and shown promise in clinical trials, although some setbacks have occurred. First, encephalitis was observed in a small subset of patients. More recent autopsy data from a few subjects suggests that clearance of Abeta plaques may not halt cognitive deterioration once impairments are evident, emphasizing the need for other more effective approaches at that stage of the disease. Another important target in AD is the neurofibrillary tangles and its precursors, composed primarily of hyperphosphorylated tau proteins, which correlate well with the degree of dementia. As Abeta and tau pathologies are likely synergistic, targeting both together may be more effective, and perhaps essential as early diagnosis prior to cognitive decline is currently unavailable. Also, Abeta immunotherapy results in a very limited indirect clearance of tau aggregates, showing the importance of developing a separate therapy that directly targets pathological tau. Our findings in two tangle mouse models indicate that active immunization targeting an AD phospho-tau epitope reduces aggregated tau in the brain and prevents/slows progression of the tangle-related behavioral phenotype, including cognitive impairment. These antibodies enter the brain and bind to pathological tau within neurons although the therapeutic effect may at least in part be due to clearance of extracellular tau that may have biological effects. We are currently clarifying the mechanism of these promising findings, determining its epitope specificity as well as assessing the feasibility of this approach for clinical trials

Background: Immunotherapy holds great promise for Alzheimer's disease (AD) and other conformational disorders. Recent studies from our group have shown that immunization with an AD specific phosphotau immuno-gen Tau379-408[P-Ser396,404] could alleviate brain levels of aggregated tau and slow the progression of motor deficits or prevent cognitive impair-ments in two different tangle models (Asuni A. et al. J. Neurosci., 2007, Sigurdsson E.M. et al., ICAD Chicago, 2008). To assess potential epitope specificity and safety of this promising therapeutic effect, we are examining several tau epitopes. Here we assessed the efficacy of targeting a region within the microtubule binding site. Methods: Homozygous P301L mice were immunized with Tau260-264[P-Ser262] linked to a tetanus toxin helper T-cell epitope in alum adjuvant (n=8) or with adjuvant only (n=7), starting at 2 months. Mice were tested on various sensorimotor tasks (rotarod, traverse beam, locomotor activity) at 5 and 8 months of age. An-tibody titers were determined and at 8 months their brains were processed for tau biochemistry and histology. Results: The vaccine elicited a robust antibody response that was associated with a 64% reduction in PHF-1 tau staining (p=0.02) in the dentate gyrus of the right hemisphere but soluble PHF-1 tau levels were unaltered in the whole left hemisphere compared to controls. Analysis of other brain regions, of insoluble tau and with other tau antibodies is underway. The clearance of tau aggregates was accompanied with functional benefits as the control animals deteriorated in their performance on the rotarod (p=0.05) and the traverse beam (p=0.03) from 5 to 8 months of age, whereas the immunized mice performed equally well at both time points. Various locomotor activity measurements did not differ between the groups except that the 8 month old controls obtained a higher maximum velocity in the open field than treated littermates (p<0.01). Con clusions: Together with our previous results, these findings indicate that immunological targeting of various tau epitopes is a potential therapy for AD. However, a direct comparison of these different immunogens will be needed to assess their relative efficacy. Supported by: NIH grant AG032611, the Alzheimer's Drug Discovery Foundation and the Alzheimer's Association

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