Faculty Bibliography

Alzheimer's disease is the most common cause of dementia worldwide. Alzheimer's disease is a member of a broad range of neurodegenerative diseases characterized pathologically by the conformational change of a normal protein into a pathological conformer with a high beta-sheet content that renders it neurotoxic. In the case of Alzheimer's disease, the normal soluble amyloid beta peptide is converted into oligomeric/fibrillar amyloid beta. The oligomeric forms of amyloid beta have been hypothesized to be the most toxic, whereas fibrillar amyloid beta becomes deposited as amyloid plaques and congophilic angiopathy, which both serve as neuropathological markers of the disease. In addition, the accumulation of abnormally phosphorylated tau as soluble toxic oligomers and as neurofibrillary tangles is a critical part of the pathology. Numerous therapeutic interventions are under investigation to prevent and treat Alzheimer's disease. Among the most exciting and advanced of these approaches is vaccination. Immunomodulation is being tried for a range of neurodegenerative disorders, with great success being reported in most model animal trials; however, the much more limited human data have shown more modest clinical success so far, with encephalitis occurring in a minority of patients treated with active immunization. The immunomodulatory approaches for neurodegenerative diseases involve targeting a self-protein, albeit in an abnormal conformation; hence, effective enhanced clearance of the disease-associated conformer has to be balanced with the potential risk of stimulating excessive toxic inflammation within the central nervous system. The design of future immunomodulatory approaches that are more focused is dependent on addressing a number of questions, including when is the best time to start immunization, what are the most appropriate targets for vaccination, and is amyloid central to the pathogenesis of Alzheimer's disease or is it critical to target tau-related pathology also. In this review, we discuss the past experience with vaccination for Alzheimer's disease and the development of possible future strategies that target both amyloid beta-related and tau-related pathologies. Mt Sinai J Med 77:17&-31, 2010. (c) 2010 Mount Sinai School of Medicine

Novel agonists of TLR9 with two 5'-ends and synthetic immune stimulatory motifs, referred to as immune modulatory oligonucleotides (IMOs) are potent agonists of TLR9. In the present study, we have designed and synthesized 15 novel IMOs by incorporating specific chemical modifications and studied their immune response profiles both in vitro and in vivo. Analysis of the immunostimulatory profiles of these IMOs in human and NHP cell-based assays suggest that changes in the number of synthetic immunostimulatory motifs gave only a subtle change in immune stimulation of pDCs as indicated by IFN-alpha production and pDC maturation while the addition of self-complementary sequences produced more dramatic changes in both pDC and B cell stimulation. All IMOs induced cytokine production in vivo immediately after administration in mice. Representative compounds were also compared for the ability to stimulate cytokine production in vivo (IFN-alpha and IP-10) in rhesus macaques after intra-muscular administration.

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

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

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

The pathogenesis of prion diseases is related to conformational transformation of cellular prion protein (PrP(C)) into a toxic, infectious, and self-replicating conformer termed PrP(Sc). Following extracerebral inoculation, the replication of PrP(Sc) is confined for months to years to the lymporeticular system (LRS) before the secondary CNS involvement results in occurrence of neurological symptoms. Therefore, replication of PrP(Sc), in the early stage of infection can be targeted by therapeutic approaches, which like passive immunization have limited blood-brain-barrier penetration. In this study, we show that 6D11 anti-PrP monoclonal antibody (Mab) prevents infection on a FDC-P1 myeloid precursor cell line stably infected with 22L mouse adapted scrapie strain. Passive immunization of extracerebrally infected CD-1 mice with Mab 6D11 resulted in effective suppression of PrP(Sc) replication in the LRS. Although, a rebound of PrP(Sc) presence occurred when the Mab 6D11 treatment was stopped, passively immunized mice showed a prolongation of the incubation period by 36.9% (pb0.0001) and a significant decrease in CNS pathology compared to control groups receiving vehicle or murine IgG. Our results indicate that antibody-based therapeutic strategies can be used, even on a short-term basis, to delay or prevent disease in subjects accidentally exposed to prions