Faculty Bibliography

Alzheimer's disease (AD), the most prevalent form of dementia worldwide, can be deemed as the next global health epidemic. The biochemistry underlying deposition of amyloid beta (A beta) and hyperphosphorylated tau aggregates in AD has been extensively studied. The oligomeric forms of A beta that are derived from the normal soluble A beta peptides are believed to be the most toxic. However, it is the fibrillar Abeta form that aggregates as amyloid plaques and cerebral amyloid angiopathy, which serve as pathological hallmarks of AD. Moreover, deposits of abnormally phosphorylated tau that form soluble toxic oligomers and then accumulate as neurofibrillary tangles are an essential part of AD pathology. Currently, many strategies are being tested that either inhibit, eradicate or prevent the development of plaques in AD. An exciting new approach on the horizon is the immunization approach. Dramatic results from AD animal models have shown promise for active and passive immune therapies targeting A beta. However, there is very limited data in humans that suggests a clear benefit. Some hurdles faced with these studies arise from complications noted with therapy. Encephalitis has been reported in trials of active immunization and vasogenic edema or amyloid - related imaging abnormalities (ARIA) has been reported with passive immunization in a minority of patients. As yet, therapies targeting only tau are still limited to mouse models with few studies targeting both pathologies. As the majority of approaches tried so far are based on targeting a self - protein, though in an abnormal conformation, benefits of therapy need to be balanced against the possible risks of stimulating excessive toxic inflammation. For better efficacy, future strategies will need to focus on the toxic oligomers and targeting all aspects of AD pathology.

BACKGROUND: Central to the pathogenesis of Alzheimer's disease (AD) and many other neurodegenerative diseases is the conformational change of a normal self-protein into toxic oligomeric species and amyloid deposits. None of these disorders have an effective therapy, but immunization approaches hold great promise. We have previously shown that active immunization with a novel peptide when polymerized into a stable oligomeric conformation, pBri, induced a humoral immune response to toxic Abeta species in an AD model, APP/PS1 transgenic (Tg) mice, reducing plaque deposits. pBri is a glutaraldehyde polymerized form of the carboxyl fragment of an amyloidogenic protein, which is deposited in the brains of patients with a rare autosomal dominant disease due to a missense mutation in a stop codon, resulting in the translation of an intronic sequence, with no known sequence homology to any mammalian protein. METHODS: In the current study we tested whether pBri-peptide-based immunomodulation is effective at reducing both vascular amyloid deposits and tau-related pathology using TgSwDI mice with extensive congophilic angiopathy and 3xTg mice with tau pathology. RESULTS: Our results indicate that this immunomodulation approach, which produces a humoral response to proteins in a pathological conformation, is effective at reducing both Abeta and tau-related pathologies. CONCLUSIONS: This immunomodulatory approach has the advantage of using a non-self-immunogen that is less likely to be associated with autoimmune toxicity. Furthermore we found that it is able to target all the cardinal features of AD concurrently.

HIV-ITP patients have a unique antibody (Ab) against platelet GPIIIa49-66 which induces oxidative platelet fragmentation in the absence of complement (Cell 106: 551, 2001; JCI 113: 973, 2004). The search for a physiologic ligand that could induce this reaction was undertaken by panning the GPIIIa49-66 peptide with a phage surface display 7-mer peptide library. From 20 positive clones, 1 had 70% identity with a C-terminal region of ADAMTS-18 (a disintegrin and metalloproteinase with thrombospondin (TSR)-like motif 18), which is secreted by endothelial cell (EC). The recombinant C-terminal fragment of ADAMTS-18 can completely dissolve platelet aggregates formed in vitro. Moreover, this fragment lyses thrombi formed in the cerebral artery of mice and reduces infarction and neurologic impairment in murine ischemic stroke model (Blood 113: 6051, 2009). However, whether ADAMTS-18 represents the dominant physiologic mechanism controlling thrombus dissolution in vivo remains to be clarified. Here, we used ADAMTS-18-deficient (ADAMTS-18^-/-) mice to study the contributions of ADAMTS-18 to thrombus formation in vivo. To investigate possible functional differences between WT and ADAMTS-18^-/- platelets, we tested WT and ADAMTS-18^-/- platelets in a model of pulmonary thromboembolism induced by infusion of a mixture of platelet agonist collagen (25 mug per mouse) and epinephrine (1 mug per mouse). In lung tissue Hematoxylin and eosin-stained (HE) slides, the mean number of thrombi per lung was same in the ADAMTS-18^-/- group compared with WT group (163.7 +/-14.38 vs 174.9 +/-11.73, n=30/group, P=0.5480). In vitro, there is no difference between WT and ADAMTS-18^-/- platelet aggregation trace and activation initiated by various platelet agonists ADP (10 muM) or collagen (2 mug/mL). No difference was noted on WT and ADAMTS-18^-/- platelet adhesion on immobilized ligand (fibrinogen). These results indicated ADAMTS-18 had no effect on platelet functio!

Soluble amyloid-beta oligomers (Abetao) trigger Alzheimer's disease (AD) pathophysiology and bind with high affinity to cellular prion protein (PrP(C)). At the postsynaptic density (PSD), extracellular Abetao bound to lipid-anchored PrP(C) activates intracellular Fyn kinase to disrupt synapses. Here, we screened transmembrane PSD proteins heterologously for the ability to couple Abetao-PrP(C) with Fyn. Only coexpression of the metabotropic glutamate receptor, mGluR5, allowed PrP(C)-bound Abetao to activate Fyn. PrP(C) and mGluR5 interact physically, and cytoplasmic Fyn forms a complex with mGluR5. Abetao-PrP(C) generates mGluR5-mediated increases of intracellular calcium in Xenopus oocytes and in neurons, and the latter is also driven by human AD brain extracts. In addition, signaling by Abetao-PrP(C)-mGluR5 complexes mediates eEF2 phosphorylation and dendritic spine loss. For mice expressing familial AD transgenes, mGluR5 antagonism reverses deficits in learning, memory, and synapse density. Thus, Abetao-PrP(C) complexes at the neuronal surface activate mGluR5 to disrupt neuronal function.

Background: Immunomodulation has shown great promise as an Alzheimer's disease (AD) therapy but major limitations must be overcome, such as the need for effectively reducing cerebral amyloid angiopathy (CAA), without associated hemorrhages. CAA is a common feature in AD and cognitively normal elderly individuals. Our initial findings indicate that stimulation of innate immunity with CpG ODN appears to be an effective means of reducing vascular amyloid without inducing toxicity in AD mouse models. We are currently testing our approach in a well characterized nonhuman primate model of sporadic CAA, squirrel monkey (Saimiri Boliviensis), which share numerous biological similarities with humans. Methods: Varying doses of the class B CpG ODN preparation containing the primate specific immunostimulatory sequence were administered in young monkeys by a subcutaneous route (s.c.). The most effective and non-toxic dosage described in young animals was selected for our long term studies in the older animals (with expected CAA deposits). During the treatment, primates were closely monitored for signs of toxicity. The peripheral cytokine responses were determined in PBMC supernatants and plasma from control and treated monkeys at selected time points. In addition, the performances on cognitive tests are being compared between our aged and young squirrel monkeys. Results: We have shown that a TLR9 agonist prevented shortterm memory deficits in Tg-SwDI mice, a model with extensive CAA. CpG ODN treatment led to a reduction of CAA in the absence of microhemorrhages and increased inflammation. Transgenic models are ideal for initial screening of a potential therapy but prior to clinical trials it is imperative to perform studies in non-human primates, which are a more biologically proximate model to humans. Short duration safety and efficacy assessment studies were first performed in young monkeys. Characterization of immune responses and evaluation of cognitive function and working memory in our monkeys is curr!

Background: We have shown that active immunization with a novel nonself amyloidogenic peptide (pABri) induced a humoral immune response, largely IgM, to both PHF and toxic Abeta species inAD model, APP/PS1 transgenic (Tg) mice. Histology revealed a lower amyloid burden in both the cortex and hippocampus, along with improved cognitive testing scores compared to controls. pABri immunization resulted in lower levels of soluble and insoluble Abeta42 and Abeta40 in Tg mice. Plasma from these mice was used to immunostain human AD temporal cortex brain tissue. Staining of cytoplasm and dendrites of neurons, paired helical filaments, and Abeta plaques was documented. Methods: The novel peptide, pABri, is a carboxyl fragment of an amyloidogenic protein which is deposited in the brain of patients with a rare autosomal dominant disease due to a missense mutation in a stop codon, resulting in the translation of an intronic sequence, with no known sequence homology to any mammalian protein. Hence, this immunomodulatory therapeutic is unlikely to produce autoimmune toxicity since it utilizes a non-self peptide. This current study utilizes the pABri peptide as an immunogen for active immunization in two other mouse AD Tg models: 3xTg, with tau and amyloid pathology, and TgSwDI, with extensive congophilic angiopathy. Toxicity, neuropathology, humoral immune responses, and cognitive behavior were assessed. Results: The antibodies produced are against both the primary sequence of the immunogen as well as to the pathology associated b-sheet structure that is shared by both NFTs and amyloid plaques. These conformationally specific antibodies, reacting to Abeta peptide and tau oligomers, are against a b-sheet conformation since the immunogen, pAbri, is predominantly in such a conformation. Treatment led to cognitive rescue with pABri matching cognition of WT mice. Brain homogenates revealed lower Abeta40 and Abeta42 levels in pABri treated 3xTg mice compared to controls. pABri treatment groups show lower amyloid bu!

Background: Currently there is no effective therapy for Alzheimer's Disease (AD). Active and passive immunomodulation still holds promise but current attempts only address one side of the pathology: either amyloid beta (Abeta) or the hyperphosphorylated tau (ptau) protein. Furthermore current approaches are not specific for the pathological conformers of either protein. From our novel immunization method targeting pathological beta-sheet conformation (PLoS ONE 5(10): e13391, 2010) we have developed monoclonal antibodies, some of them with promising binding capacities; and we propose to characterize a monoclonal specific for pathological conformers of Abeta and tau (TAB1) to be used for immunotherapy in AD mouse models. Methods: Monoclonal antibodies were obtained from our conformational inoculation of BALBc mice. Positive hybridomas were selected by their shared reactivity against Abeta, PHF and PrP Res. The best conformational candidate (TAB1) was selected after characterization by blots, ELISA and histology against pathological conformers in AD tissue. TAB1 is being used of treatment by intraperitoneal injection in 3xTg mice with both tau and Abeta related pathology. Results: TAB1 on tissue sections specifically immunolabels AD tissue with no labeling in young, health normal control brains. On Western blots TAB1 detects purified paired helical filament preparations, aggregated/ oligomeric Abeta and PrP Res, extracted from CJD brain tissue. Use of TAB1 therapeutically in 3xTg mice is on-going. Conclusions: We have developed a novel immunization procedure which we have used to produce monoclonal antibodies (mAbs) that recognize multiple pathological proteins, including PrP Res, oligomer A beta and ptau. We have characterized one of these mAbs, TAB1, which gives specific immunolabeling in AD tissue and onWestern blots to pathological conformers.We believe that immunotherapy that specifically targets the most toxic, oligomeric forms of Abeta and ptau, has the greatest chance of success with littl!

Background: Atrophy of the hippocampus is a key pathological hallmark of Alzheimer's disease (AD). An interest of subfields of hippocampal imaging has emerged in recent years due to the advent of ultra-high field MR. This work was to evaluate the imaging parameters on human postmortem brain at 7T MR using 3D susceptibility-sensitivity imaging (SWI) with enhanced tissue susceptibility contrast to better identify these layers and hippocampal subfields that are not available on conventional MR in order to better understand the transition of the hippocampus in AD as disease progresses. Methods: Imaging was performed on a 7.0T Siemens MAGNETOM using a 24-element phased array head coil. Post-mortem brain specimens of the hippocampus were obtained from 3 patients (mean: 72.2+4.3 years) with clinically diagnosed AD and 4 age-matched healthy controls (71.4+5.2 years). Coronal brain slices were preserved and fixed in 2% agar for this study. High resolution 3D SWI was obtained with isotropic voxel size 150~320mum. For imaging optimization to better visualize amyloid plaques, we varied TR, TE, BWand flip angle from 30-100ms, 12-36ms, 60-140Hz/ pixel and 10-40degree; respectively. The SWI filtered phase images were used (multiplication factor of 4 ~ 8) to enhance susceptibility contrast in the SWI images. Results: With optimal SWI parameters TR/TE/FA of 80ms/ 20ms/30IS at 7T, Figure 1 exemplifies the excellent image contrast for visualization of hippocampal layers (Fig A) and subfields (Fig B) in an elderly post-mortem brain without AD, specifically for cell types/layers: (1) Alveus; (2) Stratum Oriens; (3) Stratum Pyramidale; (4) Stratum Radiatum; (5) Stratum Lacunosum; (6) Stratum Moleculare; and for Hippocampal Formation subfields: (1) Hippocampal Head; (2, 2') Dentate Gyrus, (3, 3') Cornu Ammonis (CA1), (4) CA2, (5) CA3, (6) Pre-Subiculum/ Subiculum, (7) Para-Subiculum, (8) Entorhinal Cortex. There was significant atrophy of the whole hippocampal formation and subfields inADsamples with lessening of the!

Individuals with autism demonstrate atypical gaze, impairments in smooth pursuit, altered movement perception and deficits in facial perception. The olivo-floccular neuronal circuit is a major contributor to eye movement control. This study of the cerebellum in 12 autistic and 10 control subjects revealed dysplastic changes in the flocculus of eight autistic (67%) and two control (20%) subjects. Defects of the oculomotor system, including avoidance of eye contact and poor or no eye contact, were reported in 88% of autistic subjects with postmortem-detected floccular dysplasia. Focal disorganization of the flocculus cytoarchitecture with deficit, altered morphology, and spatial disorientation of Purkinje cells (PCs); deficit and abnormalities of granule, basket, stellate and unipolar brush cells; and structural defects and abnormal orientation of Bergmann glia are indicators of profound disruption of flocculus circuitry in a dysplastic area. The average volume of PCs was 26% less in the dysplastic region than in the unaffected region of the flocculus (p<0.01) in autistic subjects. Moreover, the average volume of PCs in the entire cerebellum was 25% less in the autistic subjects than in the control subjects (p<0.001). Findings from this study and a parallel study of the inferior olive (IO) suggest that focal floccular dysplasia combined with IO neurons and PC developmental defects may contribute to oculomotor system dysfunction and atypical gaze in autistic subjects.

The CD40 receptor-CD40 ligand (CD40-CD40L) interaction has been shown to affect both immune and non-immune cells and is implicated in diverse activities including immunoglobulin class switching (IgM to IgG), atherosclerosis, chronic inflammation and Alzheimer's disease pathogenesis. A number of groups have studied the role of CD40 in prion disease, however, the results are conflicting presumably due to the use of different scrapie agent-host strain combinations and routes of infection. In the current study, we clarify the effect of CD40 on: (i) replication, progression to clinical disease, PrP(Sc) profile, and neuropathology associated with infection of a single host genotype with three distinct mouse-adapted scrapie strains, and (ii) the immune response of double knockout (PrP, CD40) transgenic mice to recombinant PrP as assessed by the generation of anti-PrP antibodies. Our results suggest that CD40: (i) results in slower disease progression and scrapie strain-specific differences in incubation periods, (ii) does not affect the level of scrapie strain-specific PrP(Sc), (iii) does not influence disease-associated neuropathology, but (iv), as expected, is required to mount an immune response generating anti-PrP IgG antibodies.