Astrid Bottelbergs

Intracerebral injection of preformed synthetic tau fibrils initiates widespread tauopathy and neuronal loss in the brains of tau transgenic mice.

Neurofibrillary tangles composed of hyperphosphorylated fibrillized tau are found in numerous tauopathies including Alzheimers disease. Increasing evidence suggests that tau pathology can be transmitted from cell-to-cell; however the mechanisms involved in the initiation of tau fibrillization and spreading of disease linked to progression of tau pathology are poorly understood. We show here that intracerebral injections of preformed synthetic tau fibrils into the hippocampus or frontal cortex of young tau transgenic mice expressing mutant human P301L tau induces tau hyperphosphorylation and aggregation around the site of injection, as well as a time-dependent propagation of tau pathology to interconnected brain areas distant from the injection site. Furthermore, we show that the tau pathology as a consequence of injection of tau preformed fibrils into the hippocampus induces selective loss of CA1 neurons. Together, our data confirm previous studies on the seeded induction and the spreading of tau pathology in a different tau transgenic mouse model and reveals neuronal loss associated with seeded tau pathology in tau transgenic mouse brain. These results further validate the utility of the tau seeding model in studying disease transmission, and provide a more complete in vivo tauopathy model with associated neurodegeneration which can be used to investigate the mechanisms involved in tau aggregation and spreading, as well as aid in the search for disease modifying treatments for Alzheimers disease and related tauopathies.

Comparison of New Tau PET-Tracer Candidates With [18F]T808 and [18F]T807

Early clinical results of two tau tracers, [18F]T808 and [18F]T807, have recently been reported. In the present study, the biodistribution, radiometabolite quantification, and competition-binding studies were performed in order to acquire comparative preclinical data as well as to establish the value of T808 and T807 as benchmark compounds for assessment of binding affinities of eight new/other tau tracers. Biodistribution studies in mice showed high brain uptake and fast washout. In vivo radiometabolite analysis using high-performance liquid chromatography showed the presence of polar radiometabolites in plasma and brain. No specific binding of [18F]T808 was found in transgenic mice expressing mutant human P301L tau. In semiquantitative autoradiography studies on human Alzheimer disease slices, we observed more than 50% tau selective blocking of [18F]T808 in the presence of 1 µmol/L of the novel ligands. This study provides a straightforward comparison of the binding affinity and selectivity for tau of the reported radiolabeled tracers BF-158, BF-170, THK5105, lansoprazole, astemizole, and novel tau positron emission tomography ligands against T807 and T808. Therefore, these data are helpful to identify structural requirements for selective interaction with tau and to compare the performance of new highly selective and specific radiolabeled tau tracers.

Quantitative μPET Imaging of Cerebral Glucose Metabolism and Amyloidosis in the TASTPM Double Transgenic Mouse Model of Alzheimer’s Disease

Positron emission tomography studies of cerebral glucose utilization and amyloid-β deposition with fluoro-deoxy-D-glucose ([(18)F]-FDG) and amyloid tracers have shown characteristic pathological changes in Alzheimers Disease that can be used for disease diagnosis and monitoring. Application of this technology to preclinical research with transgenic animal models would greatly facilitate drug discovery and further understanding of disease processes. The results from preclinical studies with these imaging biomarkers have however been highly inconsistent, causing doubts over whether animal models can truly replicate an AD-like phenotype. In this study we performed in vivo imaging with [(18)F]-FDG and [(18)F]-AV45 in double transgenic TASTPM mice, a transgenic model that been previously demonstrated high levels of fibrillar amyloid-β and decreases in cerebral glucose utilization with ex vivo techniques. Our results show widespread and significant retention of [(18)F]-AV45 (p < 0.0001) in aged TASTPM mice in addition to significant regional decreases in [(18)F]-FDG uptake (p < 0.05). In vivo quantification of amyloid-β showed a strong (Pearsons r = 0.7078), but not significant (p = 0.1156), positive correlation with ex vivo measures suggesting some limitations on tracer sensitivity. In the case of [(18)F]-FDG, voxelwise analysis greatly enhanced detection of hypometabolic regions. We further evidenced modest neuronal loss (thalamus p = 0.0318) that could underlie the observed hypometabolism. This research was performed in conjunction with the European Communitys Seventh Framework Program (FP7/2007-2013) for the Innovative Medicine Initiative under the PharmaCog Grant Agreement no.115009.

Systemic immune‐checkpoint blockade with anti‐PD1 antibodies does not alter cerebral amyloid‐β burden in several amyloid transgenic mouse models

Chronic inflammation represents a central component in the pathogenesis of Alzheimers disease (AD). Recent work suggests that breaking immune tolerance by Programmed cell Death‐1 (PD1) checkpoint inhibition produces an IFN‐γ‐dependent systemic immune response, with infiltration of the brain by peripheral myeloid cells and neuropathological as well as functional improvements even in mice with advanced amyloid pathology (Baruch et al., ( ): Nature Medicine, 22:135–137). Immune checkpoint inhibition was therefore suggested as potential treatment for neurodegenerative disorders when activation of the immune system is appropriate. Because a xenogeneic rat antibody (mAb) was used in the study, whether the effect was specific to PD1 target engagement was uncertain. In the present study we examined whether PD1 immunotherapy can lower amyloid‐β pathology in a range of different amyloid transgenic models performed at three pharmaceutical companies with the exact same anti‐PD1 isotype and two mouse chimeric variants. Although PD1 immunotherapy stimulated systemic activation of the peripheral immune system, monocyte‐derived macrophage infiltration into the brain was not detected, and progression of brain amyloid pathology was not altered. Similar negative results of the effect of PD1 immunotherapy on amyloid brain pathology were obtained in two additional models in two separate institutions. These results show that inhibition of PD1 checkpoint signaling by itself is not sufficient to reduce amyloid pathology and that additional factors might have contributed to previously published results (Baruch et al., ( ): Nature Medicine, 22:135–137). Until such factors are elucidated, animal model data do not support further evaluation of PD1 checkpoint inhibition as a therapeutic modality for Alzheimers disease.

INTRACEREBRAL INJECTION OF PREFORMED SYNTHETIC TAU FIBRILS INITIATES WIDESPREAD TAUOPATHY AND NEURONAL LOSS IN THE BRAINS OF TAU TRANSGENIC MICE

directed to understand and characterize the transmissible features of Ab and the role that spreading of Ab aggregation may play in the etiology and progression of AD.Methods: Several prion-like properties were tested in vivo for misfolded Ab, including: de novo transmission in a transgenic model that do not develop spontaneous Ab aggregates, pathological induction by different routes of exposure to Ab aggregates, titration of the inducible agent, and transmission using samples associated to early AD pathological changes (individuals affected by Mild Cognitive Impairment (MCI) and Non-Demented people with Alzheimer’s Neuropathology (NDAN)). Animals were sacrificed several months after administration of misfolded Ab and tissues were collected for biochemical and histological analyses. Induced pathology was compared to amyloid deposition naturally developed in transgenic animals at different ages. Results: A prion-like propagation of Ab misfolding was observed in several of the different paradigms explored. We measured the amount, brain distribution, morphological characteristics and profile of Ab aggregates generated in challenged mice. Ab misfolding was titrable in a similar way as observed for the prion infectious agent. We also observed an important induction of Ab misfolding by blood transfusion and other peripheral routes. Brain extracts from individuals classified as MCI and NDAN also promoted amyloid deposition and showed particular profiles of Ab aggregation in the brain of experimental subjects. Conclusions:Our findings, together with previously published reports, suggest that some aspects of AD pathology might be transmissible. However, additional experimental and epidemiological studies are necessary to unveil the role of these processes in the etiology of the disease in humans. These results may contribute to understand the mechanisms implicated in the initiation of Ab pathology and therefore be useful to develop new therapeutic strategies for the prevention and treatment of this devastating disease.

Evaluation of μPET outcome measures to detect disease modification induced by BACE inhibition in a transgenic mouse model of Alzheimer’s disease.

In this study, we investigated the effects of chronic administration of an inhibitor of the β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) on Alzheimer-related pathology by multitracer PET imaging in transgenic APPPS1-21 (TG) mice. Methods: Wild-type (WT) and TG mice received vehicle or BACE inhibitor (60 mg/kg) starting at 7 wk of age. Outcome measures of brain metabolism, neuroinflammation, and amyloid-β pathology were obtained through small-animal PET imaging with 18F-FDG, 18F-peripheral benzodiazepine receptor (18F-PBR), and 18F-florbetapir (18F-AV45), respectively. Baseline scans were acquired at 6–7 wk of age and follow-up scans at 4, 7, and 12 mo. 18F-AV45 uptake was measured at 8 and 13 mo of age. After the final scans, histologic measures of amyloid-β (4G8), microglia (ionized calcium binding adaptor molecule 1), astrocytes (glial fibrillary acidic protein), and neuronal nuclei were performed. Results: TG mice demonstrated significant age-associated increases in 18F-AV45 uptake. An effect of treatment was observed in the cortex (P = 0.0014), hippocampus (P = 0.0005), and thalamus (P < 0.0001). Histology confirmed reduction of amyloid-β pathology in TG-BACE mice. Regardless of treatment, TG mice demonstrated significantly lower 18F-FDG uptake than WT mice in the thalamus (P = 0.0004) and hippocampus (P = 0.0332). Neuronal nucleus staining was lower in both TG groups in the thalamus and cortex. 18F-PBR111 detected a significant age-related increase in TG mice (P < 0.0001) but did not detect the treatment-induced reduction in activated microglia as demonstrated by histology. Conclusion: Although 18F-FDG, 18F-PBR111, and 18F-AV45 all detected pathologic alterations between TG and WT mice, only 18F-AV45 could detect an effect of BACE inhibitor treatment. However, changes in WT binding of 18F-AV45 undermine the specificity of this effect.

SliceMap: an algorithm for automated brain region annotation

Summary Many neurodegenerative disorders, such as Alzheimers Disease, pertain to or spread from specific sites of the brain. Hence, accurate disease staging or therapy assessment in transgenic model mice demands automated analysis of selected brain regions. To address this need, we have developed an algorithm, termed SliceMap, that enables contextual quantification by mapping anatomical information onto microtome-cut brain slices. For every newly acquired high-resolution image of a brain slice, the algorithm performs a coarse congealing-based registration to a library of pre-annotated reference slices. A subset of optimally matching reference slices is then used for refined, elastic registration. Morphotextural metrics are used to measure registration performance and to automatically detect poorly cut slices. We have implemented our method as a plugin for FIJI image analysis freeware, and we have used it to regionally quantify tau pathology in brain slices from a tauopathy (P301S) mouse model. By enabling region-based quantification, our method contributes to a more accurate assessment of neurodegenerative disease development. Availability and implementation The method is available as a plugin for FIJI from https://github.com/mbarbie1/SliceMap/, along with an example dataset and user instructions. Contact winnok.devos@uantwerpen.be. Supplementary information Supplementary data are available at Bioinformatics online.

PRE-CLINICAL CHARACTERIZATION OF THE NOVEL TAU PET LIGAND [18F]-JNJ'067

widespread reduction in CVR, with the exception of occipital CVR. Results support the notion that older adults with cognitive impairment may experience an altered cerebrovascular state in which compensatory dilation relates to CBF in areas at elevated risk and further relates to diminished CVR in anterior regions. These results provide novel insight into intracranial structural-functional relations that cannot be explained by shared systemic vascular risk factors or advancing age.

[18F]THK-5117-PET AND [11C]PIB-PET IMAGING IN IDIOPATHIC NORMAL PRESSURE HYDROCEPHALUS (INPH) IN RELATION TO CONFIRMED AMYLOID-β PLAQUES AND TAU IN BRAIN BIOPSIES

non-specific binding of [C]FPS-ZM1 (5 nM or 10 nM; 75 mM of FPSZM1 for non-specific binding (NSB)) in cerebellar or extracerebellar regions of 8-month-old wild-type (WT) versus 17-month-old transgenic (TG; Tg2576) Alzheimer’s disease model mice brain (n1⁄43). Data expressed as a mean6 standard deviation (represented by error bars). No statistically significant differences were observed between the animal species, brain regions or different concentrations of the radiotracer. Poster Presentations: Wednesday, July 19, 2017 P1537