Binding of [18F]AV1451 in post mortem brain slices of semantic variant primary progressive aphasia patients

Abstract Purpose In vivo tau-PET tracer retention in the anterior temporal lobe of patients with semantic variant primary progressive aphasia (SV PPA) has consistently been reported. This is unexpected as the majority of these patients have frontotemporal lobar degeneration TDP (FTLD-TDP). Methods We conducted an in vitro [18F]AV1451 autoradiography binding study in five cases with a clinical diagnosis of SV PPA constituting the range of pathologies (i.e., three FTLD-TDP, one Alzheimer’s disease (AD), and one Pick’s disease (PiD)). Binding was compared with two controls without neurodegeneration, two typical AD, one corticobasal syndrome with underlying AD, and one frontotemporal dementia behavioral variant with FTLD-TDP. The effect of blocking with the authentic reference material and with the MAO-B inhibitor deprenyl was assessed. Immunohistochemistry was performed on adjacent cryosections. Results Absence of specific [18F]AV1451 binding was observed for all three SV PPA FTLD-TDP cases. The absence of binding in controls as well as the successful blocking with authentic AV1451 in cases with tauopathy demonstrated specificity of the [18F]AV1451 signal for tau. The specific [18F]AV1451 binding was highest in AD, followed by PiD. This binding colocalized with the respective tau lesions and could not be blocked by deprenyl. Similar pilot findings were obtained with [18F]THK5351. Conclusion In vitro autoradiography showed no [18F]AV1451 binding in SV PPA due to FTLD-TDP, while specific binding was present in SV PPA due to AD and PiD. The discrepancy between in vitro and in vivo findings remains to be explained. The discordance is not related to [18F]AV1451 idiosyncrasies as [18F]THK5351 findings were similar.

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[18F]AV-1451 binding in vivo mirrors the expected distribution of TDP-43 pathology in the semantic variant of primary progressive aphasia

Journal of Neurology Neurosurgery & Psychiatry ◽

10.1136/jnnp-2017-316402 ◽

2017 ◽

Vol 89 (10) ◽

pp. 1032-1037 ◽

Cited By ~ 43

Author(s):

W R Bevan-Jones ◽

Thomas E Cope ◽

P Simon Jones ◽

Luca Passamonti ◽

Young T Hong ◽

...

Keyword(s):

Frontotemporal Lobar Degeneration ◽

Primary Progressive Aphasia ◽

Hierarchical Cluster ◽

Clinical Syndrome ◽

Semantic Dementia ◽

Binding Potential ◽

Progressive Aphasia ◽

Primary Progressive ◽

Semantic Variant

IntroductionSemantic dementia, including the semantic variant of primary progressive aphasia (svPPA), is strongly associated with TAR-DNA binding protein 43 (TDP-43) type C pathology. It provides a useful model in which to test the specificity of in vivo binding of the putative tau ligand [18F]AV-1451, which is elevated in frontotemporal lobar degeneration tauopathies.Methods and resultsSeven patients (five with svPPA and two with ‘right’ semantic dementia) and 12 healthy controls underwent positron emission tomography brain imaging with [18F]AV-1451. Two independent preprocessing methods were used. For both methods, all patients had clearly elevated binding potential (BPND (non-displaceable binding potential)) in temporal lobes, lateralising according to their clinical syndrome and evident in raw images. Region of interest analyses confirmed that BPND was significantly increased in temporal regions, insula and fusiform gyrus, consistent with those areas known to be most affected in semantic dementia. Hierarchical cluster analysis, based on the distribution of [18F]AV-1451 binding potential, separated semantic dementia from controls with 86% sensitivity and 100% specificity.Conclusions[18F]AV-1451 binds in vivo regions that are likely to contain TDP-43 and not significant tau pathology. While this suggests a non-tau target for [18F]AV-1451, the pathological regions in semantic dementia do not normally contain significant levels of recently proposed ‘off target’ binding sites for [18F]AV-1451, such as neuronal monoamine oxidase or neuromelanin. Postmortem and longitudinal data will be useful to assess the utility of [18F]AV-1451 to differentiate and track different types of frontotemporal lobar degeneration.

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Neuroinflammation and protein aggregation co-localize across the frontotemporal dementia spectrum

Brain ◽

10.1093/brain/awaa033 ◽

2020 ◽

Vol 143 (3) ◽

pp. 1010-1026 ◽

Cited By ~ 12

Author(s):

W Richard Bevan-Jones ◽

Thomas E Cope ◽

P Simon Jones ◽

Sanne S Kaalund ◽

Luca Passamonti ◽

...

Keyword(s):

Protein Aggregation ◽

Frontotemporal Dementia ◽

Primary Progressive Aphasia ◽

Amyloid Β Protein ◽

Progressive Aphasia ◽

Primary Progressive ◽

Activated Microglia ◽

Clinical Syndromes ◽

Semantic Variant

Abstract The clinical syndromes of frontotemporal dementia are clinically and neuropathologically heterogeneous, but processes such as neuroinflammation may be common across the disease spectrum. We investigated how neuroinflammation relates to the localization of tau and TDP-43 pathology, and to the heterogeneity of clinical disease. We used PET in vivo with (i) 11C-PK-11195, a marker of activated microglia and a proxy index of neuroinflammation; and (ii) 18F-AV-1451, a radioligand with increased binding to pathologically affected regions in tauopathies and TDP-43-related disease, and which is used as a surrogate marker of non-amyloid-β protein aggregation. We assessed 31 patients with frontotemporal dementia (10 with behavioural variant, 11 with the semantic variant and 10 with the non-fluent variant), 28 of whom underwent both 18F-AV-1451 and 11C-PK-11195 PET, and matched control subjects (14 for 18F-AV-1451 and 15 for 11C-PK-11195). We used a univariate region of interest analysis, a paired correlation analysis of the regional relationship between binding distributions of the two ligands, a principal component analysis of the spatial distributions of binding, and a multivariate analysis of the distribution of binding that explicitly controls for individual differences in ligand affinity for TDP-43 and different tau isoforms. We found significant group-wise differences in 11C-PK-11195 binding between each patient group and controls in frontotemporal regions, in both a regions-of-interest analysis and in the comparison of principal spatial components of binding. 18F-AV-1451 binding was increased in semantic variant primary progressive aphasia compared to controls in the temporal regions, and both semantic variant primary progressive aphasia and behavioural variant frontotemporal dementia differed from controls in the expression of principal spatial components of binding, across temporal and frontotemporal cortex, respectively. There was a strong positive correlation between 11C-PK-11195 and 18F-AV-1451 uptake in all disease groups, across widespread cortical regions. We confirmed this association with post-mortem quantification in 12 brains, demonstrating strong associations between the regional densities of microglia and neuropathology in FTLD-TDP (A), FTLD-TDP (C), and FTLD-Pick's. This was driven by amoeboid (activated) microglia, with no change in the density of ramified (sessile) microglia. The multivariate distribution of 11C-PK-11195 binding related better to clinical heterogeneity than did 18F-AV-1451: distinct spatial modes of neuroinflammation were associated with different frontotemporal dementia syndromes and supported accurate classification of participants. These in vivo findings indicate a close association between neuroinflammation and protein aggregation in frontotemporal dementia. The inflammatory component may be important in shaping the clinical and neuropathological patterns of the diverse clinical syndromes of frontotemporal dementia.

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Flortaucipir tau PET imaging in semantic variant primary progressive aphasia

Journal of Neurology Neurosurgery & Psychiatry ◽

10.1136/jnnp-2017-316409 ◽

2017 ◽

Vol 89 (10) ◽

pp. 1024-1031 ◽

Cited By ~ 43

Author(s):

Sara J Makaretz ◽

Megan Quimby ◽

Jessica Collins ◽

Nikos Makris ◽

Scott McGinnis ◽

...

Keyword(s):

Pet Imaging ◽

Visual Inspection ◽

Primary Progressive Aphasia ◽

Structural Mri ◽

Tracer Uptake ◽

Amyloid Pet ◽

Progressive Aphasia ◽

Primary Progressive ◽

Pet Tracer ◽

Semantic Variant

ObjectiveThe semantic variant of primary progressive aphasia (svPPA) is typically associated with frontotemporal lobar degeneration (FTLD) with longTAR DNA-binding protein (TDP)-43-positive neuropil threads and dystrophic neurites (type C), and is only rarely due to a primary tauopathy or Alzheimer’s disease. We undertook this study to investigate the localisation and magnitude of the presumed tau Positron Emission Tomography (PET) tracer [18F]Flortaucipir (FTP; also known as T807 or AV1451) in patients with svPPA, hypothesising that most patients would not show tracer uptake different from controls.MethodsFTP and [11C]Pittsburgh compound B PET imaging as well as MRI were performed in seven patients with svPPA and in 20 controls. FTP signal was analysed by visual inspection and by quantitative comparison to controls, with and without partial volume correction.ResultsAll seven patients showed elevated FTP uptake in the anterior temporal lobe with a leftward asymmetry that was not observed in healthy controls. This elevated FTP signal, largely co-localised with atrophy, was evident on both visual inspection and quantitative cortical surface-based analysis. Five patients were amyloid negative, one was amyloid positive and one has an unknown amyloid status.ConclusionsIn this series of patients with clinical profiles, structural MRI and amyloid PET imaging typical for svPPA, FTP signal was unexpectedly elevated with a spatial pattern localised to areas of atrophy. This raises questions about the possible off-target binding of this tracer to non-tau molecules associated with neurodegeneration. Further investigation with autopsy analysis will help illuminate the binding target(s) of FTP in cases of suspected FTLD-TDP neuropathology.

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Supplemental Material for The Concept of Regularization: Resolving the Problem of Surface Dyslexia in Semantic Variant Primary Progressive Aphasia Across Different Languages

Neuropsychology ◽

10.1037/neu0000611.supp ◽

2019 ◽

Keyword(s):

Primary Progressive Aphasia ◽

Progressive Aphasia ◽

Primary Progressive ◽

Semantic Variant ◽

Surface Dyslexia

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Primary Progressive Aphasia: Toward a Pathophysiological Synthesis

Current Neurology and Neuroscience Reports ◽

10.1007/s11910-021-01097-z ◽

2021 ◽

Vol 21 (3) ◽

Author(s):

Justina Ruksenaite ◽

Anna Volkmer ◽

Jessica Jiang ◽

Jeremy CS Johnson ◽

Charles R Marshall ◽

...

Keyword(s):

Care Management ◽

Primary Progressive Aphasia ◽

Disease Stage ◽

Major Step ◽

Progressive Aphasia ◽

Primary Progressive ◽

New Findings ◽

Critical Issues ◽

Semantic Variant ◽

Auditory Impairments

Abstract Purpose of Review The term primary progressive aphasia (PPA) refers to a diverse group of dementias that present with prominent and early problems with speech and language. They present considerable challenges to clinicians and researchers. Recent Findings Here, we review critical issues around diagnosis of the three major PPA variants (semantic variant PPA, nonfluent/agrammatic variant PPA, logopenic variant PPA), as well as considering ‘fragmentary’ syndromes. We next consider issues around assessing disease stage, before discussing physiological phenotyping of proteinopathies across the PPA spectrum. We also review evidence for core central auditory impairments in PPA, outline critical challenges associated with treatment, discuss pathophysiological features of each major PPA variant, and conclude with thoughts on key challenges that remain to be addressed. Summary New findings elucidating the pathophysiology of PPA represent a major step forward in our understanding of these diseases, with implications for diagnosis, care, management, and therapies.

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Breakdowns in Informativeness of Naturalistic Speech Production in Primary Progressive Aphasia

Brain Sciences ◽

10.3390/brainsci11020130 ◽

2021 ◽

Vol 11 (2) ◽

pp. 130

Author(s):

Jeanne Gallée ◽

Claire Cordella ◽

Evelina Fedorenko ◽

Daisy Hochberg ◽

Alexandra Touroutoglou ◽

...

Keyword(s):

Primary Progressive Aphasia ◽

Speech Analysis ◽

Clinical Settings ◽

Functional Communication ◽

Or Efficiency ◽

Progressive Aphasia ◽

Primary Progressive ◽

Communication Impairment ◽

Semantic Variant ◽

Lower Production

“Functional communication” refers to an individual’s ability to communicate effectively in his or her everyday environment, and thus is a paramount skill to monitor and target therapeutically in people with aphasia. However, traditional controlled-paradigm assessments commonly used in both research and clinical settings often fail to adequately capture this ability. In the current study, facets of functional communication were measured from picture-elicited speech samples from 70 individuals with mild primary progressive aphasia (PPA), including the three variants, and 31 age-matched controls. Building upon methods recently used by Berube et al. (2019), we measured the informativeness of speech by quantifying the content of each patient’s description that was relevant to a picture relative to the total amount of speech they produced. Importantly, form-based errors, such as mispronunciations of words, unusual word choices, or grammatical mistakes are not penalized in this approach. We found that the relative informativeness, or efficiency, of speech was preserved in non-fluent variant PPA patients as compared with controls, whereas the logopenic and semantic variant PPA patients produced significantly less informative output. Furthermore, reduced informativeness in the semantic variant is attributable to a lower production of content units and a propensity for self-referential tangents, whereas for the logopenic variant, a lower production of content units and relatively ”empty” speech and false starts contribute to this reduction. These findings demonstrate that functional communication impairment does not uniformly affect all the PPA variants and highlight the utility of naturalistic speech analysis for measuring the breakdown of functional communication in PPA.

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Development of 18F-Labeled Radiotracers for PET Imaging of the Adenosine A2A Receptor: Synthesis, Radiolabeling and Preliminary Biological Evaluation

International Journal of Molecular Sciences ◽

10.3390/ijms22052285 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2285

Author(s):

Thu Hang Lai ◽

Susann Schröder ◽

Magali Toussaint ◽

Sladjana Dukić-Stefanović ◽

Mathias Kranz ◽

...

Keyword(s):

Specific Binding ◽

Brain Slices ◽

Total Activity ◽

Biological Evaluation ◽

Adenosine A2a Receptor ◽

Positron Emission ◽

A2a Receptor ◽

Adenosine A2a

The adenosine A2A receptor (A2AR) represents a potential therapeutic target for neurodegenerative diseases. Aiming at the development of a positron emission tomography (PET) radiotracer to monitor changes of receptor density and/or occupancy during the A2AR-tailored therapy, we designed a library of fluorinated analogs based on a recently published lead compound (PPY). Among those, the highly affine 4-fluorobenzyl derivate (PPY1; Ki(hA2AR) = 5.3 nM) and the 2-fluorobenzyl derivate (PPY2; Ki(hA2AR) = 2.1 nM) were chosen for 18F-labeling via an alcohol-enhanced copper-mediated procedure starting from the corresponding boronic acid pinacol ester precursors. Investigations of the metabolic stability of [18F]PPY1 and [18F]PPY2 in CD-1 mice by radio-HPLC analysis revealed parent fractions of more than 76% of total activity in the brain. Specific binding of [18F]PPY2 on mice brain slices was demonstrated by in vitro autoradiography. In vivo PET/magnetic resonance imaging (MRI) studies in CD-1 mice revealed a reasonable high initial brain uptake for both radiotracers, followed by a fast clearance.

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