Human Prion Disorders: Review of the Current Literature and a Twenty-Year Experience of the National Surveillance Center in the Czech Republic

Synthesis and Biological Evaluation of Novel 2-(Benzofuran-2-yl)-chromone Derivatives for In Vivo Imaging of Prion Deposits in the Brain

Prion diseases are fatal neurodegenerative disorders caused by the deposition of scrapie prion protein aggregates (PrP^Sc) in the brain. We previously reported that styrylchromone (SC) and benzofuran (BF) derivatives have potential as imaging probes for PrP^Sc. To further improve their properties, we designed and synthesized 2-(benzofuran-2-yl)-chromone (BFC) derivatives hybridized with SC and BF backbones as novel single-photon emission computed tomography probes for the detection of cerebral PrP^Sc deposits. Recombinant mouse prion protein (rMoPrP) aggregates and mouse-adapted bovine spongiform encephalopathy (mBSE)-infected mice were used to evaluate the binding properties of BFC derivatives to PrP^Sc. The BFC derivatives exhibited high binding affinities (equilibrium dissociation constant [K_d] = 22.6-47.7 nM) for rMoPrP aggregates. All BFC derivatives showed remarkable selectivity against amyloid beta aggregates. Fluorescence microscopy confirmed that the fluorescence signals of the BFC derivatives corresponded to the antibody-positive deposits of PrP^Sc in mBSE-infected mouse brains. Among the BFC derivatives, [¹²⁵I]BFC-OMe and [¹²⁵I]BFC-NH₂ exhibited high brain uptake and favorable washout from the mouse brain. In vitro autoradiography demonstrated that the distribution of [¹²⁵I]BFC-OMe in the brain tissues of mBSE-infected mice was colocalized with PrP^Sc deposits. Taken together, BFC derivatives appear to be promising prion imaging probes.

Case Report: A Case of Creutzfeldt–Jakob Heidenhain Variant Simulating PRES

The Heidenhain Variant of Creutzfeldt–Jakob disease (CJD) is an uncommon early clinical syndrome of the otherwise regular sporadic CJD, which belongs to the group of prion diseases caused by a transmissible agent, the misfolded form of the prion protein. The most characteristic symptoms of CJD are rapidly progressive cognitive impairment, typical motor manifestations and mental and behavioural changes. Conversely, in the Heidenhain Variant, different kinds of visual disturbances are observed at onset due to microvacuolar spongiform degeneration or, less frequently, confluent spongiform changes in the parieto-occipital area, detectable through brain MRI with hyperintensity in T2-FLAIR or DWI in the same areas. Since this an extremely rare condition with a heterogeneous clinical presentation, it may easily be misdiagnosed with other diseases at the earlier stages. Here, we describe the case of a patient initially diagnosed with posterior reversible encephalopathy syndrome (PRES), presenting with visual disturbances and headache at onset in a context of poorly controlled arterial hypertension. Subsequently, a rapid worsening of cognitive decline, associated with myoclonus and startle reaction led to further investigations, shifting the diagnosis toward a rapidly evolving neurodegenerative form. This hypothesis was also supported by EEG traces, MRI and CSF analysis. Finally, the clinical–instrumental evolution confirmed the diagnosis of Heidenhain Variant of CJD.

Biomarkers Analysis and Clinical Manifestations in Comorbid Creutzfeldt–Jakob Disease: A Retrospective Study in 215 Autopsy Cases

Creutzfeldt–Jakob disease (CJD), the most common human prion disorder, may occur as “pure” neurodegeneration with isolated prion deposits in the brain tissue; however, comorbid cases with different concomitant neurodegenerative diseases have been reported. This retrospective study examined correlations of clinical, neuropathological, molecular-genetic, immunological, and neuroimaging biomarkers in pure and comorbid CJD. A total of 215 patients have been diagnosed with CJD during the last ten years by the Czech National Center for Prion Disorder Surveillance. Data were collected from all patients with respect to diagnostic criteria for probable CJD, including clinical description, EEG, MRI, and CSF findings. A detailed neuropathological analysis uncovered that only 11.16% were “pure” CJD, while 62.79% had comorbid tauopathy, 20.47% had Alzheimer’s disease, 3.26% had frontotemporal lobar degeneration, and 2.33% had synucleinopathy. The comorbid subgroup analysis revealed that tauopathy was linked to putaminal hyperintensity on MRIs, and AD mainly impacted the age of onset, hippocampal atrophy on MRIs, and beta-amyloid levels in the CSF. The retrospective data analysis found a surprisingly high proportion of comorbid neuropathologies; only 11% of cases were verified as “pure” CJD, i.e., lacking hallmarks of other neurodegenerations. Comorbid neuropathologies can impact disease manifestation and can complicate the clinical diagnosis of CJD.

Extracellular Prion Protein Aggregates in Nine Gerstmann–Sträussler–Scheinker Syndrome Subjects with Mutation P102L: A Micromorphological Study and Comparison with Literature Data

Gerstmann–Sträussler–Scheinker syndrome (GSS) is a hereditary neurodegenerative disease characterized by extracellular aggregations of pathological prion protein (PrP) forming characteristic plaques. Our study aimed to evaluate the micromorphology and protein composition of these plaques in relation to age, disease duration, and co-expression of other pathogenic proteins related to other neurodegenerations. Hippocampal regions of nine clinically, neuropathologically, and genetically confirmed GSS subjects were investigated using immunohistochemistry and multichannel confocal fluorescent microscopy. Most pathognomic prion protein plaques were small (2–10 µm), condensed, globous, and did not contain any of the other investigated proteinaceous components, particularly dystrophic neurites. Equally rare (in two cases out of nine) were plaques over 50 µm having predominantly fibrillar structure and exhibit the presence of dystrophic neuritic structures; in one case, the plaques also included bulbous dystrophic neurites. Co-expression with hyperphosphorylated protein tau protein or amyloid beta-peptide (Aβ) in GSS PrP plaques is generally a rare observation, even in cases with comorbid neuropathology. The dominant picture of the GSS brain is small, condensed plaques, often multicentric, while presence of dystrophic neuritic changes accumulating hyperphosphorylated protein tau or Aβ in the PrP plaques are rare and, thus, their presence probably constitutes a trivial observation without any relationship to GSS development and progression.