Epitope mapping of the protease resistant products of RT-QuIC does not allow the discrimination of sCJD subtypes

Unveiling the Significance of Peroxiredoxin 6 in Central Nervous System Disorders

Peroxiredoxin 6 (Prdx6), a unique 1-Cys member of the peroxiredoxin family, exhibits peroxidase activity, phospholipase activity, and lysophosphatidylcholine acyltransferase (LPCAT) activity. Prdx6 has been known to be an important enzyme for the maintenance of lipid peroxidation repair, cellular metabolism, inflammatory signaling, and antioxidant damage. Growing research has demonstrated that the altered activity of this enzyme is linked with various pathological processes including central nervous system (CNS) disorders. This review discusses the distinctive structure, enzyme activity, and function of Prdx6 in different CNS disorders, as well as emphasizing the significance of Prdx6 in neurological disorders.

Role of Biomarkers for the Diagnosis of Prion Diseases: A Narrative Review

Prion diseases are progressive and irreversible neurodegenerative disorders with a low incidence (1.5–2 cases per million per year). Genetic (10–15%), acquired (anecdotal) and sporadic (85%) forms of the disease have been described. The clinical spectrum of prion diseases is very varied, although the most common symptoms are rapidly progressive dementia, cerebellar ataxia and myoclonus. Mean life expectancy from the onset of symptoms is 6 months. There are currently diagnostic criteria based on clinical phenotype, as well as neuroimaging biomarkers (magnetic resonance imaging), neurophysiological tests (electroencephalogram and polysomnogram), and cerebrospinal fluid biomarkers (14-3-3 protein and real-time quaking-induced conversion (RT-QuIC)). The sensitivity and specificity of some of these tests (electroencephalogram and 14-3-3 protein) is under debate and the applicability of other tests, such as RT-QuIC, is not universal. However, the usefulness of these biomarkers beyond the most frequent prion disease, sporadic Creutzfeldt–Jakob disease, remains unclear. Therefore, research is being carried out on new, more efficient cerebrospinal fluid biomarkers (total tau, ratio total tau/phosphorylated tau and neurofilament light chain) and potential blood biomarkers (neurofilament light chain, among others) to try to universalize access to early diagnosis in the case of prion diseases.

Sporadic Creutzfeldt-Jakob disease: Real-Time Quaking Induced Conversion (RT-QuIC) assay represents a major diagnostic advance

Sporadic Creutzfeldt-Jakob disease (sCJD) is a rare and fatal neurodegenerative disorder with an incidence of 1.5 to 2 cases per million population/year. The disease is caused by a proteinaceous infectious agent, named prion (or PrPSc), which arises from the conformational conversion of the cellular prion protein (PrPC). Once formed, PrPSc interacts with the normally folded PrPC coercing it to undergo similar structural rearrangement. The disease is highly heterogeneous from a clinical and neuropathological point of view. The origin of this variability lies in the aberrant structures acquired by PrPSc. At least six different sCJD phenotypes have been described and each of them is thought to be caused by a peculiar PrPSc strain. Definitive sCJD diagnosis requires brain analysis with the aim of identifying intracerebral accumulation of PrPSc which currently represents the only reliable biomarker of the disease. Clinical diagnosis of sCJD is very challenging and is based on the combination of several clinical, instrumental and laboratory tests representing surrogate disease biomarkers. Thanks to the advent of the ultrasensitive Real-Time Quaking-Induced Conversion (RT-QuIC) assay, PrPSc was found in several peripheral tissues of sCJD patients, sometimes even before the clinical onset of the disease. This discovery represents an important step forward for the clinical diagnosis of sCJD. In this manuscript, we present an overview of the current applications and future perspectives of RT-QuIC in the field of sCJD diagnosis.

Subtype Diagnosis of Sporadic Creutzfeldt-Jakob Disease with Diffusion Magnetic Resonance Imaging

Objective

Sporadic Creutzfeldt–Jakob disease (sCJD) comprises several subtypes as defined by genetic and prion protein characteristics, which are associated with distinct clinical and pathological phenotypes. To date, no clinical test can reliably diagnose the subtype. We established two procedures for the antemortem diagnosis of sCJD subtype using diffusion magnetic resonance imaging (MRI).

Methods

MRI of 1,458 patients referred to the National Prion Disease Pathology Surveillance Center were collected through its consultation service. One neuroradiologist blind to the diagnosis scored 12 brain regions and generated a lesion profile for each MRI scan. We selected 487 patients with autopsy‐confirmed diagnosis of “pure” sCJD subtype and at least one positive diffusion MRI examination. We designed and tested two data‐driven procedures for subtype diagnosis: the first procedure—prion subtype classification algorithm with MRI (PriSCA_MRI)—uses only MRI examinations; the second—PriSCA_MRI + Gen—includes knowledge of the prion protein codon 129 genotype, a major determinant of sCJD subtypes. Both procedures were tested on the first MRI and the last MRI follow‐up.

Results

PriSCA_MRI classified the 3 most prevalent subtypes with 82% accuracy.

PriSCA_MRI + Gen raised the accuracy to 89% and identified all subtypes.

Individually, the 2 most prevalent sCJD subtypes, MM1 and VV2, were diagnosed with sensitivities up to 95 and 97%, respectively. The performances of both procedures did not change in 168 patients with longitudinal MRI studies when the last examination was used.

Interpretation

This study provides the first practical algorithms for antemortem diagnosis of sCJD subtypes. MRI diagnosis of subtype is likely to be attainable at early disease stages to prognosticate clinical course and design future therapeutic trials. ANN NEUROL 2021;89:560–572

Report of a Case of Creutzfeldt-Jakob Disease With an Unusual Clinical Presentation

We describe the clinical features, neuropsychological tests, laboratory, electroencephalography (EEG), magnetic resonance imaging (MRI) and positron emission tomography (PET) findings of a 59-year-old woman who presented to our Centre for cognitive impairment since few months, with language disturbances, particularly anomia, dyscalculia, and memory loss. The clinical and neuropsychological features were non-specific and overlapping with those of other rapidly progressing neurodegenerative disorders. However, brain MRI played a pivotal role in the diagnosis, showing cortical diffusion restriction, particularly in the parietal lobes and posterior cingulum, with sparing of the perirolandic cortex, typical of Creutzfeldt-Jakob disease (CJD). Brain MRI abnormalities were visible since the first evaluation and remained stable at 2 and 6 weeks follow up. Basal ganglia and thalami were never involved. PET showed left lateralized reduced glucose metabolism, with partial overlap with MRI signal abnormalities. Despite MRI were strongly indicative of CJD, clinical, laboratory and EEG findings did not fulfill the diagnostic criteria for CJD which applied at the time of clinical assessment. Indeed, neither myoclonus, visual or cerebellar signs or akinetic mutism were present. Also, the characteristic periodic sharp wave complexes were absent at baseline EEG, and the CSF assay for 14–3–3 was negative. We, therefore, performed a real-time quaking-induced conversion (RT-QuIC) assay on a frozen sample of corticospinal fluid (CSF), which showed a positive result. RT-QuIC is a prion protein conversion assay that has shown high diagnostic sensitivity and specificity for the diagnosis of CJD. RT-QuIC has been recently incorporated in the National CJD Research and Surveillance Unit and Center for Disease Control and Prevention (CDC) diagnostic criteria for CJD. The fatal evolution of the disease brought the patient to death 13 months after symptoms onset. Pathology proved the diagnosis of sporadic CJD, subtype MM/MV 2C.