Clinical Use of Improved Diagnostic Testing for Detection of Prion Disease

Personalized brain MRI revealed distinct functional and anatomical disruptions in Creutzfeldt-Jakob disease and Alzheimer's disease

AIMS

Creutzfeldt-Jakob disease (CJD) is a lethal neurodegenerative disorder, which leads to a rapidly progressive dementia. This study aimed to examine the cortical alterations in CJD, changes in these brain characteristics over time, and the differences between CJD and Alzheimer's disease (AD) that show similar clinical manifestations.

METHODS

To obtain reliable, subject-specific functional measures, we acquired 24 min of resting-state fMRI data from each subject. We applied an individual-based approach to characterize the functional brain organization of 10 patients with CJD, 8 matched patients with AD, and 8 normal controls. We measured cortical atrophy as well as disruption in resting-state functional connectivity (rsFC) and then investigated longitudinal brain changes in a subset of CJD patients.

RESULTS

CJD was associated with widespread cortical thinning and weakened rsFC. Compared with AD, CJD showed distinct atrophy patterns and greater disruptions in rsFC. Moreover, the longitudinal data demonstrated that the progressive cortical thinning and disruption in rsFC mainly affected the association rather than the primary cortex in CJD.

CONCLUSIONS

CJD shows unique anatomical and functional disruptions in the cerebral cortex, distinct from AD. Rapid progression of CJD affects both the cortical thickness and rsFC in the association cortex.

A case report of fatal familial insomnia with cerebrospinal fluid leukocytosis during the COVID-19 epidemic and review of the literature

Fatal familial insomnia (FFI) is a rare autosomal dominant genetic neurodegenerative disease. Generally, FFI patients will develop rapidly progressive dementia, sleep disturbance, autonomic dysfunction, and so on. Cerebrospinal fluid examination of FFI patients normally shows no obvious abnormalities. Here, we report a young male patient who was diagnosed with FFI during the COVID-19 epidemic. Clinical symptoms include psychobehavioral abnormality, cognitive decline, sleep disturbance, and autonomic dysfunction. No abnormalities were found in routine examinations after admission. However, the number of white blood cells in the cerebrospinal fluid increased. Though the patient was treated with anti-infection and immunotherapy, the symptoms were not relieved. A lumbar puncture was performed again, and it was found that the total Tau protein in the cerebrospinal fluid was elevated, and PET results showed that brain metabolism decreased. Finally, a genetic test was used to confirm the diagnosis of FFI. This case suggests that patients with FFI may also have elevated white blood cells in cerebrospinal fluid and timely detection of Tau protein in cerebrospinal fluid is helpful for early identification of FFI. And precise diagnosis relies on genetic testing.

Pick's Disease, Seeding an Answer to the Clinical Diagnosis Conundrum

Pick's disease (PiD) is a devastating neurodegenerative disease that is characterized by dementia, frontotemporal lobar degeneration, and the aggregation of 3R tau in pathognomonic inclusions known as Pick bodies. The term PiD has adopted many meanings since its conception in 1926, but it is currently used as a strictly neuropathological term, since PiD patients cannot be diagnosed during life. Due to its rarity, PiD remains significantly understudied, and subsequently, the etiology and pathomechanisms of the disease remain to be elucidated. The study of PiD and the preferential 3R tau accumulation that is unique to PiD is imperative in order to expand the current understanding of the disease and inform future studies and therapeutic development, since the lack of intervention strategies for tauopathies remains an unmet need. Yet, the lack of an antemortem diagnostic test for the disease has further complicated the study of PiD. The development of a clinical diagnostic assay for PiD will be a vital step in the study of the disease that will greatly contribute to therapeutic research, clinical trial design and patient recruitment and ultimately improve patient outcomes. Seed aggregation assays have shown great promise for becoming ante mortem clinical diagnostic tools for many proteinopathies, including tauopathies. Future research on adapting and optimizing current seed aggregation assays to successfully detect 3R tau pathogenic forms from PiD samples will be critical in establishing a 3R tau specific seed aggregation assay that can be used for clinical diagnosis and treatment evaluation.

Human prion diseases and the prion protein - what is the current state of knowledge?

Prion diseases and the prion protein are only partially understood so far in many aspects. This explains the continued research on this topic, calling for an overview on the current state of knowledge. The main objective of the present review article is to provide a comprehensive up-to-date presentation of all major features of human prion diseases bridging the gap between basic research and clinical aspects. Starting with the prion protein, current insights concerning its physiological functions and the process of pathological conversion will be highlighted. Diagnostic, molecular, and clinical aspects of all human prion diseases will be discussed, including information concerning rare diseases like prion-associated amyloidoses and Huntington disease-like 1, as well as the question about a potential human threat due to the transmission of prions from prion diseases of other species such as chronic wasting disease. Finally, recent attempts to develop future therapeutic strategies will be addressed.

Genetic aspects of human prion diseases

Human prion diseases are rapidly progressive and fatal neurodegenerative conditions caused by a disease-causing isoform of the native prion protein. The prion protein gene (PRNP) encodes for the cellular prion protein, which is the biological substrate for prion disease transmission and neurotoxicity. Human prion diseases have three etiologies: sporadic, genetic, and acquired. PRNP polymorphisms and pathogenic variants play a large role in the frequency, age at onset, and clinicopathologic phenotype of prion diseases. Genetic prion diseases will be covered in detail and information necessary for clinical care, predictive genetic testing, and genetic counseling will be reviewed. Because the prion protein is necessary for transmission and neurotoxicity, many experimental treatments targeting its production are being investigated and hold potential promise as a disease modifying treatment for all forms of prion disease, including asymptomatic mutation carriers. This article will review genetic aspects of human prion disease and their influence on epidemiology, clinicopathologic phenotype, diagnostics, clinical management, and potential treatment approaches.

A field-deployable diagnostic assay for the visual detection of misfolded prions

Diagnostic tools for the detection of protein-misfolding diseases (i.e., proteopathies) are limited. Gold nanoparticles (AuNPs) facilitate sensitive diagnostic techniques via visual color change for the identification of a variety of targets. In parallel, recently developed quaking-induced conversion (QuIC) assays leverage protein-amplification and fluorescent signaling for the accurate detection of misfolded proteins. Here, we combine AuNP and QuIC technologies for the visual detection of amplified misfolded prion proteins from tissues of wild white-tailed deer infected with chronic wasting disease (CWD), a prion disease of cervids. Our newly developed assay, MN-QuIC, enables both naked-eye and light-absorbance measurements for detection of misfolded prions. MN-QuIC leverages basic laboratory equipment that is cost-effective and portable, thus facilitating real-time prion diagnostics across a variety of settings. In addition to laboratory-based tests, we deployed to a rural field-station in southeastern Minnesota and tested for CWD on site. We successfully demonstrated that MN-QuIC is functional in a non-traditional laboratory setting by performing a blinded analysis in the field and correctly identifying all CWD positive and CWD not-detected deer at the field site in 24 h, thus documenting the portability of the assay. White-tailed deer tissues used to validate MN-QuIC included medial retropharyngeal lymph nodes, parotid lymph nodes, and palatine tonsils. Importantly, all of the white-tailed deer (n = 63) were independently tested using ELISA, IHC, and/or RT-QuIC technologies and results secured with MN-QuIC were 95.7% and 100% consistent with these tests for positive and non-detected animals, respectively. We hypothesize that electrostatic forces help govern the AuNP/prion interactions and conclude that MN-QuIC has great potential for sensitive, field-deployable diagnostics for CWD, with future potential diagnostic applications for a variety of proteopathies.

Genetic counseling for prion disease: Updates and best practices

Prion disease is a rare, fatal, and often rapidly progressive neurodegenerative disease. Ten to fifteen percent of cases are caused by autosomal dominant gain-of-function variants in the prion protein gene, PRNP. Rarity and phenotypic variability complicate diagnosis, often obscuring family history and leaving families unprepared for the genetic implications of an index case. Several recent developments inspire this update in best practices for prion disease genetic counseling. A new prion-detection assay has transformed symptomatic diagnosis. Meanwhile, penetrance, age of onset, and duration of illness have been systematically characterized across PRNP variants in a global cohort. Clinically, the traditional genotype-phenotype correlation has weakened over time, and the term genetic prion disease may now better serve providers than the historical subtypes Creutzfeldt-Jakob disease, fatal familial insomnia, and Gerstmann-Sträussler-Scheinker disease. Finally, in the age of genetically targeted therapies, clinical trials for prion disease are being envisaged, and healthy at-risk individuals may be best positioned to benefit. Such individuals need to be able to access clinical services for genetic counseling and testing. Thus, this update on the genetics of prion disease and best practices for genetic counseling for this disease aims to provide the information needed to expand genetic counseling services.

Atypical Case of VV1 Creutzfeldt–Jakob Disease Subtype: Case Report

Creutzfeldt–Jakob disease (CJD) is a rare form of rapidly progressive, neurodegenerative disease that results from the misfolding and accumulation of an aberrant, disease-associated prion protein (PrPD). CJD affects 1–1.5 cases per million per year with the sporadic-type accounting for an estimated 85% of these cases. Sporadic CJD (sCJD) is further subdivided into five subtypes based on genetic polymorphisms; the rarest subtype, sCJDVV1, occurs at a rate of 1 case per one-hundredth million population per year. Clinical characteristics of the sCJDVV1 subtype have been reported to show, early age of onset (44 years), average disease duration of 21 months, absent PSWCs on electroencephalography (EEG), and MRI hyperintensities in the cerebral cortex with usual negative signal in the basal ganglia or thalamus. We present a case of the sCJDVV1 subtype with uncommon features. Contrary to current data on sCJDVV1, our patient presented with an unusual age at onset (61 years) and longer disease duration (32 months). The highly sensitive and specific real-time quaking-induced conversion (RT-QuIC) assay was negative. Presenting clinical symptoms included paranoid thoughts and agitation, rapidly progressive memory decline, prosopagnosia, and late development of myoclonus and mutism. Other findings showed positive antithyroid peroxidase antibodies (anti-TPO), and absent PSWCs on EEG. High-dose steroid therapy treatment was administered based on positive anti-TPO findings, which failed to elicit any improvement and the patient continued to decline. To our knowledge, only four cases with the sCJDVV1 subtype, including our patient, have been reported to have a negative result on RT-QuIC. This may suggest varied sensitivity across sCJD subtypes. However, given the rarity of our patient's subtype, and the relatively novel RT-QuIC, current data are based on a small number of cases and larger cohorts of confirmed VV1 cases with RT-QuIC testing need to be reported.

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.

The 14-3-3 Protein Family and Schizophrenia

Schizophrenia is a debilitating mental disorder that affects approximately 1% of the world population, yet the disorder is not very well understood. The genetics of schizophrenia is very heterogenous, making it hard to pinpoint specific alterations that may cause the disorder. However, there is growing evidence from human studies suggesting a link between alterations in the 14-3-3 family and schizophrenia. The 14-3-3 proteins are abundantly expressed in the brain and are involved in many important cellular processes. Knockout of 14-3-3 proteins in mice has been shown to cause molecular, structural, and behavioral alterations associated with schizophrenia. Thus, 14-3-3 animal models allow for further exploration of the relationship between 14-3-3 and schizophrenia as well as the study of schizophrenia pathology. This review considers evidence from both human and animal model studies that implicate the 14-3-3 family in schizophrenia. In addition, possible mechanisms by which alterations in 14-3-3 proteins may contribute to schizophrenia-like phenotypes such as dopaminergic, glutamatergic, and cytoskeletal dysregulations are discussed.

The First Sporadic Creutzfeldt-Jakob Disease Case with a Rare Molecular Subtype VV1 and 1-Octapeptide Repeat Deletion in PRNP

In the present manuscript, we report the clinical presentation and challenging diagnostic work-up of a sporadic Creutzfeldt–Jakob disease patient with confirmed VV1 subtype and heterozygous 1-octapeptide repeat deletion in the prion protein gene. The described patient was a 58-year-old woman. Interestingly, most of the reported patients with the VV1 subtype to date are men with an average age of 44 years at disease onset. The patient was observed clinically from symptoms onset until her death 22 months later. This report describes the patient’s insidious clinical evolution and the paraclinical examinations and pathology reports gathered at different time points of disease progression. Unfortunately, the absence of typical clinical and paraclinical features of classic sporadic Creutzfeldt–Jakob disease made the brain biopsy surgery necessary. This case report illustrates the diagnostic difficulties posed by the phenotypic heterogeneity of sporadic Creutzfeldt–Jakob disease and urges clinicians to consider this diagnosis even in patients who do not fulfil the typical clinical disease criteria. Furthermore, it highlights the need for real-time quaking-induced conversion method adaptation for detection of rare sporadic Creutzfeldt–Jakob disease subtypes with certain prion protein gene variants.