Chronological changes in MRI and CSF biochemical markers in Creutzfeldt-Jakob disease patients

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.

Establishment of a standard 14-3-3 protein assay of cerebrospinal fluid as a diagnostic tool for Creutzfeldt-Jakob disease

Periodic sharp wave complexes observed on an electroencephalographic recording and the presence of a 14-3-3 protein in the cerebrospinal fluid (CSF) are both included in the diagnostic criteria for the Creutzfeldt-Jakob disease (CJD) supplied by the World Health Organization; however, the presence or absence of the 14-3-3 protein in the CSF is sometimes difficult to discern on a western blot because of equivocal bands. The goal of this study was to establish a standard 14-3-3 protein assay and to determine the threshold level of a 14-3-3 protein that can be assayed by western blot. We searched for the most suitable isoform of the 14-3-3 protein to test for in protein assays, and the most sensitive antibody among four antibodies with an affinity for 14-3-3. We measured the levels of all 14-3-3 isoforms in 112 patients with CJD and in 100 patients with other diseases. We compared the performances of four different antibodies. We carried out a semi-quantitative analysis of γ-isoform levels using the LAS 3000 system, which was capable of producing a digital image from the luminescence on a western blot. We determined that the most suitable isoform of the 14-3-3 protein for conducting a standardized assay was the γ-isoform. Among the four commercially available antibodies for this protein, the most sensitive and specific was 18647 (IBL, Japan). We report the high repeatability of the detection of the 14-3-3 protein by this antibody to the γ-isoform, showing that western blot can be used for semi-quantitative analysis.

Elevated levels of tau protein in cerebrospinal fluid of patients with probable Creutzfeldt-Jakob disease

INTRODUCTION

A definitive diagnosis of Creutzfeldt-Jakob disease (CJD) can only be made by neuropathologic examination and demonstration of typical pathologic changes and the pathologic prion protein in central nervous tissues. This study investigated the diagnostic sensitivity and specificity of the microtubule-association protein tau in cerebrospinal fluid (CSF) from Chinese patients with sporadic CJD.

METHODS

Two hundred two CSF samples from clinically suspected patients with sporadic CJD were analyzed for tau protein by enzyme-linked immunosorbent assay and for the signal transduction regulatory protein 14-3-3 protein by immunoblot.

RESULTS

Remarkably increased levels of tau protein and increased incidence of 14-3-3 positivity were observed in probable CJD, when compared with possible CJD and others. With a threshold of 1400 pg/mL, tau determination showed a sensitivity of 90% and a specificity of 94% for the diagnosis of probable CJD. The combination of raised tau and positive 14-3-3 increased the specificity but slightly reduced the sensitivity. Statistical analysis indicated that the raised level of tau positively correlated with the presence of 14-3-3 in CSF but not with other main clinical features, eg, age, gender, clinical manifestations and sampling time.

CONCLUSIONS

These data suggest that Chinese patients with probable CJD have similar increased levels of tau in the CSF as in Caucasian patients. Measurement of CSF tau will be another potential technique for antemortem CJD diagnosis.