Amplification techniques and diagnosis of prion diseases.

Protein misfolding cyclic amplification assay (PMCA) and real-time quaking-induced conversion (RT-QuIC) are two amplification techniques based on the ability of PrPsc to induce a conformational change in PrP allowing the detection of minute amounts of PrPsc in body fluids or tissues. PMCA and RT-QuIC have different ability to amplify PrPsc from sporadic, variant and genetic forms of Creutzfeldt-Jakob disease (CJD). PMCA readily amplifies PrPsc from variant CJD (vCJD) tissue while RT-QuIC easily amplifies PrPsc from sporadic CJD (sCJD) patient tissues. In terms of diagnosis, this implies the possibility of distinguishing vCJD from sCJD and explains the wider use of RT-QuIC given the respective frequencies of vCJD and sCJD. The sensitivity values of RT-QuIC for the diagnosis of sCJD are comparable or higher than those of the other tests (EEG, MRI, detection of 14-3-3 or tau proteins in cerebrospinal fluid) but with a specificity close to 100%. These new diagnostic methods could also be useful for the diagnosis of other neurodegenerative diseases.

14-3-3 protein cerebrospinal fluid detection in human growth hormone-treated Creutzfeldt-Jakob disease patients.

The usefulness of the detection of 14-3-3 protein in the cerebrospinal fluid (CSF) in the diagnosis of Creutzfeldt-Jakob disease transmitted from human growth hormone was evaluated in 20 French patients. The 14-3-3 protein was rarely detectable within the first 3 months of the disease but always positive after 7 months associated with the aggravation of the disease and the occurrence of dementia. 14-3-3 detection was not predictive of the survival time of the patients. The genotype at PRNP codon 129 could influence the timing of appearance of the 14-3-3 protein in the CSF.