PMCA optimization for the detection of prions in urine of patients with Fatal Familial Insomnia

Fatal Familial Insomnia (FFI) is a rare prion disease caused by a mutation in the PRNP gene, resulting in a substitution of asparagine with aspartic acid (D178N). Genetic testing can identify mutation carriers, but biomarkers capable of predicting disease onset are still lacking. This study aims at developing a new protein misfolding cyclic amplification (PMCA) protocol to detect prions (PrPSc) in urine and blood samples of FFI mutation carriers collected at different disease stages (preclinical and clinical). To this aim, urine samples longitudinally collected from D178N mutation carriers at preclinical (n=fourteen) or clinical (n=four) stage and controls (n=twenty) were tested, as well as one plasma sample collected from a patient at terminal disease stage. PMCA enabled the detection of prions in the urine of ten mutation carriers, two symptomatic and eight asymptomatic at the time of collection. The PMCA analysis of the plasma also yielded a positive result. These findings suggest that PMCA may be capable of detecting prions prior to the onset of symptoms; however, it remains unclear whether—and to what extent—this could serve as a reliable biomarker for disease initiation. Further evaluation of the patients’ clinical parameters (e.g., kidney functions/dysfunctions) could help clarify why prions were detectable in the urine of some asymptomatic carriers but not others, and provide insights into the reliability and timing of prion detection.