Detection of pathological prion protein by RT-QuIC analysis of cerebrospinal fluid and olfactory neuroepithelium of patients with sporadic Creutzfeldt-Jakob disease

ABSTRACT BACKGROUND: Definitive diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) in living patients remains a challenge. Real time quaking-induced conversion (RT-QuIC) testing of cerebrospinal fluid (CSF) has allowed identification of sCJD patients with 80-90% sensitivity. However, because CJD is transmissible, untreatable and fatal, it is important to eliminate missed diagnoses. Previous work identified abnormal prion protein (PrP) in olfactory neuroepithelium of sCJD patients, prompting us to investigate whether RT-QuIC analysis of easily accessible nasal brushings might improve sCJD diagnosis. METHODS: We tested olfactory neuroepithelium brushings from sCJD and non-CJD patients using RT-QuIC, which is an ultrasensitive, multi-well plate-based fluorescence assay involving prion-seeded polymerization of recombinant PrP into amyloid fibrils. RESULTS: We observed strong positive RT-QuIC reactions seeded with nasal brushings from 7 of 7 probable sCJD patients, but none of 11 negative controls, providing 100% sensitivity and 100% specificity. By comparison, 6 out of 7 CSF samples from the same group of sCJD patients was RT-QuIC-positive, giving 86% sensitivity. Quantitative RT-QuIC showed that olfactory brushings contained ~105-107 prion seeds. CONCLUSIONS: Nasal brushing-based RT-QuIC may markedly facilitate and strengthen diagnosis of sCJD. Moreover, the high levels of prion seeding activity found in these samples raises concerns about transmissible sCJD prion shedding from olfactory mucosa.