Alpha-synuclein seeds in olfactory mucosa and cerebrospinal fluid of patients with dementia with Lewy bodies

Abstract

In patients with suspected dementia with Lewy bodies the detection of the disease-associated α-synuclein in easily accessible tissues amenable to be collected using minimally invasive procedures, remains a major diagnostic challenge. This approach has the potential to take advantage of modern molecular assays for the diagnosis of α–synucleinopathy and, in turn, to optimize the recruitment and selection of patients in clinical trials, using drugs directed at counteracting α-synuclein aggregation. In this study, we explored the diagnostic accuracy of α-synuclein real-time quaking-induced conversion assay by testing olfactory mucosa and CSF in patients with a clinical diagnosis of probable (n = 32) or prodromal (n = 5) dementia with Lewy bodies or mixed degenerative dementia (dementia with Lewy bodies/Alzheimer’s disease) (n = 6). Thirty-eight patients with non-α-synuclein-related neurodegenerative and non-neurodegenerative disorders, including Alzheimer’s disease (n = 10), sporadic Creutzfeldt-Jakob disease (n = 10), progressive supranuclear palsy (n = 8), corticobasal syndrome (n = 1), fronto-temporal dementia (n = 3) and other neurological conditions (n = 6) were also included, as controls. All 81 patients underwent olfactory swabbing while CSF was obtained in 48 participants. At the initial blinded screening of olfactory mucosa samples, 38 out of 81 resulted positive while CSF was positive in 19 samples out of 48 analyzed. After unblinding of the results, 27 positive olfactory mucosa were assigned to patients with probable dementia with Lewy bodies, five with prodromal dementia with Lewy bodies and three to patients with mixed dementia, as opposed to three out 38 controls. Corresponding results of CSF testing disclosed 10 out 10 positive samples in patients with probable dementia with Lewy bodies and six out of six with mixed dementia, in addition to three out of 32 for controls. The accuracy among results of real-time quaking-induced conversion assays and clinical diagnoses was 86.4% in the case of olfactory mucosa and 93.8% for CSF. For the first time, we showed that α-synuclein real-time quaking induced conversion assay detects α-synuclein aggregates in olfactory mucosa of patients with dementia with Lewy bodies and with mixed dementia. Additionally, we provided preliminary evidence that the combined testing of olfactory mucosa and CSF raised the concordance with clinical diagnosis potentially to 100%. Our results suggest that nasal swabbing might be considered as a first line screening procedure in patients with a diagnosis of suspected dementia with Lewy bodies followed by CSF analysis, as a confirmatory test, when the result in the olfactory mucosa is incongruent with the initial clinical diagnosis.

High diagnostic performance of independent alpha-synuclein seed amplification assays for detection of early Parkinson’s disease

“…The in vitro generated αSyn fibrils are rich in β-sheets, enabling detection by the amyloid-specific dye Thioflavin T (ThT). αSyn-SAAs are capable of detecting and amplifying αSyn seeds from multiple biospecimens, including brain [11][12][13], cerebrospinal fluid (CSF) [6][7][8][9][10][13][14][15][16], skin [17][18][19], olfactory mucosa [20,21], submandibular gland [22], and gut [23]. Moreover, they have demonstrated accurate detection of αSyn seeds in clinically and pathologically validated cohorts of PD patients [6,7,9,10,13,17,18,24].…”

Seed amplification assays for diagnosing synucleinopathies: the issue of influencing factors

“…In different investigations, α-syn SAAs showed high sensitivity and specificity in differentiating PD from healthy controls and from non-α-syn-related parkinsonisms by using CSF as biological matrix [26][27][28][29][30][31][32][33]. Some other accessible peripheral matrices, such as olfactory mucosa [34,35] and skin biopsies [36][37][38], also produced very encouraging results. Considering the impact that SAAs might have when introduced in PD diagnostic workup, the analysis of the effects of experimental variables on the α-syn aggregation kinetics is a crucial step for both optimization and standardization of these experimental protocols.…”

Production of Recombinant Alpha-Synuclein: Still No Standardized Protocol in Sight

“…Some studies use home-made aSyn, others use protein from commercial vendors. While batch-to-batch variations in aSyn are recognized as a possible source of variation in the field [ 28 , 29 ], only a subset of studies reports systematic comparison of inter-batch variability [ 28 , 30 , 31 , 32 ]. In a recent study, SAAs were performed on control- and PD CSF by three independent groups in parallel according to their respective protocols [ 33 ].…”