Detection of Prions

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications, trials & patents

Abstract

1) Currently, there is a need for diagnostic markers in Lewy body disorders (LBD) such as Parkinsons disease. -synuclein (Syn) RT-QuIC has emerged as a promising assay to detect misfolded Syn in clinically or neuropathologically established patients with various synucleinopathies. We used Syn RT-QuIC to analyze lumbar CSF in a clinical cohort from the Swedish BioFINDER study and postmortem ventricular CSF in a neuropathological cohort from the Arizona Study of Aging and Neurodegenerative Disorders/Brain and Body Donation Program (AZSAND/BBDP). The BioFINDER cohort included 64 PD/PDD, 15 MSA, 15 PSP, 47 controls and two controls who later converted to PD/DLB. The neuropathological cohort included 101 cases with different brain disorders, including LBD and controls. In the BioFINDER cohort Syn RT-QuIC identified LBD (i.e. PD, PDD and converters) vs. controls with a sensitivity of 95% and a specificity of 83%. The two controls that converted to LBD were Syn RT-QuIC positive. Within the AZSAND/BBDP cohort, Syn RT-QuIC identified neuropathologically verified "standard LBD" (i.e. PD, PD with AD and DLB; n=25) vs. no LB pathology (n=53) with high sensitivity (100%) and specificity (94%). Only 57% were Syn RT-QuIC positive in the subgroup with "non-standard" LBD (i.e., AD with Lewy Bodies not meeting criteria for DLB or PD, and incidental LBD, n=23). Furthermore, Syn RT-QuIC reliably identified cases with LB pathology in the cortex (97% sensitivity) vs. cases with no LBs or LBs present only in the olfactory bulb (93% specificity). However, the sensitivity was low, only 50%, for cases with LB pathology restricted to the brainstem or amygdala, not affecting the allocortex or neocortex. We concluded that Syn RT-QuIC of CSF samples is highly sensitive and specific for identifying cases with clinicopathologically-defined Lewy body disorders and shows a lower sensitivity for non-standard LBD or asymptomatic LBD or in cases with modest LB pathology not affecting the cortex 2) Alpha-synuclein seed amplification assays (Syn-SAAs) are promising diagnostic tools for Parkinsons disease (PD) and related synucleinopathies. They enable detection of seeding-competent alpha-synuclein aggregates in living patients and have shown high diagnostic accuracy in several PD and other synucleinopathy patient cohorts. However, there has been confusion about Syn-SAAs for their methodology, nomenclature, and relative accuracies when performed by various laboratories. We compared Syn-SAA results obtained from three independent laboratories to evaluate reproducibility across methodological variations. We utilized the Parkinsons Progression Markers Initiative (PPMI) cohort, with DATSCAN data available for comparison, since clinical diagnosis of early de novo PD is critical for neuroprotective trials, which often use dopamine transporter imaging to enrich their cohorts. Blinded cerebrospinal fluid (CSF) samples for a randomly selected subset of PPMI subjects (30 PD, 30 HC, and 20 SWEDD), from both baseline and year 3 collections for the PD and HC groups (140 total CSF samples) were analyzed in parallel by each lab according to their own established and optimized Syn-SAA protocols. The Syn-SAA results were remarkably similar across laboratories, displaying high diagnostic performance (sensitivity ranging from 86% to 96% and specificity from 93% to 100%). The assays were also concordant for samples with results that differed from clinical diagnosis, including 2 PD patients determined to be clinically inconsistent with PD at later time points. All three assays also detected 2 SWEDD subjects as Syn-SAA positive who later developed PD with abnormal DAT-SPECT. These multi-laboratory results confirm the reproducibility and value of Syn-SAA as diagnostic tools, illustrate reproducibility of the assay in expert hands, and suggest that Syn-SAA has potential to provide earlier diagnosis with comparable or superior accuracy to existing methods.