Longitudinal α-Synuclein Seed Amplification Assay in Lewy Body Disorders

Overview

This longitudinal study of 196 Lewy body disease (LBD) patients demonstrates that α-synuclein seed amplification assay (SAA) kinetic parameters correlate with disease stage and progression. Notably, the number of positive replicates (Nrep) increased and the lag time (Lag) decreased over time, with baseline Nrep predicting dementia onset.

Background

Lewy body disease (LBD) is characterized by intraneuronal accumulation of misfolded α-synuclein, primarily manifesting as Parkinson’s disease (PD) or dementia with Lewy bodies. α-Synuclein seed amplification assays (SAA) have emerged as highly accurate ante-mortem biomarkers for LBD, but traditionally yield binary results. Recent evidence suggests that quantitative kinetic parameters from SAA may reflect pathology burden and predict clinical progression. Longitudinal studies are essential to validate these parameters as biomarkers for disease monitoring and therapeutic response.

Data Highlights

Key Findings

• 196 individuals with α-syn seeding activity were studied longitudinally, including 26 who converted from negative to positive SAA during follow-up.
• LBD-converters had significantly lower Nrep and longer Lag at baseline compared to those positive from the first sample.
• Nrep increased longitudinally across the cohort, including asymptomatic LBD and PD without dementia subgroups.
• Lag time decreased longitudinally in asymptomatic LBD participants, indicating increasing seed amplification efficiency.
• Higher baseline Nrep was associated with increased risk of developing dementia in the whole cohort and PD subgroup.
• Changes in Lag over time were inversely associated with dementia onset, supporting its role as a progression biomarker.

Clinical Implications

Quantitative α-syn SAA kinetic parameters, specifically Nrep and Lag, provide valuable biomarkers for staging Lewy body disease and predicting dementia onset. Monitoring these parameters longitudinally can aid in assessing disease progression and may serve as objective outcome measures in clinical trials of disease-modifying therapies. Early identification of LBD converters through SAA kinetics could facilitate timely intervention.

Conclusion

This study validates α-synuclein SAA kinetic parameters as dynamic biomarkers reflecting Lewy body pathology progression and clinical outcomes. Their longitudinal assessment holds promise for improving diagnosis, prognosis, and therapeutic monitoring in LBD.

References

1. Concha-Marambio et al. 2023 -- Longitudinal Analysis of α-Synuclein Seed Amplification Assay Outcomes in the Spectrum of Lewy Body Disorders