Strain-Specific Prion Seeding Dynamics and Proteomic Changes in Human CJD: Toward Early Diagnosis

Introduction:
Creutzfeldt-Jakob disease (CJD) is a fatal neurodegenerative disorder caused by misfolded prion proteins. Early diagnosis remains a major challenge due to the subtle and heterogeneous onset of symptoms across different CJD subtypes.

Objectives:
This study aimed to characterize the early-stage prion seeding kinetics and molecular signatures of distinct human CJD strains to identify potential early diagnostic biomarkers.

Methods:
Using the real-time quaking-induced conversion (RT-QuIC) assay, we analyzed prion seeding activity in brain samples from transgenic mice (tg340, tg361, tg650) inoculated with MM1 or VV2 human CJD strains. A total of 188 cortical samples from pre-clinical and clinical disease stages were evaluated. Proteomic profiling was performed using SWATH-MS to identify differentially expressed proteins.

Results/Discussion:
RT-QuIC revealed region- and strain-specific differences in prion seeding kinetics, with MM1-infected tg340 mice showing longer lag phases (~24.5 h), while VV2-infected tg361 mice exhibited minimal seeding at the preclinical stage. Proteomic analysis identified 500 and 682 differentially expressed proteins in MM1 and VV2 models, respectively. Early-stage biomarkers included Gnl1, Stxbp1, Nefh (MM1) and Calb2, Dnaja1, Syn2 (VV2). Functional pathways revealed subtype-specific responses: MM1 engaged metabolic and vesicular pathways, while VV2 showed early calcium signaling disruption and cytoskeletal instability.

Conclusion:
This integrative kinetic and proteomic study reveals strain-specific early molecular changes in CJD, highlighting promising biomarker candidates for early diagnosis and enhancing our understanding of prion disease mechanisms.