Chimeric Phagocytic Receptors (CPR) to target Alzheimer’s disease pathology

Abstract

AbstractBackgroundBased on the premise that protein aggregation and accumulation in AD and many other neurodegenerative disorders is a key, causal, pathologic event, therapeutic strategies need to focus on i) prevention of aggregate formation ii) enhancement of clearance of the aggregate or iii) neutralization of “toxic” signaling by the aggregate. Enhancing clearance of the target protein via phagocytic mechanisms is the most direct way to test the hypothesis that enhancing clearance will be beneficial. We cloned two novel chimeric phagocytic receptors (CPRs), fused to a previously characterized anti‐Abeta scFv. The present work aims to explore whether astrocyte expressed CPRs targeting Aβ enhance phagocyte clearance and alter the target pathology, when delivered into the brain of the Alzheimer’s disease mouse model, CRND8, as a prevention paradigm, before the pathology develops, or after amyloid aggregation already occurred.MethodAnti‐Abeta recombinant scFvs fused to two most promising CPRs were packaged in AAV under astrocytic GFAP promoter and delivered into the brains of newborn CRND8 mice (prevention paradigm) as well as older mice with preexisting pathology (treatment paradigm). Amyloid burden and Aβ levels in the soluble, SDS soluble and SDS‐insoluble, Formic Acid soluble fractions, as well as the state of astrocytosis and astrogliosis were compared between various cohorts. Backbone of the CPR without the scFv as well as pAAV‐EGFP served as controls.ResultInitially we evaluated expression, amyloid burden and GFAP and IBA staining in mice that were injected with 2 CPRs, pAAV‐MRC1‐GFAP‐scFv9, pAAV‐FCRG‐GFAP‐scFv9, as well as pAAV‐MRC1‐BB (backbone control) and pAAV‐EGFP control. Amyloid staining revealed a significant clearance of amyloid staining in the area around the injection site, which overlapped with the expression of CPR. Additionally, expression of CPRs resulted in increased astrocytes and microglia burden.ConclusionThese results suggest a significant amyloid alteration by chosen CPRs. Future studies will optimize brain delivery as well as determine therapeutic potential of CPRs following transplantation of the CPR expressing microglia/monocytes into the brain mice with preexisting pathology.