Abstract
Alzheimer's disease (AD) is the most common neurodegenerative disorder, yet effective preventive or therapeutic strategies remain limited. A hallmark of AD pathology is the accumulation of insoluble amyloid-β (Aβ) aggregates, which are targeted by recent antibody-based therapies. Conversely, soluble amyloid precursor protein-alpha (sAPPα), a non-amyloidogenic cleavage product of APP, possesses neuroprotective, neurotrophic, and synaptogenic properties, and the ability to enhance memory. This study evaluated the therapeutic efficacy of adeno-associated virus variant PHP.eB (AAV-PHP.eB) encoding human sAPPα in the APPswe/PS1dE9 transgenic mouse model of AD. Six-month-old female wild-type and transgenic mice received a single intravenous injection via the tail vein. Three months post-injection, brain tissue was harvested for electrophysiological and histological analyses. The treatment significantly increased cortical sAPPα levels and fully restored hippocampal long-term potentiation (LTP) in transgenic mice. Post-mortem analyses revealed a substantial reduction in amyloid plaque burden in both the hippocampus and cortex, with minimal plaque progression from the time of injection. However, no significant changes were observed in astrocytic (GFAP) or microglial (Iba-1) coverage, nor in soluble and insoluble Aβ1-40 or Aβ1-42 levels. These findings suggest that systemic AAV-PHP.eB-mediated sAPPα delivery can ameliorate synaptic dysfunction and aggregated amyloid pathology in AD, highlighting its potential as a therapeutic strategy.