Intramuscular delivery of a single chain antibody gene reduces brain Aβ burden in a mouse model of Alzheimer's disease

Anti-β-amyloid (Aβ) immunotherapy has been well documented to effectively elicit amyloid plaque clearance and slow cognitive decline in experimental and clinical studies. However, anti-Aβ immunotherapy was associated with detrimental effects of brain inflammation and microhemorrhage, presumably induced by T-cell-mediated and/or Fc-mediated inflammatory responses. In the present study, a single chain antibody (scFv) against Aβ could effectively inhibit the aggregation of Aβ and promote the disaggregation of preformed Aβ fibrils. The recombined adeno-associated virus vectors carrying the scFv gene were produced to delivery the scFv gene. Hippocampus delivery of the scFv gene was effective in reducing the amyloid plaque in the hippocampus of an Alzheimer's disease (AD) mouse model. Further studies demonstrated that intramuscular delivery of the scFv gene was as effective as intracranial delivery in reducing the total Aβ level in the brain with a concomitant elevated Aβ level in serum. No enhanced microglial activation, discernable T lymphocyte infiltration, and increased microhemorrhage were found after intracranial and intramuscular delivery of the scFv gene. Our results suggest that intramuscular delivery of the scFv gene would be a novel peripheral noninflammatory immunological modality targeting Aβ clearance and be promising in future drug development for the prevention and treatment of AD.