ApoE-directed CpG nano-immunoadjuvant ameliorates Alzheimer's-like pathology in mice

Toll-like receptor 9 (TLR9), expressed in both microglia and neurons of the CNS, represents a promising therapeutic target for Alzheimer's disease (AD). While either microglial or neuronal TLR9 activation exerts neuroprotective effects that ameliorate AD pathology and preserve cognitive function, CpG oligodeoxynucleotides (ODNs), the synthetic agonists, cannot cross the blood-brain barrier (BBB). To overcome this, we developed tNCpG, an apolipoprotein E (ApoE)-functionalized polymersome nanocarrier for brain-targeted delivery of CpG ODNs. APP/PS1 transgenic mice, which overexpress human mutant APP/PS1 and are widely used in AD mouse models for preclinical studies, were administered tNCpG intravenously biweekly for 3 months, starting at 4 months of age. tNCpG achieved efficient brain delivery while specifically targeting microglia and neurons. tNCpG treatment enhanced microglial recruitment to and phagocytosis of Aβ plaques, suppressed Aβ production while promoting its degradation, and improved BBB integrity and Aβ efflux. Collectively, these effects significantly reduced cerebral Aβ burden, neuroinflammation, and neurodegeneration, leading to the rescue of cognitive deficits. Our study establishes targeted TLR9 activation via tNCpG as a disease-modifying therapeutic strategy for AD.