PLGA Nanoparticle-based Anti-TLR2 scFv Gene Delivery for the Treatment of Alzheimer's Disease

In Alzheimer's disease (AD), persistent microglial neuroinflammation and the poor brain exposure and durability of current therapies underscore the need for new, long-acting treatments. We developed a non-viral gene therapy that suppresses microglial Toll-like receptor 2 (TLR2) signaling using poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with a plasmid encoding the anti-TLR2 single-chain variable fragment (scFv33). Following intra-cisterna magna delivery, PLGA NPs exhibited microglia-biased uptake and enabled brain-wide transgene expression in mice. In 5xFAD mice, a single administration of scFv33 NPs improved recognition memory in the novel object recognition (NOR) assay, outperforming 8 weeks of weekly recombinant scFv33-Fc dosing. Histology showed selective reduction of small hippocampal Aβ plaques and a shift toward a ramified microglial morphology, indicative of reduced activation. In primary neuron-microglia co-culture, scFv33 reduced microglial hypertrophy, restored process complexity, and enhanced Aβ phagocytosis. Together, these data indicate that sustained, local expression of an anti-TLR2 scFv via a clinically translatable PLGA platform recalibrates microglial state and preferentially limits early-stage plaque accumulation, yielding cognitive benefit after a single dose.