This study aims to investigate the therapeutic potential of engineered exosomes in anti-NMDAR encephalitis.

Currently, there is a lack of biomarkers to monitor treatment response or guide therapeutic adjustments in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, and management of refractory cases remains a major clinical challenge. Exosomes, serving as intercellular signaling carriers, cross the blood-brain barrier and reflect central nervous system (CNS) status. Moreover, miRNA-loaded exosomes can markedly ameliorate disease phenotypes, offering novel research directions for anti-NMDAR encephalitis. Additionally, progressively optimized animal models have provided strong support for further exploration of the disease.

Plasma exosomes were isolated from acute-phase and stable-phase anti-NMDAR encephalitis patients, as well as healthy controls. Next-generation sequencing profiled exosomal miRNAs, and their expression levels were correlated with clinical severity to nominate therapeutic candidates. Furthermore, we established mice models of anti-NMDAR encephalitis through active immunization and validated the reliability and stability using behavioral assessments, electroencephalogram recording, serum anti-NMDAR titres and brain-section immunofluorescence. Finally, we modified exosomes to load miRNAs and conjugated them with RVG targeting peptides to enhance CNS delivery, and their therapeutic efficacy was evaluated in the validated model.

We found that the expression levels of exosomal miR-432-5p, miR-4433b-5p, and miR-599 exhibited significant down-regulated in anti-NMDAR encephalitis patients versus healthy controls, with the lowest levels observed in the acute-phase, and that miR-432-5p and miR-4433b-5p levels were negatively correlated with the clinical severity. Moreover, we successfully established mice models of anti-NMDAR encephalitis. Exosomes modified with miR-432-5p mimics demonstrated therapeutic effects in the anti-NMDAR encephalitis mice models, reversing deficits in motor coordination, anxiety-like behavior, and spatial memory.

This study identified exosomal miR-432-5p, miR-4433b-5p, and miR-599 as severity indicators for anti-NMDAR encephalitis. In validated mice models, RVG-targeted exosomes delivering miR-432-5p mimics markedly attenuated disease signs, providing pre-clinical proof of concept for exosome based therapy.