Exosome-Modified AAV Gene Therapy Attenuates Autoimmune Hepatitis via Enhanced Regulatory T Cell Targeting and Immune Modulation.

Autoimmune hepatitis (AIH) is a chronic liver disorder driven by immune dysregulation, marked by reduced regulatory T cells (Tregs) and unchecked inflammation. Current therapies lack specificity and efficacy, necessitating novel approaches. This study explores gene therapy using exosome-associated adeno-associated virus (exo-AAV) to deliver the Foxp3 gene, aiming to restore Treg-mediated immune tolerance in AIH. We engineered exosomes expressing the CD4-targeting antibody on their surface, encapsulating AAV6/Foxp3, to enhance lymphoid cell specificity. In a ConA-induced murine AIH model, engineered exo-AAV administration significantly increased hepatic Treg proportions while reducing Th17 cells and inflammatory cytokines (IFN-γ, TNF-α, IL-6), compared to control groups (unmodified exo-AAV or empty exosomes). Liver histopathology and serum ALT levels also improved in engineered exo-AAV treated mice. Mechanistically, engineered exo-AAV demonstrated superior targeting via CD4 binding, validated by immunofluorescence and nanoparticle tracking. Despite transient reductions in splenic Tregs, localized hepatic immune modulation underscored exo-AAV's efficacy. These findings highlight engineered exo-AAV as a promising strategy for precision gene therapy in AIH, overcoming limitations of traditional AAV delivery by enhancing lymphocyte-specific transduction and immune balance restoration. This approach presents a novel therapeutic avenue for systemic autoimmune diseases reliant on Treg reinforcement.