Precision glycoengineered AAV capsids enhance hepatocyte targeting and attenuated immune activation for liver-directed gene therapy

Adeno-associated virus (AAV) vectors are a promising platform for liver-directed gene therapy, yet their clinical translation is hindered by limited cell-type specificity and dose-dependent immune responses. Here, we report a chemical biology strategy for programmable, site-defined glycan installation on intact AAV capsids via genetic code expansion and biorthogonal chemistry. This approach enables precise conjugation of triantennary N-acetylgalactosamine (GN₃), a model ligand of the hepatocyte-specific receptor ASGPR1 for proof of concept, to AAV2, AAV8, and AAV-DJ capsids, overcoming the stochastic nature of conventional modifications. The resulting GN₃-modified AAVs (AAV-GN3) exhibit enhanced hepatocyte-specific transduction, reduced susceptibility to pre-existing neutralizing antibodies, and attenuated innate and adaptive immune activation. Importantly, AAV-GN3 mediates hepatocyte-restricted FOXA2 and FIX expression, alleviating liver fibrosis and hemophilia in mice, and its properties of weakening immune activation suggest potential for AAV-seropositive patients or repeated administration scenarios. These results establish a modular, precise platform for AAV glycoengineering, advancing the development of safer and more effective liver-targeted gene therapies.