(562h) Modified AAV Vectors with Phosphoserine-Containing Zwitterionic Peptides for Enhanced Cell-Specific Transduction and Immunosuppressive Capacities

Although adeno-associated viruses (AAVs) are considered low immunogenic and safe for gene delivery, the immunogenicity of capsids still impedes the re-administration of AAVs. The current method using poly(ethylene glycol)(PEG) to shield AAV from being recognized by neutralizing antibodies efficiently reduces humoral immunity but is not effective against cell-mediated immune responses. Here, we modify the AAV surface with phosphoserine-containing zwitterionic peptides to induce AAV-specific immune tolerance to facilitate multiple AAV injections. The phosphoserine moiety is known for specific binding to the receptors on monocytes and induction of immunosuppressive environment. Moreover, our zwitterionic design of the peptide balances the excessive anionic charges of the phosphoserine moiety to maintain the transduction efficiency of the modified AAV. After optimization of the chemical structure, we simplify the conjugation process into a one-step reaction which minimizes virus loss and sustained virus activity. Moreover, we evaluate the binding specificity of the phosphoserine moieties on the peptides to their receptor via a surface plasma resonance (SPR) assay. We further demonstrate the similar transduction and uptake efficiency of modified AAV compared to wildtype AAV in different cell lines and in vivo at a single injection to the animal. Finally, in the setting of multiple injections, we reveal that the modified AAV has better transduction efficacy and induced lower antibody titers than the wild type. Overall, this immunosuppressive zwitterionic peptide presents a new platform for engineering AAV vectors to enable re-administrations and increased delivery efficiency.