The 2.8 Å Electron Microscopy Structure of Adeno-Associated Virus-DJ Bound by a Heparinoid Pentasaccharide

• Published in: Molecular therapy. Methods & clinical development 2017-06, Vol.5 (C), p.1-12
• Main Authors: Xie, Qing, Spear, John M, Noble, Alex J, Sousa, Duncan R, Meyer, Nancy L, Davulcu, Omar, Zhang, Fuming, Linhardt, Robert J, Stagg, Scott M, Chapman, Michael S
• Format: Article
• Language: English
• Subjects: AAV; adeno-associated virus; Amino acids; attachment; Binding sites; Cell surface; Conflicts of interest; Directed evolution; Electron microscopy; Gene therapy; Genomes; glycan; Heparan sulfate; Heparin; Microscopy; Original; Proteins; receptor; Serotypes; Software; structure; Symmetry; vector
• ISSN: 2329-0501; 2329-0501
• DOI: 10.1016/j.omtm.2017.02.004

Atomic structures of adeno-associated virus (AAV)-DJ, alone and in complex with fondaparinux, have been determined by cryoelectron microscopy at 3 Å resolution. The gene therapy vector, AAV-DJ, is a hybrid of natural serotypes that was previously derived by directed evolution, selecting for hepatocyte entry and resistance to neutralization by human serum. The structure of AAV-DJ differs from that of parental serotypes in two regions where neutralizing antibodies bind, so immune escape appears to have been the primary driver of AAV-DJ's directed evolution. Fondaparinux is an analog of cell surface heparan sulfate to which several AAVs bind during entry. Fondaparinux interacts with viral arginines at a known heparin binding site, without the large conformational changes whose presence was controversial in low-resolution imaging of AAV2-heparin complexes. The glycan density suggests multi-modal binding that could accommodate sequence variation and multivalent binding along a glycan polymer, consistent with a role in attachment, prior to more specific interactions with a receptor protein mediating entry.