91. Identification and Mutagenesis of the AAV5 Sialic Acid Binding Region

As a genus, the dependoviruses use a diverse group of cell surface carbohydrates for attachment and entry. Despite the fact that a majority of AAVs utilize sialic acid (SIA) for binding and transduction, this virus:carbohydrate interaction is poorly understood. Utilizing X-ray crystallography, two SIA binding regions were mapped for AAV5. The first site mapped to the depression in the center of the threefold axis of symmetry, while the second site was located under the HI loop close to the fivefold axis. Mutagenesis of amino acids 569 and 585 or 587 within the threefold depression resulted in elimination or alteration in SIA dependent transduction, respectively. This change in SIA binding was confirmed using glycan microarrays. Mutagenesis of the second site identified a role in transduction that was SIA independent. Further studies of the mutants at the threefold site demonstrated a change in transduction activity and cell tropism in vivo as well as resistance to neutralization by a polycloncal antibody raised against the wild type virus.