Terminal glucose as a receptor for adeno-associated virus 44.9

The isolation of novel adeno-associated virus (AAV) serotypes has led to significant advances in our understanding of parvovirus biology and vector development for gene therapy by identifying isolates with unique cell tropism and increased efficiency of gene transfer to target cells. AAV44.9 is a natural isolate originally found as a contamination of the laboratory stock of SV15 adenovirus. Its sequence homology places it between current clades in a small cluster with AAVrh.8R. Recent studies have suggested that AAV44.9 is a promising candidate for photoreceptor-targeted tissues, salivary glands, and other tissues. To better understand its tropism, glycan arrays and competition experiments were used to define its binding requirements for interacting with glucose and glucosamine on N-linked cell surface carbohydrates. Subsequent studies confirmed the role of these glycans in AAV44.9 transduction. Mutagenesis experiments were also used to identify amino acids responsible for glycan recognition and specificity.IMPORTANCEAdeno-associated virus (AAV) vector technology is rapidly advancing and becoming the leading vector platform not only in the field of gene therapy but also a useful tool for functional genomic studies of novel proteins. The characterization of the biologic activities of these vectors is critical to the further application of these vectors in gene therapy and understanding their natural tropism. In this study, we have identified terminal glucose as a unique glycan receptor for AAV 44.9 vectors. We have confirmed this binding activity via multiple methods and showed that the interaction is critical to vector transduction of AAV44.9. Furthermore, by comparing its sequence and difference in binding activity to another closely related but distinct vector AAVrh.8R, we have defined amino acids on the surface of the capsid that impact the interaction between AAV and terminal glucose.