AAV9-tMCK-mCherry

Recombinant adeno-associated virus (rAAV)-based gene therapy has revolutionized the clinical management of a wide range of genetic diseases. With more than one hundred clinical trials using AAV drugs to correct defective human genes, AAV has become the leading in vivo gene delivery system due to its low immunogenicity, customizable design, and safety profile.

The target tissues and cell types for transgene expression are primarily determined by the AAV capsid, with different wild-type AAV serotypes exhibiting different tissue tropisms due to differences in the regions that interact with specific cell surface receptors. Therefore, the AAV capsid must bind to various host biological components to facilitate efficient transduction of target cells. AAV binding to cell surface glycans is thought to act as attachment factors that enhance internalization by increasing interactions with transmembrane receptor proteins responsible for entry. The presence of specific types of glycans can affect binding and internalization in a manner specific to each serotype, potentially affecting tropism. Heparan sulfate proteoglycans were identified as essential components for AAV2 cell binding and transduction, making them the first recognized receptors. Subsequent studies revealed specific glycans for other serotypes, such as sialic acid moieties for AAV5, -1, -6, and -4, and galactose for AAV9. The glycans are considered “primary receptors,” meaning an early interaction characterized by low-affinity, indiscriminate binding of these glycans, leading to sequestration and concentration of AAV on the cytoplasmic membrane.