GFP Adeno-Associated Virus ( AAV-NQVGSWS )

Recombinant adeno-associated virus (AAV) vectors are promising because they mediate stable and efficient gene expression with good biosafety. AAV-2 vectors can be targeted to alternative receptors by inserting specific peptide ligands into certain sites of the AAV capsid. Several sites in the AAV capsid have been identified as suitable for manipulation and incorporation of peptides, but only a few have been systematically evaluated for insertion of targeting ligands to alter the cellular tropism of AAV-2. While the unique VP1 and VP2 regions of the AAV capsid protein appear suitable for expression and display of even large incorporated targeting peptides on the vector surface, most publications refer to sites in the VP3 protein of AAV-2 for targeting purposes.

Girod et al. described three sites in the AAV-2 capsid exposed on the capsid surface for inserted integrin targeting peptides. One of these, adjacent to the arginine at amino acid position 588 (R588), was shown to preferentially transduce integrin-expressing or CD13-expressing cells. Since then, this capsid site has become the most commonly used site for the insertion of targeting ligands, leading to targeted transduction of various cell types, such as endothelial cells or certain other cell lines, especially because the insertion of peptides at this site reduces heparin binding of the mutant particles, thereby abolishing their natural tropism. In fact, it has recently been demonstrated that R588 is one of the four arginines that mediate the attachment of AAV-2 to its natural receptor. Insertion of peptides near R588 most likely interferes with this heparin binding motif and therefore abolishes (but does not completely eliminate) the natural tropism of the AAV-2 capsid. This allows the AAV-2 to be removed from the liver and relocated to other tissues in the body.