AAV6.2-CAG-GFP

Adeno-associated virus (AAV) is widely recognized as a safe and effective method for gene transfer in a variety of tissues. The in vitro and in vivo transduction profiles of many AAV serotypes have been well characterized. Modification of AAV capsids by rational design or directed evolution can generate capsid variants with desirable properties, such as altered tissue tropism, enhanced transgene expression in target cells, or the introduction of binding domains to aid purification. A classic example is AAV-DJ, which is the product of recombination of AAV2 and AAV8 capsids to produce a hybrid capsid that combines the beneficial properties of both capsids: AAV2 has heparin binding and in vitro transduction ability, while AAV8 has strong in vivo liver transduction ability. Alternatively, single point mutations in the AAV capsid can also produce desirable modifications. AAV6.2 has a single nucleotide substitution in which amino acid phenylalanine (F) at position 129 is replaced by leucine (L). This alteration allows AAV6.2 to have a high infection efficiency, especially in airway epithelial cells, and has been used in lung, liver, and inner ear studies. Limberis et al. demonstrated that AAV6.2 was 2-fold more efficient than AAV6 in transducing mouse nasal, respiratory, and alveolar type II cells. Similarly, AAV6.2 mediated 2-fold higher serum concentrations of human alpha-1 antitrypsin (hA1AT) than AAV6 when injected intravenously into mice. Furthermore, intramuscular injection of the same AAV6.2-hA1AT vector mediated higher serum concentrations of hA1AT than either AAV6 or AAV9. Interestingly, of the more than 100 known primate AAV capsid sequences, F129L is a naturally occurring single-stranded residue in the majority of them. In fact, AAV5 and AAV6 are the only serotypes that encode a phenylalanine rather than a leucine at this position.