Abstract: Gene therapy aims to introduce genetic information into a cell-type of interest to replace, correct, silence, or modify defective genes. Gene therapy in its broadest sense can theoretically prevent, halt, or cure any condition that affects mankind. In addition to that, the introduction and/or manipulation of genes is one of the major research areas in biological sciences, aimed to deepen our knowledge on how biological systems work. Scientific advances have made it possible to induce changes ranging from manipulations of large stretches of the genome to the change of single nucleotides. The gold-standard vehicles to bring this genetic information into the target cells are viral vectors, amongst which the adeno-associated virus (AAV) is the most commonly used. AAV-vectors are small single stranded DNA viruses that naturally infect cells in humans and other primate species, thereby making them a perfect candidate for gene-therapy. In contrast to retroviruses, such as lentiviral vectors, AAVs are replication deficient and do not integrate into the host genome thus reducing the risk of insertional mutagenesis. Furthermore, AAVs are currently not known to cause any diseases in humans. The AAVs have an excellent biosafety profile and approximately 80–90% of the human population is already carrying the virus. There are currently about 13 naturally occurring variants known (serotypes), each with a different tropism profile to specific cell/tissue types (Vance et al., 2015).