Adenoassociated viruses (AAV) are small (20-30 nm), ssDNA, non-enveloped and replication-defective viruses that infect human and other primate species, but which, up to now, have not been reported as being the cause any known disease. They can infect both dividing and quiescent cells.
When they occasionally do so, AAV always integrate in one non-mutagenic unique location (on Chromosome 19). Most AAV used for gene delivery are modified to force integration and are thus suitable for long-term studies. They do not ellicit strong immune responses owing to the removal of their VP2 capside protein by genetic engineering.
These features makes them excellent Gene therapy tools.