AAV5-Syn-iCre

Adeno-associated virus (AAV) is a non-enveloped, single-stranded DNA virus belonging to the family Parvoviridae that was originally discovered as a contaminant of adenoviral preparations. Unlike most other members of the Parvoviridae family, AAV is replication-defective and can only replicate efficiently in the presence of a helper virus, such as adenovirus or herpes virus. The infectious virus particle consists of a small (20 – 25 nm in diameter), icosahedral capsid containing a linear, single-stranded DNA genome, approximately 4.7 kb in length, with plus and minus strands packaged with equal efficiency into preformed, empty viral particles composed of 60 copies of the three viral proteins; VP1, VP2 and VP3.

The AAV genome organization is simple and consists only of a rep and a cap gene flanked by two inverted terminal repeats (ITRs). The Rep protein is required for DNA replication and for packaging of viral DNA into preformed capsids during efficient viral replication. Rep proteins are also required for the preferential integration of the wtAAV genome into human chromosome 19 and for the rescue of the integrated genome after superinfection with a helper virus. Interestingly, even though recombinant AAVs (rAAVs) are unable to integrate preferentially into chromosome 19 (because they lack the Rep proteins), they can trigger long-term transgene expression in post-mitotic tissues, most likely because they persist as largely circular episomes within the nucleus.