AAV3-Cre-GFP

Adeno-associated virus (AAV) was originally described as a satellite virus after being observed in electron micrographs of adenovirus. The physical properties of these satellite viruses isolated from different adenovirus preparations, such as capsid sequences and protease digestion patterns, are serologically distinct. These satellite viruses have been shown to be defective and require the function of a helper virus for efficient replication. As a result, AAV is considered replication-defective and is now classified in the genus Dependovirus of the subfamily Parvovirinae. Early studies showed that human seroprevalence of some serotypes exceeded 50%, and similar prevalence rates continue to be documented recently. However, even in the presence of high seroprevalence, AAV is considered non-pathogenic, a most desirable feature for virotherapy.

The structure of AAV is very simple. The genome consists of less than 4700 single-stranded bases. The ends of the genome are identical 145-base inverted terminal repeats (ITRs) that form a "T"-shaped hairpin due to base pairing of approximately 116/145 bases. The terminal repeats contain sequences for replication (rep) protein binding and nicking, and importantly, the ITRs are the only cis sequences required for packaging of the recombinant genome. Wild-type AAV ITRs flank two coding domains. First, the 5' domain encodes the four rep proteins (rep 78 kDa/68 kDa and rep 52 kDa/40 kDa). Size differences depend on promoter usage, map position (p) 5 or p 19, and alternative splicing.