AAV6-CAG-FLuc

Although viruses can have a variety of morphologies, approximately half of known viral families have a broad icosahedral symmetry. A model icosahedral virus with T=1 symmetry is adeno-associated virus (AAV), a parvovirus belonging to the genus Dependoparvovirus in the family Parvoviridae. A variety of AAV serotypes are known, each with its own tropism for specific cell types. AAV can be engineered for use as a gene therapy vector by removing the viral genome and replacing it with an expression cassette containing tissue-selective regulatory elements and the gene of interest. AAV has recently become a well-regarded in vivo gene therapy vector with success in clinical trials for diseases such as hemophilia B, lipoprotein lipase deficiency, and Leber's congenital amaurosis.

AAV is a small, nonenveloped virus with a single-stranded DNA genome of 4.7 kb that contains two genes, rep and cap, located between two inverted terminal repeats. The rep gene produces the nonstructural Rep proteins that are essential for replication and packaging of the viral genome. The cap gene produces three structural proteins, VP1, VP2, and VP3, which are translated from different start codons and are located in the same open reading frame (ORF). Alternative mRNA splicing and the combined use of the ATG codon and alternative start codons for initiating translation of the VP proteins result in a capsid with a favorable stoichiometry of approximately 1:1:10 for VP1/VP2/VP3. The AAV genome was long believed to encode only Rep and VP proteins until 2010, when a second +1 frameshifted open reading frame (ORF) was discovered in the cap gene of AAV serotype 2 (AAV2), encoding a nonstructural protein of 204 amino acids in length. This new AAV protein was named assembly-activating protein (AAP) for its role in capsid assembly.