AAV5-hSyn-FLuc

Adeno-associated virus (AAV) belongs to the Parvoviridae family and primarily infects mammalian cells and is reportedly non-pathogenic to humans. AAV was first reported in 1965 as a contaminant of adenovirus and has since been identified as naturally replication-defective, requiring a helper virus such as adenovirus for propagation. The linear single-stranded DNA genome of AAV (approximately 4.7 kb) encodes two genes, rep and cap, flanked by inverted terminal repeats (ITRs), which are required for packaging of the viral genome into capsids. The ITRs are primers for second-strand synthesis and are the only elements of the genome that require cis sequences during viral production. For the production of recombinant adeno-associated virus (rAAV) vectors, the remaining viral genome can be removed, placed in trans on a separate plasmid, and then replaced with the desired transgene. The rep gene encodes four overlapping nonstructural proteins required for replication, integration, and packaging. Rep78 and Rep68 bind to the ITRs and have helicase and endonuclease activities necessary for AAV genome replication. Rep52 and Rep40 have 3' to 5' helicase activity and package the viral genome into capsids during virus production. The cap gene encodes three structural proteins, VP1, VP2, and VP3, which self-assemble into a 60-mer icosahedral capsid in a ratio of approximately 1:1:10. The three proteins are transcribed from the same open reading frame and share a C-terminal domain but have different N-termini due to alternative start codons and alternative splicing. cap also encodes a nonstructural protein, assembly activation protein (AAP), which is located in an alternative open reading frame to VP that was initially shown to be required for AAV2 capsid assembly. The dependence of AAP on capsid assembly is serotype specific, as AAV4, -5, and -11 do not require AAP for assembly. rAAV achieves high levels of long-term gene expression without chromosomal integration and exists episomally in the nucleus as head-to-tail ligands. rAAV episomes may be able to replicate in proliferating cells, albeit at a lower frequency.