Adeno‑associated virus 7 (AAV7) is a parvovirus serotype originally isolated from rhesus macaque tissues. Like other adeno‑associated viruses, it is a small non‑enveloped icosahedral virus (~25 nm) with a single‑stranded DNA genome of ~4.7 kb. AAV7 is replication‑defective and relies on a co‑infecting helper virus for productive replication. Its natural cell receptor has not been identified, and unlike some other serotypes it does not bind heparin or other glycans.
Explanation
AAV7 was first identified in 2002 in tissues of rhesus macaques. Genomic analysis shows that it is distinct from primate AAVs, but its capsid proteins share structural similarities with other dependoparvoviruses. The virus contains inverted terminal repeats that bracket two open reading frames encoding non‑structural Rep proteins and capsid proteins. Like other adeno‑associated viruses, AAV7 cannot replicate without helper functions provided by adenovirus or herpesvirus. Cell binding and entry mechanisms remain uncertain; studies show that AAV7 does not bind heparan sulfate or sialic acid residues, and its primary receptor is still unidentified. Capsid analysis has revealed multiple post‑translational modifications, including glycosylation, phosphorylation, SUMOylation and acetylation. Because of this unknown receptor usage, purification protocols rely on ion‑exchange chromatography rather than affinity columns. Preclinical research has demonstrated that AAV7 has broad tissue tropism: it efficiently transduces skeletal muscle and achieves high transduction of hepatocytes in murine and human tissues, surpassing AAV2. In non‑human primate CNS it robustly transduces cortical and spinal neurons and glia, and in mouse retina AAV7 vectors transduce photoreceptors and photoreceptor precursors. Neutralising antibodies to AAV7 are relatively uncommon in human populations, a property that may make it valuable for gene therapy in patients who have pre‑existing immunity to common human serotypes.
Research uses and examples
Because of its potent transduction of muscle and liver cells and its low seroprevalence, AAV7 has been investigated as a delivery vehicle for gene therapy. In mouse models, intramuscular injection of rAAV7 vectors results in robust expression of therapeutic genes in skeletal muscle, and systemic delivery leads to efficient hepatocyte transduction. Studies in non‑human primate brains have shown widespread transduction of cortical and spinal motor neurons, raising interest in AAV7 for neurodegenerative disorders. AAV7 vectors have also been applied experimentally in retinal gene therapy to deliver genes to photoreceptors and retinal pigment epithelial cells. These examples illustrate the versatility of this serotype, though no approved clinical products currently use AAV7. AAV7 is a lesser‑known adeno‑associated virus with unique receptor independence and broad tissue tropism. Its low prevalence of neutralizing antibodies and ability to transduce muscle, liver, neural and ocular tissues make it an attractive candidate for future gene therapy applications once its receptor and entry mechanisms are better understood. Related Terms: Adeno Associated Virus 6, Adeno Associated Virus 8, Adeno Associated Virus 9, Adeno Associated Virus 2, Parvovirus 4