AAV1-EF1α-mCherry

Gene therapy involves the introduction of therapeutic nucleic acids into target cells in order to (i) replace the function of a defective gene, (ii) increase the expression of a downregulated gene, or (iii) reduce the harmful level of a protein by RNA interference or antisense techniques. Of the various viruses used as gene transfer vectors (retroviruses, herpes viruses, adenoviruses, poxviruses, etc.), the most impressive therapeutic successes to date are those achieved with retroviral vectors in treating children with X-linked severe combined immunodeficiency and with adeno-associated virus (AAV)-derived vectors in treating Leber congenital amaurosis, an inherited eye disease that causes retinal degeneration.

AAVs are small, nonenveloped DNA viruses that were originally discovered as contaminants of adenoviral preparations. They belong to the subfamily Parvovirinae and the genus Dependovirus of the family Parvoviridae and require co-infection with a helper DNA virus (adenovirus, herpes virus, or papillomavirus) to complete their productive replication cycle. AAVs are not pathogenic to humans or animals and have low immunogenicity compared to other viruses. AAV has an icosahedral capsid (22-26 nm in diameter) containing a linear single-stranded DNA genome of approximately 4.7 kb flanked by two T-shaped inverted terminal repeats. The left side of the viral genome contains the rep gene, encoding the nonstructural proteins rep78, 68, 52, and 40 required for DNA replication and packaging. The right side of the AAV genome contains the cap gene, which encodes the capsid proteins VP1, VP2, and VP3 and a newly discovered chaperone protein, the so-called assembly activation protein, which is required for capsid formation.