AAV1-CAG-Cre-2A-GFP

Adeno-associated virus (AAV) is a small, nonenveloped, single-stranded DNA packaging virus that belongs to the genus Dependoparvovirus in the family Parvoviridae. There are over 150 natural variants of AAV, of which 13 have been described as non-human and human serotypes. AAV is being developed as a gene delivery vector due to its lack of pathogenicity, ability to package recombinant DNA, long-term expression of transgenes, and ability to transduce both dividing and non-dividing cells. The most studied serotype, AAV2, has broad tissue tropism, while several other serotypes show improved tissue-specific transduction capabilities. For example, AAV1 is 1,000-fold, 35-fold, and 2-fold more potent than AAV2 in transducing smooth muscle, the central nervous system, and the retina, respectively, while AAV6 is 500-fold, 10-fold, and 10-fold more potent than AAV2 in transducing smooth muscle, heart, and lung, respectively. Differences in tissue tropism among AAV serotypes expand their applications in delivering a large number of different genes to treat a variety of genetic diseases. The T=1 icosahedral capsid of AAV is assembled from 60 copies of three overlapping viral proteins (VPs), VP1, VP2, and VP3, in a ratio of approximately 1:1:10. The complete sequence of VP3 is contained within VP2, which in turn is contained within VP1. Thus, VP1 contains a unique region, VP1u, and shares a common VP1/2 region with VP2. Superposition of the existing AAV serotype structures with the structurally ordered VP3 reveals a core eight-stranded antiparallel β barrel (βBIDG-βCHEF) motif and a conserved α helix (αA), with variable loops inserted between these secondary structural elements. Comparison of two serotypes that differ in sequence and structure, AAV2 and AAV4, has defined a total of nine variable regions (VRs) within the loop insertions. The VR rings constitute the outer capsid surface and determine serovar diversity, such as capsid topology, tissue tropism, antibody recognition, and transduction properties. The capsid surface is characterized by depressions at the icosahedral 2-fold axis, protrusions surrounding the depressions at the 3-fold axis, and a cylindrical channel at the 5-fold axis surrounded by canyon-like depressions.