AAV6-CAG-iCre

The AAV life cycle consists of multiple stages, each of which may impede efficient infection. The first step of infection is the binding of AAV to target cells via the primary attachment receptor. The attachment process for each AAV serotype involves a number of different receptors and coreceptors, resulting in a wide range of tissue tropism. Next, AAV undergoes receptor-mediated endocytosis and is internalized via clathrin pits in a dynamin-dependent process. Once inside the host cell, the AAV capsid must undergo vesicular transport through the endosomal pathway. This step is critical for the transduction process, as the viral capsid appears to be altered by the drop in endosomal pH, preparing the virus for nuclear transport and uncoating. Structural changes in the AAV capsid trigger the externalization of a conserved phospholipase A2 (PLA2) motif on the unique N-terminal domain of the VP1 protein (VP1u). This step is critical for successful infection and is thought to facilitate viral escape from endosomes. Once in the nucleus, the virus uncoats, releasing its genomic ssDNA, and infection proceeds in a lytic or lysogenic manner. In the presence of a helper virus, lytic infection results in genome replication, viral gene expression, and production of the Rep, Cap, and AAP proteins. The Cap protein assembles into viral particles with the help of the AAP, while the Rep package the AAV genome into preformed capsids. However, in the absence of a helper virus, AAV can exist in a free form as a DNA concatemer or may integrate at low levels site-specifically into chromosome 19q13.4.