scAAV7m8-CAG-GFP

AAV is a non-enveloped, dependent parvovirus belonging to the Parvoviridae family. Its capsid consists of 60 subunits composed of three different proteins (VP1, VP2, and VP3) with a common C-terminus, which are generated by alternative translation of the AAV cap gene. The AAV cap gene is the primary factor determining the natural cell/tissue tropism of AAV and is therefore a key modifiable genetic element for optimizing transduction efficiency. Each capsid subunit contains nine variable regions, i.e., peptide loops extending from the virion surface, which are involved in capsid assembly, genome packaging, cell receptor interactions, and antigenic determinants of anti-capsid cellular and humoral immune responses. Currently, more than 100 different AAV serotypes have been isolated from humans, non-human primates (NHPs), and other species that display a wide range of tissue and cell tropisms, which are mainly determined by their primary attachment receptor and coreceptor specificities. These naturally occurring unique serotypes have been extensively screened for their ability to transduce a variety of target cells and organs. However, anti-AAV antibodies are common in the population, effectively neutralize AAV vectors and reduce transduction efficiency, and are often cross-reactive, which limits the widespread clinical application of many serotypes. A variety of strategies have been developed to optimize AAV capsids for gene delivery, including rational design, directed evolution, and phylogenetic reconstruction of ancestral capsids. These strategies have a variety of potential clinical benefits, such as the ability to change the tropism of vectors, avoid vector retention in non-target tissues, reduce innate immune responses against vectors, circumvent existing anti-vector humoral and cellular immune responses, and reduce the effective dose of AAV. Therefore, engineering methods to generate new capsids derived from natural or artificial AAV capsids, optimize target tissue specificity and reduce antigenicity is an effective solution to improve the tropism of vectors for persistently virally infected cells and tissues.