Adeno-associated Virus Type 2: A Latent Life Cycle

Publisher Summary This chapter discusses the structure and the genetic map of adeno-associated viruses (AAV). AAV constitute the Dependouirus genus of the family Parvoviridae , which are small DNA viruses, with a host range, extending from insects to humans. Those with vertebrate hosts belong to the subfamily Parvovirinae , whose members include both viruses with life cycles that are predominantly, if not completely, characterized by productive infection and viruses that establish latent infections as a prominent component of their life cycles. The AAV are members of the latter group; as such, they do not normally undergo a productive infection in cell culture unless there is coinfection with a helper virus, either an adeno- or a herpesvirus. The crystal structures of several parvoviruses closely related to AAV have been determined. An interesting feature of the interior capsid is the existence of 60 pockets, each capable of accommodating, and thus immobilizing 11 bases of the genome. There are three structural proteins, with overlapping amino-acid sequences, that differ in size, by the extension of the NH,-terminus. The genome of AAV, the most common human AAV, has been sequenced. There is an inverted terminal repeat of 145 bases, of which the terminal 125 bases are symmetrical. This chapter also describes the establishment of latency, integration, rescue, and replication of AAV.