Accessory proteins of HIV and innate anti-retroviral factors

The HIV genome encodes several accessory proteins (Vif, Vpr, Vpx, Vpu, and Nef) unique to primate lentiviruses, in addition to the structural (Gag, Pol, and Env) and regulatory (Tat and Rev) proteins. Early studies showed that deletion of accessory proteins has a small or no effect on virus replication in cell cultures. However, recent studies have clearly demonstrated that these proteins are essential for efficient viral replication, dissemination, pathogenicity, and disease progression. Here, we summarize the current knowledge of HIV accessory proteins and their cellular targets, and discuss the functional roles of these biologically unique and important viral proteins for virus replication in vitro and in vivo.