Simian Immunodeficiency Virus: Animal Models of Disease

Simian immunodeficiency viruses (SIVs) are members of the genus Lentivirus and the family Retroviridae. SIV_mac was the first member of the group to be identified following isolation of a retrovirus from a captive rhesus macaque housed at a US primate center. The virus was introduced into captive macaque populations in the US during transfer of tissue from SIV-infected African monkeys to Asian macaques. Lentivirus genomes contain long terminal repeats at each end and genes encoding three virion structural proteins: core, polymerase, and envelope. In addition, all SIV genomes also contain five accessory genes, vif, vpr, rev, tat, and nef, and a subset of SIVs has one of two unique genes: vpr or vpu. SIV infects CD4+ cells of the immune system including T-cell, macrophages, and dendritic cells. While the CD4 molecule is the primary cellular receptor for SIV, a number of chemokine receptors are required co-receptors for SIV infection. While the endemic SIV infections of African monkeys and apes seem to be minimally pathogenic, SIV infections of Asian macaques cause simian acquired immune deficiency syndrome (AIDS). This disease results from the profound destruction of CD4+ T cells in lymphoid organs throughout the body. SIV infection of macaques closely mimics the pathogenesis, virology, immunology, and pathology of HIV infection in people and it has been used as a model to test strategies to prevent ot treat AIDS.