The human immunodeficiency viruses type 1 and 2 (HIV-1, HIV-2) are members of the lentivirus subfamily of the retroviruses. As typical for all retroviruses, viral RNA replication requires the synthesis of a DNA intermediate, which is stably integrated into the host cell DNA (termed provirus). HIV can induce, after a long clinically silent period, the acquired immune deficiency syndrome (AIDS). In the case of HIV-1 infections, the majority of individuals will finally suffer from this late disease; whereas HIV-2 infections appear to exhibit a lower frequency of progression to AIDS.
