human T-cell lymphotropic virus type III; a cytopathic retrovirus (genus Lentvirus, family Retroviridae) that is 100-120 nm in diameter, has a lipid envelope, and has a characteristic dense cylindric nucleoid containing core proteins and genomic RNA. There are currently two types: HIV-1 infects only humans and chimpanzees and is more virulent than HIV-2, which is more closely related to Simian or monkey viruses. HIV-2 is found primarily in West Africa and is not as widespread as HIV-1. In addition to the usual gene associated with retroviruses, this virus has at least six genes that regulate its replication. It is the etiologic agent of acquired immunodeficiency syndrome (AIDS). Formerly or also known as the lymphadenopathy virus (LAV) or the human T-cell lymphotropic virus type III (HTLV-III). Identified in 1984 by Luc Montagnier and colleagues. SYN: lymphadenopathy-associated virus.