Human Immunodeficiency Viruses and the Pathogenesis of AIDS

THE ACQUIRED immunodeficiency syndrome (AIDS) is caused by a newly recognized member of the lentivirus family, the human immunodeficiency virus (HIV).¹This retrovirus family is distinct from the other subfamilies of human retroviruses, theSpumavirinaeandOncovirinae(Table 1). In particular, lentivirus genomes are large and contain several viral genes; the viruses frequently induce cytopathic effects in infected cells, and the disease they cause has a long incubation period resulting in immunologic disorders and neurological disease.²Lentiviruses have been identified in several other animal species, including horses, sheep, goats, cows, cats, and monkeys.¹,²This finding suggests that a progenitor virus entered the animal kingdom in the distant past and various strains evolved over time within each species. This could be the reason that the primate and human lentiviruses (the simian immunodeficiency virus and HIV) resemble each other.³Two subtypes of HIV, HIV-1 and HIV-2, have been