title: The evolution of HIV-1 and the origin of AIDS.
abstract: The major cause of acquired immune deficiency syndrome (AIDS) is human immunodeficiency virus type 1 (HIV-1). We have been using evolutionary comparisons to trace (i) the origin(s) of HIV-1 and (ii) the origin(s) of AIDS. The closest relatives of HIV-1 are simian immunodeficiency viruses (SIVs) infecting wild-living chimpanzees (Pan troglodytes troglodytes) and gorillas (Gorilla gorilla gorilla) in west central Africa. Phylogenetic analyses have revealed the origins of HIV-1: chimpanzees were the original hosts of this clade of viruses; four lineages of HIV-1 have arisen by independent cross-species transmissions to humans and one or two of those transmissions may have been via gorillas. However, SIVs are primarily monkey viruses: more than 40 species of African monkeys are infected with their own, species-specific, SIV and in at least some host species, the infection seems non-pathogenic. Chimpanzees acquired from monkeys two distinct forms of SIVs that recombined to produce a virus with a unique genome structure. We have found that SIV infection causes CD4(+) T-cell depletion and increases mortality in wild chimpanzees, and so the origin of AIDS is more ancient than the origin of HIV-1. Tracing the genetic changes that occurred as monkey viruses adapted to infect first chimpanzees and then humans may provide insights into the causes of the pathogenicity of these viruses.
authors.affiliation: Institute of Evolutionary Biology, University of Edinburgh, Kings Buildings, Edinburgh EH9 3JT, UK. paul.sharp@ed.ac.uk
authors.forename: Paul M
authors.initials: PM
authors.lastname: Sharp
authors.forename: Beatrice H
authors.initials: BH
authors.lastname: Hahn
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000635:transmission* / Q000821:virology*; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D019143:Evolution, Molecular; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D010802:Phylogeny; D011323:Primates / Q000821:virology*; D015302:Simian Immunodeficiency Virus / Q000235:genetics*; D013045:Species Specificity; D015047:Zoonoses / Q000821:virology*