Chimpanzee Reservoirs of Pandemic

Human immunodeficiency virus type 1 (HIV-1), the cause of human acquired immunodeficiency syndrome (AIDS), is a zoonotic infection of staggering proportions and social impact. Yet uncertainty persists regarding its natural reservoir. The virus most closely related to HIV-1 is a simian immunodeficiency virus (SIV) thus far identified only in captive members of the chimpanzee subspecies Pan troglodytes troglodytes. Here we report the detection of SIVcpz antibodies and nucleic acids in fecal samples from wild-living P. t. troglodytes apes in southern Cameroon, where prevalence rates in some communities reached 29 to 35%. By sequence analysis of endemic SIVcpz strains, we could trace the origins of pandemic (group M) and nonpandemic (group N) HIV-1 to distinct, geographically isolated chimpanzee communities. These findings establish P. t. troglodytes as a natural reservoir of HIV-1. S ince the first detection of an HIV-1– related lentivirus in chimpanzees (1, 2), this species has been suspected as the source of the human AIDS pandemic. However, a crucial missing link in the chain of evidence implicating SIVcpz in the origin of HIV-1 and AIDShas been the absence of a recognizable virus reservoir in wild-living apes. Chimpanzees (Pan troglodytes) are classified into four subspecies on the basis of differences in mitochondrial DNA sequence (3): P. t. verus in west Africa; P. t. vellerosus in Nigeria and northern Cameroon; P. t