Current Literature: HIV-1 transmission from chimpanzee reservoir.

Abstract

Geo, F., Balles, E., Robertson, D.L. et al. (1999) Origin of HIV-1 in the chimpanzee Pan troglodytes troglodytes Nature 397, 436–441The introduction of human immunodeficiency virus (HIV) into humans is attributed to zoonotic transmission of primate lentiviruses. For HIV-2, the source is a genomically indistinguishable simian immunodeficiency virus (SIVsm) found in sooty mangabeys. The route for HIV-1 has been much harder to identify. Here, Geo and colleagues have used tissue from a laboratory chimpanzee that died in 1985 to show that HIV-1 derives from SIVcpz found in the chimpanzee species Pan troglodytes troglodytes.Polymerase chain reaction (PCR) was used to amplify four overlapping fragments, together comprising a complete proviral genome (SIVcpzUS). Structural and regulatory elements common to all primate lentiviruses were identified along with a vpu gene that is only found in HIV-1 and SIVcpz. Only three other SIVcpz strains have been reported – two from animals from the Gabon (SIVcpzGAB1 and SIVcpzGAB2) and one from Zaire (SIVcpzANT). Phylogenetic analysis shows that SIVcpzUS is clearly a new member of the SIVcpz/HIV-1 group of viruses, most closely related to SIVcpzGAB1 and SIVcpzGAB2. Mitochondrial DNA from the chimpanzee hosts shows that the closely-related SIVcpzUS, -GAB1 and -GAB2 strains were all isolated from the P.t.troglodytes subspecies, whereas SIVcpzANT was found in a P.t. schweinfurthii individual.HIV-1 in humans has been classified into three main groups – M, N and O – of which M is by far the major cause of AIDS. All three groups are phylogenetically closely related to the SIVcpz strains infecting P.t.troglodytes, with HIV-1 M and N groups having the strongest correlation.The data presented here, and the fact that the natural range of P.t.troglodytes maps with areas of HIV-1 endemicity, suggest that this chimpanzee subspecies is the natural reservoir for zoonotic transmission of SIVcpz/HIV-1 into the human population. The most likely route is through infection following animal slaughter as part of the ‘bushmeat’ trade.