Natural infection of chimpanzees with new lentiviruses related to HIV-1/SIVcpz

To determine newly identified lentiviruses, termed simian immunodeficiency virus (SIV)cpz97CG4 and SIVcpz97CG6. from two wild-captured juvenile brothe r chimpanzees in the Republic of Congo, subgenomic pol (integrase, 288 bp), 5'tat/rev-env C1 (including vpu, 354 bp) and env (C2-C4, 544 bp) gene frag ments were amplified and sequenced. The analysis revealed significantly dis cordant phylogenetic positions of SIVcpz97CG in each genomic region. In the trees derived from partial env sequences (V3), both SIVcpz strains cluster ed in human immunodeficiency virus type 1 (HIV-1) subtype A. However. in th e trees derived from partial pol (integrase) and 5'tat/rev-env C1 (includin g vpu) sequences, they clustered independently from any of the known HIV-1 subtypes. Especially, in the 5'tat/rev-vpu tree, they branched before the r oot of HIV-1 group M. These findings suggest that these Congolese SIVcpz ge nomes are mosaic, probably due to a recombinational event in the recent pas t, and it provides evidence for a rather recently occurring cross-species t ransmission between humans and chimpanzees.