env Sequences of simian immunodeficiency viruses from chimpanzees in Cameroon are strongly related to those of human immunodeficiency virus group N from the same geographic area

Human immunodeficiency virus type 1 (HIV-1) group N from Cameroon is phylog enetically close, in env, to the simian immunodeficiency virus (SIV) cpz-ga b from Gabon and SIVcpz-US of unknown geographic origin. We screened 29 wil d-born Cameroonian chimpanzees and found that three (Cam3, Cam4, and Cam5) were positive for HIV-1 by Western blotting. Mitochondrial DNA sequence ana lysis demonstrated that Cam3 and Cam5 belonged to Pan troglodytes troglodyt es and that Cam4 belonged to P. t. vellerosus. Genetic analyses of the viru ses together with serological data demonstrated that at least one of the tw o P. t. troglodytes chimpanzees (Cam5) was infected in the wild, and reveal ed a horizontal transmission between Cam3 and Cam4. These data confirm that P. t. troglodytes is a natural host for HIV-1-related viruses. Furthermore , they show that SIVcpz can be transmitted in captivity, from one chimpanze e subspecies to another. All three SIVcpz-cam viruses clustered with HIV-1 N in env. The full Cam3 SIVcpz genome sequence showed a very close phylogen etic relationship with SIVcpz-US, a virus identified in a P t. troglodytes chimpanzee captured nearly 40 years earlier. Like SIVcpz-US, SIVcpz-cam3 wa s closely related to HIV-1 N in env, but not in pol, supporting the hypothe sis that HIV-1 N results from a recombination event. SIVcpz from chimpanzee s born in the wild in Cameroon are thus strongly related in env to HIV-1 N from Cameroon, demonstrating the geographic coincidence of these human and simian viruses and providing a further strong argument in favor of the orig in of HIV-1 being in chimpanzees.