With a high probability more African primates than shown in Table 1 are carriers of an SIV, since for some species only a limited number of individuals have been tested and some have not been screened at all (99).
The common structure for primate lentiviruses is LTR-gag-pol-vif-vpr-tat-rev-env-nef-LTR, but some lentiviruses, have an additional gene, vpu or vpx in the central part of the genome (Figure 1).
As recently shown, humans are still exposed to a plethora of primate lentiviruses through hunting and handling of primate bushmeat in central Africa (71).
The possibility of additional zoonotic transfers of primate lentiviruses from species other than chimpanzees and sooty mangabeys has thus to be considered.
The basic genome structure applies to the members of the SIVagm, SIVsyk, SIVlhoest, SIVmnd-1 and SIVcol lineages (5, 10, 26, 35, 37, 45, 46, 52, 90).
SIVsm-related viruses, including HIV-2 and SIVmac, as well as SIVrcm, and SIVmnd-2 have a vpx gene upstream of the vpr gene (11, 17, 21, 48, 91).
Within the Colobinae, the living African colobids are further represented by 3 genera, Colobus or black and white colobus, Piliocolobus or red colobus and Procolobus or olive colobus.
The extent of this cross-reactivity is not known, and screening for SIV infection using HIV tests can thus underestimate SIV infection, but can also represent non-specific antibody binding (false positivity).
Simian immunodeficiency viruses (SIV) and the closely related human immunodeficiency viruses (HIV-1 and HIV-2) belong to the lentivirus subfamily of retroviruses.
SIVs are a large group of viruses that are found naturally in many African primate species, and serological and/or molecular evidences for SIV infection have been reported in at least 30 African non human primates (NHP) (44, 71).
In this paper we will summarize the actual knowledge on SIV infected primates and the characteristics of the currently identified SIVs.
Natural SIV infection has only been identified in African primate species.