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An African primate lentivirus (SIVsm) closely related to HIV-2
V M Hirsch1, R A Olmsted, M Murphey-Corb
1Department of Microbiology, Georgetown University, NIH/Twinbrook II, Rockville, Maryland 20852.
Abstract:
The ancestors of the human immunodeficiency viruses (HIV-1 and HIV-2) may have evolved from a reservoir of African nonhuman primate lentiviruses, termed simian immunodeficiency viruses (SIV). None of the SIV strains characterized so far are closely related to HIV-1. HIV-2, however, is closely related to SIV (SIVmac) isolated from captive rhesus macaques (Macaca mulatta). SIV infection of feral Asian macaques has not been demonstrated by serological surveys. Thus, macaques may have acquired SIV in captivity by cross-species transmission from an SIV-infected African primate. Sooty mangabeys (Cercocebus atys), an African primate species indigenous to West Africa, however, are infected with SIV (SIVsm) both in captivity and in the wild (P. Fultz, personal communication). We have molecularly cloned and sequenced SIVsm and report here that it is closely related to SIVmac and HIV-2. These results suggest that SIVsm has infected macaques in captivity and humans in West Africa and evolved as SIVmac and HIV-2, respectively.
Insights
Human immunodeficiency viruses (HIV-1 and HIV-2) may originate from African simian immunodeficiency viruses (SIV). SIVsm from sooty mangabeys is closely related to HIV-2, suggesting a cross-species transmission origin.
Area of Science:
- Virology
- Primatology
- Evolutionary Biology
Background:
- Human immunodeficiency viruses (HIV-1, HIV-2) are lentiviruses.
- Simian immunodeficiency viruses (SIV) are found in nonhuman primates and are considered potential ancestors of HIV.
- HIV-2 shows close relation to SIVmac from rhesus macaques, but the origin remains unclear.
Purpose of the Study:
- To investigate the evolutionary origins of HIV-2.
- To determine the relationship between SIV strains from different primate species and HIV.
- To identify the specific SIV ancestor of HIV-2 and SIVmac.
Main Methods:
- Molecular cloning and sequencing of SIVsm from sooty mangabeys.
- Phylogenetic analysis to compare SIVsm with SIVmac and HIV-2 sequences.
- Review of existing serological surveys on SIV infection in macaques.
Main Results:
- SIVsm, isolated from sooty mangabeys, was molecularly cloned and sequenced.
- SIVsm is closely related to SIVmac and HIV-2.
- No evidence of SIV infection in feral Asian macaques was found.
Conclusions:
- SIVsm is the likely progenitor of both SIVmac in macaques and HIV-2 in humans.
- Cross-species transmission of SIVsm from sooty mangabeys to macaques and humans likely occurred.
- This study provides strong evidence for the origin of HIV-2 from African SIV.