Isolation and partial characterization of an HIV-related virus occurring naturally in chimpanzees in Gabon

Two cases of wild-born chimpanzees which were positive for HIV-1 antibodies were observed in Gabon. These animals were never experimentally exposed to HIV-1 and had no history of inoculation with human blood products. A retrovirus was isolated from one of these chimpanzees. Several of the viral proteins from this virus, designated SIVcpz-GAB-1 (simian immunodeficiency virus from chimpanzee), differed in molecular weight from the known corresponding HIV/SIV proteins. The major gag protein of SIVcpz migrated on SDS-PAGE with a relative molecular mass of 25.5 and the outer membrane proteins were 110, 155 and 185 kD, respectively. SIVcpz did not induce severe cytopathic effects in human and chimpanzee lymphocytes. Antigenically, SIVcpz seems to be closer to HIV-1 than to HIV-2 and the other SIVs. Nucleic acid hybridization experiments appear to indicate that the virus is different from HIV-1 and HIV-2.