Isolation and characterization of a new chimpanzee lentivirus (simian immunodeficiency virus isolate cpz-ant) from a wild-captured chimpanzee

Objective:
To assess the prevalence of infection with simian immunodeficiency virus (SIV) isolate cpz, a lentivirus closely related to HIV-1, in chimpanzees, and to obtain new SIV(cpz) isolates.

Methods:
Forty-four wild-captured chimpanzees in Belgium and Cote d'Ivoire were tested for HIV and SIV antibodies. Virus was isolated from the peripheral blood lymphocytes of positive animals and characterized by electron microscopy, Western blot and radioimmunoprecipitation assay.

Results:
One animal had antibodies that cross-reacted with HIV-1. A lentivirus was isolated and referred to as SIV(cpz-ant). With regard to molecular weight patterns, SIV(cpz-ant) differs from SIV(cpz-gab), an HIV-1-related virus isolated from a wild-captured chimpanzee in Gabon. The major core protein, the transmembrane and outer membrane glycoproteins of the SIV(cpz-ant) strain consistently had higher molecular weights. Significantly more HIV-1-positive sera reacted with the envelope proteins of the Gabonese SIV(cpz-gab) strain than with the SIV(cpz-ant) strain.

Conclusions:
This study shows that natural infection of wild-captured chimpanzees with an HIV-related virus may not be uncommon. The diversity of the two chimpanzee isolates, the different geographical origin and the absence of disease suggest that chimpanzees have not recently become SIV(cpz)-infected.