Simian Immunodeficiency Virus Infection of Chimpanzees (Pan troglodytes)

A few years after the origin of human immunodeficiency virus (HIV)-2 was identified as the simian immunodeficiency virus (SIV) of the sooty mangabey, chimpanzees were found to naturally carry an SIV (SIVcpz) that is closely related to HIV-1, the virus responsible for the acquired immune deficiency syndrome pandemic. Among non-human primates, chimpanzees are uniquely susceptible to infection with primary isolates of HIV-1, with a generally nonpathogenic outcome. However, reports of the outcome of SIVcpz infection are conflicting. In this chapter we review the insights gained from extensive investigations of SIVcpz in wild chimpanzee populations, discuss the origin of SIVcpz, and evaluate the most recent estimates for the time that chimpanzees have been exposed to the virus. We examine reports of the consequences of SIVcpz infection in chimpanzees and discuss how SIVcpz might be distinguished from SIVs in other natural hosts. Finally, we outline the major outstanding issues that must be resolved to complete our understanding of this subject.