Human Immunodeficiency Viruses: Origin

Abstract

Today it is well established that human immunodeficiency viruses HIV-1 and HIV-2 are the result of several cross-species transmissions from primates to humans. The four groups of HIV-1, group M, N, O, and P, reflect four independent cross-species transmissions in West-Central Africa. The SIVcpzPtt strains that gave rise to HIV-1 group M and N belonged to a viral lineage that persists today in chimpanzees (Pan troglodytes troglodytes) in south Cameroon. HIV-1 group O and P-related viruses are present in western lowland gorillas (Gorilla gorilla gorilla) from southern Cameroon but chimpanzees are the original reservoir of SIVgor. While HIV-1 N, O, and P infections remained mainly restricted to Cameroon, HIV-1 group M strains have spread across Africa and all the other continents. Similarly, HIV-2, which remained largely restricted to West Africa, is the result of cross-species transmissions from SIVsmm of sooty mangabeys (Cercocebus atys) on at least nine occasions, resulting in HIV-2 groups A–I. While the origin of the HIV-1 and HIV-2 viruses became clearer, some important questions concerning pathogenicity and epidemic spread of certain SIV variants in the human population need to be further elucidated.