UniProt release 8.7

The search for the origin of HIV-1

The origin of Human immunodeficiency virus 1 (HIV-1) has been the subject of hot debate for more than twenty years. In 1999, American, Japanese and French researchers claimed to have discovered an indisputable link between a chimpanzee virus from central West Africa called SIVcpz (Simian Immunodeficiency Virus from chimpanzees) and HIV-1. SIVcpz is 70-90% identical to HIV-1 and does not appear to cause illness in chimpanzees.

However, since SIVcpz was only found in a few chimpanzees held in captivity, the possibility existed that another yet unidentified species could be the natural reservoir of both HIV-1 and SIVcpz.

A recent study provides for the first time a clear picture of the origin of HIV-1 and the seeds of the AIDS pandemic. New strains of SIVcpz have been identified in wild chimpanzees from Cameroon. These new strains are more closely related to human HIV-1 than to any Simian viruses.

There are three HIV-1 lineages: M (Major), O (Outlier) and N (New). The new SIVcpz isolate MB66 turned out to be more closely related to HIV-1 group M than to any Simian virus (see a similarity search for SIVcpz MB66 gag-pol protein). Moreover, another wild virus, SIVcpz isolate EK505, is very closely related to HIV-1 group N. This suggests that at least two independent SIVcpz transfers from chimpanzee to man occurred in this region. HIV-1 group M presumably crossed species early in the 20th century. HIV-1 group N may have infected humans more recently.

The authors of the study also postulate that "given the extensive genetic diversity and phylogeographical clustering of SIVcpz now recognised and the vast areas of west central Africa not yet sampled, it is quite possible that still other SIVcpz lineages exist that could pose risks for human infection and prove problematic for HIV diagnostics and vaccines."

Proteins from SIVcpz isolates MB66 and EK505 are fully annotated and available from UniProtKB/Swiss-Prot.