The HIV virus is a virus that contains RNA and not DNA as its genetic material. Retroviruses produce an analogue (a kind of mirror image) of their RNA by using an enzyme known as "reverse transcriptase." The result of this capability is DNA that incorporates itself into the genetic material of the cell that the virus has invaded. It then uses the cell's own facility to produce RNA clones of itself and viral proteins. The means by which the virus actually destroys the cell is not known.
It has been proposed that the virus acts in vivo not so much by destroying the cells it invades but, rather, by preventing their clonal expansion in response to immune stimulation.
The virus appears quite similar to the STLV-III virus which infects the African Green Monkey without causing illness and the HTLV-IV virus which infects humans without causing disease. Other viruses believed capable of causing AIDS are LAV-2 and SRB. These closely related retroviruses belong to a family of viruses called Lentivirus. A recently identified virus of the Lentivirus family, designated FTLV, has produced AIDS-like symptoms in cats. Other Lentiviruses include the visna viruses of sheep, the equine infectuous anemia virus of horses, and the caprine arthritis-encephalitis virus of goats.