Monkey gene clue to origin of HIV

The identification of a crucial genetic difference between rhesus monkeys and humans could help develop new treatments to tackle HIV (human immunodeficiency virus), the virus that causes AIDS (acquired immune deficiency syndrome). Scientists based at the National Institute for Medical Research in the UK have pinpointed the key difference between a monkey gene that confers resistance to HIV, and its human counterpart, which does not. The team, who published their findings in the journal Current Biology, say their findings show that gene therapy could potentially be used to treat people infected with HIV.

HIV attacks the body's immune system, disarming its defences against infections and certain cancers. The virus attacks and kills crucial immune system cells, known as T-helper cells. Without T-helper cells, many other immune system cells cannot work properly, including B-cells that make antibodies. So people with AIDS have difficulty fighting off infections that would cause relatively minor problems in healthy individuals.

Rhesus monkeys are resistant to HIV infection, because of a gene called Trim5alpha, which makes a protein that somehow stops the virus copying itself after it has entered a cell. In the latest research, the scientists discovered that humans have a different version of Trim5alpha, which protects against several forms of retrovirus - but not HIV. The team found that by changing just one 'building block' (amino acid) in the human protein to that found in the equivalent place in the monkey protein, they could make the human protein active against HIV.

The scientists think that this single difference could explain why HIV has become established in the human population. More importantly, it suggests a target for potential new gene therapy treatments to combat the disease. 'In theory, it should be possible to take cells from an HIV-infected individual, make them resistant to HIV infection with the modified gene and reintroduce them into the patient', said team leader Jonathan Stoye, adding 'alternatively, we could seek drugs that activate the human gene against HIV'. The researchers now hope to test this approach in mice. However, Jo Robinson, of the UK HIV charity the Terence Higgins Trust stressed that although the research was important, 'we are still a long way from it having a practical application for people with HIV'.