HOW quickly HIV turns into AIDS might depend on an individual's DNA. Some variations in the DNA in mitochondria, the parts of cells that generate energy, seem to make AIDS develop twice as fast as others.

Stephen O'Brien from the National Cancer Institute in Frederick, Maryland, and colleagues examined data from five long-term studies tracking a total of 1833 people with HIV during the 1980s and early 1990s. This was before antiretroviral therapy (HAART) was commonly used, so the team could follow the disease's development without intervention.

By studying the time it took for the subjects to develop AIDS-related diseases and linking it to their genetic information, the team found that some mitochondrial DNA genotypes are associated with rapid development of AIDS. For example, subjects with specific sets of variations known as U5a1 and J haplogroups progressed to AIDS at twice the average rate of the studied population. In contrast, people with the H3 haplogroup progressed less than twice as slowly: (AIDS, DOI:10.1097/QAD.0b013e32831940bb).

This supports existing theories that mitochondria are implicated in the progression of HIV/AIDS. The virus kills immune cells by triggering cell suicide, which appears to happen more easily in cells with mitochondria that generate less energy. "Having less energy available seems to exacerbate the effects of the disease," says team member Sher Hendrickson. The U5a1 and

J haplogroups seem to be responsible for this lack of energy.

That means mitochondrial DNA tests could one day give an accurate prognosis for people with HIV, although further work on other genetic and environmental influence factors would be necessary first, says Hendrickson.

The research could also determine when an individual should start HIV therapy. "Mitochondrial DNA types may suggest which patients are more susceptible and should start HAART earlier than currently recommended," says Andrew Lever, who studies HIV at the University of Cambridge. The findings also suggest that screening mitochondrial DNA may help doctors choose the best combination of drugs.

Source: New Scientist