A crucial genetic difference has been discovered that gives some monkeys but not humans HIV immunity, suggesting a new gene therapy for treating AIDS.

The discovery, by researchers from the UK National Institute for Medical Research, offers a clue to the origins of the AIDS epidemic. It suggests that HIV infection would not have become established in humans if the species carried the form of a gene present in some monkeys.

In humans, the researchers report, a single amino acid substitution (R332P) in the gene Trim5alpha can confer the ability to restrict HIV-1. Just this single change to the human gene should enable it to interfere with the replication process of the HIV virus to prevent infection.

“This discovery has significant implications for the development of effective gene therapy to combat AIDS,” says Jonathan Stoye, the study’s lead researcher. “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. These cells could then block progression to AIDS.”

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