Scientists say they have found the genetic mechanism for spontaneous curing infected patients of HIV, holding out new hope for AIDS sufferers.

French scientists have unveiled the genetic mechanism by which they believe two men were spontaneously cured of HIV, and said the discovery may offer a new strategy in the fight against AIDS.

In both asymptomatic men, the AIDS-causing virus was inactivated because of an altered HIV gene coding integrated into human cells, they wrote in the journal Clinical Microbiology and Infection.

This, in turn, was likely the result of the stimulation of an enzyme that may in future be targeted for drug treatment to induce the same response, they said.

"This finding represents an avenue for a cure," study co-author Didier Raoult of the French Institute of Health and Medical Research (Inserm) said on Tuesday.

Neither of the men, one diagnosed HIV positive 30 years ago and the other in 2011, have ever been ill, and the AIDS-causing virus cannot be detected with routine tests of their blood.

In both, the virus was unable to replicate due to DNA coding changes that the researchers proposed were the result of a spontaneous evolution between humans and the virus that is called "endogenisation".

"We propose that HIV cure may occur through HIV endogenisation in humans," they wrote. "We believe that the persistence of HIV DNA can lead to cure, and protection, from HIV."

The approach hitherto has been the opposite: to try and clear all traces of HIV from human cells.

The teams said they did not believe the two patients were unique or that the phenomenon was new.

Copyright AAP 2014.