US doctors say they have saved a seven-year-old girl who was close to dying from leukemia by pioneering the use of an unlikely ally: a modified form of HIV.After fighting Emily Whitehead's disease with chemotherapy for almost two years and watching the young girl have two relapses, doctors at the Children's Hospital of Philadelphia said she "faced grim prospects". In February, they agreed to take her on in an experimental program that fought fire with fire.
Helped by a genetically altered HIV - stripped of the devastating properties that cause AIDS - doctors turned the girl's immune cells into a superior force able to rout the "aggressive" leukemia.
Emily was the first child and one of only a handful of people to be given what's officially known as CTL019 therapy.
The hospital stressed this could not yet be called "a magic bullet".
First, millions of the girl's natural immune system cells were removed. Then the modified HIV was used to carry in a new gene that would boost the immune cells and help them spot, then attack, cancer cells that had previously been able to sneak in "under the radar".
Finally, the rebooted immune cells were sent back in to do their work. "The researchers have created a guided missile that locks in on and kills B cells, thereby attacking B-cell leukemia," the hospital said.