But then her parents put Emma through an experimental treatment at Children’s Hospital of Philadelphia.

They infected her with a version of HIV, reprogrammed to attack cancer cells.

Whitehead almost died, but the treatment worked and now she's in remission — and doing cartwheels all over her house.

Grady says the treatment hasn't worked for all patients.

It worked completely on three adults. Four treated adults have merely improved. A child relapsed. The treatment failed two adults completely.