Established HIV infection is easy to control but impossible to cure. Or almost impossible.The exception seems to be Timothy Brown, a man often referred to as the Berlin patient.In 2006, after a decade of successfully suppressing his infection with antiretroviral drugs,Mr Brown developed an unrelated blood cancer, acute myeloid leukaemia.To treat this life-threatening condition he opted, the following year, for a blood-stem-cell transplant.And, at the same time, he volunteered as a guinea pig for an experimental anti-HIV treatment, which worked.
Now, a team of doctors in London have reported a similar case.Blood-stem-cell transplantation is an established, though extreme, treatment for various sorts of blood cancer.Stem cells are the precursors from which particular tissues grow.Blood-stem-cell transplantation involves using drugs (backed up, in Mr Brown's case, by radiotherapy)to kill a patient's natural blood-producing tissue, the bone marrow, and then transfusing in new stem cells from a donor.
So far, so normal. But Mr Brown, at the suggestion of his doctors,chose from among the 267 possible tissue-matched donors one who had inherited from both parents a mutation that,in healthy people, prevents HIV infection in the first place. (The mutation in question alters one of the proteins the virus attaches itself to when entering a cell.)After two such transplants Mr Brown was cleared of the leukaemia and, as far as it is possible to tell, HIV had stopped replicating in his body.