The first and only person ever to be cured of HIV/AIDS is a leukemia patient treated in Berlin with HIV-resistant stem cells.
Although the Berlin patient was treated in 2007, researchers are only now officially using the word "cure." That's because extensive tests -- including analyses of tissues from his brain, gut, and other organs -- detect no sign of lingering HIV.
Few people with HIV would want to go through the grueling and life-threatening cancer treatment that was part of this cure. And so far, the cure has not been duplicated in other HIV-positive leukemia patients who underwent similar treatment.
Yet the finding already has transformed AIDS research. What really happened? What does this mean for people who have HIV/AIDS? Here are WebMD's answers to these and other questions about the first HIV cure.
HIV infects a kind of white blood cell called a CD4 lymphocyte, a key player in the immune response. What makes HIV so sneaky is that it infects the very cells that are supposed to rub out viral infections.
HIV replicates in CD4 cells when they are activated -- that is, when they are triggered by an infection. But some HIV-infected cells become inactive before the virus replicates. They go into a resting mode -- and the HIV inside them becomes dormant until the cell is activated.
HIV drugs don't affect HIV hiding in resting cells. These cells represent a hidden reservoir of HIV. When treatment stops, the resting cells eventually become active. The HIV inside them replicates and quickly spreads. That's why current HIV treatments don't cure HIV.
How was the Berlin patient cured of HIV?
The Berlin patient was 40 years old when he developed leukemia. He had been infected with HIV for more than 10 years, but he was keeping his infection under control with a standard HIV drug regimen.
Standard treatment for leukemia is to kill off most of a patient's blood cells with chemotherapy -- a process called conditioning -- and then to rescue the patient with infusions of stem cells from a matched donor's blood or bone marrow. The new stem cells then repopulate the immune system and kill off the leukemia cells that survived the conditioning treatment.