In 2007, Timothy Ray Brown underwent an experimental bone marrow transplant to treat his life-threatening leukemia. The marrow cells he received were no ordinary cells: They contained a very specific mutation that confers resistance to HIV. Brown, who grew up in Seattle but was living in Europe at the time, had been infected with HIV more than a decade earlier.
The procedure was harrowing, involving multiple rounds of chemotherapy, followed by radiation. He came down with graft vs. host disease and had to have a whole second transplant. But in the end, Timothy Ray Brown became the first person in the world functionally cured of HIV.