The poor dude had both cancer and HIV. After the aggressive treatment for the leukemia, a funny thing happened:
The treatment Brown underwent was aggressive: chemotherapy that destroyed the majority of his immune cells. Total body irradiation. Finally, a risky stem-cell transplant that nearly a third of patients don't survive—but that appears to have completely cured Brown of HIV.
Doctors were savvy when they chose a stem cell donor for Brown. The man whose bone marrow they used has a particular genetic mutation, present in an incredibly small percentage of people, that makes him almost invulnerable to HIV. With Brown's own defenses decimated by treatments, the healthy, HIV-resistant donor cells repopulated his immune system. The initial indications that the virus had abated were promising. But only just now, having taken no antiretroviral drugs since the transplant, and following extensive testing shows no signs whatsoever of HIV, have his doctors given the official word: