It’s not yet clear how the 10 people cured of HIV after stem cell transplants have managed to eliminate the virus, but in one case, unusually efficient natural killer (NK) cells may play a role. In 2024, researchers presented the “Next Berlin Patient,” a German man who has now been free of HIV for seven years after stopping antiretrovirals. Unlike Timothy Ray Brown—the original Berlin Patient—and six other people, he received stem cells from a donor with only one copy of a rare genetic mutation called CCR5-delta32 that blocks HIV from entering CD4 cells. A detailed analysis showed that he had a higher frequency of a specific subset of NK cells (NKG2A+/CD57+) and high HIV-specific antibody-dependent cellular cytotoxicity, exceeding that of natural elite controllers. He produced powerful antibodies—more potent than broadly neutralizing antibodies—that efficiently targeted his strain of HIV. These findings suggest that therapies that promote NK cell activation might help achieve a functional cure in people with HIV who are not eligible for risky stem cell transplants.