A 60-year-old man in Germany is at least the seventh person with HIV to be announced virus-free after receiving a stem cell transplant 1. However, the man, who has been virus-free for almost six years, is only the second person to receive stem cells that are not resistant to the virus.

“I'm very surprised that it worked,” says Ravindra Gupta, a microbiologist at the University of Cambridge who led a team that treated one of the other people who are now HIV-free 2, 3. “It’s a big deal.”

The first person to be found HIV-free after a bone marrow transplant to treat blood cancer 4, was Timothy Ray Brown, who is known as the Berlin patient. Brown and some others received special donor stem cells 2, 3. These carried a mutation in the gene that encodes a receptor called CCR5, which is used by most strains of HIV viruses to enter immune cells. For many scientists, these cases suggested that CCR5 best target for HIV cure be.

The latest case — presented at the 25th International AIDS Conference in Munich, Germany, this week — turns that on its head. The patient, dubbed the next Berlin patient, received stem cells from a donor who had only one copy of the mutated gene, meaning their cells express CCR5, but at a lower level than usual.

The case sends a clear message that the search for a cure for HIV "is not just about CCR5," says infectious disease doctor Sharon Lewin, who directs the Peter Doherty Institute for Infection and Immunity in Melbourne, Australia.

Ultimately, the results expand the donor pool for stem cell transplants, a risky procedure offered to people with leukemia but unlikely to be rolled out to most people with HIV. About 1% of people of European descent carry mutations in both copies of theCCR5gene, but about 10% of people with such ancestry have a mutated copy Download references