Matthew Warren in Nature:
A person with HIV seems to be free of the virus after receiving a stem-cell transplant that replaced their white blood cells with HIV-resistant versions. The patient is only the second person ever reported to have been cleared of the virus using this method. But researchers warn that it is too early to say that they have been cured. The patient — whose identity hasn’t been disclosed — was able to stop taking antiretroviral drugs, with no sign of the virus returning 18 months later. The stem-cell technique was first used a decade ago for Timothy Ray Brown, known as the ‘Berlin patient’, who is still free of the virus. So far, the latest patient to receive the treatment is showing a response similar to Brown’s, says Andrew Freedman, a clinical infectious-disease physician at Cardiff University in the UK who was not involved in the study. “There’s good reason to hope that it will have the same result,” he says. Like Brown, the latest patient also had a form of blood cancer that wasn’t responding to chemotherapy. They required a bone-marrow transplant, in which their blood cells would be destroyed and replenished with stem cells transplanted from a healthy donor.
But rather than choosing just any suitable donor, the team — led by Ravindra Gupta, an infectious-disease physician at the University of Cambridge, UK — picked a donor who had two copies of a mutation in the CCR5 gene that gives people resistance to HIV infection. This gene codes for a receptor which sits on the surface of white blood cells involved in the body’s immune response. Normally, the HIV binds to these receptors and attacks the cells, but a deletion in the CCR5 gene stops the receptors from functioning properly. About 1% of people of European descent have two copies of this mutation and are resistant to HIV infection.