On Wednesday, researchers from the U.S. facility in Duarte, California, reported that their oldest patient had been cured of HIV after receiving a stem cell transplant for leukemia. The 66-year-old patient was the fourth to be cured using the "Berlin patient" mechanism developed by Dr. Timothy Ray Brown in 2007.

While the transplant was planned to treat the patient’s leukemia, the doctors also sought a donor who was naturally resistant to the virus that causes AIDS. The patient was one of the oldest individuals who also had the longest history of HIV. He was diagnosed with HIV in 1988, which the patient described as a ‘death sentence’ that killed many of his friends. He has been on antiretroviral therapy for more than 30 years. Dr. Sharon Lewin stated that the case provided hope and inspiration for people diagnosed with HIV. She added that it is a remarkable cure, although it is an unlikely option for most people with HIV due to the risks of the procedure.

The researchers think that the process works because the donor’s stem cells have a specific, rare genetic mutation, i.e., they lack the receptors used by HIV to infect cells. Dr. Lewin added that researchers from Spain have also presented the details of a 59-year-old woman who is one of a rare group of "post-treatment controllers." These controllers are known to maintain undetectable viral loads after stopping anti-retroviral therapy.