But the transplants were meant to treat cancer in the patients, not HIV.
With the right kind of donor, his doctors figured, the London patient might get a bonus beyond treating his cancer: a possible HIV cure.
His doctors found a donor with a gene mutation that confers natural resistance to HIV.
The patient received the bone-marrow transplant in May 2016.
"I never thought that there would be a cure during my lifetime", he said. The surprise success now confirms that a cure for HIV infection is possible, if hard, researchers said.
To learn more about the factors that favor a cure, amfAR, the Foundation for AIDS Research, a New York City-based foundation, in 2014 began to fund a consortium of global researchers who do transplants in HIV-infected people with blood cancers.
Nearly 1 million people die annually from HIV-related causes.
"Coming 10 years after the successful report of the Berlin Patient, this new case confirms that bone marrow transplantation from a CCR5-negative donor can eliminate residual virus and stop any traces of virus from rebounding", said Lewin, who was not involved in the new case study.
He quit taking anti-HIV drugs in September 2017, making him the first patient since Brown known to remain virus-free for more than a year after stopping.
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The Berlin patient - treated for leukemia - was given two transplants, and underwent total body irradiation, while the British patient received just one transplant and less intensive chemotherapy. "Everybody believed after the Berlin patient that you needed to almost die basically to cure HIV, but now maybe you don't".
That didn't happen with the London patient.
Scientists have tried, and repeatedly failed, to duplicate the success they had in curing Brown.
Timothy Henrich, a clinician at the University of California, San Francisco (UCSF), has seen HIV bounce back in two patients who had a conditioning regimen that impressively knocked down HIV reservoirs but whose transplants came from donors with working CCR5s.
"I think this does change the game a little bit", said Dr. Ravindra Gupta, a virologist at University College London who presented the findings at the Seattle meeting. To do this in others, exact match donors would have to be found in the tiny proportion of people - majority of northern European descent - who have the CCR5 mutation that makes them resistant to the virus.
"In a way, the only person to compare with directly is the Berlin patient", he said. "At the moment the procedure still carries too much risk to be used in patients who are otherwise well, as daily tablet treatment for HIV is able to usually able to maintain patient's long-term health".
"I am an optimist because I'm a scientist and vice versa", Henrich said.
"This tells us that the feasibility, and importantly, the availability of delivering this approach could possibly be achieved by the rapidly accelerating field of gene editing and related gene therapies". The transplant destroyed the cancer without harmful side effects, while the transplanted immune cells, which are now resistant to H.I.V., seem to have fully replaced his vulnerable cells, according to the paper.