Though there are some differences, the London case mirrors that of the Berlin Patient, Timothy Brown, who has remained free of HIV and off ART since a bone marrow transplant 12 years ago and, until now, was the only adult considered to be cured of HIV. Beforehand, each had been treated with toxic chemicals in a "conditioning" regimen meant to kill off their existing cancerous bone marrow cells.
The London patient has been free of the virus for a substantial amount of time, he acknowledges, but at this point, "it's still possible for the virus to come back".
The doctors selected a donor who had two copies of a particular mutation in the CCR5 gene that prevents HIV from infecting T-cells, a part of the immune system where the virus takes hold and does its damage.
The case report, carried out by researchers at UCL and Imperial College London, together with teams at the University of Cambridge and the University of Oxford, comes ten years after the first such case, known as the 'Berlin Patient'.
This is the second time a patient treated this way has ended up in remission from HIV. "We speculate that CCR5 gene therapy strategies using stem cells could conceivably be a scalable approach to remission", they said.
Brown told the Associated Press on Monday that he would encourage the London patient to go public because "it's been very useful for science and for giving hope to HIV-positive people, to people living with HIV".
"I did not want to be the only person in the world cured of HIV", Brown wrote in a medical journal in 2015, explaining why he made a decision to reveal his identity.
After more than a decade - and with over half a trillion U.S. dollars spent on HIV/AIDS research this century - we finally know that this incredible result can be replicated.
"I never thought that there would be a cure during my lifetime", the patient told The New York Times.
Scientists report a 2nd person has been cured of HIV
We can thus say the patient is functionally cured ", said Ravindra Gupta , one of the medics working on the man's case. However she said the process was not yet applicable to tens of millions of other HIV-infected individuals worldwide.
The exact treatment used here is unlikely to be repeated widely. Scientific research into the complex virus has in recent years led to the development of drug combinations that can keep it at bay in most patients.
Researchers from eight countries are tracking 45 patients with cancer and HIV who have or will soon have stem cell transplants. A stem cell transplant allows the body to be repopulated with healthy blood cells - and a new immune system. "Everybody believed after the Berlin patient that you needed to almost die basically to cure H.I.V., but now maybe you don't".
Timothy Brown, said to be the first person to "beat" HIV/Aids, was given two transplants and total body irradiation (radiotherapy) for leukaemia - a much more aggressive treatment.
Dr. David Hardy chairs the board of directors for the HIV Medicine Association.
To do that, researchers are studying new gene-editing technology, Kiem explained.
In both cases, the doctor used a a genetic mutation that leads to HIV immunity.
"We don't need cells from a donor anymore", Kiem said - which is critical, since so few appropriate donors are available and stem cell transplants have major risks.
"We really don't know what the long-standing significance of this is", says Dr. Rosenthal.