The therapy had an early success with Timothy Ray Brown, a USA man treated in Germany, who is 12 years post-transplant and still free of HIV. Timothy Ray Brown, also known as the "Berlin patient", is the first person ever cured of HIV. They're additionally impractical to attempt to treat the thousands already contaminated.
Doctors said the man's remission showed that a similar case more than a decade ago was not a fluke, but stressed that it was too soon to talk of a cure.
Learning that he could be cured of HIV infection and cancer, the "London patient" felt both "surreal" and "overwhelming".
The patient has not been identified.
According to the report, the patient was diagnosed with HIV in 2003 and was on anti-HIV drugs since 2012. It's unclear why he waited that long. He had developed cancer and received a bone marrow transplant with stem cells that ultimately proved resistant to HIV.
As the Guardian reports, University College London's Professor Ravinda Gupta, the lead author of the study, detailed that the next step for finding a HIV cure would be with gene-editing.
The transplant cleared the man's cancer and his HIV, but the resistant genes may not be the sole cause of his HIV remission. About 1 p.c of individuals descended from northern Europeans have inherited the mutation from each mother and father and are proof against most HIV. Gupta described this as a condition in which donor immune cells attack the recipient's immune cells.
That was "an improbable event", said lead researcher Ravindra Gupta of University College London.
"That's why this has not been observed more frequently", he added.
The transplant changed the London patient's immune system, giving him the donor's mutation and HIV resistance.
Regular testing confirmed that the patient's viral load remained undetectable, and he has been in remission for 18 months since ceasing ARV therapy (35 months post-transplant).
"If we can understand better why the procedure works in some patients and not others, we will be closer to our ultimate goal of curing HIV", said Cooke, who was not involved in the case study.
When drugs are stopped, the virus roars back, usually in two to three weeks.
Researchers learned that Brown and the "London patient" both shared a novel treatment course.
The idea is to use an initial drug to flush out HIV that is hiding from the immune system and then use standard antiretrovirals to kill the newly-exposed virus.
Gupta said the method used is not appropriate for all patients but offers hope for new treatment strategies. "We speculate that CCR5 gene therapy strategies using stem cells could conceivably be a scalable approach to remission", they said.
There are complications too. Stem cell transplantation is life threatening, with a mortality rate as high as 25 percent, and Brown was left with lasting side effects.
Like Brown, he required a bone-marrow transplant, in which blood cells are destroyed and replenished with those from a healthy donor.
Tez Anderson, who founded Let's Kick ASS (AIDS Survivor Syndrome) and has lived with HIV since 1983, said he fears the London news will reinforce the misperception that AIDS is no longer a epidemic thanks to advances in treatment, even though some 40,000 new HIV cases are reported in the United States every year.