Timothy Brown, the "Berlin patient," was given two transplants and underwent total body irradiation to treat leukemia, while the British patient received just one transplant and less intensive chemotherapy.
His doctors found a donor with a gene mutation that confers natural resistance to HIV.
He said: "But what we are able to say with certainty is that, through early diagnosis and access to treatment, you can live a long, healthy life with HIV and be confident you won't pass the virus to your sexual partners".
"The so-called London Patient has now been off ART for 19 months with no viral rebound which is impressive, but I would still be closely monitoring his viral load", IAS Governing Council Member and co-chair of it cure initiative, Sharon Lewin, said. The donor - who was unrelated - had a genetic mutation known as CCR5 delta 32, which confers resistance to HIV. In 2012, he developed a blood cancer called Hodgkin's lymphoma.
Researchers from University College London announced the finding at the annual conference of retroviruses and opportunistic infections (CROI) ongoing in Seattle, USA this week.
HIV has been cured in a second patient, researchers are reporting.
The breakthrough comes ten years after the first such case of a patient with HIV going into sustained remission, known as the 'Berlin Patient'.
The unnamed patient, known only as the "London patient", was cured more than a decade after the "Berlin patient" was confirmed as the first person to be cured of the disease.
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.
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Professor Ravindra Gupta is a virologist at University College London.
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 worldwide researchers who do transplants in HIV-infected people with blood cancers. A second, less common form of HIV, could still cause infection despite a transplant like this.
Unfortunately, stem cell transplants are not only expensive, but risky.
AIDS virus now affects some 37 million people globally.
The London patient said that it was "surreal" and "overwhelming" to have both his cancer and his HIV cured at the same time. They will continue to monitor the patient to determine if he has been definitively cured (meaning the HIV does not come back).
After examining over and over the "London patient's" blood to look for H.I.V., the scientists could not find any circulating virus.
In their latest small study, presented at CROI, Tebas's team showed that in 15 patients who received this therapy and then stopped ARVs, HIV did rebound, but a few weeks slower than it does in people without such transplants.
"Today's news is a welcome development for many people living with HIV, but we must not take our eye off the ball in ensuring we use the tools we already have that can help us towards zero new transmissions".
The patient, who prefers to remain anonymous, remains HIV-free to date.