However the virus did not return in the London patient's case and there is still no trace of the virus after 18 months off the drugs.
"The new bone marrow is resistant to HIV, and also the new bone marrow is actively eliminating any HIV-infected cells through something called "graft versus host" disease," said Lewin, co-chair of the International AIDS Society's cure research advisory board and a researcher at Australia's Doherty Institute. Until now, success in replicating that cure has been limited.
"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.
According to HIV.gov, there are approximately 1.1 million people in the United States living with HIV. Of these, about 1.1 million live in the U.S.
The research team for the London patient will present their findings at the annual Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle, Washington.
Since the pandemic began in the 1980s, more than 70 million people have been infected with HIV and about 35 million have died, most in Africa. Their immune system appears to be successful in controlling the virus, even without drugs.
Sadly, there are some people like Martin Shkreli who seek to profit from the HIV medications. However, these medications must be taken every day, have multiple distressing side effects, and can cost thousands of dollars each month.
The donor has two mutated copies of the CCR5 Δ32 allele, so the person is resistant to the HIV-1 virus strain that uses the CCR5 receptor since the virus can not enter the host cells. Both cases involved bone-marrow transplants, though the transplants were meant to treat cancer in the individuals, not HIV.
Timothy Brown, the "Berlin patient", was given two transplants and underwent total body irradiation to treat leukaemia, while the British patient received just one transplant and less intensive chemotherapy.
This is a hard treatment that carries a high risk of infection and other complications, such as graft-versus-host disease, blood clots and liver disease.
That didn't happen with the London patient.
According to doctors, the unnamed person received a bone marrow transplant from an HIV resistant donor and antiretroviral drugs about 19 months ago. This indicates that other patients, in the same circumstances, should where possible receive transplants from a donor with this same gene mutation. "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". If researchers can find a way to easily manipulate CCR5, perhaps with CRISPR gene editing, they could open up a path for H.I.V. patients to enter remission without undergoing invasive transplants.