Finding a stem cell donor with a double copy of the HIV-resistant gene mutation was "an improbable event", said lead researcher Ravindra Gupta of University College London. He developed cancer and agreed to a stem cell transplant to treat the cancer in 2016.
"While there are important limitations to applying this study to a HIV cure globally, this second documented case does reinforce the message that HIV cures are possible".
16 months after the stem-cell transplant, September 2017, the man went off his antiretroviral drugs for HIV.
In some of the past transplant failures, the donor did not have a mutated CCR5, but the conditioning regimen seemed to have significantly reduced the "reservoirs" of cells in the recipient that have latent HIV infections, invisible to the immune system. His transplant beat cancer without any threatening side-effects, and the transplanted immune cells that were made resistant to HIV appeared to have replaced all the HIV-vulnerable cells in his blood.
Using bone marrow transplants to cure HIV in everyone who has the virus, though, remains impractical, expensive, and risky.
Gupta and his team emphasized that bone marrow transplant - a unsafe and painful procedure - is not a viable option for HIV treatment.
Gero Hütter, the German hematologist who treated Timothy Ray Brown, said: "By repeating the procedure in another patient, there is more evidence that the "Berlin patient" is not a sole exception".
"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.
Possibly. The London patient's immune system is now created to block HIV's most common path into cells, using the CCR5 receptor.
Nevertheless, the researchers are clear: "At 18 months post-treatment interruption it is premature to conclude that this patient has been cured". President Trump has been a proponent of cutting the budget allocated to fighting HIV and directing energies t5owards find a cure.
Advancements in antiretroviral drugs have greatly increased the life expectancy of people diagnosed with HIV in recent years.
But a reservoir of cells carrying HIV can still remain in the body, in a resting state, for many years.
The London patient is only the world's second person to go into remission from HIV.
The CCR5 gene, and the eponymous cell it codes for, nearly certainly play a crucial role in the collateral HIV cure. The new patient had none of this HIV variant, which probably contributed to the success of this treatment.
"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.
After news of the first "Berlin patient" broke at the same Seattle Conference in 2007, scientists have been trying hard to replicate the results in other HIV-infected patients.