At that time, he was found to have the HIV infection. Scientists have already used the gene editing tool CRISPR to snip out HIV in human cells in the lab, but they are still years away from proving the technology is safe to use in patients. Unlike in the first case 12 years ago involving Timothy Ray Brown from Berlin, Germany, who described his bone marrow transplant as near death experience, the latest case had minimal side effects, thanks to progress in the medical field.
Brown, who had been living in Berlin, has since moved to the United States and, according to HIV experts, is still HIV-free.
Following his bone marrow transplant, the London Patient also got two copies of the CCR5 receptor.
A man in Britain has become the second known adult worldwide to be cleared of the virus after he received a bone marrow transplant from an HIV-resistant donor, his doctors said.
As with cancer, chemotherapy can be effective against HIV as it kills cells that are dividing.
Brown remains uninfected as far as scientists can tell, and no HIV has been detected in the London patient's blood for 18 months, save for one blip of viral DNA that researchers studying the man suspect was a false signal.
The London Patient has not been named yet, but Brown hopes both men will meet one day, but just not yet on account of publicity concerns. For one thing, the rare mutation in this case, a variant of a receptor called CCR5, only blocks one variety of HIV. He said simply, "I never thought that there would be a cure during my lifetime". The London patient, in contrast, had a milder regimen that targeted his lymphoma. "We speculate that CCR5 gene therapy strategies using stem cells could conceivably be a scalable approach to remission", they said.
"And maybe that's what's happening here - the graft is eliminating any residual HIV", Lewin said.
For the second time in the history of HIV infection, a patient seems to have been cured completely of the infection which eventually causes AIDS. The new patient had none of this HIV variant, which probably contributed to the success of this treatment.
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. "Durable engraftment" of the CCR5 mutants is key to a cure, he concludes.
The only previous patient to be cured of the virus was Timothy Ray Brown, an American known as the "Berlin patient". "That could be a fantastic way forward", Johnston says.
The researchers say it is too early to say the patient is "cured" of HIV. Exact match donors would have to be found in the tiny proportion of people - a lot of them of northern European descent - who have the CCR5 mutation. 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. Then he was taken off antiretroviral medicine (the treatment for HIV-positive patients). Today, researchers are reporting the second instance in which the transplantation of stem cells carrying this mutation has seemingly eliminated a viral infection.