"As long as Timothy Brown was the only [one], we'd have always wondered if there [was] something unique about it"'.
The case report comes 10 years after the first such case known as the "Berlin Patient". Yet Brown's case remained the lone success since then.
But there was something unusual about the person who gave the London patient stem cells.
"The concept of a cure for HIV is really being able to remove the virus", David Rosenthal, DO, PhD, medical director of the Center for Young Adult, Adolescent, and Pediatric HIV at Northwell Health in Great Neck, New York, who was not involved in the London patient's care, tells Health. Normally, the HIV binds to these receptors and attacks the cells, but a deletion in the CCR5 gene stops the receptors from functioning properly.
"At the moment the only way to treat HIV is with medications that suppress the virus, which people need to take for their entire lives, posing a particular challenge in developing countries", said the study's lead author, Professor Ravindra Gupta from the University of Cambridge, who led the study while at UCL.
Of course, remission is not necessarily a "cure" (though many have referred to this landmark achievement as such), Gupta told Cohen at Science. Other, more generally applicable strategies that may, in time, lead to a cure are also being investigated.
2nd HIV patient in 'sustained remission,' physicians say
In 2003, the male patient was diagnosed with HIV infection and developed an Aids defining cancer, advanced Hodgkin's Lymphoma, in 2012. Gupta did not expect this transplant to work either. "So while it's truly aspirational, I wouldn't say it's out of the realm of possibility".
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.
Twelve years ago, Timothy Brown - initially called the "Berlin patient" before he made a decision to go public - had this transplant and has been clear of HIV ever since. Meanwhile, in the decade between the successful cure of Brown and the London patient, none of the other attempts to use the same method have worked.
Now, doctors in Europe are reporting a second case of HIV remission after a similar stem cell transplant. The London patient has been free of the virus for a substantial amount of time, he acknowledges, but at this point, "it's still possible for the virus to come back". "Durable engraftment" of the CCR5 mutants is key to a cure, he concludes.
Steven Deeks, an HIV researcher at UCSF, says the results could also boost cure efforts to cripple CCR5 "without the need for heroic interventions such as in the Berlin and London cases". To do this in others, exact match donors would have to be found in the tiny proportion of people - majority of northern European descent - who have the CCR5 mutation that makes them resistant to the virus.
The researchers say the latest findings show that Brown's case was not a one off, and that there are ways to target the CCR5 receptor to treat HIV.