"This research further confirms the promising HIV curative effects of bone marrow transplantation from the relatively few persons who have the HIV-resistant cells known as CCR5/delta32 hematopoietic stem cells".
Unexpectedly, the stem cell treatment - from a donor with a mutation of the CCR5 gene, which is a co-receptor for the HIV-1 infection - ended up with Brown's HIV going into remission, where is has remained ever since.
But it in the past 18 months he was taken off the extra drugs and regular testing confirmed his viral load is now undetectable.
"There was no virus that we could measure".
"By achieving remission in a second patient using a similar approach, we have shown that the Berlin patient was not an anomaly", said lead author Ravindra Gupta, a professor at the University of Cambridge, referring to the first known functional cure.
"CCR5 is something essential for the virus to complete its life-cycle and we can't knock out many other things without causing harm to the patient", said Gupta.
The standard chemotherapy treatment failed to remove the cancer from Brown so, as a last-ditch effort, doctors proceeded with a bone-marrow transplant. Brown and the London patient also suffered from graft-versus-host disease as the transplanted immune systems attacked other recipient tissues as foreign. In interviews, most experts are calling it a cure, with the caveat that it is hard to know how to define the word when there are only two known instances.More news: Federer to face Tsitsipas in final
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The vast majority of people who express the CCR5 mutation live in Northern Europe, and there aren't many of them.
Not until the world heard of how the London patient, who was - to a lesser degree than Brown - battling with cancer and the virus. That transplant also appeared to clear his HIV infection.
The London patient, in contrast, had a milder regimen that targeted his lymphoma. Certain HIV antibodies and proteins declined in the blood of both men, she points out, which might offer a helpful early indicator of whether a cure strategy is working prior to stopping ARVs.
The AIDS pandemic has killed 35 million people around the world since it began in the 1980s and approximately 37 million people are now infected with HIV.
"Two factors are likely at play - 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".
Scientist are increasingly hopeful that cure would be found soon after over 30 years of rigorous research.
Brown said he would like to meet the London patient and would encourage him to go public because "it's been very useful for science and for giving hope to HIV-positive people, to people living with HIV", he told The Associated Press Monday.