This receptor was recently in the news after Chinese scientist He Jiankui claimed he'd edited the genes of embryos to include a protective version of CCR5. But since then, they've struggled to replicate the results. Twelve years ago, Brown became the first person to rid the virus from his body.
The patient received the bone-marrow transplant in May 2016. The "Berlin patient," aka Timothy Ray Brown, now 52 and living in Palm Springs, California, is widely considered cured because he has been HIV-free without anti-HIV drugs for more than a decade.
But McKnight cautioned that this won't necessarily lead to a treatment for all HIV individuals. More recently, researchers reported that a bone marrow transplant recipient in Minnesota had viral remission lasting almost 10 months after an analytic treatment interruption, but he too ultimately experienced viral rebound.
Brown's bone marrow donor also had the CCR5 mutation - something Dr. Sharon Lewin (a professor of medicine and director of the Peter Doherty Institute for Infection and Immunity, who was not involved in the London patient's treatment) told CNN is "exciting" given the remission period of the new patient compared with Brown's case. Donors have to be a genetic match and carry the malfunctioning CCR5 gene.
During the treatment the patient underwent "graft-versus-host" disease, where the donor's immune cells attack the recipient's immune cells. Replacing immune cells with those that don't have the CCR5 receptor appears to be key in preventing HIV from rebounding after the treatment. Extensive testing of blood plasma and T cells revealed undetectable HIV and his HIV-specific antibody level also dropped. About 10 weeks post-transplant he developed mild graft-versus-host disease, which resolved on its own. This means that when populations are treated effectively we can also stop new infections.
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Tests found no trace of the virus - which causes Aids - more than 18 months after the man came off the antiretroviral drugs he was using to manage the condition.
Brown told the Associated Press on Monday that he would encourage the London patient to go public because "it's been very useful for science and for giving hope to HIV-positive people, to people living with HIV".
Dr. Gupta from University College London has stated that the two rounds of successful treatment prove that the Berlin patient "was not an anomaly". What's more, this current case shows that remission can happen without harsh conditioning chemotherapy or radiation.
However, now that science has determined that the earlier Berlin patient's HIV cure wasn't merely a unusual fluke, it could open up the doors to new gene-level treatments for the disease. The London patient ultimately had no option but to try the experimental treatment when he was diagnosed with Hodgkin's lymphoma in 2012.
"We don't need cells from a donor anymore", Kiem said - which is critical, since so few appropriate donors are available and stem cell transplants have major risks. For one thing, the rare mutation in this case, a variant of a receptor called CCR5, only blocks one variety of HIV.