Brown, who had been living in Berlin, has since moved to the United States and, according to HIV experts, is still HIV-free. The treatments are also too unsafe, expensive and risky to do for the large number of people who already have the virus that causes AIDS. Other attempts had failed. This is not a new idea: the CCR5 gene was infamously targeted by Chinese scientist He Jiankui, whose (possibly failed) attempt to edit human embryos to make them immune to HIV sparked an worldwide scandal last fall.
"The question is, is it in remission, which means that we've been able to stop the virus from reproducing itself temporarily, or is it truly cured, in which case it won't ever come back?" says Dr. Rosenthal.
Now, researchers at University College London report in a paper being published Tuesday in Nature that they have apparently eliminated HIV in a second person.
Gupta, now at Cambridge University, treated the London patient when he was working at University College London.
The patient has not been identified.
Both the Berlin patient and this latest patient needed a stem cell transplant for their blood cancers. In 2007, Brown received a hematopoietic stem cell transplantation from a donor with two genetic copies of the CCR5 receptor, then had another transplant a year later following a relapse.
Doctors found a donor with a gene-mutation that is naturally resistant to the HIV virus, according to the findings.
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CCR5 is the most commonly used receptor by HIV-1, the most common and most harmful type of HIV. The donor had this double copy of the mutation. "That's why this has not been observed more frequently".
He still doesn't take antiretroviral treatment, the treatment that most people with HIV take, and yet he remains essentially cured.
But it in the past 18 months he was taken off the extra drugs and regular testing confirmed his viral load is now undetectable.
Bone marrow transplants as an HIV cure is a treatment with harsh side effects, but The New York Times reported that scientists think giving patients similar HIV-resistant immune cells might do the trick. In September 2017, 16 months after the stem cell transplant, the "London patient" went off antiretroviral drugs and has remained HIV-free.
While some commentators are calling this a "cure" for HIV, the scientists who performed the experiment say it's too soon to say that. "We are being cautious" to call it remission for now, he said.
The "London patient" told the Times, "I feel a sense of responsibility to help the doctors understand how it happened so they can develop the science", adding that when he was apprised he might be cured it felt "surreal" and "overwhelming". He also received less aggressive conditioning chemotherapy (lomustine, cyclophosphamide, cytarabine and etoposide), alemtuzumab (Campath, a monoclonal antibody that targets CD52 on malignant B and T cells), and cyclosporine-A and methotrexate, immunosuppressive drugs used to prevent graft-versus-host disease (when transplanted immune cells attack the recipient's body). There are complications too.