HIV viral particles under an electron microscope.
HIV viral particles under an electron microscope.
Image: Maureen Metcalfe, Tom Hodge (CDC)

A new study out Tuesday seems to confirm a remarkable achievement in the world of HIV research. A London man living with HIV who received an experimental stem cell transplant has appeared free of the virus for at least 30 months despite no longer taking medication. They say it’s strong evidence that he may be cured of HIV—the second such case ever documented.

Nearly four years ago, the man known as the London patient received a bone marrow transplant primarily meant to help treat his advanced blood cancer, Hodgkin’s lymphoma. But the transplant was sourced from a donor with a rare mutation that makes people nearly impervious to the most common type of HIV infection, HIV-1. Doctors hoped the transplant would not only help treat the man’s cancer but also reboot his immune system to resemble the donor’s, transferring that same resistance to HIV.

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Last March, his doctors reported that the man had no detectable traces of the virus in his system for 18 months since he stopped taking antiretroviral medication (typically, it only takes weeks for the virus to start proliferating again after standard treatment is stopped). At the time, they still cautioned that it was too early to declare him cured. But in a study published today in the Lancet HIV, they’re now much more confident about that possibility.

“The London patient has been in HIV-1 remission for 30 months with no detectable replication-competent virus in blood, CSF, intestinal tissue, or lymphoid tissue,” they wrote. “We propose that these findings represent HIV-1 cure.”

A day earlier, the London patient also revealed his identity for the first time in an interview with the New York Times: He is 40-year-old Adam Castillejo.

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“This is a unique position to be in, a unique and very humbling position,” Castillejo told the Times. “I want to be an ambassador of hope.”

Castillejo is the only second person ever thought to have been cured of HIV, which is typically a lifelong infection that can be suppressed but not fully cleared with existing medication. He follows Timothy Ray Brown, who received a similar stem cell transplant in 2007. Brown was known only as the Berlin patient until he publicly revealed himself.

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These cases, monumental as they are, are more a proof of concept than anything else. Some scientists still think we have to wait longer before we can be sure that Castillejo is cured. And even if he is, there are many practical reasons why we can’t just give everyone living with HIV these kinds of stem cell transplants (for one, they’re a very risky, last-resort procedure). We also don’t necessarily need a cure to end HIV as a public health threat, as I reported recently in an article about ending HIV. But researchers hope to build on the lessons learned from Castillejo and Brown to someday cure HIV for good.

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Science writer at Gizmodo and pug aficionado elsewhere

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