After over a decade with HIV, a Norwegian man received a surprise through a stem cell donation from his sibling.

The gifted bone marrow was originally intended to treat the patient’s rare blood cancer, but researchers noticed a remarkable quirk. The sick man’s brother had a genetic mutation that made his stem cells resistant to the human immunodeficiency virus. 

Given that discovery, the team at Oslo University Hospital monitored the procedure extremely closely on the off-chance that it might lead to a “cure” for the patient’s HIV. Now, five years and many tests later, that hoped-for outcome has become reality, as reported Monday in the journal Nature Microbiology.

The unidentified man, known in medical spheres as the “Oslo patient,” is now the 10th person worldwide to be in full, long-term remission from HIV. As of 2024, almost 41 million people were living with the virus, according to the World Health Organization.

Speaking to Live Science, Marius Trøseid, an author of the study, said the patient “feels like he has won the lottery twice … He was cured of his bone marrow disease, which could be fatal, and he’s also now cured of HIV, most likely.”

While drugs that manage HIV are widely available, they’re designed to keep the virus from replicating within the body, not to eradicate the virus itself. This means HIV will likely re-emerge if medication is stopped for any reason.

But in the case of the Oslo patient, the brother’s genetic mutation didn’t just resist the HIV virus. It removed a certain receptor in the white blood cells that typically opens the door for HIV to infect the immune system, giving the virus nowhere to flourish.

As with any transplant, whether or not the donated tissue would take hold in the patient’s body was a gamble. The HIV-resistant stem cells won out in the end. 

In the Oslo patient, the researchers observed changes in the behavior of his immune system’s T cells, which get hijacked by HIV, leaving the body more vulnerable to germs and diseases.

After the procedure, his T cells eventually stopped behaving like they were under siege. 

The operation was so successful that the patient was able to stop taking his HIV medication two years later.

At four years, his medical team found no traces of any “functioning” HIV DNA in his body. And his most recent five-year check-up was consistent, too.

Still, doctors are hesitant to call the Oslo patient case an outright cure, because the process he and his brother underwent is impossible to replicate at scale. 

Stem cell transplants like these are seen as “risky reboots of the immune system” and can result in fatal infections, according to ScienceAlert. Up to 20% of patients who survive these operations will die within a year post-op.

Though he eventually pulled through, even the Oslo patient suffered from graft-versus-host disease, a serious complication that can accompany transplants.

Regardless, the researchers are optimistic about the findings, which they hope will help guide research into future cure methodologies that are more accessible and replicable.

“This and other studies on HIV cure enhance our understanding of HIV pathology, molecular mechanisms and predictive biomarkers that may be of broader interest” beyond patients treated with this kind of transplant, they wrote.

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