Scientists may have cured a man of HIV by injecting him with 'superpower' cells. Here's what it means for the future of AIDS treatment.

Scientists say they may have cured a man's HIV by performing a stem cell transplant to treat his cancer.Only one other person has been deemed “cured” of HIV before. He's also a cancer patient who got a stem-cell transplant.HIV/AIDS researchers say this is an exciting development, but it's also a risky strategy, perhaps even life-threatening.First there was one, now there are two: A second cancer patient has been treated with a bone marrow transplant, and it looks like that treatment cured him of HIV.This is the second time scientists have done this — the first person cured of HIV was an American man named Timothy Brown (originally nicknamed “the Berlin patient”). Brown received a bone marrow transplant in 2007 to help treat his aggressive leukemia. The new patient who may also have been cured has Hodgkin‘s lymphoma and lives in the UK.“It's cool because before this we had an 'n' of one,” microbiologist Jeffrey Milush, who directs the UCSF Core Immunology Laboratory, told Business Insider. (Milush was not involved in the latest research.) “Now we've got two people.” The scientists behind the feat are still approaching the case cautiously, though. “At 18 months post-treatment interruption, it is premature to conclude that this patient has been cured,” they wrote in the journal Nature Tuesday. But essentially, they think that’s what theyve done.In both cases, the patients weren't specifically trying to cure their HIV; they were dealing with aggressive strains of cancer, and their oncologists recommended bone marrow transplants to treat it.The reason that these specific bone marrow transplants seem to be capable of curing HIV is because both of the bone-marrow donors had a genetic mutation that made them more resistant to a common kind of HIV (the kind both patients had). “It does give them some superpower, in the sense of being protected from CCR5 -using HIV,” Milush said. CCR5 is one kind of HIV. But even though Brown is cured of that strain, he still has to take medications that prevent another strain, CXCR4, from replicating in his body. “They're not impervious to infection,” Milush said. “They are just more resistant to the major type of HIV.”What these cases mean for the future of HIV/AIDS treatment These types of stem cell transplants require harvesting blood marrow from a compatible human donor, wiping out the cancer patient's own immune system, then reconstituting it with the donated marrow. The cancer patient has to take potent drugs that help their body accept the donor's immune system.It's an expensive, invasive, and extremely complicated immunological dance, and bone marrow transplants can be fatal. “It's not simple,” Milush said.It's also not a realistic treatment option for most HIV patients, who don't necessarily have cancer. More than 38,000 Americans were infected with HIV last year, and 6,160 US deaths were directly attributed to HIV in 2016. Public health experts in the US have a bullish plan to end HIV in the US by 2030, but it does not involve expensive and dangerous bone-marrow transplants.“You've gotten millions upon millions of people infected with HIV, and you certainly aren't going to be doing stem cell transplants on all of them,” Milush said. “We need something that's going to be able to be rolled out to the mass population. If we focus only on these bone-marrow transplants, I think we're going to miss the opportunity to treat the widest group of people.”The most promising way to end HIV in the US, experts say, is to manage infected patients' viral loads with drugs, and to prevent the disease from spreading to more people.“We have very effective antiretroviral therapy, and when people are on retroviral therapy and achieve an undetectable viral level, they cannot transmit the disease,” US Health and Human Services assistant secretary for health Brett Giroir told reporters in February. But although various drugs on the market can make HIV a livable disease, it is still a dangerous condition if not treated well. And while these drug cocktails are good at controlling the virus, they don't eradicate it. So scientists like Milush are still on the hunt for a full-on HIV cure for all. Some of the most promising strategies to date include extracting and genetically transforming patients' own virus cells (sometimes with the CRISPR gene editing-technique), or a vaccine.The new case could also help scientists by informing future research into cures that would be less dangerous than bone-marrow transplants. “Continuing our research, we need to understand if we could knock out this [CCR5] receptor in people with HIV, which may be possible with gene therapy,” lead study author Ravindra Gupta said in a release.