The treatment wasn't a new scientific technique or high-tech drug. Instead, the cure was an accidental side-effect of a decades-old medical procedure that was once the basis for a Nobel Prize : a bone marrow transplant.
Bone marrow transplants have shown remarkable results in more than 70 different diseases, a wide-ranging list that includes cancers, inherited disorders and diseases of the immune system.
But they are also very risky, intense and expensive, making them a treatment of last resort, and unlikely to become a viable treatment option for the roughly 37 million individuals living with HIV worldwide.
Bone marrow transplants essentially require first wiping out a patient's disease-fighting immune system, using either radiation or chemotherapy, to pave the way for the transplant.
Patients then get an infusion of either bone marrow from a donor's hip or stem cells from blood, which eventually begins producing new, healthy cells so the body can fight infections again.
Bone marrow is often compared to a factory that makes blood cells, so think of a bone marrow transplant like tearing the factory down and rebuilding it.
Jay Feinberg was diagnosed with leukemia in the early 1990s and told he needed a bone marrow transplant to survive. Difficulty finding a donor match led him and his family to found the nonprofit Gift of Life Marrow Registry, where he now serves as CEO.
Cancers like leukemias, lymphomas and multiple myeloma are some of the more common reasons that patients might get bone marrow transplants.
After years of searching, Feinberg eventually did find a match and has been leukemia-free for 24 years now. But finding matches for patients continues to be a problem, because there's a need for donors from more diverse backgrounds , he said.
The transplant procedure carries risks of infection and other potential complications, including a life-threatening one in which cells from the donor attack the recipient. "It's not an easy process, but thankfully it works and it can cure your disease," he told Business Insider.
The only known HIV cure, but not a solution
Because bone marrow transplants are the only known HIV cure today, there's been some excitement about how they may be used.
Susan LeLacheur , a physician assistant who treats individuals living with HIV in Washington, DC, says that a couple of her patients have asked about bone marrow transplants.
She has explained to them that it's only a good option for those who also have cancer, in very specific circumstances, and that it's a difficult process.
The two men who appear to have been cured of HIV only got bone marrow transplants because they had been diagnosed with aggressive cancers. Importantly, their bone marrow donors also had a genetic mutation that helps with resistance to a common type of HIV.
People are excited because "the idea of a cure hasn't been out there for a while," she said. But "it's kind of more exciting for what it portends for the future ," with biopharma companies using the technology as the basis for cutting-edge new approaches to treating disease.
Effective HIV treatments also make it possible today for the estimated 1.1 million Americans who live with HIV to control it by taking pills each day. The medications allow many individuals to live long lives and avoid transmitting HIV, which is commonly spread through such activities as sex and sharing needles or syringes.
