We've seen several breakthroughs in HIV treatment this year — early treatment "functionally cured" a child and helped fourteen adults go off HIV drugs — and now researchers from Boston's Brigham and Women's Hospital have discovered another advancement. At the International AIDS society conference, Timothy Henrich described how two men with longstanding HIV infections received bone marrow transplants that appear to have removed all traces of the virus from their blood, allowing them to go off medication. One man became infected with HIV in the early years of the disease's epidemic while the other contracted it as a baby, and both were receiving the bone marrow transplant to battle infection. At this point, it's been seven weeks and four months, respectively, since the men stopped taking HIV suppression drugs but the virus hasn't returned.

Of course, the doctors cautioned that the virus could return at any time. "Long-term follow up of at least one year will be required to understand the full impact of a bone marow transplant on HIV persistence," said Henrich. And he also cautioned that this treatment only worked in a very specific situation, as the men already needed to receive the bone marrow transplant for their blood cancers. Generally speaking, bone marrow transplants are a risky surgery with a 20 percent mortality rate — not the kind of surgery you'd want to go into unless it was really necessary. "This is not a practical strategy that we can do for most people with HIV," Henrich said. "It's also very expensive, so it's not scalable." Still, the researchers believe there's a lot that can be learned from these cases that can be applied to future HIV treatment options.