But experts caution that while the man's outcome seems promising, the risky procedure might not work on otherwise healthy people with HIV and probably won't yield an overall cure for AIDS. Still, if the patient's HIV doesn't resurface, this would mark the first time HIV has been wiped out in any patient.
In 2007, Timothy Ray Brown received a stem cell transplant to treat his leukemia, a cancer of the blood. The procedure involves destroying a patient's natural immune system with chemotherapy and radiation, then boosting it back up by inserting bone marrow or blood stem cells from a healthy donor.
Brown's donor was not only a perfect match for his blood and bone marrow type but also happened to have a rare, inherited genetic mutation that makes carriers virtually immune to HIV. The donor's cells took root in Brown's body and multiplied. Three years later, Brown's leukemia is in remission, and he's also HIV-negative.
The German doctors' findings were published last week in Blood, the journal of the American Society of Hematology. "Our results strongly suggest that cure of HIV has been achieved in this patient," they wrote.
Other experts warn that HIV could still be present -- but dormant and undetectable -- in the patient's blood.
"'Cured' is a strong word. But this is very encouraging," Dr. David Scadden, co-director of the Harvard University Stem Cell Institute, told The Miami Herald. "From all indications, there was no residual virus. It's as good an outcome as one could hope."
But Jerome Zack, an HIV researcher at the University of California at Los Angeles, told MSNBC that "you can't eliminate the potential for there still being low-level virus in the body that's undetectable."
There's also a problem with replicating the same procedure in otherwise healthy patients who are HIV-positive but don't have leukemia. Plus, the genetic mutation found in Brown's donor, which makes patients resistant to HIV, is extremely rare.
"For him to receive the donor cells, his body had to have all of his immune system wiped out" and then receive a bone marrow transplant, Saag said. "The catch-22 here is that the best candidates for a cure, ideally, are people who are healthy" and don't have leukemia, he said.
Stem cell transplants are very risky because they wipe out the patient's immune system to the point where they could die without an insertion of healthy donor cells. That process is "very hazardous," Saag said. "Even if somebody doesn't die from a transplant, there are complications that make it very unpleasant for people to live with."