OAKLAND, Calif. (KGO) -- Call it a cure or a long-term remission -- there are now two patients who no longer have HIV.
The first is Timothy Brown, known 12 years ago as the "Berlin patient."
The most recent one remains anonymous but is referred to as the "London patient."
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Both men had blood cancer and both received bone marrow transplants from a donor with an HIV-resistant mutation.
In other words, some people carry a genetic mutation known as CCR5 Delta 32 that helps prevent HIV from entering the cells.
"To find this rare set of donor and then match them is really what this experiment has been about with the 38 patients," explained HIV activist, Jeff Sheehy.
So far, 38 HIV patients have received bone marrow transplants. To date, only two are HIV-free.
Sheehy has been keeping track of a third person called the "Dusseldorf patient," whose results will be known soon.
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Notice how all these transplants have been done in Northern Europe. There is a genetic reason for that.
"Up to 10 percent of the population in parts of Northern Europe have this mutation that makes it almost impossible for them to get infected with HIV, the proportion is 1 percent or less in the U.S.," said Sheehy.
Researchers say this kind of therapy is not a safe and practical strategy for the majority of HIV patients.
"It's not something that is going to be rolled out to the general public. It's currently too risky and too complicated to do on a large-scale basis," explained Jeffrey Milush, an immunologist at UCSF.
Instead, the California Institute for Regenerative Medicine based in Oakland is working on gene therapy that will someday modify our own cells to ward off HIV.
"The advances we are seeing in cell and gene therapy in cells and gene therapy will be applied to HIV and we'll be able to cure it," said Sheehy.
Second patient appears free of HIV after bone marrow transplant