Doctors say two more people are nearing AIDS 'cure' after a bone marrow transplants

The so-called Berlin patient is famously the only person in the world who has been cured of HIV. But he may soon have company.

Two people in Boston also seem to be free of HIV after undergoing bone marrow transplants for cancer, just as the Berlin patient did five years ago. The crucial difference is that the Boston patients have not yet stopped taking anti-HIV drugs – although that may happen in the coming months.

Harvard researchers got an enthusiastic response from an overflow crowd when they presented the first report on the patients at the 19th International AIDS Conference in Washington, D.C.

"As far as we've been able to measure, we can't find evidence of HIV infection in the patients' blood or blood plasma, and their antibody levels against HIV are dropping," Dr. Daniel Kuritzkes of Brigham and Women's Hospital told Shots. "The antibody evidence tells us there is little if any persisting HIV protein to trigger an anti-HIV response."

 Kuritzkes is careful not to claim cure of HIV – although he says it's "entirely possible" that the two patients are cured.

"We can't say we've replicated the Berlin patient's cure at this point because our patients remain on antiretroviral therapy," Kuritzkes says. Only if they stop therapy for months and years, without seeing a rebound of HIV in their blood, can these new bone marrow transplant patients be declared cured.

Meanwhile the Boston patients are shedding light on just what may have cured Timothy Ray Brown, the Berlin patient. He's an American HIV patient from Seattle who had two bone marrow transplants for leukemia while he was living in Berlin more than five years ago.

Brown has been free of daily antiviral drugs ever since with no reappearance of the virus. Thus, he's considered "functionally" cured, even if traces of HIV genes may persist in some of his cells. (That's a matter of some uncertainty.)

It's been widely assumed that the magic in Brown's cure resides in the stem cells he got from a bone marrow donor. Those donor cells lack a receptor called CCR5 that HIV uses to enter immune cells.

Not necessarily, the Boston researchers say. That's because the donor cells their patients got did not lack the receptor. So what's happening with them must be different from the Berlin patient.