AIDS researchers are still buzzing about a finding announced at the International AIDS Conference in Washington last week that provides insight into how an eventual cure for HIV/ AIDS might be developed.

Presented as a “late-breaker” finding on Thursday, Boston researchers described the cases of two HIV-positive patients who underwent bone marrow transplants and later developed undetectable levels of HIV in their blood.

The two cases are reminiscent of the so-called "Berlin patient," Timothy Brown, the only person known to have been cured of infection.

Five years ago, after Brown developed leukemia, he received a bone marrow transplant from a donor who was immune to HIV because of a rare double genetic mutation he carried, found in only 1 per cent of Caucasians. Not only did the transplant cure Brown’s cancer, his HIV essentially disappeared.

These two new patients didn’t receive bone marrow from such donors. But they were able to stay on their HIV medications throughout the bone marrow transplant process.

That appears to be the key to why they now appear to have no HIV left in them nine months after the transplants, says Dr. Daniel Kuritzkes of Brigham and Women’s Hospital, one of the researchers who studied the patients.

“These cells that our patients got didn’t have the receptor (found in the Berlin patient donor) but we were still able to protect them just with HIV medications,” Kuritzkes told CTV’s Canada AM Monday from Boston.

“This gives us hope that other approaches that are being studied as a possible cure may indeed be feasible and a reason for optimism.”

Kuritzkes and his team say it is too early to call the patients “cured,” because the men are still taking HIV drugs. But the results are intriguing to AIDS researchers.

HIV-infected patients are already more susceptible to cancers than most healthy people. Both of these men had developed Hodgkin’s lymphoma, but multiple rounds of chemotherapy and other treatments had failed. So they each decided to undergo stem cell treatments.

Kuritzkes says as the donor cells replaced the patients’ cells, the HIV disappeared.

“These cells were foreign and knocked off the patient’s own cells, thereby eliminating the HIV-infected cells that had been circulating in their blood,” he explained.

“The reason the new cells from the donor didn’t become infected is because the patients were able to stay on their HIV medicines the entire time, preventing the virus from reproducing and infecting these new healthy cells.”

Kuritzkes notes that bone marrow transplants are very risky; in HIV patients a marrow transplant is fatal in about 15 per cent of cases. The procedure is also expensive. That makes it unlikely as a treatment for all HIV patients, he says.

“I don’t think we’re going to be doing bone marrow transplants on healthy HIV-infected patients who are doing well on their anti-HIV medications anytime soon,” Kuritzkes said.

“What we’re hoping is that some gentler form or some other way of giving healthy cells to HIV patients could be developed in the future that would be a more acceptable way of treating patients.”

The next thing that researchers want to know is what will happen to if they take the treated patients off treatment with antiretrovirals – will the virus come back? Some fellow researchers say there are worries the virus could still be lurking in the men’s lymph nodes.

The patients are still considering whether to give their permission to stop their HIV meds and see what happens, Kuritzkes says.

Whatever the result, these patients have given AIDS researchers hope that other cure approaches may indeed be feasible.

“It gives us reason for optimism that we can find a cure for this terrible infection that will be applicable to patients with HIV across the world.”