Researchers are saying a pair of HIV-positive men from Boston, thought to have been cured of the disease after undergoing bone marrow transplants, has since seen the reappearance of the virus that causes AIDS in their bloodstream.

The Boston Globe reports a team led by Dr. Timothy Henrich, an infectious disease specialist at Brigham and Women’s Hospital in Boston, revealed the disappointing findings on Friday at a Florida conference on HIV.

“This suggests that we need to look deeper, or we need to be looking in other tissues . . . the liver, gut, and brain,” Henrich told The Globe. “These are all potential sources, but it’s very difficult to obtain tissue from these places so we don’t do that routinely.”

Both patients reportedly had undergone bone marrow transplants to combat lymphoma – and had since then stopped taking the costly cocktail of medicines that keeps HIV from reproducing in the body. HIV is a virus that attacks - and destroys - the body's immune system. An HIV-positive patient is said to have AIDS once their immune system has deteriorated beyond a certain, clinically measured point.

In one of the Boston patients' cases, the virus reportedly reappeared after 12 weeks of not having taken medication. In the other, it returned after 32.

“This is certainly telling us a lot about persistence, what we need to do, and how low we need to drop the levels of HIV reservoirs in order to allow patients to achieve remission,” Dr. Katherine Luzuriaga, professor of molecular medicine, pediatrics and medicine at UMass Medical School, told The Globe by phone from the conference.

Only one person is believed to have ever been cured of HIV in the world. In 2009, German doctors reportedly said they had tangentially cured an American after he underwent a bone marrow transplant for leukemia.

But The Globe writes Timothy Ray Brown, known as the “Berlin patient,” received the bone marrow transplant from a donor possessing a rare gene mutation, CCR5-delta32, thought to offer HIV resistance. Also, Brown reportedly submitted to an extreme, preparatory regimen involving massive doses of chemotherapy and radiation prior to the transplant. The Globe writes the Boston duo received much lower doses before their procedures.

Still, researchers hailed the Henrich team findings crucial to their ongoing understanding of the virus.

“There are a lot of hurdles,” Steven Deeks, a University of California HIV specialist and medical professor who attended the Florida summit, told The Globe. “But this [the Boston researchers’ approach] dramatically advanced the cure research agenda.”

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