Did You Know…
That we’ve functionally cured someone (and possibly several someones) of HIV?
Timothy Ray Brown - otherwise known as the Berlin patient - is an American HIV patient from Seattle who had two bone marrow transplants to treat leukemia while he was living in Berlin five years ago. Brown has been free of antiviral drugs ever since, with no reappearance of the virus. Although traces of the virus genome may persist in his cells, he’s the only person we’ve ever functionally cured of HIV - until now.
The Berlin patient may have to share his title as two Bostonians also seem to be HIV-free after undergoing bone marrow treatments for cancer. The crucial difference is that the Boston patients have not yet stopped taking antiviral drugs - although that could well happen in the coming months.
"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," says Dr. Daniel Kuritzkes of Brigham and Women’s Hospital. “The antibody evidence tells us there is little - if any - persisting HIV protein to trigger an anti-HIV response.”
Kuritzkes and colleagues are very careful not to claim a “cure” for HIV, insisting that the Boston patients would have to be off antiviral drugs for years before they could be considered functionally cured. They do hope, however, that the Boston patients can give us some answers as to what cured Timothy Ray Brown, and help us better understand the virus itself.
It was always assumed that the “magic” of Brown’s cure resided in the stem cells he got from a bone marrow donor, as the donor cells lacked the receptor CCR5 - the very receptor HIV uses to enter immune cells. However, the Boston researchers have questioned the need for the absence of CCR5, as the bone marrow their patients received did not lack the receptor.
The Boston researchers think their could-be-cures could be down to one of two factors: Either the milder pre-transplant chemotherapy their patients received, or graft-versus-host disease. The milder pre-transplant chemotherapy was given to the patients so they could remain on their anti-HIV drugs throughout treatment, and the scientists postulate that this could have prevented HIV hiding out in their bodies from infecting the transplanted donor cells. Graft-versus-host disease, however - a phenomenon in which the donor cells see the patient’s own cells as foreign and attack them - is really piquing researchers’ interest, particularly because Timothy Ray Brown had episodes of graft-versus-host disease after his transplants.
It’s possible that the lack of CCR5 receptors did contribute to the Berlin patient’s cure, certainly - but scientists are very excited by the possibility that a cure may not require donor cells lacking CCR5 receptors, as that would considerably widen the donor pool. Very few people are lucky enough to lack CCR5.
Dr. Steven Deeks, from the University of California at San Francisco, was cautious when asked if an HIV cure was possible within the next decade. “I would be shocked,” he said, “But it’s at least possible, and we [scientists] all think it’s worth pursuing.”
The upper image is of HIV. The lower image is an SEM of healthy human bone marrow.