A 42-year-old man who had both leukemia and AIDS received a bone marrow transplant — a common, late-stage treatment for that type of cancer. His doctor selected a bone marrow donor who had a rare genetic mutation that renders people virtually immune to HIV. The transplant appeared to cure the patient of AIDS.
We’re as wary as the next guy of inferring too much from a single case study. Maybe it was a fluke; maybe there were unknown factors at work. But this one is pretty intriguing.
The case was presented at a conference earlier this year (here’s the abstract), and written up in this morning’s WSJ.
As is common for bone marrow transplant recipients, the patient first had radiation and chemotherapy, which tends to kill off many of the immune cells that harbor HIV. After the transplant, the patient’s immune system was repopulated by cells created by the donor marrow.
The donor had a mutation, present in about 1% of Europeans, that creates immune system cells that lack a receptor molecule called CCR5. That receptor plays an important role in HIV’s ability to enter the cell. (Pfizer’s HIV drug Selzentry works by blocking CCR5.)
So the patient’s immune system was repopulated with immune cells that carried the mutation. And, nearly two years after undergoing the transplant, he shows no signs of having any HIV left in his body — despite the fact that he hasn’t taken any AIDS drugs since before the transplant.
Perhaps the most important caveat is just how risky bone marrow transplantation is: It’s given to cancer patients after other treatments fail, and it kills up to 30% of patients.
But researchers hope to apply the apparent lessons of this case to strategies using gene therapy (which carries its own risks) to try to induce the protective mutation in patients with HIV.
David Baltimore, who won a Nobel Prize for research on tumor viruses, has started a company to use gene therapy to target HIV. He calls this case “a very good sign” and a virtual “proof of principle” for gene-therapy approaches.