Can a Bone-Marrow Transplant Halt HIV?
By Eben Harrell / London Thursday, Nov. 13, 2008
The human immunodeficiency virus (HIV) is a pathogen so wily and protean that researchers rarely talk about curing infected patients, focusing instead on treatment and prevention. But in an announcement that caused a flutter of excitement and a wave of prudent skepticism, Berlin-based hematologist Gero Huetter claimed on Thursday that he has cured an HIV infection in a 42-year-old man through a bone-marrow transplant.
The patient, a U.S. citizen living in Germany, was suffering from advanced leukemia and HIV two years ago when Huetter treated the cancer with a bone-marrow transplant at Berlin's Charité hospital. As a side experiment, he inserted the bone marrow of a donor naturally resistant to HIV, the virus that causes AIDS. (Researchers have long known that about 1% of Europeans carry a genetic mutation that makes their cells resistant to HIV infection.) Bone marrow produces the cells that HIV attacks. So, the thinking went, inserting marrow that produces HIV-resistant cells might endow the patient with a means to repel the infection. Twenty months after the transplant, Huetter says, the man shows no signs of carrying the virus. (See stories of people surviving with HIV.)
Is this a viable cure for HIV? Not by a long shot. Even Huetter says bone-marrow transplants, which kill about a third of patients, are so dangerous that "they can't be justified ethically" in anything other than desperate situations like late-stage leukemia. Nor is it clear that Huetter's claim to have cured his patient is yet justified. HIV has a frustrating ability to hide in hard-to-detect "reservoir" cells in various parts of the body. Current antiviral drugs, for example, can lower a patient's "viral load" to the point that HIV is undetectable in his or her bloodstream. But as soon as such patients are taken off antivirals, the virus comes storming back.
Huetter's patient has not received antivirals for two years and remains virus-free even in the known HIV hiding spots of brain and rectal tissue, according to Huetter's tests. But many researchers remain skeptical about whether these tests have been thorough enough. Dr. Andrew Badley, director of the HIV and immunology research lab at the Mayo Clinic, told the Associated Press, "A lot more scrutiny from a lot of different biological samples would be required to say it's not present."
But there might be a glimmer of hope in the case. If the transplant does prove to have been a success and can be replicated, researchers say gene therapists might one day be able to re-engineer a patient's cells to change their bone morrow the same way a transplant does, except without the dangers. Such a breakthrough, if it proves possible, would be "decades rather than years away," according to Ade Fakoya, a London-based clinician and senior adviser to the nonprofit Aids Alliance. The treatment would also likely prove too expensive to implement in developing countries where HIV rates are highest, although some proponents of gene therapy say it could eventually be done cheaply through an injection, as with vaccines. (Read a TIME cover story on AIDS.)
Ron Noble of the British AIDS charity Avert says recent setbacks for research into an AIDS vaccine, along with multiple false hopes in the search for a cure, have caused many in the HIV activism community to view Huetter's experiment warily. For many AIDS activists, bone-marrow transplantation is a loaded procedure that evokes a traumatic past: before antivirals were widely introduced in the 1990s, it was one of the aggressive and often fatal procedures doctors tried in their desperate effort to halt the epidemic; some of these transplants even used marrow harvested from baboons.
In light of that pessimism about curing HIV in patients, Huetter's announcement was barely discussed at a major international HIV conference in Glasgow today, according to Fakoya, who was attending the event. He said greater attention was paid to more prosaic methods of defense, such as early identification and testing programs. "I'm in the conservative camp — I don't think there will be a cure," he says. "But if you look at antiviral treatment, data was provided at this conference confirming that you can live 30 years on [antiviral-drug] therapy, especially if it's initiated soon after infection. We are getting to a stage where HIV can be managed as a chronic illness. Now, that's not great, but I have a feeling it's the best we can do for the foreseeable future."