Potentially Deadly Immune Response

Timothy Brown, known in biomedical circles as “The Berlin Patient,” has been HIV-free for ten years now. The medical research community has always believed that his cure was the result of a bone marrow transplant he received from a person with immunity to the virus — until now. Current research suggests that the cure might be the aftermath of an immune system war that the transplant cells triggered within his body — a war he survived, but the virus didn't.

The immune war is known more formally as graft-versus-host disease. It happens when a transplant takes place and new, transplanted cells bring their own immune response to the party. The body's existing immune reaction is already an issue, so the competing immune responses of the existing and donor cells attack each other. In Brown's case, the healthier donor cells won, killing not just the immune response in his cells, but also the HIV virus that lived there.

In fact, according to what the IrsiCaixa AIDS Research Institute's Javier Martínez-Picado tells New Scientist, there are at least six other patients who received similar treatments and achieved a cure as a result. They're fairly sure that graft-versus-host disease is responsible for this result because of those six additional patients, only one received donor material from someone with the HIV immunity. Therefore, something about the process — rather than the cells — must have cured them.

New Insight Into HIV

So, does this mean that doctors will induce an immune system war in patients intentionally, with the hopes that they'll live and be cured? Not likely. Of 23 HIV patients who received bone marrow transplants to fight cancer, about half have died (albeit some from cancer and some from the treatment). Additionally, while living with HIV is a scary prospect, current drug regimens are better than ever before, and in many cases succeed at keeping the virus at bay.

The breakthrough with this research is its potential for helping researchers understand more about HIV — including how it lives and hides in cells. The EpiStem Consortium, of which Martínez-Picado is a member, is investigating this issue of where HIV hides with the aim of developing a cure that wouldn't require a transplant. Ultimately, the immune system war triggered by a transplant — and the beneficial effects of graft-versus-host disease — is really about furthering science's ability to root out HIV where it lives, studying this process could, eventually, lead to a cure.

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