Timothy Brown discovered he had HIV in 1995. In 2007, he got a couple stem-cell transplants from a donor with a genetic mutation called delta-32, and he now has no trace of HIV. Tina Rosenberg reports:
More than four years after he stopped taking anti-retroviral therapy, there is also no sign of HIV in his body. Brown is now surely one of the most biopsied humans on Earth. Samples from his blood, his brain, his liver, his rectum, have been tested over and over. People in whom the disease is controlled with anti-retroviral therapy will still have hidden HIV—perhaps a million copies. But with Brown, even the most sensitive tests detect no virus at all. Even if trace amounts remain (it is impossible to test every cell), it no longer matters. Absent the CCR5 receptors, any HIV still present cannot take root. He is cured.
A stem-cell transplant from an unrelated donor can cost $250,000 and is a reasonable risk only in the face of imminent death. What cured Timothy Brown is obviously not a cure for the rest of the world. But it is proof of concept, and it has jolted AIDS-cure research back to life. Sometimes science follows sentiment; the abandonment of cure research after the disillusion of the nineties is now playing out in reverse.
For Brown’s cure to be relevant on a wide scale, it would have to be possible to create the delta 32 mutation without a donor and without a transplant—preferably in the form of a single injection. As it happens, progress toward that goal has already begun, in the laboratory of Paula Cannon at the University of Southern California. Instead of a donor, Cannon is using a new form of gene editing known as zinc finger nucleases, developed by the California company Sangamo BioSciences. Zinc finger nucleases are synthetic proteins that act as genetic scissors. They can target and snip a specific part of the genetic blueprint: They can, for instance, cut out the code that produces the CCR5 receptor, yielding a cell with HIV resistance.
The re-booting of the immune system with HIV-free stem cells was much discussed in the early 1990s – only to be abandoned. I fervently believe that anti-retroviral treatment and sero-sorting are still easily the most cost-effective ways of curbing the epidemic. But getting HIV out of those pesky reservoirs where it can lurk forever, adding stem cells with an immunity to HIV so they replicate and reboot the entire body over time: this is exciting stuff.
Some part of me wants to die HIV-negative and American. I am now almost halfway there.