A First Step Toward a Cure for AIDS? Novel Procedure Appears to Have Eliminated HIV
Dr. Jeffrey Laurence, Ph.D.
March 2009—Can a stem cell transplant cure AIDS? Physicians and HIV/AIDS researchers are eager to explore this question after a brief report in February 2008 of a formerly HIV-positive patient who now shows no detectable signs of the virus after undergoing the procedure.
This case offers hope for the future, but it must be approached with extreme care and rigor. Scientists must first determine whether the stem cell transplant approach can be replicated; if it can, they must then examine which biological mechanisms are responsible for the eradication of the virus. This work might then pave the way for a more widely accessible cure.
|This case offers hope for the future but it must be approached with extreme care and rigor.
The report, from a group of physicians from Germany, described a 40-year-old man whose HIV had been under good control for several years on antiretroviral therapy. Then he developed acute leukemia. In an attempt to cure the leukemia, he underwent a course of radiation therapy and chemotherapy in preparation for a stem cell transplant. But in his case, rather than simply using the best match among available stem cell donors, his physicians did something very clever. They also screened potential donors for a natural mutation known as delta32 CCR5. CCR5 is the primary means by which most types of HIV infect cells. People lacking this CCR5 receptor—a very small number—are resistant to infection by the most common forms of HIV.
The patient's stem cell transplant was a success, although relapse of his leukemia required a second transplant using the same donor. Now off all antiretroviral drugs for almost two years, the patient continues to show no detectable signs of HIV in his blood, bone marrow, lymph nodes, intestines, or brain. To the limits of our ability to detect HIV, it appears that the patient represents a functional cure: he is off antiretrovirals, has a normal CD4 count, and exhibits no evidence of virus by ultrasensitive viral load testing.
It is possible that the patient may have been cured of HIV/AIDS. His doctors continue to monitor him closely and new tests are being conducted. But stem cell transplants are not a practical cure for HIV in any event—their cost can run up to US$250,000, they are associated with a relatively high death rate from infectious and immunologic complications, and the number of delta32-CCR5 donors of appropriate tissue type would be very small. But further research may yield key answers about this intriguing development.
Dr. Laurence is amfAR's senior scientific consultant.