One percent of Caucasians have a gene variant that lacks the section known as CCR5 that helps enable the AIDS virus to enter the body. When a German AIDS patient received stem cells from a donor with the gene variant, he was able to be permanently taken off antiviral drugs. Researchers also reported that the transplant cured his leukemia.

Doctors chose to perform the stem cell transplant despite its risk because the patient's levels of the AIDS virus had increased after receiving chemotherapy to kill his leukemia, which he had developed in July 2006. They decided that since they were doing the transplant, they would try to find a donor who did not have the key section of CCR5. "Our thinking was that if we do this and replace his immune system with cells that are resistant to HIV, we can do two things at once by stopping his leukemia and his HIV infection," says Gero Hutter, a hematologist at Benjamin Franklin Hospital in Berlin who led his treatment and was co-author of the report.

Hunter and his colleagues scanned the genomes of 60 potential donors. From those, they found one without the CCR5 section. The day following the transplant, they stopped the antiviral therapy. It has been two years since the transplant, and according to Hutter, "There has been no rebound of HIV. Two years after transplantation, we can't find any HIV in this patient."

The results of the experiment may help researchers determine new ways to control the AIDS virus that don't require patients to take antiviral drugs for life. Jay Levy, an AIDS researcher with the University of California, San Francisco, predicts that the report "is going to stimulate a lot of companies to put more emphasis on gene therapy." And in fact, a trial being sponsored by Sangamo Biosciences of California recently began at the University of Pennsylvania. Its goal is to test whether a gene therapy can modify the immune cells in 12 patients infected with HIV so that they lack the CCR5 receptor. "The fact that you could put back into the patient CCR5-deficient cells and have those cells work to clear the virus -- that gave us a lot of confidence," says company spokeswoman Elizabeth Wolffe.

News Release: Stem cells cut AIDS virus in patient, ending need for drugs www.bloomberg.com  February 11, 2009