City of Hope researchers demonstrated the first successful long-term persistence of anti-HIV genes in patients with AIDS-related lymphoma. In the investigational therapy, patients underwent autologous hematopoietic cell transplantation (HCT) in which their own blood stem cells were harvested and genetically engineered with three anti-HIV ribonucleic acids (RNAs) that block HIV from infecting new cells.
The gene therapy was developed by City of Hope’s John Rossi, Ph.D. (pictured right), Lidow Family Research Chair and chair and professor, molecular and cellular biology, with technology that uses ribozymes and short strands of RNA, also known as small interfering RNA (siRNA), to selectively silence specific genes against HIV infection. The ribozyme molecule prevents the patient’s white blood cells from producing a protein called CCR5, which HIV needs to enter a cell. The new CCR5-deficient immune cells the patient produces are effectively resistant to HIV infection. Additionally, the siRNA inactivates the virus directly, and a third component, called a TAR decoy sequesters the HIV regulatory Tat protein from the virus. The goal of the therapy is to reboot the immune system to once again identify HIV and mount a response to the infection by lowering the viral load.
“While highly active antiretroviral drugs have managed to turn HIV infection from an immediate death sentence to a long-term manageable chronic condition, we are still seeking a cure,” said David DiGiusto, Ph.D. (pictured left), professor of City of Hope’s Department of Hematology & Hematopoietic Cell Transplantation, and lead author of the paper. “Our research and clinical trials are showing promise for this novel approach to treating HIV patients.”
John Zaia, M.D., Aaron D. and Edith Miller Chair in Gene Therapy and chair of virology, City of Hope, leads the human clinical trial of the therapy and is senior author of the paper. The researchers isolated healthy blood stem cells from four patients and modified the cells to have the therapeutic gene. They then infused the patients with a mixture of modified stem cells and normal stem cells and measured how long the new gene stayed present in the patients’ blood samples. None of the patients reported any negative side effects from the gene therapy.
“We still see evidence that the patients are producing the therapeutic genes, including the siRNA, as long as 2 years after transplant,” said Zaia.
A standard treatment for AIDS-related lymphomas is autologous HCT, which replaces the diseased bone marrow with healthy, functioning cells. Although the lymphoma may be put into remission, the underlying HIV infection still remains for HIV-positive patients. Patients are kept on lifelong antiretroviral therapy, but resistance to these drugs often can occur. The gene therapy research may eventually yield a cure for both the cancer and the HIV infection.
The team continues research and clinical trials to improve the efficiency of their process, so future patients can receive more genetically modified stem cells and boost their resistance to HIV.
Illustration: City of Hope.
City of Hope News Release (06/16/10)
Medical News Today (07/05/10)
Abstract (Science Translational Medicine; Vol. 2, Issue 36, 36-43 (06/16/10))