In this process, the team selectively removed the alpha/beta-positive T cells and CD19-positive B cells from the donor graft, as those are more likely to trigger donor cells to attack recipient cells, resulting in a dangerous complication known as graft-versus-host disease (GVHD). At the same time, the process preserved healthy, mature, immune-active cells known as natural killer and gamma/delta-positive T cells that help prevent disease relapse and protect against infection. A total of 45 patients with acute leukemia were treated with genetically engineered stem cells from one of their parents. Transplants engrafted in 44 of the 45 patients, with a 29 percent cumulative incidence of mild GVHD. One month after transplant, follow-up analyses showed that transplanted cells had persisted in the patients and demonstrated potential anti-leukemic activity, which continued to increase over time."Our results, which demonstrate that transplantation of selectively modified, half-matched donor stem cells boasts success rates equivalent to those of a fully matched transplant, preventing GVHD and reducing transplant-related death, help continue to establish this approach as a viable option for patients without a matched donor," said study author Alice Bertaina, MD, of the Bambino Gesu Children's Hospital in Rome, Italy. "This has the potential to make this lifesaving treatment more accessible to a much larger population of patients who may not have a perfect donor match." Dr. Bertaina will present this study during an oral presentation at 5:00 p.m. CST on Sunday, December 8, in Rooms 208-210 of the Ernest N. Morial Convention Center. Immune Reconstitution and Preliminary Safety Analysis of 9 Patients Treated With Somatic Gene Therapy for X-Linked Severe Combined Immunodeficiency (SCID-X1) With a Self-Inactivating Gammaretroviral Vector [ 715 ] Previous studies have investigated the potential for gene therapy using a retroviral vector to treat children with the fatal inherited disease, X-linked severe combined immunodeficiency (SCID-X1, or "bubble boy disease"). The vector works by latching to the surface of the T cell and injecting genetic material that helps "train" the cells to properly produce their own immune cells. While successful in earlier studies, in some cases the children developed leukemia when new corrective genetic material was inserted near a trigger in the children's DNA, predisposing T cells to turn into cancer cells.