U.S. researchers have moved a step forward in developing gene therapy to treat HIV patients. Although viable treatment is still a long way off, researchers hope that one day gene therapy could potentially keep the AIDS- causing virus at bay. In the study, researchers at City of Hope, a hospital and research center in Duarte, California genetically manipulated healthy blood cells to resist HIV and inserted them into four HIV- positive patients who had lymphoma, a blood cancer. At this early point in the research process, the goal was to see if the implanted cells would survive. In the next phases of research, scientists will try to implant enough genetically engineered cells to actually boost the body's ability to fight off HIV. Ideally, the cells would multiply and fight off HIV infection. In that case, 'the virus has nowhere to grow, no way to expand in the patient,' said David L. DiGiusto, a biologist and immunologist at City of Hope. The research took place in people, not in test tubes, the researchers noted. Gene therapy has the potential to free HIV patients from a lifetime of taking medications that may fail to work, especially if the virus develops immunity to them, said David V. Schaffer, co- director of the Berkeley Stem Cell Center at the University of California at Berkeley and co-author of a commentary accompanying DiGiusto's study. The treatment wouldn't necessarily be a cure because the virus would remain in the body. Still, it could create a situation ' where HIV is present but at levels that are too low to detect and don't cause AIDS,' Schaffer said. The study was published in the June 16 issue of the journal Science Translational Medicine. 