"A combination gene therapy that endows human stem cells with three ways to resist HIV has passed its first safety test in humans," reports a study published today in Science Translational Medicine. "Four patients with AIDS who were infused with these cells tolerated the treatment, and the cells produced their anti-HIV weapons for up to two years...'It's a small study, but it's a step in the right direction,' says Pablo Tebas, a clinical researcher at the University of Pennsylvania in Philadelphia who works on gene therapy and vaccines for HIV. 'The most promising thing is that it shows you can modify stem cells in a way that makes them [HIV-]resistant, and the progeny of those cells would still be resistant to HIV and would still be functional.'"