An HIV-infected human cellSTEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY A man has become the seventh person to be left HIV-free after receiving a stem cell transplant to treat blood cancer. Significantly, he is also the second of the seven who received stem cells that were not actually resistant to the virus, strengthening the case that HIV-resistant cells may not be necessary for an HIV cure. “Seeing that a cure is possible without this resistance gives us more options for curing HIV,” says Christia...