For about a decade, scientists have had remarkable success curing some blood cancers by modifying a patient’s own immune cells to recognize and kill the malignant cells. That same approach may help control HIV, among the wiliest of viruses, scientists will report Tuesday. After a single infusion of immune cells engineered to recognize the virus, two people in a new study have suppressed their HIV to undetectable levels, one of them for nearly two years. The data is scheduled to be presented at a gene therapy conference in Boston, but the researchers shared an early copy with The New York Times. The treatment is years, if not decades, from being widely available, but the study offers what scientists call “proof of concept,” and the tantalizing hope that a single shot could one day offer lifelong relief from HIV. “It is inspiration and a potential road map to get to where we need to go,” said Dr. Steve Deeks, an HIV expert at the University of California, San Francisco, who led the trial.…