Scientists say they took the immune cells from the patients' own blood, then snipped out a single gene.
When put back in the patient, the cells no longer make a receptor that HIV needs to enter the cell, effectively blocking the virus, The Philadelphia Inquirer reported Thursday.
University of Pennsylvania gene-therapy expert Carl June presented the findings at an AIDS conference in Boston Wednesday, the newspaper said.
June said nine HIV-positive patients had received the novel treatment in Philadelphia, New York, and California.
The engineered cells stayed free of HIV infection in all nine patients and multiplied greatly in eight of them, he said.
June, who has worked on other experimental gene therapies to treat HIV, said the new approach "shows the most promise of any yet tested."
"It's a big accomplishment because this is the first successful attempt at genetic editing," he said. "It gives us an essential tool."