The Mississippi child is now two-and-a-half years old and has been off medication for about a year with no signs of infection.
More testing needs to be done to see if the treatment would have the same effect on other children.
But the results could possibly lead to a cure for children with HIV.
If the girl stays healthy it would be only the world's second reported cure.
Dr Deborah Persaud, a virologist at Johns Hopkins University in Baltimore, presented the findings at the Conference on Retroviruses and Opportunistic Infections in Atlanta.
"This is a proof of concept that HIV can be potentially curable in infants," she said.