The study followed the mice for a relatively short time. In several human cases in which the virus had been believed eliminated, including a Mississippi baby given HIV drugs from an early age, it eventually came back.

Many groups are working toward a cure, said Ambrose, who was not involved in the study. "This is probably one of the most promising studies that have come out, but there's some work that still needs to be done," she said.

Given the effectiveness of the HIV drug therapies now available, she added, "We'd want to make sure the system is as safe as possible before we deliver it to humans."

However, Gendelman noted that the researchers conducted exhaustive testing in their search for remaining virus. "There was no trace of the virus there," he said.

According to estimates by the United Nations, more than 36.7 million people worldwide are infected with the virus, about 1.2 million of them in the United States. Some 5,000 people are newly infected every day around the world.