Sept. 19, 2011 (Chicago) -- Researchers report that they have taken a small step toward developing a gene-based treatment that aims to control HIV without drugs in some patients -- and could lead to a "functional cure."

Researchers say a functional cure may occur when the patient would still be infected with HIV, but no longer needs drugs to control it and prevent disease.

The treatment involves genetically modifying CD4 cells -- immune system cells that are the target of HIV -- so that they are resistant to the virus.

In preliminary research, the new treatment was safe and well tolerated, says researcher Ronald T. Mitsuyasu, MD. Mitsuyasu is director of the University of California, Los Angeles Center for Clinical AIDS Research & Education.

HIV dropped to undetectable levels in one patient, even though he was taken off his usual antiviral medications, he tells WebMD.

"If we can get the immune system to kick in and control the virus without drugs, that's a win," Mitsuyasu says.

However, the treatment did not work as well in five other patients.

The findings were presented here at the 51st Interscience Conference on Antimicrobial Agents and Chemotherapy.