AUSTIN, Texas - Researchers at the University of Texas and Stanford University have blocked HIV from invading healthy cells in the laboratory, saying the work could lead to treating patients without drugs.

The scientists knocked out a gene involved in HIV and inserted three genes that help the cells resist the virus in a process they call "targeted stacking." The research was published this week in the journal Molecular Therapy.

The process is three to five years away from being tried in humans and mirrors recent strategies to attack HIV, the precursor to AIDS, at the genetic level. But the UT and Stanford scientists said their method is more precise - and more effective.

It combines two different approaches - using a zinc protein to inactivate an HIV gene and then adding blockers to fight off both types, or strains, of the virus.

These "zinc-finger nucleases" act like "a molecular scissors that can be used to cut out a gene in the human genome, and insert other ones in its place," said Sara Sawyer, a co-author of the study and an assistant professor of molecular genetics and microbiology at UT-Austin. "That is exactly what we did. We cut out a gene that HIV needs, and replaced it with three genes that work to block HIV replication. This makes T-cells virtually resistant to HIV infection, at least in the lab."

Her collaborator at Stanford, Dr. Matthew Porteus, said, "It's like a Reese's Peanut Butter Cup. We're fusing two approaches."

Such gene manipulations represent the next wave of HIV research and "could contribute toward a cure for HIV," said Dr. Paul Spearman, a research professor and vice chairman for research in the Department of Pediatrics at Emory University in Atlanta.

"It's a clever way of enhancing the ability of zinc nucleases in blocking HIV infection," said Spearman, who isn't involved with the UT and Stanford team. "It's a really promising approach."