Study Touts AIDS Virus for Gene Therapy

The same characteristics that make the AIDS virus such a cunning and effective killer may make it ideal as a medical tool for gene therapy, new research indicates.

In Friday’s issue of the journal Science, a team from the Salk Institute in La Jolla and the Whitehead Institute for Biomedical Research in Cambridge, Mass., shows that certain slow-acting viruses such as the human immunodeficiency virus that causes AIDS can be exploited to change the genetic content of cells that are difficult or impossible to target by conventional gene therapy.

To replace defective genes or supply missing ones in their patients, gene therapists often employ viruses as the vehicle (or “vector”) because they are notoriously talented at hijacking healthy cells and inserting viral genes in place of the cells’ normal genetic material.

Scientists splice the desired human genes into a modified form of the virus, infect the human subject and wait for the virus to rearrange the cells’ genetic code. Although promising, this technique has proven largely disappointing so far.

One reason is that most of the viruses used only affect cells while they are in the process of dividing. Many cells in the body--including neurons, “stem” cells that produce various kinds of blood components, liver cells and muscle fibers--never divide once they are mature. Those cells can be removed from the body, chemically induced to reproduce, genetically altered while dividing and then returned to the patient. But that elaborate process “can be done to [comparatively] few cells,” said lead author Inder Verma of Salk, “and very often it damages the cells.”

What is needed instead, Verma said, is a vector that can inject its genes into cells that aren’t dividing--and do so entirely within the body.