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Experimental Gene Therapy May Control HIV

Gene-Based Treatment Hopes to Keep HIV in Check Without Drugs
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WebMD Health News
Reviewed by Laura J. Martin, MD

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.

Targeting a Key Gene

The treatment, known as SB-728-T, disrupts the CCR5 gene used by HIV to enter and infect CD4 cells.  

During the procedure, immune system cells are removed from the patient, modified, and reinfused.

The idea is to mimic naturally occurring CCR5 gene mutations that make cells resistant to HIV. The 5% of the population with two copies of the mutant CCR5 gene are basically immune to the virus. The 10% of people with one normal and one mutant CCR5 gene have a slower disease course.

Two studies presented at the meeting involved a total of 15 HIV-infected patients followed for about one year. There were no serious side effects related to the treatment, Mitsuyasu says. Still, long-term side effects are unknown.

In one study, six patients were taken off antiviral medication for 12 weeks after getting the new treatment. HIV levels dropped in three of them, and in one patient, HIV was no longer detectable.

That patient already carried a naturally occurring mutation in one copy of his CCR5 gene. That means that with the gene therapy, the patient had about twice as many gene-modified cells as other patients, Mitsuyasu says.

Indeed, the study showed that the greater the number of cells that carried modified CCR5 genes, the lower the amount of HIV in the blood.

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