Modified AIDS Virus Is Utilized for Blood-Cell Disorder in Mice

Massachusetts researchers successfully used a modified form of the AIDS virus, carefully stripped of potentially harmful components, to cure sickle-cell anemia in mice. The gene therapy work, published in today's issue of Science (Vol. 294; No. 5550), used a form of the AIDS virus to deliver a therapeutic gene to the bone marrow, where blood cells are made. The same method has potential for treating several hundred blood-cell disorders, including leukemia.

The use of the AIDS virus will require careful scrutiny before it is tried in humans. The method used by researchers at Harvard University and the Massachusetts Institute of Technology could be ready for human testing in about three years, according to Genetix Pharmaceuticals Inc., a closely held Cambridge, Mass., company that aims to commercialize the procedure.

To test the technique, scientists removed bone marrow from mice and inserted a gene that helps blood cells keep their normal shape. They used radiation to kill diseased cells remaining in the bone marrow, then put the treated cells back into the mice. When scientists examined the animals' blood after the therapy, they found a high percentage of normal, round blood cells and very few sickle cells, said senior author Dr. Philippe Leboulch, an assistant professor at Harvard Medical School. The treated mice also showed healthy weight and none of the fatigue characteristic of the disease in mice and humans, he said. The positive effects lasted as long as 10 months.

Leboulch, who has been unsuccessfully trying to insert the therapeutic genes in mice for years, said the secret is the powerful ability of the AIDS virus to carry a large therapeutic gene and effectively insert it into the cells' normal genetic material. The modified AIDS virus is "the single best thing we've seen in gene therapy for years," he said. Normally, viruses similar to that which causes the common cold are used, but they are not as good at worming their way into the nuclei of cells, where genes are stored. But Leboulch, who co-founded Genetix, said it will take a lot of work to convince government regulators that the AIDS virus can be used successfully.

As the gene therapy method gains credence, scientists are also working competitively to overcome one major obstacle of using it in humans: how to get rid of all the defective cells. The radiation method used in mice would likely prove too dangerous in humans. Researchers are looking at various alternatives, including drug therapy designed to kill the damaged cells but not the gene-treated ones.

Back to other CDC news for December 14, 2001

Previous Updates