Important note: Information in this article was accurate in 2001. The state of the art may have changed since the publication date.

Reuters NewMedia - Thursday December 13, 2001
Maggie Fox, Health and Science Correspondent

If so, gene therapy could be used to treat one of the most common genetic diseases. But the researchers, who published their findings in the journal Science, said they are a long way from trying the approach in people. Sickle cell disorders are most common in people of African, Mediterranean, Indian and Middle Eastern descent, and one in every 13 African Americans carries the sickle cell gene.

It is recessive, meaning a person has to get two copies of the gene to get the disease, so about one in 450 African-Americans has sickle cell disease.

"It is important to do something," Philippe Leboulch of Harvard Medical School, Brigham and Women's Hospital and Genetix Pharmaceuticals in Boston, Massachusetts, who led the study, said in a telephone interview.

Usually, oxygen is carried to red blood cells by hemoglobin. A protein called beta globin helps.

In sickle cell disease, cells make an abnormal version of hemaglobin, in which the chains of beta globin develop sticky patches, stretching the red blood cell into a characteristic sickle shape. Sickle-shaped cells get stuck in blood vessels and block blood flow, leading to anemia, stroke and organ damage. Leboulch's team designed a new gene that makes normal beta globin, helping to prevent the red blood cells from taking on the sickle shape.

They used a gutted HIV virus to carry the new gene into mice, and the gene produced the needed protein for as long as 10 months -- a long time in gene therapy terms.

"Since we wrote the report we have kept mice that are over a year old and they still express (the gene) at the same levels," Leboulch said. "We really believe that it is permanent."

But getting gene therapy to work in a mouse is different than making it work in human beings, which are 1,000 times bigger.

STEM CELLS AFFECTED

Leboulch said the gene therapy is affecting stem cells in the bone marrow. These are the cells that give rise to all of the blood cells in the body -- red blood cells and the white blood cells of the immune system.

"These are the ones that you really want to target because they are the only ones capable ... of keeping the process going in the individual," Leboulch whose team worked with researchers at the Massachusetts Institute of Technology and the French research institute INSERM, said.

To try this in people, researchers will first have to get more vector -- the virus they used to carry the new gene. Their altered HIV virus worked well but they also have to make sure it cannot somehow turn into a dangerous form in a patient's body.

They would also like to find a way to separate out and grow the patient's own stem cells and use the gene therapy on these, rather than using a lot of virus, because that would be safer for patients. The one gene therapy patient known to have died suffered an over-reaction to the virus used on him.

This work will be done at Genetix, the privately held company Leboulch co-founded with other scientists. Johnson & Johnson is the main shareholder in the company.

Leboulch said the researchers would soon start experimenting with monkeys.
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