The San Francisco Chronicle on Friday examined an ongoing clinical trial that combines components of genetic engineering, gene therapy and stem cell research to develop a "parallel immune system" for HIV-positive people. More than 70 HIV-positive people are participating in the study -- led by Ronald Mitsuyasu, director of the University of California-Los Angeles' Center for Clinical AIDS Research and Education -- half of whom received their own blood cells fortified with a gene that blocks HIV, and half of whom received a placebo at the start of the trial. According to the Chronicle, the trial seeks to develop fortified blood cells that will block HIV infection of individual cells and eventually outlast natural blood cells so the patient "would be left with a rebuilt immune system resistant to HIV."
The "secret" of the experimental gene therapy method to controlling HIV is a "custom-built" version of an enzyme called a ribozyme, developed by Australian researchers, that cuts up one of the virus's nine genes when it attempts to replicate, the Chronicle reports. Because the body does not naturally produce the ribozyme, researchers began using stem cells -- specifically those found in bone marrow and the bloodstream -- to manufacture the enzyme. The type of stem cell -- which is known as "the mother of all blood cells" because it develops into "the many kinds of white cells that fight infection" -- is often a "target" of HIV, the Chronicle reports. To transfer the fortified cells into the body, participants in two, eight-hour sessions are connected to a machine that filters stem cells from their blood and then returns the blood. In the laboratory, a mouse virus engineered to carry the ribozyme gene -- which "tell[s] the cell[s] how to make the enzyme" -- is injected into the cells. After three days participants' own stem cells, containing the ribozyme gene, are injected back into their body. In the following weeks, the stem cells produce white blood cells containing the ribozymes.
Mitsuyasu said he does not think this treatment will become a substitute for antiretroviral drugs. However, "if we are intelligent in how we use the drugs with these immune therapy approaches, it could lead to extremely effective control of HIV," he said. The trial's preliminary results are expected to be ready in February 2007. UCLA and a research company in Sydney, Australia, owned by Johnson & Johnson currently are conducting similar trials (Russell, San Francisco Chronicle, 4/7).
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