California: Scientists Tout Stem Cells' Use to Battle HIV

Together with Ronald Mitsuyasu, a University of California-Los Angeles researcher and HIV/AIDS specialist, UCLA virologist Jerome Zack is working on a way to insert a gene into bone marrow stem cells that could either protect the cells from HIV or deactivate virus already in the cells. The effort would replace a gene that is vulnerable to HIV with synthetically engineered DNA designed to seek and destroy the virus. The DNA fragment, called a ribozyme, is programmed to bind to HIV and cut it into harmless halves.

Zack presented his research in San Francisco Wednesday before the Independent Citizens' Oversight Committee, the 27-member group created under Proposition 71 to guide California's stem cell research program.

Recently, Mitsuyasu completed a clinical trial of the treatment's safety. No problems were reported with the 10 trial patients, and after three years, HIV-resistant blood cells could still be detected. He is currently enrolling more subjects.

Trial participants first receive a growth factor that stimulates bone marrow stem cells to enter the bloodstream. Blood is drawn, and the patients' own stem cells are isolated. A harmless modified virus related to HIV is used to insert the gene into the cells. Thus enhanced, the stem cells are returned to the bloodstream, where they make all the different types of blood cells, each of which will have the new anti-HIV gene.

The method can initially protect about 10 percent of patients' stem cells, but this percentage increases as HIV kills the vulnerable cells while protected cells replicate. To accelerate the process, six months later the patients stop taking anti-virals for four weeks to give HIV the opportunity to kill some unprotected blood cells; this puts pressure on the protected cells to replicate more quickly and replace the killed cells. Twelve weeks later, the patients go off medication for at least eight weeks, or longer, depending on how well the strategy is working. The trial will be completed in about a year and a half.

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