Gene Therapy May Hold Key to Treating Hepatitis B

Gene therapy that targets liver cells can halt hepatitis B infection in mice, a new study shows. Researchers targeted the strands of RNA that the hepatitis virus latches onto when it infects a cell, said Dr. Mark A. Kay, a Stanford professor of pediatrics and genetics. Once the virus locks onto a cell's RNA, it can commandeer the cell's reproductive machinery and turn it into a factory for making new virus copies. Hepatitis B infection can be prevented through immunization, while treatment is of limited effectiveness for those who are not immunized and become infected with the virus.

Kay and colleagues created a bit of genetic material that is the mirror image of the RNA onto which hepatitis locks, essentially forming a unit that the virus can no longer latch onto. This gene-silencing technique is known as RNA interference. "It's as if you've taken a scissors and cut out only those sequences that are related to hepatitis B," Kay said. "So basically, you're short circuiting the life cycle of the virus."

The researchers delivered the gene therapy by attaching it to a benign virus that infected mouse liver cells. The therapy cut the levels of hepatitis virus by 84.5 percent in mice, researchers reported.

Much safety testing still needs to be done before the therapy can be tried in human beings, Kay said. "But I'm cautiously optimistic," he added. "This is the first time I've been really excited about taking a potential therapy for hepatitis and bringing it to clinical trials." The full report, "Inhibition of Hepatitis B Virus in Mice by RNA Interference," was published May 12 in the advance online edition of Nature Biotechnology (2003;10.1038/nbt824).

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