RNA interference, an ancient defense mechanism that plants and other organisms use to fight off viruses, holds promise as a strategy for treating HIV and other diseases, scientists report. The mechanism "has the potential to revolutionize biology," according to Drs. Moiz Kitabwalla and Ruth M. Ruprecht of the Dana-Farber Cancer Institute in Boston. Their report, "RNA Interference -- A New Weapon against HIV and Beyond," was published in the October 24 edition of the New England Journal of Medicine (2002;347:1364-1367).

In an interview, Dr. Judy Lieberman of the Center for Blood Research in Boston said RNA interference is an "old antiviral strategy" used by plants, worms and other lower species. Small interfering RNA, or siRNA, degrades messenger RNA, the genetic material that translates DNA instructions for making proteins. Researchers have also discovered that RNA interference could work in mammal cells, she said. "We thought it would be a good idea to harness it to combat viral infection, in particular, HIV," said Lieberman, who co-authored a study last summer in which researchers at the Blood Research Center and Massachusetts Institute of Technology used RNA interference to silence messenger RNA on immune cells and HIV itself.

Kitabwalla and Ruprecht say there is a definite need for new strategies to target HIV, since more North Americans are infected with drug-resistant strains. Besides Lieberman's team, they said, two other teams have used RNA interference to fight HIV in the lab.

However, several obstacles need to be overcome before the strategy can be used clinically, the report said. Getting siRNA into cells is an inefficient process, and making sure it remains stable inside cells will be another challenge. If these problems can be solved, "RNA interference has implications far beyond HIV and AIDS," according to Kitabwalla and Ruprecht, who suggest it could be used to target mutant genes in cancer cells and degrade the messenger RNA of other viruses, including the poliovirus. But they cautioned that the approach is "many years from clinical practice." Lieberman noted that some of the obstacles have been overcome in yet-to-be-published studies.

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