Gene That Combats Flu May Lead to Effective Treatment

A gene that helps fight off influenza infections has been identified in humans, a University of California, Santa Barbara, researcher reported Tuesday.

The gene is the blueprint for a protein, called Mx protein, that blocks the proliferation of the influenza virus in test tubes, biochemist Charles E. Samuel said.

Eventually, “it may prove possible to design agents that can uniquely inhibit the spread of influenza viruses, as well as other viruses,” Samuel said in a statement released by the university.

Influenza kills 20,000 to 40,000 Americans every winter, according to the U.S. Centers for Disease Control in Atlanta. No effective treatment for influenza exists, but the disease can be prevented by vaccines.

Samuel told an international meeting on interferon research in Washington that the Mx protein was produced after the cells were exposed to interferons, a family of antiviral proteins.

Interferons are released by cells when they are infected by a virus, to warn other cells to defend themselves against the virus. They stimulate a complex cascade of reactions inside the cells that inhibit the virus’ reproduction.

When interferons are applied to infected cells in the laboratory, they generally reduce the number of new virus particles formed from an average of a few thousand viruses per cell to less than one per cell.

Even though interferons were discovered 30 years ago and are being studied for the treatment of several viral infections, including AIDS and herpes, “the precise, fine points of their mechanism of action are not known,” said internist David Pizzuti of Hoffmann-LaRoche Inc., of Nutley, N.J. Samuel’s discovery thus may also shed new light on how the interferons work.

Samuel and his colleagues at the University of Zurich in Switzerland and the National Institutes of Health in Bethesda, Md., have found the gene for the Mx protein in both cultured mouse cells and cultured human placenta cells. When they used genetic engineering techniques to introduce the gene into monkey cells grown in the laboratory, they found that it protected the cells from influenza infection.

They do not yet know how it works, however. The protein may itself block viral replication, or it may stimulate formation of some other substance that blocks replication, Samuel said.

Interferon also stimulates the production of other proteins in the cell, Samuel said, and these proteins may inhibit the replication of other viruses. He is now working to identify some of these other proteins.

The new gene and the Mx protein could also have wide use in agriculture, according to Mike Narachi, a product development manager at Amgen Inc. in Thousand Oaks.

“Chickens are highly susceptible to influenza, and it might be possible to boost their resistance by engineering the gene into their eggs so that higher amounts (of the protein) are produced,” he said.