Experimental Drugs Block Hepatitis C Virus

New experimental compounds may help the body fight off hepatitis C, researchers said Thursday. The research, done by separate teams in the United States and Canada, also led to new discoveries about how the body fights off infection.

While viruses such as influenza are eventually cleared by the immune system, hepatitis C can stay in the body permanently, eluding the immune system's various weapons. According to CDC, 75 percent to 85 percent of those infected have chronic hepatitis C infection. Many will develop liver damage, sometimes leading to cirrhosis and liver cancer. The antiviral ribavirin, used with alpha interferon, can help some patients control hepatitis C but does not cure it.

"Just a year ago, the hepatitis C virus field had no leads," said Michael Gale, a virologist at the University of Texas Southwestern Medical Center in Dallas who led one of the studies. "We were totally clueless." Gale's team and a team led by John Hiscott at McGill University in Montreal found out how the virus de-activates cell defenses so it can stay in a cell virtually forever. The full reports were published in the online journal Science Express (April 17, 2003; 10.1126/science.1082604) and in the Journal of Virology (2003;77:3898-3912).

Both teams said they found that the virus can block a cell's production of interferon regulatory factor 3 (IRF3), which cells produce to defend against infection and to summon more immune system help. The McGill team also found it blocks a second compound, IRF7.

"This really gives us the first evidence of how it is the virus can cause lifetime infection, as opposed to influenza which infects you for a week," Gale said in an interview. Gale's team also discovered that individual cells have their own immune responses. "The whole thing works by IRF3 turning on genes in the human cell that fight off infection. We are going to find out what those genes are, what their products are," Gale said. This, in turn, could lead to new ways to battle viruses from HIV to herpes.

In the meantime, Schering-Plough and Boehringer Ingelheim have developed compounds they hope will work against hepatitis C. Gale's team tested the experimental Schering product, SCH-6, and found it could protect the cell's defenses. "We found that the new protease inhibitors could actually prevent the virus from blocking this immune response and basically restore the innate antiviral response in human cells," Gale said.

The work reported in Science Express was all done in the laboratory; Gale said the drugs will be difficult to test because no animals are naturally infected with hepatitis C the way humans are. However, Boehringer has reported on Phase I clinical trials that suggest its protease inhibitor is safe and may greatly reduce viral levels in the body.

Back to other CDC news for April 25, 2003

Previous Updates