April 25, 2003
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.
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.
04.17.03; Maggie Fox