An estimated 170 million individuals worldwide harbor the lethal hepatitis C virus (HCV)--most without even knowing it. Indeed, the virus often resides in the body undetected for years before it ultimately causes advanced liver disease. Efforts to study HCV have been hampered by the virus's unwillingness to grow in the lab. The results of a new study, however, promise to change that. According to a report published today in the journal Science, Charles M. Rice of Rockefeller University and his colleagues have discovered that certain HCV strains contain mutations in a particular region of a protein known as NS5A that allow the virus to replicate more freely in cell culture. Taking advantage of that, the team developed a culture system that should enable researchers to conduct genetic analyses of the virus and test drug compounds more rapidly in the near future. Moreover, the region of NS5A that appears to be so critical for replication may itself represent a good drug target. "This is a major breakthrough for genetics studies on the virus and for designing ways to screen for effective drugs," Rice says. "This could really speed up the drug discovery process."