Hepatitis C on Demand

Scientists have found a way to replicate part of the hepatitis C virus (HCV). The achievement, described in today's Science, could help researchers better understand--and possibly find new treatments for--the virus, which infects some 170 million people worldwide and is causing rising rates of liver disease.

HCV cannot be grown reliably in the laboratory, a failing that has slowed critical studies of everything from drugs to vaccines to basic knowledge of the virus's life cycle. "We desperately need a culture system," says Frank Chisari, a leading hepatitis immunologist at The Scripps Research Institute in La Jolla, California.

Researchers aren't there yet, but one group has taken a big step in the right direction. Ralf Bartenschlager and colleagues at the Johannes-Gutenberg University in Mainz, Germany, have engineered a stretch of DNA that contains the mirror image of a portion of HCV's RNA. Bartenschlager injected this "replicon," which codes for HCV's nonstructural proteins but not its core or surface proteins, into human cells. The replicon made copious copies of itself, which the researchers showed both by polymerase chain reaction assays and by analyzing viral proteins.

"It's a groundbreaking study," says Jake Liang of the National Institute of Diabetes and Digestive and Kidney Diseases. But because the replicon does not produce whole viruses and their attendant envelope proteins, researchers cannot use it to determine how HCV infects cells--a critical question that has frustrated all comers. The replicon, however, could become "enormously useful" as a target for testing potential drugs against HCV, says Stanley Lemon of the University of Texas Medical Branch at Galveston.