Response to interferon of GB virus C and hepatitis C virus in patients with chronic hepatitis.

Objectives: To evaluate the response to interferon and capacity to induce liver disease of a putative non-A to E hepatitis virus designated GB virus C (GBV-C). Methods: RNA of GBV-C was detected by reverse transcription polymerase chain reaction with nested primers deduced from the 5'-noncoding region. It was titrated, along with RNA of hepatitis C virus (HCV), in 16 co-infected patients (11%) out of 140 patients who received interferon. Results: At the completion of a 6-month course of interferon (total dose: 516-774 million units), GBV-C RNA disappeared from serum in seven (44%) and HCV RNA from serum in 11 (69%) patients. At 6 months after interferon treatment ended, GBV-C RNA remained cleared in three patients (19%), and HCV RNA was persistently undetectable in four (25%). One patient lost both GBV-C and HCV RNAs. The three patients whose serum was cleared of GBV-C RNA had pretreatment titers of the virus (two with 10 1 /ml and one with 10 2 /ml) that were considerably lower than the titers of 13 patients (one with 10 2 /ml, eight with 10 3 /ml, and four with < 10 4 /ml) without such clearance. The decrease in alanine aminotransferase levels paralleled the response of HCV RNA but not that of GBV-C RNA to interferon. The response of HCV at 6 months after interferon in the co-infected patients (4/16 or 25%) did not differ significantly from that in patients without GBV-C infection (44/ 124 or 35%). Conclusions: The sensitivity of GBV-C to interferon is comparable to but independent of HCV. Co-infection with GBV-C does not influence the response to interferon of patients with chronic hepatitis C.