Hepatitis C virus (HCV), a positive stranded RNA virus, is the main causative agent of post-transfusion and sporadic non-A non-B hepatitis worldwide. Paired samples of plasma and peripheral blood mononuclear cells (PBMC) from 11 patients with chronic hepatitis C treated with alpha-interferon (IFN) were tested, using a single step polymerase chain reaction (PCR), for the presence of HCV RNA. Before treatment, the viral genome was detected in all the plasma samples and 81.8% of PBMC. After 3 months of treatment, HCV RNA was still present in 63.6% of plasma samples but in only 27.3% of PBMC. A good correlation was observed between serum alanine aminotransferase level normalisation and disappearance of the viral genome in plasma. Among the six responder patients, five relapsed shortly after IFN withdrawal; HCV RNA became detectable again, especially in PBMC. These results show the presence of HCV in PBMC from most patients infected chronically. IFN therapy had an inhibitory effect on viral replication in lymphoid cells, but frequent relapses observed after cessation of treatment with IFN suggested persistence of HCV in these cells.

Among 47 blood donors tested positive with HCV EIA 2.0 Abbott, 27 (57.4%) also reacted with four ¿third-generation' EIAs. The presence of anti-HCV antibodies was confirmed with 3 different immunoblot assays in 16 of 27 sera (34.0%) while 10 samples (21.3%) had indeterminate profile with antibodies usually directed against structural core antigen. Anti-HCV core IgM response was found in 12 of 47 sera (25.5%) and HCV viremia detected by the polymerase chain reaction (PCR) procedure was observed in 15 samples (31.9%). A comparative study of the different markers confirmed a good correlation between a strong antibody response in EIAs and immunoblot assays and the presence of HCV RNA in the serum; only 2 immunoblot indeterminate samples were PCR positive. An association was observed between IgM antibodies against "core' epitopes and HCV RNA carriage: all IgM-positive sera were found positive by PCR. However, the direct detection of viral genome remains the best method for identifying HCV carriers in the blood donor population.