Serum microRNA-122 kinetics in patients with chronic hepatitis C virus infection during antiviral therapy

The levels of the liver-specific microRNA-122 (miR-122) circulating extracellularly in the blood have been shown to be increased upon liver damage. However, it is unknown if the levels of serum miR-122 are altered during antiviral therapy and reflect the therapeutic success. Here, we investigated miR-122 serum levels in patients with chronic hepatitis C virus (HCV) genotype 1 infection during antiviral therapy with pegylated interferon and ribavirin. Therefore, sera from 60 patients with chronic HCV infection genotype 1 showing sustained virological response (SVR), non-response or relapse to therapy obtained at baseline, 4, 12, 24 weeks, end of treatment and follow-up were analysed retrospectively for miR-122 content by quantitative real-time reverse transcription PCR. The time courses of miR-122 were correlated with HCV RNA as well as standard liver parameters. We found that while there was no relation between serum miR-122 and HCV RNA levels at baseline, the decline in HCV RNA upon beginning of the therapy closely correlated with the reduction of serum miR-122 in the three different patient groups. Moreover, the serum miR-122 level correlated well with alanine aminotransaminase, a marker of ongoing liver damage. At follow-up serum miR-122 levels remained low in SVR, but increased to baseline levels in patients not responding or showing relapse to therapy. In contrast, the serum concentration of the ubiquitously expressed miR-16 did not change during therapy. We conclude that the serum level of miR-122 well reflects the success of interferon/ribavirin therapy in patients with chronic HCV infection.

Modulation of replication efficacy of the hepatitis C virus replicon Con1 by site-directed mutagenesis of an NS4B aminoterminal basic leucine zipper

The hepatitis C virus (HCV) nonstructural protein 4B (NS4B) is assumed to function as a membrane anchor and protein hub for the viral replication complex. The aim of the current work was to modulate HCV replication efficacy in the subgenomic Con1 replicon by mutations of specific sites within the aminoterminal-located basic leucine zipper (bZIP), a candidate motif for protein-protein interactions involving NS4B. Mutational sites and amino acid substitutes were determined by in-silico sequence analyses of the NS4B-bZIP motif in 357 isolates of HCV genotype 1b from the euHCVdB and LosAlamos database and consecutive analysis of conserved physico-chemical properties at bZIP specific positions. Mutants with predicted minor, medium or major reduction of replication efficacy were tested in the pFKI389neo/NS3-3'/ET plasmid replicon model. Four sites (L25, T29, V39 and W43) of crucial importance for bZIP-mediated protein interaction with predicted apolarity of respective amino acid positions were selected for mutational studies. Substitutes with physico-chemical properties matching the predicted requirements either well (T29A), moderately (L25W, V39W), or insufficiently (T29E, W43E) were associated with slightly improved, moderate and marked decreased replication efficacy, respectively. Spontaneous (T29G) and adaptive (A28G, E40G) mutations occurred in the T29E mutation isolate only and were associated with marked reduction of replication efficacy. The bZIP motif region of NS4B is crucial for RNA replication in the subgenomic Con1 replicon system. RNA replication efficacy can be modulated by site-directed mutagenesis at specific bZIP functional sites. New adaptive amino acid mutations were identified within the HCV NS4B protein.