| Summary: | Peginterferon lambda-1a (Lambda), a type III interferon (IFN), acts through a unique receptor complex with limited cellular expression outside the liver which may result in a differentiated tolerability profile compared to peginterferon alfa (alfa). In Phase 2b clinical studies, Lambda administered in combination with ribavirin (RBV) was efficacious in patients with hepatitis C virus (HCV) infection representing genotypes 1 through 4, and was associated with more rapid declines in HCV RNA compared to alfa plus RBV. To gain insights into potential mechanisms for this finding, we investigated the effects of HCV replication on IFN signaling in primary human hepatocytes (PHH) and in induced hepatocyte-like cells (iHLCs). HCV infection resulted in rapid down-regulation of the type I IFN-α receptor subunit 1 (IFNAR1) transcript in hepatocytes while the transcriptional level of the unique IFN-λ receptor subunit IL28RA was transiently increased. In line with this observation, IFN signaling was selectively impaired in infected cells upon stimulation with alfa but not in response to Lambda. Importantly, in contrast to alfa, Lambda was able to induce IFN-stimulated gene (ISG) expression in HCV-infected hepatocytes, reflecting the onset of innate responses. Moreover, global transcriptome analysis in hepatocytes indicated that Lambda stimulation prolonged the expression of various ISGs that are potentially beneficial to antiviral defense mechanisms. Collectively, these observed effects of HCV infection on IFN receptor expression and signaling within infected hepatocytes provide a possible explanation for the more pronounced early virologic responses observed in patients treated with Lambda compared to alfa.
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