Expression signature of microRNA-155 in hepatitis C virus genotype 4 infection

Hepatits C virus (HCV) genotype 4 (GT4) shows low treatment response rates and discrepancies when compared to other genotypes. However, the reason underlying these discrepancies remains unclear due to the limited number of studies on GT4. microRNA-155 (miR-155) is a noteworthy example of a discrepancy in GT4, as it was found to be upregulated in genotypes 1, 2 and 3 HCV infection, but downregulated in GT4-HCV-infected peripheral blood mononuclear cells (PBMCs). The present study aimed to investigate the expression of miR-155 in PBMCs, serum and liver tissues of GT4-HCV-infected patients. miR-155 expression was assessed using reverse transcription-quantitative polymerase chain reaction in GT4-HCV-infected PBMCs, serum and liver tissues, as well as GT2- and GT4-infected Huh7 cells, and compared to the healthy controls. There was no difference in miR-155 expression observed between naïve GT4-HCV patients and healthy controls in the PBMCs and serum. In HCV-infected liver tissues, however, a significant downregulation was observed. The unique miR-155 expression pattern during GT4 infection was confirmed in the infected Huh7 cell lines when compared to GT2 infection. Clinical data showed a positive correlation between liver transaminases and serum miR-155 expression. In addition, serum miR-155 expression was significantly lower in naïve non-responders (NRs) than naïve sustained virological responders (SVRs), and in post-treatment NRs compared to post-treatment SVRs. In conclusion, miR-155 was not only proven to be a genotype-specific microRNA that is not induced during GT4-HCV infection, but also a good prognostic factor and predictor of response to treatment enabling a non-invasive differentiation between NRs and SVRs during GT4-HCV infection.