[84] Similarly, most of other investigators have indicated less marked association between the expression of ISGs in PBMCs and treatment find more outcomes, or IL28B genotype in comparison with in liver of the same patients.[80, 86] Thus, although there are several reports about the association between ISGs in liver or PBMCs and IL28B genotype or response to IFN therapy, the biological pathways linking IL28B genetic variants to spontaneous and/or treatment-induced HCV clearance remain unknown. However, recent reports suggest some possible scenarios. Using primary human hepatocytes or chimpanzee, Thomas et al. found that type III but not type I IFNs are primarily induced after HCV infection and

that their degree of induction

is closely correlated with the levels of ISGs.[87] These results strongly suggest that hepatic IFN-λ production may have important roles and could be a principal driver of ISG induction in response to HCV infection. On the other hand, in chronically HCV-infected chimeric mouse model that have the characteristic of immunodeficiency, larger amounts of IFN-λs on HCV-infected human hepatocytes were produced in liver with a favorable IL28B genotype on treatment with IFN-α.[88] However, no significant differences in HCV-RNA reduction related to IL28B variants were observed because of the lack of intrinsic immune cells in the model. In contrast, Zhang et al. and Yoshio et al. reported that a certain subset Decitabine nmr of dendritic cells (DCs) within human PBMCs could recognize HCV and produce large amounts of IFN-λs.[89, 90] The ability of production of IFN-λ3 was superior in subjects with a favorable IL28B genotype.[90] Moreover, IFN-α directly affected DC function and significantly increased IFN-λ production.[89] Based on these findings, it is tempting to speculate that exogenous IFN-α would increase IFN-λ production by DCs and/or HCV-infected hepatocytes during IFN-α therapy, and this Oxalosuccinic acid could provide a potential explanation as to why

IL28B genetic variants predict the outcome of IFN-α therapy (Fig. 1). Recently, Olsson et al. performed RNA sequencing in primary human hepatocytes activated with synthetic double-stranded RNA to mimic HCV infection. They discovered that a new transiently induced region that harbors a dinucleotide variant ss469415590 (TT or ΔG) was strongly associated with HCV clearance. The ss469415590 polymorphism is located upstream of IL28B and is in high-linkage disequilibrium with rs12979860. The ss469415590 ΔG allele is a frameshift variant that creates a novel gene, designated IFNL4, encoding the type III IFN-λ4 protein, which is fairly similar to IFN-λ3. Interestingly, compared with rs12979860, ss469415590 is more strongly associated with spontaneous and treatment-induced HCV clearance in individuals of African ancestry, whereas it did not improve prediction among Caucasians and Asians.