Natural killer inhibitory receptor expression associated with treatment failure and interleukin-28B genotype in patients with chronic hepatitis C

The adverse pharmacology of calcineurin inhibitors and their impact on hepatitis C recurrence after liver transplantation: implications for clinical practice

Calcineurin inhibitors are widely used as maintenance immunosuppressants in solid-organ transplantation to minimize the risk of allograft rejection. Although the use of these agents has transformed the outcomes for patient and graft survival, this has come at a cost, notably the well-known adverse events of nephrotoxicity and metabolic abnormalities, to name a few. Over the last decade, tremendous interest has also focused on the impact of these medications on the replication of hepatitis C virus (HCV), with cyclosporine in particular having a negative effect on viral replication in vitro. Although small retrospective studies suggested that there may be a beneficial effect with cyclosporine on the progression of recurrent HCV and response to interferon, these findings have not been validated in several well-designed randomized controlled trial studies. The authors will review the pharmacology and pharmacokinetics of these well-known drugs and discuss the impact of these medications on the natural history of HCV recurrence after liver transplantation.

Dysregulation of innate immunity in hepatitis C virus genotype 1 IL28B-unfavorable genotype patients: impaired viral kinetics and therapeutic response

Recent studies have shown that a single-nucleotide polymorphism upstream of the interleukin-28B (IL28B) gene plays a major role in predicting therapeutic response in hepatitis C virus (HCV)-infected patients treated with pegylated interferon (PEG-IFN)/ribavirin. We sought to investigate the mechanism of the IL28B polymorphism, specifically as it relates to early HCV viral kinetics, IFN pharmacokinetics, IFN pharmacodynamics, and gene expression profiles. Two prospective cohorts (human immunodeficiency virus [HIV]/HCV-coinfected and HCV-monoinfected) completing treatment with IFN/ribavirin were enrolled. Patients were genotyped at the polymorphic site rs12979860. In the HIV/HCV cohort, frequent serum sampling was completed for HCV RNA and IFN levels. DNA microarray of peripheral blood mononuclear cells and individual expression of IFN-stimulated genes (ISGs) were quantified on IFN therapy. The IL28B-favorable (CC) genotype was associated with improved therapeutic response compared with unfavorable (CT or TT) genotypes. Patients with a favorable genotype had greater first- and second-phase viral kinetics (P = 0.004 and P = 0.036, respectively), IFN maximum antiviral efficiency (P = 0.007) and infected cell death loss (P = 0.009) compared with unfavorable genotypes. Functional annotation analysis of DNA microarray data was consistent with depressed innate immune function, particularly of natural killer cells, from patients with unfavorable genotypes (P <0.004). Induction of innate immunity genes was also lower in unfavorable genotypes. ISG expression at baseline and induction with IFN was independent of IL28B genotype.

CONCLUSION

Carriers of the IL28B-favorable genotype were more likely to have superior innate immune response to IFN therapy compared with unfavorable genotypes, suggesting that the unfavorable genotype has aberrant baseline induction of innate immune response pathways resulting in impaired virologic response. IL28B genotype is associated with more rapid viral kinetics and improved treatment response outcomes independent of ISG expression.

Host genomics and HCV treatment response

In 2009, an association between the interleukin-28B (IL28B) polymorphism and treatment outcome for genotype 1 (G1) hepatitis C virus (HCV) infection, as well as spontaneous clearance of HCV, was reported. Since the initial publications, over 100 articles have appeared in the peer-reviewed literature, with many more manuscripts in press and abstracts presented at scientific meetings. Despite the proliferation of data concerning the IL28B polymorphism and HCV infection, there remain many critical unanswered questions about clinical implications and the underlying biological mechanisms. In this review, we discuss the basic principles of genome-wide association study methodologies that are important for interpreting the results of genetic association studies. We then review the current literature concerning the association between IL28B variants and interferon (IFN) treatment response in patients with chronic HCV infection, as well as spontaneous HCV clearance. We consider the relevance of the IL28B polymorphism to non-G1 HCV, as well as the special treatment populations of HIV/HCV co-infection and recurrent HCV post-liver transplantation. We review current knowledge of the biological mechanisms underlying this genetic association, including the link to liver IFN-stimulated gene expression, and identify continuing gaps in our knowledge and key research priorities. Finally, pegylated-IFN and ribavirin is no longer the standard of care for the treatment of G1 HCV, and we conclude by considering the relevance of IL28B polymorphisms in the era of direct-acting antivirals.