Donor IFNL4 Genotype Is Associated with Early Post-Transplant Fibrosis in Recipients with Hepatitis C

Interferon-λ rs12979860 genotype association with liver fibrosis in chronic hepatitis C (CHC) patients in the Pakistani population

Risk and progression of liver fibrosis and cirrhosis in chronic hepatitis C (CHC) patients is significantly influenced by host genetic factors in a polygenic manner. The rs12979860 genetic polymorphism in the interferon-λ3-interferon-λ4 (IFNL3-IFNL4) region has been found to be a major determinant of hepatic inflammatory and fibrotic progression in CHC patients of mainly Caucasian origin; however, it is not known if this association applies to other ethnicities, including Pakistani CHC patients. Here, we genotyped IFNL3-IFNL4 rs12979860 genetic variants in a sample set of 502 Pakistani patients with CHC and used logistic regression analysis to determine its association with the risk and progression of HCV-related fibrosis and cirrhosis. We demonstrate that the rs12979860 major (CC) genotype, despite not determining the risk of stage-specific hepatic fibrosis independently, is associated with a marginally significant risk of liver cirrhosis (OR: 1.64, p = 0.049) after an adjustment for age, gender, body mass index, HCV viral load, and liver enzymes. In a subgroup of CHC patients with sustained ALT levels of <60 IU/L, a more pronounced impact of the IFNL3-IFNL4 rs12979860 major (CC) genotype on advanced liver fibrosis (OR: 4.99, p = 0.017) and cirrhosis (OR: 3.34, p = 0.005) was seen. The present study suggests that IFNL3-IFNL4 rs12979860 polymorphism may also be a significant predictor of hepatic fibrosis and cirrhosis in Pakistani CHC patients, especially in those with normal or near-normal liver enzyme levels.

IFNL4: Notable variants and associated phenotypes. Gene 2019;730:144289. [PMID: 31846709 DOI: 10.1016/j.gene.2019.144289]

Interferon lambda proteins activate the JAK-STAT signalling pathway, resulting in upregulation of genes with antiviral effects. The interferon lambda family was initially thought to be redundant to the interferon alpha family, which signals through the same pathway, except for the more limited expression of the IFNLR1 receptor. However, recent studies show that interferon lambdas uniquely protect tissue barriers against a wide range of important viral infections. The interferon lambda 4 gene (IFNL4) was discovered in 2013. The IFNL4 protein is determined by the IFNL4-ΔG/TT (rs368234815) variant. The ancestral IFNL4-ΔG allele generates IFNL4, whereas IFNL4-TT causes pre-mature termination of the protein. Surprisingly, although interferons are generally antiviral proteins, the genotypes that generate the IFNL4 protein are strongly linked to impaired clearance of hepatitis C virus (HCV). IFNL4 genotype has also been linked to variation within the HCV genome, as well as risk of hepatic fibrosis, certain cancers and some infectious diseases. There has been very strong evolutionary selection against the ancestral IFNL4-ΔG allele, which is the major form in African populations, but the minor allele in Europeans and Asians. The reason for this selection and the biological mechanisms underlying observed phenotypic associations remain to be explained.

Interferon Lambda and Liver Fibrosis

Fibrosis is a highly conserved and coordinated wound healing response to injury. In the liver, injury is promoted by immune effector mechanisms that are common across various disease etiologies and even between organs such as lungs, kidneys, heart, and other organs. Thus, the liver represents a useful model to study inflammation and repair, particularly as it is frequently biopsied in clinical contexts. Currently, strong evidence implicates IFNL3/4 polymorphisms and interferon (IFN)-λ3 levels as determinants of the extent of hepatic inflammation and fibrosis in viral and nonviral liver diseases, as well as in governing the severity of nonhepatotropic viral diseases. Interestingly, IFNL3/4 polymorphisms and IFN-λ3 levels correlate with fibrosis extent in other organs such as the lung and kidney. In this review, we discuss the association between IFN-λ and tissue inflammation and fibrosis in human disease and the potential clinical utility of the findings.

Genetic Factors That Affect Spontaneous Clearance of Hepatitis C or B Virus, Response to Treatment, and Disease Progression

Hepatitis C virus (HCV) and hepatitis B virus (HBV) infections can lead to cirrhosis, end-stage liver disease, and hepatocellular carcinoma. Over the past decade, studies of individuals infected with these viruses have established genetic associations with the probability of developing a chronic infection, risk of disease progression, and likelihood of treatment response. We review genetic and genomic methods that have been used to study risk of HBV and HCV infection and patient outcomes. For example, genome-wide association studies have linked a region containing the interferon lambda genes to spontaneous and treatment-induced clearance of HCV. We review the genetic variants associated with HCV and HBV infection, and how these variants affect specific expression or activities of their products. Further studies of these variants could provide insights into risk factors for and mechanisms of chronic infection and disease progression, as well as new strategies for treatment.