Genotype rs8099917 near the IL28B gene and amino acid substitution at position 70 in the core region of the hepatitis C virus are determinants of serum apolipoprotein B-100 concentration in chronic hepatitis C

Chronic hepatitis C virus infection and lipoprotein metabolism

Hepatitis C virus (HCV) is a hepatotrophic virus and a major cause of chronic liver disease, including hepatocellular carcinoma, worldwide. The life cycle of HCV is closely associated with the metabolism of lipids and lipoproteins. The main function of lipoproteins is transporting lipids throughout the body. Triglycerides, free cholesterol, cholesteryl esters, and phospholipids are the major components of the transported lipids. The pathway of HCV assembly and secretion is closely linked to lipoprotein production and secretion, and the infectivity of HCV particles largely depends on the interaction of lipoproteins. Moreover, HCV entry into hepatocytes is strongly influenced by lipoproteins. The key lipoprotein molecules mediating these interactions are apolipoproteins. Apolipoproteins are amphipathic proteins on the surface of a lipoprotein particle, which help stabilize lipoprotein structure. They perform a key role in lipoprotein metabolism by serving as receptor ligands, enzyme co-factors, and lipid transport carriers. Understanding the association between the life cycle of HCV and lipoprotein metabolism is important because each step of the life cycle of HCV that is associated with lipoprotein metabolism is a potential target for anti-HCV therapy. In this article, we first concisely review the nature of lipoprotein and its metabolism to better understand the complicated interaction of HCV with lipoprotein. Then, we review the outline of the processes of HCV assembly, secretion, and entry into hepatocytes, focusing on the association with lipoproteins. Finally, we discuss the clinical aspects of disturbed lipid/lipoprotein metabolism and the significance of dyslipoproteinemia in chronic HCV infection with regard to abnormal apolipoproteins.

Assessment of the features of serum apolipoprotein profiles in chronic HCV infection: difference between HCV genotypes 1b and 2

BACKGROUND

The life cycle of hepatitis C virus (HCV) is tightly associated with host lipoprotein metabolic pathways. Apolipoprotein is present on the outer surface of lipoprotein particles and plays an important role in lipoprotein metabolism. We aimed to elucidate the influence of chronic HCV infection on serum apolipoprotein profiles.

METHODS

Fasting serum apolipoprotein profiles of 310 subjects with active or cleared HCV infection were examined. Subsequently, the association between chronic HCV infection and serum apolipoprotein levels was determined using multiple regression analysis.

RESULTS

Active HCV infection was associated with high serum levels of apo A-II and low serum levels of apo C-II and C-III. HCV infection with both genotype 1b (G1b) and genotype 2 (G2) was associated with low serum levels of either apo C-II and C-III, whereas only HCV G1b infections caused elevated levels of apo A II and E. Among active HCV infections, HCV G1b was associated with an elevation in the serum apo E levels. Furthermore, IL28B non-major genotype (rs8099917 TG/GG) was associated with low levels of serum apo B and high levels of apoA-II, and advanced fibrosis was associated with low levels of apo B and C-II in G1b infection.

CONCLUSIONS

Active HCV infection is distinctively associated with characteristic serum apolipoprotein profiles. The influence on apolipoprotein profiles varies with different HCV genotypes. Moreover, the genotype of IL28B and hepatic fibrosis affected serum apolipoproteins in G1b infection. Abnormalities in serum apolipoproteins may provide a clue to the elucidation of complex interactions between active HCV infection and lipid metabolism.

Core amino acid variation at position 110 is associated with sustained virological response in Caucasian patients with chronic hepatitis C virus 1b infection

The aim of this study was to analyze the impact of core variations on sustained virological response (SVR) to pegylated interferon plus ribavirin (PEG-IFN/RBV) and its association with predictive factors of response in Caucasian patients infected with genotype 1 hepatitis C virus (HCV-1). Full-length core sequences were analyzed in 100 Caucasian HCV-1-infected patients who received therapy with PEG-IFN/RBV. The associations between variations in the core protein and SVR, as well as with predictors of SVR, were analyzed. Variations at core 62, 70 and 110 were selected as candidates. There were almost no variations at these positions among patients harboring HCV-1a. However, they were identified in 10 (30.3 %), 21 (63.6 %) and 13 (39.4 %) subjects with HCV-1b, respectively. Among the HCV-1b patients, 39.1 % individuals carrying core R62 and 70 % subjects with core R62G showed SVR (p = 0.141), and 66.7 % of HCV-1b patients harboring core R70 and 38.1 % with core R70Q achieved SVR (p = 0.157), whereas the rate of SVR was 70 % for individuals with core T110 and 15.4 % for those with core T110N (p = 0.004). No statistical interaction between core variations and IL28B genotype was observed. Patients with R70 showed higher median (interquartile range) baseline plasma levels of low-density-lipoprotein cholesterol (LDL-C) than those with R70Q (96 [86-118] mg/dL vs. 76 [54-88] mg/dL, p = 0.014). We concluded that a substitution at core 110 is associated with a lower rate of SVR in Caucasian HCV-1b-infected patients receiving PEG-IFN/RBV. Furthermore, the variation at the core 70 position is related to plasma levels of LDL-C in these patients.

Serum apolipoprotein B-100 concentration predicts the virological response to pegylated interferon plus ribavirin combination therapy in patients infected with chronic hepatitis C virus genotype 1b

Host lipoprotein metabolism is associated closely with the life cycle of hepatitis C virus (HCV), and serum lipid profiles have been linked to the response to pegylated interferon (Peg-IFN) plus ribavirin (RBV) therapy. Polymorphisms in the human IL28B gene and amino acid substitutions in the core and interferon sensitivity-determining region (ISDR) in NS5A of HCV genotype 1b (G1b) were also shown to strongly affect the outcome of Peg-IFN plus RBV therapy. In this study, an observational cohort study was performed in 247 HCV G1b-infected patients to investigate whether the response to Peg-IFN and RBV combination therapy in these patients is independently associated with the level of lipid factors, especially apolipoprotein B-100 (apoB-100), an obligatory structural component of very low density lipoprotein and low density lipoprotein. The multivariate logistic analysis subsequently identified apoB-100 (odds ratio (OR), 1.602; 95% confidence interval (CI), 1.046-2.456), alpha-fetoprotein (OR, 0.764; 95% CI, 0.610-0.958), non-wild-type ISDR (OR, 5.617; 95% CI, 1.274-24.754), and the rs8099917 major genotype (OR, 34.188; 95% CI, 10.225-114.308) as independent factors affecting rapid initial virological response (decline in HCV RNA levels by ≥3-log10 at week 4). While lipid factors were not independent predictors of complete early or sustained virological response, the serum apoB-100 level was an independent factor for sustained virological response in patients carrying the rs8099917 hetero/minor genotype. Together, we conclude that serum apoB-100 concentrations could predict virological response to Peg-IFN plus RBV combination therapy in patients infected with HCV G1b, especially in those with the rs8099917 hetero/minor genotype.

Hepatitis C virus infection alters lipid metabolism depending on IL28B polymorphism and viral genotype and modulates gene expression in vivo and in vitro

Hepatitis C virus (HCV) interacts with lipid receptors to enter the cell, circulates as lipoviroparticle and is secreted as VLDL. We aimed to investigate the role of the rs12979860 polymorphism in the IL28B gene in 143 with chronic hepatitis C genotype 1, 144 infected with genotype 3, 90 genotype 4 and 413 noninfected individuals on lipid profile and to test the impact of HCV infection in an in vitro model on VLDL biosynthesis-related gene expression rs12979860 polymorphism was analysed using real-time PCR coupled to Fluorescence Resonance Energy Transfer (FRET). Huh7.5 (rs12979860 CT) and Huh7 (genotype CC) cells were infected with JFH-1 particles and serum from patients infected with genotypes 1 and 3. Gene expression of apolipoprotein B (apoB), microsomal triglyceride transfer protein (MTP), acetyl CoA carboxylase (ACC), diacylglycerol acyltransferase 2 (DGAT2), diacylglycerol acyltransferase 1 (DGAT1) and low-density lipoprotein receptor (LDLr) genes were determined by semiquantitative RT-PCR in vivo and in vitro. Genotype CC rs12979860 polymorphism was associated with significantly higher serum LDL and total cholesterol levels in patients with hepatitis C genotype 1 but not in patients with hepatitis C genotype 3, genotype 4 and control (noninfected) population. Genotype CC was more often seen in genotype 3 and healthy people in comparison with genotype 1; P = 0.001. In vitro results showed that HCV infection promotes lipid metabolism gene expression induction depending on viral genotype, but to a lesser extent in cells with CT genotype. These results demonstrate that IL28B genotype influences lipid metabolism in patients with hepatitis C but not in noninfected and it seems to be viral genotype-mediated. HCV infection modifies lipid-related genes expression (DGAT1 and DGAT2) in cultured cells based on viral genotype and IL28 polymorphism.

Polymorphism Near the Interleukin-28B Gene and Anti-Hepatitis C Viral Response

In a recent genome-wide association study, single nucleotide polymorphisms (SNPs) located near the interleukin-28B gene (IL28B), which encodes type III interferon (IFN) λ3, were shown to be strongly associated with a viral response to pegylated IFNα (PEG-IFNα) and ribavirin (RBV) combination therapy and spontaneous viral clearance in patients chronically and acutely infected with hepatitis C virus (HCV), respectively. The global distribution of allele frequencies shows a remarkable pattern, in which a favorable allele is nearly fixed in East Asia, has an intermediate frequency in Europe, and is least frequent in Africa. Although the underlying mechanisms responsible for viral responses associated with IL28B SNPs have not been completely elucidated, IFN-stimulated gene expression in patients with unfavorable IL28B genotypes tends to be high at baseline and is insufficiently induced by exogenous IFN administration, resulting in poor treatment outcomes. Clinically, triple therapy with PEG-IFNα/RBV together with direct-acting antiviral agents (DAAs) is currently used to treat chronic hepatitis C as a first-line therapy. Although the predictive power of IL28B status may be attenuated, the IL28B genotype will remain relevant to the outcomes of DAA therapy when used in combination with PEG-IFNα as a backbone. Even with the introduction of IFN-free therapies with a new class of highly effective DAAs, IL28B SNPs are still useful predictors of treatment outcomes and can be used to individualize treatment strategies to maximize cost-effectiveness and identify patients at risk of being refractory to treatment. This review summarizes the current understanding of the clinical significance and role of IL28B in HCV infection and response to therapy.

Serum lipoprotein profiles and response to pegylated interferon plus ribavirin combination therapy in patients with chronic HCV genotype 1b infection

BACKGROUND

Abnormal serum lipid profiles have been noted in patients with chronic hepatitis C virus (HCV) infection. Moreover, many reports suggest that serum lipoprotein profiles are more profoundly distorted in patients with HCV G1b infection who have an unfavorable response to pegylated interferon (peg-IFN) plus ribavirin (RBV) combination therapy. However, after the discovery of single nucleotide polymorphisms near the IL28B gene (rs8099917 and rs12979860) as potent predictive factors affecting the response to peg-IFN plus RBV, lipid factors are thought to be confounding factors.

OBJECTIVES

To re-examine the significance of lipoprotein profiles on virological response to peg-IFN plus RBV combination therapy in patients with chronic HCV G1b infection, we examined cholesterol and triglyceride concentrations in each lipoprotein fraction separated by high performance liquid chromatography.

PATIENTS AND METHODS

Lipoprotein profiles were examined using fasting sera from 108 patients infected with HCV G1b who had chronic hepatitis, as determined by liver biopsy. Results of lipoprotein profiles and clinical data, including IL28B genotype and amino acid substitution at aa70 of HCV G1b, were compared between patients with a sustained virological response (SVR) and non-SVR or a non-virological response (NVR) and virological responses other than NVR (non-NVR). In addition, significant predictive factors independently associated with virological response to peg-IFNα-2b plus RBV were determined by logistic regression analysis.

RESULTS

An increased ratio of cholesterol/triglyceride in very low-density lipoprotein (odds ratio (OR) 3.03; 95% confidence interval (CI) 1.01-9.44) along with a major genotype of rs8099917 (OR 9.09; 95% CI 2.94-33.33), were independent predictive factors for SVR. In contrast, lipid factors were not elucidated as independent predictive factors for NVR.

CONCLUSIONS

Examination of the fasting lipid profile has clinical importance in predicting the efficacy of peg-IFN-α-2b plus RBV combination therapy for patients with HCV G1b even after the discovery of the IL28 genotype as a potent predictive factor.

The impact of interferon lambda 3 gene polymorphism on natural course and treatment of hepatitis C

Host genetic factors may predict the outcome and treatment response in hepatitis C virus (HCV) infection. Very recently, three landmark genome-wide association studies identified single nucleotide polymorphisms near the interleukin 28B (IL28B) region which were more frequent in responders to treatment. IL28B encodes interferon (IFN)λ3, a type III IFN involved in host antiviral immunity. Favourable variants of the two most widely studied IL28B polymorphisms, rs12979860 and rs8099917, are strong pretreatment predictors of early viral clearance and sustained viral response in patients with genotype 1 HCV infection. Further investigations have implicated IL28B in the development of chronic HCV infection versus spontaneous resolution of acute infection and suggest that IL28B may be a key factor involved in host immunity against HCV. This paper presents an overview about the biological activity and clinical applications of IL28B, summarizing the available data on its impact on HCV infection. Moreover, the potential usefulness of IFNλ in the treatment and natural history of this disease is also discussed.