Interleukin 28B genetic polymorphism and hepatitis B virus infection

Abstract

Interleukin (IL) 28B genetic polymorphism is significantly associated with the sustained virological response rate in patients with chronic hepatitis C treated with pegylated interferon-α (PEG-IFN) plus ribavirin and with spontaneous hepatitis C virus clearance. However, a consensus on the relationship between IL28B genetic polymorphism and the favorable outcome of chronic hepatitis B virus infection defined by hepatitis B e antigen seroconversion, and/or hepatitis B surface antigen seroclearance in patients treated with interferon or PEG-IFN has not been reached. Several reports failed to show a positive association, while some studies demonstrated a positive association in certain subject settings. More prospective studies including large cohorts are needed to determine the possible association between IL28B genetic polymorphism and the outcome of interferon or PEG-IFN treatment for chronic hepatitis B.

Key Words: Interleukin 28B, Polymorphism, Hepatitis B virus, Interferon, Pegylated interferon

Core tip: An association between interleukin (IL) 28B genetic polymorphism and sustained virological response rate in patients with chronic hepatitis C treated with pegylated interferon-α and ribavirin or spontaneous hepatitis C virus clearance has been established. However, the association between IL28B genetic polymorphism and hepatitis B virus infection remains unclear. We discuss this topic and summarize the available clinical data.

INTRODUCTION

Recent advances in molecular biology have enabled us to discover not only various factors regarding pathogens, but also regarding hosts which may influence the fate, character, mode of onset and natural or therapeutic outcome of various disorders. One such example is a genome-wide analysis of sequence. Such progress is also obvious in the research field of gastroenterology and hepatology. For example, the discovery of an association between single nucleotide polymorphism (SNP) at or near the interleukin 28B (IL28B) gene and the sustained virological response (SVR) rate with pegylated interferon-α (PEG-IFN) plus ribavirin (RBV) treatment for chronic hepatitis C (CH-C)[1-3]. Subsequent studies confirmed an association between IL28B and spontaneous hepatitis C virus (HCV) clearance[4,5]. The IL28B genetic polymorphism also accounts for the racial difference in the SVR rate with PEG-IFN/RBV treatment for CH-C[1].

Recently, a possible association between IL28B genetic polymorphism and hepatitis B virus (HBV) infection has become a target of interest. It is known that 240 million individuals are chronically infected with HBV worldwide[6], with the majority in the Asia-Pacific region[7]. An association between IL28B genetic polymorphism and the rate of hepatitis B e antigen (HBeAg) seroconversion and/or hepatitis B surface antigen (HBsAg) seroclearance with PEG-IFN treatment has been intensively discussed recently.

Here we summarize and discuss the possible association between IL28B genetic polymorphism and the favorable outcome of chronic HBV infection defined by HBeAg seroconversion and/or HBsAg seroclearance in patients with chronic hepatitis B (CH-B) treated by PEG-IFN with or without nucleoside analogues.

FACTS ON IL28B

IL28B is a class II cytokine receptor ligand related to type I interferons. These ligands play a critical role in response to microbial challenge and activate the JAK/STAT signaling system and show anti-viral activity by inducing interferon-stimulated genes (ISG)[8]. IL28B is located on the long arm of chromosome 19 and spans about 1.5 kilo base pairs. It encodes interferon λ3 (IFN λ3), one of the type III IFNs, while IL29 and IL28A encode other type III IFNs, namely IFN λ1 and λ2.

It is unknown why IL28B (namely IFN λ3) genetic polymorphism influences the SVR in PEG-IFN/RBV therapy for CH-C as described above. Gene expression studies using peripheral blood mononuclear cells revealed that IL28B gene expression was lower in individuals carrying minor alleles[2,3]. In contrast, there is no difference in hepatic IL28B gene expression according to haplotypes, although pretreatment intrahepatic ISG expressions are higher in individuals carrying minor alleles[9,10]. These results may support the previously reported findings that already elevated ISG gene expression before treatment was significantly related to poor viral eradication rate since externally administered PEG-IFN did not fully stimulate ISG[11,12].

Type III IFN is a major component of the innate immune system of liver cells. HCV infection studies in primary human fetal liver cell cultures[13] revealed that cell culture-induced HCV evoked expression of type III (λ) IFNs and of ISGs, while low expression of type I IFNs (IFN α and β) was observed. Higher levels of viral replication were associated with greater induction of ISGs and IFNλ. It was shown in 2005 that IFNλ inhibited HBV replication in a differentiated murine hepatocyte cell line as well as replication of a subgenomic and a full-length genomic HCV replicon in Huh7 cells[14]. IFN-α and IFNλ3 in combination showed synergistic anti-HCV activity in the HCV 1b and 2a replicon system[15]. The humanized livers of chimeric mice exhibited increased expression at the mRNA and protein level of human IFNλs, following treatment with a hepatotropic cationic liposome and a synthetic double-stranded RNA analog[16] resulting in a strong antiviral effect on HBV and HCV. With regard to the possibility of IFNλ as a therapeutic agent for CH-C, a phase 1b trial revealed that weekly PEG-IFN-λ with or without daily RBV for 4 wk was associated with clear antiviral activity across a broad range of doses in patients with CH-C[17].

As another source of IFN-λ in liver, human type 2 myeloid dendritic cells, or human blood dendritic cell antigen 3-positive cells instead of hepatocytes were recently reported to be a potent producer of IFN-λ in response to HCV[18,19].

POSSIBLE ASSOCIATION BETWEEN IL28B GENETIC POLYMORPHISM AND SPONTANEOUS HBV RECOVERY OR OUTCOME OF PEG-IFN TREATMENT FOR CH-B

The first study concerning IL28B and HBV infection was reported in 2010, the following year it was discovered that this genetic polymorphism was strongly associated with the SVR rate in patients with CH-C treated with PEG/RBV. In this report, C-C genotype of rs12979860 was not associated with HBV recovery (OR = 0.99)[20]. Two subsequent reports in 2011[21,22] also failed to show the possible association, although one revealed an association between genotype, allele and haplotype frequencies of IL28B and both aminotransferase levels and HBV DNA[21]. In 2012, the first report that determined a positive association between IL28B genetic polymorphism and chronic HBV infection was published[23]. IL28B genotype was significantly associated with HBeAg seroconversion at the end of PEG-IFN treatment (P < 0.01), the adjusted odds ratio for seroconversion was 3.16 (P = 0.013) for AA vs AG/GG at rs12980275 after adjustment for HBV genotype, age, levels of HBV DNA and alanine aminotransferase, and PEG-IFN and a nucleoside analogue-lamivudine combination therapy. IL28B genotype was independently associated with an increased probability of HBeAg seroconversion during long-term follow-up (adjusted HR = 2.14, P = 0.018 by Cox regression analysis). Similar results were obtained for rs12979860. IL28B genotype was also associated with HBsAg clearance (HR = 3.47, P = 0.042). Thus, the authors concluded that polymorphisms near IL28B were independently associated with serologic response to PEG-IFN in patients with HBeAg-positive chronic hepatitis B.

Another report published in 2012[24] also demonstrated a possible association between IL28B and HBeAg-positive CH-B in a Chinese Han population, while another 3 reports published in the same year[25-27] concluded that IL28B was not significantly related to the outcome of patients with CH-B who were treated with PEG-IFN. Three SNPs in the IL28B gene (rs12979869C/T, rs8099917G/T and rs12980275G/A) were examined in 330 subjects [including 154 HBV-related hepatocellular carcinoma (HCC) patients, 86 non-HCC patients with CH-B, 43 HBV self-limited infections and 47 healthy controls][28]. In conclusion, the IL28B rs12979860C/T polymorphism might affect susceptibility to chronic HBV infection and progression of HCC. In another report, the effect of rs8099917 in IL-28B gene as well as rs187238 and rs1946518 in IL-18 gene on HBV recurrence in liver transplant patients was investigated in a Chinese Han population[29]. In 140 HBV-related liver transplant recipients, the genotype of IL-28B gene rs8099917 was associated with aminotransferase levels. The recipients with allele G (GG + GT) had higher aminotransferase levels (P < 0.05). No association was found between IL-18 gene and IL28B gene polymorphisms with HBV recurrence in the liver transplant recipients or the donors. The authors concluded that allele G of rs8099917 was associated with hepatitis B-related hepatocyte injury. Association analysis between SNPs in IL-28B gene and the progress of HBV infection in Han Chinese revealed[30] that IL-28B rs12979860 C/T polymorphism T allele appeared to be more prevalent in patients with HCC than in those with liver cirrhosis.

In 2013, a positive association between IL-28B genetic polymorphism and the outcome of CH-B[31] was reported. A hundred and one HBeAg-negative patients (92% genotype D) with compensated CH-B were followed for a median of 11 (1-17) years after a median of 23 (10-48) mo of either standard or PEG IFN-α therapy. The rs12979860 (C > T) genotype in the IL28B locus was assessed. During a median of 11 years of post-treatment follow-up, 21 (21%) patients cleared serum HBsAg, including 15 who developed > 10 IU/mL anti-HBs titers. Forty-eight patients (47%) had CC genotype, 42 (42%) CT and 11 (11%) TT, the allelic frequency being 68% for C allele and 32% for T allele. The rate of serum HBsAg clearance was 29% (n = 14) in CC compared to 13% (n = 7) in non-CC genotype carriers (P = 0.039). Baseline HBV DNA levels < 6 log cp/mL (OR = 11.9, 95%CI: 2.8-50.6, P = 0.001), ALT levels >136 IU/mL (OR = 6.5, 95%CI: 1.8-22.5, P = 0.003), duration of IFN (OR = 1.16, 95%CI: 1.02-1.31, P = 0.021) and genotype CC (OR = 3.9, 95%CI: 1.1-13.2, P = 0.025) independently predicted HBsAg clearance. The authors concluded that IL28B polymorphism is an additional predictor of off-therapy IFN-related HBsAg seroclearance in HBeAg-negative patients chronically infected by genotype D HBV. Another work published in 2012[32] revealed that HLA-DP and IL28B genetic polymorphisms were associated with spontaneous HBsAg seroclearance in chronic hepatitis B patients.

In 2013, two reports concerning IL28B genetic polymorphism and the therapeutic outcome with PEG-IFN or natural course of CH-B failed to show any meaningful association between both[33,34]. In contrast, the SNP upstream of IL28B which has the strongest genetic association with HCV recovery had an inverse influence on HBV recovery[35] in a recent Korean study. IL28B polymorphism correlated with active hepatitis in patients with HBeAg-negative CH-B[36]. Jilg et al[37] describe and summarize potent associations between IL28B genetic polymorphism and chronic HBV infection in their review. Table 1 summarizes the possible association between IL28B genetic polymorphism and the effect of IFN-α or PEG-IFN in HBV infection, or spontaneous HBsAg seroclearance.

Table 1 Possible association between interleukin 28B genetic polymorphism and the effect of interferon-α and/or pegylated interferon-α, or spontaneous hepatitis B e antigen and/or hepatitis B surface antigen clearance in hepatitis B virus infection.

No.	Year	Ref.	Targeted SNPs	Subject settings	HBe	Result	Comments
1	2010	Martin et al[20]	rs12979860	226 HBV persistence, 384 HBV recovery	ND	Negative	C/C genotype of rs12979860 was not associated with HBV recovery (OR = 0.99)
2	2011	Li et al[21]	rs12979860, rs12980275, rs8099917	203 chronic HBV infection, 203 self-limited HBV infection, 203 individuals negative for all HBV seromarkers (Chinese Han population)	ND	Negative
3	2011	Tseng et al[22]	IL28B regions	115 HBeAg-positive chronic hepatitis B patients	Positive	Negative
4	2012	Sonneveld et al[23]	rs12980275, rs12979860	205 HBeAg-positive patients who were treated with PEG-IFN (Europeans and Asians)	Positive	Positive	IL28B genotype was significantly associated with HBeAg seroconversion at the end of treatment (P < 0.001, OR = 3.16), during long-term follow up (HR = 2.14), or with HBsAg seroclearance (HR = 3.47)
5	2012	Wu et al[24]	rs8099917	512 HBeAg positive chronic hepatitis B patients (Han Chinese) were treated with pegylated interferon a-2a ± nucleoside analogues	Positive	Positive	The frequency of G allele of rs8099917 was significantly higher in the response group than in the non-response group (8.3% vs 3.9%, P = 0.003, OR = 0.44, 95%CI: 0.25-0.79). The genotype distributions of this SNP also differed significantly between the two groups (P = 0.003)
6	2012	de Niet et al[25]	rs12979860	95 chronic hepatitis B patients who were treated with PEG-IFN and adefovir for 1 yr and who had 15% HBsAg loss (overall)	Positive and negative	Negative
7	2012	Peng et al[26]	rs12979860	651 HBV persistent infection (387 with liver cirrhosis, 264 without cirrhosis), 226 healthy individuals who recovered from HBV infection	ND	Negative	No association with clearance of HBsAg, HBeAg, HBV DNA level, apparent hepatitis onset and liver cirrhosis (P > 0.05)
8	2013	Lampertico et al[31]	rs12979860	101 HBeAg-negative patients (92% genotype D) with compensated chronic hepatitis B (84% males, 42% with cirrhosis)	Negative	Positive	The rate of serum HBsAg clearance was 29% in CC (major homo) compared to 13% in non-CC (hetero or minor homo) genotype carriers (P = 0.039)
9	2013	Seto et al[32]	IL28B (rs12979860, rs8099917)	203 chronic hepatitis B patients achieving spontaneous HBsAg seroclearance with 203 age- and sex-matched chronic hepatitis B patients without HBsAg seroclearance (control)	Negative	Positive	IL28B haplotype block CG was associated with HBsAg seroclearance (OR = 10.5, P = 0.026)
10	2013	Holmes et al[33]	rs12979860	96 patients (88% were Asian, 62% were HBeAg positive and 13% were METAVIR stage F3-4). The majority (84%) of patients carried the CC IL28B genotype (major homo)	Positive and negative	Negative
11	2013	Lee et al[34]	rs8099917, rs12979860, rs12980275	404 spontaneously recovered patients, 313 chronic hepatitis B patients, 305 liver cirrhosis patients and 417 hepatocellular carcinoma patients	ND	Negative

Studies are chronologically numbered. HBV: Hepatitis B virus; ND: Not determined or not described; IL: Interleukin; HBeAg: Hepatitis B e antigen; HBsAg: Hepatitis B surface antigen; PEG-IFN: Pegylated interferon-α.

FUTURE PERSPECTIVE

As mentioned above, there is still controversy regarding the true association between IL28B genetic polymorphism and chronic HBV infection. More evidence is required to obtain a final conclusion and a number of prospective studies with large cohorts of patients are needed to accomplish this purpose.