Interleukin 27 polymorphisms in HCV RNA positive patients: is there an impact on response to interferon therapy?

In agreement to the broad role that cytokines play in shaping many aspects of innate and adaptive immunity, there was a concerted effort toward identifying single nucleotide polymorphisms (SNPs) of cytokine associated with human diseases [1].

Interleukin 27 (IL-27) is a novel Interleukin 12 (IL-12) family member, formed by the dimerization of two subunits, Epstein-Barr virus-induced gene 3 (EBI3) and IL-27p28, which engages a receptor composed of gp130 and IL-27Rα activating Janus kinase (JAK)/signal transducer and activator of transcription (STAT) and mitogen activated protein kinase (MAPK) signaling. The human IL-27 gene is located on chromosome 16p11 and consists of five exons. Recently, both c.-964A/G ( rs153109) and 2905T/G (rs 181206) polymorphisms, corresponding to promoter region of IL-27p28 gene, were identified to be associated with individual susceptibility of asthma, inflammatory bowel diseases [2, 3]. The findings of Huang et al., [4] suggest that polymorphisms of IL-27 gene -964 A/G may not be involved in susceptibility to colorectal cancer (CRC), but this does not exclude the possible involvement of other polymorphisms of IL-27 like 2905 T/G (rs 181206). Moreover, Robinson et al. [5] showed the ability of IL-27 to regulate the macrophage activity during Mycobacterium tuberculosis infection while Peng et al., [6] associated SNPs of IL-27 gene with the development of chronic hepatitis B.

Furthermore, recent reports have shown that IL-27 significantly induces interferon (IFN)-inducible antiviral genes, suggesting that IL-27 inhibits human immunodeficiency virus (HIV), influenza virus and hepatitis C virus (HCV) replication by eliciting an IFN-like response [7–10]. The mechanisms underlying the HCV-induced liver damage have not been completely clarified yet. Several studies have shown that hepatitis pathogenesis and the rate of liver disease progression are influenced by several factors such as environmental parameters and viral factors (genotype and level of viremia) [11–15].

However, this approach is considered limitative because the evolution of liver disease and the response to treatment appear to be the result of a dynamic process in which genetic factors of host are mainly involved.

Indeed, information about genetic variants, either mutant or polymorphic, represents the basis for the development of new clinical approach for the management of chronic HCV infected patients [16]. Several independent genome-wide association studies (GWAS) have reported that SNPs near the gene IL-28B are strongly correlated with HCV containment, spontaneous clearance, host response to antiviral treatment and disease progression [17–19].

All these findings prompted us to hypothesize that interleukin-27 could influence the HCV infection susceptibility and response to therapy.

In this report, we show the development of an assay useful to detect SNP of the promoter region of IL27 p28 gene ( rs153109) and report preliminary data on HCV RNA-positive patients undergoing treatment with peginterferon-α (PegIFN- α) combined with ribavirin (RBV).

In this preliminary report, we evaluated the rs153109 alleles of the IL27p28 gene in patients with chronic hepatitis C using a direct sequencing approach. In particular, we analyzed the genotype of this SNP on c. -964A>G. Our data show a different distribution of genotype and allele of SNP in our patients. Indeed, the A/G genotype is present in non-responders and relapser compared to patients with a sustained viral response (SVR). In addition, the G/G genotype was absent in patients who negatively respond to antiviral therapy. Moreover, the analysis of allele distributions of the SNPs highlights a predominance of allele A in all genotypes in spite of allele G (see Figure 3).

It is well known that host and viral factors can predict treatment outcome; host factor, such as SNPs of Interleukin 28A (IL28A), Interleukin 28B (IL28B), Interleukin 29 (IL 29), interferon-γ (IFN- γ), mannan binding lectin (MBL), Interleukin 10 (IL−10), Interleukin 18 (IL-18), human cytotoxic T-lymphocyte antigen 4 (CTLA 4), Tumor necrosis factor-related apoptosis inducing ligand receptor 1 (TRAIL), Transforming growth factor (TGF-β), Osteopontin, low molecular mass polypeptides (LMP 7), oligoadenylate synthetase (OAS1) genes, insulin resistance, obesity and ethnicity, have been found to modulate treatment response [20]. Moreover, there is still a great effort for discovering new direct-acting inhibitors of HCV that will be used in combination with interferon or without it. For these reasons, further studies on host genetic factors that may predict the treatment outcome of combinational therapies and progression of liver disease are required.

IL-27 is one of the critical cytokines that functions as a mediator between the innate and adaptive immune system. Moreover, IL-27 synergizes with IL-12 to potentiate Interferon-γ (IFN-γ) production by activated naïve T- and Natural Killer (NK) cell populations [21]. Recent studies revealed that SNPs of the IL-27 promoter region modulate the development of infectious diseases and individual's susceptibility to therapeutic response [5, 6].

Our work provides information for a standardized method useful to genotyping of rs153109 and might suggest an association between treatment response and genetic variability of IL-27p28 SNPs.

Given the small number of patients studied, the statistical association demonstrated in this study may have occurred by chance. However, this approach could represent an interesting starting point for future investigations. Therefore, a larger sample size should confirm our results. Moreover, prospective studies should support the causal relationship between the presence of A/G genotype in non-responder and relapser patients, as well as the major presence of A allele. So, could allow us to identify IL-27p28 SNPs as novel genetic markers which may correlate with therapy response and, possibly, with liver disease progression in HCV infected patients.