Article Text
PDF
Abstract
Background Only a minority of patients with chronic hepatitis C virus (HCV) infection develops severe liver fibrosis, a process that may be controlled by human genetic factors.
Objective To investigate the role of 384 single nucleotide polymorphisms (SNPs) located in 36 candidate genes related to the fibrogenesis/fibrolysis process.
Methods Patients with chronic HCV infection were gathered from two French cohorts (prospectively and retrospectively). The overall sample consisted of 393 HCV-infected subjects without known risk factors for fibrosis progression, including 134 patients with severe liver fibrosis and 259 without severe fibrosis.
Results Only two SNPs in strong linkage disequilibrium (LD) in the interferon γ receptor 2 gene (IFNGR2) were significantly associated with liver fibrosis in both the prospective and the retrospective samples. The strongest association (p=8×10−5) was observed with the G/A SNP rs9976971 with an OR of severe fibrosis for AA versus AG or GG subjects at 2.95 (95% CI 1.70 to 5.11). This effect was higher (p=9×10−7) when taking into account the time of follow-up, and the hazard ratio of progression towards severe fibrosis for AA patients was 2.62 (1.76 to 3.91). Refined sequencing and analysis of the IFNGR2 region identified two additional variants in strong LD with rs9976971. No haplotypes derived from this cluster of four variants provided stronger evidence for association than rs9976971 alone.
Conclusions This identification of a cluster of four IFNGR2 variants strongly associated with fibrosis progression in chronic HCV infection underlines the role of IFNγ in the development of liver fibrosis that may pave the way for new treatments.
- Genetic polymorphisms
- hepatic fibrosis
- hepatitis C
- liver cirrhosis
Statistics from Altmetric.com
Significance of this study
What is already known about this subject?
Only a minority of patients with chronic HCV infection develops severe liver fibrosis.
Viral and non-genetic host factors cannot account for the variability in the rate of progression towards liver fibrosis in patients with chronic HCV infection.
There is accumulating evidence for the role of host genetic factors in the development of liver fibrosis, although these factors are as yet largely elusive.
What are the new findings?
We investigated the role of 384 single nucleotide polymorphisms (SNPs) located in 36 candidate genes related to the fibrogenesis/fibrolysis process.
We identified a single cluster of variants in the interferon γ receptor 2 gene (IFNGR2) strongly associated with progression to severe fibrosis.
This association was replicated in an independent population sample, and was stronger when taking into account the time of follow-up from contamination to liver biopsy with a hazard ratio of developing severe fibrosis estimated as 2.62 (1.76 to 3.91) for the subjects homozygous for the predisposing allele.
How might it impact on clinical practice in the foreseeable future?
As IFNγ is an anti-fibrogenic cytokine available for clinical purposes, our study may open new therapeutic avenues for the prevention of cirrhosis in HCV-infected patients.
Introduction
Hepatitis C virus (HCV) infection is a major public health concern world wide with an estimated 170 million people infected.1 2 The natural history of patients with HCV chronic infection is characterised by a highly variable disease progression.1–5 Most subjects never develop cirrhosis during their lifetime while the remaining patients are considered ‘rapid fibrosers’ and may develop severe fibrosis in <20 years.1 5–7 While viral factors such as HCV genotypes or viral load do not seem to influence progression, several host factors such as gender (male), age at infection (>40 years old), alcohol consumption (>50 g/day), obesity and its related metabolic disorders, co-infections (in particular by HIV) are associated with the development of fibrosis.4 5 8 9 However, these factors can account for only a minority of the variability in the rate of progression, and a number of studies have investigated the role of genetic host factors.5 10 Most of these studies have tested a single or a few candidate genes, and have not produced conclusive results as they were not clearly replicated.10 11 A recent study investigated a large number (>24 000) of putative functional single nucleotide polymorphisms (SNPs) and identified two variants associated with severe fibrosis.12 In a subsequent study which used the same SNPs and focused on Caucasian patients with well-characterised liver histology, a different panel of seven SNPs was found to predict the risk of developing cirrhosis, and this panel needs to be validated in prospective studies.13
Liver fibrosis is the consequence of a generalised wound-healing response of hepatic tissue against repeated injury, which results in the formation of scar tissue instead of normal parenchyma.14 This process is characterised by an imbalance between matrix synthesis (ie, fibrogenesis) and matrix degradation (ie, fibrolysis), and leads to an accumulation of a large variety of matrix proteins, including collagens, proteoglycans and glycoproteins.15 16 Activated hepatic stellate cells, portal fibroblasts and myofibroblasts of bone marrow origin are the major collagen-producing cells in the injured liver.14 A number of molecules and regulatory pathways are involved in this complex process of fibrogenesis/fibrolysis.14–16 Therefore, we hypothesised that variations in human genes involved in fibrogenesis/fibrolysis might account for interindividual variability in development of liver fibrosis among patients with chronic HCV infection. In this work we focused on the role of polymorphisms located in a panel of 36 genes (table 1) encoding either enzymes involved in extracellular matrix turnover (matrix metalloproteinases and their inhibitors) or some cytokines known to exhibit profibrogenic (transforming growth factor β (TGFβ) and related molecules) or anti-fibrogenic (interferon γ (IFNγ) and its receptors) activity. In addition to classic case–control analysis, in this study we analysed the influence of SNPs directly on the time of progression by restricting our sample to patients with a known presumed date of infection and without known risk factors of fibrosis progression such as chronic alcohol intake, associated infections or metabolic syndrome.
List of the genes investigated in the association study
Patients and methods
Patients
We recruited adult Caucasian patients (>18 years of age) with chronic HCV infection defined as the presence of circulating HCV RNA tested by reverse transcriptase PCR. The patients were gathered in two steps. First, we conducted a prospective enrolment of patients from the hepatology units of Necker Hospital in Paris and St Joseph Hospital in Marseille (sample A). The criteria for the inclusion of patients were (a) an available liver biopsy before any treatment; (b) a known presumed date of HCV acquisition (date of the first exposure to blood products, or of beginning of intravenous drug (IVD) use); (c) a low alcohol consumption (less than three or less than two standard drinks a day for men or women, respectively); (d) absence of co-infection with HIV or hepatitis B virus; (e) absence of any coexisting chronic liver disease or hepatocellular carcinoma. Clinical risk factors, history of HCV acquisition and of alcohol consumption (assessed using time-line follow-back interview) were recorded through face-to-face interviews conducted by doctors trained in addiction problems. In a second step, we gathered additional patients from an existing cohort from the hepatology unit of Pitié-Salpêtrière Hospital in Paris (sample B). The inclusion criteria were the same as for sample A except that the presumed date of infection was not known for all patients. The study was approved by the appropriate institutional review boards, and written informed consent was obtained from all patients.
Most of the enrolled patients had been followed up for a number of years in the corresponding clinics and had had a liver biopsy at the time of their first evaluation. The stage of fibrosis was assessed from liver biopsy samples using METAVIR units, and graded on a five-point scale from 0 to 4.17 For this study, in order to optimise the phenotype definition, we excluded patients with grade 2, and retained only patients with grades 0 or 1 (F0–1 patients) referred to as having no fibrosis, and patients with grades 3 or 4 (F3–4) referred to as having severe fibrosis. For patients who had had several biopsies, we used either the first biopsy specimen showing severe fibrosis (F3–4 patients) or the last biopsy showing no fibrosis without any treatment (for F0–1 patients). The duration of infection was estimated from the presumed year of HCV acquisition (eg, first exposure to blood transfusion, or to IVD use) to the year of the relevant biopsy.
Genotyping and sequencing methods
In this study we focused on the role of polymorphisms located in a panel of genes encoding either enzymes involved in extracellular matrix turnover (matrix metalloproteinases and their inhibitors) or cytokines that are believed to have a profibrogenic (TGFβ and related molecules) or an anti-fibrogenic (IFNγ and its receptors) activity. A total of 36 genes were selected and are shown in table 1. A selection of SNPs within each gene, totalling 384 SNPs (list in online supplementary table 1), was made using data from the first public release of HapMapII. For each gene, all HapMap SNPs in the region including the gene and the 10 kb flanking regions were initially considered. SNPs with minor allele frequency <5% or with low predicted quality for genotyping (calculated by Illumina) were filtered out, and pairwise linkage disequilibrium (LD) was estimated (from the HapMap data) between all pairs of remaining SNPs within each gene. The 384 SNP panel was then selected such that no two SNPs in the same gene had an estimated r2≥0.8 or were <60 bp apart.
All DNA samples were extracted from whole blood, and subjected to rigorous quality control to check for fragmentation and amplification. All SNPs were genotyped on an ultra-high throughput Illumina platform. This platform uses the GoldenGate assay followed by a bead-based technology to resolve individual SNP genotypes.18 Discovery of SNPs within an IFNGR2 region of ∼12.3 kb from 33 689 894 to 33 702 179 bps on chromosome 21 was performed by exhaustive sequencing (figure 1). The sample consisted of 32 French Caucasian subjects (men and women with no disease history) from the Epidemiological study on the Genetics and Environment of Asthma.19 The sample size of 32 allowed us to detect SNPs with a minor allele frequency of at least 5% with a probability of 96%. Sequencing reactions were performed with the Dye Terminator method using an ABI PRISM 3730 DNA Analyser (Applied Biosystems, Foster City, California, USA). Sequence alignment and SNP discovery were performed with Genalys software, developed by the Centre National de Génotypage (CNG).20
Schematic representation of the chromosome 21 region ranging from 33 689 800 to 33 702 200 bps, and including the 5′ region, exon 1 and part of intron 1 of IFNGR2. Exon 1 ranges from 33 697 072 to 33 697 792 bp with an untranslated and a translated part shown as a hatched and a solid box, respectively. Horizontal arrows indicate the regions covered by direct sequencing. Three segments could not be sequenced for technical reasons (33 694 486–33 696 000, 33 696 161–33 696 390 and 33 699 114–33 700 075 bp). The four single nucleotide polymorphisms associated with severe fibrosis are indicated by vertical arrows with distance in base pairs provided from the position of rs9976971, which is located at 33 689 967 bp.
Statistical methods
Association between severe fibrosis and the panel of SNPs was first tested in sample A by a case–control analysis using the genotypic test statistic (two degrees of freedom): the cases are HCV-infected patients with severe fibrosis and the controls are infected patients without severe fibrosis. When a type I error of 0.02 was used, our initial sample A had a power of 80% for detecting a polymorphism with an additive effect, providing an odds ratio (OR) for heterozygosity of two and having a frequency >0.09. For SNPs showing association at p<0.02, we then tested association by a survival analysis approach using a Cox model: we considered as starting points the estimated ages at infection, and as end points either the first biopsy showing severe fibrosis (failure time) or the last biopsy showing absence of severe fibrosis in the absence of any treatment (censored time). For all these analyses, we determined the genetic model (dominant/additive/recessive) providing the best fit to the data. SNPs showing the most interesting results (p<0.02 in the case–control study and p<0.05 in the survival analysis) were then tested for replication in sample B.
We tested for heterogeneity of the association results according to different criteria, such as gender, mode of infection (blood transfusion/IVD use/others), viral genotypes (one and four vs others), age at infection (≤20 years vs >20 years). Under the hypothesis of homogeneity of association, twice the difference between the likelihood of the whole sample and the summed likelihoods of the subsamples (eg, the two subsamples of men and women) is asymptotically distributed as a χ2 with one degree of freedom. All statistical analyses were performed using different procedures (FREQ, LOGISTIC, PHREG) implemented in SAS software version 8.2 (SAS Institute). Pairwise LD between SNPs was assessed by determining the r2 coefficient using the Haploview software.21 Haplotype analysis was conducted using the THESIAS software (http://www.genecanvas.org, accessed 5 May 2010).22
Results
Description of the two samples
Samples A and samples B consisted of a total of 267 (103 F3–4 patients with severe fibrosis and 164 F0–1 patients without severe fibrosis), and 126 (31 F3–4 and 95 F0–1 patients) patients with chronic HCV infection, respectively. The main features of the overall sample including 393 patients are shown in table 2. There was an overall excess of women (58.5% vs 41.5%, p=8×10−4), which might be explained, in part, by the inclusion criterion of low alcoholic consumption, but there was no significant difference (p=0.24) in the distribution of gender according to fibrosis status. In the 364 patients with reliable HCV acquisition data, the overall distribution of modes of infection was different (p=0.0004) according to the fibrosis status. The proportion of patients infected by blood transfusion was higher in patients with severe fibrosis (57.5%) than in F0–1 patients (41.3%), while the reverse was observed for IVD users (43% in F0–1 patients vs 22% in F3–4 patients). F3–4 patients were significantly older (p=0.004) at infection (mean 29.9 years, range 0.1–73.2 years) than F0–1 patients (25.6 years, 0.1–70.8 years), and had a longer (p=10−4) duration of HCV infection at the time of biopsy (22.8 years, 0.7–49.6 years vs 18.9 years, 0.2–49.6 years). Finally, the distribution of viral genotypes combined as usual in three main groups according to their sensitivity to anti-viral treatment23 was not significantly different between F0–1 and F3–4 patients.
Main features of the HCV chronically infected patients in the whole sample
Four variants are associated with fibrosis in the first sample
Of the 384 SNPs, 16 SNPs could not be genotyped (supplementary table 1), and we excluded an additional five SNPs because either they showed deviations (p<0.005) from Hardy–Weinberg equilibrium (three SNPs) or they had a minor allele frequency <0.02 (two SNPs). The 363 remaining SNPs all showed a genotyping success >96%, and were used for association analysis. Association between severe fibrosis and the panel of 363 SNPs was first tested in sample A by a classic case–control analysis where cases were the HCV-infected patients with severe fibrosis and controls were the infected patients without severe fibrosis (supplementary table 1). A total of nine SNPs, including two in IFNGR2 and three in MMP16, provided evidence for association with a p value <0.02, and were investigated further. Of these nine SNPs, four significantly influenced (p<0.05) the rate of progression towards severe fibrosis when performing a survival analysis (table 3 and supplementary table 2). The effects of the two IFNGR2 SNPs, rs9976971 and rs2284553, which already yielded the lowest p values in the case–control study (p=3×10−4 and p=8×10−4, respectively), were even more significant (p=2×10−5 and p=8×10−5, respectively) using the survival analysis. Conversely, the effects of the two other SNPs (one in MMP16, and one in TGFBR2) were slightly lower when accounting for time of progression. For both rs9976971 and rs2284553 (which are G/A SNPs), the risk allele was the minor allele A and the best fitting genetic model was recessive—that is, subjects who were AA homozygous were predisposed to severe fibrosis as compared with AG and GG subjects. These two SNPs were in strong LD (r2=0.79), and multivariate analysis confirmed that the results observed with rs9976971 and rs2284553 reflect a single signal.
Results in both samples for the four single nucleotide polymorphisms (SNPs) providing the strongest evidence for association with severe fibrosis in sample A (ie, p<0.02 in case–control study and p<0.05 in the survival analysis). The full distribution of genotypes for these four SNPs is shown in online supplementary table 2
Two IFNGR2 variants show evidence for replication in the second sample
The four SNPs providing evidence for association both in case–control (at p<0.02) and survival (at p<0.05) were tested in sample B (table 3). Only the two IFNGR2 SNPs showed evidence for replication with the same risk allele. As in sample A, the survival analysis was more powerful than the case–control approach, leading to a significant effect in sample B for rs9976971 (p=0.011). A similar trend, although not significant (p=0.13), was observed for rs2284553. When samples A and B were combined (table 4), the overall effect of rs9976971 in the case–control design was highly significant (p=8×10−5), and the OR (95% CI) of presenting severe fibrosis for AA subjects as compared with AG or GG subjects was 2.95 (1.70 to 5.11). This effect was much stronger (p=9×10−7) in the survival analysis design, and the HR (95% CI) of progressing towards severe fibrosis for AA subjects as compared with AG or GG subjects was 2.62 (1.76 to 3.91) (figure 2).
Results in the whole sample for the four IFNGR2 variants providing the strongest evidence for association
Effect of single nucleotide polymorphism rs9976971 on fibrosis progression. The figure shows the variation with time of the proportion of fibrosis-free patients according to genotypes at rs9976971. The time of follow-up was estimated from the presumed year of infection to the year of either the first biopsy showing severe fibrosis (F3–4 patients) or the last biopsy showing no fibrosis without any treatment (for F0–1 patients).
Consistent with this result taking into account the duration of infection, we observed that the effect of rs9976971 in the classical case–control design was much stronger (OR=4.46 (2.28 to 8.72)) in the 57 F3–4 patients with rapid progression (≤20 years of infection) than in the 69 F3–4 patients with slow progression (>20 years of infection, OR=2.10 (1.04 to 4.25)). Even if we considered the fact that these results were obtained in a one-step strategy (without the use of a replication sample), and that we applied the classical and stringent Bonferroni correction for multiple testing (assuming we have tested the 363 SNPs in the whole sample), the corrected p values for rs9976971 remained significant and equal to 0.029 and 0.0003 in the case–control and the survival analysis, respectively. These results indicate that one SNP in IFNGR2, either rs9976971 or another variant in strong LD with it, strongly influences the rate of progression towards severe fibrosis in patients chronically infected by HCV.
Search for other polymorphisms in linkage disequilibrium with the two IFNGR2 variants
Next, we searched for other variants in strong LD with rs9976971 along three lines. First, we looked for long range LD (from 33 380 000 to 34 000 000 bp) using the European population of the HapMap database, NCBI build 36 (http://www.hapmap.org/, accessed 5 May 2010). Substantial LD (r2 ranging from 0.3 to 0.48) with rs9976971 was observed with three clusters of SNPs. We genotyped one tag-SNP within each cluster (rs2834208, rs13047599, and rs7279549), and no association with severe fibrosis (p>0.2) was observed with any of these tag-SNPs. No other SNPs showed r2 >0.3 within this interval, and, in particular, all SNPs between 33 524 000 and 33 655 000 bp where the genes IFNAR1 and IFNAR2 encoding interferon α/β receptors are located, provided r2 <0.11 with rs9976971. Second, we explored the SeattleSNPs variation discovery resource database as it contained results for IFNGR2 sequencing in 23 European subjects for a region of ∼ 38 kb (33 695 200–33 733 200) (http://pga.gs.washington.edu/data/ifngr2/, accessed 5 May 2010). Finally, as rs9976971 is located in 5′ of IFNGR2 (33 689 967), we also sequenced a sample of 32 French Caucasian subjects for a region of 12.3 kb from 33 689 894 to 33 702 179 (figure 1 and supplementary table 3). Based on these sequencing data from both the SeattleSNPs database and our own results, we identified two additional variants in strong LD with rs9976971 (table 4). One is the T/C SNP rs17882748 (r2=0.83 with rs9976971) located in the untranslated region of exon 1, and the other is an AA insertion/deletion denoted as rs10600672 (r2=0.98 with rs9976971) located in the 5′ region of the gene at position 33 691 495.
A cluster of four IFNGR2 variants is strongly associated with liver fibrosis progression
Table 4 shows the results of both the case–control and the survival analysis with the four variants of interest over the combined samples A and B. Although all variants were strongly associated with development of severe fibrosis, the most significant results were observed with rs9976971 (p=9×10−7) and the AA ins/del (p=4×10−6) when using survival analysis. The AA insertion is in almost perfect LD with the A allele of rs9976971 (only three subjects had discordant genotypes) so that the HR of progressing towards severe fibrosis for AA/AA subjects as compared with AA/– or –/– subjects was 2.47 (1.66 to 3.66), and the curve of progression towards fibrosis with age according to this ins/del variant was extremely similar to that shown in figure 2 for rs9976971. We did not find any significant heterogeneity of these associations according to gender, mode of infection (blood transfusion/IVD use/others), viral genotypes (1 and 4 vs others), age at infection (≤20 years vs >20 years). We also conducted an analysis considering the different haplotypes that could be derived from these four variants using the method developed in the THESIAS program.22 As expected by LD, two common haplotypes accounted for >90% of the estimated haplotypes (table 5). The common haplotype carrying the risk alleles at the four IFNGR2 variants had a frequency of 0.338 and 0.447 in F0–1 and F3–4 patients, respectively. Under a recessive model (table 5), the effects of this at-risk haplotype (using a case–control or a survival analysis) were slightly lower than those estimated from rs9976971 or rs10600672 alone. As expected by the r2 value at 0.98, the two variant haplotypes consisting of rs9976971 and rs10600672 provided results almost identical to the analysis of any of these variants alone (data not shown). However, none of the tested haplotypes consisting of three or four of these IFNGR2 variants provided stronger evidence for association than rs9976971 or rs10600672 when considered alone.
Results of the analysis considering haplotypes derived from the cluster of the four IFNGR2 variants providing the strongest evidence for association
Discussion
In this study, we investigated whether the development of liver fibrosis in HCV chronically infected patients might be influenced by polymorphisms located in a panel of 36 genes involved in the fibrogenesis/fibrolysis process. To reduce the variability in assessing fibrosis stage by biopsy,24 only F0–1 and F3–4 stages were included to define phenotypes. We found a single convincing signal of association in IFNGR2, which was the most significant in our primary sample and was exactly replicated (same allele at risk and same genetic model) in our second sample. The evidence for association was even higher (by one order of magnitude) when using the information obtained by the time of progression, providing strong additional support for our findings. The IFNGR2 signal results from a cluster of four variants in strong LD. These variants are quite common with a frequency in the HapMap Caucasian population of 0.41 for risk allele A of the most associated SNP rs9976971, and 26% AA homozygosity in our sample of F3–4 patients. Sequencing data obtained either from existing databases or from our present analysis excluded the role of any other SNPs located within a region of ∼43.5 kb (33 689 894–33 733 200 bps) encompassing the IFNGR2 gene. Analysis of the HapMap database also made quite unlikely the hypothesis that this signal could be due to another SNP in long-range LD with this cluster of four IFNGR2 variants. Refined analysis showed that no haplotypes derived from this cluster of four variants provided stronger evidence for association than any of the four SNPs when analysed alone. From a statistical point of view, the strongest evidence was obtained with rs9976971 and the AA ins/del (rs10600672), which are in almost perfect LD. Nevertheless, the roles of rs2284553 (in intron 1) and rs17882748 (in untranslated region of exon 1) could not be ruled out.
Although several association studies have investigated the role of a small number of polymorphisms within the gene encoding IFNγ (IFNG) and progression to fibrosis in HCV infection, in particular a variant at position +874 which may influence IFNγ expression, no consistent and clearly replicated results have been reported.10 A study also tested the role of variants within the interferon γ receptor 1 gene (IFNGR1), without any significant results.25 In this context, it is interesting to note that two linkage studies conducted in Sudan26 and Egypt27 mapped a locus predisposing to development of severe liver fibrosis due to the parasite Schistosoma mansoni infection in a region including the IFNGR1 gene. No precise variants underlying these linkage peaks have been reported yet. To our knowledge, no studies have yet investigated the influence of IFNGR2 polymorphisms in HCV-related liver fibrosis. We cannot rule out the possibility that some IFGNR2 variants were included in the study that tested the association with 24 823 putative functional SNPs.12 However, it is unlikely that any of our four associated polymorphisms were included in that panel as they are not known to be functional.
IFNγ is usually considered to be an anti-fibrogenic cytokine. In an experimental model of liver fibrosis induced with carbon tetrachloride, IFNγ-deficient mice exhibited more pronounced hepatic fibrosis lesions than wild-type animals, and exogenous IFNγ administered to deficient animals reduced the level of fibrosis.28 In human cells, IFNγ has been shown to inhibit activation, proliferation and collagen synthesis in cultures of activated hepatic stellate cells and hepatic myofibroblasts.16 29 It is also interesting to note that IFNγ has been proposed as a treatment for idiopathic pulmonary fibrosis and was associated with reduced mortality in a meta-analysis.30 Along the same lines, high levels of IFNγ production were associated with protection against periportal fibrosis in subjects infected with the parasites S mansoni31 or Schistosoma japonicum.32
However, the role of IFNγ may be more complex, as suggested by a study performed on liver biopsy specimens from patients with chronic HCV infection, which showed that increased IFNγ expression was associated with portal inflammation and fibrosis stage.33 This latter observation suggests that the proinflammatory effects of IFNγ may predominate over its anti-fibrogenic role in HCV liver fibrosis, although IFNγ expression might also be a consequence of the fibrosis process. For example, an impaired function of IFNγ receptors might lead to increased production of IFNγ, as seen in patients with complete IFNγ receptor deficiencies.34
In conclusion we have found that progression to severe liver fibrosis in HCV chronically infected patients of European origin is strongly associated with a cluster of four IFNGR2 variants. Interestingly, between the two IFNγ receptors, IFNγR2 expression appears to be the deciding factor that controls the way in which target cells physiologically respond to IFNγ.35 36 Functional studies are continuing in human liver cells to investigate the detailed biological mechanisms of this association and the potential effect of this cluster of variants on IFNGR2 regulation. Prospective studies using large samples will also assess the predictive value of these polymorphisms with repeated validated non-invasive biomarkers.37 IFNγ has already been found to be associated with clearance of HCV infection.38 39 These results highlight the role of the IFNγ pathway in development of liver fibrosis that may pave the way for new treatments.
Acknowledgments
We thank Rachel Morra, AP-HP/UPMC liver center, Hôpital Pitié-Salpêtrière, Paris, France, and la Banque de Cellules - Cochin APHP with all its staff for their logistic help and for providing patient lymphoblastoid cell lines. We are grateful to David-Alexandre Tregouët for helpful discussions about the haplotype analysis, and to the Centre National de Génotypage (CNG) for its help in genotyping. We also thank all members of the laboratory of Human Genetics of Infectious Diseases for fruitful discussions.
References
Supplementary materials
Web only files gut.2009.202267
Files in this Data Supplement:
Footnotes
Funding This work was supported by grants from Institut National de la Santé et de la Recherche Médicale (4CH08G), Japanese Society for Promotion of Science (JSPS)/Inserm cooperation agreement, and Agence Nationale de Recherche sur le SIDA et les hépatites virales (ANRS HC EP13). LA was supported, in part, by a grant from Assistance Publique-Hôpitaux de Paris.
Competing interests None.
Ethics approval This study was conducted with the approval of the institutional review board (CPP: Comité de Protection des Personnes) of Ile de France - Paris - Saint Antoine, on 5 March 2002.
Provenance and peer review Not commissioned; externally peer reviewed.
Linked Articles
- Digest