26 research outputs found
Interferon signalling in the liver : implications for the natural course and therapy of hepatitis C
No full textHepatitis C virus is a global health concern, estimated to infect 2-3% of the world's population. Inter-individual differences in the course of infection and response to therapy, highlighted by recent genomewide association studies, point to the crucial role of the host immune system in the efficient control of infection. Ongoing progress in the studies of the role of innate immunity during hepatitis C virus infection has improved our understanding of the intricacies of the host-virus interactions. In this work I present and discuss results of three studies aimed to dissect interferon signalling in the liver in the context of natural course or therapy of hepatitis C virus infection.
Interferon-based therapies are in clinical use for treatment of diseases such as hepatitis C virus infection or multiple sclerosis. Interferon-induced regulators of the Jak-STAT signalling are known to involve in negative feedback loops and affect the response to exogenously administered interferon alpha. In this context it is important to understand which interferon subtypes are potent inducers of the negative regulators and whether all interferons are equally sensitive to the inhibitory mechanisms. To tackle this question we attempted to characterize and compare response patterns to interferons alpha, beta and lambda in a setting of continuous and repeated stimulation (see Section 3.1).
The acute phase of hepatitis C virus infection in humans (first 6 months after transmission) is characterized by high rates of spontaneous clearance and excellent treatment response (>90% cure rate). As the infection at that stage is mostly asymptomatic, it is rarely diagnosed and, in comparison to the chronic phase of hepatitis C virus infection, little is known about the human liver response to acute hepatitis C virus infection and the host-virus interactions during this time. In the second part of this PhD project we made use of the acute hepatitis C liver biopsies collected over the course of several years at the University Hospital of Basel to describe human hepatic response to acute hepatitis C virus infection and gain an insight into the mechanism of improved cure rate compared to chronic hepatitis C (see Section 3.2).
Chronic hepatitis C is currently treated with combination therapies based on pegylated interferon- alpha. A significant proportion of patients fails to respond to the current treatment options, probably due to the refractory state of the preactivated endogenous interferon system in the liver. Several compounds are currently in clinical development with the aim to improve the treatment outcome of pegylated interferon�alpha nonresponders. In the last part of this work we investigated in vivo the mode of action
of a novel synthetic TLR9 agonist which is a clinical candidate for anti-hepatitis C virus therapy
and characterized the hepatic response to this compound (see Section 3.3)
1296 DEVELOPING END POINTS FOR CLINICAL TRIALS IN PBC: ALKALINE PHOSPHATASE AS A PREDICTOR OF OUTCOME
No full textInterferon signaling in chronic hepatitis C : mechanisms and implications for therapy
No full textHepatitis C virus (HCV) infection is a major cause of chronic liver disease worldwide and can lead to liver cirrhosis and hepatocellular carcinoma. The current standard therapy of chronic hepatitis C (CHC) consists of a combination of pegylated interferon alpha (pegIFNα) and ribavirin. However, sustained viral clearance is achieved in only 50-60% of patients. The underlying mechanism of failure of pegIFNα based therapy remains unknown and no molecular or genetic markers have been identified that could predict the treatment outcome. The overall aim of the study described in this thesis is to understand the molecular basis for failure of IFNα based therapies in patients with CHC. The study has focused on the IFNinduced Jak-STAT (janus kinase-signal transducer and activator of transcription) signaling pathway. To address the molecular basis of treatment response to IFN therapy, three experimental approaches have been employed. The first approach involved the analysis of IFNα signaling and expression of interferon stimulated genes (ISGs) in liver biopsies and peripheral blood mononuclear cells (PBMCs) of HCV patients undergoing pegIFNα treatment. Paired liver biopsies and PBMCs from 16 patients were collected before andhours after the first injection of pegIFNα, and were subjected to analysis of global gene expression using Affymetrix arrays. Further, activation of the IFN-induced Jak-STAT signaling pathway was analyzed by immunoblotting, immunohistochemistry and gel shift assays. The correlation of these biochemical and molecular data with the clinical response to treatment demonstrated that in the liver of patients with a rapid response pegIFNα induced a strong upregulation of ISGs, whereas in patients that did not respond to therapy, induction of IFN-dependent gene expression was impaired. Surprisingly, the non-responders had maximally induced ISG expression already before treatment with pegIFNα. Furthermore, the analyses of STAT1 phosphorylation, nuclear localization and DNA binding confirmed that the endogenous IFN signaling pathway in non-responders is pre-activated and refractory to further stimulation. In contrast to liver samples, ISG expression in PBMCs was stimulated by pegIFNα in both responders and nonresponders, indicating that PBMCs are not a good surrogate marker for IFNα responses in the liver and that chronic HCV infection has strong local effects on the IFN system in liver. Our findings support an interesting concept that activation of the endogenous IFN system in CHC not only is ineffective in clearing the infection, but may also impede the response to therapy, most likely by inducing a refractory state of the IFN signaling pathway in the liver.
In the second approach we addressed the mechanisms underlying the pre-activation of the
endogenous IFN system in a defined group of HCV patients (future non-responders). For this
purpose, we analyzed ISG expression by quantitative RT-PCR and nuclear localization of
STAT1 by immunohistochemistry in a cohort of 112 patients with CHC. By subdividing this
cohort according to the HCV genotype (GT), we discovered that patients infected with HCV
GT 1 and 4 more often show hepatic ISG preactivation than GT 2 and 3 patients, thus
providing an explanation for the poor response to IFN therapy seen in GT 1/4 patients. We
analyzed the possible involvement of viral sensory pathways in type I IFN production and
ISG upregulation. Previously, the viral HCV NS3-4A protease was shown to interfere with
viral sensory pathways by cleaving and thereby inactivating an important adaptor molecule,
Cardif. We therefore assessed Cardif cleavage in liver biopsies of HCV patients and found
that cleavage more often occurred in patients infected with HCV GTs 2 and 3. Our findings
support a concept that the success of the virus in preventing the induction of the endogenous
IFN system in the livers of these patients would, however, come at the cost of being more
susceptible to IFNα therapies as is the case with GT 2/3 patients.
In the third approach we designed an experimental model to study the molecular basis of
refractoriness of IFN signaling in vivo. Previously, cell culture experiments demonstrated a
long lasting desensitization period, which followed the initial activation of the IFNα
signaling pathway. In the approach used here, we established a mouse model in which
continuous presence of IFNα in vivo was achieved by multiple subcutaneous injections,
mimicking the constitutively high serum levels achieved by pegIFNα in patients.
Interestingly, this resulted in refractoriness of IFNα signaling. Activation of STAT1 and
STAT2, but not STAT3, in the mouse liver was desensitized by continuous IFNα stimulation.
To elucidate the mechanism of this refractoriness, the role of negative regulators of the Jak-
STAT signaling pathway was investigated. IFN signaling remained refractory in mice
deficient in suppressor of cytokine signaling (SOCS) 3 and persisting refractoriness was also
observed in mice deficient in IL-10, a strong inducer of SOCS3. Ubiquitin specific peptidase
18 (USP18/UBP43) was recently identified as novel negative regulator of IFNα signal
transduction. Interestingly, refractoriness could be overcome in USP18/UBP43 knockout
mice. These data strongly indicate that UBP43 is the decisive factor in inducing a refractory
state in the IFNα signaling pathway in vivo
IgG4 Related disease – a retrospective descriptive study highlighting Canadian experiences in diagnosis and management
No full textBACKGROUND: Appreciating the utility of published diagnostic criteria for autoimmune pancreatitis, when compared to the characteristics of patients clinically managed as having disease, informs and refines ongoing clinical practice.METHODS: Comparative retrospective descriptive evaluation of patients with autoimmune pancreatitis including dedicated radiology review.RESULTS: 66 subjects with radiographic OR clinical features of autoimmune pancreatitis were initially identifiable (Male: n = 50), with 55 confirmed for evaluation. The most common presentation included pain (67%), weight loss (65%), and jaundice (62%). Diffuse enlargement of the pancreas was evident in 38%, whilst multifocal, focal, or atrophic changes were seen in 7%, 33% and 9% respectively. 13% had no pancreatic parenchymal involvement. Peripheral rim enhancement was seen in 23 patients (42%). Where discernible, disease was a) Sclerosing pancreatitis and cholangitis, n = 21; b) Sclerosing cholangitis, n = 9; c) Sclerosing pancreatitis, n = 4; d) Sclerosing pancreatitis and cholangitis with pancreatic pseudotumour, n = 7; e) Sclerosing cholangitis with hepatic pseudotumour, n = 3; f) Sclerosing pancreatitis with pancreatic pseudotumour, n = 1. 56% of the patients had systemic manifestations and the median serum IgG4 at diagnosis was 5.12 g/L. The Korean criteria identified most patients (82%) compared to HISORt (55%) or the Japan Pancreas Society (56%). The majority (HISORt 60%; Japan Pancreas Society 55%; Korean 58%) met diagnostic criterion by radiological findings and elevated serum IgG4. Treatment and response did not differ when stratified by diagnostic criteria.CONCLUSION: Our descriptive and retrospective dataset confirms that in non-expert practice settings, autoimmune pancreatitis scoring systems with a focus on radiology and serology capture most patients who are clinically felt to have disease.</p
Immunochip analyses identify a novel risk locus for primary biliary cirrhosis at 13q14, multiple independent associations at four established risk loci and epistasis between 1p31 and 7q32 risk variants.
No full textImmunochip analyses identify a novel risk locus for primary biliary cirrhosis at 13q14, multiple independent associations at four established risk loci and epistasis between 1p31 and 7q32 risk variants
No full textTo further characterize the genetic basis of primary biliary cirrhosis (PBC), we genotyped 2426 PBC patients and 5731 unaffected controls from three independent cohorts using a single nucleotide polymorphism (SNP) array (Immunochip) enriched for autoimmune disease risk loci. Meta-analysis of the genotype data sets identified a novel disease-associated locus near the TNFSF11 gene at 13q14, provided evidence for association at six additional immune-related loci not previously implicated in PBC and confirmed associations at 19 of 22 established risk loci. Results of conditional analyses also provided evidence for multiple independent association signals at four risk loci, with haplotype analyses suggesting independent SNP effects at the 2q32 and 16p13 loci, but complex haplotype driven effects at the 3q25 and 6p21 loci. By imputing classical HLA alleles from this data set, four class II alleles independently contributing to the association signal from this region were identified. Imputation of genotypes at the non-HLA loci also provided additional associations, but none with stronger effects than the genotyped variants. An epistatic interaction between the IL12RB2 risk locus at 1p31and the IRF5 risk locus at 7q32 was also identified and suggests a complementary effect of these loci in predisposing to disease. These data expand the repertoire of genes with potential roles in PBC pathogenesis that need to be explored by follow-up biological studies.</p
Immunochip analyses identify a novel risk locus for primary biliary cirrhosis at 13q14, multiple independent associations at four established risk loci and epistasis between 1p31 and 7q32 risk variants
No full textA validated clinical tool for the prediction of varices in PBC: The Newcastle Varices in PBC Score
No full textImmunochip analyses identify a novel risk locus for primary biliary cirrhosis at 13q14, multiple independent associations at four established risk loci and epistasis between 1p31 and 7q32 risk variants.
No full textTo further characterize the genetic basis of primary biliary cirrhosis (PBC), we genotyped 2426 PBC patients and 5731 unaffected controls from three independent cohorts using a single nucleotide polymorphism (SNP) array (Immunochip) enriched for autoimmune disease risk loci. Meta-analysis of the genotype data sets identified a novel disease-associated locus near the TNFSF11 gene at 13q14, provided evidence for association at six additional immune-related loci not previously implicated in PBC and confirmed associations at 19 of 22 established risk loci. Results of conditional analyses also provided evidence for multiple independent association signals at four risk loci, with haplotype analyses suggesting independent SNP effects at the 2q32 and 16p13 loci, but complex haplotype driven effects at the 3q25 and 6p21 loci. By imputing classical HLA alleles from this data set, four class II alleles independently contributing to the association signal from this region were identified. Imputation of genotypes at the non-HLA loci also provided additional associations, but none with stronger effects than the genotyped variants. An epistatic interaction between the IL12RB2 risk locus at 1p31and the IRF5 risk locus at 7q32 was also identified and suggests a complementary effect of these loci in predisposing to disease. These data expand the repertoire of genes with potential roles in PBC pathogenesis that need to be explored by follow-up biological studies
The IRF5-TNPO3 association with systemic lupus erythematosus has two components that other autoimmune disorders variably share
No full textAdvance Access published on September 8, 2014Exploiting genotyping, DNA sequencing, imputation and trans-ancestral mapping, we used Bayesian and frequentist approaches to model the IRF5-TNPO3 locus association, now implicated in two immunotherapies and seven autoimmune diseases. Specifically, in systemic lupus erythematosus (SLE), we resolved separate associations in the IRF5 promoter (all ancestries) and with an extended European haplotype. We captured 3230 IRF5-TNPO3 high-quality, common variants across 5 ethnicities in 8395 SLE cases and 7367 controls. The genetic effect from the IRF5 promoter can be explained by any one of four variants in 5.7 kb (P-valuemeta = 6 × 10(-49); OR = 1.38-1.97). The second genetic effect spanned an 85.5-kb, 24-variant haplotype that included the genes IRF5 and TNPO3 (P-valuesEU = 10(-27)-10(-32), OR = 1.7-1.81). Many variants at the IRF5 locus with previously assigned biological function are not members of either final credible set of potential causal variants identified herein. In addition to the known biologically functional variants, we demonstrated that the risk allele of rs4728142, a variant in the promoter among the lowest frequentist probability and highest Bayesian posterior probability, was correlated with IRF5 expression and differentially binds the transcription factor ZBTB3. Our analytical strategy provides a novel framework for future studies aimed at dissecting etiological genetic effects. Finally, both SLE elements of the statistical model appear to operate in Sjögren's syndrome and systemic sclerosis whereas only the IRF5-TNPO3 gene-spanning haplotype is associated with primary biliary cirrhosis, demonstrating the nuance of similarity and difference in autoimmune disease risk mechanisms at IRF5-TNPO3.Leah C. Kottyan ... Maureen Rischmueller, Sue Lester ... et al
