Impact of Steroid Therapy on Early Growth in Infants with Biliary Atresia: The Multicenter Steroids in Biliary Atresia Randomized Trial

OBJECTIVE

To investigate the impact of corticosteroid therapy on the growth of participants in the Steroids in Biliary Atresia Randomized Trial (START) conducted through the Childhood Liver Disease Research Network. The primary analysis in START indicated that steroids did not have a beneficial effect on drainage in a cohort of infants with biliary atresia. We hypothesized that steroids would have a detrimental effect on growth in these infants.

STUDY DESIGN

A total of 140 infants were enrolled in START, with 70 randomized to each treatment arm: steroid and placebo. Length, weight, and head circumference were obtained at baseline and follow-up visits to 24 months of age.

RESULTS

Patients treated with steroids had significantly lower length and head circumference z scores during the first 3 months post-hepatoportoenterostomy (HPE), and significantly lower weight until 12 months. Growth trajectories in the steroid and placebo arms differed significantly for length (P < .0001), weight (P = .009), and head circumference (P < .0001) with the largest impact noted for those with successful HPE. Growth trajectory for head circumference was significantly lower in patients treated with steroids irrespective of HPE status, but recovered during the second 6 months of life.

CONCLUSIONS

Steroid therapy following HPE in patients with biliary atresia is associated with impaired length, weight, and head circumference growth trajectories for at least 6 months post-HPE, especially impacting infants with successful bile drainage.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00294684.

Cytokine-Producing B Cells Promote Immune-Mediated Bile Duct Injury in Murine Biliary Atresia

Biliary atresia (BA) is a neonatal T cell-mediated, inflammatory, sclerosing cholangiopathy. In the rhesus rotavirus (RRV)-induced neonatal mouse model of BA (murine BA), mice lacking B cells do not develop BA, and the lack of B cells is associated with loss of T-cell and macrophage activation. The aim of this study was to determine the mechanism of B cell-mediated immune activation (antigen presentation versus cytokine production) in murine BA. Normal neonatal B cells in the liver are predominantly at pro-B and pre-B cellular development. However, BA mice exhibit a significant increase in the number and activation status of mature liver B cells. Adoptively transferred B cells into RRV-infected, B cell-deficient mice were able to reinstate T-cell and macrophage infiltration and biliary injury. Nonetheless, neonatal liver B cells were incompetent at antigen presentation to T cells. Moreover, 3-83 immunoglobulin transgenic mice, in which B cells only present an irrelevant antigen, developed BA, indicating a B-cell antigen-independent mechanism. B cells from BA mice produced a variety of innate and adaptive immune cytokines associated with immune activation. In vitro trans-well studies revealed that BA B cells secreted cytokines that activated T cells based on increased expression of T-cell activation marker cluster of differentiation 69. Conclusion: Neonatal liver B cells are highly activated in murine BA and contribute to immune activation through production of numerous cytokines involved in innate and adaptive immunity; this work provides increased knowledge on the capacity of neonatal B cells to contribute to an inflammatory disease through cytokine-mediated mechanisms, and future studies should focus on targeting B cells as a therapeutic intervention in human BA.

Placebo-Controlled Randomized Trial of an Intestinal Bile Salt Transport Inhibitor for Pruritus in Alagille Syndrome

Medically refractory, severe, cholestasis-induced pruritus in Alagille syndrome may be improved by surgical interruption of the enterohepatic circulation. This multicenter trial (NCT02057692) tested the hypothesis that the intestinal bile acid transport inhibitor maralixibat would similarly reduce pruritus in Alagille syndrome. Thirty-seven children with Alagille syndrome were randomly assigned to double-blinded administration of placebo, 70, 140, or 280 µg/kg/day of maralixibat for 13 weeks. Pruritus was assessed by caregiver (itch-reported outcome instrument [ItchRO]) and clinician report (range, 0-4 [severe]). Liver chemistries and serum bile acids were measured. The primary outcome was the change from baseline to week 13 in ItchRO relative to placebo. In the a priori first analysis of the primary efficacy endpoint, the mean adjusted difference between participants receiving 140 or 280 µg/kg/day and placebo was -0.47 (95% confidence interval [CI], -1.14, 0.20; P = 0.16). Statistically significant decreases were observed with doses of 70 and 140 µg/kg/day (mean adjusted difference, -0.89; 95% CI, -1.70, -0.08; P = 0.032; and mean adjusted difference, -0.91; 95% CI, -1.62, -0.19; P = 0.014) but not 280 µg/kg/day (mean adjusted difference, -0.04; 95% CI, -0.94, 0.86; P = 0.44) or all doses combined (mean adjusted difference, -0.61; 95% CI, -1.24, 0.20; P = 0.055). A 1-point reduction in pruritus was more common in maralixibat-treated versus placebo-treated participants (caregiver ItchRO, 65% versus 25%; P = 0.06; clinician score, 76% versus 25%; P = 0.01). There were no significant changes in liver chemistries or bile acids relative to placebo. Adverse and serious adverse events were similar between maralixibat and placebo. Conclusion: Although the prespecified primary analyses of ItchRO were not all statistically significant, the data suggest that maralixibat is safe and may reduce pruritus in Alagille syndrome.

Biliary Atresia: Clinical and Research Challenges for the Twenty-First Century

Biliary atresia (BA) is a fibroinflammatory disease of the intrahepatic and extrahepatic biliary tree. Surgical hepatic portoenterostomy (HPE) may restore bile drainage, but progression of the intrahepatic disease results in complications of portal hypertension and advanced cirrhosis in most children. Recognizing that further progress in the field is unlikely without a better understanding of the underlying cause(s) and pathogenesis of the disease, the National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK) sponsored a research workshop focused on innovative and promising approaches and on identifying future areas of research. Investigators discussed recent advances using gestational ultrasound and results of newborn BA screening with serum direct (conjugated) bilirubin that support a prenatal onset of biliary injury. Experimental and human studies implicate the toxic properties of environmental toxins (e.g., biliatresone) and of viruses (e.g., cytomegalovirus) to the biliary system. Among host factors, sequence variants in genes related to biliary development and ciliopathies, a notable lack of a cholangiocyte glycocalyx and of submucosal collagen bundles in the neonatal extrahepatic bile ducts, and an innate proinflammatory bias of the neonatal immune system contribute to an increased susceptibility to damage and obstruction following epithelial injury. These advances form the foundation for a future research agenda focused on identifying the environmental and host factor(s) that cause BA, the potential use of population screening, studies of the mechanisms of prominent fibrosis in young infants, determinations of clinical surrogates of disease progression, and the design of clinical trials that target subgroups of patients with initial drainage following HPE. (Hepatology 2018; 00:000-000).

Use of Fully Covered Self-expanding Metal Biliary Stents in Pediatrics: A Case Series

OBJECTIVES

Endoscopic retrograde cholangiopancreatography is used to manage biliary pathology in pediatric patients. Plastic biliary stents have been used in this population for obstructive lesions and bile leaks; however, they are sometimes not effective due to migration, occlusion, or ineffective sealing. Fully covered self-expanding metal stents (FCSEMS) have larger diameters making them more suitable for some situations. Their use in pediatrics has, however, not been defined. The aim of the present study is to describe our experience with FCSEMS at our institution.

METHODS

We present a series of all patients who underwent FCSEMS placement at Children's Hospital Colorado including 3 adolescents and 1 young adult with complex medical needs.

RESULTS

Patient age range was 12 to 24 years and the weight ranged between 36 and 75 kg. All patients underwent previous endoscopic retrograde cholangiopancreatography and 1 or more rounds of plastic stenting without adequate clinical response before consideration of FCSEMS placement. Indications included recalcitrant biliary anastomotic stricture after liver transplant, persistent bile leak after needle perforation, recurrent obstructive choledocholithiasis after cholecystectomy, and malignant biliary stricture. Sizes of FCSEMS depended on patient bile duct size and biliary pathology. Dwell time was 6 to 8 weeks. Three patients had resolution of biliary pathology after FCSEMS therapy. One patient had distal migration of FCSEMS necessitating repeat stenting. There were no adverse events from FCSEMS placement or removal.

CONCLUSIONS

FCSEMS therapy should be considered in appropriate pediatric patients when plastic biliary stents are not effective. Further studies are needed to evaluate the safety and efficacy of FCSEMS in the pediatric age group.

Update on investigations pertaining to the pathogenesis of biliary atresia

Biliary atresia is a devastating biliary disease of neonates that results in liver transplantation for the vast majority. The etiology of biliary atresia is unknown and is likely multifactorial, with components of genetic predisposition, environmental trigger and autoimmunity contributing to disease pathogenesis. This review highlights recent work related to investigations of disease pathogenesis in biliary atresia.

Biliary atresia: Indications and timing of liver transplantation and optimization of pretransplant care

Biliary atresia (BA) is a progressive, fibro-obliterative disorder of the intrahepatic and extrahepatic bile ducts in infancy. The majority of affected children will eventually develop end-stage liver disease and require liver transplantation (LT). Indications for LT in BA include failed Kasai portoenterostomy, significant and recalcitrant malnutrition, recurrent cholangitis, and the progressive manifestations of portal hypertension. Extrahepatic complications of this disease, such as hepatopulmonary syndrome and portopulmonary hypertension, are also indications for LT. Optimal pretransplant management of these potentially life-threatening complications and maximizing nutrition and growth require the expertise of a multidisciplinary team with experience caring for BA. The timing of transplant for BA requires careful consideration of the potential risk of transplant versus the survival benefit at any given stage of disease. Children with BA often experience long wait times for transplant unless exception points are granted to reflect severity of disease. Family preparedness for this arduous process is therefore critical. Liver Transplantation 23:96-109 2017 AASLD.

CD4+ and CD8+ T Cell Activation in Children with Hepatitis C

OBJECTIVES

To assess if peripheral T cell populations in children with chronic hepatitis C virus (HCV) infection would show evidence of activation/exhaustion and an attenuated functional response.

STUDY DESIGN

Compared with adults, children with HCV infection have a higher rate of spontaneous viral clearance. In adults, chronic HCV has been linked to T cell exhaustion. Little is known of the immune status of children with HCV. Peripheral blood mononuclear cells were isolated from 16 children with HCV (6 males, 10 females; mean age 8.6 years, range 2-17), 16 age- and sex-matched control children without HCV infection, and 20 adults with chronic HCV. Multiparameter flow cytometry was performed to characterize T cell differences across the 3 groups.

RESULTS

Controls and children with HCV had similar levels of CD4(+), CD8(+), and γδ(+) T cells. Children with HCV demonstrated a decrease in naïve T cells compared with control children and increased activation/exhaustion marker expression on both CD8(+) and CD4(+) T cells. Transcription factor analysis suggested functional activation of T cells in children with HCV; however, only the CD4(+) subset had enhanced cytokine production (interferon gamma and interleukin-2) compared with control children.

CONCLUSIONS

The HCV response in children is characterized by several changes in T cell phenotype. Many of these changes, such as increased T cell expression of programmed cell death-1, are similar to responses in adults. Of note, cytokine production by CD4(+) helper T cells is increased in children with HCV compared with age- and sex-matched control children, which may influence long-term prognosis in children with HCV.

What Causes Biliary Atresia? Unique Aspects of the Neonatal Immune System Provide Clues to Disease Pathogenesis

Biliary atresia (BA) is the most frequent identifiable cause of neonatal cholestasis and the majority of patients will need liver transplantation for survival. Despite surgical intervention with the Kasai portoenterostomy, significant fibrosis and cirrhosis develops early in life. An increased understanding of what causes this inflammatory fibrosing cholangiopathy will lead to therapies aimed at protecting the intrahepatic biliary system from immune-mediated damage. This review focuses on studies pertaining to the role of the adaptive immune response in bile duct injury in BA, including cellular and humoral immunity. The neonatal presentation of BA begs the question of what are potential modifications of unique aspects of the neonatal immune system that "sets the stage" for the progressive biliary disease? Throughout this article, characteristics of the neonatal immune response are outlined and theories as to how alterations of this response could contribute to the pathogenesis of BA are discussed. These include aberrant Th1 and Th17 responses, deficiencies in regulatory T cells, activation of humoral immunity and autoimmunity. In order to advance our understanding of the etiology of BA, future studies should focus on those unique aspects of the neonatal immune system that have gone awry, as detailed throughout this review.

Extrahepatic anomalies in infants with biliary atresia: results of a large prospective North American multicenter study

The etiology of biliary atresia (BA) is unknown. Given that patterns of anomalies might provide etiopathogenetic clues, we used data from the North American Childhood Liver Disease Research and Education Network to analyze patterns of anomalies in infants with BA. In all, 289 infants who were enrolled in the prospective database prior to surgery at any of 15 participating centers were evaluated. Group 1 was nonsyndromic, isolated BA (without major malformations) (n = 242, 84%), Group 2 was BA and at least one malformation considered major as defined by the National Birth Defects Prevention Study but without laterality defects (n = 17, 6%). Group 3 was syndromic, with laterality defects (n = 30, 10%). In the population as a whole, anomalies (either major or minor) were most prevalent in the cardiovascular (16%) and gastrointestinal (14%) systems. Group 3 patients accounted for the majority of subjects with cardiac, gastrointestinal, and splenic anomalies. Group 2 subjects also frequently displayed cardiovascular (71%) and gastrointestinal (24%) anomalies; interestingly, this group had genitourinary anomalies more frequently (47%) compared to Group 3 subjects (10%).

CONCLUSION

This study identified a group of BA (Group 2) that differed from the classical syndromic and nonsyndromic groups and that was defined by multiple malformations without laterality defects. Careful phenotyping of the patterns of anomalies may be critical to the interpretation of both genetic and environmental risk factors associated with BA, allowing new insight into pathogenesis and/or outcome.

Regulatory T cells inhibit Th1 cell-mediated bile duct injury in murine biliary atresia

BACKGROUND & AIMS

Biliary atresia (BA) is a pediatric inflammatory disease of the biliary system which leads to cirrhosis and the need for liver transplantation. One theory regarding etiology is that bile duct injury is due to virus-induced autoreactive T cell-mediated inflammation. Regulatory T cell (Treg) abnormalities in BA could result in unchecked bystander inflammation and autoimmunity targeting bile ducts. The aim of this study was to determine if Tregs are dysfunctional in the rotavirus-induced mouse model of BA (murine BA).

METHODS

Murine BA resulted from infection of BALB/c neonates with Rhesus rotavirus (RRV).

RESULTS

Liver Tregs from BA mice were decreased in number, activation marker expression, and suppressive function. Adoptive transfer studies revealed that RRV-infected mice that received Tregs had significantly increased survival (84%) compared to controls (12.5%). In addition, ablation of Tregs in older mice, followed by RRV infection, resulted in increased bile duct injury.

CONCLUSIONS

These studies demonstrate that dysregulation of Tregs is present in murine BA and that diminished Treg function may be implicated in the pathogenesis of human BA.

B cell deficient mice are protected from biliary obstruction in the rotavirus-induced mouse model of biliary atresia

A leading theory regarding the pathogenesis of biliary atresia (BA) is that bile duct injury is initiated by a virus infection, followed by an autoimmune response targeting bile ducts. In experimental models of autoimmune diseases, B cells have been shown to play an important role. The aim of this study was to determine the role of B cells in the development of biliary obstruction in the Rhesus rotavirus (RRV)-induced mouse model of BA. Wild-type (WT) and B cell-deficient (Ig-α(-/-)) mice received RRV shortly after birth. Ig-α(-/-) RRV-infected mice had significantly increased disease-free survival rate compared to WT RRV-infected BA mice (76.8% vs. 17.5%). In stark contrast to the RRV-infected BA mice, the RRV-infected Ig-α(-/-) mice did not have hyperbilirubinemia or bile duct obstruction. The RRV-infected Ig-α(-/-) mice had significantly less liver inflammation and Th1 cytokine production compared to RRV-infected WT mice. In addition, Ig-α(-/-) mice had significantly increased numbers of regulatory T cells (Tregs) at baseline and after RRV infection compared to WT mice. However, depletion of Tregs in Ig-α(-/-) mice did not induce biliary obstruction, indicating that the expanded Tregs in the Ig-α(-/-) mice were not the sole reason for protection from disease. Conclusion : B cell deficient Ig-α(-/-) mice are protected from biliary obstruction in the RRV-induced mouse model of BA, indicating a primary role of B cells in mediating disease pathology. The mechanism of protection may involve lack of B cell antigen presentation, which impairs T-cell activation and Th1 inflammation. Immune modulators that inhibit B cell function may be a new strategy for treatment of BA.

Lack of HLA predominance and HLA shared epitopes in biliary Atresia

Biliary atresia (BA) is characterized by progressive inflammation and fibrosis of bile ducts. A theory of pathogenesis entails autoimmune-mediated injury targeting bile duct epithelia. One of the strongest genetic associations with autoimmunity is with HLA genes. In addition, apparently dissimilar HLA alleles may have similar antigen-binding sites, called shared epitopes, that overlap in their capacity to present antigens. In autoimmune disease, the incidence of the disease may be related to the presence of shared epitopes, not simply the HLA allelic association. Aim: To determine HLA allele frequency (high-resolution genotyping) and shared epitope associations in BA. Results: Analysis of every allele for HLA-A, -B, -C, -DRB1, -DPB1 and -DQB1 in 180 BA and 360 racially-matched controls did not identify any significant HLA association with BA. Furthermore, shared epitope analysis of greater than 10 million possible combinations of peptide sequences was not different between BA and controls. Conclusions: This study encompasses the largest HLA allele frequency analysis for BA in the United States and is the first study to perform shared epitope analysis. When controlling for multiple comparisons, no HLA allele or shared epitope association was identified in BA. Future studies of genetic links to BA that involve alterations of the immune response should include investigations into defects in regulatory T cells and non-HLA linked autoinflammatory diseases.

Clues to the etiology of bile duct injury in biliary atresia

Biliary atresia (BA) is an infantile obstructive cholangiopathy of unknown etiology with suboptimal therapy, which is responsible for 40 to 50% of all pediatric liver transplants. Although the etiology of bile duct injury in BA in unknown, it is postulated that a pre- or perinatal viral infection initiates cholangiocyte apoptosis and release of antigens that trigger a Th1 immune response that leads to further bile duct injury, inflammation, and obstructive fibrosis. Humoral immunity and activation of the innate immune system may also play key roles in this process. Moreover, recent investigations from the murine BA model and human data suggest that regulatory T cells and genetic susceptibility factors may orchestrate autoimmune mechanisms. What controls the coordination of these events, why the disease only occurs in the first few months of life, and why a minority of infants with perinatal viral infections develop BA are remaining questions to be answered.

Biliary atresia: cellular dynamics and immune dysregulation

The cause of biliary atresia is unknown; in the past few decades, the majority of investigations related to its pathogenesis have centered on viral infections and immunity. The acquired or perinatal form of biliary atresia entails a progressive inflammatory injury of bile ducts, leading to fibrosis and obliteration of both the extrahepatic and intrahepatic bile ducts. Theories of pathogenesis include viral infection, chronic inflammatory or autoimmune-mediated bile duct injury, and abnormalities in bile duct development. This review will focus solely on human studies pertaining to a potential viral trigger of bile duct injury at diagnosis and provide insight into the interplay of the innate and adaptive immune responses in the pathogenesis of disease.

Generation of a cholangiocyte-specific cDNA expression library for the identification of B and T cell autoantigens in murine biliary disease

AIM

  Several mouse models of inflammatory cholangiopathies exist, including biliary atresia, primary biliary cirrhosis, autoimmune hepatitis, and primary sclerosing cholangitis. In an ongoing effort to identify the target antigens of both infiltrating autoreactive T cells and serum autoantibodies, we aimed to generate a cholangiocyte-derived cDNA library capable of expressing a wide variety of proteins.

METHODS

  mRNA was isolated from a normal mouse cholangiocyte cell line and reverse transcribed into cDNA. After initial cloning of the cDNA into a transfer vector (pDONR222), the entire library was shuttled into an Escherichia coli expression vector (pDEST160).

RESULTS

  The library contains 2.3 × 10(6) independent clones and expresses proteins up to 100 kD in molecular weight. Using a variety of techniques, including western blot analysis, mass spectrometry of individual clones, and direct DNA sequencing of plasmids, a number of both ubiquitously expressed and cholangiocyte-specific proteins (e.g. cytokeratin 19) have been identified within.

CONCLUSION

  A comprehensive mouse cholangiocyte cDNA expression library has been generated and is available for use as a source of multiple cholangiocyte-specific antigens for immunological studies. The library can be used to screen for specificity of T cell lines or hybridomas. Furthermore, this library has potential uses in SEREX analysis of autoantibody reactivity. The cholangiocyte-specific cDNA library is a powerful tool for the identification of target antigens in murine inflammatory cholangiopathies and is available as a shared resource.

Cytomegalovirus-specific T-cell reactivity in biliary atresia at the time of diagnosis is associated with deficits in regulatory T cells

Biliary atresia (BA) is a progressive, inflammatory cholangiopathy that culminates in fibrosis of extrahepatic and intrahepatic bile ducts. A leading theory on the pathogenesis of BA is that the bile duct damage is initiated by a virus infection, followed by a bile duct-targeted autoimmune response. One mechanism of autoimmunity entails a diminished number or function of regulatory T cells (Tregs). The aim of this study was to identify potential virus-specific liver T cells from infants with BA at the time of diagnosis, implicating the virus involved in early bile duct damage. A subaim was to determine if the presence of virus infection was associated with quantitative changes in Tregs. Liver T cells from BA and control patients were cultured with antigen-presenting cells in the presence of a variety of viral or control proteins. 56% of BA patients had significant increases in interferon-gamma-producing liver T cells in response to cytomegalovirus (CMV), compared with minimal BA responses to other viruses or the control group CMV response. In addition, a positive correlation between BA plasma CMV immunoglobulin M (IgM) and liver T-cell CMV reactivity was identified. Investigation of peripheral blood Tregs revealed significant deficits in Treg frequencies in BA compared with controls, with marked deficits in those BA patients who were positive for CMV.

CONCLUSION

Liver T-cell responses to CMV were identified in the majority of BA patients at diagnosis, suggesting perinatal CMV infection as a plausible initiator of bile duct damage. Deficiency of Tregs in BA implies decreased inhibition of inflammation and autoreactivity, potentially allowing for exaggerated bile duct injury.

Biosorptive recovery of platinum from platinum group metal refining wastewaters by immobilised Saccharomyces cerevisiae

The process of platinum group metal (PGM) refining can be up to 99.99% efficient at best, and although it may seem small, the amount of valuable metal lost to waste streams is appreciable enough to warrant recovery. The method currently used to remove entrained metal ions from refinery wastewaters, chemical precipitation, is not effective for selective recovery of PGMs. The yeast Saccharomyces cerevisiae has been found capable of sorbing numerous precious and base metals, and is a cheap and abundant source of biomass. In this investigation, S. cerevisiae was immobilised using polyethyleneimine and glutaraldehyde to produce a suitable sorbent, capable of high platinum uptake (150-170 mg/g) at low pH (<2). The sorption mechanism was found to be a chemical reaction, which made effective desorption impossible. When applied to PGM refinery wastewater, two key wastewater characteristics limited the success of the sorption process; high inorganic ion content and complex speciation of the platinum ions. The results proved the concept principle of platinum recovery by immobilised yeast biosorption and indicated that a more detailed understanding of the platinum speciation within the wastewater is required before biosorption can be applied. Overall, the sorption of platinum by the S. cerevisiae sorbent was demonstrated to be highly effective in principle, but the complexity of the wastewater requires that pretreatment steps be taken before the successful application of this process to industrial wastewater.

Treatment of neonatal hemochromatosis with exchange transfusion and intravenous immunoglobulin

OBJECTIVE

To determine if immunomodulatory treatment including intravenous immunoglobulin (IVIG) can favorably affect survival in neontatal hemochromatosis (NH) diagnosed postnatally because it can effectively prevent occurrence of NH when applied during gestations at risk.

STUDY DESIGN

We treated 16 newborn infants with liver failure due to NH with high-dose IVIG, in combination with exchange transfusion in 13 (ET/IVIG), and compared the outcome with 131 historical controls treated conventionally.

RESULTS

The severity of liver disease as estimated by prothrombin time was similar in the subjects receiving ET/IVIG and the historical controls, and the medical therapy was equivalent with the exception of the ET/IVIG therapy. Twelve subjects (75%) had good outcome, defined as survival without liver transplantation, whereas good outcome was achieved in only 17% (23/131) of historical control patients (P < .001). Four subjects died, 2 without and 2 after liver transplant. Survivors were discharged 6 to 90 days after receiving ET/IVIG therapy, and those followed for more than 1 year are within normal measures for growth, development, and liver function.

CONCLUSIONS

Immune therapy with ET/IVIG appears to improve the outcome and reduce the need for liver transplantation in patients with NH.

Cholangiocytes as immune modulators in rotavirus-induced murine biliary atresia

BACKGROUND/AIMS

Biliary atresia (BA) is a progressive disease characterized by bile duct inflammation and fibrosis. The aetiology is unknown and may be due to a virus-induced, autoimmune-mediated injury of cholangiocytes. Cholangiocytes are not only targets of injury but may also modulate hepatic inflammation. The aim of this study was to determine the immune profile of murine cholangiocytes and the ability to function as antigen-presenting cells (APCs) in culture with Rhesus rotavirus (RRV), poly I:C (viral mimic) or interferon-gamma/tumour necrosis factor-alpha.

METHODS/RESULTS

Both the cholangiocyte cell line (long-term culture) and fresh, ex vivo cholangiocytes expressed APC surface markers major histocompatibility complex (MHC)-class I and II and CD40, while only the cultured cell line expressed costimulatory molecules B7-1 and B7-2. Despite APC expression, cultured cholangiocytes were unable to function as competent APCs in T-cell proliferation assays. Furthermore, both cultured and ex vivo cholangiocytes expressed RNA transcripts for many pro-inflammatory cytokines and chemokines.

CONCLUSIONS

Although cholangiocytes contain APC molecules, they are incompetent at antigen presentation and cannot elicit effective T-cell activation. Upregulation of MHC-class I and II found in BA mice may serve to prime the cholangiocyte as a target for immune-mediated injury. Cholangiocytes produced many pro-inflammatory cytokines and chemokines in the setting of RRV infection and T-helper type 1 cytokine milieu, suggesting a role of cholangiocytes as immune modulators promoting the ongoing inflammation that exists in RRV-induced BA.

The pathogenesis of biliary atresia: evidence for a virus-induced autoimmune disease

Biliary atresia is a mystifying cause of neonatal cholestasis, manifested by progressive inflammation and fibrosis of both the extrahepatic and intrahepatic bile ducts. It is a devastating disease that leads to cirrhosis and the need for liver transplantation in the majority of children. The etiology is unknown, and one theory is that it may involve a primary perinatal hepatobiliary viral infection and a secondary generation of an autoimmune-mediated bile duct injury. This review will outline the evidence from both human and murine studies supporting a potential cholangiotropic viral infection as the initiator of bile duct injury in biliary atresia and the role of the adaptive immune response and autoimmunity in progression of disease. Delineating the pathways of immune and autoimmune-mediated bile duct injury within biliary atresia could stimulate development of new medical interventions aimed at suppressing the specific immune response, decreasing the inflammatory damage to bile ducts, and delaying or negating the need for liver transplantation.

Progressive biliary destruction is independent of a functional tumor necrosis factor-alpha pathway in a rhesus rotavirus-induced murine model of biliary atresia

Rhesus rotavirus (RRV)-inoculated neonatal BALB/c mice develop an immune-mediated inflammation of extra- and intrahepatic bile ducts that progresses to biliary obstruction and death by 3 wk of age. Livers of diseased animals demonstrate increased numbers of T lymphocytes with elevated expression of helper T cell type 1 (Th1) cytokines at 1 wk, which transitions to increased numbers of macrophages and high expression of the proinflammatory cytokine tumor necrosis factor (TNF)-alpha by 2 wk. We employed both pharmacologic and genetic approaches for attenuation of TNF-alpha to determine whether it plays a causal role in injury. First, RRV-inoculated BALB/c mice were subjected to multiple treatments with either the TNF receptor I (TNF-RI)-Fc fusion protein etanercept or neutralizing antibodies to mouse TNF-alpha. Also, TNF-RI(-/-) mice were injected with RRV in the same manner as wild-type mice. In all cases, TNF inhibition did not reduce the severity or incidence of disease. Survival curves of mice given blocking agents were similar to those of control RRV-inoculated mice, and survival of challenged TNF-RI(-/-) mice was worse than that of wild-type mice, likely because of the prolonged presence of infectious RRV. In all experimental groups, markers of disease were unchanged from those of control mice. In summary, although RRV-inoculated BALB/c mice have highly elevated expression of TNF-alpha, this cytokine does not play an obligate role in disease progression.