Immunological gap in the infectious animal model for biliary atresia

Biliatresone induces cholangiopathy in C57BL/6J neonates

Exposure to plant toxins or microbiota that are able to digest common food ingredients to toxic structures might be responsible for biliary atresia (BA). An isoflavonoid, biliatresone is known to effectively alter the extrahepatic bile duct (EHBD) development in BALB/c mice. Biliatresone causes a reduction of Glutathione (GSH) levels, SOX17 downregulation and is effectively countered with N-Acetyl-L-cysteine treatment in vitro. Therefore, reversing GSH-loss appears to be a promising treatment target for a translational approach. Since BALB/c mice have been described as sensitive in various models, we evaluated the toxic effect of biliatresone in robust C57BL/6J mice and confirmed its toxicity. Comparison between BALB/c and C57BL/6J mice revealed similarity in the toxic model. Affected neonates exhibited clinical symptoms of BA, such as jaundice, ascites, clay-colored stools, yellow urine and impaired weight gain. The gallbladders of jaundiced neonates were hydropic and EHBD were twisted and enlarged. Serum and histological analysis proved cholestasis. No anomalies were seen in the liver and EHBD of control animals. With our study we join a chain of evidence confirming that biliatresone is an effective agent for cross-lineage targeted alteration of the EHBD system.

Increased Risk of Neurological Disease Following Pediatric Rotavirus Infection: A Two-Center Case-Control Study

BACKGROUND

Whether pediatric rotavirus infection is associated with extraintestinal complications remains unknown.

METHODS

We conducted a case-control study to investigate the incidences and risks of rotavirus-associated extraintestinal complications in hospitalized newborns, infants, and children younger than 5 years.

RESULTS

A total of 1325 young inpatients with rotavirus infection (754 male and 539 newborns) and 1840 controls without rotavirus infection (1035 male and 836 newborns) were included. The incidences of neurological disease were higher among rotavirus individuals compared with controls: newborns, 7.24% (39/539) versus 2.87% (24/836), P < .001; infants and young children, 19.59% (154/786) versus 12.35% (124/1004), P < .001. The associated odd ratios (ORs) for neurological disease frequency following rotavirus infection was 2.64 (95% confidence interval [CI], 1.57-4.44) for newborns and 1.73 (95% CI, 1.34-2.24) for infants and young children, which increased to 2.56 (95% CI, 1.57-4.18) in case-control (1:1) matching analysis and 1.85 (95% CI, 1.41-2.42) in confounder adjustment. Rotavirus infection was associated with other extraintestinal complications, depending on study population and disease severity. Outcome analysis revealed rotavirus infection and its consequences had a significant impact on hospitalization and discharge.

CONCLUSIONS

Rotavirus exposure was associated with a spectrum of extraintestinal complications, particularly neurological disease. Rotavirus infection and subsequent consequences resulted in poor clinical outcomes.

Update on Etiology and Pathogenesis of Biliary Atresia

Biliary atresia is a rare inflammatory sclerosing obstructive cholangiopathy that initiates in infancy as complete choledochal blockage and progresses to the involvement of intrahepatic biliary epithelium. Growing evidence shows that biliary atresia is not a single entity with a single etiology but a phenotype resulting from multifactorial events whose common path is obliterative cholangiopathy. The etiology of biliary atresia has been explained as resulting from genetic variants, toxins, viral infection, chronic inflammation or bile duct lesions mediated by autoimmunity, abnormalities in the development of the bile ducts, and defects in embryogenesis, abnormal fetal or prenatal circulation and susceptibility factors. It is increasingly evident that the genetic and epigenetic predisposition combined with the environmental factors to which the mother is exposed are potential triggers for biliary atresia. There is also an indication that a progressive thickening of the arterial middle layer occurs in this disease, suggestive of vascular remodeling and disappearance of the interlobular bile ducts. It is suggested that the hypoxia/ischemia process can affect portal structures in biliary atresia and is associated with both the extent of biliary proliferation and the thickening of the medial layer.

Rotavirus-related systemic diseases: clinical manifestation, evidence and pathogenesis

Rotaviruses, double-stranded, non-enveloped RNA viruses, are a global health concern, associated with acute gastroenteritis and secretory-driven watery diarrhoea, especially in infants and young children. Conventionally, rotavirus is primarily viewed as a pathogen for intestinal enterocytes. This notion is challenged, however, by data from patients and animal models documenting extra-intestinal clinical manifestations and viral replication following rotavirus infection. In addition to acute gastroenteritis, rotavirus infection has been linked to various neurological disorders, hepatitis and cholestasis, type 1 diabetes, respiratory illness, myocarditis, renal failure and thrombocytopenia. Concomitantly, molecular studies have provided insight into potential mechanisms by which rotavirus can enter and replicate in non-enterocyte cell types and evade host immune responses. Nevertheless, it is fair to say that the extra-intestinal aspect of the rotavirus infectious process is largely being overlooked by biomedical professionals, and there are gaps in the understanding of mechanisms of pathogenesis. Thus with the aim of increasing public and professional awareness we here provide a description of our current understanding of rotavirus-related extra-intestinal clinical manifestations and associated molecular pathogenesis. Further understanding of the processes involved should prove exceedingly useful for future diagnosis, treatment and prevention of rotavirus-associated disease.

Liver Immune Profiling Reveals Pathogenesis and Therapeutics for Biliary Atresia

Biliary atresia (BA) is a severe cholangiopathy that leads to liver failure in infants, but its pathogenesis remains to be fully characterized. By single-cell RNA profiling, we observed macrophage hypo-inflammation, Kupffer cell scavenger function defects, cytotoxic T cell expansion, and deficiency of CX3CR1⁺effector T and natural killer (NK) cells in infants with BA. More importantly, we discovered that hepatic B cell lymphopoiesis did not cease after birth and that tolerance defects contributed to immunoglobulin G (IgG)-autoantibody accumulation in BA. In a rhesus-rotavirus induced BA model, depleting B cells or blocking antigen presentation ameliorated liver damage. In a pilot clinical study, we demonstrated that rituximab was effective in depleting hepatic B cells and restoring the functions of macrophages, Kupffer cells, and T cells to levels comparable to those of control subjects. In summary, our comprehensive immune profiling in infants with BA had educed that B-cell-modifying therapies may alleviate liver pathology.

Innate Immunity and Pathogenesis of Biliary Atresia

Biliary atresia (BA) is a devastating fibro-inflammatory disease characterized by the obstruction of extrahepatic and intrahepatic bile ducts in infants that can have fatal consequences, when not treated in a timely manner. It is the most common indication of pediatric liver transplantation worldwide and the development of new therapies, to alleviate the need of surgical intervention, has been hindered due to its complexity and lack of understanding of the disease pathogenesis. For that reason, significant efforts have been made toward the development of experimental models and strategies to understand the etiology and disease mechanisms and to identify novel therapeutic targets. The only characterized model of BA, using a Rhesus Rotavirus Type A infection of newborn BALB/c mice, has enabled the identification of key cellular and molecular targets involved in epithelial injury and duct obstruction. However, the establishment of an unleashed chronic inflammation followed by a progressive pathological wound healing process remains poorly understood. Like T cells, macrophages can adopt different functional programs [pro-inflammatory (M1) and resolutive (M2) macrophages] and influence the surrounding cytokine environment and the cell response to injury. In this review, we provide an overview of the immunopathogenesis of BA, discuss the implication of innate immunity in the disease pathogenesis and highlight their suitability as therapeutic targets.

A Phase I/IIa Trial of Intravenous Immunoglobulin Following Portoenterostomy in Biliary Atresia

OBJECTIVES

Biliary atresia (BA) is a progressive neonatal fibroinflammatory cholangiopathy. We hypothesized that intravenous immunoglobulin (IVIg) would be safe, feasible, acceptable, and efficacious for the treatment of BA. The primary objective of this study was to establish the feasibility, acceptability, and safety profile of IVIg administration after hepatoportoenterostomy (HPE) in BA. The secondary objective was to determine the treatment efficacy of IVIg based on good bile drainage and survival with the native liver.

METHODS

A multicenter, prospective, open-labeled, phase I/IIA trial of IVIg was conducted, with 1 g/kg/dose of IVIg infused at 3-5, 30, and 60 days post-HPE, and subjects followed for 360 days post-HPE. Twenty-nine participants completed the study.

RESULTS

Administration of IVIg infusions was feasible and acceptable in 79%. None of the serious adverse events (SAEs) were directly related to IVIg infusions; however, 90% of participants had an SAE. Compared with a historical placebo-arm group, there was no significant increase in the proportion of IVIg participants with a serum total bilirubin <1.5 mg/dL at 90, 180, or 360 days post-HPE. Survival with the native liver in the IVIg participants showed no significant benefit over the historical placebo arm, with a difference at 360 days of -11.9% (IVIg: 58.6%, placebo: 70.5%; 90% UCB: 2.1%; P > 0.05).

CONCLUSIONS

Although IVIg infusions in infants with BA post-HPE were feasible, acceptable and safe, there was no trend to lower bilirubin levels or improved 360-day survival with the native liver.

CLINICAL TRIAL

Safety Study of Intravenous Immunoglobulin Post-Portoenterostomy in Biliary Atresia; #NCT01854827.

A Rotavirus-Induced Mouse Model to Study Biliary Atresia and Neonatal Cholestasis

Biliary atresia is a devastating neonatal cholangiopathy that affects both extra- and intrahepatic bile ducts progressing to fibrosis and end-stage liver disease by 2 years of age. Despite re-establishment of biliary drainage following a Kasai portoenterostomy (surgical procedure), many infants develop fibrosis requiring liver transplant. In the murine model of biliary atresia, rhesus rotavirus infection of newborn pups results in a cholangiopathy paralleling human biliary atresia and is used to study mechanistic aspects of the disease. The infected mice displayed histopathological signs similar to human biliary atresia, with bile duct obstruction, bile duct proliferation, and liver inflammation with fibrosis.

Role of viruses in biliary atresia: news from mice and men

Biliary atresia (BA) is still an enigmatic disease of unknown etiology and cryptic pathomechanism. Despite the fact that BA is rated among rare diseases, it represents the most frequent indication for pediatric liver transplantation. Although every effort is made to elucidate the origin of the ongoing deterioration of liver function, no breakthrough has so far been achieved, which switches the surgical but symptomatic therapy to a cause-oriented approach. The nowadays leading hypothesis focuses on hepatotropic virus as a triggering agent for an autoimmunological self-limiting inflammatory process along the entire biliary tree. The present review highlights the current state of research on the factor "viruses in biliary atresia" in both patients undergoing the Kasai procedure and the virus-induced BA mouse model.

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.

A Point Mutation in the Rhesus Rotavirus VP4 Protein Generated through a Rotavirus Reverse Genetics System Attenuates Biliary Atresia in the Murine Model

Rotavirus infection is one of the most common causes of diarrheal illness in humans. In neonatal mice, rhesus rotavirus (RRV) can induce biliary atresia (BA), a disease resulting in inflammatory obstruction of the extrahepatic biliary tract and intrahepatic bile ducts. We previously showed that the amino acid arginine (R) within the sequence SRL (amino acids 445 to 447) in the RRV VP4 protein is required for viral binding and entry into biliary epithelial cells. To determine if this single amino acid (R) influences the pathogenicity of the virus, we generated a recombinant virus with a single amino acid mutation at this site through a reverse genetics system. We demonstrated that the RRV mutant (RRV^VP4-R446G) produced less symptomatology and replicated to lower titers both in vivo and in vitro than those seen with wild-type RRV, with reduced binding in cholangiocytes. Our results demonstrate that a single amino acid change in the RRV VP4 gene influences cholangiocyte tropism and reduces pathogenicity in mice.IMPORTANCE Rotavirus is the leading cause of diarrhea in humans. Rhesus rotavirus (RRV) can also lead to biliary atresia (a neonatal human disease) in mice. We developed a reverse genetics system to create a mutant of RRV (RRV^VP4-R446G) with a single amino acid change in the VP4 protein compared to that of wild-type RRV. In vitro, the mutant virus had reduced binding and infectivity in cholangiocytes. In vivo, it produced fewer symptoms and lower mortality in neonatal mice, resulting in an attenuated form of biliary atresia.

The SRL peptide of rhesus rotavirus VP4 protein governs cholangiocyte infection and the murine model of biliary atresia

Biliary atresia (BA) is a neonatal obstructive cholangiopathy that progresses to end-stage liver disease, often requiring transplantation. The murine model of BA, employing rhesus rotavirus (RRV), parallels human disease and has been used to elucidate mechanistic aspects of a virus induced biliary cholangiopathy. We previously reported that the RRV VP4 gene plays an integral role in activating the immune system and induction of BA. Using rotavirus binding and blocking assays, this study elucidated how RRV VP4 protein governs cholangiocyte susceptibility to infection both in vitro and in vivo in the murine model of BA. We identified the amino acid sequence on VP4 and its cholangiocyte binding protein, finding that the sequence is specific to those rotavirus strains that cause obstructive cholangiopathy. Pretreatment of murine and human cholangiocytes with this VP4-derived peptide (TRTRVSRLY) significantly reduced the ability of RRV to bind and infect cells. However, the peptide did not block cholangiocyte binding of TUCH and Ro1845, strains that do not induce murine BA. The SRL sequence within TRTRVSRLY is required for cholangiocyte binding and viral replication. The cholangiocyte membrane protein bound by SRL was found to be Hsc70. Inhibition of Hsc70 by small interfering RNAs reduced RRV's ability to infect cholangiocytes. This virus-cholangiocyte interaction is also seen in vivo in the murine model of BA, where inoculation of mice with TRTRVSRLY peptide significantly reduced symptoms and mortality in RRV-injected mice.

CONCLUSION

The tripeptide SRL on RRV VP4 binds to the cholangiocyte membrane protein Hsc70, defining a novel binding site governing VP4 attachment. Investigations are underway to determine the cellular response to this interaction to understand how it contributes to the pathogenesis of BA. (Hepatology 2017;65:1278-1292).

Rhesus rotavirus VP6 regulates ERK-dependent calcium influx in cholangiocytes

The Rhesus rotavirus (RRV) induced murine model of biliary atresia (BA) is a useful tool in studying the pathogenesis of this neonatal biliary obstructive disease. In this model, the mitogen associated protein kinase pathway is involved in RRV infection of biliary epithelial cells (cholangiocytes). We hypothesized that extracellular signal-related kinase (ERK) phosphorylation is integral to calcium influx, allowing for viral replication within the cholangiocyte. Utilizing ERK and calcium inhibitors in immortalized cholangiocytes and BALB/c pups, we determined that ERK inhibition resulted in reduced viral yield and subsequent decreased symptomatology in mice. In vitro, the RRV VP6 protein induced ERK phosphorylation, leading to cellular calcium influx. Pre-treatment with an ERK inhibitor or Verapamil resulted in lower viral yields. We conclude that the pathogenesis of RRV-induced murine BA is dependent on the VP6 protein causing ERK phosphorylation and triggering calcium influx allowing replication in cholangiocytes.

Targeting Extracellular Cyclophilins Ameliorates Disease Progression in Experimental Biliary Atresia

Biliary atresia (BA) is a devastating liver disease of unknown etiology affecting children generally within the first 3 months of life. The disease is manifested by inflammation and subsequent obstruction of the extrahepatic bile ducts, fibrosis and liver failure. The mechanisms responsible for disease pathogenesis are not fully understood, but a number of factors controlled by the SMAD signaling pathway have been implicated. In this study, we investigated the role of a known proinflammatory factor, extracellular cyclophilin A (CypA), in the pathogenesis of biliary atresia using the rhesus rotavirus (RRV) murine model. We used a unique cyclosporine A derivative, MM284, which does not enter cells and therefore inactivates exclusively extracellular cyclophilins, as a potential treatment. We demonstrated that levels of CypA in plasma of RRV-infected mice were increased significantly, and that treatment of mice with MM284 prior to or one day after disease initiation by RRV infection significantly improved the status of mice with experimental BA: weight gain was restored, bilirubinuria was abrogated, liver infiltration by inflammatory cells was reduced and activation of the SMAD pathway and SMAD-controlled fibrosis mediators and tissue inhibitor of metalloproteinases (TIMP)-4 and matrix metalloproteinase (MMP)-7 was alleviated. Furthermore, treatment of human hepatic stellate cells with recombinant cyclophilin recapitulated SMAD2/3 activation, which was also suppressed by MM284 treatment. Our data provide the first evidence that extracellular cyclophilins activate the SMAD pathway and promote inflammation in experimental BA, and suggest that MM284 may be a promising therapeutic agent for treating BA and possibly other intrahepatic chronic disorders.

The Sea Lamprey as an Etiological Model for Biliary Atresia

Biliary atresia (BA) is a progressive, inflammatory, and fibrosclerosing cholangiopathy in infants that results in obstruction of both extrahepatic and intrahepatic bile ducts. It is the most common cause for pediatric liver transplantation. In contrast, the sea lamprey undergoes developmental BA with transient cholestasis and fibrosis during metamorphosis, but emerges as a fecund adult with steatohepatitis and fibrosis in the liver. In this paper, we present new histological evidence and compare the sea lamprey to existing animal models to highlight the advantages and possible limitations of using the sea lamprey to study the etiology and compensatory mechanisms of BA and other liver diseases. Understanding the signaling factors and genetic networks underlying lamprey BA can provide insights into BA etiology and possible targets to prevent biliary degeneration and to clear fibrosis. In addition, information from lamprey BA can be used to develop adjunct treatments for patients awaiting or receiving surgical treatments. Furthermore, the cholestatic adult lamprey has unique adaptive mechanisms that can be used to explore potential treatments for cholestasis and nonalcoholic steatohepatitis (NASH).

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.

Prevalence of groups A and C rotavirus antibodies in infants with biliary atresia and cholestatic controls

OBJECTIVE

To analyze the prevalence of acute asymptomatic group A and C rotavirus (RV-A and RV-C) infection in neonates with cholestasis.

STUDY DESIGN

Participants were infants <180 days of age with cholestasis (serum direct or conjugated bilirubin >20% of total and ≥2 mg/dL) enrolled in the Childhood Liver Disease Research and Education Network during RV season (December-May). Forty infants with biliary atresia (BA), age 62 ± 29 days (range, 4.7-13 weeks) and 38 infants with cholestasis, age 67 ± 44 days (range, 3-15.8 weeks) were enrolled.

RESULTS

At enrollment, RV-A IgM positivity rates did not differ between infants with BA (10%) vs those without (18%) (P = .349). RV-C IgM was positive in 0% of infants with BA vs 3% in those without BA (P = .49). RV-A IgG was lower in infants with BA: 51 ± 39 vs 56 ± 44 enzyme-linked immunoassay unit, P = .045 but this difference may lack biological relevance as maternal RV-A IgG titers were similar between groups. Infant RV-A IgM titers at 2-6 months follow-up increased markedly vs at presentation in both infants with BA (50 ± 30 vs 9 ± 9) and those without (43 ± 18 vs 16 ± 20 enzyme-linked immunoassay unit) (P < .0001), without differences between groups.

CONCLUSIONS

RV-A infection in the first 6 months of life is common in infants with cholestasis of any cause. RV-A could have different pathogenetic effects by initiating different hepatic immune responses in infants with vs without BA or could lack pathogenetic significance.

Hepatocytes buried in the cirrhotic livers of patients with biliary atresia proliferate and function in the livers of urokinase-type plasminogen activator-NOG mice

The pathogenesis of biliary atresia (BA), which leads to end-stage cirrhosis in most patients, has been thought to inflame and obstruct the intrahepatic and extrahepatic bile ducts. BA is not believed to be caused by abnormalities in parenchymal hepatocytes. However, there has been no report of a detailed analysis of hepatocytes buried in the cirrhotic livers of patients with BA. Therefore, we evaluated the proliferative potential of these hepatocytes in immunodeficient, liver-injured mice [the urokinase-type plasminogen activator (uPA) transgenic NOD/Shi-scid IL2rγnull (NOG); uPA-NOG strain]. We succeeded in isolating viable hepatocytes from the livers of patients with BA who had various degrees of fibrosis. The isolated hepatocytes were intrasplenically transplanted into the livers of uPA-NOG mice. The hepatocytes of only 3 of the 9 BA patients secreted detectable amounts of human albumin in sera when they were transplanted into mice. However, human leukocyte antigen-positive hepatocyte colonies were detected in 7 of the 9 mice with hepatocyte transplants from patients with BA. We demonstrated that hepatocytes buried in the cirrhotic livers of patients with BA retained their proliferative potential. A liver that was reconstituted with hepatocytes from patients with BA was shown to be a functioning human liver with a drug-metabolizing enzyme gene expression pattern that was representative of mature human liver and biliary function, as ascertained by fluorescent dye excretion into the bile canaliculi. These results imply that removing the primary etiology via an earlier portoenterostomy may increase the quantity of functionally intact hepatocytes remaining in a cirrhotic liver and may contribute to improved outcomes.

Rotavirus particles in the extrahepatic bile duct in experimental biliary atresia

BACKGROUND

Biliary atresia (BA) is the most common indication for liver transplantation in children. The experimental model of BA, induced by rotavirus infection in neonatal mice, has been widely used to investigate the inflammatory aspects of this disease. We investigated the kinetics and the localization of the viral infection in this murine model.

METHODS

In this study 399 animals were employed for a detailed investigation of rhesus rotavirus (RRV)-induced BA. RRV kinetics was analyzed by rtPCR and its (sub) cellular localization investigated using whole mounts which were further processed for confocal and electron microscopy.

RESULTS

The BA mouse model resulted in up to 100% induction of atresia following RRV injection. The kinetics of RRV infection differed between liver and extrahepatic bile ducts. While the virus peak up to day 10 postinfection was similar in both organs, the virus remained detectable in extrahepatic bile duct cells up to day 21. Interestingly, RRV particles were localized not only in cholangiocytes but also in cells of the subepithelial layers, potentially macrophages.

CONCLUSIONS

RRV remains present in the extrahepatic bile duct cells after an initial virus peak. Viral particles were detected in subepithelial cells in contrast to the described tropism toward cholangiocytes.

HMGB1-promoted and TLR2/4-dependent NK cell maturation and activation take part in rotavirus-induced murine biliary atresia

Recent studies show that NK cells play important roles in murine biliary atresia (BA), and a temporary immunological gap exists in this disease. In this study, we found high-mobility group box-1 (HMGB1) and TLRs were overexpressed in human and rotavirus-induced murine BA. The overexpressed HMGB1 released from the nuclei of rotavirus-infected cholangiocytes, as well as macrophages, activated hepatic NK cells via HMGB1-TLRs-MAPK signaling pathways. Immature NK cells had low cytotoxicity on rotavirus-injured cholangiocytes due to low expression of TLRs, which caused persistent rotavirus infection in bile ducts. HMGB1 up-regulated the levels of TLRs of NK cells and promoted NK cell activation in an age-dependent fashion. As NK cells gained increasing activation as mice aged, they gained increasing cytotoxicity on rotavirus-infected cholangiocytes, which finally caused BA. Adult NK cells eliminated rotavirus-infected cholangiocytes shortly after infection, which prevented persistent rotavirus infection in bile ducts. Moreover, adoptive transfer of mature NK cells prior to rotavirus infection decreased the incidence of BA in newborn mice. Thus, the dysfunction of newborn NK cells may, in part, participate in the immunological gap in the development of rotavirus induced murine BA.

Biliary atresia (BA) is the most common precipitating factor for liver transplantation in infants. BA is caused by the obstruction of hepatic bile ducts, leading to progressive obstructive jaundice and liver fibrosis. A well-recognized theory is that rotavirus injures biliary epithelia in a mouse model of BA, followed by attack of immunocytes, such as NK cells. We performed this research to investigate whether maturation and activation of NK cells take part in the development of BA. We identified that rotavirus induced HMGB1 release from injured bile ducts. HMGB1 induced NK cell activation in an age-dependent fashion via HMGB1-TLRs-MAPK signaling pathways. Newborn NK cells were unable to eliminate rotavirus-infected cholangiocytes, which caused persistent biliary infection; maturated NK cells were activated gradually and caused persistent biliary injury, which finally led to BA. We identify HMGB1 as an important pro-inflammatory initiator and a critical inducer for maturation of NK cells in the development of BA. HMGB1-induced activation of NK cells may, in part, plays crucial roles in the development of murine BA. Novel therapies targeting HMGB1 or TLRs in patients with BA may be applied in the future to decrease the activity of NK cells in order to inhibit the progression of BA.

A novel rat model simulating biliary atresia after a Kasai operation

PURPOSE

The mechanisms of liver fibrosis in biliary atresia (BA) after a Kasai operation deserve studying to improve the clinical outcomes. This study aimed to create a rat model simulating BA after a Kasai operation.

METHODS

We inserted a polyethylene tube (PE10) into the common hepatic duct (CHD) and ligated the common bile duct (CBD) in 30 newborn rats and injected 95% ethanol into IHD at postoperative week-one (POW-1). The PE10 was removed at POW-3. The rats were sacrificed at POW-5. The CBD cystojejunostomy was performed on another 10 rats at POW-5.

RESULTS

The IHD obliteration and CBD dilatation were noted at POW-3 cholangiography before removal of the PE tube. The gross findings at sacrifice in the rats without cystojejunostomy included biliary fibrosis, CBD cyst, and IHD obliteration. The microscopic findings of the liver were like BA. Seven of the 10 rats with CBD cystojejunostomy were jaundice-free at POW-8. The fibrosis grade at POW-8 of the rats with CBD cystojejunostomy was significantly lower in the jaundice-free rats (Ishak fibrosis score, 3.4 ± 0.9 and 1.5 ± 0.3 in the jaundiced rats and jaundice-free rats, respectively, p < .05).

CONCLUSION

Based on our study, CBD cystojejunostomy five weeks after CBD ligation with ethanol injection into the IHD in newborn rats can provide a model for investigating mechanisms and treatments of liver fibrosis in BA after a Kasai operation.

Systemic rotavirus infection

A new paradigm of rotavirus disease is emerging and rotavirus infection is no longer considered to be localized and confined to the GI tract. New evidence indicates that rotavirus infection is systemic. Viral antigen and infectious virus frequently enter the circulation in both children and animal model systems. Clinical case reports of systemic sequelae to rotavirus infection in children continue to accumulate, suggesting involvement in systemic disease syndromes. The use of animal models is providing biological and molecular evidence for infection at peripheral sites. Thus, infection at peripheral sites may account for reports of systemic sequelae to rotavirus infection. The importance of systemic sequelae and the ability of vaccination to prevent such sequelae remains to be determined.

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.

Different virulence of porcine and porcine-like bovine rotavirus strains with genetically nearly identical genomes in piglets and calves

Direct interspecies transmissions of group A rotaviruses (RVA) have been reported under natural conditions. However, the pathogenicity of RVA has never been directly compared in homologous and heterologous hosts. The bovine RVA/Cow-tc/KOR/K5/2004/G5P[7] strain, which was shown to possess a typical porcine-like genotype constellation similar to that of the G5P[7] prototype RVA/Pig-tc/USA/OSU/1977/G5P9[7] strain, was examined for its pathogenicity and compared with the porcine G5P[7] RVA/Pig-tc/KOR/K71/2006/G5P[7] strain possessing the same genotype constellation. The bovine K5 strain induced diarrhea and histopathological changes in the small intestine of piglets and calves, whereas the porcine K71 strain caused diarrhea and histopathological changes in the small intestine of piglets, but not in calves. Furthermore, the bovine K5 strain showed extra-intestinal tropisms in both piglets and calves, whereas the porcine K71 strain had extra-intestinal tropisms in piglets, but not in calves. Therefore, we performed comparative genomic analysis of the K71 and K5 RVA strains to determine whether specific mutations could be associated with these distinct clinical and pathological phenotypes. Full-length sequencing analyses for the 11 genomic segments for K71 and K5 revealed that these strains were genetically nearly identical to each other. Two nucleotide mutations were found in the 5′ untranslated region (UTR) of NSP5 and the 3′ UTR of NSP3, and eight amino acid mutations in VP1-VP4 and NSP2. Some of these mutations may be critical molecular determinants for RVA virulence and/or pathogenicity.

Aetiology of biliary atresia: what is actually known?

Biliary atresia (BA) is a rare disease of unknown etiology and unpredictable outcome, even when there has been timely diagnosis and exemplary surgery. It has been the commonest indication for liver transplantation during childhood for the past 20 years. Hence much clinical and basic research has been directed at elucidating the origin and pathology of BA. This review summarizes the current clinical variations of BA in humans, its occasional appearance in animals and its various manifestations in the laboratory as an experimental model.

Prevention of cholestasis in the murine rotavirus-induced biliary atresia model using passive immunization and nonreplicating virus-like particles

Biliary atresia (BA) is a neonatal cholangiopathy of unknown etiology that results in obliteration of bile ducts and is the primary indication for liver transplant in children. A murine model of BA, which involves infecting newborn mice with rhesus rotavirus (RRV) and leads to development of an obstructive cholangiopathy, has provided a model to assess measures to prevent and treat BA. We used this mouse model of RRV-induced BA to determine if passive immunization of pups using maternal immunization [injection of dams with non-replicating rotavirus (RV) virus-like particles (VLPs) or live RRV] or injection of pups with RV immune serum would protect these RRV-infected neonates from developing BA (measured using cholestasis). Parenteral immunization of mouse dams with two formulations of VLPs (containing viral proteins 2/6 or 2/6/7) resulted in a significant increase in serum RV antibody, and pups born to these immunized dams were protected from developing cholestasis following neonatal infection with RRV. Serum RV-specific antibody with titers of ≥400-800 in dams significantly protected pups from developing cholestasis, and a significant trend of increasing protection with high titers was observed (p<0.0001). Cholestatic pups had lower levels of RV serum antibody and higher serum (p<0.01) and liver (p<0.05) RV antigen compared to healthy pups. Passive transfer of low-titer (1600; p<0.05) or high-titer (25,600; p<0.01) RV immune serum to neonatal pups prior to RRV infection also protected them from developing cholestasis. Together, these findings indicate that passively acquired, neutralizing or non-neutralizing RV serum antibody attenuates viral replication and protects pups against disease in the RRV BA model. Early reduction of viral load by clearance with RV-specific antibody is likely a critical determinant of disease in this model.

Rotavirus replication in the cholangiocyte mediates the temporal dependence of murine biliary atresia

Biliary atresia (BA) is a neonatal disease that results in obliteration of the biliary tree. The murine model of BA, which mirrors the human disease, is based upon infection of newborn mice with rhesus rotavirus (RRV), leading to an obstructive cholangiopathy. The purpose of this study was to characterize the temporal relationship between viral infection and the induction of this model. BALB/c mice were infected with RRV on day of life (DOL) 0, 3, 5, and 7. Groups were characterized as early-infection (infection by DOL 3) or late-infection (infection after DOL 5). Early RRV infection induced symptoms in 95% of pups with a mortality rate of 80%. In contrast, late infection caused symptoms in only 50% of mice, and 100% of pups survived. The clinical findings correlated with histological analysis of extrahepatic biliary trees, cytokine expression, and viral titers. Primary murine cholangiocytes isolated, cultured, and infected with RRV yielded higher titers of infectious virus in those harvested from DOL 2 versus DOL 9 mice. Less interferon alpha and beta was produced in DOL 2 versus DOL 9 RRV infected primary cholangiocytes. Injection of BALB/c interferon alpha/beta receptor knockout (IFN-αβR(-/-)) pups at DOL 7 showed increased symptoms (79%) and mortality (46%) when compared to late infected wild type mice. In conclusion, the degree of injury sustained by relatively immature cholangiocytes due to more robust RRV replication correlated with more severe clinical manifestations of cholangiopathy and higher mortality. Interferon alpha production by cholangiocytes appears to play a regulatory role. These findings confirm a temporal dependence of RRV infection in murine BA and begin to define a pathophysiologic role of the maturing cholangiocyte.

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: the animal models

Biliary atresia (BA) is a progressive fibrosing process of the neonatal biliary tree and liver, of unknown origin, and an as-yet unexplained pathologic mechanism. The crucial point is to elucidate the origin of this rare disease to change palliative surgery to etiology-related procedures. Patient-based research can only begin at the time of the Kasai procedure and does not allow retracing of the pathology back to its origin. Basic research has focused on similar diseases in the veterinary literature and started to simulate BA in animal models. Unfortunately, even after 50 years of research, no knowledge has been gained from such models, which has led to a single clinical application. This article reviews BA in the context of the animal models available and discusses whether future studies are promising or futile.

Rotavirus and biliary atresia: can causation be proven?

PURPOSE OF REVIEW

New knowledge on rotavirus infection in children and well established mouse models has renewed interest in whether rotavirus could cause biliary atresia, an idiopathic, obliterative infantile disease of bile ducts that is the primary indication for liver transplant in children.

RECENT FINDINGS

Studies in the rotavirus mouse model of biliary atresia indicate that infection of biliary epithelium is an inaugural event leading to biliary inflammation and obstruction, which is preceded by systemic spread of rotavirus, which also occurs during human rotavirus enteric infections. Viral factors, including rotavirus gene 4, are important for biliary infection and biliary atresia in mice. Specific host factors related to inflammatory processes (natural killer and T cells, interferon) are also critical, and a paucity of regulatory T cells in neonates may play a key role in pathogenesis in experimental biliary atresia. Rotavirus vaccination has substantially decreased rotavirus diarrheal disease worldwide and might enable demonstration of a cause-effect relationship between rotavirus infection and biliary atresia in humans.

SUMMARY

Rotavirus can be detected in the serum of mice and children and causes biliary atresia in neonatal mice. Approaches to re-examine whether rotavirus causes biliary atresia in children are discussed based on concepts from the mouse model of biliary atresia and rotavirus vaccination programs.

Osteopontin upregulation in rotavirus-induced murine biliary atresia requires replicating virus but is not necessary for development of biliary atresia

Biliary atresia (BA) is a progressive fibro-inflammatory pediatric liver disease in which osteopontin (OPN), a glycoprotein with inflammatory and fibrogenic activity, may play a pathogenic role. The current studies were conducted in a mouse model of rotavirus-induced BA to test the hypotheses that live but not inactivated rotavirus causes antigenemia, upregulation of hepatic OPN expression, and induction of BA and fibrosis; and that OPN is necessary for development of BA. Prolonged or transient antigenemia developed in mice inoculated with live or inactivated virus, respectively, but only live virus upregulated hepatic OPN and caused BA and fibrosis. OPN was expressed in intra- and extrahepatic bile ducts in healthy mice and in mice with BA. OPN-deficient mice, similar to WT mice, developed BA. Together, these data show that live but not inactivated rotavirus causes upregulation of hepatic OPN expression and BA but that OPN is not necessary for development of BA.

α-enolase autoantibodies cross-reactive to viral proteins in a mouse model of biliary atresia

BACKGROUND & AIMS

Biliary atresia (BA) is a neonatal cholangiopathy of unknown etiology. The bile duct injury that occurs in patients with BA might result from a hepatobiliary viral infection followed by an autoimmune response against the bile duct epithelia. We aimed to identify autoantigens recognized by serum antibodies in the Rhesus rotavirus (RRV)-induced mouse model of BA; findings were correlated with BA in humans.

METHODS

Bile duct epithelial proteins were screened for their reactivity with serum antibodies from the mouse model of BA using immunoblot assays. Unique proteins that reacted with sera antibodies were identified by mass spectrometry and verified using enzyme-linked immunosorbent assay (ELISA) and immunoblot analyses. Candidate autoantibodies in BA patient sera were analyzed by ELISA.

RESULTS

A bile duct epithelial antigen that reacted strongly with serum immunoglobulin (Ig) G from the mouse model of BA was identified as α-enolase. α-Enolase autoantibody specificity was confirmed by ELISA and immunoblot analyses. Anti-RRV and anti-enolase antibodies cross-reacted with enolase and RRV proteins; we identified regions of sequence homology between RRV and enolase. Serum samples from patients with BA had increased levels of anti-enolase IgM and IgG.

CONCLUSIONS

We have identified autoantibodies against α-enolase in a mouse model of BA (infected with RRV) and in serum samples from patients, indicating a role of humoral autoimmunity in disease pathogenesis. The cross-reactivity between an anti-enolase antibody and RRV proteins indicates that molecular mimicry might activate humoral autoimmunity in BA patients; further studies are required.

Molecular mechanisms of bile duct development

The mammalian biliary system, consisting of the intrahepatic and extrahepatic bile ducts, is responsible for transporting bile from the liver to the intestine. Bile duct dysfunction, as is seen in some congenital biliary diseases such as Alagille syndrome and biliary atresia, can lead to the accumulation of bile in the liver, preventing the excretion of detoxification products and ultimately leading to liver damage. Bile duct formation requires coordinated cell-cell interactions, resulting in the regulation of cell differentiation and morphogenesis. Multiple signaling molecules and transcription factors have been identified as important regulators of bile duct development. This review summarizes recent progress in the field. Insights gained from studies of the molecular mechanisms of bile duct development have the potential to reveal novel mechanisms of differentiation and morphogenesis in addition to potential targets for therapy of bile duct disorders.

Susceptibility to experimental biliary atresia linked to different hepatic gene expression profiles in two mouse strains

AIM

To compare hepatic gene expression during the development of experimental biliary atresia (BA) in two different mouse strains.

METHODS

Balb/c mice and C57Black/6 (Black/6) mice were infected with rhesus rotavirus (RRV) postpartum, clinical signs of BA and survival were noted. Liver sections were assessed for cluster of differentiation antigen (CD) 3, CD4 and CD8 expression, and the hepatic virus load was determined. Second, mice of both strains were sacrificed three days after infection. Isolated hepatic RNA was subjected to gene expression analysis using Affymetrix Gene Chip MOE 430 2.0.

RESULTS

The incidence of BA was significantly lower in Black/6 mice compared to Balb/c mice (13.5% vs. 67%, P < 0.05). The mean virus titers were higher in mice with BA compared to mice without BA. Different gene profiles three days after virus infection were noted, with differential expression of 201 genes, including those regulating apoptosis, nucleic acid binding, transport function and particularly the immune response (chemokine C-C motif ligand 2, toll-like receptor 3, CD antigen 14, chemokine (C-X-C motif) ligands 10 and 11). This correlated with a significant increase of CD4 positive cells only in Balb/c mice with BA compared to healthy mice (13.5 vs. 5.0; P < 0.05). Black/6 mice did not exhibit any significant increase of CD3 or CD4 leukocytes despite cholestasis.

CONCLUSION

The different susceptibility to experimental BA was associated with an increase of CD4 T-cells in the liver of Balb/c mice, which is linked to different gene profiles at the onset of bile duct obstruction.

Biliary atresia: a new immunological insight into etiopathogenesis

Biliary atresia is an idiopathic neonatal cholestatic disease characterized by the destruction of both the intra- and extra-hepatic biliary ducts. There are two clinical manifestations of the disease: an embryonal subtype, which often presents at birth and is associated with congenital malformations, and a 'perinatal' subtype, which is probably an acquired disease due to unknown etiology. Over the last two decades, researchers have focused on activation of the cell-mediated immunity as the mechanism for biliary epithelial cell destruction for the latter subtype. A proposed trigger of this immune response is an initial viral infection, inducing biliary epithelial cells to become antigen-presenting cells and thus instigating immune-mediated destruction of the biliary tract. However, putative viruses have never been confirmed. More recently, a novel hypothesis - that maternal microchimerism may initiate a host immunologic response towards the bile duct epithelia - has been proposed. This paper discusses the etiology of biliary atresia in the context of the current research.

Differential expression of hepatic fibrosis mediators in sick and spontaneously recovered mice with experimental biliary atresia

BACKGROUND

Hepatic fibrosis leading to cirrhosis is the major morbidity in patients with biliary atresia (BA). This fibrosis is due to an imbalance in extracellular matrix (ECM) breakdown and deposition. We have previously demonstrated increased mRNA expression for inhibitors of ECM breakdown without increased expression for mediators of ECM deposition in our animal model of BA by d 14. However, only a mild degree of hepatic fibrosis was seen at this time. We hypothesized that expression patterns for these proteins may change once more significant fibrosis had been established, and added resuscitation to the model to improve survival. Interestingly, we found that some mice spontaneously recovered at later time points with resuscitation, and thus compared expression for inhibitors of ECM breakdown and deposition in sick and recovered mice to determine the differences.

METHODS

Newborn Balb/c mice received an intraperitoneal injection 1.0 x 10(6) fluorescence forming units of rhesus rotavirus 24h after birth. Mice were monitored daily for weight gain, development of jaundice, acholic stools, and bilirubinuria. Fifty muL/g of 5% dextrose in normal saline were subcutaneously injected daily to each mouse starting on d 7 until sacrifice. Mice that survived past d 14 were sacrificed at d 21 after saline or RRV infection. Livers were then harvested post-injection d 21 for histologic and immunohistochemical analysis. RNA expression of known mediators of fibrosis was evaluated using quantitative real-time PCR. Protein expression was assessed using ELISA. Weights and normally distributed data were compared using Student's t test. Histologic findings were compared using Fisher's exact test. Comparisons of gene expression and skewed data were performed by the Mann-Whitney U test. Statistical significance was assigned to any P value less than 0.05.

RESULTS

Daily resuscitation resulted in a 35% (24/68) survival rate to d 21 in our model. Mice that recovered were significantly heavier than those that remained ill on d 14 (6.15 +/- 1.16 versus 4.94 +/- 0.82, P = 0.02) and 21 (7.31 +/- 1.41 versus 4.14 +/- 0.53, P < 0.001) despite the fact that there was no difference between the groups with respect to weight on d 7 (4.29 +/- 0.90 versus 3.89 +/- 0.81, P = 0.32). We found that all (10/10) animals that displayed clinical signs of biliary atresia on d 21 had moderate or severe histologic findings, while only one (1/9) of the recovered animals had liver abnormalities at sacrifice (P < 0.001 versus sick group). We also found that the sick mice had statistically significant median fold-increases of mRNA expression for TIMP-1 (31.9 versus 9.1, P = 0.041), TIMP-4 (88.1 versus 1.8, P = 0.022), and MMP-7 (51.8 versus 11.9, P = 0.006) compared with those that recovered. There was a trend toward decreased mRNA expression for PAI-1, which did not reach statistical significance (median 27.7 versus 2.19, P = 0.066). Increased protein expression for TIMP-1 and PAI-1 were also found in the sick group. The mRNA expression for the fibrillar collagens, fibronectin-1, connective tissue growth factor, snail-1, TIMP-2 and -3, and MMP-2 and MMP-9 was not different in the sick and recovered groups 21 d after RRV infection, and was not elevated from baseline gene expression.

CONCLUSIONS

With resuscitation added to the animal model of BA, some mice spontaneously recover while others progress to more significant hepatic fibrosis. Mice with hepatic fibrosis have a continued increase in mRNA expression of TIMP-1, TIMP-4, and MMP-7, with a trend toward increased mRNA expression of PAI-1 on d 21. Protein levels for TIMP-1 and PAI-1 were also increased in the sick mice. Recovered mice display mild to no hepatic parenchymal disease and a normal pattern of mRNA expression for the mediators of fibrosis tested. No increase in mRNA expression for the mediators of ECM deposition was found in either group. These data further support the notion that inhibition of ECM breakdown alone is sufficient to induce hepatic fibrosis. Modulation of this process may be a putative target for preventing liver injury in patients with BA.

Biliary atresia

Biliary atresia (BA) is a condition unique to infancy. It results from inflammatory destruction of the intrahepatic and extrahepatic bile ducts. It is the most frequent surgically correctable liver disorder in infancy and the most frequent indication for liver transplantation in paediatric age. Clinical presentation is in the first few weeks of life with conjugated hyperbilirubinaemia (dark urine and pale stools); other manifestations of liver disease, such as failure to thrive, splenomegaly and ascites, appear only later, when surgery is unlikely to be successful. Hence, all infants with conjugated hyperbilirubinaemia must be urgently referred to specialised centres for appropriate treatment. Success of surgery depends on the age at which it is performed. With corrective surgery, followed, when necessary, by liver transplantation, the overall survival rate is approximately 90%. The cause of BA is unknown, but there is evidence for the involvement of infectious, genetic and immunologic mechanisms, which will be discussed in this review.

Recent advances in biliary atresia: prospects for novel therapies

BACKGROUND

Biliary atresia (BA) is a progressive fibro-obliterative disease of the extrahepatic biliary tree that presents with biliary obstruction before 2 months of age. Untreated BA is a uniformly fatal disease and even with our current therapies only 50% of children with BA will be transplant-free by 2 years of age. Despite descriptions of this disorder dating back to the 1800s our current therapies are palliative. They focus on prompt diagnosis, supportive nutritional care and interventions for sequelae.

OBJECTIVE

To present the literature supporting current treatment strategies and potential future therapies.

METHOD

Each of the aspects of care is described and the literature about nuances of care is provided.

CONCLUSION

Therapies will not improve outcomes until novel treatments are introduced, such as those suggested, which may intervene in the inflammatory or fibrotic steps of the disease process.

Role of interferon in homologous and heterologous rotavirus infection in the intestines and extraintestinal organs of suckling mice

Recent studies demonstrated that viremia and extraintestinal rotavirus infection are common in acutely infected humans and animals, while systemic diseases appear to be rare. Intraperitoneal infection of newborn mice with rhesus rotavirus (RRV) results in biliary atresia (BA), and this condition is influenced by the host interferon response. We studied orally inoculated 5-day-old suckling mice that were deficient in interferon (IFN) signaling to evaluate the role of interferon on the outcome of local and systemic infection after enteric inoculation. We found that systemic replication of RRV, but not murine rotavirus strain EC, was greatly enhanced in IFN-alpha/beta and IFN-gamma receptor double-knockout (KO) or STAT1 KO mice but not in mice deficient in B- or T-cell immunity. The enhanced replication of RRV was associated with a lethal hepatitis, pancreatitis, and BA, while no systemic disease was observed in strain EC-infected interferon-deficient mice. In IFN-alpha/beta receptor KO mice the extraintestinal infection and systemic disease were only moderately increased, while RRV infection was not augmented and systemic disease was not present in IFN-gamma receptor KO mice. The increase of systemic infection in IFN-deficient mice was also observed during simian strain SA11 infection but not following bovine NCDV, porcine OSU, or murine strain EW infection. Our data indicate that the requirements for the interferon system to inhibit intestinal and extraintestinal viral replication in suckling mice vary among different heterologous and homologous rotavirus strains, and this variation is associated with lethal systemic disease.

Biliary atresia: recent progress

Extrahepatic biliary atresia (EHBA), an inflammatory sclerosing cholangiopathy, is the leading indication for liver transplantation in children. The cause is still unknown, although possible infectious, genetic, and immunologic etiologies have received much recent focus. These theories are often dependent on each other for secondary or coexisting mechanisms. Concern for EHBA is raised by a cholestatic infant, but the differential diagnosis is large and the path to diagnosis remains varied. Current treatment is surgical with an overall survival rate of approximately 90%. The goals of this article are to review the important clinical aspects of EHBA and to highlight some of the more recent scientific and clinical developments contributing to our understanding of this condition.

Cholangiocyte expression of alpha2beta1-integrin confers susceptibility to rotavirus-induced experimental biliary atresia

Inoculation of BALB/c mice with rhesus rotavirus (RRV) in the newborn period results in biliary epithelial cell (cholangiocyte) infection and the murine model of biliary atresia. Rotavirus infection of a cell requires attachment, which is governed in part by cell-surface expression of integrins such as alpha2beta1. We hypothesized that cholangiocytes were susceptible to RRV infection because they express alpha2beta1. RRV attachment and replication was measured in cell lines derived from cholangiocytes and hepatocytes. Flow cytometry was performed on these cell lines to determine whether alpha2beta1 was present. Cholangiocytes were blocked with natural ligands, a monoclonal antibody, or small interfering RNA against the alpha2-subunit and were infected with RRV. The extrahepatic biliary tract of newborn mice was screened for the expression of the alpha2beta1-integrin. Newborn mice were pretreated with a monoclonal antibody against the alpha2-subunit and were inoculated with RRV. RRV attached and replicated significantly better in cholangiocytes than in hepatocytes. Cholangiocytes, but not hepatocytes, expressed alpha2beta1 in vitro and in vivo. Blocking assays led to a significant reduction in attachment and yield of virus in RRV-infected cholangiocytes. Pretreatment of newborn pups with an anti-alpha2 monoclonal antibody reduced the ability of RRV to cause biliary atresia in mice. Cell-surface expression of the alpha2beta1-integrin plays a role in the mechanism that confers cholangiocyte susceptibility to RRV infection.

Integrin alphavbeta6 and mediators of extracellular matrix deposition are up-regulated in experimental biliary atresia

INTRODUCTION

Biliary atresia (BA) is a progressive obliteration of the extrahepatic bile ducts resulting in hepatic fibrosis. The underlying mechanisms have not been defined. We used an animal model of BA to evaluate mediators of extracellular matrix (ECM) processing to determine which factors may be involved.

METHODS

Newborn BALB/c mice received an intraperitoneal injection with rhesus rotavirus or saline within 24 h of birth. Livers were harvested on days 7 and 14 for histology and immunohistochemistry (IHC). RNA expression was determined using quantitative real-time PCR. Human liver from patients with BA and those having a resection for nonfibrosing diseases was also evaluated.

RESULTS

In experimental mice, mRNA expression for tissue inhibitor of metalloproteinase (TIMP)-1 and matrix metalloproteinase (MMP)-7 was increased 18-fold and 69-fold, respectively on day 7, with further increases on day 14. On day 14, mRNA expression for plasminogen activator inhibitor (PAI)-1 (38-fold), TIMP-4 (9.5-fold), and MMP-9 (5.5-fold) mRNA was also observed. Furthermore, integrin alpha(v) beta(6) mRNA expression was increased on days 7 (11-fold) and 14 (6-fold). Presence of integrin alpha(v) beta(6) protein was confirmed by IHC in both mouse and human specimens in the proliferating biliary epithelium.

CONCLUSIONS

Our data suggest experimental BA is associated with increased mRNA expression of ECM degradation inhibitors, TIMP-1, PAI-1, and TIMP-4. MMP-7 and MMP-9 expression is also elevated in this model. Furthermore, increased gene expression of integrin alpha(v)beta(6) was demonstrated and IHC confirmed protein expression. Integrin alpha(v)beta(6) or the inhibitors of ECM breakdown may be attractive targets for future treatment strategies.

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.

Biliary atresia: interdisciplinary initiatives focus on a rare disease

During the last decade, biliary atresia (BA) has attained more interest and the frequency of BA-related publications has increased continuously. Pediatric hepatologists and pediatric surgeons are very active in improving diagnosis and treatment modalities of BA patients, in order to prolong the survival rate of their native liver. Together with transplant surgeons, the bridging of BA patients to liver transplantation (LTx) becomes optimized and as a consequence of this interdisciplinary approach, the overall survival of babies with BA has already reached 90%. Furthermore, basic research into the still unknown origin of BA has advanced, and numerous scientific programs have already linked together. The overriding interest is to discover at least BA's etiology and to turn the treatment of BA patients from a symptomatic to a causative approach. Interdisciplinary and international programs are mandatory and already existing initiatives in Europe, the United States and Japan are going to coordinate their registries, clinical trials and basic research studies for the benefit of the patients and solve the riddle of BA.

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.