What Is Hot and New in Basic and Translational Science in Liver Transplantation in 2023? Report of the Basic and Translational Research Committee of the International Liver Transplantation Society.

The 2023 Joint Annual Congress of the International Liver Transplantation Society, European Liver and Intestine Transplant Association, and Liver Intensive Care Group of Europe were held in Rotterdam, the Netherlands, from May 3 to 6, 2023. This year, all speakers were invited to attend the Congress in person for the first time since the COVID-19 pandemic. The congress was attended by 1159 registered delegates from 54 countries representing 5 continents, with the 10 countries comprising the bulk of the delegates. Of the 647 abstracts initially submitted, 542 were eventually presented at the meeting, coming from 38 countries (mainly North America, Europe, and Asia) and 85% of them (462 abstracts) came from only 10 countries. Fifty-three (9.8%) abstracts, originated from 17 countries, were submitted under the Basic/Translational Scientific Research category, a similar percentage as in 2022. Abstracts presented at the meeting were classified as (1) ischemia and reperfusion injury, (2) machine perfusion, (3) bioengineering and liver regeneration, (4) transplant oncology, (5) novel biomarkers in liver transplantation, (6) liver immunology (rejection and tolerance), and (7) artificial intelligence and machine learning. Finally, we evaluated the number of abstracts commented in the Basic and Translational Research Committee-International Liver Transplantation Society annual reports over the past 5 y that resulted in publications in peer-reviewed journals to measure their scientific impact in the field of liver transplantation.

Piezoelectric Multi-Channel Bilayer Transducer for Sensing and Filtering Ossicular Vibration.

This paper presents an acoustic transducer for fully implantable cochlear implants (FICIs), which can be implanted on the hearing chain to detect and filter the ambient sound in eight frequency bands between 250 and 6000 Hz. The transducer dimensions are conventional surgery compatible. The structure is formed with 3  × 3 × 0.36 mm active space for each layer and 5.2 mg total active mass excluding packaging. Characterization of the transducer is carried on an artificial membrane whose vibration characteristic is similar to the umbo vibration. On the artificial membrane, piezoelectric transducer generates up to 320.3 mVpp under 100 dB sound pressure level (SPL) excitation and covers the audible acoustic frequency. The measured signal-to-noise-ratio (SNR) of the channels is up to 84.2 dB. Sound quality of the transducer for fully implantable cochlear implant application is graded with an objective qualification method (PESQ) for the first time in the literature to the best of the knowledge, and scored 3.42/4.5.

Telemedicine in monitoring pediatric LT patients before and during COVID-19 pandemic.

BACKGROUND: The delivery of healthcare services by telemedicine decreases costs of traveling for patients, is less time-consuming, and most importantly permits the connection between highly skilled specialists and patients. However, whether the use of telemedicine (text messaging) for LT patients was affected by the COVID-19 pandemic is unknown. METHODS: We collected data (following consent from patients and parents) from 57 patients (33 male/24 female) with a median age of 47 (IQR: 9-91) months, whom we followed up with text messaging between September 2019 and September 2020, spanning the 6 months prior to COVID-19 and during this period. RESULTS: In total, 723 text message mediated consultations occurred during this period, henceforth simply referred to as "messages." Three hundred and twenty-eight (45%) messages occurred during the 6 months up to the start of the pandemic. Following the COVID-19 outbreak, the number of messages increased to 395 (55%). The three most common reasons of messaging were post-liver-LT follow-up messages (n = 215/723, 29.7%), consultations for drug use (n = 157/723, 21.7%), and medication prescriptions (n = 113/723, 15.6%). Protocol biopsy discussions (n = 33/723, 4.6%) and fever (n = 27/723, 3.7%) were among others (vaccination, rash, diarrhea, cough, fatigue, acne). During the COVID-19 outbreak, only post-LT follow-up messages increased significantly to 132/395 (33%) from 83/328 (25%) (p-value: .02). CONCLUSIONS: We found that the pandemic resulted in an increase in the total number of text message mediated consultations and specifically for the use of post-LT follow-up. Messaging was effective for post-LT follow-ups and all patients were at least satisfied.

Examining the Hepatic Immune System in Children With Liver Disease With Fine Needle Aspiration.

OBJECTIVES: Liver biopsy is the standard in diagnosing liver diseases. Yet, it provides little space to perform comprehensive immune profiling of the liver. Hence, we explored whether fine needle aspirates (FNAs) could be used to elucidate the hepatic immunity in children. METHODS: We enrolled 74 children undergoing diagnostic (n = 17) or protocol biopsy (n = 57) following liver transplantation (LT). Matched blood and FNAs were obtained. Additionally, explant liver tissue was collected from children (n = 14) undergoing LT. Immune cells were isolated from peripheral blood, FNAs and explanted livers. Immune-phenotypical profiling was done by flow cytometry. RESULTS: Biopsied patients (58% female) were at a median age of 46 months (interquartile range [IQR]: 12-118) and LT patients (71% female) were 48 months (IQR: 21-134, P = 0.78) old. CD69+, a hallmark of tissue-resident immune cells was expressed in 1.3% of CD3+ T cells from blood being higher in FNA (20%) and tissue (49%, P < 0.001). CD4+ T-cell frequencies in tissue (13%) and FNAs (20%) were lower compared to blood (35%, P < 0.001) whereas CD8+ T cells in tissue (33.5%) and FNA (32%) were higher than in blood (25%, P < 0.01). Mucosal associated invariant T cells were enriched in liver tissue (8.8%) and in the FNA (4.4%) compared to blood (1.7%, P < 0.001). Whereas the percentage of total Tregs (CD4+CD25+FOXP3+CD127low/-) decreased, the proportion of activated Tregs (CD4+CD45RA-FOXP3high) increased in FNA and explant. Breg (CD19+CD20+CD24highCD38high) frequencies were similar in all groups. CONCLUSION: FNA is a practical method to sample the liver immune system collecting even small cell subsets such as regulatory T/B cells.

Standard immunosuppressive treatment reduces regulatory B cells in children with autoimmune liver disease.

Introduction: Autoimmune hepatitis (AIH) is a chronic liver disease caused by a perturbed immune system. The scarcity of short- and long-term immune monitoring of AIH hampered us to comprehend the interaction between immunosuppressive medication and immune homeostasis. Methods and patients: We recruited children with AIH at the time of diagnosis and at the 1st, 3rd, 6th, 12th, 18th, and 24th months of immunosuppression (IS). We also enrolled children with AIH being on IS for >2 years. Children with drug-induced liver injury (DILI), and those receiving tacrolimus after liver transplantation (LT), were enrolled as disease/IS control subjects. Healthy children (HC) were also recruited. Peripheral blood mononuclear cells (PBMCs) were isolated from all participants. Healthy liver tissue from adult donors and from livers without inflammation were obtained from children with hepatoblastoma. By using flow cytometry, we performed multi-parametric immune profiling of PBMCs and intrahepatic lymphocytes. Additionally, after IS with prednisolone, tacrolimus, rapamycin, or 6-mercaptopurine, we carried out an in vitro cytokine stimulation assay. Finally, a Lifecodes SSO typing kit was used to type HLA-DRB1 and Luminex was used to analyze the results. Results: Untreated AIH patients had lower total CD8 T-cell frequencies than HC, but these cells were more naïve. While the percentage of naïve regulatory T cells (Tregs) (CD4+FOXP3lowCD45RA+) and regulatory B cells (Bregs, CD20+CD24+CD38+) was similar, AIH patients had fewer activated Tregs (CD4+FOXP3highCD45RA - ) compared to HC. Mucosal-associated-invariant-T-cells (MAIT) were also lower in these patients. Following the initiation of IS, the immune profiles demonstrated fluctuations. Bregs frequency decreased substantially at 1 month and did not recover anymore. Additionally, the frequency of intrahepatic Bregs in treated AIH patients was lower, compared to control livers, DILI, and LT patients. Following in vitro IS drugs incubation, only the frequency of IL-10-producing total B-cells increased with tacrolimus and 6MP. Lastly, 70% of AIH patients possessed HLA-DR11, whereas HLA-DR03/DR07/DR13 was present in only some patients. Conclusion: HLA-DR11 was prominent in our AIH cohort. Activated Tregs and MAIT cell frequencies were lower before IS. Importantly, we discovered a previously unrecognized and long-lasting Bregs scarcity in AIH patients after IS. Tacrolimus and 6MP increased IL-10+ B-cells in vitro.

Course of vitamin D levels before and after liver transplantation in pediatric patients.

BACKGROUND: 25-hydroxy VD insufficiency is known in children undergoing LT but the serial post-transplant VD course and supplementation modalities in the peri-transplant period are lacking. We aimed to determine the pre-VD status and the post-transplant VD status course following VD supplementation and to elucidate its relationship with post-transplant outcome parameters such as infection and survival. METHODS: Pre- and post-VD levels were monitored in parallel with interventions to adjust VD levels in LT patients. VD status was categorized as circulating levels <30-21 ng/ml (insufficiency), 20-10 ng/ml (deficiency), and <10 ng/ml (severe deficiency). Patients received stoss (300000IU) VD3 within the pretransplant period if serum levels were <20 ng/ml. RESULTS: 135 transplanted children were included. The age at LT was 22 months (IQR: 8-60). The pretransplant median VD level was 14 ng/ml. Despite stoss dose, post-transplant median VD level was 1.8 ng/ml (day one), 4 ng/ml (week one), 19 ng/ml (month one), 33 ng/ml (month three), 38 ng/ml (months 6-12), and 40 ng/ml (month 24). After 6 months, VD status reached >30 ng/ml in 98% of patients. Only at pre-LT, higher infection rate (18.7%) in the severe VD deficiency group was observed compared to the VD deficiency group (2.9%, p = .04). Survival was not affected by serum VD levels. CONCLUSION: VD levels fell substantially after LT but are rectifiable by stoss dose, which was well tolerated. Only the infection rate was associated with the VD status.

A single-center report of COVID-19 disease course and management in liver transplanted pediatric patients.

BACKGROUND: In 2019, SARS-CoV-2 causing COVID-19 emerged. Severe COVID-19 symptoms may evolve by virtue of hyperactivation of the immune system. Equally, immunocompromised patients may be at increased risk to develop COVID-19. However, treatment guidelines for children following liver transplantation are elusive. METHODS: As a liver transplantation center, we diagnosed and followed up 10 children (male/female: 8/2) with a median age of 8.5 years (IQR: 5.2-11.0), with COVID-19 post-liver transplant between March 2019 and December 2020. COVID-19 diagnosis was based on PCR test and or florid X-ray findings compatible with COVID-19 in the absence of other cause. We retrospectively collected clinical and laboratory data from electronic patient records following written consent from patients/parents. RESULTS: Nine patients were diagnosed as definitive (PCR positive) with one patient being diagnosed as probable COVID-19. Seven patients recovered without any support whereas three were admitted for non-invasive oxygenation. Lymphopenia and/or high levels of serum IL-6 were detected in four patients. Six patients mounted anti-SARS-CoV-2 antibodies at median 30 days (IQR: 26.5-119.0) following COVID-19 diagnosis. Antibiotic therapy, favipiravir, anakinra, and IVIG were used as treatment in 4,1,1 and 2 patients, respectively. Furthermore, we kept the tacrolimus with or without everolimus but stopped MMF in 2 patients. Importantly, liver allograft function was retained in all patients. CONCLUSIONS: We found that being immunocompromised did not affect disease severity nor survival. Stopping MMF yet continuing with tacrolimus was an apt treatment modality in these patients.

Human Leukocyte Antigen Profile Predicts Severity of Autoimmune Liver Disease in Children of European Ancestry.

BACKGROUND AND AIMS: Genetic predisposition to autoimmune hepatitis (AIH) in adults is associated with possession of human leukocyte antigen (HLA) class I (A*01, B*08) and class II (DRB1*03, -04, -07, or -13) alleles, depending on geographic region. Juvenile autoimmune liver disease (AILD) comprises AIH-1, AIH-2, and autoimmune sclerosing cholangitis (ASC), which are phenotypically different from their adult counterparts. We aimed to define the relationship between HLA profile and disease course, severity, and outcome in juvenile AILD. APPROACH AND RESULTS: We studied 236 children of European ancestry (152 female [64%], median age 11.15 years, range 0.8-17), including 100 with AIH-1, 59 with AIH-2, and 77 with ASC. The follow-up period was from 1977 to June 2019 (median 14.5 years). Class I and II HLA genotyping was performed using PCR/sequence-specific primers. HLA B*08, -DRB1*03, and the A1-B8-DR3 haplotype impart predisposition to all three forms of AILD. Homozygosity for DRB1*03 represented the strongest risk factor (8.8). HLA DRB1*04, which independently confers susceptibility to AIH in adults, was infrequent in AIH-1 and ASC, suggesting protection; and DRB1*15 (DR15) was protective against all forms of AILD. Distinct HLA class II alleles predispose to the different subgroups of juvenile AILD: DRB1*03 to AIH-1, DRB1*13 to ASC, and DRB1*07 to AIH-2. Possession of homozygous DRB1*03 or of DRB1*13 is associated with fibrosis at disease onset, and possession of these two genes in addition to DRB1*07 is associated with a more severe disease in all three subgroups. CONCLUSIONS: Unique HLA profiles are seen in each subgroup of juvenile AILD. HLA genotype might be useful in predicting responsiveness to immunosuppressive treatment and course.

A novel insight into the pathophysiology of autoimmune hepatitis: An immune activator mutation in the FLT3 receptor.

Autoimmune hepatitis (AIH) is a chronic progressive autoimmune liver disease characterized by hypergammaglobulinemia, interface hepatitis, a female preponderance, and the presence of autoantibodies in most patients. The presence of HLA-DR3/DR4 and functional impairment in regulatory T cells are associated with AIH. However, AIH is a multifactorial complex disease. This report is a description of a case of seronegative AIH in a girl with chronic hepatitis, a high immunoglobulin E (IgE) level, perforating nodular dermatitis, and sheer eosinophilia. To re-evaluate the diagnosis, whole exon sequencing was performed. It was determined that the patient had ancestral haplotype A1-B8-DR3, which is associated with autoimmunity. Importantly, it was also noted that an undocumented point mutation (Ala627Thr) of the FMS-like tyrosine 3 kinase (FLT3) receptor was present. This FLT3 receptor gain-of-function mutation is associated with the activation of the mechanistic target of rapamycin (mTOR), and dendritic cell activation. In addition, a loss-of-function mutation in the melanocortin-3 receptor gene, which inhibits interleukin 4, was detected. The constellation of these immune deregulatory factors may have propagated auto-aggression of the liver, causing chronic hepatitis with AIH features. The findings of seronegativity with eosinophilia and a high IgE level led us to hypothesize that the pathognomonic mechanism in this case was unlike that of classic AIH pathophysiology. Since mTOR is constitutively activated, mTOR inhibitors may be a useful option to treat AIH and dermatitis.

Immune monitoring of a child with autoimmune hepatitis and type 1 diabetes during COVID-19 infection.

Immunocompromised patients may be at increased risk to develop COVID-19 during the 2019 ß-coronavirus infection. We present the unique opportunity we had to monitor the liver, IL-6 and immune cell course before, during and after COVID-19 in a boy with autoimmune hepatitis (AIH) and type 1 diabetes (T1D). CD4 and CD8 T cells frequencies decreased because of prednisolone, followed by a plateauing increase whereas CD19CD20 B cell increased strongly and was unaffected by COVID-19 infection. Moreover, the percentage of activated CD8 T cells expressing HLA-DR (CD8HLA-DR) increased during COVID-19 and subsided after its clearance. Total regulatory T cells (Tregs: CD4CD25CD127FOXP3) remained stable. Although activated Tregs (CD4CD45RAFOXP3) strongly increased upon prednisolone, it decreased afterwards. Furthermore, regulatory B cells (Bregs: CD19CD20CD24CD38) declined sharply owing to prednisolone. Serum IL-6 remained undetectable at all times. We demonstrated for the first time immune monitoring in a child with AIH and T1D before, during and after COVID-19. We hypothesize that continuing with low level of prednisolone without azathioprine may have abrogated activated Tregs, Bregs and IL-6 production and therefore permitting the activation of CD8 T cells, clearing the virus.

Normothermic Machine Perfusion (NMP) Inhibits Proinflammatory Responses in the Liver and Promotes Regeneration.

Liver transplantation (LT) is a successful treatment for patients with liver failure. However, organ shortage results in over 11% of patients losing their chance of a transplant attributed to liver decompensation (LD) and death. Ischemia/reperfusion injury (IRI) following conventional cold storage (CS) is a major cause of injury leading to graft loss after LT. Normothermic machine perfusion (NMP), a method of organ preservation, provides oxygen and nutrition during preservation and allows aerobic metabolism. NMP has recently been shown to enable improved organ utilization and posttransplant outcomes following a phase I and a phase III randomized trial. The aim of the present study is to assess the impact of NMP on reducing IRI and to define the underlying mechanisms. We transplanted and compared 12 NMP with 27 CS-preserved livers by performing gene microarray, immunoprofiling of hepatic lymphocytes, and immunochemistry staining of liver tissues for assessing necrosis, platelet deposition, and neutrophil infiltration, and the status of steatosis after NMP or CS prereperfusion and postreperfusion. Recipients receiving NMP grafts showed significantly lower peak aspartate aminotransferase (AST) levels than those receiving CS grafts. NMP altered gene-expression profiles of liver tissue from proinflammation to prohealing and regeneration. NMP also reduced the number of interferon gamma (IFN-γ) and interleukin (IL)-17-producing T cells and enlarged the CD4pos CD25high CD127neg FOXP3pos regulatory T cell (Treg) pool. NMP liver tissues showed less necrosis and apoptosis in the parenchyma and fewer neutrophil infiltration compared to CS liver tissues. Conclusion: Reduced IRI in NMP recipients was the consequence of the combination of inhibiting inflammation and promoting graft regeneration.

MerTK expressing hepatic macrophages promote the resolution of inflammation in acute liver failure.

OBJECTIVE: Acute liver failure (ALF) is characterised by overwhelming hepatocyte death and liver inflammation with massive infiltration of myeloid cells in necrotic areas. The mechanisms underlying resolution of acute hepatic inflammation are largely unknown. Here, we aimed to investigate the impact of Mer tyrosine kinase (MerTK) during ALF and also examine how the microenvironmental mediator, secretory leucocyte protease inhibitor (SLPI), governs this response. DESIGN: Flow cytometry, immunohistochemistry, confocal imaging and gene expression analyses determined the phenotype, functional/transcriptomic profile and tissue topography of MerTK+ monocytes/macrophages in ALF, healthy and disease controls. The temporal evolution of macrophage MerTK expression and its impact on resolution was examined in APAP-induced acute liver injury using wild-type (WT) and Mer-deficient (Mer-/-) mice. SLPI effects on hepatic myeloid cells were determined in vitro and in vivo using APAP-treated WT mice. RESULTS: We demonstrate a significant expansion of resolution-like MerTK+HLA-DRhigh cells in circulatory and tissue compartments of patients with ALF. Compared with WT mice which show an increase of MerTK+MHCIIhigh macrophages during the resolution phase in ALF, APAP-treated Mer-/- mice exhibit persistent liver injury and inflammation, characterised by a decreased proportion of resident Kupffer cells and increased number of neutrophils. Both in vitro and in APAP-treated mice, SLPI reprogrammes myeloid cells towards resolution responses through induction of a MerTK+HLA-DRhigh phenotype which promotes neutrophil apoptosis and their subsequent clearance. CONCLUSIONS: We identify a hepatoprotective, MerTK+, macrophage phenotype that evolves during the resolution phase following ALF and represents a novel immunotherapeutic target to promote resolution responses following acute liver injury.

An Atlas of Human Regulatory T Helper-like Cells Reveals Features of Th2-like Tregs that Support a Tumorigenic Environment.

Regulatory T cells (Tregs) play a pivotal role in maintaining immunological tolerance, but they can also play a detrimental role by preventing antitumor responses. Here, we characterized T helper (Th)-like Treg subsets to further delineate their biological function and tissue distribution, focusing on their possible contribution to disease states. RNA sequencing and functional assays revealed that Th2-like Tregs displayed higher viability and autocrine interleukin-2 (IL-2)-mediated activation than other subsets. Th2-like Tregs were preferentially found in tissues rather than circulation and exhibited the highest migratory capacity toward chemokines enriched at tumor sites. These cellular responses led us to hypothesize that this subset could play a role in maintaining a tumorigenic environment. Concurrently, Th2-like Tregs were enriched specifically in malignant tissues from patients with melanoma and colorectal cancer compared to healthy tissue. Overall, our results suggest that Th2-like Tregs may contribute to a tumorigenic environment due to their increased cell survival, higher migratory capacity, and selective T-effector suppressive ability.

Regulatory T-cell conditioning endows activated effector T cells with suppressor function in autoimmune hepatitis/autoimmune sclerosing cholangitis.

Imbalance between T regulatory (Treg) and T effector (Teff) cells is likely to contribute to the induction and perpetuation of liver damage in autoimmune hepatitis (AIH) and autoimmune sclerosing cholangitis (AISC) either through inability of Tregs to restrain proliferation and effector cytokine production by responders or through conversion of Tregs into T helper type 1 (Th1) or type 17 (Th17) effector lymphocytes. We investigated the effect of Treg skewing on the phenotypic and functional properties of CD4+ CD127+ CD25high cells, an activated subset of Teff, in 32 patients with AIH and 20 with AISC and in 36 healthy subjects. In AIH/AISC we noted a substantial increase in peripheral blood-derived CD4+ CD127+ CD25high cells that display a Th1/Th17 phenotypic profile, as reflected by heightened interferon gamma and interleukin 17 (IL-17) production as well as by high levels of T-bet and related orphan receptor 3 expression, which is strongly correlated with disease activity. CD4+ CD127+ CD25high cells are unresponsive to low-dose IL-2 and in patients have marked proliferative ability, further enhanced by stimulation with IL-7. CD4+ CD127+ CD25high cells obtained from CD4+ cells exposed to Treg polarizing conditions display enhanced IL-10 production; up-regulate CD49b and LAG-3, markers of T regulatory 1 cells; and effectively suppress responder cell proliferation in both healthy subjects and AIH/AISC patients through a mechanism which is dependent on interferon gamma and IL-17. The suppressive function of CD4+ CD127+ CD25high cells is maintained upon proinflammatory challenge in healthy subjects but not in AIH/AISC. CONCLUSION: Treg skewing confers activated Teff phenotypic and functional properties of T regulatory 1 cells in health and in AIH/AISC, though suppressive function is lost in patients upon proinflammatory challenge; protracted modulation of the inflammatory environment is required to attenuate the effector potential while boosting immunoregulatory properties in Teff. (Hepatology 2017;66:1570-1584).

Impact of Donation Mode on the Proportion and Function of T Lymphocytes in the Liver.

BACKGROUND: Liver T-cells respond to the inflammatory insult generated during organ procurement and contribute to the injury following reperfusion. The mode of liver donation alters various metabolic and inflammatory pathways but the way it affects intrahepatic T-cells is still unclear. METHODS: We investigated the modifications occurring in the proportion and function of T-cells during liver procurement for transplantation. We isolated hepatic mononuclear cells (HMC) from liver perfusate of living donors (LD) and donors after brain death (DBD) or cardiac death (DCD) and assessed the frequency of T-cell subsets, their cytokine secretion profile and CD8 T-cell cytotoxicity function, responsiveness to a danger associated molecular pattern (High Mobility Group Box1, HMGB1) and association with donor and recipient clinical parameters and immediate graft outcome. RESULTS: We found that T-cells in healthy human livers were enriched in memory CD8 T-cells exhibiting a phenotype of non-circulating tissue-associated lymphocytes, functionally dominated by more cytotoxicity and IFN-γ-production in DBD donors, including upon activation by HMGB1 and correlating with peak of post-transplant AST. This liver-specific pattern of CD8 T-cell was prominent in DBD livers compared to DCD and LD livers suggesting that it was influenced by events surrounding brain death, prior to retrieval. CONCLUSION: Mode of liver donation can affect liver T-cells with increased liver damage in DBD donors. These findings may be relevant in designing therapeutic strategies aimed at organ optimization prior to transplantation.

A novel "humanized mouse" model for autoimmune hepatitis and the association of gut microbiota with liver inflammation.

UNLABELLED: Autoimmune hepatitis (AIH) in humans is a severe inflammatory liver disease characterized by interface hepatitis, the presence of circulating autoantibodies, and hyper-gammaglobulinemia. There are two types of AIH, type 1 (AIH-1) and type 2 (AIH-2), characterized by distinct autoimmune serology. Patients with AIH-1 are positive for anti-smooth muscle and/or antinuclear autoantibodies, whereas patients with AIH-2 have anti-liver kidney microsomal type 1 and/or anti-liver cytosol type 1 autoantibodies. Cytochrome P4502D6 is the antigenic target of anti-liver kidney microsomal type 1, and formiminotransferase cyclodeaminase is the antigenic target of anti-liver cytosol type 1. It is known that AIH, both types 1 and 2, is strongly linked to the human leukocyte antigen (HLA) alleles -DR3, -DR4, and -DR7. However, direct evidence of the association of HLA with AIH is lacking. We developed a novel mouse model of AIH using the HLA-DR3 transgenic mouse on the nonobese-diabetic background by immunization of HLA-DR3- and HLA-DR3+ nonobese-diabetic mice with a DNA plasmid, coding for human cytochrome P4502D6/formiminotransferase cyclodeaminase fusion protein. Immunization with cytochrome P4502D6/formiminotransferase cyclodeaminase leads to a sustained elevation of alanine aminotransferase, development of antinuclear autoantibodies and anti-liver kidney microsomal type 1/anti-liver cytosol type 1 autoantibodies, chronic immune cell infiltration, and parenchymal fibrosis on liver histology in HLA-DR3+ mice. Immunized mice also showed an enhanced T helper 1 immune response and paucity of the frequency of regulatory T cells in the liver. Moreover, HLA-DR3+ mice with exacerbated AIH showed reduced diversity and total load of gut bacteria. CONCLUSION: Our humanized animal model has provided a novel experimental tool to further elucidate the pathogenesis of AIH and to evaluate the efficacy and safety of immunoregulatory therapeutic interventions in vivo.

Hepatitis mouse models: from acute-to-chronic autoimmune hepatitis.

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease associated with interface hepatitis, raised plasma liver enzymes, the presence of autoantibodies and regulatory T-cell (Tregs) dysfunction. The clinical course is heterogeneous, manifested by a fulminant or indolent course. Although genetic predisposition is well accepted, the combination with currently undefined environmental factors is crucial for the development of the disease. Progress in the development of reliable animal models provides added understanding of the pathophysiology of AIH, and these will be very useful in evaluating potential therapeutics. It appears that artificially breaking tolerance in the liver is easy. However, maintaining this state of tolerance breakdown, to get chronic hepatitis, is difficult because liver immune homeostasis is strongly regulated by several immune response inhibitory mechanisms. For example, Tregs are crucial regulators in acute and chronic hepatitis, and C57BL/6 mice are most prone to experimental AIH. Immunization of C57BL/6 mice with liver (AIH) autoantigens (CYP2D6/FTCD or IL-4R) and the disturbance of liver regulatory mechanism(s), leading to experimental AIH, are likely to be most representative of human AIH pathology.

Role of IRAK-M in alcohol induced liver injury.

Increasing evidence suggests that innate immunity plays an important role in alcohol-induced liver injury and most studies have focused on positive regulation of innate immunity. The main objective of this study was to investigate the negative regulator of innate immunity, IL-1/Toll-like receptor (TLR) signaling pathways and interleukin receptor-associated kinase-M (IRAK-M) in alcoholic liver injury. We established an alcohol-induced liver injury model using wild type and IRAK-M deficient B6 mice and investigated the possible mechanisms. We found that in the absence of IRAK-M, liver damage by alcohol was worse with higher alanine transaminase (ALT), more immune cell infiltration and increased numbers of IFNγ producing cells. We also found enhanced phagocytic activity in CD68(+) cells. Moreover, our results revealed altered gut bacteria after alcohol consumption and this was more striking in the absence of IRAK-M. Our study provides evidence that IRAK-M plays an important role in alcohol-induced liver injury and IRAK-M negatively regulates the innate and possibly the adaptive immune response in the liver reacting to acute insult by alcohol. In the absence of IRAK-M, the hosts developed worse liver injury, enhanced gut permeability and altered gut microbiota.