Linking human beta retrovirus infection with primary biliary cirrhosis

Life after Cleavage: The Story of a β-Retroviral (MMTV) Signal Peptide-From Murine Lymphoma to Human Breast Cancer

An increasing body of evidence in recent years supports an association of the betaretrovirus mouse mammary tumor virus (MMTV) with human breast cancer. This is an issue that still raises heated controversy. We have come to address this association using the signal peptide p14 of the MMTV envelope precursor protein as a key element of our strategy. In addition to its signal peptide function, p14 has some significant post endoplasmic reticulum (ER)-targeting characteristics: (1) it localizes to nucleoli where it binds key proteins (RPL5 and B23) involved (among other activities) in the regulation of nucleolar stress response, ribosome biogenesis and p53 stabilization; (2) p14 is a nuclear export factor; (3) it is expressed on the cell surface of infected cells, and as such, is amenable to, and successfully used, in preventive vaccination against experimental tumors that harbor MMTV; (4) the growth of such tumors is impaired in vivo using a combination of monoclonal anti-p14 antibodies or adoptive T-cell transfer treatments; (5) p14 is a phospho-protein endogenously phosphorylated by two different serine kinases. The phosphorylation status of the two sites determines whether p14 will function in an oncogenic or tumor-suppressing capacity; (6) transcriptional activation of genes (RPL5, ErbB4) correlates with the oncogenic potential of MMTV; (7) finally, polyclonal anti-p14 antibodies have been applied in immune histochemistry analyses of breast cancer cases using formalin fixed paraffin-embedded sections, supporting the associations of MMTV with the disease. Taken together, the above findings constitute a road map towards the diagnosis and possible prevention and treatment of MMTV-associated breast cancer.

Mechanisms and molecules: What are the treatment targets for primary biliary cholangitis?

Treatment of primary biliary cholangitis (PBC) with ursodeoxycholic acid (UDCA) is not always sufficient to prevent progression to hepatic decompensation and/or need for liver transplant. Adjuvant therapy with obeticholic acid may provide additional biochemical improvements in some patients, but it is not well-tolerated by patients with significant itch or advanced cirrhosis. Thus, new and creative approaches to treating patients with PBC are important to identify. This review discusses major potential therapeutic targets in PBC and provides examples of some specific agents currently in development for the treatment of PBC. Targets are broadly classified into those which strive to modify bile, inflammation, cell survival, or fibrosis. In bile, shrinking the size of the bile acid pool or modifying the quality of the bile by making it more hydrophilic or enriched in phosphatidylcholine may ameliorate cholestatic injury. Biliary epithelial cell survival may be extended by fortifying the bicarbonate umbrella or improving cell membrane integrity. Autoimmunity and cholangitis have the potential to be improved via regulation of the immune system. Targeting cytokines, immune checkpoints, and anti-mitochondrial antibodies are examples of a more focused immunosuppression approach. Stem cell therapy and lymphocyte trafficking inhibition are more novel methods of broad immune regulation. Anti-fibrotic therapies are also potentially useful for preventing progression of PBC. The nuclear hormone receptors, farnesoid X receptor (FXR) and peroxisome proliferator-activated receptor (PPAR) regulate many of these pathways: cholestasis, inflammation, and fibrosis, which is why they are being enthusiastically pursued as potential therapeutic targets in PBC.

The latest research trends in primary biliary cholangitis: a bibliometric analysis

The bibliometric analysis uses the citation count of an article to measure its impact in the scientific community, but no study has been undertaken to determine the most influential papers in the field of primary biliary cholangitis (PBC). This study aimed to investigate the global research interest regarding PBC in dentistry using a bibliometric approach. We searched the Web of Science Core Collection database to find the top 100 most cited (T100) articles focusing on PBC. The information about each article including citations, authors, journals, countries, institutions, and keywords was recorded for bibliometric analysis. The T100 articles related to PBC were published from 1983 to 2019 and were originated from 26 countries. A total of 805 different authors were from 342 different institutions, and articles written by them were published in 35 journals. The five most frequently occurring keywords were "biochemical response," "ursodeoxycholic acid," "primary biliary cirrhosis," "antimitochondrial antibody," and "autoimmunity." The T100 articles were classified into different research focuses: pathogenesis (41%), treatment (20%), prognosis (12%), epidemiology (9%), diagnosis (8%), and others (10%). These 100 articles included 32 observational studies, 29 basic research articles, 15 reviews, eight meta-analyses, 12 clinical trials, and four clinical guidelines. The 100 top-cited articles are marked with the leading countries, institutions, journals, hotspots, and development trends in the PBC field that could provide the foundation for further investigations.

Mouse Mammary Tumour Virus (MMTV) in Human Breast Cancer—The Value of Bradford Hill Criteria

For many decades, the betaretrovirus, mouse mammary tumour virus (MMTV), has been a causal suspect for human breast cancer. In recent years, substantial new evidence has been developed. Based on this evidence, we hypothesise that MMTV has a causal role. We have used an extended version of the classic A. Bradford Hill causal criteria to assess the evidence. 1. Identification of MMTV in human breast cancers: The MMTV 9.9 kb genome in breast cancer cells has been identified. The MMTV genome in human breast cancer is up to 98% identical to MMTV in mice. 2. Epidemiology: The prevalence of MMTV positive human breast cancer is about 35 to 40% of breast cancers in Western countries and 15 to 20% in China and Japan. 3. Strength of the association between MMTV and human breast cancer: Consistency—MMTV env gene sequences are consistently five-fold higher in human breast cancer as compared to benign and normal breast controls. 4. Temporality (timing) of the association: MMTV has been identified in benign and normal breast tissues up to 10 years before the development of MMTV positive breast cancer in the same patient. 5. Exposure: Exposure of humans to MMTV leads to development of MMTV positive human breast cancer. 6. Experimental evidence: MMTVs can infect human breast cells in culture; MMTV proteins are capable of malignantly transforming normal human breast epithelial cells; MMTV is a likely cause of biliary cirrhosis, which suggests a link between MMTV and the disease in humans. 7. Coherence—analogy: The life cycle and biology of MMTV in humans is almost the same as in experimental and feral mice. 8. MMTV Transmission: MMTV has been identified in human sputum and human milk. Cereals contaminated with mouse fecal material may transmit MMTV. These are potential means of transmission. 9. Biological plausibility: Retroviruses are the established cause of human cancers. Human T cell leukaemia virus type I (HTLV-1) causes adult T cell leukaemia, and human immunodeficiency virus infection (HIV) is associated with lymphoma and Kaposi sarcoma. 10. Oncogenic mechanisms: MMTV oncogenesis in humans probably differs from mice and may involve the enzyme APOBEC3B. Conclusion: In our view, the evidence is compelling that MMTV has a probable causal role in a subset of approximately 40% of human breast cancers.

High occurrence of small intestinal bacterial overgrowth in primary biliary cholangitis

BACKGROUND

Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease affecting mainly middle-aged women. An alteration in intestinal motility has been well documented in cirrhosis predisposing to small intestinal bacterial overgrowth (SIBO). Patients with PBC frequently complain of various gastrointestinal symptoms compatible with SIBO. No study has specifically been published to this day to determine the occurrence of SIBO in PBC. Our objective was to determine the prevalence of SIBO in patients with PBC.

METHODS

Retrospective study from 2010 to 2018. All patients diagnosed with PBC during this period had a systematic screening for SIBO in their diagnostic workup. The diagnosis of SIBO was made by a carbohydrate breath test (lactulose and/or glucose). Clinical and paraclinical factors of patients were compared with a control group of healthy subjects.

KEY RESULTS

Ninety-eight subjects were included in the study (mean age 49, range 21-88 years) including 58 patients with PBC and 40 healthy subjects. The PBC group was older than the control group (mean age 56, range 31-88 vs 39, range 21-62 years; P < .001), but identical for gender and body mass index. The prevalence of SIBO was higher in PBC versus controls (32.8% vs 2.5%; P < .001). The PBC group with SIBO had significantly more diarrhea (78.9% vs 35.9%; P < .05) than the PBC group without SIBO, but the prevalence of abdominal pain and bloating was similar.

CONCLUSIONS & INFERENCES

The high occurrence of SIBO in PBC may explain some of the frequently reported gastrointestinal symptoms. This study justifies the systematic screening for SIBO in PBC.

Epidemiology and liver transplantation burden of primary biliary cholangitis: a retrospective cohort study

BACKGROUND

There is a wealth of data documenting the epidemiology of primary biliary cholangitis (PBC) globally; however, the epidemiology of PBC has not been as well studied in Canada. Our study characterized the Canadian prevalence of PBC and the number of liver transplantations because of PBC.

METHODS

For this retrospective cohort study we used national hospital administrative records from the Canadian Institute for Health Information, with the exception of Quebec for the prevalence estimate and Quebec and British Columbia for the transplant analysis. Prevalent patients were identified through a diagnostic code for PBC of the Canadian version of the 10th revision of the International Classification of Diseases. PBC transplant patients were identified from their transplant record. Descriptive statistics were used to summarize the characteristics of the study cohorts.

RESULTS

In 2015, 8680 patients with PBC were identified in Canada, translating to a prevalence of 318 cases per million. Annual prevalence by province varied, ranging from 283 (95% confidence interval [CI] 269-297) cases per million to 465 (95% CI 426-504) cases per million, and the 6-year PBC liver transplantation rate ranged from 3.17 (95% CI 1.27-6.54) to 5.92 (95% CI 3.71-9.08) per million. The Atlantic provinces exhibited the highest PBC prevalence and close to the highest 6-year liver transplantation rate (465 [95% CI 426-504] cases per million and 5.70 [95% CI 426-504, 3.19-9.56] cases per million, respectively). We observed the lowest PBC prevalence (283 [95% CI 269-297] cases per million) and the second lowest 6-year liver transplantation rate in Ontario (3.37 [95% CI 2.47-4.50] cases per million).

INTERPRETATION

The prevalence of PBC that we found in Canada is similar to the prevalence reported in other studies, but our work also indicates geographic variation within this country. Given our finding of geographic clustering of PBC across Canada, we hypothesize that environmental and genetic factors contribute to the pathogenesis of this condition.

A new immunization and treatment strategy for mouse mammary tumor virus (MMTV) associated cancers

Mouse Mammary Tumor Virus (MMTV) causes mammary carcinoma or lymphoma in mice. An increasing body of evidence in recent years supports its involvement also in human sporadic breast cancer. It is thus of importance to develop new strategies to impair the development, growth and metastasis of MMTV-associated cancers. The signal peptide of the envelope precursor protein of this virus: MMTV-p14 (p14) is an excellent target for such strategies, due to unique characteristics distinct from its regular endoplasmic reticulum targeting function. These include cell surface expression in: murine cancer cells that harbor the virus, human breast cancer (MCF-7) cells that ectopically express p14, as well as cultured human cells derived from an invasive ductal breast carcinoma positive for MMTV sequences. These findings support its use in signal peptide-based immune targeting. Indeed, priming and boosting mice with p14 elicits a specific anti-signal peptide immune response sufficient for protective vaccination against MMTV-associated tumors. Furthermore, passive immunization using a combination of anti-p14 monoclonal antibodies or the transfer of T-cells from immunized mice (Adoptive Cell Transfer) is also therapeutically effective. With reports demonstrating involvement of MMTV in human breast cancer, we propose the immune-mediated targeting of p14 as a strategy for prevention, treatment and diagnosis of MMTV-associated cancers.

Novel Therapies on Primary Biliary Cirrhosis

All patients with primary biliary cirrhosis (PBC) and abnormal liver biochemistry should be considered for specific therapy. Ursodeoxycholic acid (UDCA) is the only FDA-approved drug for treating PBC. Approximately 40% of patients with PBC respond incompletely to treatment with UDCA, thus having increased risk of death or need for liver transplantation. No second-line therapies for patients with inadequate response to UDCA therapy have been approved. This review provides a current perspective on potential new approaches to treatment in PBC, and highlights some of the challenges we face in evaluating and effectively implementing those treatments.

Primary biliary cirrhosis: From bench to bedside

Primary biliary cirrhosis (PBC) is a chronic non-suppurative destructive intrahepatic cholangitis leading to cirrhosis after a protractive non cirrhotic stage. The etiology and pathogenesis are largely unknown and autoimmne mechanisms have been implicated to explain the pathological lesions. Many epitopes and autoantigens have been reported as crucial in the pathophysiology of the disease and T and B cells abnormalities have been described, the exact pathways leading to the destruction of small intrahepatic ductules are mostly speculative. In this review we examined the various epidemiologal and geoepidemiological data as well as the complex pathogenetic aspects of this disease, focusing on recent in vivo and in vitro studies in this field. Initiation and progression of PBC is believed to be a multifactorial process with strong infuences from the patient’s genetic background and by various environmental factors. The role of innate and adaptive immunity, including cytokines, chemokines, macrophages and the involvement of apoptosis and reactive oxygen species are outlined in detailed. The current pathogenetic aspects are presented and a novel pathogenetic theory unifying the accumulated clinical information with in vitro and in vivo data is formulated. A review of clinical manifestations and immunological and pathological diagnosis was presented. Treatment modalities, including the multiple mechanisms of action of ursodeoxycholate were finally discussed.

Novel therapeutic targets in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic immune-mediated liver disease characterized by progressive cholestasis, biliary fibrosis and eventually cirrhosis. It results in characteristic symptoms with marked effects on life quality. The advent of large patient cohorts has challenged the view of PBC as a benign condition treated effectively by the single licensed therapy-ursodeoxycholic acid (UDCA). UDCA nonresponse or under-response has a major bearing on outcome, substantially increasing the likelihood that liver transplantation will be required or that patients will die of the disease. In patients with high-risk, treatment-unresponsive or highly symptomatic disease the need for new treatment approaches is clear. Evolution in our understanding of disease mechanisms is rapidly leading to the advent of new and re-purposed therapeutic agents targeting key processes. Notable opportunities are offered by targeting what could be considered as the 'upstream' immune response, 'midstream' biliary injury and 'downstream' fibrotic processes. Combination therapy targeting several pathways or the development of novel agents addressing multiple components of the disease pathway might be required. Ultimately, PBC therapeutics will require a stratified approach to be adopted in practice. This Review provides a current perspective on potential approaches to PBC treatment, and highlights the challenges faced in evaluating and implementing those treatments.

Differential binding of pyruvate dehydrogenase complex-E2 epitopes by DRB1*08:01 and DRB1*11:01 Is predicted by their structural motifs and correlates with disease risk

DRB1*08:01 (DR0801) and DRB1*11:01 (DR1101) are highly homologous alleles that have opposing effects on susceptibility to primary biliary cirrhosis (PBC). DR0801 confers risk and shares a key feature with other HLA class II alleles that predispose to autoimmunity: a nonaspartic acid at beta57. DR1101 is associated with protection from PBC, and its sequence includes an aspartic acid at beta57. To elucidate a mechanism for the opposing effects of these HLA alleles on PBC susceptibility, we compared the features of epitopes presented by DR0801 and DR1101. First, we identified DR0801- and DR1101-restricted epitopes within multiple viral Ags, observing both shared and distinct epitopes. Because DR0801 is not well characterized, we deduced its motif by measuring binding affinities for a library of peptides, confirming its key features through structural modeling. DR0801 was distinct from DR1101 in its ability to accommodate charged residues within all but one of its binding pockets. In particular, DR0801 strongly preferred acidic residues in pocket 9. These findings were used to identify potentially antigenic sequences within PDC-E2 (an important hepatic autoantigen) that contain a DR0801 motif. Four peptides bound to DR0801 with reasonable affinity, but only one of these bound to DR1101. Three peptides, PDC-E2145-159, PDC-E2(249-263), and PDC-E2(629-643), elicited high-affinity T cell responses in DR0801 subjects, implicating these as likely autoreactive specificities. Therefore, the unique molecular features of DR0801 may lead to the selection of a distinct T cell repertoire that contributes to breakdown of self-tolerance in primary biliary cirrhosis, whereas those of DR1101 promote tolerance.

Is there a role for cyclophilin inhibitors in the management of primary biliary cirrhosis?

Autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC) are poorly understood autoimmune liver diseases. Immunosuppression is used to treat AIH and ursodeoxycholic acid is used to slow the progression of PBC. Nevertheless, a proportion of patients with both disorders progress to liver failure. Following liver transplantation, up to a third of patients with PBC experience recurrent disease. Moreover a syndrome referred to as "de novo AIH" occurs in a proportion of patients regardless of maintenance immunosuppression, who have been transplanted for disorders unrelated to AIH. Of note, the use of cyclosporine A appears to protect against the development of recurrent PBC and de novo AIH even though it is a less potent immunosuppressive compared to tacrolimus. The reason why cyclosporine A is protective has not been determined. However, a virus resembling mouse mammary tumor virus (MMTV) has been characterized in patients with PBC and AIH. Accordingly, we hypothesized that the protective effect of cyclosporine A in liver transplant recipients may be mediated by the antiviral activity of this cyclophilin inhibitor. Treatment of the MMTV producing MM5MT cells with different antivirals and immunosuppressive agents showed that both cyclosporine A and the analogue NIM811 inhibited MMTV production from the producer cells. Herein, we discuss the evidence supporting the role of MMTV-like human betaretrovirus in the development of PBC and de novo AIH and speculate on the possibility that the agent may be associated with disease following transplantation. We also review the mechanisms of how both cyclosporine A and NIM811 may inhibit betaretrovirus production in vitro.

Etiopathogenesis of primary biliary cirrhosis: an overview of recent developments

Substantial advancements in the field of primary biliary cirrhosis (PBC) research have broadened our understanding of this enigmatic disease. Genome-wide studies have identified several new candidate genes involved in the immunoregulatory process, particularly those responsible for antigen presentation and lymphocyte signaling. Examples include the HLA class-II region and genes implicated in IL12-JAK/STAT signaling, and the NF-κB and TNF signaling pathways. Environmental triggers appear to disrupt the pre-existing, unstable immune tolerance in genetically susceptible individuals, and molecular mimics of the PBC-specific autoantigen (PDC) may be derived from microbes or xenobiotic compounds, which modify native proteins, making them immunogenic. Although the vast majority of patients with PBC are AMA-positive, a variety of disease-specific antinuclear antibodies have been recognized in conferring a worse clinical outcome. There has also been a revived interest in the role of antibody-secreting B cells in murine models suggesting that depletion of these cells paradoxically exacerbates cholangiopathy. Biliary specificity in PBC is most likely driven by the uniqueness of cholangiocyte apoptosis in which the PDC-E2 autoantigen undergoes differential glutathiolation. Cholangiocytes also possess the ability to phagocytose neighboring apoptotic cells, present intact immunoreactive antigen, and undergo attack from autoantibodies, the innate immune system, and autoreactive lymphocytes. Cellular senescence and a lack of functioning T-regulatory cells are proposed mechanisms by which this multi-lineage process is thought to be enhanced. This review summarizes these key advances as the true complexities of the disease process begin to be unraveled.

Immunopathogenesis of primary biliary cirrhosis: an old wives' tale

Primary biliary cirrhosis (PBC) is a cholestatic liver disease characterised by the autoimmune destruction of the small intrahepatic bile ducts. The disease has an unpredictable clinical course, but may progress to fibrosis and cirrhosis. Although medical treatment with urseodeoxycholic acid is largely successful, some patients may progress to liver failure requiring liver transplantation. PBC is characterised by the presence of disease specific anti-mitochondrial (AMA) antibodies, which are pathognomonic for PBC development. The disease demonstrates an overwhelming female preponderance and virtually all women with PBC present in middle age. The reasons for this are unknown; however several environmental and immunological factors may be involved. As the immune systems ages, it become less self tolerant, and mounts a weaker response to pathogens, possibly leading to cross reactivity or molecular mimicry. Some individuals display immunological changes which encourage the development of autoimmune disease. Risk factors implicated in PBC include recurrent urinary tract infection in females, as well as an increased prevalence of reproductive complications. These risk factors may work in concert with and possibly even accelerate, immune system ageing, contributing to PBC development. This review will examine the changes that occur in the immune system with ageing, paying particular attention to those changes which contribute to the development of autoimmune disease with increasing age. The review also discusses risk factors which may account for the increased female predominance of PBC, such as recurrent UTI and oestrogens.

Identification, characterization, and comparative genomic distribution of the HERV-K (HML-2) group of human endogenous retroviruses

BACKGROUND

Integration of retroviral DNA into a germ cell may lead to a provirus that is transmitted vertically to that host's offspring as an endogenous retrovirus (ERV). In humans, ERVs (HERVs) comprise about 8% of the genome, the vast majority of which are truncated and/or highly mutated and no longer encode functional genes. The most recently active retroviruses that integrated into the human germ line are members of the Betaretrovirus-like HERV-K (HML-2) group, many of which contain intact open reading frames (ORFs) in some or all genes, sometimes encoding functional proteins that are expressed in various tissues. Interestingly, this expression is upregulated in many tumors ranging from breast and ovarian tissues to lymphomas and melanomas, as well as schizophrenia, rheumatoid arthritis, and other disorders.

RESULTS

No study to date has characterized all HML-2 elements in the genome, an essential step towards determining a possible functional role of HML-2 expression in disease. We present here the most comprehensive and accurate catalog of all full-length and partial HML-2 proviruses, as well as solo LTR elements, within the published human genome to date. Furthermore, we provide evidence for preferential maintenance of proviruses and solo LTR elements on gene-rich chromosomes of the human genome and in proximity to gene regions.

CONCLUSIONS

Our analysis has found and corrected several errors in the annotation of HML-2 elements in the human genome, including mislabeling of a newly identified group called HML-11. HML-elements have been implicated in a wide array of diseases, and characterization of these elements will play a fundamental role to understand the relationship between endogenous retrovirus expression and disease.

Mouse mammary tumor virus in anti-mitochondrial antibody producing mouse models

BACKGROUND & AIMS

A human betaretrovirus resembling the mouse mammary tumor virus (MMTV) has been characterized in primary biliary cirrhosis (PBC) and associated with aberrant pyruvate dehydrogenase complex (PDC)-E2-like expression. As MMTV is prevalent in mice as either an exogenous or endogenous infection, we tested the hypothesis that MMTV is linked with anti-mitochondrial antibody (AMA) production in models with severe immune dysfunction.

METHODS

Evidence for MMTV was assessed in the liver and spleen of mice by PCR and immunochemistry and PDC-E2-like protein by immunochemistry. ELISA and Western blot were used to investigate AMA and anti-MMTV antibody production.

RESULTS

Increased MMTV gag or env expression was detected in the livers of AMA producing mice including NOD.c3c4, CD4 directed dominant negative TGF-β receptor II and IL-2 receptor α knockout mice as well as the NOD parental strain when compared to healthy strains and biliary disease control mice. The NOD.c3c4 mice expressed MMTV surface and capsid proteins and aberrant PDC-E2-like protein in the bile ducts, whereas IL-2 receptor α knockout mice, NOD.c3c4 and the NOD mice expressed MMTV proteins and aberrant PDC-E2-like protein in the spleen. A significant correlation between anti-MMTV antibody production and AMA production was observed in the sera of NOD and NOD.c3c4 mice (p<0.0001).

CONCLUSIONS

The association of betaretroviral protein production and aberrant PDC-E2-like protein expression in the NOD.c3c4, NOD, and the IL-2 receptor α knockout mice is comparable to observations in patients with PBC. The correlation of AMA and anti-MMTV suggests the hypothesis that MMTV infection may trigger the production of AMA.

Role of the anion exchanger 2 in the pathogenesis and treatment of primary biliary cirrhosis

The essential anion exchanger (AE) involved in biliary bicarbonate secretion is AE2/SLC4A2, a membrane protein which has also been recognized to be relevant for the regulation of the intracellular pH (pH(i)) in several cell types. Previously, we reported that the expression of AE2 mRNA is diminished in liver biopsies and peripheral blood mononuclear cells from patients with primary biliary cirrhosis (PBC). Immunohistochemical studies indicated that the expression of the AE2 protein is decreased in the bile ducts and hepatocytes in PBC livers. Moreover, we found that bile duct cells isolated from PBC patients and cultured for a few passages exhibit defective Na(+)-independent Cl(-)/HCO(3)(-) exchange. Interestingly, positron emission tomography studies have shown that PBC patients, even at early stages of the disease, fail to secrete bicarbonate to bile in response to secretin, a defect that can be partially reversed after several months of treatment with ursodeoxycholic acid. Altogether, these findings sustain our hypothesis that dysfunctions related to AE2 might have a role in the pathogenesis of PBC. Inadequate AE2 function in lymphocytes may disturb pH(i) regulation in these cells and alter immune homeostasis leading to autoimmunity. On the other hand, reduced AE2 in cholangiocytes could cause cholestasis and oxidative stress of bile duct cells. Cholangiocyte changes, together with altered immune homeostasis, could favor the development of antimitochondrial antibodies and the autoimmune attack on biliary ducts. Our recent findings that Ae2(a,b)-deficient mice indeed display most of these features strongly support the notion that AE2 abnormalities may be involved in the pathogenesis of PBC.

Disease-specific autoantibodies in primary biliary cirrhosis

Anti-mitochondrial autoantibodies (AMA) are specific markers of primary biliary liver cirrhosis (PBC), a cholestatic autoimmune disease which is characterised by a progressive destruction of the biliary epithelial cells followed by fibrosis, cirrhosis and liver failure. The prevalence of AMA in PBC is more than 90% and they can precede long before the clinical symptoms. AMA are conventionally detected by indirect immunofluorescence (IIF) using rodent liver, kidney, and stomach sections as substrates. Additionally, different PBC-specific anti-nuclear autoantibodies (ANA) can be observed in 30% of patients presenting with multiple nuclear dot or nuclear membrane staining patterns, which preferentially are identified using HEp-2 cells as substrate. The identification of the major PBC-specific mitochondrial and nuclear targets has allowed the generation of monospecific antigenic targets which are increasingly used in solid-phase assays for routine detection of AMA and ANA in mono- or multiparametric screen test systems. In the present paper, we give an overview of the diagnostic significance of autoantibodies in PBC, discuss the competencies of different techniques used for their determination and propose an effective diagnostic strategy.