Anti-mitochondrial antibody-negative primary biliary cirrhosis

Autotaxin: A Potential biomarker for primary biliary cholangitis

Background

In some patients especially those AMA negative, the diagnosis may be a challenge requiring liver biopsy. This study determined whether autotaxin, a secreted lysophospholipase D encoded by the exonucleotide pyrophosphatase phosphodiesterase 2 gene, can be used as a serum biomarker for primary biliary cholangitis.

Methods

Plasma samples were collected from 103 patients with PBC and 74 healthy controls. autotaxin levels were determined by Enzyme-linked immunosorbent assay, and its predictive value for diagnosing primary biliary cholangitis was analysed. The relationship between autotaxin and the clinical data was also evaluated.

Results

Autotaxin levels in patients with primary biliary cholangitis were significantly higher than those in healthy control (median: 60.7 ng/ml vs. 32.6 ng/ml, P < 0.001). The cut-off value of autotaxin in patients with primary biliary cholangitis was 38.5 ng/ml, and the positivity rate was 33.9 %, calculated twice. The sensitivity, specificity, positive predictive value, and negative predictive value were 54.3 %, 93.1 %, 84.4 %, and 74.8 %, respectively, and the area under the curve was 0.73. Autotaxin level positively correlated with immunoglobulin M level (r = -0.22, P < 0.05) and Ludwig's classification (r = 0.76, P < 0.01) in patients with primary biliary cholangitis. The positivity rate of autotaxin (50.0 %) was higher than that of anti-sp100 (16.7 %) and anti-gp210 (11.1 %) antibodies in anti-mitochondrial antibody -negative patients with primary biliary cholangitis.

Conclusions

Autotaxin may be an effective noninvasive biomarker used in diagnosis, prognosis of primary biliary cholangitis, particularly in anti-mitochondrial antibody -negative patients.

Anti-mitochondrial Antibody-Negative Primary Biliary Cholangitis Is Part of the Same Spectrum of Classical Primary Biliary Cholangitis

BACKGROUND

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease in which anti-mitochondrial antibodies (AMA) are the diagnostic hallmark. Whether AMA-negative PBC patients represent a different phenotype of disease is highly debated.

AIMS

The purpose of our study was to compare AMA-positive and AMA-negative PBC patients in a large non-white admixed Brazilian cohort.

METHODS

The Brazilian Cholestasis Study Group multicentre database was reviewed to assess demographics, clinical features and treatment outcomes of Brazilian PBC patients, stratifying data according to AMA status.

RESULTS

A total of 464 subjects (95.4% females, mean age 56 ± 5 years) with PBC were included. Three hundred and eighty-four (83%) subjects were AMA-positive, whereas 80 (17%) had AMA-negative PBC. Subjects with AMA-negative PBC were significantly younger (52.2 ± 14 vs. 59.6 ± 11 years, p = 0.001) and had their first symptom at an earlier age (43.2 ± 13 vs. 49.5 ± 12 years, p = 0.005). Frequency of type 2 diabetes was significantly increased in subjects with AMA-negative PBC (22.5% vs. 12.2%, p = 0.03). Lower IgM (272.2 ± 183 vs. 383.2 ± 378 mg/dL, p = 0.01) and triglycerides (107.6 ± 59.8 vs.129.3 ± 75.7 mg/dL, p = 0.025) and higher bilirubin (3.8 ± 13.5 vs. 1.8 ± 3.4 mg/dL, p = 0.02) levels were also observed in this subgroup. Response to ursodeoxycholic acid varied from 40.5 to 63.3% in AMA-positive and 34 to 62.3% in AMA-negative individuals, according to different response criteria. Outcomes such as development of liver-related complications, death and requirement for liver transplantation were similar in both groups.

CONCLUSIONS

AMA-negative PBC patients are similar to their AMA-positive counterparts with subtle differences observed in clinical and laboratory features.

Antimitochondrial Antibodies: from Bench to Bedside

Anti-mitochondrial antibodies (AMA) are directed against the E2 subunits of the 2-oxo acid dehydrogenase complexes (PDC-E2) and are the typical biomarkers of primary biliary cholangitis (PBC), being present in 90-95% of patients, with increasing sensitivity at increasing titers. Albeit being highly specific for PBC diagnosis, AMA can be detected in less than 1% of healthy subjects, and thus the management subjects with no sign or symptom of liver disease is still a challenge and data concerning clinical risk of developing PBC in this subgroup of patients are controversial. Moreover, AMA can also be detected in patients affected by overlap syndrome, as well as hepatic diseases (i.e., NASH and viral hepatitis), while the association with autoimmune diseases, in particular Sjögren's syndrome, systemic sclerosis, and systemic lupus erythematosus, is well established. Furthermore, new associations are being identified with inflammatory myositis and heart disease. AMA are directed towards the pyruvate dehydrogenase multi enzyme complex (PDC-E2) subunit, which represents an epithelial specific autoantigen for PBC. This review focuses on the main characteristics of AMA, their association with autoimmune diseases and liver diseases.

The diagnosis of antimitochondrial antibody-negative primary biliary cholangitis

Autoimmune liver diseases are heterogenous disorders that share largely non-specific clinical, serological and pathological features. The correct diagnosis requires discriminative features which are highly specific, for example high-titer antimitochondrial antibodies (AMA) and florid duct lesion in primary biliary cholangitis (PBC). However, the imperfect sensitivities of these characteristic features and abuse of scoring systems led to many artificial diagnoses such as overlap syndromes and outliers for example "autoimmune cholangitis" which is now called as "AMA-negative PBC". Patients lacking detectable AMA (up to 20% in indirect immunofluorescence - IF), but otherwise presenting signs and symptoms of PBC should be regarded as affected by "AMA-negative PBC" because they seem to follow a natural history similar to that of their AMA positive counterparts. The complementary use of IF, ELISA and immunoblotting have disclosed that the majority of patients initially considered AMA-negative are in fact AMA positive. Moreover, the use of PBC-specific ANA's like Gp210 and sp100 have diminished the AMA-negative cases (if truly exists!) to less than 5%. The histological spectrum of PBC includes typical florid duct lesions and/or compatible features such as non-specific hepatitic and biliary findings. In the absence of florid duct lesion and AMA positivity, histology alone cannot differentiate PBC from other biliary disorders. However, the analysis of compatible histological features with the clinical, serological and imaging findings usually points to a specific diagnosis. In this review, we present serological, clinical and pathological pitfalls regarding AMA-negative PBC including illustrative cases and a diagnostic algorithm.

Practical guidelines for examination of adults with asymptomatic hypertransaminasaemia

The causes of sustained elevation of serum transaminases in asymptomatic adults, both hepatic and extrahepatic, are varied. In order to reach an aetiological diagnosis, a standardized protocol should be applied, aimed firstly at ruling out the most common causes, such as chronic hepatitis (viral or autoimmune), metabolic diseases, and toxic liver diseases. Several biochemical patterns, which take into account transaminase, cholestatic enzyme, muscle enzyme, ferritin and ceruloplasmin levels, as well protein electrophoresis and autoantibody measurement, will identify most causes. In cases in which a diagnosis cannot be reached with the use of these non-invasive methods, a needle liver biopsy will be justified.

The accuracy of the anti-mitochondrial antibody and the M2 subtype test for diagnosis of primary biliary cirrhosis: a meta-analysis

The aim of this study was to evaluate the diagnostic value of anti-mitochondrial antibodies (AMAs) and/or the M2 subtype (AMA-M2) in patients with primary biliary cirrhosis (PBC). AMA/AMA-M2 data were obtained by searching electronic databases. Studies showing AMA/AMA-M2 results in patients with PBC and control groups with other liver diseases or healthy livers were included. The quality of the involved studies was assessed using the QUADAS tool. The pooled sensitivity and specificity were calculated, and stratified analysis was performed according to possible heterogeneity sources. The pooled AMA (all methods) sensitivity and specificity were 84.5% (95% confidence interval (CI) 83.3%-85.6%) and 97.8% (95% CI 97.6%-98.0%), respectively. The positive and negative likelihood ratios were 25.201 (95% CI 17.583-36.118) and 0.162 (95% CI 0.131-0.199), respectively. The current evidence suggests that AMA and AMA-M2 show favorable accuracy for the diagnosis of PBC with high specificity and sensitivity. AMA is a better and more comprehensive marker than AMA-M2. The accuracy established in this meta-analysis is based on clinical studies using patient cohorts from different ethnicities.

Clinical significance of the fluctuation of primary biliary cirrhosis-related autoantibodies during the course of the disease

Primary biliary cirrhosis (PBC) is a chronic cholestatic disease characterized by the presence of antimitochondrial antibodies (AMA). PBC-specific antinuclear antibodies (ANA) have been characterized and associated with disease progression and outcome. We evaluated the clinical significance of the presence and serial changes in titers of AMA, PBC-specific ANA (anti-gp210, anti-sp100) and anti-chromatin antibodies. Over a median (IQR) period of 35 (36) months, 512 specimens were collected from 110 patients. Autoantibodies were detected by commercial ELISAs (INOVA Diagnostics). Biochemical, clinical, and histological status were included at initial presentation and during follow-up visits. The Mayo risk score was calculated as a prognostic index at each time point. Liver biopsy findings were classified according to Ludwig's classification and biochemical response to ursodeoxycholic acid was evaluated according to Pares. At baseline, AMA IgG and IgA, anti-gp210 IgG, anti-sp100 IgG and anti-chromatin IgG were detected in 92/110 (83.6%), 57/110 (51.8%), 5/110 (4.5%), 14/110 (12.7%), and 0/110 (0%) patients, respectively. Positivity for all autoantibodies apart from anti-chromatin, at baseline visit (n = 110 patients), in all tested sera (n = 512) as well as increased autoantibodies titers during follow-up were associated with biochemically and/or histologically advanced disease. A decrease of anti-sp100 titers but not of anti-gp210 titers during follow-up was associated with improvement of Mayo risk score (p = 0.025) and response to ursodeoxycholic acid (p = 0.016). These results suggest that detection of AMA and PBC-specific ANA was correlated with disease severity. Serial changes of anti-sp100 titers and not of anti-gp210 titers might prove useful for monitoring the disease course and treatment outcome.

Serum markers of infections in patients with primary biliary cirrhosis: evidence of infection burden

BACKGROUND

Currently not much is known regarding the environmental factors involved in primary biliary cirrhosis (PBC). It is even more unclear which factors may determine the subgroup (i.e., AMA status) of patients with PBC. We thus tested AMA+and AMA- PBC patients' sera for antibodies (Abs) against multiple infectious agents.

METHODS

Sera from 69 patients with PBC (49 AMA+and 20 AMA-) and 100 matched controls were screened for IgG-Abs against Toxoplasma gondii, Helicobacter pylori, Epstein-Barr virus (EBV), cytomegalovirus (CMV), hepatitis B, and hepatitis C utilizing the BioPlex 2200 and ELISA kits (Bio-Rad Laboratories, USA).

RESULTS

The prevalence of four anti-infectious agents Abs was significantly elevated among PBC patients when compared with controls, namely anti-T. gondii (ATxA; 71% vs. 40%, p<0.0001), EBV early antigen (EA; 44% vs. 12%, p<0.0001), H. pylori (54% vs. 31%, p<0.01), and CMV (90% vs. 75%, p<0.05) Abs, respectively. The co-occurrence of these four anti-infectious agents Abs was highly common in PBC, whereas this infection burden was rare in healthy subjects (20% vs. 3% respectively, p<0.0001). Furthermore, specific infections interactions possibly increasing PBC risk were noted as well. Seropositivity of ATxA was inversely associated with cirrhosis among PBC patients (p<0.05). Finally, no differences were observed between AMA- sera and their AMA+counterparts with regard to seroprevalence of any of the investigated infectious agents.

CONCLUSIONS

We note the association of ATxA and PBC, with the possibility of a milder disease manifestation. We also suggest that multiple exposures to infectious agents may contribute to PBC risk.

Clinical features of primary biliary cirrhosis: An analysis of 114 cases

AIM: To summarize the clinical characteristics of primary biliary cirrhosis (PBC) and to explore the clinical significance of serum anti-mitochondrial antibodies (AMAs) in the diagnosis and assessment of severity of PBC.

METHODS: A retrospective analysis of clinical manifestations, serum biochemical parameters, serum antibodies and pathological features was performed in 114 patients with PBC. M2 antibody-positive patients (105 cases) were divided into four groups: those positive for only M2 (61 cases), for both M2 and M9 (9 cases), for both M2 and M4 (25 cases), and for M2, M4, and M9 (10 cases). Serological markers and complications were compared among the four groups.

RESULTS: Main clinical manifestations of PBC include fatigue, jaundice, and skin itching. The levels of alkalinity phosphatase (ALP), γ-glutamyl transpeptidase (GGT), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (TBIL) increased to varying degrees. Serum AMA and M2 antibodies had a very high specificity and sensitivity in diagnosing PBC. Compared to the M2-positive group, the levels of ALP and IgM in M2-M4-positive group were higher (P = 0.010, 0.014, P < 0.05). Compared to the M2-M9-positive group, the levels of AST, TBIL, and IgG in the M2-M4-M9 positive group were higher (P = 0.039, 0.016, 0.039, P < 0.05). Compared to the M2-positive group, the level of TBIL in the M2-M4-M9 positive group was higher (P = 0.023, P < 0.05). Compared to the M2-M9 positive group, the level of IgG in the M2-positive group was higher (P = 0.031, P < 0.05). Thus, serum M4 and M9 levels have clinical significance in the diagnosis of PBC.

CONCLUSION: Understanding the clinical characteristics of PBC can help improve the diagnosis, treatment, and prognosis of this disease.

Primary biliary cirrhosis and Sjögren's syndrome: autoimmune epithelitis

Primary biliary cirrhosis (PBC) has been often coined a model autoimmune disease based on the homogeneity amongst patients, the frequency and similarity of antimitochondrial antibodies, including the highly directed immune response to pyruvate dehydrogenase (PDC-E2). A significant number of patients with PBC suffer from sicca and amongst these, there are patients who also have classic Sjögren's syndrome. Indeed, both PBC and Sjögren's syndrome are characterized by inflammation of target epithelial elements. Both diseases can be considered on the basis of a number of other related clinical aspects, including proposed unique apoptotic features of the target tissue, the role of secretory IgA, and the frequency with which both diseases overlap with each other. Indeed, PBC may be considered a Sjögren's syndrome of the liver, whereas Sjögren's syndrome can be equally discussed as PBC of the salivary glands. Dissection of the genetic predispositions for both diseases and especially the molecular basis of effector mechanisms, will become critical elements in developing new therapies.

Primary biliary cirrhosis-related autoantibodies in a large cohort of italian patients with systemic sclerosis

OBJECTIVE

To analyze the prevalence, associations, and fine specificity of autoantibodies to primary biliary cirrhosis (PBC)-associated antigens (MIT3, Sp100, and gp210) in a cohort of Italian patients with systemic sclerosis (SSc).

METHODS

Sera samples from 201 patients with SSc were tested for antibodies to MIT3, gp210, and Sp100 by ELISA (the PBC screen). Anti-MIT3-positive sera were studied for IgG or IgA isotypes. All sera were analyzed by indirect immunofluorescence on HEp-2 cells and on rodent kidney/stomach/liver tissue sections in order to detect antinuclear and antimitochondrial antibodies (AMA). SSc was selected by American College of Rheumatology criteria and classified based on LeRoy's criteria.

RESULTS

Forty-three (21.4%) sera samples were positive for PBC screen antibodies. Anti-MIT3 antibodies were detected in 36 samples, anti-Sp100 in 5, and anti-gp210 in 1 sample. The other 3 PBC screen-positive samples showed no specificity for the single antigens. PBC screen-positive patients more frequently showed a limited cutaneous SSc subtype (p = 0.04), anticentromere antibodies (ACA; p = 0.0013), elevated alkaline phosphatase (ALP) (p < 0.0001), PBC (p = 0.002), and AMA (p = 0.008). Teleangiectasia and calcinosis were less frequent in this group of patients. IgG+IgA anti-MIT3-positive patients had higher prevalence of AMA (p = 0.0035), diagnosis of PBC (p = 0.014), and increased ALP (p = 0.039), all considered biochemical markers of severe liver disease.

CONCLUSION

PBC screen antibodies were detected in 20% of patients with SSc, strongly associated with ACA. ACA+/PBC screen+ patients had higher risk of developing PBC or elevation of ALP.

Fetomaternal alloimmunity as a cause of liver disease

Fetomaternal alloimmune disease has traditionally been associated with haematological disease such as fetomaternal alloimmune thrombocytopaenia and Rh haemolytic anaemia, but is now known to also be organ specific. Alloimmune membranous glomerulonephritis (AMG) is one of the most well understood organ-specific alloimmune diseases. Neonatal haemochromatosis (NH) is a rare condition characterised by early liver failure in infants, with evidence suggesting that it is also alloimmune. Both AMG and NH appear to involve the passive transfer of alloantibodies to the fetus, which bind a specific alloantigen, fix complement and activate the terminal complement cascade. Although differences between AMG and NH are known, and evidence of the presence of antigen-specific alloantibodies in NH is still missing, we will use AMG as an example of fetomaternal organ specific alloimmune disease, and critically compare this to other emerging evidence that indicates that NH is also alloimmune.

Immune-mediated bile duct injury: The case of primary biliary cirrhosis

Autoimmune cholangitis would be the appropriate name to define the immune-mediated bile duct injury following the breakdown of tolerance to mitochondrial proteins and the appearance of serum autoantibodies and autoreactive T cells. Nevertheless, the condition is universally named primary biliary cirrhosis (PBC). The disease etiology and pathogenesis remain largely unknown despite the proposed lines of evidence. One twin study and numerous epidemiology reports suggest that both a susceptible genetic background and environmental factors determine disease onset while a recent genome-wide association study proposed highly significant associations with several common genetic polymorphisms in subgroups of patients. Specific infectious agents and chemicals may contribute to the disease onset and perpetuation in a genetically susceptible host, possibly through molecular mimicry. Importantly, several murine models have been proposed and include strains in which PBC is genetically determined or induced by immunization with chemicals and bacteria. From a pathogenetic standpoint, new exciting data have demonstrated the unique apoptotic features of bile duct cells that allow the mitochondrial autoantigens to be taken up in their intact form within apoptotic blebs. We are convinced that the application of the most recent molecular techniques will soon provide developments in PBC etiology and pathogenesis with likely implications in diagnostics and therapeutics.

The spectrum of autoantibodies in IPEX syndrome is broad and includes anti-mitochondrial autoantibodies

IPEX syndrome is a congenital disorder of immune regulation caused by mutations in the FOXP3 gene, which is required for the suppressive function of naturally arising CD4 + CD25 + regulatory T cells. In this case series we evaluated serum samples from 12 patients with IPEX syndrome for the presence of common autoantibodies associated with a broad range of autoimmune disorders. We note that 75% of patients (9/12) had 1 or more autoantibodies, an incidence far above the cumulative rate observed in the general population. The range of autoantibodies differed between patients and there was no predominant autoantibody or pattern of autoantibodies present in this cohort. Surprisingly, one patient had high-titer anti-mitochondrial antibodies (AMA) typically associated with primary biliary cirrhosis (PBC) although the patient had no signs of cholestasis. PBC is a well-characterized autoimmune disease that occurs primarily in women and includes the serological hallmarks of serum AMA and elevated IgM which were both present in this patient. PBC is virtually absent in children with the exception of one reported child with interleukin 2 receptor α (CD25) deficiency which is associated with an IPEX-like regulatory T cell dysfunction. Based on the present data and the available literature we suggest a direct role for CD4 + CD25 + regulatory T cells in restraining B cell autoantibody production and that defects in regulatory T cells may be crucial to the development of PBC.

Genomic variants associated with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune hepatobiliary disease characterized by immune-mediated injury of small and medium-sized bile ducts, eventually leading to liver cirrhosis. Several studies have addressed PBC immunopathology, and the data support an immune activation leading to autoantibodies and autoreactive T cells acting against the lipoylated 2-oxoacid dehydrogenase complexes. The causes of the disease remain unknown, but environmental factors and genetic susceptibility both contribute to its onset. Over the past two decades several association studies have addressed the role of genetic polymorphisms in PBC pathogenesis and have reported multiple associations. However, only a few studies had sufficient statistical power, and in most cases results were not independently validated. A genome-wide association study has recently been reported, but this too awaits independent confirmation. The aim of this present work is to critically review the numerous studies dedicated to revealing genetic associations in PBC, and to predict the potential for future studies based on these data.

Experimental evidence on the immunopathogenesis of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease for which an autoimmune pathogenesis is supported by clinical and experimental data, including the presence of autoantibodies and autoreactive T cells. The etiology remains to be determined, yet data suggest that both a susceptible genetic background and unknown environmental factors determine disease onset. Multiple infectious and chemical candidates have been proposed to trigger the disease in a genetically susceptible host, mostly by molecular mimicry. Most recently, several murine models have been reported, including genetically determined models as well as models induced by immunization with xenobiotics and bacteria.

A comprehensive evaluation of serum autoantibodies in primary biliary cirrhosis

In primary biliary cirrhosis (PBC) serum markers other than anti-mitochondrial antibodies (AMA) are promising in terms of disease severity and comorbidities, as well represented by anti-nuclear antibodies (ANA). The aim of the present study was thus to evaluate the prevalence and clinical significance of a large profile of serum autoantibodies in PBC sera. We utilized 69 sera from European patients with PBC (including 20 AMA-negative) and 297 sera from geographically and sex-matched healthy controls. All sera were tested for the presence of ANA and autoantibodies associated with thrombophilia, vasculitis, and gastrointestinal disease. Autoantibodies other than AMA were detected in 53/69 (76%) PBC sera vs. 105/297 (35%) among controls. The prevalence of ANA (targeting dsDNA, Sm, chromatin, ribosomal-P, RNP, SmRNP, SSA, SSB, and centromere) and thrombophilia-associated autoantibodies (i.e. anti-beta2GPI, phosphatydilserine, prothrombin) was common among patients with PBC. When clinical features were compared, the presence of anti-prothrombin IgM was associated with a worse prognosis as represented by a higher Mayo score. We demonstrate an increased prevalence of ANA and thrombophilia-associated autoantibodies in PBC sera and an association between the latter autoantibodies and PBC stage. The role of thrombophilia-associated antibodies will warrant further studies, based in particular on the incidence of portal hypertension at early stages of PBC.

Autoantibody IgG subclasses to recombinant antigens and the role of bacterial stimuli in primary biliary cirrhosis

AIM

Serum antimitochondrial antibody (AMA) of the IgG2 and IgG3 subclasses has been reported to be predominant in patients with primary biliary cirrhosis from developed countries. No data are available as to the significance of AMA subtypes in Japanese primary biliary cirrhosis (PBC) patients who have previously manifested unique serological features, nor it is known whether AMA subclasses are influenced by bacterial stimuli, as suggested by the molecular theory of PBC. We undertook a three-step study to address these questions.

METHODS

First, Japanese PBC sera were tested using the established triple recombinant antigen (pML-MIT3) to find AMA subclass distribution. Second, we used the three recombinant mitochondrial antigens in PBC sera of Japanese and USA patients to explore the ethnic difference. Third, we used CpG oligodeoxynucleotides and a B cell mitogen to challenge ex vivo peripheral leukocytes from indirect immunofluorescence (IIF)-AMA-positive patients with Japanese PBC.

RESULTS

We detected most frequently IgG2-AMA followed by IgG3-AMA, with the latter being more common in IIF-AMA-positive cases, and demonstrated that the IgG3 reactivity against the dominant antigen was significantly higher in PBC sera from the USA. We determined that the bacterial stimulus was superior to the mitogen at inducing a predominant production of IgG2-AMA and CD20+ B cell activation.

CONCLUSION

Our data cumulatively supported the hypothesis that IgG2 AMA subtypes are predominant in PBC and suggest that this might be favored by an innate immune reaction against bacterial particles, such as CpG DNA.