Measurement of gp210 autoantibodies in sera of patients with primary biliary cirrhosis

Diagnostic and Clinical Value of Specific Autoantibodies against Kelch-like 12 Peptide and Nuclear Envelope Proteins in Patients with Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease characterized by the presence of antimitochondrial and antinuclear antibodies in patients’ serum. Here, we analyzed the reactivity of autoantibodies against a novel autoantigen, kelch-like 12 (KLHL12) protein, in a cohort of 138 PBC and 90 non-PBC patients. Additionally, we compared the reactivity of KLHL12 with antinuclear envelope antibodies: anti-gp210, anti-p62, and anti-LBR. Commercially available kits and an ‘in-house’ ELISA were used in the studies. Antinuclear envelope antibodies were detected in 65% of PBC patients and the presence of these antibodies was observed more frequently in patients diagnosed with later stages (III/IV) of PBC, according to Ludwig’s classification (p < 0.05) and were found to correlate with a higher concentration of bilirubin. Overall, anti-KLHL12 antibodies were found more frequently in PBC patients than in non-PBC controls (p < 0.001). Anti-KLHL12 antibodies were detected in 36% of the tested PBC cohort, including PBC patients negative for antimitochondrial antibodies. Presence of anti-KLHL12 was also associated with a higher concentration of bilirubin and correlated with fibrosis (p < 0.05). Anti-KLHL12 antibodies were detected in 30% of PBC individuals positive for antinuclear envelope antibodies, while anti-KLHL12 and antinuclear envelope antibodies were found in 17% of all PBC cases. Concluding, our data confirm that antibodies against the KLHL12 protein are highly specific for PBC and when used in combination with other markers, may significantly increase the diagnosis of PBC.

Increased sensitivity of gp210 autoantibody detection using a newly designed gp210 antigen

OBJECTIVES

The detection of autoantibody to glycoprotein 210 (gp210 Ab) against a 15 amino-acid peptide epitope by enzyme-linked immunosorbent assay (ELISA) has been widely used in the diagnosis of primary biliary cholangitis (PBC). However, this small peptide antigen presents spatial limitations for antibody access, which reduces the sensitivity of autoantibody detection. A recombinant gp210 antigen was constructed for increased sensitivity in antibody detection is described here.

METHODS

The gp210 C terminal 18 amino acid coding sequence was ligated to the modified C-terminal 108 amino acid coding sequence of human serum albumin (mHSA108) and produced as a recombinant gp210 antigen mHSA108-gp210-C18. Measurements of gp210 Ab using the gp210 C-terminal 25 amino acid peptide (gp210-C25) and mHSA108-gp210-C18 by in-house ELISA were compared. ELISAs with mHSA108-gp210-C18 and commercial INOVA kit for gp210 Ab detection were also compared in PBC patients and healthy controls. The correlation between the two assays was analyzed and their efficiency in diagnosing was compared.

RESULTS

Of 86 PBC samples, 35 (40.70%) and 44 (52.33%) positive samples were detected for anti-gp210 Ab using gp210-C25 and mHSA108-gp210-C18, respectively. Of 252 samples from PBC, 114 (45.24%) were positive for mHSA108-gp210-C18 ELISA whereas 94 (37.3%) for commercial ELISA (INOVA). All positive samples detected with commercial ELISA kit were also tested positive in mHSA108-gp210-C18 ELISA. Among 374 patients with other autoimmune diseases, anti-gp210 Ab were detected by mHSA108-gp210-C18 ELISA in 0.95% systemic lupus erythematosus (SLE) patients (2/210), 13.04% rheumatoid arthritis (RA) patients (13/97), and 1.47% of Sjögren's Syndrome (SS) patients (1/67).

CONCLUSIONS

Compared to the gp210 peptide antigen, the sensitivity of the ELISA system using mHSA108-gp210-C18 antigen was improved. The novel gp210 antigen could be useful for screening patients known to be at increased risk of developing PBC.

Analysis of Autoantibodies against Promyelocytic Leukemia Nuclear Body Components and Biochemical Parameters in Sera of Patients with Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease characterized by immune-mediated destruction of intrahepatic bile ducts and the presence of specific antibodies. The aim of the study was to examine the diagnostic significance of antibodies against promyelocytic leukemia nuclear body (PML NB) components such as Sp100, Sp140, and PML in a cohort of PBC patients and compare the results with biochemical and histological parameters. Serum samples were collected from 93 PBC patients. Anti-Sp100 and anti-PML antibodies were assessed using commercially available kits, anti-Sp140 using developed “in-house” ELISA test. Anti-Sp140, anti-Sp100, and anti-PML antibodies were present in 25 (27%), 37 (40%), and 29 (31%) PBC patients, respectively. Anti-PML NB positive patients also showed increased concentration of bilirubin and alkaline phosphatase (p < 0.05). In the group with the presence of at least two types of these antibodies, more frequent deaths or transplantations were observed. A correlation between the presence of antibodies and histological grade (OR = 2.55 p = 0.039) was established. Patients with bilirubin > 1.1 mg/dL at the time of diagnosis had a significantly shorter time of survival than patients with bilirubin ≤ 1.1 mg/dL (HR 5.7; 95% C.I., 2.7, 12.3; p < 0.001). Our data confirm very high specificity of anti-PML NB antibodies, which can expand the laboratory diagnostic capabilities of PBC. We found an association between positive reactivity of autoantibodies directed against components of PML nuclear bodies and higher concentrations of bilirubin and alkaline phosphatase, but the main prognostic marker of survival remains serum bilirubin.

Detection of Autoantibodies Against Nucleoporin p62 in Sera of Patients With Primary Biliary Cholangitis

BACKGROUND

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by specific autoantibodies. We evaluated the prevalence of autoantibodies against nucleoporin p62 (anti-p62) in PBC patients' sera to determine whether it can be a marker for PBC, in comparison with other immunological and biochemical parameters. We validated the performance of our in-house ELISA technique.

METHODS

Serum samples were collected from 135 PBC patients. Thirty patients with primary sclerosing cholangitis (PSC) and 30 with autoimmune hepatitis (AIH) were included as pathological controls, and 40 healthy blood donors served as healthy controls. The presence of anti-p62 was determined by an in-house ELISA using a recombinant protein. We calculated the sensitivity, specificity, positive and negative predictive values (PPV and NPV), and positive and negative likelihood ratio (LR+ and LR-) of our in-house ELISA for diagnosing PBC based on anti-p62. Findings were correlated with biochemical data and survival.

RESULTS

Anti-p62 was detected in 32 PBC patients (23.7%). Specificity and PPV of anti-p62 for PBC were 99% and 97%, respectively. The difference between proportions of anti-p62-positive patients and controls was 0.23 (95% confidence interval [CI]: 0.03-0.40; P<0.0001); LR+ and LR- were 23.7 and 0.77, respectively. The presence of anti-p62 was associated with higher levels of bilirubin and alkaline phosphatase (P<0.001). The odds ratio for survival was 2.44 (95% CI: 0.87-6.87; P=0.091).

CONCLUSIONS

Anti-p62 may be regarded as a significant serological marker of PBC.

Meta-analysis assessment of GP210 and SP100 for the diagnosis of primary biliary cirrhosis

PURPOSE

To conduct a systematic review of included studies assessing the association of GP210 and SP100 with the risk of primary biliary cirrhosis (PBC) using meta-analysis.

METHODS

Five databases, the Cochrane Library, MEDLINE, VIP, CNKI, WANFANG were used to detect the role of GP210 and SP100 in diagnosis of PBC. Approximately 13,000 participants from several countries were included in this analysis. Meta-DiSc statistical software was used for analysis.

RESULTS

25 studies on GP210 and 21 studies on SP100 were included in the meta-analysis. The DOR, sensitivity, specificity of GP210 in diagnosis of PBC were 24.854 (11.957-51.660), 0.272 (0.257-0.288), 0.985 (0.982-0.988), respectively, and they were 9.133 (4.739-17.600), 0.231 (0.213-0.249), 0.977 (0.973-0.981) for SP100.

CONCLUSION

Our meta-analysis indicated both GP210 and SP100 had high specificity but low sensitivity in diagnosis of PBC.

Diagnostic and predictive significance of autoantibody profiles in autoimmune liver disease

Autoimmune liver disease (AILD) is a chronic inflammatory disease presumably induced by a disorder of immune homeostasis within the liver, which can lead to damage to or loss of the hepatic parenchyma or bile duct epithelia. Indirect immunofluorescence and antibody specificity assays are important tools for the diagnosis of AILD. Over the last decade, there have been an increasing number of newly characterized target antigens for autoantibodies in AILD. Autoantibodies, as biomarkers, are used not only for disease diagnosis, but also for monitoring disease activity and progression and predicting prognosis and treatment responses.

Diagnostic value of anti-gp210 antibodies in primary biliary cirrhosis: a case-based review

Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterised by chronic cholestasis usually associated with antimitochondrial antibodies. Moreover, several types of antinuclear antibodies have been associated with primary biliary cirrhosis. We describe an 83-year-old man, in whom the exploration of a chronic cholestasis led to the diagnosis of primary biliary cirrhosis despite negative antimitochondrial antibodies, regarding the presence of anti-gp210 antibodies. Found in 25% of patients, these antinuclear antibodies must be sought before a strong suspicion of primary biliary cirrhosis with antimitochondrial antibodies negative, as they are highly specific of the disease. They are generally associated with a more aggressive form of PBC.

Identification of new autoantigens for primary biliary cirrhosis using human proteome microarrays

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease of unknown etiology and is considered to be an autoimmune disease. Autoantibodies are important tools for accurate diagnosis of PBC. Here, we employed serum profiling analysis using a human proteome microarray composed of about 17,000 full-length unique proteins and identified 23 proteins that correlated with PBC. To validate these results, we fabricated a PBC-focused microarray with 21 of these newly identified candidates and nine additional known PBC antigens. By screening the PBC microarrays with additional cohorts of 191 PBC patients and 321 controls (43 autoimmune hepatitis, 55 hepatitis B virus, 31 hepatitis C virus, 48 rheumatoid arthritis, 45 systematic lupus erythematosus, 49 systemic sclerosis, and 50 healthy), six proteins were confirmed as novel PBC autoantigens with high sensitivities and specificities, including hexokinase-1 (isoforms I and II), Kelch-like protein 7, Kelch-like protein 12, zinc finger and BTB domain-containing protein 2, and eukaryotic translation initiation factor 2C, subunit 1. To facilitate clinical diagnosis, we developed ELISA for Kelch-like protein 12 and zinc finger and BTB domain-containing protein 2 and tested large cohorts (297 PBC and 637 control sera) to confirm the sensitivities and specificities observed in the microarray-based assays. In conclusion, our research showed that a strategy using high content protein microarray combined with a smaller but more focused protein microarray can effectively identify and validate novel PBC-specific autoantigens and has the capacity to be translated to clinical diagnosis by means of an ELISA-based method.

Autoantibodies to GW bodies and other autoantigens in primary biliary cirrhosis

Autoantibodies to intracellular targets in mitochondria and nuclei are serological hallmarks of primary biliary cirrhosis (PBC). One of the most recently identified cellular targets of PBC autoantibodies is a novel cytoplasmic structure referred to as GW bodies [GWB, G (glycine) W (tryptophan)-containing bodies (GWB)]. GWB are indentified as discrete cytoplasmic domains that are involved in mRNA processing via the RNA interference (RNAi) pathway. Key components of GWB include the proteins GW182, Ago2, RNA-associated protein 55 (RAP55) and Ge-1/Hedls. The primary objective was to study the frequency and clinical association of antibodies directed to GWB components, in 109 PBC patients. Autoantibodies to mitochondrial antigen-pyruvate dehydrogenase complex (M2), branched-chain 2-oxo-acid dehydrogenase complex and 2-oxo glutarate dehydrogenase complex (3E-BPO), gp210, sp100, promyelocytic leukaemia cell antigen (PML) and liver kidney microsomal-1 antigen (LKM-1) were detected by a line immunoassay and antibodies to GWB (GW182, RAP55, Ge-1, GW2, GW3) and glutamate receptor interacting protein (GRIP)-associated protein-1 (GRASP-1), by an addressable laser bead immunoassay (ALBIA). The most common GWB autoantigen targets were: RAP55-28%, GW182-12%, GW2-2% and antibodies to GRASP-1-17%. By comparison, the frequency of reactivity to established PBC autoantigens was: gp210, 27%; sp100, 27% and PML, 17%. None of the autoantibodies were associated with differences in Mayo risk score or liver decompensation. This study is the first study to show that antibodies to RAP55, GW182 and GRASP-1 are the most common GWB targets in PBC.

Primary biliary cirrhosis: What do autoantibodies tell us?

Primary biliary cirrhosis (PBC) is a chronic, progressive, cholestatic, organ-specific autoimmune disease of unknown etiology. It predominantly affects middle-aged women, and is characterized by autoimmune-mediated destruction of small- and medium-size intrahepatic bile ducts, portal inflammation and progressive scarring, which without proper treatment can ultimately lead to fibrosis and hepatic failure. Serum autoantibodies are crucial tools for differential diagnosis of PBC. While it is currently accepted that antimitochondrial antibodies are the most important serological markers of PBC, during the last five decades more than sixty autoantibodies have been explored in these patients, some of which had previously been thought to be specific for other autoimmune diseases.

Differential detection of nuclear envelope autoantibodies in primary biliary cirrhosis using routine and alternative methods

Background

Detection of autoantibodies giving nuclear rim pattern by immunofluorescence (anti-nuclear envelope antibodies - ANEA) in sera from patients with primary biliary cirrhosis (PBC) is a useful tool for the diagnosis and prognosis of the disease. Differences in the prevalence of ANEA in PBC sera so far reported have been attributed to the methodology used for the detection as well as to ethnic/geographical variations. Therefore, we evaluated the prevalence of ANEA in sera of Greek patients with PBC by using methods widely used by clinical laboratories and a combination of techniques and materials.

Methods

We screened 103 sera by immunoblotting on nuclear envelopes and indirect immunofluorescence (IIF) using cells and purified nuclei. Reactivities against specific autoantigens were assessed using purified proteins, ELISA, immunoprecipitation and mass spectrometry.

Results

We found higher prevalence of ANEA when sera were assayed by IIF on purified nuclei or cultured cells (50%) compared to Hep2 commercially available slides (15%). Anti-gp210 antibodies were identified in 22.3% and 33% of sera using ELISA for the C-terminal of gp210 or both ELISA and immunoprecipitation, respectively. Immunoblotting on nuclear envelopes revealed that immunoreactivity for the 210 kDa zone is related to anti-gp210 antibodies (p < 0.0001). Moreover, we found that sera had antibodies for lamins A (6.8%), B (1%) and C (1%) and LBR (8.7%), whereas none at all had detectable anti-p62 antibodies.

Conclusions

The prevalence of ANEA or anti-gp210 antibodies is under-estimated in PBC sera which are analyzed by conventional commercially available IIF or ELISA, respectively. Therefore, new substrates for IIF and ELISA should be included by clinical laboratories in the analysis of ANEA in autoimmune sera.

Autoimmune liver serology: Current diagnostic and clinical challenges

Liver-related autoantibodies are crucial for the correct diagnosis and classification of autoimmune liver diseases (AiLD), namely autoimmune hepatitis types 1 and 2 (AIH-1 and 2), primary biliary cirrhosis (PBC), and the sclerosing cholangitis variants in adults and children. AIH-1 is specified by anti-nuclear antibody (ANA) and smooth muscle antibody (SMA). AIH-2 is specified by antibody to liver kidney microsomal antigen type-1 (anti-LKM1) and anti-liver cytosol type 1 (anti-LC1). SMA, ANA and anti-LKM antibodies can be present in de-novo AIH following liver transplantation. PBC is specified by antimitochondrial antibodies (AMA) reacting with enzymes of the 2-oxo-acid dehydrogenase complexes (chiefly pyruvate dehydrogenase complex E2 subunit) and disease-specific ANA mainly reacting with nuclear pore gp210 and nuclear body sp100. Sclerosing cholangitis presents as at least two variants, first the classical primary sclerosing cholangitis (PSC) mostly affecting adult men wherein the only (and non-specific) reactivity is an atypical perinuclear antineutrophil cytoplasmic antibody (p-ANCA), also termed perinuclear anti-neutrophil nuclear antibodies (p-ANNA) and second the childhood disease called autoimmune sclerosing cholangitis (ASC) with serological features resembling those of type 1 AIH. Liver diagnostic serology is a fast-expanding area of investigation as new purified and recombinant autoantigens, and automated technologies such as ELISAs and bead assays, become available to complement (or even compete with) traditional immunofluorescence procedures. We survey for the first time global trends in quality assurance impacting as it does on (1) manufacturers/purveyors of kits and reagents, (2) diagnostic service laboratories that fulfill clinicians’ requirements, and (3) the end-user, the physician providing patient care, who must properly interpret test results in the overall clinical context.