Autoantibodies

Anti-nucleosome autoantibodies as markers for autoimmune hepatitis and their correlation with disease activity

AIM

To assess the prevalence of autoantibodies against nucleosomes (anti-nucleosome Ab) in patients with autoimmune hepatitis (AIH), examine the correlation between anti-nucleosome Ab and disease activity, and evaluate the effectiveness of anti-nucleosome Ab in predicting relapse.

METHODS

We analyzed serum anti-nucleosome Ab levels in 38 patients with AIH by enzyme-linked immunosorbent assay, and assessed their correlation with clinical characteristics.

RESULTS

Anti-nucleosome Ab levels were significantly higher in AIH, but not in patients with chronic hepatitis B (n = 20) or chronic hepatitis C (n = 20), compared to healthy controls (n = 15). The positive prevalence of anti-nucleosome Ab was 71.1% in AIH. Anti-nucleosome Ab levels were significantly lower during remission compared to that during flares within the same patients with AIH. Total bilirubin levels were significantly higher in patients with anti-nucleosome Ab levels of 53.7 U/mL or more compared to those with less than 53.7 U/mL at disease onset. Analysis of the reduction in anti-nucleosome Ab by immunosuppressive therapy in 16 AIH patients revealed that age at disease onset was significantly lower and IgG levels and relapse rates were significantly higher in patients with a reduction rate of less than 35% compared to those with a reduction rate 35% or more. The International Autoimmune Hepatitis Group score and γ-globulin levels were also higher in patients with reduction rates of less than 35% (borderline significance).

CONCLUSION

Anti-nucleosome Ab in AIH patients may be useful markers not only for disease diagnosis, but also for activity assessment and relapse prediction.

Autoantibodies as prognostic markers in autoimmune liver disease

Certain autoantibodies in autoimmune liver disease have prognostic implications that are under-utilized and under-developed. The goals of this review are to indicate progress in characterizing the autoantibodies with prognostic connotations and to indicate the feasibility and importance of discovering other markers. Prime source and review articles in English were selected by a Medline search through 2010. Antibodies to soluble liver antigen, actin, liver cytosol type 1, asialoglycoprotein receptor, chromatin, cyclic citrullinated peptide, and uridine glucuronosyltransferases have been associated with the occurrence, severity, and progression of autoimmune hepatitis, and antibodies to Sp100, gp210, and centromere have had similar implications in primary biliary cirrhosis. Antibodies to soluble liver antigen have shown the most promise in autoimmune hepatitis as they have been associated with severe histological changes, long durations of treatment, relapse after drug withdrawal, and high frequency of liver failure. Antibodies to the nuclear rim pore protein, gp210, have shown the most promise in primary biliary cirrhosis as they have been associated with severe interface hepatitis, lobular inflammation, and progression to liver failure. The major limitations of the autoantibodies have been their lack of standardized assays, low negative predictabilities, and fluctuating levels. Performance parameters will improve as critical pathogenic pathways, comprehensive testing batteries, and standardized assays through international exchange workshops are developed. Progress has been made in identifying the serological markers of prognosis in autoimmune liver disease, and they promise to reflect critical disease mechanisms and enhance patient management.

Nonstandard Antibodies as Prognostic Markers in Autoimmune Hepatitis

BACKGROUND

Antibodies to actin, chromatin, soluble liver antigen/liver pancreas and liver cytosol type 1 have been ascribed prognostic value in autoimmune hepatitis.

AIM

Evaluate the performance parameters of these nonstandard autoantibodies and determine the critical battery for clinical application.

METHODS

All antibodies were tested concurrently by enzyme immunoassay in 106 patients who had reached a treatment outcome. Tests were repeated in 149 serum samples obtained later to assess durability of the findings.

RESULTS

Antibodies to chromatin and soluble liver antigen/liver pancreas were superior to the other markers in predicting relapse. Patients with antibodies to chromatin and/or soluble liver antigen/liver pancreas relapsed more frequently than patients without these markers (100 versus 79%, p < 0.0003). Maximum sensitivity and predictability for relapse required combined testing, and they were 54 and 60%, respectively. Antibody status remained stable in 60% of patients during 127 +/- 9 months of follow-up, and antibodies to soluble liver antigen/liver pancreas were less labile than antibodies to chromatin (frequency of status change, 4 versus 22%). None of the antibodies were associated with treatment failure, death from hepatic failure or requirement for liver transplantation.

CONCLUSIONS

Antibodies to chromatin and soluble liver antigen/liver pancreas are associated with relapse after corticosteroid withdrawal, and they may be useful prognostic markers. Combined testing improves but does not eliminate deficiencies in sensitivity, predictability and durability.

Role of auto-antibodies for the diagnosis of chronic cholestatic liver diseases

Auto-antibodies are an integral part of the diagnostic armentarium in chronic cholestatic liver disorders, such as primary sclerosing cholangitis (PSC), primary biliary cirrhosis (PBC),auto-immune cholangitis, or overlap syndromes among these disorders. However, care should be taken not to overestimate the diagnostic specificity. Auto-antibodies to mitochondrial antigens(AMAs) with reactivity to the E2 subunit of the pyruvate dehydrogenase complex represent the hallmark antibody for the diagnosis of PBC, whereas antinuclear antibodies (ANAs)with low disease specificity are found in up to 50% of these sera. Antibodies that recognize nuclear envelope proteins exert a similarly high diagnostic specificity as AMA in PBC but occur at a rather low prevalence. The role of auto-antibodies is less well-studied for patients with PSC, but there is growing evidence that only antineutrophil cytoplasmic antibodies(ANCAs) are of relevant diagnostic significance. In contrast, auto-antibodies-particularlyAMAs-do not contribute to the diagnosis of auto-immune cholangitis, whereas ANCAs,ANAs, smooth muscle antibodies, and AMAs are of varying significance in PBC-auto-immune hepatitis (AIH) or PSC-AIH overlap syndromes. It has been widely accepted that the course of the auto-antibody serum end point titers are not suited for the clinical management of patients with chronic cholestatic liver disorders. Additionally, auto-antibodies in these disorders usually do not contribute to the immunopathogenesis of the disease.

Autoantibodies in autoimmune liver disease

Autoantibodies indicate an immune reactive state, but in liver disease they lack pathogenicity and disease specificity. Antinuclear antibodies, smooth muscle antibodies, antibodies to liver/kidney microsome type 1, antimitochondrial antibodies, and perinuclear antineutrophil cytoplasmic antibodies constitute the standard serological repertoire that should be assessed in all liver diseases of undetermined cause. Antibodies to soluble liver antigen/liver pancreas, asialoglycoprotein receptor, actin, liver cytosol type 1, nuclear antigens specific to primary biliary cirrhosis, and pore complex antigens constitute an investigational repertoire that promises to have prognostic and diagnostic value. These autoantibodies may emerge as predictors of treatment response and outcome. Antibodies to histones, doubled-stranded DNA, chromatin, and lactoferrin constitute a supplemental repertoire, and they support the immune nature of the liver disease. Final diagnoses and treatment strategies do not depend solely on serological markers. Autoantibodies are floating variables, and their behavior does not correlate closely with disease activity. There are no minimum levels of significant seropositivity, especially in children. Over-interpretation is the major pitfall in the clinical application of the serological results. New autoantibodies will emerge as the search for target antigens and key pathogenic pathways continues.

Autoantibodies in the diagnosis and management of liver disease

Autoantibodies are nonpathogenic manifestations of immune reactivity, and they may occur in acute and chronic liver diseases. Autoantibodies may be consequences rather than causes of the liver injury, and they should be regarded as diagnostic clues rather than etiologic markers. Conventional autoantibodies used in the categorization of autoimmune liver disease are antinuclear antibodies, smooth muscle antibodies, antibodies to liver/kidney microsome type 1, antimitochondrial antibodies, and atypical perinuclear anti-neutrophil cytoplasmic antibodies. Ancillary autoantibodies that enhance diagnostic specificity, have prognostic connotation, or direct treatment are antibodies to endomysium, tissue transglutaminase, histones, doubled-stranded DNA, and actin. Autoantibodies that have an emerging diagnostic and prognostic significance are antibodies to soluble liver antigen/liver pancreas, asialoglycoprotein receptor, liver cytosol type 1, and nuclear pore complex antigens. Autoantibodies of uncertain clinical value that remain under investigation are antibodies to chromatin, lactoferrin, and Saccharomyces cervisiae. Continued recognition and characterization of autoantibodies should improve diagnostic precision, provide prognostic indices, and elucidate target autoantigens. These advances may in turn clarify pathogenic mechanisms, facilitate the development of animal models, and generate novel site-specific therapies.

Antibodies to soluble liver antigen/liver pancreas and HLA risk factors for type 1 autoimmune hepatitis

OBJECTIVE

Antibodies to soluble liver antigen/liver-pancreas are highly specific markers of type 1 autoimmune hepatitis that have been associated with relapse. Our aim was to determine if these antibodies are reflective of a genetic predisposition for recrudescent disease.

METHODS

One hundred forty-four white North American patients were evaluated by an enzyme immunoassay and by Western blot using recombinant soluble liver antigen/liver-pancreas; 122 were assessed for class II human leukocyte antigens (HLAs).

RESULTS

Twenty-two patients (15%) had antibodies to soluble liver antigen/liver-pancreas. These patients were indistinguishable from seronegative patients by clinical, laboratory, and histological features at presentation. Patients with antibodies to soluble liver antigen/liver pancreas had HLA DR3 (79% vs 50%, p = 0.02) more commonly and HLA DR4 less often (16% vs 47%, p = 0.02) than patients with smooth muscle antibodies and/or antinuclear antibodies. Seropositivity was associated with DRB1*0301 and seronegativity was associated with DRB1*0401. Relapse after drug withdrawal occurred in all patients with antibodies to soluble liver antigen/liver-pancreas and at a higher frequency than in patients with conventional antibodies (100% vs 78%, p = 0.05).

CONCLUSIONS

Antibodies to soluble liver antigen/liver pancreas are associated with HLA DR3 and the susceptibility allele, DRB1*0301. Antibodies to soluble liver antigen/liver-pancreas may be surrogate markers of a genetic propensity for recrudescent disease or the target autoantigen. They may be complementary to antinuclear antibodies and smooth muscle antibodies in diagnosis and management.

Current concepts in the diagnosis, pathogenesis, and treatment of autoimmune hepatitis

Autoimmune hepatitis has a global distribution and affects all ages. Genetic factors strongly influence susceptibility, clinical expression, and treatment response. The diagnosis of autoimmune hepatitis has been codified by an international panel. An acute or fulminant presentation is recognized but not a cholestatic form. Subclassifications by predominant autoantibody profile have been proposed, but they lack etiologic and prognostic differences. Autoantibodies continue to be characterized to improve diagnostic specificity, predict outcome, and identify pertinent antigenic targets. Cytosolic enzymes are prime candidates as autoantigens. DRB1*0301 and DRB1*0401 are the susceptibility alleles in Caucasoid Northern Europeans and North Americans, and they also affect clinical expression and treatment outcome. Other autoimmune promoters affecting cytokine production and immunocyte activation may act in synergy with the susceptibility alleles to affect disease behavior. Cell-mediated and antibody-dependent forms of cytotoxicity are probably interactive pathogenic mechanisms, and novel site-specific therapies are feasible because these mechanisms are defined. Potent new immunosuppressive agents are emerging from the transplantation arena, but prednisone alone or in combination with azathioprine remains the mainstay of treatment. Corticosteroid therapy is effective but not ideal.

Autoimmune liver disease. Current standards, future directions

The diagnosis and management of autoimmune hepatitis continues to evolve as new diagnostic tests and new therapies are added to the armamentarium. Also encouraging are the advances in the understanding of the human immune system and its involvement in the origin and course of auto immune diseases in general and in the variants of autoimmune liver disease. Promising changes are expected in the next few years as new medications become available to the practicing hepatologist. New immune tests may allow therapies to be customized to patients, and antiviral therapies may also eventually be used in the management of this autoimmune liver diseases.

Isolation and characterization of cDNA encoding the antigenic protein of the human tRNP(Ser)Sec complex recognized by autoantibodies from patients withtype-1 autoimmune hepatitis

We previously described autoantibodies against a UGA serine tRNA-protein complex (tRNP(Ser)Sec) in patients with type-1 autoimmune hepatitis [1] and now define the specificity and frequency of this autoantibody and the DNA sequence encoding the tRNA(Ser)Sec-associated antigenic protein. The presence of anti-tRNP(Ser)Sec antibodies was highly specific for type-1 autoimmune hepatitis, as 47.5% of patients were positive compared with none of the control subjects. To characterize the antigenic protein(s), we immunoscreened a human cDNA library with anti-tRNP(Ser)Sec-positive sera. Two clones (19 and 13) were isolated. Clone 19 encodes a protein with a predicted molecular mass of 48.8 kD. Clone 13 is a shorter cDNA, almost identical to clone 19, which encodes a 35.9-kD protein. Expression of both cDNAs was accomplished in Escherichia coli as His-tagged recombinant proteins. Antibodies eluted from both purified recombinant proteins were able to immunoprecipitate the tRNA(Ser)Sec from a HeLa S3 cell extract, demonstrating their cross-reactivity with the mammalian antigenic complex. Recent cloning data relating to the target antigen(s) of autoantibodies in autoimmune hepatitis patients that react with a soluble liver antigen (SLA) and a liver-pancreas antigen (LP) have revealed that these two autoantibodies are identical and that the cloned antigen shows 99% amino acid sequence homology with tRNP(Ser)Sec.

Autoimmune cholangitis within the spectrum of autoimmune liver disease

Autoimmune cholangitis is an idiopathic disorder with mixed hepatocellular and cholestatic findings. Our goal was to characterize the disease prospectively by application of uniform diagnostic criteria. Twenty patients were identified and compared with 242 patients with conventional forms of autoimmune liver disease. Patients with autoimmune cholangitis were distinguished from type 1 autoimmune hepatitis (AIH) by lower serum levels of aspartate transaminase (AST), gamma-globulin, and immunoglobulin G; higher serum levels of alkaline phosphatase; and lower frequencies of autoantibodies. They were distinguished from primary biliary cirrhosis (PBC) by higher serum levels of AST and bilirubin, lower serum concentrations of immunoglobulin M, and greater occurrence of autoantibodies. Their female predominance, lower serum alkaline phosphatase levels, higher frequency of autoantibodies, and absence of inflammatory bowel disease differentiated them from primary sclerosing cholangitis (PSC). Laboratory findings ranged widely and did not characterize individual patients. HLA risk factors were similar to those of type 1 AIH and PBC, and different from those of PSC. Treatment responses to corticosteroids or ursodeoxycholic acid were poor. Composite histological patterns resembled mainly PBC or PSC. We conclude that autoimmune cholangitis diagnosed by prospective analysis cannot be assimilated into a single, conventional, diagnostic category. It may represent variant forms of diverse conditions, a transition stage, or a separate entity with varying manifestations.

Behavior and significance of autoantibodies in type 1 autoimmune hepatitis

BACKGROUND/AIM

Smooth muscle antibodies and antinuclear antibodies characterize type 1 autoimmune hepatitis. Our aim was to correlate the appearance and disappearance of these autoantibodies with clinical and histological events.

METHODS

One hundred and seven patients were evaluated successively over 128+/-9 months. Autoantibodies were determined by indirect immunofluorescence during routine follow-up and at key clinical events.

RESULTS

Eighty-one patients (76%) lost one or both of the autoantibodies, and disappearance was associated with improved laboratory and histological features. Autoantibody status, however, was not highly predictive of laboratory (69%) or histological activity (72%). Patients who relapsed were seronegative at the time of drug withdrawal as commonly as patients who sustained remission (29% versus 25%). Only 27 patients (25%) lost their autoantibodies long term. Patients who eventually entered a sustained remission lost their autoantibodies more commonly than those who required retreatment (76% versus 43%, p=0.03). Disappearance of the autoantibodies, however, preceded sustained remission in only 38%. Serum titers at presentation did not distinguish patients with more severe disease or different treatment outcomes.

CONCLUSIONS

Smooth muscle antibodies and antinuclear antibodies commonly disappear and reappear. Their loss is associated with improved laboratory tests and biopsy findings, but disappearance does not predict treatment outcome. Autoantibody titer at presentation and autoantibody behavior during therapy are not accurate indices of disease severity or prognosis.

Drug therapy in the management of type 1 autoimmune hepatitis

Prednisone alone or in combination with azathioprine is the treatment of choice for severe type 1 autoimmune hepatitis. The combination regimen is preferred, especially in the elderly, because of a lower incidence of corticosteroid-related complications. Only patients with sustained severe laboratory abnormalities, bridging necrosis or multilobular necrosis on histological assessment, and/or incapacitating symptoms, have absolute indications for treatment based on controlled clinical trials. The institution of therapy must be individualised in other patients, based mainly on symptoms and disease behaviour. Serum aspartate aminotransferase and gamma-globulin levels are the most useful indices to monitor during therapy. Liver tissue examination is the best method of evaluating completeness of response. Most patients enter remission, but relapse occurs in 50 to 86% after drug withdrawal. Maintenance therapy with low dosages of prednisone or azathioprine can be used long term in patients who have relapsed repeatedly. Inability to achieve remission after 3 years (incomplete response), deterioration during therapy (treatment failure) and drug toxicity are unsatisfactory responses that warrant alternative strategies. Liver transplantation is effective in managing decompensated disease, but recurrence of autoimmune hepatitis after transplantation is possible. Tacrolimus and budesonide are promising new drugs.