Antibodies to nuclear lamin C in chronic hepatitis delta virus infection

Autoimmune manifestations in viral hepatitis

Infections by the viruses responsible for hepatitis B, C and D are accompanied by a number of immunopathological manifestations. A link between infection and autoimmunity is particularly well documented for the hepatitis C virus. Immunopathological manifestations range from production of autoantibodies to overt autoimmune disease, including thyroiditis and autoimmune hepatitis, and to immune-complex-mediated disorders, including cryoglobulinaemia, glomerulonephritis and vasculitis. Several of these manifestations improve with successful antiviral treatment, directly incriminating the virus in their pathogenesis. Mechanisms considered responsible for hepatitis virus-related immunopathology, including molecular mimicry, impairment of regulatory T cells and activation of B lymphocytes, will be examined in this review.

Autoimmunity and hepatitis C

Hepatitis C is a widespread chronic liver disease leading to cirrhosis and to the complications of portal hypertension. Based on biochemical and clinical features, it is almost indistinguishable from autoimmune hepatitis, which is characterized by the absence of viral infection, and other causes of chronic liver diseases, and represents a classical autoimmune disease with loss of immunological tolerance of liver tissue. Although the differentiation between both diseases is not difficult due the availability of diagnostic viral markers, it is well recognized that not only are autoantibodies present in autoimmune hepatitis frequently detected in hepatitis C, but also that an array of immune-mediated symptoms and diseases occur in patients with chronic hepatitis C. This has prompted research aimed at identifying a link between hepatitis C and autoimmunity, and autoimmune hepatitis in particular. This review focuses on the general immunological mechanisms linking viral infections with autoimmunity and includes the specific features of hepatitis C- and D-associated autoimmunity. Virus infection remains at the center of molecular and cellular research aimed at identifying the forces driving human autoimmunity and autoimmune diseases.

Autoimmunity and viruses

Although viruses are commonly cited as triggers for autoimmune disease, the actual mechanisms by which they initiate autoimmunity are unknown. Molecular mimicry is the most popular hypothesis, and it proposes that viral antigens that share homologies with host antigens generate an immune response that damages host tissue. The viral antigen may not be needed for perpetuation of the disease, and cross-reacting immune responses can involve humoral, cellular, or both types of reactivity. Linear and conformational epitopes may be involved, and foreign antigens do not need to share exact amino acid sequences with self-proteins to activate autoreactive T cells. Bystander effects can enhance the autoimmune process if previously sequestered or cryptic antigens are exposed to the immune system, and superantigens that are produced by the pathogen and are not MHC restricted can result in marked polyclonal activation of CD4 and CD8 T cells. Future studies must differentiate the targets of pathologic immunity and distinguish self-antigens from infectious nonself-antigens. Transgenic animal models of AIH are needed to assess the pathogenicity of the antigenic targets.

Anti-nuclear envelope antibodies: Clinical associations

OBJECTIVES

Characterization of the clinical associations and clinical implications of antibodies reacting with antigens of the nuclear envelope.

METHODS

Description of an illustrative case and a MEDLINE search-assisted literature review of relevant cases.

RESULTS

With indirect immunofluorescence, autoantibodies directed against various antigens of the nuclear envelope stain the nucleus in a ring-like (rim) pattern. Autoantibodies against 5 antigenic components of the nuclear envelope have been described: anti-gp210, p62, lamina, lamina-associated polypeptides, and lamin B receptor. Antibodies to antigens of the nuclear pore complex, such as gp210 and p62, are highly specific (> 95%) for primary biliary cirrhosis and may aid in the serologic diagnosis of this condition, especially in cases in which antimitochondrial antibodies are not detectable. In contrast, antilamin antibodies are not disease-specific but seem to be associated with lupus anticoagulant or anticardiolipin antibodies, antiphospholipid syndrome, thrombocytopenia, autoimmune liver diseases, and arthralgia. High-titered antilamin antibodies help to define a subset of lupus patients with antiphospholipid antibodies who are at a lower risk of developing thrombotic events. In addition, preliminary data suggest that the presence of antilamin antibodies may be helpful in the diagnosis of chronic fatigue syndrome.

CONCLUSIONS

Each of the antibodies reacting with nuclear membrane antigens has its own spectrum of disease associations.

RELEVANCE

Determination of anti-nuclear envelope antibody pattern by indirect immunofluorescence, with subsequent determination of the specific antibody, carries important diagnostic and prognostic implications in various autoimmune conditions.

Review: nuclear lamins--structural proteins with fundamental functions

The nuclear lamina is located between the inner nuclear membrane and the peripheral chromatin. It is composed of both peripheral and integral membrane proteins, including lamins and lamina-associated proteins. Lamins can interact with one another, with lamina-associated proteins, with nuclear scaffold proteins, and with chromatin. Likewise, most of the lamina-associated proteins are likely to interact directly with chromatin. The nuclear lamina is required for proper cell cycle regulation, chromatin organization, DNA replication, cell differentiation, and apoptosis. Mutations in proteins of the nuclear lamina can disrupt these activities and cause genetic diseases. The structure and assembly of the nuclear lamina proteins and their roles in chromatin organization and cell cycle regulation were recently reviewed. In this review, we discuss the roles of the nuclear lamina in DNA replication and apoptosis and analyze how mutations in nuclear lamina proteins might cause genetic diseases.

Acute hepatitis caused by alverine associated with anti-lamin A and C autoantibodies

We report the case of a 67-year-old woman in whom onset and regression of acute hepatitis were closely related to the time of administration and withdrawal of the smooth muscle relaxant alverine. Antinuclear antibodies were positive, and their titer followed the course of hepatitis. They presented a smooth rim-like nuclear immunofluorescence staining pattern. Immunoblot assay showed that they were directed against lamin A and lamin C. This suggests that alverine should be added to the list of drugs known to produce acute hepatitis, and that drug-induced liver injury is a possible cause of antinuclear antibodies specific for lamin A and lamin C.

Clinical associations of anti-lamin autoantibodies

BACKGROUND

The clinical associations of anti-lamin autoantibodies were first described in 1973. Since then a number of individual case reports and two small series have been published. These have suggested an association with connective tissue disorders and autoimmune liver disease.

AIMS

To identify the clinical and laboratory associations of anti-lamin autoantibodies in an Australian population.

METHODS

Retrospective review of routine antinuclear antibody testing between 1990-1994 for characteristics linear staining of nuclear envelope on indirect immunofluorescence on HEp-2 cells with clinical status defined by retrospective review of case records.

RESULTS

Twenty-eight patients were identified and the clinical status of 27 patients defined. Eleven patients had associated IgG anti-cardiolipin antibodies; anti-phospholipid syndrome was present in nine. Seven further patients had liver disease; five had autoimmune liver disease, with associated autoantibodies. The remaining nine patients had a diverse group of diseases. There was no correlation between the titre of the autoantibody and clinical status. An association with anti-cardiolipin antibodies was found although the cause remains obscure.

CONCLUSION

Anti-lamin autoantibodies, as identified by indirect immunofluorescence, are associated with a diverse group of diseases but particularly with anti-phospholipid syndrome and liver disease. Testing for anti-phospholipid antibodies and more specific markers of systemic lupus erythematosus and autoimmune disease, for example anti-dsDNA antibodies, anti-smooth muscle antibodies and anti-mitochondrial antibodies should be pursued when anti-lamin autoantibodies are detected.

Autoimmunity in hepatitis C and D virus infection

A large number of viruses are capable of inducing acute or chronic hepatitis. The syndrome of chronic hepatitis encompasses not only viral but also autoimmune liver diseases. The hepatitis C virus, and recently also the hepatitis D virus have been found to be associated with an array of autoimmune syndromes, diseases and markers of autoimmunity. The relationship of hepatotropic virus infection and the immune system leading to virus-associated autoimmunity, and its distinction from genuine autoimmune disease represents a fascinating field of research. Clinically, the differentiation between autoimmune liver diseases, virus infection and virus-associated autoimmunity is difficult and epidemiological evaluations have not come up with universally applicable and valid classification criteria. However, both autoimmune liver diseases and viral hepatitis can readily be diagnosed and distinguished through precise and molecularly determined immunological testing systems. The overlap of both, virus-associated autoimmunity, is still at the centre of research activities aimed at establishing diagnostic and risk-assessment criteria. Studies of molecular autoantigens and autoepitopes have begun to define the differences of the B-cell response in autoimmune disease and virus-associated autoimmunity. This provides data that may contribute to the safe application of therapeutic strategies as different as immunosuppression and interferon-alpha (IFN-alpha). The present review focuses on the clinical, epidemiological and molecular aspects of these disease entities.

Heterogeneity of liver-kidney microsomal autoantibodies in chronic hepatitis C and D virus infection

BACKGROUND/AIMS

Anti-liver-kidney microsomal (LKM) autoantibodies occur in a proportion of patients with chronic hepatitis C and D infections. Because of different immunofluorescence patterns, antibodies in hepatitis C and D were termed LKM-1 and LKM-3, respectively. The aim of the present study was to evaluate the different specificities of LKM-1 and LKM-3 antibodies.

METHODS

Forty-nine samples of LKM-1 sera and 16 samples of LKM-3 sera were studied for reactivity against rat and human liver microsomal proteins by immunofluorescence, enzyme-linked immunosorbent assay, and Western blot.

RESULTS

Thirty-four percent of the LKM-1 sera reacted with 50-kilodalton cytochrome P4502D6 in Western blot. In addition, a proportion of the sera recognized either a 59- or 70-kilodalton antigen, and 45% of the sera did not react in Western blot. Recently, the major LKM-3 antigen was identified as an autoepitope expressed on uridine diphosphate-glucuronosyltransferases (UGT). Seven LKM-3-positive sera reacted with recombinant rabbit family one UGT. None of the anti-LKM-1-positive hepatitis C sera reacted with UGT. Antibody reactivity against liver microsomal proteins in enzyme-linked immunosorbent assay ended when antigens were pretreated with sodium dodecyl sulfate, confirming that antibodies recognize conformational epitopes.

CONCLUSIONS

LKM-1 antibodies in hepatitis C are more heterogeneous and react with different antigens compared with LKM-3 antibodies in hepatitis D.

Autoantibodies in hepatitis delta

Hepatitis delta virus infection is associated with a wide range of different autoantibodies. The humoral immune response in chronic hepatitis D is directed against the cytoskeleton, the nucleus, the nuclear lamina and the endoplasmic reticulum. Smooth muscle antibodies (SMA), basal cell layer antibodies (BCLA), stellate epithelial cell antibodies (SECA), thymic reticular cell antibodies (TRA), perithymocytic cell antibodies (PTA), and anti-calmodulin antibodies are reactive with constituents of the cytoskeleton. Antinuclear antibodies (ANA) and anti-lamin C antibodies recognize antigens of the nucleus and the nuclear lamina, respectively. Autoantibodies directed against antigens of the endodoplasmic reticulum (LKM) are also common in chronic hepatitis D. Recently, the major molecular target of LKM-3 autoantibodies was described as an epitope on UDP-glucuronosyltransferases of family 1. In view of the important role of UGTs in drug metabolism, LKM-3 autoantibodies represent a new model to study virus induced autoimmunity in man. Future studies should focus on the role of the host immune response and the clinical relevance of these autoantibodies in chronic hepatitis D.

Anti-GOR in hepatitis D: specific association with hepatitis C virus superinfection

A group of 113 patients with chronic hepatitis D was investigated for the presence of anti-GOR and liver kidney microsomal antibodies. Eight patients were anti-GOR positive and also positive for hepatitis C virus-infection. In sera from 16 patients liver-kidney microsomal antibodies were detectable by immunofluorescence. They were classified as LKM-3 due to their fluorescence pattern. Two of the LKM-3-positive sera were also anti-hepatitis C virus and anti-human immunodeficiency virus positive. None of these patients were positive for anti-GOR. Fourteen sera from LKM-3-positive patients reacted in Western blot with a microsomal protein at 55 kDa that differs from the 50-kDa LKM-1 (cytochrome P450IID6) antigen. Our studies demonstrate that hepatitis D virus itself does not induce an autoimmune reaction against the GOR antigen and that autoimmunity to the LKM-3 antigen induced by hepatitis D virus infection does not correlated with anti-GOR. These studies support the specificity of the anti-GOR response for hepatitis C virus infection.

Recognition of uridine diphosphate glucuronosyl transferases by LKM-3 antibodies in chronic hepatitis D

Patients with chronic hepatitis D often have liver-kidney microsomal antibodies type 3 (LKM-3). These antibodies react with several microsomal antigens that have a molecular weight of 55 KDa and an isoelectric point of about 8. We studied the molecular nature of the antigen and, by immunoscreening a human liver cDNA expression library with KM-3 sera, found that uridine diphosphate glucuronosyl transferases (UGT) appeared as candidate antigens. We confirmed the identity of UGT as an antigen by reacting the sera with recombinant rabbit liver UGT proteins. Some sera reacted with rabbit UGT-2 proteins, but UGT-1 proteins were more sensitive and specific in detecting LKM-3 autoantibodies in patient sera. Anti-UGT-1 antibodies were detected in all LKM-3 positive sera from patients with hepatitis D and 1 out of 11 patients with autoimmune hepatitis type 2. Sera from patients who had hepatitis B only did not react with UGT proteins. The UGT proteins are part of the phase II enzymes of drug metabolism and are the first such enzymes to be identified as human autoantigens.

Cell cycle-associated autoantibodies: markers for autoimmunity and probes for molecular cell biology

Antinuclear autoantibodies are useful diagnostic markers for systemic autoimmune diseases and as probes for the molecular cell biology of nuclear proteins. Here, we review a subset of autoantibodies to nuclear and cytoplasmic proteins involved in the cell cycle. We propose a classification of these autoantibodies into S-phase (DNA Synthesis) and M-phase (Mitosis) autoantibodies. S-phase autoantibodies are represented by autoantibodies to PCNA (Proliferating Cell Nuclear Antigen), the auxiliary protein of DNA polymerase delta. M-phase autoantibodies are represented by autoantibodies to mitotic spindle components viz. centrosomes, condensed chromosomes, centromeres, mitotic spindle proper and intercellular bridge. We have included autoantibodies to nuclear lamins as M-phase autoantibodies as lamins play a key role in reversible breakdown and reformation of nuclear membranes during mitosis. The usefulness of these autoantibodies as diagnostic markers in systemic autoimmune disease is tempered by their presence in patients with "atypical" autoimmune diseases and in normal individuals. However, as molecular probes, they have proven to be unique and invaluable tools for shedding new light on the workings of the cell cycle.

L-tryptophan and the eosinophilia-myalgia syndrome: current understanding of the etiology and pathogenesis

The eosinophilia-myalgia syndrome (EMS) is a newly recognized illness that occurred in an epidemic form during the summer of 1989. The illness was characterized in the acute phase by myalgia and eosinophilia, followed in many patients by chronic cutaneous lesions, progressive neuropathy, and myopathy. EMS was associated with ingestion of L-tryptophan, an essential amino acid marketed as a nutritional supplement but widely used as a therapeutic agent. Evidence of abnormal L-tryptophan metabolism has been described in patients with EMS, and most likely reflects increased activity of indoleamine 2,3-dioxygenase, the rate-limiting enzyme of tryptophan metabolism. A contaminant identified in EMS-associated L-tryptophan preparations has been isolated and characterized, but its biologic effects and role as the etiologic agent in EMS remain to be established. Pathologic observations and experimental studies indicate that eosinophils, mononuclear inflammatory cells, and fibroblasts are potential effector cells, and interleukin-5 and transforming growth factor-beta are important mediators in the pathogenesis of the syndrome. Although few new cases of EMS occurred following the withdrawal of L-tryptophan, affected patients continue to manifest late sequelae of the disease, including dermal fibrotic conditions. This tragic outbreak of a newly recognized illness has focused interest on the role of chemical and environmental agents in the pathogenesis of various idiopathic illness characterized by tissue inflammation and fibrosis.

Clinical manifestations in patients with autoantibodies specific for nuclear lamin proteins

IgG antibodies to nuclear lamin proteins have been found in serum samples from 31 patients using immunofluorescence on HEp-2 cells, Western blotting, and enzyme-linked immunosorbent assay, performed against a nuclear lamina preparation from Ehrlich ascites tumor cells. Antilamin antibodies were most prevalent among patients with nonerosive, seronegative polyarthritis, or patients showing serum antiphospholipid reactivity as well. It is possible that anti-lamin antibodies may thus be a marker for a subgroup of polyarthritis patients who have a different prognosis from that of those with seropositive rheumatoid arthritis. The mechanism for the combined occurrence of anti-lamin and antiphospholipid autoantibodies is obscure. Future studies will answer whether these two antibodies represent a distinct antibody profile in patients with antiphospholipid antibody syndrome.

Autoantibodies to nuclear lamin C in the eosinophilia-myalgia syndrome associated with L-tryptophan ingestion

OBJECTIVE

To examine the autoantibodies (antinuclear antibodies [ANA]) present in serum from a patient with eosinophilia-myalgia syndrome (EMS).

METHODS

Sera obtained during the early phase of EMS and following therapy with prednisone were screened by indirect immunofluorescence on HEp-2 cells, and ANA were characterized by immunoblotting on a purified nuclear lamin fraction.

RESULTS

ANA with a ring-like pattern of nuclear staining were identified at high titer by immunofluorescence, and immunoblotting experiments showed them to be directed against lamin C. The antibody titer declined dramatically after discontinuation of L-tryptophan and therapy with prednisone.

CONCLUSION

This is the first characterization of an antigen/autoantibody system associated with EMS. The findings indicate that this EMS-associated autoantibody recognizes epitopes localized in the carboxyterminal region of lamin C. The occurrence of anti-lamin C autoantibodies in one EMS patient expands the spectrum of clinical conditions associated with these antibodies, and provides evidence for an autoimmune response in EMS.