Dimitrios P. Bogdanos

Cytochrome P4502D6(193-212): A new immunodominant epitope and target of virus/self cross-reactivity in liver kidney microsomal autoantibody type 1-positive liver disease

Cytochrome P4502D6 (CYP2D6), target of liver kidney microsomal autoantibody type 1 (LKM1), characterizes autoimmune hepatitis type 2 (AIH2) but is also found in patients with chronic hepatitis C virus (HCV) infection. To provide a complete linear epitope B cell map of CYP2D6, we tested peptides spanning the entire sequence of CYP2D6. In addition to confirming previously described antigenic sites, we identified four new epitopes (193–212, 238–257, 268–287, and 478–497). CYP2D6193–212 is immunodominant and was the target of 12 of 13 (93%) patients with AIH2 and 5 of 10 (50%) HCV/LKM1-positive patients. Because LKM1 is present in both AIH2 and a viral infection, we tested whether Abs to CYP2D6193–212 arise through cross-reactive immunity between virus and self. We identified a hexameric sequence “RLLDLA” sharing 5 of 6 aa with “RLLDLS” of HCV2985–2990 and all 6 aa with CMV130–135. Of 17 CYP2D6193–212-reactive sera, 11 (7 AIH and 4 HCV) reacted by ELISA with the HCV homologue, 8 (5 AIH and 3 HCV) with the CMV homologue, and 8 (5 AIH and 3 HCV) showed double reactivity. Autoantibody binding to CYP2D6193–212 was inhibited by preincubation with HCV2977–2996 or CMV121–140. Recombinant HCV-nonstructural protein 5 and CMV-UL98 proteins also inhibited Ab binding to CYP2D6193–212. Affinity-purified CYP2D6193–212-specific Ab inhibited the metabolic activity of CYP2D6. The demonstrated similarity and cross-reactivity between CYP2D6193–212 and two unrelated viruses suggests that multiple exposure to viruses mimicking self may represent an important pathway to the development of autoimmunity.

Pathogenesis of autoimmune hepatitis.

Autoimmune hepatitis is initiated by CD4 T cells that recognize self-antigen. The effector cells differentiate into functional phenotypes according to cytokines in the microenvironment and the nature of the triggering antigen. Hepatocytes can express class II molecules and present antigenic peptides through a bystander mechanism. NKT cells reside in the normal liver but may be involved in liver cell damage possibly through the expression of Fas ligand. Autoantibodies may also participate in the process by complexing with antigen on the hepatocyte membrane surface and by interacting with mononuclear cells with Fc receptors. Molecular mimicry generates cross-reactivities that predispose the immune system to cross-react with self-antigens. Multiple exposures to pathogens with antigenic similarities may prime a cross-reactive subset of T cells in the genetically predisposed host. Autoimmunity against one self-antigen may then spread through molecular mimicry to other homologous self-antigens and may lead to overt autoimmune disease. Anatomically distant tissues may also become involved as autoreactive T cells that had been activated in one organ expand and infiltrate other organs that express similar epitopes.

Multiple Viral/Self Immunological Cross-Reactivity in Liver Kidney Microsomal Antibody Positive Hepatitis C Virus-Infected Patients is Associated with the Possession of HLA B51

Liver Kidney Microsomal autoantibody type 1(LKM1) directed to cytochrome P4502D6 (CYP2D6) characterises autoimmune hepatitis type-2 (AIH-2), but is also found in a proportion of chronic hepatitis C virus (HCV) infected patients, CYP2D6252 – 271 being a major B- cell autoepitope. Molecular mimicry and immunological cross-reactivity between CYP2D6252 – 271, HCV polyprotein and the infected cell protein 4 (ICP4) of herpes simplex virus type 1 (HSV-1) have been suggested as triggers for the induction of LKM1, but reactivity and cross-reactivity to the relevant sequences have not been investigated experimentally. CYP2D6252 – 271 and its viral homologues were constructed and tested by ELISA in the sera of 46 chronically infected HCV patients, 23 of whom were LKM1 positive. Reactivity to the E1 HCV and ICP4 HSV1 mimics was frequently found in HCV infected patients irrespectively of their LKM1 status; viral/self cross-reactivity (as indicated by inhibition studies), however, was present in the only 2 of the 23 LKM1 seropositive HCV patients, who possessed the HLA allotype B51. Our results indicate that in HCV infected patients virus/self cross-reactivity is dependent on a specific immunogenetic background, a finding awaiting confirmation by studies in larger series of patients.

Bacteria and Primary Biliary Cirrhosis

Infectious agents have been postulated to play a pathogenic role in the loss of immunological tolerance and the induction of primary biliary cirrhosis, an immune-mediated cholestatic liver disease characterized by progressive destruction of the small intrahepatic bile ducts and subsequent cirrhosis and liver failure. This review discusses emerging issues implicating infectious agents such as Escherichia coli, mycobacteria, chlamydia, helicobacter species, lactobacilli, Novosphingobium aromaticivorans, and betaretroviruses in the pathogenesis of primary biliary cirrhosis. We also review the immunopathological mechanisms responsible for the induction of the disease with special emphasis on the role of molecular mimicry and microbial/self immunological cross-reactivity.

Susceptibility to thyroid disorders in hepatitis C

BACKGROUND & AIMSnAutoimmune thyroid disorders (AITDs) are reported, especially during interferon treatment, in chronic HCV infection, in which non-organ-specific autoantibodies (NOSAs) are common. We wondered whether seropositivity for NOSA is associated with susceptibility to AITDs.nnnMETHODSnWe evaluated thyroid function and antithyroglobulin and antithyroperoxidase antibodies in 348 Italian patients with chronic hepatitis C (34% NOSA-positive), 196 patients (33% NOSA-positive) of whom received interferon treatment.nnnRESULTSnAt baseline, thyroid disorders were significantly more frequent in liver/kidney microsomal antibody type 1 (LKM1)-positive patients (29% vs 9%, P < .005). Similarly, on interferon therapy de novo autoimmune thyroid markers and/or symptomatic thyroid disorders appeared more often in LKM1-positive patients (50% vs 3%, P < .0001). Both female sex and LKM1 positivity were predictors of AITD, but only the latter remained significant after logistic regression analysis. Cross-reactivity to all 7 linear epitopes encoding homologous amino acid sequences shared by the HCV polyprotein, CYP2D6 (the LKM1 autoantigen), and thyroperoxidase was detected in 86% LKM1-positive HCV patients with clinical thyroid disorders, but in none of the LKM1-positive or negative HCV patients without thyroid disease, and none of an HCV-negative control group comprising subjects with LKM1-positive autoimmune hepatitis or AITD without liver disease ( P < .0001).nnnCONCLUSIONSnPatients receiving interferon therapy for hepatitis C seropositive for LKM1 are susceptible to develop AITDs, in association with treatment. Molecular mimicry and epitope spreading are potential pathogenic mechanisms.

Antibodies to soluble liver antigen and α-enolase in patients with autoimmune hepatitis

BackgroundAntibodies to a cytosolic soluble liver antigen (SLA) are specifically detected in patients with autoimmune hepatitis (AIH). The target of anti-SLA has been identified as a ~50 kDa UGA serine tRNA-associated protein complex (tRNP(Ser)Sec), through the screening of cDNA libraries. A recent report questioned the identity of tRNP(Ser)Sec as the real SLA antigen. The latter study identified α-enolase as a major anti-SLA target, through proteomic analysis.MethodsIn an attempt to explain the observed discrepancy we have investigated reactivity of SLA positive sera against α-enolase and tRNP(Ser)Sec using rat and primate liver homogenate and the recombinant antigens. Thirty-three serum samples, 11 from SLA-positive patients and 22 from SLA negative controls were investigated. SLA antibodies were detected by an inhibition ELISA and confirmed by immunoblot using human liver homogenate. Autoantibody reactivity was further evaluated using preparations of primate and rat liver homogenates. Anti-α-enolase antibody reactivity has been tested by immunoblot using recombinant α-enolase. An affinity purified goat polyclonal anti-α-enolase IgG antibody was used as reference serum sample. Anti-tRNP(Ser)Sec antibody reactivity was detected by ELISA or dot blot using recombinant tRNP(Ser)Sec antigen.Results and DiscussionThe affinity purified IgG antibody directed to human α-enolase gave a band of approximately 48 kDa in both human and rat liver homogenates. A high titre anti-tRNP(Ser)Sec antibody serum gave a single band of ~50 kDa in both liver preparations. All but one anti-SLA antibody positive sera reacted with a ~50 kDa but none immunofixed a 48 kDa band. All anti-SLA antibody positive sera reacted strongly with the recombinant full length tRNP(Ser)Sec protein. None of the anti-SLA negative sera reacted with tRNP(Ser)Sec. Anti-SLA positive, and anti-SLA negative sera reacted equally against recombinant α-enolase by immunoblot. Pre-incubation of anti-SLA positive sera with tRNP(Ser)Sec completely abolished the 50 kDa band. The findings of the present study indicate that α-enolase and tRNP(Ser)Sec are both expressed in primate and rat liver and have a respective MW of 48 and 50 kDa. They also show that anti-tRNP(Ser)Sec – but not anti-α-enolase – correlates with anti-SLA antibody reactivity.ConclusionOur findings indicate that tRNP(Ser)Sec is the most likely target of anti-SLA.

Early systemic sclerosis—opportunities for treatment

Systemic sclerosis (SSc) is characterized by microvasculopathy (Raynaud’s phenomenon and fibrointimal proliferation), presence of autoantibodies and collagen deposition in skin (scleroderma) and internal organs. Microvasculopathy, detected by nailfold capillaroscopy, and disease-specific autoantibodies (anti-topoisomerase I, anti-centromere, anti-RNA polymerase III antibodies) usually appear earlier, even years before scleroderma. At that stage of the disease, immune activation with T cells and B cells promote fibrosis. Diagnosis of SSc has been relied on scleroderma, and by this time, internal organs may have developed fibrosis, a lethal feature with no available treatment. The new EULAR/ACR 2013 criteria for the classification of SSc will help identify SSc patients before fibrosis of internal organs. The early diagnosis of SSc, before the development of fibrosis in internal organs, will allow the introduction of immunosuppressive medications in these patients in a controlled setting (randomized trials). It is anticipated that this approach will change the hitherto grim prognosis of SSc for the better.

Experimental evidence of Migfilin as a new therapeutic target of hepatocellular carcinoma metastasis

Migfilin is a novel cell-matrix adhesion protein known to interact with Vasodilator Stimulated Phosphoprotein (VASP) and be localized both at cell-matrix and cell-cell adhesions. To date there is nothing known about its role in hepatocellular carcinoma (HCC). As matrix is important in metastasis, we aimed to investigate the Migfilin׳s role in HCC metastasis using two human HCC cell lines that differ in their metastatic potential; non-invasive Alexander cells and the highly invasive HepG2 cells. We silenced Migfilin by siRNA and studied its effect on signaling and metastasis-related cellular properties. We show that Migfilin׳s expression is elevated in HepG2 cells and its silencing leads to upregulation of actin reorganization-related proteins, namely phosphor-VASP (Ser157 and Ser239), Fascin-1 and Rho-kinase-1, promoting actin polymerization and inhibiting cell invasion. Phosphor-Akt (Ser473) is decreased contributing to the upregulation of free and phosphor-β-catenin (Ser33/37Thr41) and inducing proliferation. Migfilin elimination upregulates Extracellular Signal-regulated kinase, which increases cell adhesion in HepG2 and reduces invasiveness. This is the first study to reveal that Migfilin inhibition can halt HCC metastasis in vitro, providing the molecular mechanism involved and presenting Migfilin as potential therapeutic target against HCC metastasis.

Overlap syndromes from pediatrics to adulthood

Abstractu2003 Overlap syndromes are autoimmune conditions with mixed immunological, clinical and histological features. The most frequent overlaps are between primary biliary cirrhosis (PBC) and autoimmune hepatitis (AIH), and between AIH and sclerosing cholangitis (SC). True AIH/PBC overlap syndrome is rare and characterized by elevation of transaminases and immunoglobulin G (IgG), positive anti‐smooth muscle antibodies and a liver biopsy showing interface hepatitis as well as changes typical of PBC. These patients respond to immunosuppressive treatment that must be given promptly, to avoid progression to liver failure. The so‐called ‘autoimmune cholangitis’ defines a small group of patients with cholestatic and histological features of PBC but negative for anti‐mitochondrial antibody (AMA) and positive for PBC‐specific anti‐nuclear antibody (ANA). The positivity for ANA in these patients is a consequence of the AMA negativity, since AMA masks ANA on immunofluorescence. These patients’ clinical course and response to treatment resemble that of classical PBC. AIH/ASC overlap syndrome is characterised by elevated levels of IgG and circulating autoantibodies, including ANA, SMA and atypical perinuclear anti‐neutrophil cytoplasmic antibody, in association with cholangiographic changes typical of SC. This condition affects in particular children and young adults and may represent the early stage of adult primary SC. The parenchymal liver inflammation responds satisfactorily to immunosuppression, while the bile duct damage may progress despite treatment.

The role of the Mediterranean diet in hyperuricemia and gout

The effect of diet habits in the induction of hyperuricemia and gout is extensively studied and several nutritional factors exacerbating the disease have been identified. In this review, we discuss the data so far obtained of the beneficial role on controlling hyperuricemia of Mediterranean diet, which is full of mono-unsaturated fatty acids and flavonoids and sort of butter, processed food and red meat. We emphasize that though the published findings are promising the data are limited and more studies are needed.