Antibodies to the cytoskeleton components and other autoantibodies in inflammatory bowel disease

Prevalence of antinuclear antibodies in inflammatory bowel disease and seroconversion after biological therapy

BACKGROUND

Estimates of detectable antinuclear antibodies (ANA) prevalence vary widely, from 6% in healthy populations to 50-80% in patients with autoimmune disease. However, there is a lack of evidence about the overall prevalence in inflammatory bowel disease (IBD) and ANA seroconversion after the beginning of biological therapy.

OBJECTIVES

The aim of the study was to investigate the overall prevalence of ANA in IBD patients, their relationship with different treatments, clinical outcomes and the seroconversion rate of ANA in patients treated with biological therapy.

METHODS

Ambispective observational study including all consecutive IBD patients was carried out. Information about the presence of ANA, disease phenotype, duration, activity, complications, and past and current treatments were transversally collected. Retrospectively, in patients with detectable ANA, data regarding previous ANA detection and the diagnosis of lupus-like syndrome (LLS) was gathered.

RESULTS

A total of 879 IBD patients were included. We observed a detectable ANA prevalence of 13.6%. The presence of ANA was frequently associated with biological therapy (36/118) and decreased when immunomodulators were combined to this therapy (7/32). Of 78 patients with ANA prior to the beginning of biological therapy, a seroconversion rate of 28.8% was observed after a mean of 3.14 years. Only 1 patient suffered LLS.

CONCLUSION

Our study showed a prevalence of detectable ANA higher than the expected in healthy population. The presence of ANA was lower when immunomodulator therapy is associated. The ANA seroconversion rate is relevant after the initiation of biological treatment nevertheless, the risk of LLS appeared to be marginal.

Antibodies in cerebral cavernous malformations react with cytoskeleton autoantigens in the lesional milieu

Previous studies have reported robust inflammatory cell infiltration, synthesis of IgG, B-cell clonal expansion, deposition of immune complexes and complement within cerebral cavernous malformation (CCM) lesions. B-cell depletion has also been shown to reduce the maturation of CCM in murine models. We hypothesize that antigen(s) within the lesional milieu perpetuate the pathogenetic immune responses in CCMs. This study aims to identify those putative antigen(s) using monoclonal antibodies (mAbs) derived from plasma cells found in surgically removed human CCM lesions. We produced human mAbs from laser capture micro-dissected plasma cells from four CCM patients, and also germline-reverted versions. CCM mAbs were assayed using immunofluorescence on central nervous system (CNS) tissues and immunocytochemistry on human primary cell lines. Antigen characterization was performed using a combination of confocal microscopy, immunoprecipitation and mass spectrometry. Affinity was determined by enzyme-linked immunosorbent assay, and specificity by multi-color confocal microscopy and quantitative co-localization. CCM mAbs bound CNS tissue, especially endothelial cells and astrocytes. Non-muscle myosin heavy chain IIA (NMMHCIIA), vimentin and tubulin are three cytoskeleton proteins that were commonly targeted. Selection of cytoskeleton proteins by plasma cells was supported by a high frequency of immunoglobulin variable region somatic hypermutations, high affinity and selectivity of mAbs in their affinity matured forms, and profoundly reduced affinity and selectivity in the germline reverted forms. Antibodies produced by plasma cells in CCM lesions commonly target cytoplasmic and cytoskeletal autoantigens including NMMHCIIA, vimentin and tubulin that are abundant in endothelial cells and astrocytes. Binding to, and selection on autoantigen(s) in the lesional milieu likely perpetuates the pathogenetic immune response in CCMs. Blocking this in situ autoimmune response may yield a novel treatment for CCM.

Relationship between Smooth Muscle and Cytoskeleton Antibodies in Neuroblastoma

The previously reported high prevalence of smooth muscle antibodies in neuroblastoma has been found to be associated with a similarly elevated prevalence of anti-cytoskeleton antibodies. The most relevant finding is related to anti-microfilaments (anti-actin) and anti-microtubules antibodies, which were detected with highly significantly different prevalences when compared with a disease control group (p < 0.001 and p < 0.000001, respectively). The correspondence between smooth muscle antibodies and anti-cytoskeleton antibodies is incomplete, and it is more relevant for anti-microfilaments. It is concluded that antigen specificities of smooth muscle antibodies in neuroblastoma are as complex as documented in other diseases. Possible pathogenetic and clinical implications emerging from these data are discussed.

Current concepts and future directions for the assessment of autoantibodies to cellular antigens referred to as anti-nuclear antibodies

The detection of autoantibodies that target intracellular antigens, commonly termed anti-nuclear antibodies (ANA), is a serological hallmark in the diagnosis of systemic autoimmune rheumatic diseases (SARD). Different methods are available for detection of ANA and all bearing their own advantages and limitations. Most laboratories use the indirect immunofluorescence (IIF) assay based on HEp-2 cell substrates. Due to the subjectivity of this diagnostic platform, automated digital reading systems have been developed during the last decade. In addition, solid phase immunoassays using well characterized antigens have gained widespread adoption in high throughput laboratories due to their ease of use and open automation. Despite all the advances in the field of ANA detection and its contribution to the diagnosis of SARD, significant challenges persist. This review provides a comprehensive overview of the current status on ANA testing including automated IIF reading systems and solid phase assays and suggests an approach to interpretation of results and discusses meeting the problems of assay standardization and other persistent challenges.

IgA anti-actin antibodies in children with celiac disease: comparison of immunofluorescence with Elisa assay in predicting severe intestinal damage

BACKGROUND

Previous studies have demonstrated that the presence of serum IgA antibodies against actin filaments (AAA) in patients with celiac disease (CD) is strongly associated with mucosal damage and severe degrees of villous atrophy.The aims of the present study were (1) to verify the effectiveness of IgA-AAA in newly diagnosed CD patients in a clinical setting (2) to compare the immunofluorescence assay with ELISA assay; (3) to compare the correlation of our IgA anti-tissue transglutaminase antibodies (tTG-Ab) class with mucosal intestinal lesions.

METHODS

90 patients underwent endoscopy and multiple biopsies for suspected CD on the basis of symptoms, in presence of positive tTG-Ab tests. Twenty biopsied and 25 not-biopsied subjects with negative tTG-Ab were tested as control groups. IgA-AAA assays were performed by indirect immunofluorescence using rat epithelial intestinal cells, and by ELISA with a commercial kit. tTG-Ab assay was a radio-binding assay. Intestinal specimens were collected by upper endoscopy and the histological study was done according to the Marsh's classification modified by Oberhuber (M/O). Auto-antibodies assays and histological evaluation have been performed blindly by skilled operators.

RESULTS

CD diagnosis was confirmed in 82 patients (type I M/O in 2 patients, IIIA in 18 patients, IIIB in 29 patients and IIIC in 33 patients). Two patients with type 1 lesion in presence of positive tTG-Ab and abdominal complaints, started a gluten free diet. The rate of IgA-AAA positivity (sensitivity) by IFI and ELISA in histologically proven celiac disease patients, were 5.5% and 25% patients in IIIA, 27.5% and 34.4% patients in IIIB, 78.8% and 75% in IIIC patients, respectively.Patients with normal or nearly normal mucosa, regardless of tTG-Ab status, presented negative IgA-AAA IFI assay. On the other hand, 1 patient with normal mucosa but positive tTG-Ab, also presented positive IgA-AAA ELISA. All healthy non biopsied controls had negative IgA-AAA. tTG-Ab serum concentration was significantly correlated with more severe intestinal lesion (IIIB, IIIC M/O).

CONCLUSIONS

IgA-AAA may be undetectable in presence of severe mucosal damage. Histology is still necessary to diagnose celiac disease and IgA-AAA cannot be included in usual screening tests, because it has little to offer if compared to the well-established tTG-Ab.IgA-AAA could be an adjunctive, very useful tool to support the diagnosis of CD in case of suboptimal histology, when the biopsy is to be avoided for clinical reasons, or in case of negative parents' consensus.

Antinuclear antibodies: a marker associated with steroid dependence in patients with ulcerative colitis

BACKGROUND

The autoimmune phenomena and the autoantibody profile have acquired great importance in ulcerative colitis (UC). Few studies have explored antinuclear antibodies (ANAs) prevalence, but not its association with steroid dependence. We hypothesized that ANAs could be a factor associated to steroid dependence.

METHODS

Ninety-seven consecutive patients with UC were included. ANA titers and staining patterns were determined by indirect immunofluorescence. Gender, age, follow-up time, C-reactive protein (CRP), disease extent, Mayo Score Activity Index, extraintestinal manifestations, and steroid dependence were analyzed in univariate and multivariate models.

RESULTS

Ninety-seven patients were included and 49 (50.5%) were females; mean age was 41.7 +/- 22.2 years. Positivity for ANAs was encountered in 52 (53.5%) patients, and none for anti-dsDNA. The prevalence of ANAs was higher in steroid-dependent than in nonsteroid-dependent patients (77.8% versus 48.1%, P = 0.020; odds ratio [OR] = 3.8, 95% confidence interval [CI] 1.1-12.5), and in those with uveitis (100% versus 51.1%; P = 0.040) or pyoderma gangrenosum (100% versus 51.6%; P = 0.078). No association was observed with gender, age, CRP, disease extent, and Mayo Score Activity Index. The multiple regression analysis model showed an association between steroid dependence and ANAs (P = 0.033, OR = 3.9, 95% CI 1.4-14.9).

CONCLUSIONS

ANAs are associated with steroid dependence in UC patients. Further studies are required to determine the role of ANAs as serological markers for prediction of steroid dependence in order to perform early therapeutic interventions with biological agents.

Toxicity of infliximab in the course of treatment of Crohn's disease

Infliximab is a monoclonal antibody directed against the pro-inflammatory mediator TNF-alpha, which was approved in the US in 1998 for treatment-resistant Crohn's disease. Since that time, the indications have dramatically expanded to include rheumatoid arthritis, ankylosing spondylitis, psoriasis and most recently, active ulcerative colitis. Although the safety profile in the initial studies was quite favourable, subsequent studies have shown that a small percentage of patients reported severe side effects, including pneumonia, tuberculosis, lymphoma, drug-induced lupus and hepatotoxicity. Although these complications are rare, it is important to properly screen patients for predisposing conditions before beginning treatment. Furthermore, concurrent use of other immunosuppresive agents, such as 6-mercaptopurine, may reduce the incidence of less serious side effects, such as arthralgias, myopathies and other antibody-associated diseases. Since its approval, infliximab has revolutionised the treatment of Crohn's disease and has shown benefit in a variety of other inflammatory conditions, but significant toxicities can occur that necessitate thorough screening protocols and periodic clinical evaluation.

Anti-actin IgA antibodies in severe coeliac disease

Anti-actin IgA antibodies have been found in sera of coeliacs. Our aim was to define the prevalence and clinical significance of anti-actin IgA in coeliacs before and after gluten withdrawal. One hundred and two biopsy-proven coeliacs, 95 disease controls and 50 blood donors were studied. Anti-actin IgA were evaluated by different methods: (a) antimicrofilament positivity on HEp-2 cells and on cultured fibroblasts by immunofluorescence; (b) anti-actin positivity by enzyme-linked immuosorbent assay (ELISA); and (c) presence of the tubular/glomerular pattern of anti-smooth muscle antibodies on rat kidney sections by immunofluorescence. Antimicrofilament IgA were present in 27% of coeliacs and in none of the controls. Antimicrofilament antibodies were found in 25 of 54 (46%) coeliacs with severe villous atrophy and in three of 48 (6%) with mild damage (P < 0.0001). In the 20 patients tested, antimicrofilaments IgA disappeared after gluten withdrawal in accordance with histological recovery. Our study shows a significant correlation between antimicrofilament IgA and the severity of intestinal damage in untreated coeliacs. The disappearance of antimicrofilament IgA after gluten withdrawal predicts the normalization of intestinal mucosa and could be considered a useful tool in the follow-up of severe coeliac disease.

Regulation of gene expression in inflammatory bowel disease and correlation with IBD drugs: screening by DNA microarrays

Potential biomarkers for Crohn's disease (CD) and ulcerative colitis (UC) were identified from two sets of full thickness pathologic samples utilizing DermArray and PharmArray DNA microarrays relative to uninvolved (Un) colon or normal colon. Seven of the over-expressed genes were verified using quantitative RT-PCR (i.e., TMPT, FABP1, IFI27, LCN2, COL11A2, HXB, and metallothionein). By correlating gene expression profiles between inflammatory bowel disease (IBD) tissue samples and IBD drug-treated cell cultures it might be possible to identify new candidate molecular target genes for IBD therapy and drug discovery. Potential biomarkers for CaCo2 cell cultures, which are routinely used as a GI tract surrogate model for in vitro pharmacokinetic studies, treated with azathioprine, 5-aminosalicylic acid, metronidazole, and prednisone were also identified from another experiment. Metallothionein mRNA expression was found to be down-regulated in azathioprine-treated CaCo2 cells, and was coincidentally up-regulated in the CD sample, thus resulting in an anti-correlation. These results suggest that this new screening methodology is feasible, that metallothioneins might be biomarkers for azathioprine therapy in vivo in CD, and that azathioprine might mechanistically down-regulate metallothionein gene expression. Correlations were also observed between IBD samples and either metronidazole- or 5-aminosalicylic acid-treated CaCo2 cells. Similar comparisons of disease tissue samples in vivo vs drug-treated cell cultures in vitro might reveal new mechanistic insights concerning established or experimental drug therapies. This affordable in vitro methodology is promising for expanded studies of IBD and other diseases.

Development of antinuclear antibodies and its clinical impact in patients with Crohn's disease treated with chimeric monoclonal anti-TNFalpha antibodies (infliximab)

BACKGROUND

Although the efficacy of infliximab in Crohn's disease (CD) has been demonstrated, its safety profile has yet to be established. Autoimmune adverse events such as human anti-chimeric antibodies and the development of antinuclear antibodies (ANAs) have been notified, but the true incidence and clinical relevance of the latter is still unknown.

OBJECTIVE

To evaluate the changes in ANA status in CD patients treated with infliximab and the clinical evolution of those who are ANA positive.

METHODS

The ANA status of 36 CD patients treated with infliximab was determined at baseline and 6 weeks after the initial infliximab infusion. Patients were followed up monthly. In the case of infliximab re-treatment, ANA status was again evaluated. Twenty-eight patients (78%) were treated concomitantly with immunosuppressants.

RESULTS

Eight patients (22%) were ANA positive at baseline; none developed anti-double-stranded DNA antibodies (aDNAds) at week 6. Three of them were re-treated: there were increasing ANA titres in all cases and developing aDNAds in two. Only six of 28 patients who were ANA negative at baseline changed their ANA status at week 6, but none developed aDNAds. One of them was retreated showing a further increase in ANA titre and developing aDNAds at high titre. No patient presented lupus-like syndrome.

CONCLUSIONS

Only a few CD patients treated with infliximab and immunosuppressants develop ANAs. This condition is not associated with aDNAds and/or lupus-like syndrome in the majority of cases.

Detection of anti-cytokeratin 8 antibody in the serum of patients with cryptogenic fibrosing alveolitis and pulmonary fibrosis associated with collagen vascular disorders

BACKGROUND

It has been suggested that the humoral immune system plays a role in the pathogenesis of cryptogenic fibrosing alveolitis (CFA). Although circulating autoantibodies to lung protein(s) have been suggested, none of the lung proteins have been characterised. The purpose of this study was to determine the antigen to which the serum from patients with pulmonary fibrosis reacted.

METHODS

The anti-A549 cell antibody was characterised in a patient with CFA using Western immunoblotting and immunohistochemical staining of A549 cells. As we identified that one of the antibodies against A549 cells was anti-cytokeratin 8, the expression of mRNA of cytokeratin 8 in A549 cells was evaluated. In addition, we attempted to establish an enzyme linked immunosorbent assay to measure the levels of anti-cytokeratin 8 antibody in the serum of patients with CFA and pulmonary fibrosis associated with collagen vascular disorders (PF-CVD).

RESULTS

Initially two anti-A549 cell antibodies were detected in the serum of patients with pulmonary fibrosis, one of which was characterised as anticytokeratin 8 antibody by Western immunoblotting. We were able to establish an ELISA to measure anti-cytokeratin 8 antibody and found significantly higher levels in patients with CFA and PF-CVD than in normal volunteers, patients with sarcoidosis, pneumonia, and pulmonary emphysema.

CONCLUSIONS

One of the anti-A549 cell antibodies in the serum of patients with CFA was against cytokeratin 8. The serum levels of anti-cytokeratin 8 antibody were increased in patients with CFA and PF-CVD. These results suggest that anticytokeratin 8 antibody may be involved in the process of lung injury in pulmonary fibrosis.

IgG subclass distribution in serum and rectal mucosa of monozygotic twins with or without inflammatory bowel disease

Serum samples from 26 monozygotic twin pairs concordant or discordant with regard to inflammatory bowel disease, and rectal biopsies from 42 twins of the same subject group, were examined for IgG subclasses. They were all compared with normal controls. Almost all affected twins were in clinical remission. Paired immunofluorescence staining of the rectal mucosa showed that those with ulcerative colitis had a significantly higher (p < 0.01) proportion of IgG1 producing mucosal immunocytes than normal controls (78.1% v 55.9%). Conversely, the IgG2 cell fraction was significantly reduced (15.9% v 34.6%). Healthy twins from ulcerative colitis pairs tended to show a raised proportion of IgG1 cells and the IgG2 cell fraction was significantly reduced (p < 0.05). In discordant ulcerative colitis twin pairs, no difference appeared in the cellular IgG subclass pattern between healthy and affected twins. Furthermore, the proportion of IgG1 in these healthy and diseased twins showed good correlation (T = 0.867). The results in rectal mucosa of twins with Crohn's disease were widely scattered and affected twins did not differ significantly from normal controls. Healthy twins, however, showed a marginally raised IgG1 cell proportion, but no correlation was seen between the IgG subclass fractions in discordant Crohn's disease twin pairs. The serum concentrations of IgG1 and IgG2 did not differ from normal controls in twins of either category. These results suggested that in ulcerative colitis, the aberrant mucosal production of IgG1 and IgG2 does not depend on active disease, but is apparently at least partially explained by a genetic impact. Conversely, the mucosal IgG subclass pattern in Crohn's disease appears to be determined mainly by exogenous variables.

Antibodies to cathepsin G in Crohn's disease

Antibodies directed against antigens in human neutrophils have proved to be of great diagnostic value in certain systemic vasculitides. Recent reports have focused the attention on these antigens as targets of antibodies in sera of patients with inflammatory bowel disease. We investigated the sera drawn from 60 patients suffering from biopsy proven Crohn's disease and 15 patients with active ulcerative colitis. Using sensitive enzyme-linked immunosorbent assays with purified antigens and Western blotting the following antibodies could be demonstrated: cathepsin G (cat-G) antibodies IgG 38.3%, IgM 13.3%, IgA 23.3% and antibodies against human leucocyte elastase (HLE) IgG, IgA, IgM 3.3%. Low but significant correlations could be found for cat-G antibodies (IgG) and the van HEES index of activity. 73.9% of the cat-G (IgG) positive patients had colon involvement. In the sera of patients with ulcerative colitis no antibodies to cat-G or HLE were detectable. Only 8.3% of the patients with Crohn's disease had antibodies against proteinase 3 (C-ANCA). Our data indicate that cat-G among other myeloid lysosomal enzymes seems to be an important target antigen of antibodies in sera of patients with Crohn's disease. Cat-G antibodies might be helpful to distinguish Crohn's disease from ulcerative colitis.

Antibodies to cytoskeletal proteins in patients with Crohn's disease

The immunologic basis of inflammatory bowel disease has been the focus of interest of a series of studies on Crohn's disease and the process of immune sensitization at the gastrointestinal mucosal level is functionally poorly understood. To date only few contradictory reports concerning the incidence of autoantibodies in patients with this disease exist. The aim of this study was to investigate the sera drawn from 60 patients suffering from biopsy-proven Crohn's disease to evaluate the prevalence of autoantibodies against nuclear antigens and cytoskeletal proteins. Using standard methods, no anti-nuclear antibodies or antibodies to extractable nuclear antigens could be detected. All sera were also negative for antibodies to double-stranded DNA, anti-mitochondrial antibodies, and antibodies to gastric parietal cells. Using sensitive enzyme-linke immunosorbent assays with purified antigens and Western blotting with cytoskeletal proteins of human intestinal cells, the following antibodies could be demonstrated: cytokeratin 18 autoantibodies (IgG 20.0%; IgM 6.7%; IgA 13.3%), actin antibodies (IgG 36.7%; IgM 48.3%, IgA 26.7%), desmin antibodies (IgG 6.7%; IgM 15.08%; IgA 5.0%), vimentin antibodies (IgG 3.3%; IgM 16.7%; IgA 10.0%) and tropomyosin antibodies (IgG 3.3%; IgM 3.3%, IgA 5.0%). Statistically significant correlations could be found for levels of cytokeratin 18 antibodies (IgM-type) and the BEST index of activity, and for levels of desmin antibodies (IgM-type) and the van HEES index of activity. Highest levels could be measured for actin antibodies (IgG-type) in patients with isolated disease manifestation in the colon. The mechanism of induction of autoantibodies against cytoskeletal components in Crohn's disease still remains obscure. Unmasking of hidden antigens after cell injury during the inflammatory process of disease might lead to sensitization and antibody production. The pattern of antibodies in patients with Crohn's disease seems to be different compared with that of connective tissue diseases.

Quantitation of autoantibodies to cytokeratins in sera from patients with squamous cell carcinoma of the oesophagus

Sera drawn from healthy individuals, patients with squamous cell carcinoma (SCC) of the oesophagus and patients with mild active oesophagitis were examined for autoantibodies to cytoskeletal proteins extracted from the normal oesophageal keratinocyte or from 2 carcinoma cell lines, each of the latter have a simple cytoskeleton. Using a radioimmunoassay with normal oesophageal cytokeratins as bound antigen, 86 normal, 76 SCC and 14 oesophagitis sera were compared. No significant difference in autoantibody titre was found. When the bound antigen was changed to one containing predominantly simple epithelial cytokeratins a significant increase (32% P less than 0.001) was noted in the SCC category only. Western blots using simple epithelial cell extracts as antigen revealed autoantibodies to cytokeratins 8, 18 and 19 as well as to one other unidentified protein in most SCC sera, and in some normal sera. Antibodies to cytokeratin 18 predominated. Normal and SCC sera were applied using indirect immunofluorescent techniques to normal oesophageal keratinocytes, SNO oesophageal SCC cells and HeLa cells grown in vitro. Autoantibodies to oesophageal cytokeratins were, with few exceptions, barely detectable. Strong reactions were noted against SNO and HeLa cytoskeletal components, but also against nuclear membrane and nucleolar determinants. These experiments suggest that raised levels of autoantibodies to certain cytoskeletal and nuclear determinants may be a feature of oesophageal cancer.

Expression of cytoskeleton components in various Epstein-Barr virus infected cell lines

It has been shown that viruses can induce alterations in the content and distribution of cytoskeleton structures, particularly actin microfilaments and microtubules. An immunomorphologic study of the cytoskeleton components of various EBV-infected cell lines with expression of different functions of EBV genome has been performed using antibodies to each of its three major components. Intermediate filaments and microtubules were similarly represented in all examined lymphoblastoid cell lines. The distribution of actin microfilaments, on the contrary, differed significantly from cell line to cell line. It is concluded that the morphologic expression of actin might depend on the expression of EBV genome. Furthermore, some of these cell lines might represent a useful substrate for the identification of anticytoskeleton antibodies, mainly anti-actin antibodies, in human sera.

Autoimmunity in chronic liver disease caused by hepatitis delta virus

Recent evidence shows that chronic liver disease induced by hepatitis delta virus is closely associated with production of autoantibodies. To verify this sera from patients with hepatitis delta virus and from those with hepatitis B virus mediated chronic liver disease were tested for a panel of autoantibodies. Although the traditional non-organ specific autoantibodies were similarly distributed in the two groups, a considerably higher prevalence of IgG basal cell layer antibodies, IgM anti-intermediate filaments, and IgG antimicrotubule antibodies was found. Although these phenomena might be secondary to hepatitis delta virus infection, they might be the serological markers of underlying immune events.

Vimentin and keratin intermediate filaments expression by K562 leukemic cell line

The expression of intermediate filaments (IMF) by K562 leukemic cell line has been studied by the use of polyclonal and monoclonal antibodies. These cells exhibited an extremely rich network of IMF reacting with both anti-vimentin and anti-keratin antibodies. Although these results need to be confirmed by different techniques, such as immunoblotting, they suggest the possibility that leukemic cell lines can express different types of IMF similarly to other cultured cells.