Antibody responses in Crohn’s disease

Abstract

Our current knowledge about the pathophysiology of the inflammatory bowel diseases (IBD) is that in a genetic susceptible host, the intestinal flora triggers and drives an aberrant immune response resulting in chronic inflammation of the gut. This so-called loss of tolerance to commensal bacteria is supported by the occurrence of specific serum antibody responses to microbial antigens in both Crohn’s disease (CD) and ulcerative colitis (UC). The presence of antibodies in IBD has been acknowledged for a long time: antibodies to colon extract were reported in the late 50s.1Broberger O. Perlmann P. Autoantibodies in human ulcerative colitis.J Exp Med. 1959; 110: 657-674Crossref PubMed Scopus (211) Google Scholar, 2Harrison W.J. Autoantibodies against intestinal and gastric mucous cells in ulcerative colitis.Lancet. 1965; 1: 1346-1350Abstract Scopus (34) Google Scholar Subsequently, strong antibody responses to a variety of epitopes have been documented. The antibodies that have been most thoroughly studied are antibodies against mannose epitopes from the yeast Saccharomyces cerevisiae (ASCA)3Sendid B. Colombel J.F. Jacquinot P.M. Faille C. Fruit J. Cortot A. Lucidarme D. Camus D. Poulain D. Specific antibody response to oligomannosidic epitopes in Crohn’s disease.Clin Diag Lab Immunol. 1996; 3: 219-226PubMed Google Scholar, 4Quinton J.F. Sendid B. Reumaux D. Duthilleul P. Cortot A. Grandbastien B. Charrier G. Targan S.R. Colombel J.F. Poulain D. Anti-Saccharomyces Cereviasiae mannan antibodies combined with anti-neutrophil cytoplasmic autoantibodies in inflammatory bowel disease prevalence and diagnostic role.Gut. 1998; 42: 788-791Crossref PubMed Scopus (536) Google Scholar and autoantibodies against an unidentified 50-kilodalton nuclear lamina protein present in neutrophils (atypical pANCA).5Terjung B. Spengler U. Sauerbruch T. Worman H.J. “Atypical p-ANCA” in IBD and Hepatobiliary disorders react with a 50-Kilodalton nuclear envelope protein of neutrophils and myeloid cell lines.Gastroenterology. 2000; 119: 310-322Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar More recently, antibodies to the outer-membrane porin C of Escherichia coli (OmpC), against a Pseudomonas fluorescens-associated sequence (I2) and were reported in CD patients.6Sutton C.L. Kim J. Yamane A. Dalwadi H. Wei B. Landers C. Targan S.R. Braun J. Identification of a novel bacterial sequence associated with Crohn’s disease.Gastroenterology. 2000; 119: 23-31Abstract Full Text Full Text PDF PubMed Scopus (197) Google Scholar, 7Landers C.J. Cohavy O. Misra R. Yang H. Lin Y.C. Braun J. Targan S.R. Selected loss of tolerance evidenced by Crohn’s disease-associated immune responses to auto- and microbial antigens.Gastroenterology. 2002; 123: 689-699Abstract Full Text Full Text PDF PubMed Scopus (374) Google Scholar A recent study by Landers et al.7Landers C.J. Cohavy O. Misra R. Yang H. Lin Y.C. Braun J. Targan S.R. Selected loss of tolerance evidenced by Crohn’s disease-associated immune responses to auto- and microbial antigens.Gastroenterology. 2002; 123: 689-699Abstract Full Text Full Text PDF PubMed Scopus (374) Google Scholar showed that 85% of CD patients elicit antibody responses to at least 1 antigen but that only a minority (4%) of patients responds to several antigens. Furthermore, 4 clusters of antibody responses could be identified: ASCA, OmpC/I2, ANCA, or no/low response. Therefore, rather than a global loss of tolerance, there seem to be subsets of patients with different responses to selected microbial and autoantigens. The exact meaning of each of these responses remains unclear to date and also their clinical value is a matter of debate. Antibodies appear to offer little value to the current diagnostic algorithm of IBD, partly because of their modest sensitivity: the prevalence of ASCA in CD ranges from 49%–60% and the prevalence of atypical pANCA in UC is between 40%–60%.4Quinton J.F. Sendid B. Reumaux D. Duthilleul P. Cortot A. Grandbastien B. Charrier G. Targan S.R. Colombel J.F. Poulain D. Anti-Saccharomyces Cereviasiae mannan antibodies combined with anti-neutrophil cytoplasmic autoantibodies in inflammatory bowel disease prevalence and diagnostic role.Gut. 1998; 42: 788-791Crossref PubMed Scopus (536) Google Scholar, 8Ruemmele F.M. Targan S.R. Levy G. Dubinsky M. Braun J. Seidman E.G. Diagnostic accuracy of serological assays in pediatric inflammatory bowel disease.Gastroenterology. 1998; 115: 822-829Abstract Full Text Full Text PDF PubMed Scopus (352) Google Scholar, 9Peeters M. Joossens S. Vermeire S. Vlietinck R. Bossuyt X. Rutgeerts P. Diagnostic value of Anti Saccharomyces cerevisiae and antineutrophil cytoplasmic autoantibodies in inflammatory bowel disease.Am J Gastroenterol. 2001; 96: 730-734Crossref PubMed Google Scholar pANCA and ASCA carry on the contrary a very high specificity (ranging from 95%–99%), especially when used in combination, and hence may be of help in those patients where distinction between CD or UC is not clear despite the classical tools.8Ruemmele F.M. Targan S.R. Levy G. Dubinsky M. Braun J. Seidman E.G. Diagnostic accuracy of serological assays in pediatric inflammatory bowel disease.Gastroenterology. 1998; 115: 822-829Abstract Full Text Full Text PDF PubMed Scopus (352) Google Scholar, 9Peeters M. Joossens S. Vermeire S. Vlietinck R. Bossuyt X. Rutgeerts P. Diagnostic value of Anti Saccharomyces cerevisiae and antineutrophil cytoplasmic autoantibodies in inflammatory bowel disease.Am J Gastroenterol. 2001; 96: 730-734Crossref PubMed Google Scholar Dubinsky et al. showed that incorporation of sequential noninvasive testing into a diagnostic strategy in children with an uncertain diagnosis of IBD may avoid costly evaluations and facilitate the clinical decision making.10Dubinsky M.C. Ofman J.J. Urman M. Targan S.R. Seidman E.G. Clinical utility of serodiagnostic testing in suspected pediatric inflammatory bowel disease.Am J Gastroenterol. 2001; 96: 758-765Crossref PubMed Google Scholar In her study, 128 children received in parallel to a complete work-up for IBD serologic testing with ASCA and ANCA. Sequential testing, using a sensitive ASCA/ANCA assay followed, if positive, by more specific ASCA and pANCA reading reduced false-positive diagnoses by 81%. Only 4 of 128 patients would have received unnecessary colonoscopy. Antibodies help the clinician the most in patients with indeterminate colitis (IC). In a collaborative study between the Universities of Lille, Vienna, and Leuven, the discriminative value of ASCA and pANCA to predict definitive diagnosis was somewhat disappointing (63.6% for UC [ASCA-/atypical ANCA+] and 80% for CD [ASCA+/atypical ANCA-]).11Joossens S. Reinisch W. Vermeire S. Sendid B. Poulain D. Peeters M. Geboes K. Bossuyt X. Vandewalle P. Oberhuber G. Vogelsang H. Rutgeerts P. Colombel J.F. The value of serologic markers in indeterminate colitis a prospective follow-up study.Gastroenterology. 2002; 122: 1242-1247Abstract Full Text Full Text PDF PubMed Scopus (287) Google Scholar A remarkable finding from this study was that a much greater percentage (48.5%) of patients do not show serum reactivity to these antigens and that these seronegative patients remain indetermined after a mean duration of disease of 9.9 years. In this issue of Gastroenterology, Mow et al.12Mow W.S. Vasiliauskas E.A. Lin Y.-C. Fleshner P.R. Papadakis K.A. Taylor K.D. Landers C.J. Abreu-Martin M.T. Rotter J.I. Yang H. Targan S.R. Association of antibody responses to microbial antigens and complications of small-bowel Crohn’s disease.Gastroenterology. 2004; 126: 414-425Abstract Full Text Full Text PDF PubMed Scopus (454) Google Scholar examined the association of antibodies against microbial antigens and clinical phenotypes of Crohn’s disease. The authors studied antibodies against 4 different (microbial) antigens: Saccharomyces cerevisiae (ASCA), Pseudomonas fluorescens (I2), Escherichia coli (OmpC) and neutrophils (atypical pANCA). Analyzing each of these markers separately, they found that patients expressing anti-I2 were more likely to have small bowel disease, fibrostenosing CD, and require small bowel surgery and that patients expressing anti-OmpC were more associated with fibrostenosis, internal perforating disease, and small bowel surgery. The phenotypic characteristics of ASCA and ANCA antibody responses have already been the subject of various studies, including some by the same group. Atypical pANCA have been associated with an UC-like CD behavior,13Vasiliauskas E.A. Plevy S.E. Landers C.J. Binder S.W. Ferguson D.M. Yang H. Rotter J.I. Vidrich A. Targan S.R. Perinuclear antineutrophil cytoplasmic antibodies in patients with Crohn’s disease define a clinical subgroup.Gastroenterology. 1996; 110: 1810-1819Abstract Full Text Full Text PDF PubMed Scopus (270) Google Scholar older age at onset,14Vasiliauskas E.A. Kam L.Y. Karp L.C. Gaiennie J. Yang H. Targan S.R. Marker antibody expression stratifies Crohn’s disease into immunologically homogeneous subgroups with distinct clinical characteristics.Gut. 2000; 47: 487-496Crossref PubMed Scopus (294) Google Scholar, 15Klebl F.H. Bataille F. Bertea C.R. Herfarth H. Hofstadter F. Scholmerich J. Rogler G. Association of perinuclear antineutrophil cytoplasmic antibodies and anti-Saccharomyces cerevisiae antibodies with Vienna classification subtypes of Crohn’s disease.Inflamm Bowel Dis. 2003; 9: 302-307Crossref PubMed Scopus (57) Google Scholar severe treatment resistant left-sided colitis,16Sandborn W.J. Landers C.J. Tremaine W.J. Targan S.R. Association of antineutrophil cytoplasmic antibodies with resistance to treatment of left-sided ulcerative colitis results of a pilot study.Mayo Clin Proc. 1996; 71: 431-436Abstract Full Text Full Text PDF PubMed Scopus (127) Google Scholar early surgery and with the development of pouchitis17Sandborn W.J. Landers C.J. Tremaine W.J. Targan S.R. Antineutrophil cytoplasmic antibody correlates with chronic pouchitis after ileal pouch-anal anastomosis.Am J Gastroenterol. 1995; 90: 740-747PubMed Google Scholar after ileoanal pouch anastomosis. ASCA have been associated with ileal disease,13Vasiliauskas E.A. Plevy S.E. Landers C.J. Binder S.W. Ferguson D.M. Yang H. Rotter J.I. Vidrich A. Targan S.R. Perinuclear antineutrophil cytoplasmic antibodies in patients with Crohn’s disease define a clinical subgroup.Gastroenterology. 1996; 110: 1810-1819Abstract Full Text Full Text PDF PubMed Scopus (270) Google Scholar, 18Vermeire S. Peeters M. Vlietinck R. Joossens S. Den Hond E. Bulteel V. Bossuyt X. Geypens B. Rutgeerts P. Anti-Saccharomyces cerevisiae antibodies (ASCA), phenotypes of IBD, and intestinal permeability a study in IBD families.Inflamm Bowel Dis. 2001; 7: 8-15Crossref PubMed Scopus (158) Google Scholar young age at onset4Quinton J.F. Sendid B. Reumaux D. Duthilleul P. Cortot A. Grandbastien B. Charrier G. Targan S.R. Colombel J.F. Poulain D. Anti-Saccharomyces Cereviasiae mannan antibodies combined with anti-neutrophil cytoplasmic autoantibodies in inflammatory bowel disease prevalence and diagnostic role.Gut. 1998; 42: 788-791Crossref PubMed Scopus (536) Google Scholar, 18Vermeire S. Peeters M. Vlietinck R. Joossens S. Den Hond E. Bulteel V. Bossuyt X. Geypens B. Rutgeerts P. Anti-Saccharomyces cerevisiae antibodies (ASCA), phenotypes of IBD, and intestinal permeability a study in IBD families.Inflamm Bowel Dis. 2001; 7: 8-15Crossref PubMed Scopus (158) Google Scholar and fibrostenosing or internal perforating disease.14Vasiliauskas E.A. Kam L.Y. Karp L.C. Gaiennie J. Yang H. Targan S.R. Marker antibody expression stratifies Crohn’s disease into immunologically homogeneous subgroups with distinct clinical characteristics.Gut. 2000; 47: 487-496Crossref PubMed Scopus (294) Google Scholar Most of the previously documented clinical phenotypes associated with ASCA and ANCA were replicated in this study. However, since the majority of the patients in the present study were also part of the study by Vasiliauskas et al.14Vasiliauskas E.A. Kam L.Y. Karp L.C. Gaiennie J. Yang H. Targan S.R. Marker antibody expression stratifies Crohn’s disease into immunologically homogeneous subgroups with distinct clinical characteristics.Gut. 2000; 47: 487-496Crossref PubMed Scopus (294) Google Scholar from the same group, these results are not surprising and cannot be seen as purely independent. When combining all antibodies in the study by Mow et al.,12Mow W.S. Vasiliauskas E.A. Lin Y.-C. Fleshner P.R. Papadakis K.A. Taylor K.D. Landers C.J. Abreu-Martin M.T. Rotter J.I. Yang H. Targan S.R. Association of antibody responses to microbial antigens and complications of small-bowel Crohn’s disease.Gastroenterology. 2004; 126: 414-425Abstract Full Text Full Text PDF PubMed Scopus (454) Google Scholar anti-I2 was independently associated with fibrostenosis and small bowel surgery, anti-Omp C with internal perforating behavior and ASCA with small bowel disease, fibrostenosis, and small bowel surgery. Taken together, these results suggest that antibody responses to I2, OmpC, and ASCA are associated with complicated small bowel Crohn’s disease. The authors further hypothesized that the severity of the disease course would correlate with the amount of “microbial hits.” In other words, the more antibody responses against different antigens present, the more likely that that patient will have a more severe disease course. Patients expressing reactivity to all 3 markers (ASCA, I2, and anti OmpC) were more likely to have fibrostenotic disease (72%), internal perforating disease (58.7%), and small bowel surgery (72%), compared with the patients without reactivity (23%, 27.9%, and 23% respectively). The presence of all 3 markers (ASCA, I2, and anti OmpC) carried a 8.6 times increased risk (95% CI, 4.0–18.9) for small bowel surgery, compared with patients without reactivity. The authors not only showed a qualitative correlation with the presence of microbial antibodies but also a quantitative relation with the amount of antibody production and complicated small bowel CD. Some reflections have to be made, however, when taking these results to clinical practice. First, this is a retrospective study and one should bear in mind the limitations of such. Therefore, it is important that these findings first be confirmed in independent series and more importantly, that prospective studies with these markers be conducted to assess the risk of microbial responses on the development of strictures and perforations and subsequent need for surgery. Until then, the testing of antibodies in IBD patients should not be performed routinely in clinical practice except in selected cases, such as when discrimination between CD and UC is difficult or for research purposes. However, if prospective studies confirm that antibodies can identify those patients likely to follow a more severe disease course, with a higher risk for surgery, then the determination of antibodies in clinical practice could have important consequences for patient management. Indeed, these patients might need more aggressive treatment or earlier introduction of immunosuppressive therapy. Also novel therapies such as anti-TNFα antibodies that induce rapid and prolonged mucosal healing might be introduced earlier. All of these questions remain unanswered for the moment. A condition sine qua non is that the antibody responses are stable over time. This has already been demonstrated for ASCA and pANCA,7Landers C.J. Cohavy O. Misra R. Yang H. Lin Y.C. Braun J. Targan S.R. Selected loss of tolerance evidenced by Crohn’s disease-associated immune responses to auto- and microbial antigens.Gastroenterology. 2002; 123: 689-699Abstract Full Text Full Text PDF PubMed Scopus (374) Google Scholar, 18Vermeire S. Peeters M. Vlietinck R. Joossens S. Den Hond E. Bulteel V. Bossuyt X. Geypens B. Rutgeerts P. Anti-Saccharomyces cerevisiae antibodies (ASCA), phenotypes of IBD, and intestinal permeability a study in IBD families.Inflamm Bowel Dis. 2001; 7: 8-15Crossref PubMed Scopus (158) Google Scholar and also in the present study for the other markers. Interestingly, NOD2 variants were not associated with complicated small bowel surgery from the multivariate analysis, indicating that disease behavior and severe course are more closely associated with immune responses toward microbial antigens than is the NOD2 genotype. Therefore, NOD2 can be seen as an indicator of Crohn’s disease susceptibility, whereas the microbial antibody responses are indicators of disease course and severity. Louis et al. have already drawn similar conclusions.19Louis E. Michel V. Hugot J.P. Reenaers C. Fontaine F. Delforge M. El Yafi F. Colombel J.F. Belaiche J. Early development of stricturing or penetrating pattern in Crohn’s disease is influenced by disease location, number of flares, and smoking but not by NOD2/CARD15 genotype.Gut. 2003; 52: 552-557Crossref PubMed Scopus (244) Google Scholar In his study on 163 patients with CD, the early development of stricturing or penetrating disease 5 years after diagnosis was influenced by the disease location, the clinical activity and the smoking habits, but not by the NOD2 genotype. The role of smoking on microbial antibody responses needs to be clarified. It would be interesting to know the smoking habits of the patients in the study by Mow et al. and the relation to antibody responses. Smoking in patients with Crohn’s disease is associated with more frequent relapse and postoperative recurrence. The principle mechanisms responsible for the detrimental effects of smoking in CD are not completely understood although there are many potential routes by which smoking could affect the disease course. Immunological factors, motility changes, mucus production, permeability, and changes in blood flow have all been suggested.20Thomas G.A. Rhodes J. Green J.T. Richardson C. Role of smoking in inflammatory bowel disease implications for therapy.Postgrad Med J. 2000; 76: 273-279Crossref PubMed Scopus (64) Google Scholar A Belgian study in 113 patients with CD found a negative association between smoking and ASCA suggesting that smoking might influence immune response against intestinal material.21Van Kemseke C. Belaiche J. Steeman C. Louis E. Negative association between smoking and anti-Saccharomyces cerevisiae antibodies in Crohn’s disease.Acta Gastroenterol Belg. 2003; 66: 1-6PubMed Google Scholar Smoking suppresses the immune system by blocking the antigen-mediated T cell proliferation. Furthermore, the production of IL-1β, IL-8, and TNF-α, which are crucial for the first-line defense against pathogens, is decreased in smokers compared with nonsmokers.20Thomas G.A. Rhodes J. Green J.T. Richardson C. Role of smoking in inflammatory bowel disease implications for therapy.Postgrad Med J. 2000; 76: 273-279Crossref PubMed Scopus (64) Google Scholar, 21Van Kemseke C. Belaiche J. Steeman C. Louis E. Negative association between smoking and anti-Saccharomyces cerevisiae antibodies in Crohn’s disease.Acta Gastroenterol Belg. 2003; 66: 1-6PubMed Google Scholar, 22Sopori M. Effects of cigarette smoke on the immune system.Nat Rev Immunol. 2002; 2: 372-377Crossref PubMed Scopus (905) Google Scholar In pulmonary diseases such as chronic bronchitis, smokers have a higher bacterial count in BAL as compared with nonsmokers23Qvarfordt I. Riise G.C. Andersson B.A. Larsson S. Lower airway bacterial colonization in asymptomatic smokers and smokers with chronic bronchitis and recurrent exacerbations.Respir Med. 2000; 94: 881-887Abstract Full Text PDF PubMed Scopus (29) Google Scholar and have a greater risk of bacterial exacerbations. In periodontitis, smoking enhances the colonization of the oral cavity by pathogenic bacteria.24Ertel A. Eng R. Smith S.M. The differential effect of cigarette smoke on the growth of bacteria found in humans.Chest. 1991; 100: 628-630Crossref PubMed Scopus (48) Google Scholar Further research is required to elucidate the exact mechanisms in which smoking may affect the microbial responses seen in Crohn’s disease. In conclusion, the currently available serologic antibodies in IBD provide insufficient accuracy for screening purposes. They seem however helpful in suspected pediatric IBD, in patients with indeterminate colitis, and based on the results of this study, they may also predict more aggressive Crohn’s disease with complications of strictures, fistulas, and early surgery. It remains to be determined if patient subgroups, selected on their response against microbial antigens, require more aggressive therapy and/or early introduction of anti-TNF strategies.