ORIGINAL ARTICLE Lectin-based Immunoassay for Aberrant IgG Glycosylation as the Biomarker for Crohn’s Disease Shinichiro Shinzaki, MD, PhD,* ,† Eri Kuroki, MSc,* Hideki Iijima, MD, PhD, † Norika Tatsunaka, MSc,* Mayuko Ishii, BSc,* Hironobu Fujii, BSc,* Yoshihiro Kamada, MD, PhD,* ,† Taku Kobayashi, MD, PhD, ‡ Narihiro Shibukawa, MD, † Takahiro Inoue, MD, † Masahiko Tsujii, MD, PhD, † Shunsaku Takeishi, PhD, § Tsunekazu Mizushima, MD, PhD, k Atsushi Ogata, MD, PhD, ¶ Tetsuji Naka, MD, PhD, ** Scott E. Plevy, MD, ‡ Tetsuo Takehara, MD, PhD, † and Eiji Miyoshi, MD, PhD* Background: Easily measured and clinically useful biomarkers for inflammatory bowel disease (IBD) are required to advance patient care. We previously reported that the agalactosyl fraction among fucosylated IgG oligosaccharides is increased in IBD, especially Crohn’s disease (CD). The present study aimed to establish a simple detection system for aberrant glycosylated IgG based on lectin–oligosaccharide interactions. Methods: Lectins with higher affinity to serum IgG from IBD patients than healthy volunteers (HV) were screened by lectin microarray. Binding of selected lectins to agalactosyl IgG was definitively confirmed using step-by-step glycosidase treatment. Using the selected lectins, a lectin-enzyme-linked immunosorbent assay system was established and its clinical utility was investigated in a total of 410 (249 Japanese and 161 American) IBD patients, disease controls, and HVs. Results: Agaricus bisporus Agglutinin (ABA) and Griffonia simplicifolia Lectin-II (GSL-II) had higher affinity for serum agalactosyl IgG from IBD patients, especially those with CD, compared to HV. Agalactosyl IgG levels measured by a lectin-enzyme immunoassay (EIA) with ABA or GSL-II were significantly increased in CD compared with HV and disease controls. Agalactosyl IgG levels significantly correlated with disease activity, showed higher predictability of therapeutic outcomes for CD than C-reactive protein levels, and exhibited higher specificity for diagnosing IBD in combination with anti-Saccharomyces cerevisiae antibody (ASCA). Validation analysis showed that agalactosyl IgG levels were significantly increased in Japanese and American CD patients. Conclusions: A lectin-EIA for agalactosyl IgG is a novel biomarker for IBD, especially in patients with CD. (Inflamm Bowel Dis 2013;19:321–331) Key Words: inflammatory bowel disease, Crohn’s disease, biomarker, oligosaccharides, IgG T he human inflammatory bowel diseases (IBD), Crohn’s dis- ease (CD) and ulcerative colitis (UC), are characterized by chronic relapsing and remitting inflammation in the digestive tract. Although genetic predisposition, environmental factors, and altered immune responses have pivotal roles in the pathogen- esis of IBD, precise etiologies remain unknown. Despite recent therapeutic advances, 1,2 surgical care remains a mainstay treat- ment of IBD. 3 Therefore, a biomarker that reflects clinical course and therapeutic outcome is in high demand. Several serologic markers have been developed for the diagnosis of IBD such as anti-Saccharomyces cerevisiae antibody (ASCA), 4 peripheral antineutrophil cytoplasmic antibody, 5 or anti-outer membrane porin protein C, and anti-CBir1 flagellin. 6 However, these anti- bodies generally lack diagnostic and prognostic sensitivity and specificity to alter clinical decision making. Immunoglobulin (Ig) G carries N-linked oligosacchar- ides at the Cgamma2 domain of the Fc fragment at asparagine 297, all of which are biantennary complex-type with or with- out bisecting N-acetylglucosamine (GlcNAc), core-fucose, Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.ibdjournal.org). Received for publication March 23, 2012; Accepted March 26, 2012. From the *Department of Molecular Biochemistry and Clinical Investigation, Osaka University Graduate School of Medicine, Suita, Osaka, Japan; † Department of Gastroenterology and Hepatology, Osaka University Graduate School of Med- icine, Suita, Osaka, Japan; ‡ Center for Gastrointestinal Biology and Diseases, Uni- versity of North Carolina School of Medicine, Chapel Hill, North Carolina, USA; § GP BioScience Ltd., Sapporo, Hokkaido, Japan; k Department of Surgery, Osaka University Graduate School of Medicine, Suita, Osaka, Japan; ¶ Department of Respiratory Medicine, Allergy and Rheumatic Diseases, Osaka University Gradu- ate School of Medicine, Suita, Osaka, Japan; and **Laboratory for Immune Signal, National Institute of Biomedical Innovation, Ibaraki, Osaka, Japan. The first two authors contributed equally to this work. Reprints: Eiji Miyoshi, MD, PhD, Department of Molecular Biochemistry and Clinical Investigation, Osaka University Graduate School of Medicine, 1-7 Yamadaoka, Suita, Osaka 565-0871, Japan (e-mail: emiyoshi@sahs.med. osaka-u.ac.jp). Copyright © 2013 Crohn’s & Colities Foundation of America, Inc. DOI 10.1097/MIB.0b013e318280eade Published online 19 December 2012. Inflamm Bowel Dis  Volume 19, Number 2, February 2013 www.ibdjournal.org | 321 Copyright © 2013 Crohn’s & Colitis Foundation of America, Inc. Unauthorized reproduction of this article is prohibited.