Anti-integrin αvβ6 antibody as a diagnostic marker for pediatric patients with ulcerative colitis

概要

Ulcerative colitis (UC) is a multifactorial chronic dis- order with a high prevalence worldwide. UC affects patients in all age groups; however, pediatric-onset UC is generally more severe than adult-onset UC.1 To avoid long- term unfavorable outcomes, such as growth failure, early and proper diagnosis with subsequent treatment is needed for pediatric UC patients. Gastrointestinal endoscopy is the criterion standard for a diagnosis of UC, but the procedure is invasive for pediatric patients, often requiring the use of general anesthesia. Thus, a non-invasive and disease-specific marker for diagnosing pediatric UC is strongly required.

We recently identified anti–integrin avb6 antibody in adult UC patients with very high sensitivity and specificity, indicating that this autoantibody can be a useful diagnostic marker for UC in adult patients.2 Here, we examined the presence and diagnostic value of this antibody in pediatric patients with inflammatory bowel disease (IBD), including UC. We enrolled 261 pediatric IBD patients (131 UC, 95 Crohn’s disease [CD], 10 IBD—unclassified [IBD-U], 25 pri- mary immunodeficiency [PID] with IBD), 40 non-IBD pa- tients (13 PID without IBD and 27 non-IBD enterocolitis), and 28 non-enterocolitis control subjects (Supplementary Figure 1A). Details of patients and control subjects are provided in the Supplementary Methods.

A total of 124 of the 131 UC patients (94.7%) had immunoglobulin (Ig) G antibodies against integrin avb6 based on a cutoff value of the mean plus 3 standard de- viations (optical density ¼ 0.2525) for the non-enterocolitis control subjects. Moreover, these IgG antibodies were detected in 31/95 (32.6%) CD, 2/10 (20.0%) IBD-U, 2/25(8.0%) PID with IBD, 0/13 (0%) PID without IBD, and 1/27 (3.7%) non-IBD enterocolitis patients, and in 1/28 (3.6%) non-enterocolitis control subjects (Figure 1A). The sensi- tivity and specificity of anti–integrin avb6 IgG autoanti- bodies in UC patients were, respectively, 94.7% (124/131) and 81.3% (161/198). On the other hand, the specificity of anti–integrin avb6 IgG autoantibodies in the diagnosis of UC against CD was 67.4% (64/95).

Next, we examined the IgG subclasses and autoantibody isotypes. Among 47 randomly selected antibody-positive UC patients, 47 (100.0%), 38 (80.9%), 14 (29.8%), 26 (55.3%), 9 (19.1%), 28 (59.6%), and 12 (25.5%) had IgG1, IgG2, IgG3, IgG4, IgM, IgA, and IgE antibodies, respectively (Supplementary Figure 1B and C). These data are similar to those found in the adult patients previously reported with UC.2 Moreover, the subclasses and isotypes of anti–integrin avb6 antibodies in patients with CD or PID with IBD were similar to those of patients with UC (Supplementary Figure 1B and C)

Previously, we showed that IgG of adult UC patients blocked integrin avb6–fibronectin binding through an Arg-Gly-Asp (RGD) tripeptide motif (Supplementary Figure 2A). Consistently, a solid-phase binding assay showed that IgG of 45/47 (95.7%) antibody-positive pediat- ric UC patients blocked integrin avb6–fibronectin binding (Figure 1B). The blocking activity of IgG was correlated with the anti–integrin avb6 antibody titers (r ¼ 0.83; P < 0.001) (Supplementary Figure 2B). Furthermore, RGD-serine (RGDS) peptides inhibited the binding of IgG to integrin avb6 in a dose-dependent manner, whereas Arg-Gly-Glu-Ser (RGES) peptides did not block such binding (Supplementary Figure 2C). Moreover, IgG of 23/25 (92.0%) CD, 2/2 (100%) IBD-U, and 2/2 (100%) PID with IBD patients with anti–integrin avb6 antibody inhibited integrin avb6–fibro- nectin binding (Figure 1B), and RGDS peptides blocked the binding of IgG of these patients to integrin avb6 (Supplementary Figure 2D and E). In contrast, IgG of non-IBD enterocolitis patients and non-enterocolitis control subjects with anti–integrin avb6 antibody neither blocked integrin avb6–fibronectin binding nor competed with RGDS peptides on binding to integrin avb6 (Figure 1B and Supplementary Figure 2E).

Notably, a considerable number of CD patients in this study (31/95, 32.6%) (Figure 1A) had anti–integrin avb6 antibodies, in contrast to its low number in adult CD patients (5/71, 7.0%).2 Moreover, these antibodies of CD patients showed characteristics similar to those of UC patients, including IgG subclasses, isotypes, blocking activity on integrin avb6–fibronectin binding, and inhibition of RGDS peptide binding to integrin avb6.

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