Persistence of Elevated Deamidated Gliadin Peptide Antibodies on a Gluten-free Diet Indicates Nonresponsive Coeliac Disease

B. N. Spatola; K. Kaukinen; P. Collin; M. Mäki; M. F. Kagnoff; P. S. Daugherty

Disclosures

Aliment Pharmacol Ther. 2014;39(4):407-417. 

In This Article

Abstract and Introduction

Abstract

Background Histologically nonresponsive coeliac disease (NRCD) is a potentially serious condition diagnosed during the follow-up of coeliac disease (CD) when patients have persistent villous atrophy despite following a gluten-free diet (GFD).

Aim As current assessments of recovery are limited to invasive and costly serial duodenal biopsies, we sought to identify antibody biomarkers for CD patients that do not respond to traditional therapy.

Methods Bacterial display peptide libraries were screened by flow cytometry to identify epitopes specifically recognised by antibodies from patients with NRCD, but not by antibodies from responsive CD patients. Deamidated gliadin was confirmed to be the antigen mimicked by library peptides using ELISA with sera from NRCD (n = 15) and responsive CD (n = 45) patients on a strict GFD for at least 1 year.

Results The dominant consensus epitope sequence identified by unbiased library screening QPxx(A/P)FP(E/D) was highly similar to reported deamidated gliadin peptide (dGP) B-cell epitopes. Measurement of anti-dGP IgG titre by ELISA discriminated between NRCD and responsive CD patients with 87% sensitivity and 89% specificity. Importantly, dGP antibody titre correlated with the severity of mucosal damage indicating that IgG dGP titres may be useful to monitor small intestinal mucosal recovery on a GFD.

Conclusions The finding of increased levels of anti-dGP IgG antibodies in CD patients on strict GFDs effectively identifies patients with NRCD. Finally, anti-dGP IgG assays may be useful to monitor mucosal damage and histological improvement in CD patients on a strict GFD.

Introduction

Coeliac disease (CD) is an autoimmune disease that is activated in genetically susceptible individuals by the ingestion of gluten in wheat and similar prolamins in rye and barley.[1] The diagnosis of CD is suggested by elevated levels of serum antibodies to tissue transglutaminase (TG2) and/or deamidated gliadin peptides (dGP) and confirmed by small bowel mucosal biopsy showing the characteristic histological features of villous atrophy and crypt hyperplasia.[2] Diagnosis is essential to prevent morbidity and possible mortality associated with prolonged untreated CD.[3,4] The only treatment currently effective for CD is a strict gluten-free diet (GFD).[5] Even so, a majority of CD patients exhibit slow mucosal recovery rates during a GFD as measured by biopsy. An estimated 8–35% of patients recover after 2 years of GFD and 66% of patients recover after 5 years.[6–8] However, 10–19% of patients do not exhibit a histological response to a GFD and are thus considered to have nonresponsive CD (NRCD).[9] NRCD is defined as persistent small bowel mucosal villous atrophy during a GFD with or without symptoms and can only be diagnosed by follow-up intestinal biopsy.[2] Continued exposure to gluten (36–45%) is the most common cause of NRCD.[9,10] If a strict GFD is confirmed, NRCD may be due to refractory CD (RCD), which occurs in approximately 4% of CD patients.[11] RCD is defined as the failure of a strict GFD to improve damaged intestinal architecture and relieve symptoms in patients with confirmed CD.[3] Poor response to a GFD may also reflect the complicating coexistence of other conditions including irritable bowel syndrome (IBS), lactose intolerance, microscopic colitis and small intestine bacterial overgrowth.[9,10]

Serological measures of the response of CD patients to a GFD that identify patients with NRCD would have substantial clinical value.[12] Previous studies failed to link the disappearance of TG2[13–15] and endomysial antibodies (EMA)[16] to CD patient recovery while on a GFD. Outside of established CD diagnostic assays, the monitoring of serum intestinal fatty acid-binding protein (I-FABP) levels,[17] faecal fat excretion,[18] urinary lactulose-to-mannitol excretion ratios[19] and the maximum concentration of simvastatin in the small intestine[20] may be useful to identify continued mucosal damage or GFD transgressions non-invasively but are not in clinical use. Thus, despite a clear need for non-invasive diagnostic methods to identify patients with NRCD, objective assessments of morphological recovery rely upon invasive and costly duodenal biopsies and are rarely made.

The objective of this study was to screen for serum antibody biomarkers that could serve as an economical and non-invasive diagnostic to identify NRCD and monitor morphological recovery in CD patients on a strict GFD. Application of a novel unbiased screening method to screen for serum antibodies present in patients with active CD, but not in healthy volunteers, recently enabled the identification of immunodominant B-cell epitopes in CD patients, which in turn provided exceptional diagnostic efficiency.[21] Because of this result and the clinical need for non-invasive diagnostics of NRCD and intestinal recovery, we applied a similar unbiased method to screen for candidate biomarkers of NRCD and convalescence while on a GFD. Our results indicate that an existing assay for dGP IgG antibodies, used clinically to diagnose active CD, can also serve as a diagnostic to identify patients with NRCD and to monitor CD patient recovery while on a GFD.

Comments

3090D553-9492-4563-8681-AD288FA52ACE

processing....