Anti-GP2 antibodies in inflammatory bowel disease patients with ileal pouch

Loss of tolerance to glycoprotein 2 isoforms 1 and 4 is associated with Crohn's disease of the pouch

BACKGROUND

Zymogen granule glycoprotein 2 (GP2) is a major autoantigen of Crohn's disease-specific pancreatic autoantibodies.

AIM

To test a link between loss of tolerance to isoforms of GP2 and pouch disorders in a cross-sectional study in ulcerative colitis patients with ileal pouch-anal anastomosis (IPAA).

METHODS

Serum samples of 117 consecutive ulcerative colitis patients after IPAA were tested for presence of Anti-GP2 isoforms 1 (GP2₁ ) & 4 (GP2₄ ) IgG and IgA as well as anti-Saccaromyces cervisiae (ASCA) IgG and IgA antibodies in a blinded fashion via enzyme-linked immunosorbent assay. Pouch disorders were diagnosed based on clinical, endoscopic, histological and radiographic criteria. Crohn's disease of the pouch was defined as involvement of the small bowel mucosa proximal to the ileal pouch with Crohn's disease, development of perianal complications or pouch fistula more than 3 months after ileostomy closure.

RESULTS

Positivity and level of Anti-GP2₁ IgG (AUC 0.77; P < 0.001 & P = 0.02, respectively), Anti-GP2₄ IgG (AUC 0.74; P < 0.001 & P = 0.025, respectively) and Anti-GP2₄ IgA (AUC 0.77; P < 0.001 to P = 0.018, respectively) were specifically associated with Crohn's disease of the pouch. Anti-GP2 was not associated with endoscopic or histological pouch disease activity index. Neither positivity nor levels of ASCA IgG (AUC 0.63; P = 0.12 & P = 0.35, respectively) or ASCA IgA (AUC 0.67; P = 0.38 & P = 0.53) were associated with pouch phenotypes.

CONCLUSIONS

The novel anti-GP2₁ and GP2₄ antibodies are associated with Crohn's disease of the pouch in ulcerative colitis patients after IPAA. Serological anti-GP2 antibodies could aid in diagnosis of Crohn's disease of the pouch.

Serologic Anti-GP2 Antibodies Are Associated with Genetic Polymorphisms, Fibrostenosis, and Need for Surgical Resection in Crohn's Disease

BACKGROUND

The presentation of Crohn's disease (CD) is heterogeneous and often leads to serious complications and need for surgery. We tested serum anti-zymogen granule glycoprotein 2 (GP2) antibodies, including its novel isoform alpha, for association with genetic variants, diagnosis, disease stratification, and prediction of CD courses in a combined cross-sectional and cohort study.

METHODS

Serum samples of 303 CD, 108 ulcerative colitis, 72 other inflammatory gastrointestinal diseases, and 206 controls without predominant gastrointestinal diseases controls (HC) were tested for the presence of Anti-GP2 and Anti-Saccharomyces cervisiae (ASCA) by enzyme-linked immunosorbent assay. Genetic analysis was performed using the Illumina Immunochip.

RESULTS

GP2 IgA and IgG had the highest discriminatory capability for CD versus ulcerative colitis and CD versus inflammatory gastrointestinal diseases. We identified an association of GP2 IgA and IgG each with 5 distinct single-nucleotide polymorphisms. Levels of anti-GP2 IgG were moderately associated with ileal disease location. Interestingly, both, anti-GP2 IgA and IgG were exclusively associated with the occurrence of stenosis and need for surgery, independently of disease location, but not with fistulizing CD, early disease onset or disease activity. ASCA IgG and IgA were qualitatively and quantitatively linked to CD, CD complications, and need for surgery. Increased levels of ASCA IgG and IgA and positivity for ASCA IgG, but neither levels nor positivity for GP2 IgG or IgA were predictive of the earlier occurrence of complications or surgery.

CONCLUSIONS

Anti-GP2 antibodies may aid as a tool for diagnosis and differentiation of CD and could indicate a more complicated CD course.

Systematic review: new serological markers (anti-glycan, anti-GP2, anti-GM-CSF Ab) in the prediction of IBD patient outcomes

Traditionally, IBD diagnosis is based on clinical, radiological, endoscopic, and histological criteria. Biomarkers are needed in cases of uncertain diagnosis, or to predict disease course and therapeutic response. No guideline recommends the detection of antibodies (including ASCA and ANCA) for diagnosis or prognosis of IBD to date. However, many recent data suggest the potential role of new serological markers (anti-glycan (ACCA, ALCA, AMCA, anti-L and anti-C), anti-GP2 and anti-GM-CSF Ab). This review focuses on clinical utility of these new serological markers in diagnosis, prognosis and therapeutic monitoring of IBD. Literature review of anti-glycan, anti-GP2 and anti-GM-CSF Ab and their impact on diagnosis, prognosis and prediction of therapeutic response was performed in PubMed/MEDLINE up to June 2014. Anti-glycan, anti-GP2 and anti-GM-CSF Ab are especially associated with CD and seem to be correlated with complicated disease phenotypes even if results differ between studies. Although anti-glycan Ab and anti-GP2 Ab have low sensitivity in diagnosis of IBD, they could identify a small number of CD patients not detected by other tests such as ASCA. Anti-glycan Abs are associated with a progression to a more severe disease course and a higher risk for IBD-related surgery. Anti-GP2 Ab could particularly contribute to better stratify cases of pouchitis. Anti-GM-CSF Ab seems to be correlated with disease activity and could help predict relapses. These new promising biomarkers could particularly be useful in stratification of patients according to disease phenotype and risk of complications. They could be a valuable aid in prediction of disease course and therapeutic response but more prospective studies are needed.