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Crohn's disease (CD) is an inflammatory bowel disease (IBD) characterized by reactivity against microbial and self antigens. Zymogen granule glycoprotein 2 (GP2) was identified as the major autoantigen of CD-specific pancreatic autoantibodies (PAB).Human GP2 was expressed in the Spodoptera frugiperda 9 (Sf9) cell line using the baculovirus system, purified by Ni-chelate chromatography, and used as antigen for anti-GP2 IgA and IgG assessment by enzyme-linked immunosorbent assays (ELISA). Antibodies to mannan of Saccharomyces cerevisiae (ASCA), PAB, and anti-GP2 were investigated in sera of 178 CD patients, 100 ulcerative colitis (UC) patients, and 162 blood donors (BD).Anti-GP2 IgG and IgA were found in 48/72 (66.7%) and 23/72 (31.9%) PAB positive and 5/106 (4.7%) and 1/106 (0.9%) PAB negative CD patients (p0.0001), respectively. CD patients displayed significantly higher reactivity to GP2 than UC patients and BD (p0.0001), respectively. Occurrence of anti-GP2 antibodies correlated with PAB reactivity (Spearmen's rho=0.493, p0.00001). There was a significant relationship between the occurrence of ASCA IgG and anti-GP2 IgG (p=0.0307).Anti-GP2 IgG and IgA constitute novel CD specific autoantibodies, the quantification of which could improve the serological diagnosis of IBD.

Background The liver-specific ASGPR is an autoantigen in autoimmune hepatitis (AIH) patients. Anti-ASGPR antibody correlates with disease activity, however, only in-house assays have been reported so far. Methods Rabbit ASGPR was purified by affinity chromatography on galactose-Sepharose and used for standardised detection of anti-ASGPR by ELISA. Anti-ASGPR IgG was measured in sera from 45 patients with AIH, PBC ( n = 43), alcoholic liver disease ( n = 13), HBV infection ( n = 35), HCV infection ( n = 53), and 118 blood donors. Anti-ASGPR was correlated with biochemical parameters of disease activity in 22 AIH patients with consecutive samples. Results Twenty-one of 30 untreated (70%) and five of 15 treated AIH patients (30%) showed elevated anti-ASGPR at first presentation. Only one blood donor demonstrated anti-ASGPR. ALD and PBC patients were all negative. ROC curve analysis of AIH and disease-control patients revealed a sensitivity of 77.8% and a specificity of 99.4%. Three (8.6%) of 35 HBV and 7 (13.2%) of 53 HCV patients demonstrated elevated anti-ASGPR. In AIH patients, anti-ASPGR correlated with liver-transaminases levels. In 22 follow-up patients, elevation of anti-ASPGR preceded liver-transaminases increase. Conclusions The novel anti-ASGPR ELISA is a readily available and specific diagnostic tool for anti-ASGPR detection in AIH. Quantification of anti-ASGPR is helpful in monitoring disease activity.