Recombinant human tissue transglutaminase ELISA for the diagnosis of gluten-sensitive enteropathy.

BACKGROUND Tissue transglutaminase (TGc) has recently been identified as the major, if not the sole, autoantigen of gluten-sensitive enteropathy (GSE). We developed and validated an ELISA based on the human recombinant antigen and compared it to existing serological tests for GSE [guinea pig TGc ELISA and endomysium antibody (EMA) test]. METHODS Human TGc was expressed in the human embryonic kidney cell line 293-EBNA as a C-terminal fusion protein with the eight-amino acid Strep-tag II allowing one-step purification via streptavidin affinity chromatography. We carried out ELISA assays for IgA antibodies against TGc using calcium-activated human and guinea pig TGc. The sera were also tested on monkey esophagus sections by indirect immunofluorescence for IgA EMA. We examined 71 serum samples from patients with GSE (38 with celiac disease, 33 with dermatitis herpetiformis), including 16 on therapy, and 53 controls. RESULTS The human TGc could be expressed and purified as an active enzyme giving a single band on a Coomassie-stained gel. The mean intra- and interassay CVs for the human TGc ELISA were 3.2% and 9.2%, respectively. The area under the ROC curve was 0.999. The specificity and sensitivity were 98.1% (95% confidence interval, 95.7-100%) and 98.2% (95.9-100%), respectively. CONCLUSIONS The human TGc ELISA was somewhat superior to the guinea pig TGc ELISA, and was as specific and sensitive as the EMA test. The human TGc-based ELISA is the method of choice for easy and noninvasive screening and diagnosis of GSE.