Antibodies to Human Recombinant Tissue Transglutaminase Measured by Radioligand Assay: Evidence for High Diagnostic Sensitivity for Celiac Disease

Abstract

Celiac disease is associated with endomysial antibodies (EmA), which have recently been reported to be directed to tissue transglutaminase (tTG). To demonstrate binding of antibodies to recombinant tTG, human tTG was cloned, expressed by in vitro transcription/translation and used to develop novel radioligand assays for combined and single detection of immunoglobulin A (IgA) and G (IgG)-specific antibodies. IgA and IgG-tTGA were found in 43 (95.6%) of 45 patients with newly-diagnosed celiac disease verified by biopsy. In addition, all 30 sera from patients with gastrointestinal symptoms and positive EmA were positive for IgA-tTGA, and all but one serum (96.7%) had antibodies of the IgG class. Receiver-operating characteristic analysis including 574 sera from healthy controls revealed a specificity of 99.5%. By means of these new assays, we identified all patients with endomysial antibodies and achieved, at equal specificity, an even improved sensitivity (95.6%) as compared to EmA (91.1%) detected by the standard immunofluorescence test. Here, we have provided direct evidence that recombinant tTG is a major target of antibodies in celiac disease. Our data suggest that tTGA measured by radioligand assay have the power to overcome the limitations of the EmA-test. This new strategy may considerably facilitate large-scale screening for silent and latent celiac disease.

Recombinant Human Tissue Transglutaminase for Diagnosis and Follow-Up of Childhood Coeliac Disease

“…The presently used IgG anti-tTG ELISA exhibited a high sensitivity (91%) and specificity (96%), whereas other recent studies have reported a sensitivity between 21% and 98% (19,21,32). Detection of IgG anti-tTG antibodies may thus be useful for the diagnosis of celiac disease in patients with selective IgA deficiency (33); this issue needs to be further investigated.…”

Tissue transglutaminase autoantibody detection in human saliva: a powerful method for celiac disease screening

“…The second consideration was that among the several immunoassays developed to detect antitTG-Abs in CD, evidence indicated that those working in fluid-phase were the most specific and sensitive. This was probably a result of the presence of conformational domains in the tTG protein 37,38 that seem to be better preserved in fluidphase rather than in solid-phase procedures. 27 Previously, several attempts were made to detect salivary CD-specific antibodies, in particular AGA and EMA.…”

Autoantibodies as predictors of disease

“…17). Gliadin antibodies, both IgA and IgG, have been used in screening and have a sensitivity and specificity for prediction of celiac disease of 70-100%, but most of the relevant studies have been cross-sectional, testing established cases and controls; thus, these estimates are not true estimates of prediction but of identification (16,18,19). Serum reticulin antibodies, notably IgA antibodies against R1-type reticulin, have a sensitivity and specificity at diagnosis in excess of 90% (20).…”