Serologic assay based on gliadin-related nonapeptides as a highly sensitive and specific diagnostic aid in celiac disease.
BACKGROUND
Celiac disease (CD) is induced by wheat gliadins and related cereal proteins. Anti-gliadin antibodies (AGAs) are present in the serum of CD patients, but these antibodies have lower diagnostic specificity and sensitivity than autoantibodies [anti-endomysium antibodies (AEmAs) and anti-tissue transglutaminase antibodies (AtTGAs)]. Recently, AGAs from CD patients were found to recognize deamidated gliadin peptides, probably formed by the action of tissue transglutaminase.


METHODS
We synthesized several gliadin peptides and their glutamine-glutamic acid-substituted counterparts on cellulose membranes and tested their recognition by IgA in sera of 52 AEmA-positive CD patients and 76 AEmA-negative controls in a luminescence assay. For comparison, we assayed IgA concentrations of AGAs, AtTGAs, and AEmAs. For measurement of AtTGAs, we used the human recombinant antigen.


RESULTS
We identified several nonapeptides that were detected with high specificity by IgA in CD patients. Diagnostic accuracy of the peptide antibody assay was highest when peptide PLQPEQPFP was used in combination with peptide PEQLPQFEE within one assay. AGAs were above the cutoff in 14 of the controls, but only 5 of the controls were positive for peptide antibodies. For comparison, 82% and 94% of samples were correctly classified by AGAs and the combination nonapeptide assay, respectively (P = 0.007), and the AtTGAs correctly classified 98%.


CONCLUSIONS
The peptide antibody assay has higher diagnostic accuracy than AGAs for distinguishing patients with CD from controls, and has diagnostic accuracy similar to that of AtTGAs.
Institute of Laboratory Medicine, Clinical Chemistry and Molecular Diagnostics, Institute of Clinical Immunology, University Hospital, Leipzig, Germany.
Elke
E
Schwertz
Franka
F
Kahlenberg
Ulrich
U
Sack
Thomas
T
Richter
Martin
M
Stern
Karsten
K
Conrad
Klaus-Peter
KP
Zimmer
Thomas
T
Mothes
D000293:Adolescent; D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood; D002446:Celiac Disease / Q000175:diagnosis* / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005455:Fluorescent Antibody Technique; D005903:Gliadin / Q000737:chemistry* / Q000276:immunology; D006801:Humans; D007124:Immunoenzyme Techniques; D007070:Immunoglobulin A / Q000097:blood; D007223:Infant; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides / Q000737:chemistry* / Q000276:immunology; D012680:Sensitivity and Specificity
D001323:Autoantibodies; D007070:Immunoglobulin A; D009842:Oligopeptides; D005903:Gliadin