Monoclonal antibody R5 for detection of putatively coeliac-toxic gliadin peptides

Monoclonal antibody R5 against rye secalin was recently suggested to be useful in analysis of gluten in food. The epitope specificity of R5 was characterized and compared with those of eight other monoclonal antibodies (mabs) against gliadins (gli) and secalins. Mabs were tested for binding to synthetic peptides spanning in overlapping manner sequences of gli. In a luminescence assay R5 bound to all peptides from the N-terminal part of α-type gli hitherto known to induce in sensitive patients with coeliac disease after in vivo instillation. Thus, R5 proves to be very useful for gluten analysis. Sequences QQPFP, QQQFP, LQPFP, and QLPFP were bound most strongly. Substitution of glutamine by glutamic acid in the epitope may decrease binding of R5 dependent on surrounding amino acids. One of the positions of the substitutions diminishing antibody binding was a typical site of attack of tissue transglutaminase, the enzyme converting by deamidation cereal prolamins into their disease active form. Investigation of eight other mabs against gli and secalins showed binding properties very similar to R5. We speculate the sequence QQQ/PFP seems to represent an immunodominant structure in prolamins. An erratum to this article can be found at