Selective inhibition of the gliadin-specific, cell-mediated immune response by transamidation with microbial transglutaminase

CD is an immune-mediated enteropathy caused by the ingestion of wheat gluten. The modification of gluten by intestinal tTGase plays a crucial role in CD pathogenesis. In this study, we observed that extensive transamidation of wheat flour with K-C2H5 by mTGase yielded spf and K-gliadins fractions. By Western blot, we found that these modifications were associated with strongly reduced immune cross-reactivity. With the use of DQ8 tg mice as a model of gluten sensitivity, we observed a dramatic reduction in IFNγ production in gliadin-specific spleen cells challenged with spf and K-gliadins in vitro (n=12; median values: 813 vs. 29 and 99; control vs. spf and K-gliadins, P=0.012 for spf, and P=0.003 for K-gliadins). For spf, we also observed an increase in the IL-10/IFNγ protein ratio (n=12; median values: 0.3 vs. 4.7; control vs. spf, P=0.005). In intestinal biopsies from CD patients challenged in vitro with gliadins (n=10), we demonstrated further that K-gliadins dramatically reduced the levels of antigen-specific IFNγ mRNA in all specimens responsive to native gliadins (four of 10; P<0.05). As cytotoxic effects have been described for gliadins, we also studied GST and caspase-3 activities using the enterocytic Caco-2 cell line. We found that neither activities were modified by flour transamidation. Our results indicate that K-C2H5 cross-linking via mTGase specifically affects gliadin immunogenicity, reversing the inducible inflammatory response in models of gluten sensitivity without affecting other aspects of the biological activity of gliadins.