IN-VITRO TOXICITY OF PURIFIED GLUTEN PEPTIDES TESTED BY ORGAN-CULTURE

Various subfractions of Frazer fraction III were separated by high-pressure liquid chromatography, and their toxicity in vitro (organ culture) was tested in comparison with alpha-gliadin using duodenal biopsies from 25 patients with active celiac disease and subtotal villous atrophy, 2 patients with partial villous atrophy, and 10 nonceliac controls. One dominating fraction, designated Frazer III-2-VIII, was purified by several steps of rechro-matography. It was markedly toxic to duodenal explants from patients with active celiac disease. The mean enterocyte height after culture was 15.9 mu m compared with 25.6 mu m in gluten-free medium. This difference was statistically significant in all cases except one, in which the lowest concentration (110 mu g) was used. The in vitro toxicity of Frazer III-2-VIII was comparable with the toxicity of cr-gliadin in twofold to fivefold higher concentrations. No toxicity could be detected in nonceliac explants (mean enterocyte height, 25.7 vs. 24.9 mu m in gluten-free medium). The N-terminal amino acid sequence was (Gin)Ile- Gln-Val-Phe-Pro-Ser-Gly-Gln-Vlr-Gln-(Trp)-Pro-Gln-Gln-(Gln)-Gln-Pro-Phe-Pro- . This sequence was not homologous to previously reported sequences of toxic gluten peptides. By use of the SwissProt and GenEMBL databases, it was concluded that the peptide Frazer III-2-VIII is part of the gamma-gliadin fraction.