THE ACTIVITY OF WHEAT GLIADIN PEPTIDES IN INVITRO ASSAYS FOR CELIAC-DISEASE

A fraction of a peptic-tryptic-pancreatinic digest of wheat gliadin (f raction 9), known to be toxic to individuals with coeliac disease, tog ether with synthetic peptides containing key gliadin sequences, were t ested for their effects on foetal chick intestine and on rat liver lys osomes. Fraction 9 and a dodecapeptide corresponding to residues 75-86 of A-gliadin (RPQQPYPQPQPQ) were the only peptides to display appreci able activity in both assays. A synthetic hexapeptide corresponding to residues 77-82 was only weakly toxic to lysosomes and non-toxic to ch ick duodenum. A decapeptide corresponding to residues 76-85 was non-to xic in both assays. Two serine-containing peptides containing the key sequence PSQQ were also tested but were found to be non-toxic, as was the hexapeptide PSQQQP. The results suggest that the key sequences QQQ P and PSQQ are not sufficient by themselves to cause activity. Further tests on synthetic peptides will be necessary to define the sequences of highest toxicity.