Progress Report for 2005
To accomplish our goals as efficiently as possible, we have maintained a substantial laboratory effort to examine the role of an enzyme called prolyl endopeptidase (PEP) in the digestion of gluten fragments (called gliadin peptides) that are formed in the normal process of digestion in the stomach and small intestine. Unlike other proteins which are broken down into very small pieces (e.g. 2 or 6 amino-acids long) by gastric, intestinal, and pancreatic enzymes, gluten is highly resistant to digestion. Therefore, many of the resulting gliadin peptide products are quite large (e.g., up to 33 amino-acids in length; by comparison, undigested wheat gliadin itself is 10 times larger, typically 330 amino-acids long). In Celiac patients, these gliadin peptide products are toxic.
Our studies established that PEP further breaks down the digestive-resistant gliadin peptides in regular gluten-containing flour to smaller non-toxic products (Thomas Marti and our group in collaboration with our colleagues Drs. Molberg and Sollid from the University of Oslo) [1]. In studies with Celiac Sprue patient volunteers, coordinated by Dr. Gail Pyle 2 , 3 in collaboration with our colleagues at the Palo Alto Research Foundation, symptom- free Celiac patients on gluten exclusion who ate 5 grams per day of grocery store gluten pre-treated with the PEP peptidase did not develop the malabsorption of fat and carbohydrate that was induced in these same patients by the same amount of dietary gluten untreated with the PEP. In the process of carrying out this food gluten detoxification study, we also discovered that 50% of the Celiacs who were free of gastrointestinal symptoms on a gluten-free diet still had malabsorption of nutrients such as fat and carbohydrate. This suggests that full dietary gluten exclusion may be difficult to achieve in many patients.
Jon Gass, a graduate student Chemical Engineering in Dr. Chaitan Khosla's group supported by the Foundation in collaboration with colleagues from Formatech, Inc., has been able to establish a preliminary formulation of the PEP in a capsule form 4 that he is now testing in small animals.
The finding that ongoing intestinal dysfunction is common in asymptomatic Celiac patients emphasizes that it is crucial 1) to improve the management of this chronic illness, and 2) to come forth with suitable supplemental therapy for this intestinal disease. In a concerted effort to bring this to fruition, the Foundation has supported the initiation of a special Celiac Management Clinic at Stanford University Medical Center beginning in January 2005 (see Celiac Management Clinic above).
1. Marti, T., Molberg, O., Li, Q., Gray, G.M., Khosla, C., and Sollid, L.M. Prolyl endopeptidase mediated destruction of T cell epitopes in whole gluten- Chemical and immunological characterization. J. Pharmacol. Exp. Therapeutics 312, 19-26, 2005.
2. Pyle, G.G., Paaso, B., Anderson, B.E., Allen, D.D., Marti, T., Khosla, C., and Gray, G.M. Low-dose gluten challenge in Celiac Sprue: Malabsorptive and antibody responses. Clin. Gastroenterol. Hepatol. 3, 679-686, 2005.
3. Pyle, G.G., Paaso, B., Anderson, B.E., Allen, D.D., Marti, T., Li, Q., Siegel, M., Khosla, C., and Gray, G.M. Pre-treatment of food gluten with prolyl endopeptidase (PEP) avoids gluten-induced malabsorption in Celiac Sprue. Clin. Gastroenterol. Hepatol. 3, 687-694, 2005.
4 . Gass, J., Ehren, J., Strohmeier, G., Isaacs, I., and Khosla, C. Fermentation, purification, formulation and pharmacological evaluation of a prolyl endopeptidase from Myxococcus xanthus: Implications for Celiac Sprue therapy. Biotechnol. Bioeng . 92, 674-684, 2005.
