Gluten, Celiac Disease, and Gluten Intolerance and the Impact of Gluten Minimization Treatments with Prolylendopeptidase on the Measurement of Gluten in Beer

Abstract

There is an increase in the number of people adopting a gluten-free diet, with one-fifth of Australian consumers avoiding certain food or drinks for allergy or intolerance reasons. For most consumers, the belief that a gluten-free diet is healthier than a gluten containing diet is unsupported by a formal diagnosis. However, for a small group of subjects who have gluten sensitive disorder, a lifelong, gluten-free diet is required, including avoidance of beer. Prolylendopeptidase enzymes (PEP) cleave gluten proteins after the abundant proline residues and have the potential to destroy gluten proteins and remove or minimize immunoreactive peptides from food. However, PEP treatment may also confound measurement of gluten concentration in food and beverages by destroying epitopes that are used to enumerate gluten peptides – we ask, “does PEP treatment destroy celiac reactive epitopes or merely disguise them from ELISA enumeration?” There is now sufficient data to show that treatment of gluten peptides with bacterial PEP in combination with other proteases, or the fungal Aspergillus niger PEP alone, reduces the immunoreactivity of gluten peptides, with celiac T-cells to near zero. This is also accompanied by destruction of key epitopes that are used by antibodies to enumerate gluten peptides during ELISA reactions. Thus, both immunoreactivity and ELISA measurements are reduced to near zero by PEP treatment. However, definitive evidence of the safety of treated beer for celiacs ideally requires a double-blind crossover, dietary challenge. Consuming sufficient beer to present a suitable load of hordein peptides is not possible, and presenting hordeins in the same form as encountered in treated beer is difficult. The effect of protease treatments on the safety of treated gluten for the remainder the celiac-like diseases, including gluten ataxia and dermatitis herpetiformis, and the larger spectrum of gluten-related disorders, including gluten intolerance and the IgE-mediated allergic responses Bakers asthma, gluten allergy, WDEIA, and urticaria, cannot be definitively assessed until the epitopes involved have been defined. The gluten sensitive disorders and the gluten proteins are reviewed, and the effects of proteolysis on several archetypal gluten peptides are examined.

• Beer
• celiac disease
• gluten
• hordeins
• prolylendopeptidase