The Development and Validation of a Novel Gluten ELISA Kit Based on Monoclonal Antibodies Configured in Competitive Format

Introduction: In an effort to address growing public health concerns regarding gluten intolerance, the FDA and TTB have recently established regulatory threshold limits for gluten content in foods and alcoholic beverages labeled "gluten-free." Implementation and observance of these labeling laws require the use of antibody-based methodologies that can accurately quantify gluten levels in different food matrices. However, accurate quantification from fermented and/or hydrolyzed food products is problematic using conventional assay formats.

Purpose: To develop a rapid and accurate competitive ELISA kit for measurement of gluten residues derived from hydrolyzed and/or fermented wheat, barley, and rye food products.

Methods: Polyclonal antibodies were raised against prolamin fractions derived from wheat, rye, and barley. The polysera from these individually immunized goats were immunopurified on gluten-based affinity columns and then blended. The antibodies were then used to develop a competitive ELISA for the detection of gluten (wheat, barley, and rye) from complex food matrices including beer and sourdough. The finalized kit was validated using native and hydrolyzed gluten sources and then compared with a commercial competitive Gluten ELISA kit based on R5 monoclonal antibodies.

Results: We report that the MEI/IEH competitive ELISA kit could quantitatively detect gluten residues derived from wheat, barley, and rye within a range of quantification 1.5-100 ppm, R² = 0.9801, with near-stoichiometric detection for all three targets. The kit broadly detected distinct varieties of wheat, barley, and rye and did not cross-detect proteins derived from soy, sorghum, corn, lupin, or oats. The test method was performed in 36 min (extraction and assay operation). Method concordance with the R5-based kit demonstrated similar ability to detect hydrolyzed gluten residues in real food matrices, without concerns for over-estimation of hordein (barley). 

Significance: This kit establishes a rapid and accurate method to detect hydrolyzed gluten residues in fermented foods and beverages in keeping with the regulations set forth recently by the FDA and TTB governing allowable gluten content in foods labeled “gluten-free.” Implementation of this kit should particularly benefit the food and beverage industries by providing a more accurate measurement of hydrolyzed barley residues.