Surface Plasmon Resonance imaging: A method to measure the affinity of the antibodies in allergy diagnosis

Aim: The biological diagnosis of type I hypersensitivity reactions is based on the quantification of specific IgEs. However, the IgE titer is not always strongly related to the clinical symptoms or predictive of the evolution of the disease. The specificity and affinity of antibodies of other isotypes may contribute to the allergic status of the patients. The aim of the present work was to develop a method that simultaneously detects the complex antibody response to various allergens and measures the avidity of the antibodies directed to each allergen. Methods: A chip based on a covalent binding of 3 major milk allergens on a gold-activated surface was developed. The binding of specific antibodies to alpha-lactalbumin,beta-lactoglobulin or caseins was monitored using Surface Plasmon Resonance imaging (SPRi). The sensitivity and specificity of the method were compared to those obtained by ELISA, the reference method. Results: The specificity of the antibodies characterized by SPRi was identical to the one obtained by ELISA. The intensity of the signal was proportional to the quantity of antibodies bound to each allergen. The sensitivity of the SPRi detection was about 8-10 times lower than for ELISA but the SPRi is faster and the analysis of association/dissociation kinetics allowed the determination of the avidity of the antibody response. Conclusion: The present study shows that SPRi allows a multiplex monitoring of the complex antibody response to the major allergens of an allergenic source. This label-free method constitutes a new tool that may be added to IgE detection to improve allergy diagnosis. (C) 2014 Elsevier B.V. All rights reserved.