Characterization of maize chitinase-A, a tough allergenic molecule

Authors: VOLPICELLA, MARIATERESA - University Of Bari; LEONI, CLAUDIA - University Of Bari; FANIZZA, IMMACOLATA - University Of Bari; DISTASO, MARCO - University Of Bari; LEONI, GUIDO - University Of Roma; FARIOLI, LAURA - Ospedale Niguarda; Naumann, Todd; PASTORELLO, ELIDE - Ospedale Niguarda; CECI, LUIGI - National Research Council - Italy

Submitted to: Allergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2017
Publication Date: 3/22/2017
Citation: Volpicella, M., Leoni, C., Fanizza, I., Distaso, M., Leoni, G., Farioli, L., Naumann, T., Pastorello, E., Ceci, L.R. 2017. Characterization of maize chitinase-A, a tough allergenic molecule. Allergy. 72(9):1423-1429. https://doi.org/10.1111/all.13164.
DOI: https://doi.org/10.1111/all.13164

Interpretive Summary: Food allergies are caused by stable proteins in food that resist digestion. Corn does not usually cause food allergies, but does in some people. Since it is a less common cause of food allergies there has not been much work done to determine which corn proteins are allergenic. In this work scientists in the Mycotoxin Prevention and Applied Mycology Research Unit, Peoria, Illinois, in collaboration with scientists at the National Research Council of Italy, Bari, Italy, identified a seed chitinase as one protein that contributes to corn allergies. The chitinase was recognized by antibodies from patients with corn allergies and it was shown that the chitinase is stable to acid and heat, a common property of allergenic proteins. Uncovering the structural basis of allergenicity would allow improvements in the diagnosis and therapy of allergies and would provide insights for understanding the effects of food processing, contributing to a safer management of food allergens.

Technical Abstract: Food allergies are recognized as an increasing health concern. Proteins commonly identified as food allergens tend to have one of about 30 different biochemical activities. This leads to the assumption that food allergens must have specific structural features which causes their allergenicity. But these structural features are not completely understood. Uncovering the structural basis of allergenicity would allow improved diagnosis and therapy of allergies and would provide insights for safer food production. The availability of recombinant food allergens can accelerate their structural analysis and benefit specific studies in allergology. Plant chitinases are an example of food allergenic proteins for which structural analysis of allergenicity has only partially been reported. The recombinant maize chitinase, rChiA, was purified from Pichia pastoris extracellular medium by differential precipitation and cation exchange chromatography. Enzyme activity was evaluated by halo-assays and microcalorimetric procedures. rChiA modeling was performed by a two-step procedure, using the Swiss-Model server and Modeller software. Allergenicity of rChiA was verified by immunoblot assays with sera from allergic subjects. rChiA is active in the hydrolysis of glycol chitin and tetra-N-acetylchitotetraose and maintains its activity at high temperatures (70°C) and low pH (pH 3). The molecule is also reactive with IgE from sera of maize-allergic subjects. rChiA is a valuable molecule for further studies on structure-allergenicity relationships and as a tool for diagnosing allergies.