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Biochemical and Immunological Investigations of Food Allergy to Eggplant (Solanum Melongena L.)

Harish Babu, B. N. (2012) Biochemical and Immunological Investigations of Food Allergy to Eggplant (Solanum Melongena L.). PhD thesis, University of Mysore.

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Abstract

Food allergy refers to an immunologically (IgE) mediated adverse reaction to food allergens in sensitized individuals. Although, about one-third of the population, perceive that they are allergic to one or more foods, the actual prevalence of food allergy has been estimated to be 6-8% among children and 1-3% in adults. In recent times, the incidence of food allergy is alarmingly on rise and many foods are being implicated in food hypersensitive reactions with varied symptoms like mild itch to fatal systemic anaphylaxis, affecting various organ systems. Food allergens identified and studied so far are mostly proteins or glycoproteins. Vegetables and fruits are an important part of our diet, and some vegetables are increasingly being recognized as a cause of food allergy. Among the vegetables, the Solanaceae members (potato, tomato and bell pepper) have been studied with respect to their allergenicity and characterization of allergens. However, allergy to eggplant, an important vegetable of the same family has not been investigated with respect to characterization of allergens. Since eggplant is widely consumed in India, it is important to study allergic reactions to eggplant and to identify and characterize the allergens involved. The research work carried out forms the subject matter of the thesis. The thesis is divided into five chapters. Chapter 1 begins with a general account on food allergy and its mechanisms followed by an overview of the current literature on food allergens, allergy to fruits and vegetables with an emphasis on Solanaceous vegetables, diagnosis, causes and management of food allergy including future therapeutic options and food labelling. The chapter also highlights the aims and scope of the present study. Chapter 2 deals with screening for food allergy to eggplant in a random population in and around Mysore city to estimate the prevalence of eggplant allergy. Although 9.2% of the subjects reported adverse reactions to eggplant, the actual prevalence of IgE-mediated eggplant allergy was found to be 0.8% based on allergy diagnostic tests, with higher rates of sensitization (two times) in females than males. The female predominance (4:1) was more in the 16-30 year age group. Chapter 3 describes the detection and localization of allergens in different parts of eggplant (cv. Arka Shirish). Skin prick tests (SPT) and allergen-specific IgE with eggplant peel, pulp and fruit were positive in all the 6 eggplant-allergic subjects. IgE-immunoblots detected 9 (26, 28, 36, 43, 45, 54, 60, 64 and 71 kD), 3 (52, 60 and 71 kD) and 5 (36, 45, 60, 64 and 71 kD) allergenic proteins in the peel, pulp and fruit of the eggplant, respectively, demonstrating that eggplant is a multi-allergenic vegetable with a predominance of the allergens in the peel. Chapter 4 deals with the purification and characterization of eggplant allergens. The eggplant allergens were purified by phenyl-Sepharose chromatography. The 43, 64 and 71 kD proteins obtained in partially purified forms displayed strong IgE-binding ability. The 64 and 71 kD IgE-binding proteins displayed polyphenol oxidase (PPO) activity, presence of bound copper in the protein bands, and immunoreactivity with rabbit polyclonal antisweet potato PPO antiserum, clearly demonstrating their identification as PPO. Further, the 43, 45, 64 and 71 kD allergens are characterized as glycoproteins by periodic acid-Schiff (PAS) staining, of which 45, 64 and 71 kD show binding to Con A. The 64 and 71 kD allergens in the eggplant peel have been identified as polyphenol oxidases. Chapter 5 examines the stability of eggplant allergens to cooking and simulated gastric fluid (SGF) to study the epitope reactivity of the SGF-digested components. The SPT and allergen-specific IgE with cooked eggplant were positive in all the 6 eggplant- allergic subjects indicating the retention of IgE binding epitopes even after cooking. The 26, 28 and 36 kD allergens remained stable in the cooked eggplant extract as revealed by SDS-PAGE. Similarly, the SPT and allergen-specific IgE with SGF-digested components were positive in all the 6 eggplant-allergic subjects. The SDS-PAGE of SGF-digested eggplant peel extract showed that the 26, 36, 64 and 71 kD allergens appeared as faint but intact protein bands at 120 min of digestion and IgE-immunoblots following SGF-digestion showed that the 64 and 71 kD allergens displayed uniform IgE-binding at all time intervals from 0 to 120 min of digestion. A fairly good IgE-binding was observed in the 26 and 28 kD regions at 60 and 120 min of SGF digestion. Further, several low molecular weight fragments of parent allergens appearing after 10 min of digestion seem to retain IgE-binding epitopes in the IgE immunoblots. The thesis ends with a comprehensive summary and conclusions emphasizing the salient aspects of the present study.

Item Type: Thesis (PhD)
Uncontrolled Keywords: Food allergy, eggplant
Subjects: 600 Technology > 08 Food technology > 12 Allergy & Toxicology
600 Technology > 08 Food technology > 23 Vegetables
Divisions: Dept. of Biochemistry
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 13 Nov 2013 06:54
Last Modified: 13 Nov 2013 06:54
URI: http://ir.cftri.com/id/eprint/11287

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