Suzanne S. Teuber

Work Group report: Oral food challenge testing

Oral food challenges are procedures conducted by allergists/immunologists to make an accurate diagnosis of immediate, and occasionally delayed, adverse reactions to foods. The timing of the challenge is carefully chosen based on the individual patient history and the results of skin prick tests and food specific serum IgE values. The type of the challenge is determined by the history, the age of the patient, and the likelihood of encountering subjective reactions. The food challenge requires preparation of the patient for the procedure and preparation of the office for the organized conduct of the challenge, for a careful assessment of the symptoms and signs and the treatment of reactions. The starting dose, the escalation of the dosing, and the intervals between doses are determined based on experience and the patients history. The interpretation of the results of the challenge and arrangements for follow-up after a challenge are important. A negative oral food challenge result allows introduction of the food into the diet, whereas a positive oral food challenge result provides a sound basis for continued avoidance of the food.

Standardizing double-blind, placebo-controlled oral food challenges : American Academy of Allergy, Asthma & Immunology-European Academy of Allergy and Clinical Immunology PRACTALL consensus report

Hugh A. Sampson, MD, Roy Gerth van Wijk, MD, Carsten Bindslev-Jensen, MD, PhD, Scott Sicherer, MD, Suzanne S. Teuber, MD, A. Wesley Burks, MD, Anthony E. J. Dubois, MD, Kirsten Beyer, MD, Philippe A. Eigenmann, MD, Jonathan M. Spergel, MD, PhD, Thomas Werfel, MD, and Vernon M. Chinchilli, PhD New York, NY, Rotterdam and Groningen, The Netherlands, Odense, Denmark, Davis, Calif, Chapel Hill, NC, Berlin and Hannover, Germany, Geneva, Switzerland, and Philadelphia and Hershey, Pa

Food allergy: a practice parameter

TABLE OF CONTENTS I. Preface S1 II. Glossary S2 III. Executive Summary S3 IV. Summary Statements S6 V. Classification of Major Food Allergens and Clinical Implications S11 VI. Mucosal Immune Responses Induced by Foods S12 VII. The Clinical Spectrum of Food Allergy S15 VIII. Algorithm and Annotations S18 IX. Prevalence and Epidemiology S21 X. Natural History of Food Allergy S22 XI. Risk Factors and Prevention of Food Allergy S23 XII. Cross-reactivity of Food Allergens S24 XIII. Adverse Reactions to Food Additives S30 XIV. Genetically Modified Foods S32 XV. Diagnosis of Food Allergy S33 XVI. Food-Dependent Exercise-Induced Anaphylaxis S39 XVII. Differential Diagnosis of Adverse Reactions to Foods S40 XVIII. General Management of Food Allergy S44 XIX. Management in Special Settings and Circumstances S45 XX. Future Directions S47 XXI. Appendix: Suggested Oral Challenge Methods S48 XXII. Acknowledgments S49 XXIII. References S50

Tree Nut Allergens

Allergic reactions to tree nuts can be serious and life threatening. Considerable research has been conducted in recent years in an attempt to characterize those allergens that are most responsible for allergy sensitization and triggering. Both native and recombinant nut allergens have been identified and characterized and, for some, the IgE-reactive epitopes described. Some allergens, such as lipid transfer proteins, profilins, and members of the Bet v 1-related family, represent minor constituents in tree nuts. These allergens are frequently cross-reactive with other food and pollen homologues, and are considered panallergens. Others, such as legumins, vicilins, and 2S albumins, represent major seed storage protein constituents of the nuts. The allergenic tree nuts discussed in this review include those most commonly responsible for allergic reactions such as hazelnut, walnut, cashew, and almond as well as those less frequently associated with allergies including pecan, chestnut, Brazil nut, pine nut, macadamia nut, pistachio, coconut, Nangai nut, and acorn.

Cloning and sequencing of a gene encoding a 2S albumin seed storage protein precursor from english walnut (Juglans regia), a major food allergen

BACKGROUND Walnuts rank third in per capita consumption of tree nuts in the United States and can be associated with systemic IgE-mediated reactions in some individuals. OBJECTIVE The objectives of the study were to clone a gene encoding one of the major food allergens in the walnut kernel and to characterize the recombinant allergen. METHODS A cDNA expression library in the lambda vector Uni-ZAP, which was prepared from walnut somatic embryos, was screened by using a patients sera that reacted with multiple protein bands on immunoblotting. RESULTS A cDNA clone containing an insert of 663 bp was identified and named Jug r 1. DNA sequence analysis of this clone revealed that it encoded a protein 142 amino acids in length. Comparison of the encoded protein sequences with protein databases revealed that this clone exhibits a 46.1% identity with the Brazil nut (Bertholletia excelsa) methionine-rich 2S albumin seed storage protein precursor, Ber e 1. Jug r 1 appears to be an important walnut food allergen; 12 of 16 sera from patients allergic to walnuts demonstrated IgE binding to the 2S albumin seed storage protein precursor fusion protein. An IgE-binding inhibition study suggests that the walnut 2S protein precursor undergoes posttranslational modification into a large and small subunit that is similar to castor seed, cottonseed, mustard seed, and Brazil nut 2S seed storage protein allergens. Interestingly, the gene encoding this allergenic protein in Brazil nuts has recently gained notoriety because of its experimental use as a transgene to enhance the nutritional quality of legumes. CONCLUSION This is now the sixth definitive 2S albumin seed storage protein demonstrated to bind IgE, suggesting that this class of proteins is inherently allergenic.

Identification and cloning of a complementary DNA encoding a vicilin-like proprotein, Jug r 2, from English walnut kernel (Juglans regia), a major food allergen

BACKGROUND Walnuts and other tree nuts are important food-allergen sources that have the potential to be associated with life-threatening, IgE-mediated systemic reactions in some individuals. OBJECTIVE The purpose of this study was to characterize a complementary (c)DNA clone encoding one of the walnut food allergens. METHODS A cDNA expression library prepared from walnut somatic embryo was screened for IgE reactivity with patient serum. A reactive clone of 2060 bp, which encoded a protein of 593 amino acids in length, was subcloned by excision into the pGEX expression vector. IgE-binding inhibition experiments were performed. RESULTS A recombinant fusion protein was induced and shown to bind serum IgE from 9 of 15 patients tested, thus identifying a major allergen. This clone, named Jug r 2, exhibited significant homology with genes encoding the vicilin group of seed proteins. An IgE-binding inhibition experiment suggested that the encoded protein undergoes posttranslational modification into at least one major polypeptide (47 kd) and possibly several others, which is similar to the vicilin-like proteins characterized in cocoa bean (Theobroma cacao) and cottonseed (Gossypium hirsutum). N-terminal sequencing of the 47-kd band, Jug r 2, identified it as a mature protein obtained from the precursor. A second IgE-binding inhibition experiment showed that there is minimal or no cross-reactivity between Jug r 2 and pea vicilin, peanut proteins, or cacao proteins. CONCLUSION Jug r 2 is the third vicilin food allergen identified in addition to vicilins from soy and peanut. The availability of recombinant food allergens should help advance studies on the immunopathogenesis and possible treatment of IgE-mediated food hypersensitivity.

Ana o 2, a Major Cashew (Anacardium occidentale L.) Nut Allergen of the Legumin Family

Background: We recently cloned and described a vicilin and showed it to be a major cashew allergen. Additional IgE-reactive cashew peptides of the legumin group and 2S albumin families have also been reported. Here, we attempt to clone, express and characterize a second major cashew allergen. Methods: A cashew cDNA library was screened with human IgE and rabbit IgG anti-cashew extract antisera, and a reactive nonvicilin clone was sequenced and expressed as a fusion protein in Escherichia coli. Immunoblotting was used to screen for reactivity with patients’ sera, and inhibition of immunoblotting was used to identify the corresponding native peptides in cashew nut extract. The identified allergen was subjected to linear epitope mapping using SPOTs solid-phase synthetic peptide technology. Results: Sequence analysis showed the selected clone, designated Ana o 2, to encode for a member of the legumin family (an 11S globulin) of seed storage proteins. By IgE immunoblotting, 13 of 21 sera (62%) from cashew-allergic patients were reactive. Immunoblot inhibition data showed that the native Ana o 2 constitutes a major band at approximately 33 kD and a minor band at approximately 53 kD. Probing of overlapping synthetic peptides with pooled human cashew-allergic sera identified 22 reactive peptides, 7 of which gave strong signals. Several Ana o 2 epitopes were shown to overlap those of the peanut legumin group allergen, Ara h 3, in position but with little sequence similarity. Greater positional overlap and identity was observed between Ana o 2 and soybean glycinin epitopes. Conclusions: We conclude that this legumin-like protein is a major allergen in cashew nut.

Clinical Significance of Complement Deficiencies

The complement system is composed of more than 30 serum and membrane‐bound proteins, all of which are needed for normal function of complement in innate and adaptive immunity. Historically, deficiencies within the complement system have been suspected when young children have had recurrent and difficult‐to‐control infections. As our understanding of the complement system has increased, many other diseases have been attributed to deficiencies within the complement system. Generally, complement deficiencies within the classical pathway lead to increased susceptibility to encapsulated bacterial infections as well as a syndrome resembling systemic lupus erythematosus. Complement deficiencies within the mannose‐binding lectin pathway generally lead to increased bacterial infections, and deficiencies within the alternative pathway usually lead to an increased frequency of Neisseria infections. However, factor H deficiency can lead to membranoproliferative glomerulonephritis and hemolytic uremic syndrome. Finally, deficiencies within the terminal complement pathway lead to an increased incidence of Neisseria infections. Two other notable complement‐associated deficiencies are complement receptor 3 and 4 deficiency, which result from a deficiency of CD18, a disease known as leukocyte adhesion deficiency type 1, and CD59 deficiency, which causes paroxysmal nocturnal hemoglobinuria. Most inherited deficiencies of the complement system are autosomal recessive, but properidin deficiency is X‐linked recessive, deficiency of C1 inhibitor is autosomal dominant, and mannose‐binding lectin and factor I deficiencies are autosomal co‐dominant. The diversity of clinical manifestations of complement deficiencies reflects the complexity of the complement system.

Systemic allergic reaction to coconut (Cocos nucifera) in 2 subjects with hypersensitivity to tree nut and demonstration of cross-reactivity to legumin-like seed storage proteins: new coconut and walnut food allergens.

BACKGROUND Two patients with tree nut allergy manifested by life-threatening systemic reactions reported the subsequent onset of systemic reactions after the consumption of coconut. OBJECTIVE Herein, the IgE-binding proteins from coconut are described, and in vitro cross-reactivity with other nuts is investigated. METHODS The IgE-binding profile of coconut endosperm tissue extract was analyzed by SDS-PAGE followed by immunoblotting. Immunoblot inhibition studies with walnut, almond, peanut, and coconut were performed. RESULTS Sera IgE from both patients recognized reduced coconut allergens with molecular weights of 35 and 36.5 kd. IgE from 1 patient also bound a 55-kd antigen. Preabsorption of sera with nut extracts suppressed IgE binding to coconut proteins. Preabsorption of sera with coconut caused the disappearance of IgE binding to protein bands at 35 and 36 kd on a reduced immunoblot of walnut protein extract in 1 patient and suppression of IgE binding to a protein at 36 kd in the other patient. CONCLUSION The reduced coconut protein at 35 kd was previously shown to be immunologically similar to soy glycinin (legumin group of seed storage proteins). The clinical reactivity in these 2 patients is likely due to cross-reacting IgE antibodies primarily directed against walnut, the original clinical allergy reported, and most likely to a walnut legumin-like protein. Coconut allergy in patients with tree nut allergy is rare; these are the first 2 patients ever reported, and therefore there is no general indication to advise patients with tree nut allergy to avoid coconut.

Food allergy diagnostics: scientific and unproven procedures.

Purpose of reviewThe accurate diagnosis of food allergy is crucial not only for the right treatment but also for the avoidance of unnecessary diets. The diagnostic work-up of suspected food allergy includes the measurement of food-specific IgE antibodies using serologic assays, the skin prick test, elimination diets and oral provocation tests. In addition, some approaches are either under further rigorous investigation (the atopy patch test) or are already in widespread use, particularly by practitioners of alternative or complementary medicine, but are considered unproven. These diagnostic methods include specific IgG to foods, provocation/neutralization testing, kinesiology, cytotoxic tests and electrodermal testing. This review covers some of the most common scientifically validated and unproven approaches used in the diagnosis of food allergy. Recent findingsFor specific serum IgE and the SPT, decision points have been established for some foods, allowing prediction of clinical relevance. The APT may be helpful, especially when considered in combination with defined levels of specific IgE. In regard to other approaches, most scientific studies do refute the usefulness of these approaches. SummaryIn most patients, controlled oral food challenges remain the gold standard in the diagnostic work-up of suspected food allergy. The skin prick test and measurement of specific IgE antibodies to food extracts, individual allergens or allergenic peptides are helpful in the diagnostic approach. Food-specific IgG continues to be an unproven or experimental test. The other alternative and complementary techniques have no proven benefit and may endanger patients via misdiagnosis.