Faculty Bibliography

BACKGROUND:Data about epinephrine use and biphasic reactions in childhood food-induced anaphylaxis during oral food challenges are scarce. OBJECTIVE:To determine the prevalence and risk factors of reactions requiring epinephrine and the rate of biphasic reactions during oral food challenges (OFCs) in children. METHODS:Reaction details of positive OFCs in children between 1999 and 2007 were collected by using a computerized database. Selection of patients for OFCs was generally predicated on < or =50% likelihood of a positive challenge and a low likelihood of a severe reaction on the basis of the clinical history, specific IgE levels, and skin prick tests. RESULTS:A total of 436 of 1273 OFCs resulted in a reaction (34%). Epinephrine was administered in 50 challenges (11% of positive challenges, 3.9% overall) for egg (n = 15, 16% of positive OFCs to egg), milk (n = 14, 12%), peanut (n = 10, 26%), tree nuts (n = 4, 33%), soy (n = 3, 7%), wheat (n = 3, 9%), and fish (n = 1, 9%). Reactions requiring epinephrine occurred in older children (median, 7.9 vs 5.8 years; P < .001) and were more often caused by peanuts (P = .006) compared with reactions not treated with epinephrine. There was no difference in the sex, prevalence of asthma, history of anaphylaxis, specific IgE level, skin prick tests, or amount of food administered. Two doses of epinephrine were required in 3 of 50 patients (6%) reacting to wheat, cow's milk, and pistachio. There was 1 (2%) biphasic reaction. No reaction resulted in life-threatening respiratory or cardiovascular compromise. CONCLUSION/CONCLUSIONS:Older age and reactions to peanuts were risk factors for anaphylaxis during oral food challenges. Reactions requiring multiple doses of epinephrine and biphasic reactions were infrequent.

PURPOSE OF REVIEW/OBJECTIVE:To review current knowledge and recent advances in food protein-induced enterocolitis syndrome (FPIES). RECENT FINDINGS/RESULTS:Rice is the most common solid food causing FPIES. Rice FPIES is associated with more severe reactions than other foods. Infants presenting acutely may be hypothermic (<36 degrees C) and have thrombocytosis. Finding of hypoalbuminemia and weight gain less than 10 g/day helps to differentiate chronic infantile cow's milk FPIES from infectious causes. Gastric juice leukocytes more than 10 cells per high-power field are found in infants with positive oral food challenge to cow's milk. SUMMARY/CONCLUSIONS:FPIES is a non-IgE-mediated gastrointestinal food hypersensitivity disorder. Food protein-activated intestinal lymphocytes elaborate inflammatory cytokines that result in increased intestinal permeability, malabsorption, dysmotility, emesis, diarrhea, pain, and failure to thrive. Decreased intestinal transforming growth factor beta and increased TNFalpha may be important in FPIES. Cow's milk and soy are the most common causes of FPIES, but cereal grains (rice, oat, and barley), fish, poultry, and vegetables may also cause FPIES. The majority of FPIES resolve by age of 3 years.

BACKGROUND:Shellfish allergy is a long-lasting disorder usually persisting throughout life. Despite its high prevalence, there is limited information about allergenic shrimp proteins. OBJECTIVE:Characterization of shrimp allergens. METHODS:Fifty-two adults and children with a history of immediate allergic reactions to shrimp and elevated serum IgE to shrimp were selected for this study. Tryptic digests from a 20-kd IgE-binding protein were analyzed by LC-MS/MS, identifying the protein as a sarcoplasmic-calcium-binding protein. cDNA encoding sarcoplasmic calcium-binding protein (SCP) from a shrimp cDNA library (Litopenaeus vannamei) was amplified by PCR, cloned into an expression vector, and sequenced. Recombinant SCP was tested with patients' sera. ELISA inhibition experiments determined the fraction of total shrimp IgE recognizing SCP. A functional assay with a rat basophilic leukemia cell line was used to determine the capacity for mediator release induced by SCP. RESULTS:Immunoblotting demonstrated IgE binding by 31 of 52 (59.6%) of the sera to a 20-kd shrimp protein. The protein was identified as a SCP. Amplified cDNA encoding SCP was isolated and sequenced. Open reading frame translation provided the complete amino acid sequence of shrimp SCP. Recombinant SCP was recognized by serum IgE from 20 of 52 (38.4%) subjects, of whom 17 of 20 (85%) were children. ELISA inhibition of pooled sera IgE reactivity to BS extract using recombinant SCP was significant (as high as 79%). For some subjects, mediator release induced by recombinant SCP was higher than that induced by recombinant tropomyosin. CONCLUSION/CONCLUSIONS:We have identified and cloned a new shrimp allergen, Lit v 4.0101, an SCP, which appears to be of particular importance in the pediatric population.

PURPOSE OF REVIEW/OBJECTIVE:To review recent advances in the area of food allergen processing and the effect on protein allergenicity. RECENT FINDINGS/RESULTS:Heating generally decreases protein allergenicity by destroying conformational epitopes. In peanut and shrimp, heat-induced Maillard reaction (glycation) may increase allergenicity. The majority of milk and egg-allergic children tolerate extensively heated (baked with wheat matrix) milk and egg. Introduction of extensively heated milk and egg proteins is associated with decreasing sizes of skin prick test wheals and increasing serum food-specific IgG4 levels. SUMMARY/CONCLUSIONS:Heating and other methods of food processing have different effects on food allergens, even those contained in the same complex food. Structural homology does not reliably predict the effect of processing on allergenicity, and individual food allergens have to be tested. Interactions with other proteins, fat, and carbohydrates in the food matrix are complex and poorly understood. Introduction of extensively heated milk and egg proteins into the diet of allergic children may represent an alternative approach to oral tolerance induction. Better characterization of these aspects of food allergy is critical for elucidation of food protein interactions with the gut-associated lymphoid tissue, the ability to induce IgE sensitization, the potential to trigger hypersensitivity reactions, and different clinical phenotypes of food allergy with regard to severity and persistence.

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 patient's 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.

BACKGROUND:Cockroach is an important allergen in inner-city asthma. The diagnosis and treatment of cockroach allergy has been impeded by the lack of standardized cockroach extracts. OBJECTIVE:We investigated the utility of a mediator release assay based on rat basophil leukemia (RBL) cells for comparing the potency of German cockroach extracts. METHODS:RBL cells (line 2H3) transfected with human FcepsilonRI were passively sensitized with sera from subjects with cockroach allergy and stimulated with serial dilutions of 3 commercial cockroach extracts (1:10 weight/volume). In addition, the in-house prepared extract was tested in separate experiments with pooled sera that produced optimal performance in the RBL assay. N-hexosaminidase release (NHR) was used as a marker of RBL cell degranulation and was examined in relation to the intradermal skin test (ID(50)EAL) and serum cockroach-specific and total IgE levels. RESULTS:The median cockroach-specific IgE concentration in 60 subjects was 0.72 kU(A)/L (interquartile range, 0.35-2.97 kU(A)/L); 19 sera (responders) produced a minimum 10% NHR to more than 1 extract. Responders had higher median cockroach-specific IgE (7.4 vs 1.0 kU(A)/L) and total IgE (429 vs 300 kU/L) levels than nonresponders. Ranking of extract potency was consistent between the mediator release assay and the ID(50)EAL. For the in-house prepared cockroach extract, the dose-response curves were shifted according to the concentration of the extract. NHR was reproducible between different experiments by using pooled sera. CONCLUSION/CONCLUSIONS:The mediator release assay measures biologic potency and correlates with the ID(50)EAL. It should be further evaluated to determine whether it could be used to replace intradermal skin test titration for assessing the potency of cockroach extract.

BACKGROUND:Children with milk allergy who tolerate heat-denatured milk (HM) have less severe reactions and outgrow the condition earlier than those who react to HM, which might be related to differences in IgE-dependent effector cell function. OBJECTIVE:We sought to apply a novel assay to test the hypothesis that HM-tolerant children have suppressed IgE-mediated basophil responses. METHODS:Allergic, HM-tolerant, outgrown, or control subjects were defined based on oral food challenges. Whole blood cells were stimulated in vitro with a range of milk allergen doses in the presence or absence of autologous serum or with dilutions of autologous serum. Activated basophils were identified by means of flow cytometry as CD63(bright)CD123+CD203c+HLA-DR(-)CD41a(-). RESULTS:HM-tolerant subjects' basophils were significantly less responsive to milk allergen stimulation at all doses than were basophils from HM-reactive (allergic) individuals. In the absence of autologous serum, HM-tolerant subjects' basophils were significantly more reactive at low allergen concentrations. To a lesser extent, autologous serum also inhibited IL-3- and anti-IgE-induced, but not N-formyl-methionyl-leucyl-phenylalanine-induced, responses. The allergen-specific responsiveness of HM-tolerant subjects' basophils increased with dilution of autologous serum with normal pooled serum. CONCLUSION/CONCLUSIONS:Children with milk allergy with a favorable prognosis have evidence of extrinsically suppressed allergen-specific effector cell reactivity.

BACKGROUND:About 70% of children with milk allergy tolerate extensively heated milk (HM) products and outgrow their allergy earlier than those who react to HM. OBJECTIVE:To test the hypothesis that HM-tolerant children have a higher precursor frequency of adaptive allergen-specific regulatory T (Treg) cells. METHODS:Allergic, HM-tolerant, outgrown, or control subjects were defined by oral food challenge. PBMCs were cultured with purified caseins and controls for 7 days, and proliferating CD25(+)CD27(+) Treg cells were identified by flow cytometry. Proliferating cells were also characterized for their expression of FoxP3, CTLA 4, CD45RO, and CD127. Allergen-specific Treg cell origin and function were assessed by depletion of CD25(hi) cells before culture. RESULTS:There was a higher percentage (median [25th% to 75th%], 16.85% [7.1-31.7]) of proliferating allergen-specific CD25(+)CD27(+) T cells from cultures of HM-tolerant subjects (n = 18) than subjects with allergy (n = 8; 4.91% [2.6-7.5]; P < .01). Control subjects with no history of milk allergy (n = 7) also had low percentages of these cells (2.9% [2.4-6.0]), whereas outgrown subjects (n = 7) had intermediate percentages (9.0% [2.7-16.4]). There were no significant differences between the patient groups in the frequency of polyclonal Treg cells or allergen-specific effector T cells. Allergen-specific Treg cells were found to be FoxP3(+)CD25(hi)CD27(+), cytotoxic T lymphocyte-associated antigen 4(+), CD45RO(+)CD127(-) and were derived from circulating CD25(hi) T cells. Depletion of the CD25(hi) cells before in vitro culture significantly enhanced allergen-specific effector T-cell expansion. CONCLUSION/CONCLUSIONS:A higher frequency of milk allergen-specific Treg cells correlates with a phenotype of mild clinical disease and favorable prognosis.

BACKGROUND:Prior studies have suggested that heated egg might be tolerated by some children with egg allergy. OBJECTIVE:We sought to confirm tolerance of heated egg in a subset of children with egg allergy, to evaluate clinical and immunologic predictors of heated egg tolerance, to characterize immunologic changes associated with continued ingestion of heated egg, and to determine whether a diet incorporating heated egg is well tolerated. METHODS:Subjects with documented IgE-mediated egg allergy underwent physician-supervised oral food challenges to extensively heated egg (in the form of a muffin and a waffle), with tolerant subjects also undergoing regular egg challenges (in a form of scrambled egg or French toast). Heated egg-tolerant subjects incorporated heated egg into their diets. Skin prick test wheal diameters and egg white, ovalbumin, and ovomucoid IgE levels, as well as ovalbumin and ovomucoid IgG4 levels, were measured at baseline for all subjects and at 3, 6, and 12 months for those tolerant of heated egg. RESULTS:Sixty-four of 117 subjects tolerated heated egg, 23 tolerated regular egg, and 27 reacted to heated egg. Heated egg-reactive subjects had larger skin test wheals and greater egg white-specific, ovalbumin-specific, and ovomucoid-specific IgE levels compared with heated egg- and egg-tolerant subjects. Continued ingestion of heated egg was associated with decreased skin test wheal diameters and ovalbumin-specific IgE levels and increased ovalbumin-specific and ovomucoid-specific IgG4 levels. CONCLUSIONS:The majority of subjects with egg allergy were tolerant of heated egg. Continued ingestion of heated egg was well tolerated and associated with immunologic changes that paralleled the changes observed with the development of clinical tolerance to regular egg.