RESUMEN
BACKGROUND: Lentils are among the main plant foods causing allergic reactions in pediatric patients in the Mediterranean area and in many Asian communities. However, very few reports have been devoted to identifying lentil allergens. Seed storage proteins of the vicilin family have been characterized as major allergens in several seed legumes and tree nuts. OBJECTIVE: We sought to evaluate the role of lentil vicilins as food allergens. METHODS: A serum pool and individual sera from 22 patients with lentil allergy were used in different IgE-binding assays. Mature lentil vicilin was isolated by means of cation-exchange chromatography, followed by reverse-phase HPLC, and characterized by means of N-terminal amino acid sequencing, matrix-assisted laser desorption/ionization mass spectrometry (MALDI) analysis, complex asparagine-linked glycan detection, specific IgE immunodetection with individual sera, and ELISA inhibition assays. Complete cDNAs encoding lentil vicilin variants were isolated by means of PCR with primers based on the amino acid sequence of the allergen. RESULTS: A major IgE-binding component of approximately 50 kd was detected in lentil extracts. This component was isolated and characterized, showing a single N-terminal amino acid sequence homologous to those of legume vicilins and a broad peak (maximum at 48613 d) in MALDI analysis. The purified allergen was recognized by 77% (17/22) of the individual sera from patients with lentil allergy and reached up to 65% inhibition of the IgE binding to the crude lentil extract. The allergen showed 3 isoforms varying in their degree of N-glycosylation. Two cDNA clones encoding different allergen variants were isolated. The amino acid sequences deduced from both clones (415 and 418 residues; 47.4 and 47.8 kd) showed greater than 50% identity with major peanut (Ara h 1) and soybean (conglutinin subunits) allergens belonging to the vicilin family. Furthermore, these sequences included those of the previously characterized lentil allergen Len c 1.02 (108 amino acid residues of the C-terminal domain) and those of a novel lentil IgE-binding protein of 26 kd. CONCLUSION: The mature 48-kd lentil vicilin, designated Len c 1.01, is a major allergen. Two of its processing fragments, corresponding to subunits of 12 to 16 kd (previously named Len c 1) and 26 kd, are also relevant lentil IgE-binding proteins. The sequence homology of Len c 1.01 to those of major allergens from peanut, soybean, walnut, and cashew can help to investigate potential cross-reactions among these plant foods.
Asunto(s)
Alérgenos/aislamiento & purificación , Clonación Molecular , Hipersensibilidad a los Alimentos/etiología , Lens (Planta)/química , Proteínas de Plantas/aislamiento & purificación , Semillas/química , Adolescente , Adulto , Alérgenos/química , Alérgenos/genética , Alérgenos/inmunología , Secuencia de Aminoácidos , Secuencia de Bases , Niño , Preescolar , ADN Complementario , Ensayo de Inmunoadsorción Enzimática/métodos , Femenino , Humanos , Inmunoglobulina E/sangre , Inmunoglobulina E/inmunología , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/inmunología , Proteínas de Almacenamiento de Semillas , Análisis de Secuencia de ADNRESUMEN
BACKGROUND: It is thought that the natural evolution of food allergy has a good tolerance prognosis. However, there are few follow-up studies that determine the exact probability of tolerance to a given food or that analyze prognostic factors that can help us to understand the evolution of a child who begins life with a food allergy. OBJECTIVE: We sought to determine the likelihood that children younger than 2 years of age with allergy to egg would eventually have tolerance to it and to analyze several prognostic predictors using egg white-specific IgE level as the main variable. METHODS: We performed a prospective study of 58 children younger than 2 years of age with egg allergy, who were studied periodically until tolerance developed or until the end of the study. During the follow-up period, open challenge tests were carried out according to previously established criteria to verify tolerance to egg. Factors such as egg white-specific IgE level, serum total IgE level, symptoms after egg ingestion, size of skin prick test reactions to egg white, atopic dermatitis, and sex were analyzed as prognostic markers. Kaplan-Meier survival curves were used to calculate cumulative tolerance probability. Predictor influence and relative prognostic importance were estimated with the Cox proportional regression model. RESULTS: The median time from the appearance of the first symptoms to tolerance was 35 months. Cumulative tolerance probability was 16% at 12 months of follow-up, 28% at 24 months, 52% at 36 months, 57% at 48 months, and 66% at 60 months. The relative weight of prognostic factors, expressed as the hazard ratio, was 50.95 for symptoms and 3.74 for the size of skin prick test reactions, with both being independent effects. The hazard ratio was 1.173 for every 0.1-unit decrease in the concentration log (decimal logarithm) of specific IgE level, with this effect being associated with tolerance only in children with cutaneous symptoms. CONCLUSIONS: Half of the children younger than 2 years of age with egg allergy will tolerate the food at 35 months of follow-up, and the proportion could be 66% after 5 years. At that age, the main predictors were the symptoms experienced after egg ingestion, followed by the size of skin prick test reactions. In addition, the specific IgE antibody level is an important prognostic marker in children who only had cutaneous symptoms.
Asunto(s)
Hipersensibilidad al Huevo/inmunología , Clara de Huevo/efectos adversos , Inmunoglobulina E/sangre , Hipersensibilidad al Huevo/sangre , Femenino , Humanos , Tolerancia Inmunológica/inmunología , Inmunoglobulina E/inmunología , Lactante , Masculino , Valor Predictivo de las Pruebas , Estudios ProspectivosRESUMEN
Gastro-allergic anisakiasis has been reported as an entity in which an acute parasitism by Anisakis simplex is accompanied by an immunoglobulin (Ig)E-mediated systemic allergic reaction. Serum samples were obtained from 24 patients within 24 h after the onset of symptoms (day 0) and after 1 month (day 30) and in 13 patients after 6 months. Total IgE was assessed by the Imx method. Specific IgE was assessed by CAP-FEIA. Specific IgM, IgG, IgG4 and IgA antibodies were assessed by enzyme-linked immunosorbent assay against crude extract (CE) and excretory-secretory products (ESP). IgE immunoblotting (IB) was directed against CE or ESP (day 0 and day 30). We found a rise of total IgE, specific IgE, number of bands in IgE-IB, IgG and IgG4 between day 0 and day 30 with a fall to near basal levels after 6 months. IgM levels were highest at day 0, falling over the next 6 months and IgA levels remained almost unchanged. Correlation studies revealed a parallel stimulation of nearly all Ig isotypes, except IgM anti-ESP, whose antibody levels correlated negatively with specific IgG levels. We found an extension of the IgE antibody repertoire in IB. We conclude that the allergic IgE-mediated reaction in the course of gastro-allergic anisakiasis involves a parallel secondary Th2 type memory response and a primary immunologic stimulation of both Th2 and Th1 lymphocyte subsets against previously unrecognized antigens.