RESUMO
BACKGROUND: Analysis of cross-reactivity between the nematode Ascaris ssp. and dust mites, two important allergen sources in the tropics, will contribute in understanding their influence on asthma and atopy. The objective of this study was to investigate immunoglobulin E (IgE) cross-reactivity between Ascaris and two domestic mites in the tropics. METHODS: Sera from 24 asthmatic patients were used in ELISA and immunoblotting IgE-binding inhibition assays using Ascaris, Blomia tropicalis and Dermatophagoides pteronyssinus extracts and the recombinants Blo t 10, ABA-1 and Blo t 13 as competitors. Identification of Ascaris allergens was confirmed by mass spectrometry (LC-MS/MS). RESULTS: We detected at least 12 human IgE-binding components in Ascaris extract. Blomia tropicalis and D. pteronyssinus inhibited 83.3% and 79% of IgE-binding to Ascaris, while Ascaris inhibited 58.3% and 79.3% to B. tropicalis and D. pteronyssinus respectively. Mite tropomyosin inhibited 85% of IgE-binding to Ascaris. Affinity-purified human IgE to rBlo t 10 identified an allergen of 40 kDa in Ascaris extract, further confirmed as tropomyosin by LC-MS/MS. We found no evidence of IgE cross-reactivity between rABA-1 and any allergen component in mite extracts, including rBlo t 13. CONCLUSIONS: There is cross-reactivity between Ascaris and mites, determined by several allergens including tropomyosin and glutathione-S-transferase. In addition to its potential impact on asthma pathogenesis, Ascaris infection and mite allergy diagnosis relying on the determination of specific IgE could be affected by this cross-reactivity. ABA-1 has no cross-reactive counterpart in mite extracts, suggesting its usefulness as a more specific marker of Ascaris infection.
Assuntos
Alérgenos/imunologia , Antígenos de Dermatophagoides/imunologia , Ascaris/imunologia , Asma , Hipersensibilidade Imediata/imunologia , Imunoglobulina E , Ácaros/imunologia , Tropomiosina/imunologia , Adolescente , Adulto , Animais , Antígenos de Plantas , Asma/imunologia , Asma/fisiopatologia , Criança , Reações Cruzadas , Feminino , Glutationa Transferase/imunologia , Proteínas de Helminto/imunologia , Humanos , Hipersensibilidade Imediata/fisiopatologia , Imunoglobulina E/imunologia , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
BACKGROUND: Differences in the IgE response to isoallergens could have clinical implications; therefore, its analysis will contribute to the design of better strategies for the diagnosis and treatment of allergic respiratory diseases. Several isoforms have been described from mites but there is no information about the clinical impact of Blomia tropicalis isoallergens. OBJECTIVE: To evaluate the differences in the IgE response against two Blo t 12 isoallergens. METHODS: The IgE-binding properties of Blo t 12 isoallergens were analysed by ELISA, a skin prick test and ELISA cross-inhibition. Epitope mapping was performed using synthetic overlapping peptides. Fold recognition methods were used to model the chitin-binding domain of the two isoallergens. RESULTS: The frequency and strength of the IgE response were greater for Blo t 12.0101 than for Blo t 12.0102. Three IgE-binding areas were identified in Blo t 12.0101; one of them included two residues that are different in Blo t 12.0102. Modelling of the chitin-binding domains of these allergens predicted that they have structural differences that could influence antibody recognition of one of these epitopes. CONCLUSION: In silico structural analysis and immunological characterization of Blo t 12 reveals that allergen polymorphism influences IgE reactivity. Blo t 12.0101 is the most IgE-reactive isoform in Cartagena. The identified IgE epitopes could be mutated to obtain hypoallergenic molecules of potential use for immunotherapy.
Assuntos
Alérgenos/imunologia , Asma/imunologia , Imunoglobulina E/sangue , Pyroglyphidae/imunologia , Adolescente , Alérgenos/química , Sequência de Aminoácidos , Animais , Criança , Clonagem Molecular , Reações Cruzadas/imunologia , Mapeamento de Epitopos , Humanos , Dados de Sequência Molecular , Peptídeos/imunologia , Isoformas de Proteínas/química , Isoformas de Proteínas/imunologia , Pyroglyphidae/química , Alinhamento de Sequência , Testes CutâneosRESUMO
The Chinese delicacy "bird's nest" is the most common cause of food-induced anaphylaxis requiring hospitalization among Chinese children in Singapore. This investigation has established an immunoglobulin E-mediated cause and has characterized the major putative allergens.
Assuntos
Anafilaxia/epidemiologia , Anafilaxia/etiologia , Aves , Hipersensibilidade Alimentar/epidemiologia , Adolescente , Animais , Criança , Pré-Escolar , China/etnologia , Feminino , Humanos , Imunoglobulina E/sangue , Lactente , Masculino , Estudos Prospectivos , Estudos Retrospectivos , Singapura/epidemiologiaRESUMO
BACKGROUND: In tropical climates, sensitization to Bloma tropicalis and Dermatophagoides pteronyssinus is high and mainly directed to species-specific allergens. There is some cross-reactivity between extracts of these mites, probably due to the group 5 allergens that have high sequence homology. OBJECTIVE AND METHODS: We used the radioallergosorbent test (RAST), RAST inhibition and immunoblotting inhibition experiments to investigate the cross-reactivity between the recombinant allergens BtM and Der p 5, expressed as glutathione S-transferase fusion proteins, to detect the epitopes involved and to analyze the importance of this cross-reactivity. RESULTS: Seventy-nine percent of 48 patients sera were RAST positive to both recombinants, with a strong correlation (r = 0.8, p<0.0001). BtM inhibited 25 and 21.1% of IgE-binding to B. tropicalis and D. pteronyssinus extracts respectively and Der p 5 inhibited 22 and 24% of IgE-binding to D. pteronyssinus and B. tropicalis extracts. Furthermore, BtM inhibited 74.5% of IgE binding to Der p 5 and Der p 5 inhibited 72.4% of IgE-binding to BtM. RAST inhibition with BtM-derived synthetic peptides showed that peptide 4 (residues 35-50) and peptide 5 (residues 46-61) inhibited 37 and 16% of IgE-binding to BtM while peptides 5 and 2 (residues 14-30) were able to inhibit the IgE binding (32 and 28%, respectively) to Der p 5. CONCLUSION: There is cross-reactivity between BtM and Der p 5, which explains almost all the cross-reactivity between the two mite extracts. This cross-reactivity seems to be related to epitope(s) at the C-terminal segment of these allergens.
Assuntos
Alérgenos/imunologia , Glicoproteínas/imunologia , Alérgenos/genética , Alérgenos/metabolismo , Animais , Especificidade de Anticorpos/imunologia , Antígenos de Dermatophagoides , Antígenos de Plantas , Ligação Competitiva/imunologia , Reações Cruzadas , Glutationa Transferase/genética , Glicoproteínas/genética , Glicoproteínas/metabolismo , Humanos , Imunoglobulina E/sangue , Imunoglobulina E/metabolismo , Ácaros/imunologia , Teste de Radioalergoadsorção , Proteínas Recombinantes de Fusão/imunologiaRESUMO
In tropical and subtropical regions of the world, allergens produced by Blomia tropicalis are an important cause of IgE-mediated sensitization among patients with asthma. We compared the relative importance of sensitization to the two mite species among asthma patients from Florida, Puerto Rico, and Brazil (n = 83), who were concurrently exposed to B. tropicalis and D. pteronyssinus, with patients from the United States and from the United Kingdom (n = 56) exposed to D. pteronyssinus. In addition, molecular cloning techniques were used to clone and express a major B. tropicalis allergen. There were significant differences between IgE antibody responses to B. tropicalis and D. pteronyssinus that were related to exposure: only 22% of patients exposed to both species had a high ratio (> 10) of IgE D. pteronyssinus:B. tropicalis, whereas 68% of patients exposed only to D. pteronyssinus had a ratio of > 10 (p < 0.001). A major 14-kD allergen (Blo t 5), cloned from a B. tropicalis cDNA library, showed 43% sequence homology to D. pteronyssinus Der p 5. Recombinant Blo t 5 produced in E. coli reacted with 45 to 69% of sera from B. tropicalis-allergic asthmatics and induced positive immediate skin tests at 10(-3) to 1 microg/ml. In vivo and in vitro comparisons of IgE responses to B. tropicalis, D. pteronyssinus, rBlo t 5, and rDer p 5, showed that B. tropicalis has unique allergens that cause specific IgE responses. The results suggest that B. tropicalis is an independent cause of sensitization and that use of recombinant Blo t 5 should lead to a better understanding of the role of B. tropicalis in causing asthma in tropical environments.