Dilia Mercado

Mite fauna, Der p I, Der f I and Blomia tropicalis allergen levels in a tropical environment

Fifty dust samples were collected from the mattresses and bedroom floors of 25 subjects with allergic asthma in Cartagena, Colombia, in order to identify house dust mites and quantitate Der p I, Derf I and Blomia tropicalis allergens. The geometric mean of the total mite density per gram of dust was 418 (range, 40–2280). Twenty‐two samples (44%) had more than 500 mites and four, less than 100. B. tropicalis and Dermatopha‐goides pteronyssinus were found in 96% and 90% of the samples, accounting for 40.1% and 35.7% of the total mites, respectively. Cheyletus malaccensis, Chortoglyphus arcuatus, Pyroglyphus africanus, Orihatids, Grallacheles bakeri. Tarsonemus spp., Suidasia spp., Dermatophagoides farinae and unidentified mites accounted for the rest. The geometric mean of the total mites/gram of dust in mattresses (563.9) was significantly higher than in floor dust (309. 1), P < 0.01. Allergen concentrations and mite numbers were analysed by Spearman rank correlations: B. tropicalis mites vs B. tropicalis allergen, r= 0.54, P<0.001; D. pteronyssinus mites vs Der p I, r= 0.52, P< 0.001. A negative correlation was obtained between B. tropicalis mites and Der p I. Allergens derived from B. tropicalis and other domestic mite species may play an important role in sensitization and allergic symptoms in Cartagena, Colombia.

IgE cross-reactivity between Ascaris and domestic mite allergens: the role of tropomyosin and the nematode polyprotein ABA-1

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.

Cloning and IgE Binding of a Recombinant Allergen from the Mite Blomia tropicalis, Homologous with Fatty Acid-Binding Proteins

To characterize the allergens of Blomia tropicalis, a cDNA library was constructed and screened with allergic sera from asthmatic patients. One clone, Bt6, was subcloned and sequenced. The nucleotide sequence of 934 bp length shows a 390-bp reading frame which encodes a 130-amino acid protein with a MW 14.8 kD. No potential glycosylation site was found in the predicted protein. The inferred amino acid sequence has no homology to known allergens. It has a cytosolic fatty acid-binding protein (FABP) signature at 5-22 amino acid residues, 42.3% identity with the Sm14-FABP of Schistosoma mansoni and 36% identity with FABPs from rat, mouse, bovine and human. The protein was expressed as a GST fusion protein and the purified GST-Bt6 used for dot blot, RAST and RAST inhibition assays. The frequency of IgE binding of allergic sera to Bt6 was low (11%) and usually weak. One positive serum did, however, show strong reactivity by RAST and dot blot and Bt6 could inhibit 60% of the IgE binding of this serum to the B. tropicalis extract. These data show that Bt6 encodes a mite FABP with allergenic properties, which are pronounced in some atopic subjects.

Association between total immunoglobulin E and antibody responses to naturally acquired Ascaris lumbricoides infection and polymorphisms of immune system-related LIG4, TNFSF13B and IRS2 genes

The 13q33–34 region harbours a susceptibility locus to Ascaris lumbricoides, although the underlying genes are unknown. Immunoglobulin (Ig)E and IgG confer protective immunity and here we sought to investigate in an endemic population whether LIG4, TNFSF13B and IRS2 genes influence IgE and IgG levels against Ascaris and the ABA‐1 allergen as a putative resistance marker. Mite‐allergic asthmatic patients were analysed for potential relationships between Ascaris predisposition and allergy. One thousand and sixty‐four subjects from Cartagena, Colombia, were included. Single nucleotide polymorphisms (SNPs) were genotyped using TaqMan assays. Antibody levels were measured by enzyme‐linked immunosorbent assay. Linear and logistic regressions were used to model effects of genotypes on antibody levels. The GG genotype of LIG4 (rs1805388) was associated with higher IgE levels to Ascaris compared with other genotypes. TNFSF13B (rs10508198) was associated positively with IgG levels against Ascaris extract and IgE levels against ABA‐1. In asthmatics, IRS2 (rs2289046) was associated with high total IgE levels. Associations held up after correction by population stratification using a set of 52 ancestry markers, age, sex and disease status. There was no association with asthma or mite sensitization. In a tropical population, LIG4 and TNFSF13B polymorphisms are associated with specific IgE and IgG to Ascaris, supporting previous linkage studies implicating the 13q33 region. Our results suggest that genes protecting against parasite infections can be different to those predisposing to asthma and atopy.

Sequential determinations of Blomia tropicalis allergens in mattress and floor dust samples in a tropical city

BACKGROUND The mite species Blomia tropicalis is commonly found in tropical and subtropical regions, and it is an important source of allergen in the city of Cartagena, Columbia. AIM The study was designed to determine seasonal allergen levels of B. tropicalis in homes of patients with asthma and mite allergy. METHODS Dust samples from mattresses and floors in 20 homes were collected on a monthly basis for 1 year. Outdoor temperature, relative humidity, and rainfall were recorded. RAST inhibition was performed on extracts of dust samples. Allergen levels were compared with variations in climate. RESULTS B. tropicalis allergens were detected in all mattress samples. More than 50% RAST inhibition was detected in 30% of mattress samples and in 4.3% of floor samples, reflecting a high concentration of allergen. Significant correlations were only found between allergen levels and absolute humidity. CONCLUSION Levels of B. tropicalis allergen fluctuated minimally in Cartagena, Colombia.

African Ancestry is a Risk Factor for Asthma and High Total IgE Levels in African Admixed Populations

Characterization of genetic admixture of populations in the Americas and the Caribbean is of interest for anthropological, epidemiological, and historical reasons. Asthma has a higher prevalence and is more severe in populations with a high African component. Association of African ancestry with asthma has been demonstrated. We estimated admixture proportions of samples from six trihybrid populations of African descent and determined the relationship between African ancestry and asthma and total serum IgE levels (tIgE). We genotyped 237 ancestry informative markers in asthmatics and nonasthmatic controls from Barbados (190/277), Jamaica (177/529), Brazil (40/220), Colombia (508/625), African Americans from New York (207/171), and African Americans from Baltimore/Washington, D.C. (625/757). We estimated individual ancestries and evaluated genetic stratification using Structure and principal component analysis. Association of African ancestry and asthma and tIgE was evaluated by regression analysis. Mean ± SD African ancestry ranged from 0.76 ± 0.10 among Barbadians to 0.33 ± 0.13 in Colombians. The European component varied from 0.14 ± 0.05 among Jamaicans and Barbadians to 0.26 ± 0.08 among Colombians. African ancestry was associated with risk for asthma in Colombians (odds ratio (OR) = 4.5, P = 0.001) Brazilians (OR = 136.5, P = 0.003), and African Americans of New York (OR: 4.7; P = 0.040). African ancestry was also associated with higher tIgE levels among Colombians (β = 1.3, P = 0.04), Barbadians (β = 3.8, P = 0.03), and Brazilians (β = 1.6, P = 0.03). Our findings indicate that African ancestry can account for, at least in part, the association between asthma and its associated trait, tIgE levels.

A Six-SNP Haplotype of ADAM33 Is Associated with Asthma in a Population of Cartagena, Colombia

Background: A disintegrin and metalloprotein-33 (ADAM33) participates in the bronchial remodeling process in asthma, and genetic analyses pointed it out as a candidate gene in asthma. Methods: To analyze the association between ADAM33 and asthma and total and mite-specific IgE levels in a population of the Caribbean Coast of Colombia, we genotyped 6 single-nucleotide polymorphisms of ADAM33 in 429 asthmatics, 401 controls and 116 family trios using fluorogenic probes. Total and specific IgE against Blomia tropicalis and Dermatophagoides pteronyssinus were determined by ELISA. Case-control and family-based analyses were performed. Case-control association analyses were corrected by population stratification using a set of 52 ancestry-informative markers. Results: Eight common haplotypes were identified; among them, H4 (GCAGGG) was associated with asthma in the family group (Z score: –2.049, p = 0.04). We also found an association between the TT genotype of ST+7 and asthma in the case-control study (p = 0.05) that disappeared after correcting for multiple testing. In the family-based analysis, this genotype was a risk factor for asthma (p = 0.01), high total IgE (Z score: 2.546, p = 0.01) and high specific IgE against B. tropicalis (p = 0.02) and D. pteronyssinus (Z score: 2.414, p = 0.01). V4 was associated with specific IgE against B. tropicalis (p = 0.03); T2 with asthma (p = 0.03), high total IgE (p = 0.02) and IgE against D. pteronyssinus (p = 0.03) and T1 with high total IgE (p = 0.04). None of these associations was maintained after correction for multiple testing. Conclusions: Our findings suggest a relevant role of ADAM33 in thepathogenesis of asthma in this population.

Analysis of the Cross–Reactivity between BtM and Der p 5, Two Group 5 Recombinant Allergens from Blomia tropicalis and Dermatophagoides pteronyssinus

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.

The IgE response to Ascaris molecular components is associated with clinical indicators of asthma severity.

BackgroundAsthma is a common chronic disease worldwide and Ascaris lumbricoides infection (ascariasis) is frequent in tropical regions. However, the effect of ascariasis on asthma severity has not been sufficiently explored. We sought to evaluate the influence of the IgE immune response to Ascaris extract and purified house dust mites (HDM) and Ascaris allergens on indicators of asthma severity in patients living in the tropics.MethodsAsthmatic patients from Cartagena, Colombia were recruited. Clinical assessment included questionnaires, physical examination, allergy skin tests, spirometry, parasite stool examination and IgE antibody measurements. Asthma was diagnosed by a physician according to validated criteria. Indicators of severity were occurrence of severe dyspnea episodes, night awakenings events, > 4 emergency room (ER) visits and hospitalizations during the last year. Specific IgE to Der p 2, Ascaris spp., Blomia tropicalis and Dermatophagoides pteronyssinus extracts was determined by ImmunoCap. IgE to tropomyosins (Asc l 3, Blo t 10 and Der p 10), Blo t 5 and Asc s 1 was detected by ELISA. Logistic regression analyses were used to explore the relationships between sensitization and indicators of asthma severity.ResultsAfter adjustment for HDM sensitization, Ascaris sensitization remained associated with severe dyspnea (aOR: 1.90, 95% CI: 1.08 - 3.34, p = 0.03) and > 4 ER visits (aOR: 2.23, 95% CI: 1.15 - 4.30, p = 0.02). We also found that sensitization to the species specific markers Blo t 5 and Asc s 1, as well as the cross-reactive tropomyosins of D. pteronyssinus and Ascaris were associated with > 4 ER visits. Der p 2 sensitization was associated with bronchodilator responsiveness (aOR: 2.24: 1.25-4.02, p = 0.01). Remarkably, significantly higher IgE levels to HDM species specific allergens were found in Ascaris sensitized patients.ConclusionsIn this tropical population, IgE sensitization to Ascaris and the cross-reactive tropomyosins was frequent and associated with clinical indicators of asthma severity. The significant relationship between sensitization to the nematode-specific marker Asc s 1 and ER attendance supports these findings. Moreover, ascariasis increases the human IgE responses to HDM specific allergens.

A NOS1 gene polymorphism associated with asthma and specific immunoglobulin E response to mite allergens in a Colombian population.

Background: Nitric oxide (NO) is involved in asthma pathogenesis and is synthesized by three isoforms of NO synthase, one of them encoded by NOS1 gene. The CA-repeat and the C5266T SNP in NOS1 exon 29 have been associated with asthma and IgE levels. We thought to test the association of asthma and asthma-related phenotypes with the exon 29 CA-repeat and the C5266T SNP in a Colombian population sample. Methods: The CA-repeat and the C5266T SNP were genotyped in 167 asthmatics and 166 controls using PCR-based fragment length polymorphism and TaqMan assay. We also determined total and mite-specific IgE against Blomia tropicalis and Dermatophagoides pteronyssinus. Results: Three new CA-repeat alleles, 14, 23 and 24 repeats were detected. Allele comprising 16 repeats was associated with asthma (OR: 1.90 (CI 1.22–2.97, pc = 0.028) and low total (pc = 0.02) and specific IgE to B. tropicalis (pc < 0.0001) and D. pteronyssinus (pc < 0.0001). We found no association of the C5266T SNP and asthma or IgE levels. Conclusion:NOS1 exon 29 CA-repeat may be a risk factor for asthma susceptibility and mite specific IgE response in a Colombian population.