Haplotypes of G protein-coupled receptor 154 are associated with childhood allergy and asthma

RATIONALE

Allergic diseases are influenced by both genes and environment. A 70-kb haplotype block in the G protein-coupled receptor for asthma susceptibility gene (GPR154; alias GPRA) on chromosome 7p was recently identified to influence susceptibility to asthma and elevated total serum IgE levels in adults.

OBJECTIVES

To assess the impact of GPR154 on childhood allergic disease, including allergic sensitization, asthma, and rhinoconjunctivitis, in study populations with diverse environmental backgrounds.

METHODS

We studied farm children, Steiner school children, and two reference groups from five Western European countries in the cross-sectional PARSIFAL (Prevention of Allergy Risk factors for Sensitization In children related to Farming and Anthroposophic Lifestyle) study and a sample of children from the Swedish birth cohort study BAMSE. DNA samples from 3,113 PARSIFAL and 800 BAMSE children were genotyped for 7 GPR154 polymorphisms and haplotypes were inferred. The proportions of alleles and haplotypes (H1-H7) were compared in affected children with their healthy counterparts.

RESULTS

Data indicate a global association of the haplotype block to sensitization (allergen-specific serum IgE > or = 0.35 kU/L, p = 0.022), with significant haplotype-specific associations for H1, H5, and H6. Haplotypes H1 and H5 were also significantly associated with childhood allergic asthma (p = 0.045 and p = 0.023, respectively), and H5 to asthma regardless of sensitization. A broader involvement of GPR154 in allergic diseases was further supported in allergic rhinoconjunctivitis (H3: p = 0.046). The associated haplotypes could be allocated into risk (H5/H6) and nonrisk (H1/H3) groups, a pattern supported by allelic association of single nucleotide polymorphisms (SNPs) rs324384 and rs324396.

CONCLUSIONS

Our results indicate that polymorphisms and haplotypes in the haplotype block of GPR154 are associated with asthma, rhinoconjunctivitis, and sensitization in European children.

Crystallization and preliminary crystallographic data of a Fel d 1 (1+2) construct corresponding to the major allergen from cat

The domestic cat (Felis domesticus) is one of the most important causes of allergic disease worldwide. A homologue of the major allergen Fel d 1 was created by linking the two chains that compose the protein. Fel d 1 (1+2) was expressed in Escherichia coli and subsequently purified using three chromatographic steps. Crystals of Fel d 1 (1+2) were obtained using the hanging-drop vapour-diffusion method in 22.5% PEG 3350, 0.5 M CaCl2. The crystals belong to space group P1, with unit-cell parameters a = 38.5, b = 42.9, c = 49.0 A, alpha = 70.7, beta = 80.5, gamma = 81.5 degrees , and diffract to 1.6 A resolution.

Qualitative and Quantitative Evaluation of Bird-Specific IgG Antibodies

BACKGROUND

Exposure to organic dust produced by birds often gives rise to an immune response, e.g. IgG antibodies, but intense exposure can lead to high concentrations of IgG antibodies and the development of allergic alveolitis, often known as "bird fancier's lung". The aim of this study was to establish the distribution of bird-specific IgG antibodies in exposed and nonexposed individuals and compare a nonquantitative and quantitative method in evaluating raised levels of IgG antibodies.

METHODS

Sera were collected in Sweden and South Africa and levels of IgG antibodies specific to pigeon, budgerigar and parrot antigens were quantified using the UniCAP system. Results were compared to the precipitation in gel assay. The IgG antibody values of symptomatic patients without precipitating antibodies (non-PP group; n = 51) and patients with precipitating antibodies (PP group; n = 34) were analyzed and compared to nonexposed asymptomatic blood donors (BD group; n = 73) and environmentally exposed pigeon breeders (n = 11).

RESULTS

The IgG antibody response of the analyzed groups in Sweden and South Africa did not vary significantly from each other. IgG antibody responses were the strongest to pigeon antigens with clear increased IgG antibody levels in the PP group [geometric mean (GM) 603 mg/l] compared to the non-PP (GM 6.9 mg/l) and BD group (GM 5.0 mg/l). Threshold values, calculated as the GM value from the BD group plus 3 standard deviations (99% confidence interval), were 9.8, 10.8 and 10.0 mg/l for pigeons, budgerigars and parrots, respectively. Comparison of the two methods resulted in a good concordance with a level of agreement of 94.1% (kappa statistic = 0.83).

CONCLUSIONS

The UniCAP system for the detection of bird-specific IgG antibodies is a highly reproducible, generally available, quantitative method for routine diagnostic testing and monitoring of exposed subjects with a very high level of agreement to the precipitating gel assay.

Increased Levels of IL-2 and IL-4 in Stimulated Adenoidal Lymphocytes of Atopic Children

BACKGROUND

The adenoid is involved in the defence against airway pathogens and its surface is also exposed to airborne allergens. The knowledge about reactions taking place in the lymphatic tissue of this organ is, however, limited. To elucidate the influence of atopy we investigated the cellular and cytokine profile of in vitro-stimulated adenoid lymphocytes.

METHODS

Adenoid tissue cells from 13 atopic and 8 non-atopic children were cultured and stimulated with ionomycin and 4beta-phorbol 12-myristate 13-acetate. Supernatants were collected after 4 and 20 h of stimulation and interleukin-2 (IL-2), IL-4 and interferon-gamma (IFN-gamma) were analysed by ELISA. Flow cytometry was used to quantify the leukocyte markers CD3, CD19, CD25 and HLA-DR.

RESULTS

Increased levels of IL-2 and IL-4 but not IFN-gamma were detected in the supernatants of adenoid cell cultures from atopic children after 20 h of stimulation (p < 0.05) and a significant correlation with a positive regression between IL-2 and IL-4 was found. Atopy was also associated with a greater increase in the percentage of CD19-positive B cells after stimulation (p < 0.05).

CONCLUSIONS

A difference in the reactivity of adenoidal lymphoid cells in children was observed between atopic and non-atopic subjects. Atopy was associated with an increased production of IL-2 and IL-4 as well as a more pronounced increase of B cells.

Formation of disulfide bonds and homodimers of the major cat allergen Fel d 1 equivalent to the natural allergen by expression in Escherichia coli

Dander from the domestic cat (Felis domesticus) is one of the most common causes of IgE-mediated allergy. Attempts to produce tetrameric folded major allergen Fel d 1 by recombinant methods with structural features similar to the natural allergen have been only partially successful. In this study, a recombinant folded Fel d 1 with molecular and biological properties similar to the natural counterpart was produced. A synthetic gene coding for direct fusion of the Fel d 1 chain 2 N-terminally to chain 1 was constructed by overlapping oligonucleotides in PCR. Escherichia coli expression resulted in a non-covalently associated homodimer with an apparent molecular mass of 30 kDa defined by size exclusion chromatography. Furthermore, each 19,177-Da subunit displayed a disulfide pattern identical to that found in the natural Fel d 1, i.e. Cys3(1) Cys73(2), Cys44(1)-Cys48(2), Cys70(1)-Cys7(2), as determined by electrospray mass spectrometry after tryptic digestion. Circular dichroism analysis showed identical folds of natural and recombinant Fel d 1. Furthermore, recombinant Fel d l reacted specifically with serum IgE, inducing expression of CD203c on basophils and lymphoproliferative responses in cat-allergic patients. The results show that the overall fold and immunological properties of the recombinant Fel d 1 are very similar to those of natural Fel d 1. Moreover, the recombinant Fel d 1 construct provides a tool for defining the three-dimensional structure of Fel d 1 and represents a reagent for diagnosis and allergen-specific immunotherapy of cat allergy.

Death in anaphylaxis in a man with house dust mite allergy

Up to recently the post-mortem diagnosis of anaphylaxis has been based solely on circumstantial evidence. With the development of assays for mast cell tryptase it is now possible to verify cases of suspected anaphylaxis. Here we present one such case, which initially appeared to be due to sudden death of unknown cause. A 47-year-old farmer was found dead in his bathroom around midnight. Hospital records revealed that he had previously been diagnosed with an allergy to house dust mites. He had also had infrequent episodes of airway symptoms, nausea, hypotension and diarrhoea usually after going to bed. The forensic autopsy did not give any clue to the cause of death. Serum tryptase in post-mortem blood was found to be substantially elevated in two samples (170 and >200 microg/L). Analysis of allergen-specific IgE showed high values for Dermatophagoides pteronyssinus and farinae. High mite allergen levels were found in dust obtained from the patient's mattress. The results of the immunological tests support the assumption that he died of anaphylactic shock. The circumstances and the patient's history of previous attacks after going to bed point to the fact that exposure to mite contaminated food and/or exposure to mite allergens in bed might have caused his death.

The crystal structure of the major cat allergen Fel d 1, a member of the secretoglobin family

The domestic cat (Felis domesticus) is one of the most important causes of allergic asthma worldwide. The dominating cat allergen, Fel d 1, is composed of two heterodimers. Recently, it has been shown that recombinant Fel d 1, consisting of chain 2 and chain 1 fused together without additional linker, has immunological properties indistinguishable from the natural heterodimeric protein. Herein, we report the crystal structure of recombinant monomeric Fel d 1 at 1.85-A resolution, determined by multi-wavelength anomalous diffraction using selenomethionine substituted protein. Fel d 1 is an all-helical protein and consists of eight helices. The two halves of the recombinant Fel d 1 molecule, corresponding to the wild-type Fel d 1 chains, are very similar in three-dimensional structure, despite the lack of significant sequence identity. The structure of the Fel d 1 presents a striking similarity to that of uteroglobin, a steroid-inducible cytokine-like molecule with anti-inflammatory and immunomodulatory properties. An internal, asymmetric cavity is formed in the Fel d 1 that could bind an endogenous ligand. The distribution of residues lining this cavity suggests that such a ligand must be amphipathic. The structure of Fel d 1 displays the localization of three previously defined Fel d 1 IgE epitopes on the surface of the protein. The three-dimensional structure provides a framework for rational design of hypoallergenic mutants aimed for treatment of cat allergy.

Production, crystallization and preliminary crystallographic study of the major cat allergen Fel d 1

The domestic cat (Felis domesticus) is an important cause of allergic disease worldwide. The major cat allergen 1 (Fel d 1) has been expressed in Escherichia coli, purified and refolded in a soluble form. Crystals of Fel d 1 were obtained in 13% 2-methyl-2,4-pentanediol, 0.1 M sodium acetate pH 4.8. The Fel d 1 crystals belong to space group P2(1), with unit-cell parameters a = 43.3, b = 51.5, c = 67.7 A, and diffract to 1.9 A resolution.

Heredity, pet ownership, and confounding control in a population-based birth cohort

BACKGROUND

The association between pet ownership in childhood and subsequent allergic disease is controversial. Bias related to selection of pet exposure has been suggested as a reason for contradictory study results.

OBJECTIVE

The purpose of this investigation was to elucidate how pet exposure depends on family history of allergic disease, smoking, and socioeconomic factors in a prospective birth cohort.

METHODS

Parents of 4089 two-month-old children answered a questionnaire that included detailed questions about family history of asthma (maternal, paternal, and sibling), rhinoconjunctivitis, atopic eczema/dermatitis syndrome, pollen and pet allergy, smoking habits, parental occupation, and family pet ownership (cat and dog). Dust samples collected from the mothers' beds were analyzed for Fel d 1 and Can f 1 in a subgroup of the cohort.

RESULTS

Cats were less frequently kept in families with parental asthma, rhinoconjunctivitis, or pet or pollen allergy (3.5% to 5.8%) than in families without parental allergic disease (10.8% to 11.8%). Dogs were less common in families with (3.3%) than in families without (5.9%) parental atopic eczema/dermatitis syndrome. Families with smoking mothers and those with low socioeconomic index kept cats and dogs more frequently. Cat allergen levels were lower in homes with than in homes without maternal pet allergy, and this tended to hold true even for homes without a cat. Cat ownership decreased from birth to 2 years of age, especially in families with parental history of allergic diseases.

CONCLUSION

There seems to be a selection of pet exposure based on parental history of allergy, maternal smoking, and socioeconomic factors. This has to be taken into consideration in evaluations of risk associations between pet exposure and allergic disease in childhood.

Cloning and characterisation of two IgE-binding proteins, homologous to tropomyosin and alpha-tubulin, from the mite Lepidoglyphus destructor

BACKGROUND

The dust mite Lepidoglyphus destructor is a major source of mite allergy in European rural environments, but it also causes allergy in urban populations around the world. We have previously cloned, sequenced and expressed several allergens from L. destructor (Lep d 2, Lep d 5, Lep d 7 and Lep d 13). The aim of this study was to identify and clone additional allergens from L. destructor, and to evaluate their IgE-binding reactivities.

METHODS

PCR and screening with sera from L. destructor-sensitised individuals were used to isolate new clones from a phage display L. destructor cDNA library. The complete coding sequences of the clones were determined and expressed as His(6)-tagged recombinant proteins in Escherichia coli. The recombinant proteins were analysed by SDS-PAGE, immunoblotting and mass spectrometry.

RESULTS

Two new clones, showing homology to tropomyosin and alpha-tubulin in several species, were isolated from the phage display L. destructor cDNA library. Due to its homology to group 10 dust mite allergens, the tropomyosin clone was named Lep d 10. The IgE-binding frequencies of the recombinant Lep d 10 and alpha-tubulin were 13% (18/136) and 12% (11/95), respectively, among subjects with IgE reactivity to mites and/or crustaceans.

CONCLUSIONS

Two new allergens from L. destructor have been identified and can now be added to the repertoire of recombinant L. destructor allergens. In addition, both these allergens belong to highly conserved protein families and may be important for evaluation of allergenic cross-reactivity.

Lep d 2 polymorphisms in wild and cultured Lepidoglyphus destructor mites

We have previously cloned, expressed and characterized two variants of the major allergen Lep d 2 from cultured Lepidoglyphus destructor mites. These variants, Lep d 2.0101 and Lep d 2.0201, differ at 13 amino acid positions. In this study we investigated Lep d 2 sequence diversity between wild and cultured mites. PCR, Southern blot and DNA sequence analysis revealed the presence of two different Lep d 2 genes, one with and one without an intron. In addition, two new variants of Lep d 2, Lep d 2.0102 and Lep d 2.0202, were found at different frequencies in wild and cultured mites. When we expressed the Lep d 2 variants and compared their IgE binding properties by ELISA inhibition, we found that Lep d 2.0102 was a more potent inhibitor than Lep d 2.0101, and to a lesser extent Lep d 2.0202 was more potent than Lep d 2.0201. Long-term cultures of peripheral blood mononuclear cells were used to assess the ability of the expressed Lep d 2 variants to induce cytokine release. Although cells from different individuals released different amounts of interferon-gamma and interleukin-5, no consistent cytokine release pattern could be linked to any specific Lep d 2 variant. In conclusion, we show that both cultured and wild Lepidoglyphus destructor mites contain the same pattern of polymorphism. Furthermore, this Lep d 2 sequence diversity seems not to have any significant impact on the allergens IgE binding or its ability to induce T cell cytokine release.

Mast cell tryptase and hemolysis after trauma

BACKGROUND

We have previously found increased mast cell tryptase in accidental deaths due to trauma, indicating that mast cell degranulation had occurred. The present study was designed to confirm the previous observation and to determine if tryptase release after trauma is acute or delayed. Furthermore, the importance of hemolysis and direct trauma to the mast cells was investigated.

MATERIALS AND METHODS

Mast cell tryptase was measured in post-mortem blood from the femoral vein in 27 cases of death from trauma and in 27 control cases by means of a commercially available immunoassay. The trauma cases were further classified into groups with single versus multiple trauma, and groups with short survival time (i.e. death at the scene of the accident) versus longer survival time (death in hospital). In five multi-trauma deaths, blood was sampled locally from the sites of crush injury.

RESULTS

The mean value of tryptase in femoral vein blood was 35.6+/-34.6 microg/l in the entire trauma group and 14.7+/-6.5 microg/l in the controls (P<0.005). In bloody liquid sampled from crush injuries, tryptase was substantially elevated in all cases, with a mean of 227+/-146 microg/l. In cases with short survival time, tryptase was significantly higher than in those who died after several hours or days in hospital (P<0.001). No statistically significant difference was seen between multi- and single-trauma cases. A correlation between hemolysis in the samples and elevated tryptase was found only in the trauma cases (P<0.05), but experimentally induced hemolysis in vitro was not found to influence the measurements.

CONCLUSION

Mast cell tryptase becomes elevated in trauma deaths and this seems to be ascribable either to direct mechanical injury to tissue mast cells and/or to cell lysis. In patients initially surviving severe injuries, the effects of massive release of histamine and other mast cell mediators might be of importance for treatment strategies and prognosis.

Decreased frequency of intracellular IFN-gamma producing T cells in whole blood preparations from patients with atopic dermatitis

There have been contradictory reports on the shift in the T-cell cytokine expression pattern of peripheral blood mononuclear cells from patients with atopic dermatitis (AD); more specifically the interleukin (IL)-4 and interferon (IFN)-gamma profiles. The aim of this study was to shed further light on this contradiction by measuring the intracellular cytokines IL-4 and IFN-gamma by flow cytometry on unseparated whole blood to obtain results that, as accurately as possible, reflect the situation in circulating cells in vivo. The patient group including 64 patients with AD was compared with 18 nonatopic healthy adults. The results showed that the percentage of CD4+ T cells expressing IFN-gamma was significantly decreased (P < or = 0.001), as well as the percentage expressing IL-4 (P < 0.05) in AD patients compared with healthy controls. Furthermore, in supernatants from whole blood samples stimulated with phorbol 12-myristate 13-acetate and ionomycin, production of IFN-gamma was significantly decreased, while IL-4 production remained unchanged in AD patients compared with healthy controls. We also investigated if there was a relationship between serum IgE level and Phadiatop, a screening test for atopy, vs. the levels of IL-4 and IFN-gamma, but found no correlation with either. However, there was a significant correlation between disease severity and the level of total IgE (r = 0.67, P < 0.05). In conclusion, our results support the evidence for a decreased ability of peripheral CD4+ T cells to produce IFN-gamma among AD patients.