Biomedical subjects

C Schou

Publications and source records attributed to C Schou.

At least 19 recordsLinked to original sources

PubMed2001

Association between quantitative traits underlying asthma and the HLA-DRB1 locus in a family-based population sample.

The region of human chromosome 6 containing the MHC has been identified as influencing asthma and atopy (allergy) by several genome-wide searches. The MHC contains many genes with potential effects on innate and specific immunity. As a first step in dissecting MHC influences on asthma and its underlying quantitative phenotypes, we have examined the HLA-DRB1 locus in a population sample consisting of 1004 individuals from 230 families from the rural Australian town of Busselton. The locus was strongly associated with the (log(e)) total serum IgE concentration, accounting for 4.0% of the sigma(2) (variance) in that trait (multi-allelic test, P=0.00001). The locus also influenced specific IgE titres to common allergens (multi-allelic tests, 2.8% sigma(2) for the house dust mite allergen Der p I, P=0.0013; 3.0% of sigma(2) for Der p II, P=0.0007; and 2.1% of sigma(2) for the cat allergen Fel d I, P=0.014). No associations were found to the categorical phenotype of asthma, or to the quantitative traits of peripheral blood eosinophil counts and bronchial hyper-responsiveness. Transmission disequilibrium tests excluded genetic admixture as a cause of false-positive findings. The results indicate that HLA-DRB1 alleles modulate the total serum IgE concentration and IgE responses to allergens, but do not account for the previous observations of linkage of asthma to the MHC.

Adult↗

PubMed2000

Early stimulation of acidification rate by novel cytotoxic pyridyl cyanoguanidines in human tumor cells: comparison with m-iodobenzylguanidine.

CHS 828, a newly recognized pyridyl cyanoguanidine, has shown promising antitumor activity both in vitro and in vivo and is presently in early phase I clinical trial in collaboration with EORTC. In this study, the effects of CHS 828 and a series of analogues on extracellular acidification and cytotoxicity were compared with those of m-iodobenzylguanidine (MIBG) in human tumor cells. The extracellular acidification rate was measured using the Cytosensor microphysiometer, and determination of cytotoxicity and proliferation was [(14)C] performed by the fluorometric microculture cytotoxicity assay (FMCA) and measurement of [(14)C]thymidine and leucine uptake. CHS 828 significantly increased the acidification rate during the first 15-24 hr in a concentration-dependent manner. This effect was abolished by removal of glucose from the medium, substituted with 10 mM of pyruvate, indicating stimulated glycolysis as the source of the increased acidification rate. However, CHS 828 induced cytotoxicity at concentrations well below those that affected the rate of acidification; when a series of closely related pyridylguanidine analogues were tested and compared, no apparent relationship between cytotoxicity and acidification could be discerned. Furthermore, comparable increases in the acidification rate were evident in one subline with high-grade resistance to the cytotoxic actions of CHS 828. The results indicate that CHS 828 may share the inhibitory actions of MIBG on mitochondrial respiration with a subsequent increase in glycolysis and acidification rate. However, this mechanism of action appears neither necessary nor sufficient to fully explain the cytotoxic actions of CHS 828 in human tumor cells, actions which remain to be mechanistically clarified.

3-Iodobenzylguanidine↗

PubMed2000

Airway eosinophilia is not a requirement for allergen-induced airway hyperresponsiveness.

BACKGROUND: House dust mites (HDMs) are the major source of perennial allergens causing human allergic asthma. Animal models mimicking as closely as possible the allergic features observed in human asthma are therefore interesting tools for studying the immunological and pathophysiological mechanisms involved. Especially the role of eosinophils and allergen-specific immunoglobulin (Ig) E in the pathophysiology of airway hyperresponsiveness (AHR) remains a subject of intense debate. OBJECTIVE: To develop a mouse model of allergic airway inflammation and hyperresponsiveness based on the use of purified house dust mite allergen (Der p 1) as clinical relevant allergen. Furthermore, we studied the effects of low dose allergen exposure on the airway eosinophilia and AHR. METHODS: On day 0, C57Bl/6 mice were immunized with purified Der p 1 intraperitoneally. From day 14-20, the mice were exposed daily to a 30-min aerosol of different concentrations of house dust mite extract. RESULTS: Mice, actively immunized with Der p 1 and subsequently exposed to HDM aerosols, developed AHR, eosinophil infiltration of the airways and allergen-specific IgE. Moreover, lowering the concentration of the HDM aerosol also induced AHR and IgE without apparent eosinophil influx into the airways. Der p 1-sensitized mice exposed to PBS produced IgE, but did not show AHR or eosinophil influx. CONCLUSION: This in vivo model of HDM-induced allergic airway changes suggests that AHR is not related to either eosinophil influx or allergen-specific serum IgE, thereby reducing the importance of these factors as essential elements for allergic AHR.

Allergens↗

PubMed2000

The 18-kDa form of cat allergen Felis domesticus 1 (Fel d 1) is associated with gelatin- and fibronectin-degrading activity.

BACKGROUND: Fel d 1, an important allergen from domestic cats, is a significant cause of asthma. In addition to directly promoting IgE synthesis, other biological activities of allergens may contribute to either allergic sensitization or the magnitude of allergic effector responses. For example, allergens that degrade proteins have been suggested to facilitate allergen presentation by increasing parallelular permeability of airways epithelium. However, little information exists to indicate whether Fel d 1 has other activities relevant to allergic responses. OBJECTIVE: To study whether Fel d 1 is associated with enzyme activity. METHODS: Fel d 1 was obtained by a rigorous purification strategy and its identity confirmed by laser desorption mass spectrometry, cleavage and sequencing. The ability of Fel d 1 to degrade gelatin, fibronectin and the artificial substrate N-benzoyl-FVR-p-nitroanilide was studied. The effect of Fel d 1 on the morphology of tight junctions in epithelial cell monolayers was also investigated. RESULTS: The 18-kDa form of Fel d 1 caused degradation of denatured collagens (gelatin) and cleaved a 20-kDa fragment from the A chain of plasma fibronectin. Catalytic activity was not altered by inhibitors of cysteine peptidases, matrix metallopeptidases or by removal of divalent cations. In contrast, aprotinin and TLCK were inhibitors of Fel d 1. The absence of a serine peptidase catalytic triad in Fel d 1, together with the stoichiometry of the inhibition of TLCK and aprotinin, suggest that their inhibitory action may be due to noncatalytic site interactions. Alternatively, highly purified Fel d 1 may be associated with an active contaminant, although none were found. CONCLUSION: These results suggest that Fel d 1 is another example of a domestic allergen which is associated with enzyme activity. It remains to be established whether the activity resides in Fel d 1 itself or in an unresolved, and possibly related, protein.

Allergens↗

PubMed1999

Dense mapping of chromosome 12q13.12-q23.3 and linkage to asthma and atopy.

BACKGROUND: Asthma is a complex disease characterized by a high prevalence of allergic diathesis and the almost ubiquitous presence of upper airway disease (eg, rhinitis). Previously, we observed linkage of asthma among Afro-Caribbean families to markers in chromosome 12q, which contains a number of genes encoding for products closely related to allergic airway inflammation and disease. OBJECTIVE: To identify susceptibility loci in chromosome 12q contributing to the genetics of upper and lower airway diseases and to expand the region to include genes encoding IFN-gamma (IFNG ) and one of the signal transducers and activators of transcription (STAT6 ), we conducted further linkage studies among 33 multiplex families. METHODS: We characterized 528 subjects from Barbados for asthma; 82% were characterized for allergic rhinitis. Two-point and multipoint linkage analysis of 22 microsatellite markers (spanning approximately 79 centimorgan) was performed. RESULTS: Affected sib-pair analysis revealed significant evidence for linkage to asthma over approximately 30 cM (P <.05 to.002), with the best evidence for linkage at a CA repeat polymorphism in the first intron of IFNG in 12q21.1 (P =.002). Evidence of linkage to allergic rhinitis was observed in the same region (D12S313, P = 0.006, and IFNGCA, P =.01, respectively). Multipoint linkage analysis also provided evidence for linkage to asthma, with the best nonparametric linkage analysis score at D12S326 (nonparametric linkage score = 3.8, P =.0008). Modest evidence for linkage to allergic rhinitis was observed next to D12S326 at D12S1052 (P =.036). CONCLUSIONS: Our findings suggest that (1) one or more loci in the chromosome 12q13. 12-q23.3 region are contributing to the expression of the clinical phenotype asthma and the strongest evidence for linkage is in a region near the gene encoding IFNG and (2) a susceptibility locus for both asthma and allergic rhinitis maps to this region.

Adult↗

PubMed1999

Identification of a highly promiscuous and an HLA allele-specific T-cell epitope in the birch major allergen Bet v 1: HLA restriction, epitope mapping and TCR sequence comparisons.

BACKGROUND: Allergen-specific CD4+ T cells play an important regulatory role in atopic allergy. OBJECTIVE: To investigate the human leucocyte antigen (HLA) restriction and T-cell receptor (TCR) usage of allergen-specific T-cell clones (TCCs) that react with defined epitopes of Bet v 1, the major birch pollen allergen. METHODS: Five Bet v 1-specific TCCs derived from two birch pollen-allergic individuals and specific for Bet v 1, were epitope-mapped with overlapping synthetic peptides. In addition, HLA-restriction and TCR CDR3 sequences were determined. RESULTS: Three TCCs reacted with a Bet v 1 peptide containing amino acid residues 21-33 (BP21), the other two TCCs reacted with a minimal peptide comprising residues 37-45 (BP37). Studies using neutralizing anti-HLA-monoclonal antibodies and HLA-typed APCs showed that the BP37-specific TCCs were restricted by a HLA-DQA1*0301/DQB1*0603 heterodimer. In contrast, BP21 was recognized in a highly promiscuous manner. TCCs recognizing this sequence were restricted by HLA-DPB1*0201, a HLA-DQA1*0201/DQB1*0201 heterodimer, or HLA-DRB3*0101. Reverse transcription-polymerase chain reaction with primers for all known TCRAV and TCRBV gene segments, followed by CDR3 region sequencing, revealed the usage of five different TCRAV and four different TCRBV gene segments by the TCCs, as well as diversity in the joining region. All BP21-specific TCCs contained a negatively charged residue in their CDR3alpha regions, the CDR3beta regions showed a high concentration of polar and OH-group bearing residues. BP37-specific TCCs shared the amino acid combination LY in the middle of their CDR3alpha regions, the CDR3beta regions showed high concentration of OH-group bearing or charged residues. CONCLUSIONS: This study shows the existence of a highly promiscuous T-cell epitope in Bet v 1. The presence of additional T-cell epitopes in Bet v 1 may, however, hamper the clinical applicability of the epitope. Likewise, the diversity in TCR usage by T cells recognizing the epitope does not support the development of TCR-directed immunotherapy for birch pollen allergy.

Alleles↗

PubMed1999

Bacterial binding to extracellular matrix proteins -- in vitro adhesion.

A binding assay was developed and used to study the binding of oral streptococcus to immobilized human fibronectin, laminin, vitronectin, fibrinogen, heparin, and collagen IV. The protein binding was dependent on the broth used for bacterial growth. The binding after growth in brain heart infusion broth, trypticase soy broth, Todd-Hewitt broth, and Dulbecco's modified Eagle's medium was examined. Most of the strains were able to bind to immobilized fibronectin and laminin, and to a minor extent vitronectin. Binding was not observed on immobilized fibrinogen, collagen IV, or heparin. Measured surface hydrophobicity correlated well with the bacterial binding strength to the proteins. Streptococcal incubation with putative inhibitors indicates multiple binding mechanisms of a lectin-like and protein nature, possibly involving protein receptors.

Animals↗

PubMed1999

Genome-wide screen for atopy susceptibility alleles in the Hutterites.

A genome-wide screen for loci influencing positive skin prick tests (SPT) to airborne allergens was conducted in the Hutterites, a founder population of European ancestry. Positive SPT to 14 standardized allergens was measured in 370 subjects in our primary sample and 324 subjects in a replication sample. Evidence for linkage to positive SPT was assessed using the transmission disequilibrium test (TDT) with 337 autosomal markers (average spacing 9.13 cM, SD = 7.8 cM). Three loci showed the strongest overall evidence of linkage to atopy, with at least one allele-specific and a locus-specific p< 1 x 10(-4). This study provides evidence for at least three atopy-susceptibility loci in the Hutterites on chromosomes 1, 6 and 16.

Adult↗

PubMed1998

Characterization of a cellobiose dehydrogenase from Humicola insolens.

The major cellobiose dehydrogenase (oxidase) (CBDH) secreted by the soft-rot thermophilic fungus Humicola insolens during growth on cellulose has been isolated and purified. It was shown to be a haemoflavoprotein with a molecular weight of 92 kDa and a pI of 4.0, capable of oxidizing the anomeric carbon of cellobiose, soluble cellooligosaccharides, lactose, xylobiose and maltose. Possible electron acceptors are 2,6-dichlorophenol-indophenol (DCPIP), Methylene Blue, 3,5-di-t-butyl-1,2-benzoquinone, potassium ferricyanide, cytochrome c and molecular oxygen. The oxidation of the prosthetic groups by oxygen was monitored at 449 nm for the flavin group and at 562 nm for the haem group. The curves were very similar to those of the cellobiose dehydrogenase from Phanerochaete chrysosporium, suggesting a similar mechanism. The pH-optima for the oxidation varied remarkably depending on the electron acceptor. For the organic electron acceptors, the pH-optima ranged from pH 4 for Methylene Blue to pH 7 for DCPIP and the benzoquinone. In the case of the FeIII-containing electron acceptors, the enzyme displayed alkaline pH-optima, in contrast to the properties of cellobiose dehydrogenases from Phanerochaete chrysosporium and Myceliophthora (Sporotrichum) thermophila. The enzyme has optimal activity at 65 degrees C.

Amino Acids↗

PubMed1998

Genetic influences of chromosomes 5q31-q33 and 11q13 on specific IgE responsiveness to common inhaled allergens among African American families. Collaborative Study on the Genetics of Asthma (CSGA).

BACKGROUND: We have recently conducted a genome-wide screening for genes influencing Dermatophagoides pteronyssinus-specific IgE responsiveness as a part of the Collaborative Study on the Genetics of Asthma (CSGA), which showed evidence for linkage in some regions, including chromosomes 5131-q33 and 11q13 in African American families. OBJECTIVES: To clarify relative contributions of these regions to atopy in the same African American population, we have conducted further genetic linkage studies of specific IgE responses toward common inhaled allergens. METHODS: We studied 328 individuals in 58 African American families participating in the CSGA. Specific IgE responses toward Dermatophagoides farinae, cat, dog, American cockroach, rye grass, and Bermuda grass, as measured by skin tests, were used for multipoint linkage analysis with polymorphic markers on chromosomes 5q31-q33 and 11q13. RESULTS: Specific IgE response toward American cockroach showed evidence for linkage to chromosomes 5q31-q33 (P = .0050) and 11q13 (P = .017). Specific IgE response toward dog showed evidence for linkage with chromosome 5q31-q33 (P = .0043). Evidence for linkage with chromosome 11q13 was obtained for specific IgE responses toward Dermatophagoides farinae (P = .012), cat (P = .035), and Bermuda grass (P = .017). The presence of a positive ST response for at least 1 of 30 common allergens showed evidence for linkage to chromosomes 5q31-q33 (P = .017) and 11q13 (P = .00058). CONCLUSIONS: These data support that genes on both chromosomes 5q31-q33 and 11q13 confer susceptibility to upregulated IgE-mediated immune responses in this African American population. The putative genes on chromosomes 5q31-q33 and 11q13, however, showed contrasting effects on atopy, which may result from strong gene-environmental interactions.

Administration, Inhalation↗

PubMed1998

Preserved epitope-specific T cell activation by recombinant Bet v 1-MBP fusion proteins.

BACKGROUND: Allergen-specific T cells play an important role in the allergic immune response, and are thought to be the principal target in specific immunotherapy. OBJECTIVE: The aim of the present study was to evaluate if fusion proteins of allergens with bacterial proteins can be used to activate and bias allergen-specific T cells, and to characterize T cell epitopes. METHODS: The complete gene of Bet v 1, the major birch pollen allergen, was amplified by PCR from birch pollen mRNA, and cloned in pKK223-3. The complete gene or truncated sequences were transferred to pMAL-c and expressed in E. coli as fusion proteins with maltose binding protein (MBP). The complete fusion protein, and the truncated fusion proteins were used for studies with Bet v 1-specific T cells. RESULTS: Bet v 1-specific T cells reacted similarly with purified and crude Bet v 1-MBP proteins. Therefore, crude preparations were used to study the epitope-specificity of 11 Bet v 1-specific T cell clones. Six distinct T cell epitopes were determined in this way. Interestingly, the T cell epitope of three T cell clones, that did not react with synthetic peptides in a previous study, was identified. In addition, the presence of MBP as a fusion partner to Bet v 1 was shown to influence TH2/TH1 cytokine production in T cell lines, but not in established T cell clones. CONCLUSION: Using crude preparations of recombinant fusion proteins of Bet v 1 with MBP, multiple T cell epitopes were identified in Bet v 1. As T cell activation is preserved in this system, the generation of recombinant allergens with TH1-inducing proteins as fusion partners might be considered as a T-cell targeted approach for specific immunotherapy.

ATP-Binding Cassette Transporters↗

PubMed1998

Purified Der p1 and p2 patch tests in patients with atopic dermatitis: evidence for both allergenicity and proteolytic irritancy.

Atopic dermatitis has many similarities with allergic contact dermatitis. Previous studies have revealed delayed-type allergic reactions indicating specific cell-mediated immune reactions in subgroups of patients. It has recently been recognized that purified house dust mite major allergens, Der p1 and Der p2 from Dermatophagoides pteronyssinus, exhibit a proteolytic enzyme activity similar to papain and maybe serine proteases (e.g. trypsin), respectively. This opens the possibility that house dust mites apart from an allergic epitope could elicit irritant reactions in atopic skin. We examined cutaneous reactivity to the purified proteins of house dust mite antigens, Der p1 and Der p2, in 36 consecutive patients with atopic dermatitis. We also patch-tested with trypsin and papain, in order to see if these proteolytic enzymes could induce irritant reactions. Twelve patients had type 1 allergy to Der p1 and two of these had type IV reactivity to D. pteronyssinus extract. Positive reactions were observed in another four patients, but they had also irritant reactions to papain and trypsin, indicating that the enzymatic activity may have elicited the reactions. The cutaneous reactivity was not linked to total serum IgE, but the patients with specific allergic patch tests had type I reactions to D. pteronyssinus extract. Our observations indicate that allergic patch tests towards Der p1 and p2 are rare and that irritant reactions from D. pteronyssinus proteolytic activity may be a more common phenomenon when patch-testing atopic dermatitis patients with house dust mite antigen extract.

Adolescent↗

PubMed1998

Environmental assessment of Dermatophagoides mite-allergen levels in Sweden should include Der m 1.

The major allergen of Dermatophagoides microceras, Der m 1, as well as the allergens of D. pteronyssinus and D. farinae, Der p 1 and Der f 1, were analyzed in the homes of 111 asthmatic children in three climatic regions in Sweden. The numbers and species of mites were determined by microscopy, and circulating IgE antibodies against mites were measured. Der f 1 was the predominant house-dust-mite (HDM) allergen, Der p 1 the least often found, and Der m 1 represented 31% of the allergen load. However, in the Linköping area, Der m 1 was the major HDM allergen (58%). Mite counts and allergen levels correlated well. Current exposure to HDM allergens at home was associated with the serum IgE antibody response to HDM in the children with no threshold level. Of the children with IgE antibodies against HDM, 67% reacted to all three mites. Mite sensitization rates were marginally increased (7%) by the addition of IgE analysis of D. microceras to the routine analysis of IgE antibodies against D. pteronyssinus and D. farinae. Thus, Der m 1 may be an important HDM allergen and should be considered when HDM exposure data are assessed in areas with a climate like that of Sweden.

Adolescent↗

PubMed1998

Quantitative assessment of immediate cutaneous hypersensitivity in a model of genetic predisposition to atopy.

Genetic predisposition and environmental factors modulate the expression of allergic phenotypes. The frequent allergic phenotype 'immediate cutaneous hypersensitivity' was established in mice as a model for atopy. Genetic dissection of this trait requires a robust procedure to assess the allergic phenotype. To this end, different mouse strains were immunized with birch pollen extract. Immediate cutaneous hypersensitivity reactions were induced through intradermal allergen exposure. Wheel formation was quantitated and expressed as a hypersensitivity score according to the bonitur method. This procedure identified A/J and C57BL/6 mice as high- and low-responder strains, respectively. Crosses of A/J and C57BL/6 mice should allow the characterization of mendelian factors responsible for the two extreme phenotypes identified here.

Allergens↗

PubMed1997

Germline TCR-A restriction of immunoglobulin E responses to allergen.

Immunoglobulin E responses to known environmental antigens (allergens) may serve as a general model to investigate germline genetic restriction of the immune response. We have previously shown genetic linkage between IgE responses to major allergens and the T-cell receptor (TCR) A/D locus, but not to TCR-B, implying that elements in TCR A/D restrict the ability to react to specific antigens. We now show, in two sets of subjects from the same population, a strong allelic association between a VA8.1 polymorphism (VA8.1(*)2) and reactivity to Der p II, a major antigenic component of the house dust mite Dermatophagoides pteronyssinus. Association was also seen between Der p II IgE titres and HLA-DRB1(*)1501 alleles. Reactivity to Der p II was confined to subjects who were positive for VA8.1(*)2 and HLA-DRB1(*)1501, demonstrating germline HLA-DR and TCR-A interaction in restricting the response to exogenous antigen.

Allergens↗

PubMed1997

Cockroach allergen in house dust.

The cockroach allergen (Bla g 1) content was determined in the floor dust of 46 homes with recent cockroach extermination in Amsterdam, The Netherlands. IgE antibodies to Blattella germanica, house-dust mite, cat dander, dog dander, and a mixture of molds were determined in venous blood samples of 46 children (4-12 years) and one of their biologic parents (24-54 years). Specific IgE to cockroach was also determined in a sample of the general population studied in a previous case-control study, one group (n = 20) with three groups (n =76) without history of cockroach infestation of the home. Cockroach allergen was detected in floor dust from 44% of the homes, with levels up to 3899 ng Bla g 1/g. Seven of the 46 adults and only one of the 46 children studied had positive RAST to cockroach. Geometric mean cockroach allergen concentrations in living room and master bedroom of sensitized adults were similar to those of nonsensitized adults. In the groups of children without a history of cockroach infestation of the home, positive RAST against cockroach was observed in 16% of the children with respiratory symptoms, in 4% of the children without respiratory symptoms, and in 48% of the children with two or more positive RAST to other allergens. Of the 18 children with positive RAST against cockroach, only one had a history of cockroach infestation of the home and 16 (89%) had also positive RAST against house-dust mite.

Adult↗

PubMed1997

Mucinous adenocarcinoma of the sublingual gland.

A case of mucinous (colloid) adenocarcinoma of the sublingual gland is reported. Adenocarcinomas associated with large pools of extracellular mucin are extremely rare in the major salivary glands. Analysis of the tumor for cytokeratin expression, estrogen and progesterone receptors was performed. Predominantly, the tumor expressed cytokeratins 7, 8, 18 and 19 that are commonly found in simple epithelia, and to a lesser degree cytokeratins 4 and 13 which are usually found in complex epithelia. Staining for estrogen and progesterone receptors was negative. No other cancer has been detected for three years after the first examination. The tumor is considered to be a primary mucinous adenocarcinoma of the sublingual gland.

Adenocarcinoma, Mucinous↗

PubMed1997

Determination of isoforms, N-linked glycan structure and disulfide bond linkages of the major cat allergen Fel d1 by a mass spectrometric approach.

The domestic cat (Felis domesticus) is an important source of indoor allergens, the major allergen being Fel d1 (formerly cat allergen 1). Fel d1 is responsible for cat allergy and has also been established to cause cat-induced asthma. The allergen is a 38 kDa dimer composed of two 19 kDa subunits. Each 19 kDa subunit comprises two disulfide linked polypeptide chains, a light alpha-chain and a heavy beta-chain containing an N-linked oligosaccharide. In this study a variety of endoproteinase digestions of the native allergen in combination with HPLC and matrix-assisted laser desorption mass spectrometry was used to determine the position of the disulfide bridges and to demonstrate that the peptide chains are linked in an anti parallel way. Enzymatic digestion of the reduced and alkylated peptides located the N-glycan to Asn33. Moreover, Fel d1 is found to be partially truncated and to exist in several isoforms. Sequential degradation of the glycosylated peptide with specific glycosidases monitored by mass spectrometry, shows that the glycan is a heterogeneous triantennary complex type structure. The heterogeneity is caused by terminal sialic acid and a fucose residue attached to a beta-galactose residue.

Alkylation↗