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Biomedical subjects

R van Ree

Publications and source records attributed to R van Ree.

At least 19 recordsLinked to original sources
PubMed2001

A case of allergy to beer showing cross-reactivity between lipid transfer proteins.

BACKGROUND: Lipid transfer proteins (LTPs) are highly conserved proteins present in a broad spectrum of fruits and vegetables that might represent a novel plant panallergen. OBJECTIVE: To demonstrate that LTP is an important allergen in beer and that beer LTP cross-reacts with LTP from botanically unrelated plant-derived foods. METHODS: Serum from a patient with clinical allergy to both beer and Rosaceae was studied for IgE reactivity to LTP to several vegetable foods by RAST, ELISA, immunoblot, and inhibition studies. RESULTS: Patient's serum showed a strong IgE reactivity to LTP purified from peach peel, carrot, and broccoli, and to a 10 kD protein in both apple and peach immunoblots, whereas no reactivity to birch cross-reactive allergens such as Bet v 1, profilin, or carbohydrates was found. In inhibition studies, preabsorption of serum with apple, walnut, hazelnut, peanut, corn, and rice caused a fall of 97%, 20%, 66%, 91%, 94%, and 93%, respectively, of its reactivity to peach LTP. Beer RAST fell from 1.8 IU/mL to <0.1 IU/mL when a patient's serum was preabsorbed with recombinant carrot LTP. CONCLUSIONS: LTP is a relevant allergen in beer. Beer LTP may cross-react with LTP from several other plant-derived foods.

Adult↗
PubMed2001

Structural aspects of cross-reactivity and its relation to antibody affinity.

In the context of IgE/allergen interactions, affinity is largely determined by the stability of the allergen-IgE complex: a low affinity is usually equated with a rapid dissociation of the complex. Regular solid-phase assays are not well suited for affinity estimates because of multivalency effects, "unstirred layer" effects and "invisible" antibodies. Elution of IgE bound to solid-phase coupled allergen might be a good measure of intrinsic affinity, provided that reassociation of antibodies is prevented by a high concentration of soluble allergen. Allergen-mediated IgE-dependent triggering of a mast cell is presumably a two-step process. During the first step, the allergen is bound to a cell-bound IgE antibody and dragged over the cell surface. The second step is the interaction between this cell-bound allergen and another IgE antibody. The hypothesis is that the affinity requirements for the first step are higher than for the second. The implication is that a mast cell can be triggered by a single high-affinity antibody in combination with one or more low-affinity antibodies.

Allergens↗
PubMed2001

Cross-reactivity of IgE antibodies to allergens.

The cross-reactivity of IgE antibodies is of interest for various reasons, three of which are discussed. Firstly, from the clinical view, it is important to know the patterns of cross-reactivity, because they often (but not always) reflect the pattern of clinical sensitivities. We discuss the cross-reactivities associated with sensitization to pollen and vegetable foods: PR-10 (Bet v 1-related), profilin, the cross-reactive carbohydrate determinant (CCD), the recently described isoflavone reductase, and the (still elusive) mugwort allergen that is associated with celery anaphylaxis; cross-reactivities between allergens from invertebrates, particularly tropomyosin, paramyosin, and glutathione S-transferase (GST); and latex-associated cross-reactivities. Clustering cross-reactive allergens may simplify diagnostic procedures and therapeutic regimens. Secondly, IgE cross-reactivity is of interest for its immunologic basis, particularly in relation to the regulation of allergic sensitization: are IgE antibodies to allergens more often cross-reactive than IgG antibodies to "normal" antigens? If so, why? For this discussion, it is relevant to compare not only the structural relation between the two allergens in question, but also the relatedness to the human equivalent (if any) and how the latter influences the immune repertoire. Thirdly, prediction of IgE cross-reactivity is of interest in relation to allergic reactivity to novel foods. Cross-reactivity is a property defined by individual antibodies to individual allergens. Quantitative information (including relative affinity) is required on cross-reactivity in the allergic population and with specific allergens (rather than with whole extracts). Such information is still scarce, but with the increasing availability of purified (usually recombinant) allergens, such quantitative information will soon start to accumulate. It is expected that similarity in short stretches of the linear amino-acid sequence is unlikely to result in relevant cross-reactivity between two proteins unless there is similarity in the protein fold.

Allergens↗
PubMed2001

Immunochemical characterization of two Pichia pastoris-derived recombinant group 5 Dactylis glomerata isoallergens.

BACKGROUND: Grass pollen of the Poaceae grasses are known to be highly allergenic. Major allergens from the species Lolium, Phleum, Poa and Holcus have been cloned and expressed as recombinant proteins, but of the important species Dactylis glomerata no recombinants are available. METHODS: Dac g 5 was cloned by PCR on the basis of homology with Lol p 5 and expressed in Pichia pastoris. Recombinant Dac g 5 (rDac g 5) was affinity purified and compared to natural Dac g 5 (nDac g 5) by immunoblot, radioallergosorbent test (RAST), RAST inhibition, basophil histamine release assay (HRA), competitive radioimmunoassay (RIA) and sandwich enzyme-linked immunosorbent assay (ELISA). In addition, N-terminal sequencing, concanavalin A (Con A) binding, circular dichroism spectrum measurements and matrix-assisted laser desorption ionization-time of flight mass-spectrometric analysis were performed. RESULTS: Clones were obtained that coded for pro-Dac g 5 and two mature isoforms of Dac g 5; the deduced amino acid sequences of both isoforms differed by 4 amino acids. Both mature isoforms were expressed in Pichia at a concentration of approximately 15 mg/l. SDS-PAGE analysis showed that rDac g 5 had an apparent M(r) approximately 10 kD above nDac g 5. By mass spectrometry this difference was shown to be around 2.5 kD. Positive Con A staining suggested (O-linked) glycosylation as an explanation for this increase in M(r). Whereas both purified recombinants showed a tendency to dimerize, purified nDac g 5 contained a 12-kD peptide not observed for rDac g 5. RAST, RAST inhibition and HRA showed that the IgE reactivity of rDac g 5 was similar to that of nDac g 5. A small subgroup, however, clearly demonstrated decreased IgE reactivity to rDac g 5.02. Differences in immune reactivity of both isoforms were confirmed by monoclonal antibody (mAb)-based sandwich ELISA. CONCLUSIONS: Dac g 5 was successfully cloned and expressed in P. pastoris. Minor differences in primary structure between isoforms influence their immune reactivity.

Allergens↗
PubMed2001

The prevalence of parasite infestation and house dust mite sensitization in Gabonese schoolchildren.

BACKGROUND: Allergic diseases seem less prevalent in communities in less developed parts of the world, where parasite infections are highly prevalent. Altogether not much is known about the association between chronic infections with tissue and blood-dwelling parasites and atopy. METHODS: In an area in Gabon endemic for blood and tissue parasites, 520 schoolchildren were parasitologically examined and skin prick-tested for a set of common environmental aeroallergens. Levels of allergen-specific IgE and polyclonal IgE were measured. RESULTS: In schoolchildren schistosome and filarial infections increased with age, whereas malaria was more prevalent in younger children. In contrast to allergen sensitization that increased with age, skin test reactivity tended to decline. The number of children with mite-specific IgE antibodies (47%) by far exceeded the number responding to skin prick testing (11%). Mite sensitization was found to be the highest in children infected with schistosomes and/or filariae whereas skin test reactivity was lowest. The multiple logistic regression showed that the risk of a positive skin test was 8-fold higher with increasing levels of mite-specific IgE but was reduced by 72% when infected with blood stage helminths. CONCLUSIONS: Chronic blood and tissue parasite infections that are often capable of modulating immune responses in the host are negatively associated with skin test reactivity in a sensitized population.

Adolescent↗
PubMed2000

Decreased atopy in children infected with Schistosoma haematobium: a role for parasite-induced interleukin-10.

BACKGROUND: Most of the effort directed at understanding the role infections have in preventing allergy has focused on bacteria and viruses and their ability to divert the immune system towards T-helper-1 responses and away from proallergic T-helper-2 responses. However, helminth infections, highly prevalent in large parts of the developing world, where allergy is uncommon, stimulate strong T-helper-2 responses. We investigated the influence of chronic helminth infections on the prevalence of atopy and aimed to understand the relation at a detailed immunological level. METHODS: 520 Gabonese schoolchildren were tested for skin reaction to house-dust mite and other allergens, for Schistosoma haematobium eggs in urine, and for microfilariae in blood samples. Total and mite-specific IgE antibodies were measured. A subsample selected on the basis of their skin test to house-dust mite received detailed immunological investigations. FINDINGS: Children with urinary schistosomiasis had a lower prevalence of a positive skin reaction to house-dust mite than those free of this infection (odds ratio 0.32 [95% CI 0.16-0.63]). The degree of sensitisation to house-dust mite could not explain this difference in skin-prick positivity. Schistosome-antigen-specific concentrations of interleukin-10 were significantly higher in infected children, and higher specific concentrations of this anti-inflammatory cytokine were negatively associated with the outcome of skin-test reactivity to mite (0.53 [0.30-0.96]). No association between polyclonal IgE antibodies and skin-test results was found. INTERPRETATION: The anti-inflammatory cytokine, interleukin-10, induced in chronic schistosomiasis, appears central to suppressing atopy in African children.

Adolescent↗
PubMed2000

Beta(1,2)-xylose and alpha(1,3)-fucose residues have a strong contribution in IgE binding to plant glycoallergens.

Primary structures of the N-glycans of two major pollen allergens (Lol p 11 and Ole e 1) and a major peanut allergen (Ara h 1) were determined. Ole e 1 and Ara h 1 carried high mannose and complex N-glycans, whereas Lol p 11 carried only the complex. The complex structures all had a beta(1,2)-xylose linked to the core mannose. Substitution of the proximal N-acetylglucosamine with an alpha(1, 3)-fucose was observed on Lol p 11 and a minor fraction of Ole e 1 but not on Ara h 1. To elucidate the structural basis for IgE recognition of plant N-glycans, radioallergosorbent test analysis with protease digests of the three allergens and a panel of glycoproteins with known N-glycan structures was performed. It was demonstrated that both alpha(1,3)-fucose and beta(1,2)-xylose are involved in IgE binding. Surprisingly, xylose-specific IgE antibodies that bound to Lol p 11 and bromelain did not recognize closely related xylose-containing structures on horseradish peroxidase, phytohemeagglutinin, Ole e 1, and Ara h 1. On Lol p 11 and bromelain, the core beta-mannose is substituted with just an alpha(1,6)-mannose. On the other xylose-containing N-glycans, an additional alpha(1,3)-mannose is present. These observations indicate that IgE binding to xylose is sterically hampered by the presence of an alpha(1,3)-antenna.

Allergens↗
PubMed2000

Lipid transfer protein: a pan-allergen in plant-derived foods that is highly resistant to pepsin digestion.

BACKGROUND: Lipid transfer proteins (LTPs) are small molecules of approximately 10 kD that demonstrate high stability. They have recently been identified as allergens in the Rosaceae subfamilies of the Prunoideae (peach, apricot, plum) and of the Pomoideae (apple). They belong to a family of structurally highly conserved proteins that are also present in non-Rosaceae vegetable foods. OBJECTIVE: The aim of this study was to investigate the cross-reactivity to non-Rosaceae LTPs, and to study the role of protein stability in allergenicity. METHODS: Thirty-eight patients with a positive SPT to Rosaceae fruit extracts enriched for LTP were characterized by interview and SPT. To investigate IgE cross-reactivity between Rosaceae and non-Rosaceae LTPs, RAST and RAST inhibition as well as ELISA and ELISA inhibition were performed, using whole food extracts and purified LTPs. Both purified natural LTPs (peach, carrot and broccoli) and Pichia pastoris recombinant LTPs (carrot and wheat) were included. Pepsin digestion was used to address the role of stability in the allergenicity of LTPs. RESULTS: IgE antibodies to Rosaceae LTPs reacted to a broad range of vegetable foods, including Gramineae (cereals), Leguminosae (peanut), Juglandaceae (walnut), Anacardiaceae (pistachio), Brassicaceae (broccoli), Umbelliferae (carrot, celery), Solanaceae (tomato), Cucurbitaceae (melon), and Actinidiaceae (kiwi). Binding and inhibition studies with purified natural and recombinant LTPs confirmed their role in this cross-reactivity. Many of these cross-reactivities were accompanied by clinical food allergy, frequently including systemic reactions. Antibody binding to LTP was shown to be resistant to pepsin treatment of whole extract or purified LTP. CONCLUSION: LTP is a pan-allergen with a degree of cross-reactivity comparable to profilin. Due to its extreme resistance to pepsin digestion, LTP is a potentially severe food allergen.

Adolescent↗
PubMed2000

A sensitive monoclonal antibody sandwich ELISA for the measurement of the major olive pollen allergen Ole e 1.

BACKGROUND: Olive pollen is a major cause of inhalant allergy in countries around the Mediterranean sea. The major allergen of olive pollen is Ole e 1. Measurement of the major allergen content of allergen products for diagnosis and therapy is becoming an essential element of standardization protocols. This study aimed at the development of a monoclonal antibody (mAb) sandwich ELISA for Ole e 1. METHODS: Balb/c mice immunized with Ole e 1 were used for the production of mAbs. Screening of mice and hybridomas was performed in a RIA with radiolabeled purified Ole e 1. Purified mAbs were used as catching and/or (biotinylated) detecting antibodies in sandwich ELISA. RESULTS: Four mAbs (IgG1kappa) directed to nonoverlapping epitopes on Ole e 1 were obtained: 1A12, 5C1, 10A12 and 3H8. Both 1A12 and 10A12 were successfully used for affinity purification of Ole e 1 from olive pollen extract. Two sandwich ELISAs were developed, with 1A12 and 10A12 as catching, and 5C1 and 3H8 as detecting antibodies, respectively. Both catching and detecting antibodies were used in similar concentrations, ranging from 60 to 100 ng/well. For both ELISAs, the sensitivity was approximately 1 ng/ml of Ole e 1. The measuring range was from 1 to 25 ng/ml. No significant differences were observed, when the performance of both ELISAs in standardization of olive pollen extracts was compared. CONCLUSIONS: Two sensitive sandwich ELISAs for the major olive pollen allergen Ole e 1 were developed. They will prove to be useful tools in allergen standardization protocols.

Allergens↗
PubMed1999

Purified natural and recombinant Fel d 1 and cat albumin in in vitro diagnostics for cat allergy.

BACKGROUND: Current diagnostics and therapeutics for cat allergy are based on cat epithelial extracts originating from highly variable source materials. This gives rise to several problems: variability of allergen composition, contamination with house dust mite allergens, and potential transfer of pathogenic agents. OBJECTIVE: The aim of this study was to investigate the feasibility of replacing cat epithelial extracts with purified natural or recombinant allergens. METHODS: Sera (n = 509) were selected on the basis of a positive cat RAST result and tested in a RAST for IgE reactivity to purified Fel d 1, cat albumin (CA), or both. The analysis was performed with both natural and recombinant allergens. In addition, some sera were further analyzed by means of immunoblotting. A serum pool was used for cat RAST inhibition with purified natural and recombinant allergens as inhibitors. RESULTS: Natural and recombinant Fel d 1 caused very similar results: 94.1% and 96.1% positive test results, respectively. In general, the negative sera were low responders to cat extract. The addition of CA (16.7% positive sera) resulted in a decrease in the number of discrepencies between purified allergens and whole extract to 2.8%. Only for 2% of all sera, sensitization to cat was largely explained by IgE reactivity to CA. IgE reactivity to Fel d 1 accounts for 88% of the total IgE response to cat allergens, as was demonstrated by RAST, with Fel d 1 concentrations nearing saturation. Recombinant Fel d 1 performed equally well in the RAST analysis. Recombinant CA was succesfully expressed in the yeast Pichia pastoris, and its immune reactivity closely resembled that of its natural counterpart. CONCLUSION: Natural and recombinant Fel d 1 and CA are good candidates for replacing ill-defined cat dander extracts in diagnostics for cat allergy. Although CA is not essential for the vast majority of cat-sensitized patients, some subjects are selectively sensitized to this serum protein.

Allergens↗
PubMed1998

How far can we simplify in vitro diagnostics for grass pollen allergy?: A study with 17 whole pollen extracts and purified natural and recombinant major allergens.

BACKGROUND: Current diagnostics for grass pollen allergy are composed of mixtures of pollen of different grass species. Their complex composition hampers accurate standardization. OBJECTIVE: The aim of the study was to investigate whether mixtures of grass pollen extracts can be replaced by a single pollen species and whether a single pollen species can be replaced by a limited number of purified natural or recombinant major allergens. METHODS: Sera (n = 800) were selected on the basis of a general suspicion for inhalant allergy and tested in a RAST for IgE reactivity with pollen from 17 different grass species. Cross-reactivity of IgE responses was studied by means of RAST inhibition. Sera with positive test results for grass pollen were tested in a RAST for natural Lol p 1 and Lol p 5 and recombinant Phl p 1 and Phl p 5. RESULTS: Specific IgE antibodies against one or more of the 17 pollen species were detected in 209 of 800 sera (26.1%). The highest responses were observed against Poa pratensis followed by Festuca rubra, Phleum pratense, and Dactylis glomerata. IgE responses were clearly lower (approximately by a factor of 5) against only three species (Phragmites communis, Cynodon dactylon, and Zea mays). With the exception of a few low-responder sera, no sera were found to have negative test results to the high responder species and positive results to any of the other species. Sera with positive test results for grass pollen (n = 154) were tested with purified Lol p 1 and Lol p 5. IgE anti-Lol p 1 and Lol p 5 accounted for an average of 81% +/- 7% of total anti-grass pollen IgE. For 14 sera (all with low anti-grass pollen IgE titers), a RAST with purified allergens resulted in a false-negative diagnosis for grass pollen allergy. With recombinant Phl p 1 and Phl p 5, the mean IgE reactivity was 57% +/- 6% of the anti-grass pollen IgE response (n = 141), with 13 false-negative results. CONCLUSION: One grass species is sufficient for in vitro diagnosis of grass pollen allergy. With purified natural Lol p 1 and Lol p 5, greater than 90% of grass-positive sera is detected. Around 80% of the IgE response to grass pollen is directed to these major allergens. Recombinant allergens, produced in Escherichia coli, did not equal the IgE-binding capacity of their natural counterparts.

Allergens↗
PubMed1998

Immune-reactivity of recombinant isoforms of the major house dust mite allergen Der p 2.

BACKGROUND: Recombinant Der p 2, expressed in yeast, lacked reactivity with 5 monoclonal antibodies against natural Der p 2. OBJECTIVE: The aim of this study was to investigate whether the lack of reactivity with recombinant Der p 2 can be explained by the existence of isoforms. METHODS: By site-directed mutagenesis three recombinant isoforms of Der p 2 were produced. Reactivity with monoclonal antibodies and human IgE was analysed by means of RAST and RAST-inhibition. RESULTS: All five monoclonals that lacked reactivity with the originally selected isoform, showed reactivity upon replacement of aspartic acid by asparagine at position 114. The other two substitutions (at position 26 and 47) had no effect. Binding of human IgE (n = 10) was not significantly influenced by the isogenetic variation at position 114. CONCLUSIONS: Monoclonal antibodies raised against natural Der p 2 can sometimes discriminate between different isoforms, allowing the study of the natural occurrence of isoforms. For application in allergen-measurement assays, non-discriminating monoclonal antibodies should be selected.

Animals↗
PubMed1998

Epitope mapping of the house-dust-mite allergen Der p 2 by means of site-directed mutagenesis.

Recombinant Der p 2, expressed in the baker's yeast Saccharomyces cerevisiae, was used as a tool to determine IgE- and monoclonal antibody (mAb)-binding sites on this allergen. For this purpose, mutant molecules were produced by application of site-directed mutagenesis. The amino-acid residues spanning cys21-cys27 and cys73-cys78 were deleted, thus preventing loop formation through disulfide bonds. Charged residues in three predicted antigenic sites (residues 45-48, 67 + 69, and 88-90) were replaced by alanine residues, IgE- and mAb reactivity to these mutants was compared to that to "wild type" Der p 2. Residues spanning cys73-cys78 were involved in the antigenic binding site for mAb alpha DpX. Mutations in the areas adjacent to this loop (i.e., 67 + 69 and 88-90) had similar effects on this mAb (10- to 20-fold decreases in reactivity were observed), supporting the suggestion that these areas are involved in this antigenic structure. The area of residues 45-48 was shown to be involved in an epitope for mAb 2B12. The reactivity of mAb 7A1 was influenced by substitutions of residues 45-48 as well as 88-90. Deletion of the residues spanning cys21-cys27 resulted in decreased reactivity to three mAbs (10E11, alpha DpX, and 7A1). From these observations, it may be concluded that binding of different mAbs is influenced by the same mutations and that the binding of single mAbs is influenced by two or more mutations scattered over the allergen molecule. These findings can point in two directions: minor amino-acid changes result in disruption of the overall conformation of the allergen, or distant sites are close together in the three-dimensional structure of the allergen. Decreased IgE reactivity was observed with all mutant molecules, varying between patients. The observed effects ranged from 5- to 1000-fold. Deletion of the amino-acid residues spanning cys21-cys27 and cys73-cys78 had the strongest effect on IgE reactivity, where decreases up to 1000-fold were observed. Such mutants might be useful tools to improve the safety of allergen-specific immunotherapy.

Allergens↗
PubMed1998

Standardization of in vivo and in vitro diagnostic procedures in food allergy.

For most foods, true standardization is not yet feasible because there is insufficient information on the relative importance of individual allergens and their variants. Standardization without sufficient information may easily be counterproductive because improvements are less likely to be implemented. In the analysis of natural test material, the following principles apply: 1) RAST inhibition is usually inferior to other means of allergen quantitation. 2) Immunoblot is inefficient for some "important" allergens and overefficient for some "unimportant" allergens and may therefore be deceptive. 3) Single-component assays are the only satisfactory way to describe complex mixtures. Improving the actual food-testing procedure is important, but will not alone result in a reliable diagnostic procedure. Tests for measuring "effect modifiers" will have to be developed in order to predict in vivo reactions to foods.

Allergens↗