Differential storage of hydroxyethyl starch (HES) in the skin: an immunoelectron-microscopical long-term study

Hydroxyethyl starch (HES) is widely used as a plasma substitute. Serious side effects occur only rarely, whereas a high incidence of severe pruritus has been reported. Moreover, tissue storage of HES has been demonstrated in various organs. The aim of the current study has been to examine precisely the intracellular uptake and long-term storage of HES in the skin. Skin biopsies from 119 patients who received HES of various preparations and cumulative dosage were obtained 30 min to 130 months after infusion therapy. The samples were analysed by ultrastructural and immunoelectron microscopy with HES-specific monoclonal and polyclonal antibodies. A characteristic vacuolisation of perivascular histiocytes was a regular finding in all skin biopsies as early as 1 day after a single infusion of 30 g. Immunoreactivity for HES was demonstrable within the vacuoles. Generally, the size and number of vacuoles in the histiocytes increased concomitantly with the cumulative dosage. Following administration of higher HES dosages, vacuoles were demonstrable in endothelial cells of blood and lymphatic vessels, basal keratinocytes, epithelia of sweat glands and in small peripheral nerves, the last mentioned being associated with pruritus. A subsequent reduction of the vacuoles in size and number could be demonstrated within 52 months. In nerves, HES deposits persisted no longer than 17 months paralleling the cessation of pruritus. Biopsies taken after 94 months exhibited no HES deposits in the skin. The condensation and final dissolution of the vacuoles may either indicate the release and subsequent redistribution of HES into the circulation or lysosomal degradation.

Recombinant dissection of myosin heavy chain of Toxocara canis shows strong clustering of antigenic regions

Myosins from nematode parasites elicit strong humoral and cellular immune responses and have been investigated as vaccine candidates. In this study we cloned and sequenced a cDNA coding for myosin heavy chain from Toxocara canis, a nematode parasite of canids which may also infect humans and cause various unspecific symptoms. To determine the major antigenic regions the myosin heavy chain was systematically dissected into ten overlapping recombinant fusion polypeptides which were purified by metal chelate chromatography. Single fragments were then tested for their IgG reactivity in sera from toxocarosis patients and healthy probands. Two regions, one region at the mid to carboxy-terminal end of the head domain and one region in the rod domain, were identified as major antigens, which in combination were positive with 86% of the sera. The other domains were less reactive. This shows that the patients' IgG reactivity was not directed evenly against all parts of the molecule, but was rather clustered in few regions.

Preventing recurrent depression using cognitive therapy with and without a continuation phase: a randomized clinical trial

BACKGROUND

Cognitive therapy (CT) may reduce depressive relapse and recurrence when patients learn and use the associated skills. Reported relapse and recurrence rates after CT discontinuation vary widely. The factors that determine when CT is preventive remain unidentified. We developed continuation-phase CT (C-CT) to teach responders skills to prevent relapse. This is the first randomized trial comparing CT with and without a continuation phase in responders to CT who were vulnerable, given their history of recurrent unipolar depression.

METHODS

Patients aged 18 to 65 years (n = 156) with recurrent DSM-IV major depressive disorder (MDD) entered 20 sessions of acute-phase CT (A-CT). Unmedicated responders (ie, no MDD and 17-item Hamilton Rating Scale for Depression score < or =9; n = 84) were randomized to either 8 months (10 sessions) of C-CT or control (evaluation without CT). Follow-up lasted an additional 16 months. A clinician blind to assignment evaluated relapse and recurrence (ie, DSM-IV MDD).

RESULTS

Over an 8-month period, C-CT significantly reduced relapse estimates more than control (10% vs 31%). Over 24 months, including the CT-free follow-up, age of onset and quality of remission during the late phase of A-CT each interacted with condition assignment to influence durability of effects. In patients with early-onset MDD, C-CT significantly reduced relapse and recurrence estimates (16% vs 67% in control). When patients had unstable remission during late A-CT, C-CT significantly reduced relapse and recurrence estimates to 37% (vs 62% in control).

CONCLUSIONS

Findings suggest that 8 months of C-CT significantly reduces relapse and recurrence in the highest-risk patients with recurrent MDD. Risk factors influenced the necessity for C-CT.

Oligodeoxynucleotides containing CpG motifs induce low levels of TNF-alpha in human B lymphocytes: possible adjuvants for Th1 responses

Oligodeoxynucleotides containing CpG motifs (CpG-ODN) represent potential adjuvants for specific immunotherapy of type I allergies because they foster Th1-like immune responses. However, previous work has shown that CpG-ODN induce systemically active levels of TNF-alpha in murine macrophages. The goal of the present study was to evaluate the release of TNF-alpha in human cells by a CpG-ODN proven to induce Th1 immune responses in cells from atopic individuals and in mice. CpG-ODN induced TNF-alpha in cells from atopic and healthy individuals. However, the amounts were low, as determined by comparison with commonly used Ags. Intracellular cytokine staining of PBMC revealed that CpG-ODN-induced TNF-alpha derived exclusively from B lymphocytes. TNF-alpha contributed to the CpG-ODN-augmented proliferation and Ig synthesis in PBMC, but was not involved in IFN-gamma synthesis. In conclusion, our findings indicate that certain CpG-ODN induce low amounts of TNF-alpha in human B lymphocytes and may therefore be used to modulate Th2-biased immune responses in allergic patients.

IgA cross-reactivity between a nuclear autoantigen and wheat proteins suggests molecular mimicry as a possible pathomechanism in celiac disease

Celiac disease patients display IgA antibody reactivity to wheat as well as to human proteins. We used serum IgA from celiac patients and, for control purposes, from patients with Crohn's disease, ulcerative colitis and from healthy individuals to identify celiac disease-specific IgA autoantigens in nitrocellulose-blotted extracts from various human cell types (epithelial, endothelial, intestinal cells, fibroblasts). The pattern, recognition intensity and time course of IgA autoreactivity was monitored using serial serum samples obtained from celiac children before and under gluten-free diet. By immunoblot inhibition and subcellular (cytosolic, nuclear) cell fractionation we identified a 55 kDa nuclear autoantigen expressed in intestinal, endothelial cells and in fibroblasts which was recognized by IgA antibodies of approximately half of the celiac disease patients and cross-reacted with wheat proteins. IgA reactivity to the 55 kDa autoantigen disappeared during gluten-free diet and was inhibited after pre-absorption of sera with wheat proteins but not with tissue transglutaminase, previously reported as the unique celiac disease-specific autoantigen. In conclusion, we defined a novel 55 kDa celiac disease-specific nuclear IgA autoantigen which shares epitopes with wheat proteins and which is different from tissue transglutaminase and calreticulin. Although the newly defined autoantigen was recognized much less frequently than tissue transglutaminase, our data suggest molecular mimicry between wheat and human proteins as a possible pathomechanism for the induction and/or maintenance of mucosal tissue damage in celiac disease.

Recombinant allergen molecules: tools to study effector cell activation

The IgE antibody-mediated activation of allergic effector cells is the key pathomechanism underlying the immediate symptoms of Type I allergy, a genetically determined hypersensitivity disease affecting 25% of the population. In recent years important environmental allergens and their epitopes have become available as structurally defined recombinant molecules. In addition, corresponding human monoclonal IgE and IgG antibodies have been isolated. This review summarizes data obtained regarding the three-dimensional structure of allergens, their IgE epitopes and the recognition of allergens by IgE and IgG antibodies. In particular, we discuss results of recent in vitro and in vivo studies with defined allergen molecules, their epitopes and the corresponding antibodies which support the hypothesis that the density and geometrical arrangement of IgE epitopes on a particular allergen molecule may profoundly affect effector cell activation. If the structural requirements for effector cell activation can be delineated, it may be envisaged that, based on this knowledge, allergens can be converted into hypoallergenic immunogens by reorientation of IgE epitopes. Such allergen derivatives may be used for allergen-specific immunotherapy with reduced risk of inducing anaphylactic side effects.

A Highly Allergenic Fragment of the Major Timothy Grass Pollen Allergen, Phl p 5, Defined by a Human Monoclonal IgE Antibody

We report the characterization of a domain of the major timothy grass pollen allergen, Phl p 5A, which contains the binding site for a human monoclonal IgE antibody. The human monoclonal IgE antibody fragment (Fab) was obtained from an IgE combinatorial library constructed from lymphocytes of a grass pollen-allergic patient. An 11.2-kD N-terminal fragment representing approximately one third of the complete Phl p 5A allergen could be identified to contain the binding site for the IgE Fab. The rPhl p 5A fragment revealed an extremely high allergenic activity in skin test experiments which in some cases equaled that of the complete Phl p 5A allergen. The rPhl p 5A domain thus represents an allergen fragment containing several IgE epitopes in a configuration optimal for efficient effector cell activation. We suggest the rPhl p 5A fragment and the corresponding IgE Fab as paradigmatic tools to explore the structural requirements for highly efficient effector cell activation.

Mucosal tolerance induction with hypoallergenic molecules in a murine model of allergic asthma

Type I allergy, frequently elicited by airborne allergens, has constantly increased within recent years. Birch pollen and its major allergen Bet v 1 represent a major source of type I allergens. By genetic engineering hypoallergenic Bet v 1 fragments were produced, which lost the IgE binding capacity but retained the T cell epitopes. We have established a murine model of aerosol sensitization to birch pollen and its major allergen Bet v 1, leading to type I allergic immune responses and airway hyperresponsiveness. In the present study we demonstrate that mucosal administration of recombinant Bet v 1 prior to sensitization led to allergen-specific suppression of B and T cell responses in vivo and in vitro, reduction of eosinophilic infiltration in the lungs and inhibition of airway hyperresponsiveness. Intranasal pretreatment with the nonanaphylactic fragments of Bet v 1 prevented allergic immune responses and airway inflammation to the same degree as the pretreatment with the complete molecule. We conclude from our studies that mucosal tolerance induction with hypoallergenic molecules could provide a safe and convenient treatment strategy against type I allergies.

T cell epitope-containing hypoallergenic recombinant fragments of the major birch pollen allergen, Bet v 1, induce blocking antibodies

Allergen-specific immunotherapy represents one of the few curative approaches toward type I allergy. Up to 25% of allergic patients are sensitized against the major birch pollen allergen, Bet v 1. By genetic engineering we produced two recombinant (r) Bet v 1 fragments comprising aa 1-74 and aa 75-160 of Bet v 1, which, due to a loss of their native-like fold, failed to bind IgE Abs and had reduced allergenic activity. Here we show that both fragments covering the full Bet v 1 sequence induced human lymphoproliferative responses similar to rBet v 1 wild type. The C-terminal rBet v 1 fragment induced higher lymphoproliferative responses than the N-terminal fragment and represented a Th1-stimulating segment with high IFN-gamma production, whereas the N-terminal fragment induced higher IL-4, IL-5, and IL-13 secretion. Immunization of mice and rabbits with rBet v 1 fragments induced IgG Abs, which cross-reacted with complete Bet v 1 and Bet v 1-related plant allergens and strongly inhibited the IgE binding of allergic patients to these allergens. Thus, our results demonstrate that hypoallergenic T cell epitope-containing rBet v 1 fragments, despite lacking IgE epitopes, can induce Abs in vivo that prevent the IgE binding of allergic patients to the wild-type allergen. The overall demonstration of the immunogenic features of the hypoallergenic rBet v 1 fragments will now enable clinical studies for safer and more efficient specific immunotherapy.

A human monoclonal IgE antibody defines a highly allergenic fragment of the major timothy grass pollen allergen, Phl p 5: molecular, immunological, and structural characterization of the epitope-containing domain

Almost 90% of grass pollen-allergic patients are sensitized against group 5 grass pollen allergens. We isolated a monoclonal human IgE Fab out of a combinatorial library prepared from lymphocytes of a grass pollen-allergic patient and studied its interaction with group 5 allergens. The IgE Fab cross-reacted with group 5A isoallergens from several grass and corn species. By allergen gene fragmentation we mapped the binding site of the IgE Fab to a 11.2-kDa N-terminal fragment of the major timothy grass pollen allergen Phl p 5A. The IgE Fab-defined Phl p 5A fragment was expressed in Escherichia coli and purified to homogeneity. Circular dichroism analysis revealed that the rPhl p 5A domain, as well as complete rPhl p 5A, assumed a folded conformation consisting predominantly of an alpha helical secondary structure, and exhibited a remarkable refolding capacity. It reacted with serum IgE from 76% of grass pollen-allergic patients and revealed an extremely high allergenic activity in basophil histamine release as well as skin test experiments. Thus, the rPhl p 5A domain represents an important allergen domain containing several IgE epitopes in a configuration optimal for efficient effector cell activation. We suggest the rPhl p 5A fragment and the corresponding IgE Fab as paradigmatic tools to explore the structural requirements for highly efficient effector cell activation and, perhaps later, for the development of generally applicable allergen-specific therapy strategies.

Immunoglobulin E antibodies of atopic individuals exhibit a broad usage of VH-gene families

The term 'atopy' describes the genetically determined tendency to mount immunoglobulin E (IgE) antibody responses against per se harmless antigens (allergens). In this study we investigated the usage of VH families in the formation of IgE antibodies in 10 patients suffering from mucosal and/or skin manifestations of atopy. IgE antibody reactivities to exogenous allergen sources as well as to autoallergens were determined and, by immunoabsorption, it was demonstrated that allergen-specific IgE accounted for most of the total serum IgE levels in these patients. Using primers with specificity for the VH1-6 gene families and a primer specific for the first constant region of human IgE, cDNAs coding for IgE heavy chain fragments were amplified using the reverse transcription-polymerase chain reaction (RT-PCR) from peripheral blood lymphocytes of the 10 atopic individuals. Hybridization of the heavy chain-encoding cDNAs with an IgE-specific internal oligonucleotide probe revealed a broad usage of all VH-gene families in the atopic individuals. The spectrum of VH families used in a given atopic individual was neither associated with the type or severity of clinical symptoms nor with the number of allergens recognized. The fact that allergen-specific IgE antibodies in atopic individuals originate from a broad variety of B cells thus reflects the activation of multiple B-cell clones during allergen sensitization. This finding should be borne in mind if therapeutic strategies for Type I allergy are considered that aim at a clonal elimination of allergen-specific B cells.

Reducing relapse in depressed outpatients with atypical features: a pilot study

BACKGROUND

Patients with major depressive disorder (MDD) and atypical features have reactive mood plus at least two symptoms: hypersomnia, hyperphagia, leaden paralysis or a lifetime sensitivity to rejection. These patients respond to cognitive therapy (CT) or phenelzine (PHZ) significantly more than pill placebo (PBO). The purpose of this report is to motivate research on tolerable continuation phase treatment designed to reduce the significant risk of relapse and recurrence which depressed patients with atypical features face.

METHODS

Outpatients with DSM-III-R MDD and atypical features who responded to acute-phase CT, clinical management plus PHZ or PBO (n = 31) were randomized to continue or discontinue treatment for 8 months and participate in 16 months or treatment-free follow-up.

RESULTS

A log-rank test showed that the relapse and recurrence-free survival over the 24 months after the acute phase was significantly greater for the responders who continued treatment than for those who discontinued treatment. Kaplan-Meier estimates of relapse and recurrence were significantly higher for patients whose treatment was discontinued than for those whose treatment continued (83 vs 49% based on unblinded ratings of the Research Diagnostic Criteria for MDD or of self/other referral for treatment of depressive symptoms).

CONCLUSIONS

We note several important limitations of the design and analysis of these pilot data. We hypothesize that not only pharmacotherapy, but also CT used as a continuation phase treatment may reduce relapse in this population. This hypothesis warrants rigorous evaluation in samples of outpatients with MDD and atypical features that are large enough to allow comparative tests.

Comparison of genetically engineered hypoallergenic rBet v 1 derivatives with rBet v 1 wild-type by skin prick and intradermal testing: results obtained in a French population

BACKGROUND

Bet v 1, the major allergen in birch pollen, is recognized by more than 90% of patients allergic to birch in northern and central Europe. Immunotherapy is commonly performed with birch pollen extracts. Recently, hypoallergenic derivatives of Bet v 1 (rBet v 1 fragments, rBet v 1 dimer and trimer) were constructed and purified.

OBJECTIVE

Our aim was to compare the allergenic activity of wild-type rBet v 1 with recombinant Bet v 1 derivatives (rBet v 1 fragments, dimer and trimer) with potentially reduced anaphylactic activity by skin testing in a French population.

METHODS

Among the 36 birch pollen allergic patients included in the study, 29 were tested by skin prick testing and 30 by intradermal injections with purified monosubstances: rBet v 1 fragments (F1: aa1-74 and F2: aa75-160), Bet v 1 dimer and trimer. Intradermal tests were performed by the end-point intradermal titration method. Eight of the intradermally-tested patients were previously hyposensitized. Tests were performed over a period of 6 months (before, during and after birch pollen season); Bet v 1-specific IgE and IgG4 subclass responses were measured by immunoblotting and ELISA.

RESULTS

All patients showed lower reactivity with the modified rBet v 1 allergens, both in skin prick and intradermal tests. In 25 and 23 out of 29 patients the lowest concentration of fragment 1 and 2, respectively, resulting in a positive prick test was 100-fold higher than the lowest concentration of monomer resulting in a positive prick test. For dimer it was 100-fold or more in 25 out of 29 patients, and for trimer it was 100-fold or superior in 26 out of 29 patients. By intradermal testing, the end-point concentration was 160-fold higher for trimer than for monomer in 24 patients and 40-fold higher in five patients. For the two fragments the end-point concentration was 160-fold higher in 20 out of 22 patients.

CONCLUSION

Genetically modified hypoallergenic derivatives of the major birch pollen allergen, Bet v 1 showed reduced capacity to induce immediate type skin reactions. They may represent candidate molecules for immunotherapy of birch pollen allergy with reduced risk of anaphylactic side-effects.

Mutual boosting effects of sensitization with timothy grass pollen and latex glove extract on IgE antibody responses in a mouse model

Type I allergy to natural rubber latex can be an important health problem for latex-exposed individuals (e.g., health care workers, spina bifida children). Also beyond these risk groups, a high sensitization rate of varying and partly unknown clinical relevance has been reported. Atopy represents a risk factor for latex allergy and recent studies indicate that patients suffering from pollen allergies may have pollen allergen-specific IgE antibodies which cross-react with latex allergens. In order to investigate whether sensitization to pollen allergens can have priming effects on the production of IgE antibodies against latex in vivo, a mouse model was established. Groups of 10 BALB/C mice were immunized with Al(OH)3-adsorbed pollen extracts from timothy grass, ragweed, mugwort, or birch. For control purposes, one additional group received adjuvant only and another group was not immunized. Half of the mice of each group were subsequently immunized with Al(OH)3-adsorbed latex glove extract, the other half with adjuvant only. Pollen and latex-specific IgE- and IgG1-antibody responses were analyzed by enzyme-linked immunosorbent assay and statistically evaluated by analysis of variance. Antibody responses to cross-reactive antigens were investigated by immunoblotting. We found significantly increased IgE reactivities to latex after pollen sensitization and vice versa. Moreover, mice immunized with timothy grass pollen extract alone - without subsequent latex immunization - displayed IgE reactivity to latex. Cross-reactive antibodies were directed against pollen antigens of approximately 60 kDa molecular weight. Our results thus demonstrate a mutual boosting effect of pollen and latex sensitization in vivo which may be also operative in polysensitized plant allergic patients.

Dissociation of allergen-specific IgE and IgA responses in sera and tears of pollen-allergic patients: a study performed with purified recombinant pollen allergens

BACKGROUND

Trees and grass pollen allergens represent potent elicitors of allergic rhinoconjunctivitis and asthma. Little is known regarding the presence of allergen-specific IgA antibodies in sera and tears and their association with IgE responses in patients with allergic conjunctivitis.

OBJECTIVE

The purpose of this study was to compare the specificities of IgE and IgA antibodies in sera and tears of pollen-allergic patients with conjunctivitis by using purified recombinant pollen allergens.

METHODS

Sera and tears collected from 23 pollen-allergic and from 23 nonatopic individuals were analyzed for IgE and IgA reactivity to nitrocellulose-blotted birch and timothy grass pollen extracts. In addition, we determined the specificities of IgE, IgG(1-4), and IgA antibodies with use of a panel of purified recombinant pollen allergens (timothy grass: rPhl p 1, rPhl p 2, rPhl p 5; birch: rBet v 1, rBet v 2) in serum and tear samples by immunoblotting and ELISA. Statistical analyses of data were performed by t test and Mann Whitney U test.

RESULTS

Serum and tears of many of the pollen-allergic individuals with conjunctivitis exhibited specificity for the very same pollen allergens. No allergen-specific IgE antibodies were detected in tears of nonatopic individuals. IgA antibodies in sera and tears of patients with allergic conjunctivitis were mainly directed against nonallergenic moieties and showed specificities that were significantly different from those of IgE antibodies.

CONCLUSION

The dissociation of IgE and IgA responses and the lack of allergen-specific IgA antibodies in mucosal secretions (eg, tears) may contribute to allergic manifestations in target organs of atopy. Induction of allergen-specific IgA antibodies may hence be considered as a promising strategy for the treatment of mucosal forms of atopy.

Prevention of latex allergy by selection of low-allergen gloves

BACKGROUND

In recent years the prevalence of type I allergy to latex has continuously increased, in particular among healthcare workers, to about 10%. While most forms of type I allergy caused by other environmental allergens can be treated by pharmacotherapy or specific immunotherapy, minimizing exposure to latex proteins may represent an effective preventive measure for latex allergy.

OBJECTIVE

To investigate whether it is possible to select by in vitro and in vivo testing low-allergen latex gloves for prevention of latex allergy.

METHODS

We obtained separate extracts by standard aqueous extraction from the inner and outer surfaces of 15 different commonly used (10 examination, five surgical) glove brands. The extracts were analysed by quantitative (bicinchoninic protein assay, immunoglobulin [Ig] E-ELISA, ELISA competition) and qualitative (SDS-PAGE, silver staining, IgE immunoblotting) methods for their protein and allergen contents. In addition, the glove extracts were analysed for their capacity to induce basophil histamine release and immediate skin reactions.

RESULTS

Extracts from different glove brands contained cross-reactive IgE epitopes. However, IgE binding studies, basophil histamine release and skin testing showed that different glove brands and their inner and outer surfaces contained widely varying protein and allergen contents. While the determination of total protein contents was not sufficient to identify low-allergen gloves, IgE measurements, basophil histamine release and skin testing were in good agreement and allowed to select low-allergen products.

CONCLUSION

We suggest the use of low-allergen latex products identified by IgE binding, basophil histamine release assays and skin testing as a feasible preventive measure for latex allergy.

[Hydroxyethyl starch accumulation in the skin with special reference to hydroxyethyl starch-associated pruritus]

BACKGROUND AND OBJECTIVE

Hydroxyethyl starch (HES) is a colloidal infusion fluid that has for a long time been used in emergency situations and to improve impaired blood perfusion. In the last few years there have been numerous reports about treatment resistant pruritus, often persisting for months, after HES infusion. We investigated the intracellular uptake of HES in the skin, special attention being focused on associated pruritus.

PATIENTS AND METHODS

Skin biopsies were obtained from 120 patients (120 men, 35 women) and examined immunohistochemically and for their ultrastructure. Three patients had received various HES preparations, while 22 had been given dextran. Five patients who had received no infusions served as controls.

RESULTS

All patients given HES had lysosomal deposits in the histiocytes, some of them also in cutaneous epithelium and endothelium. The extent of lysosomal storage correlated with the amount of infused HES and the interval between biopsy and last HES infusion. Consecutive biopsies in some cases demonstrated a definite decrease over the years of HES deposits in the vacuoles. This suggests that HES is regularly metabolized in the skin. Pruritus after high cumulative doses of HES was closely correlated with HES deposition in cutaneous nerves.

CONCLUSIONS

These results emphasize the need for starch derivatives that can be better metabolized and for better adapted infusion schedules to reduce the high incidence of pruritus.

Molecular characterization of human IgG monoclonal antibodies specific for the major birch pollen allergen Bet v 1. Anti-allergen IgG can enhance the anaphylactic reaction

We report the molecular characterization of five human monoclonal antibodies, BAB1-5 (BAB1: IgG(1); BAB4: IgG(2); BAB2, 3, 5: IgG(4)), with specificity for the major birch pollen allergen, Bet v 1. BAB1-5 were obtained after immunotherapy and contained a high degree of somatic mutations indicative of an antigen-driven affinity maturation process. While BAB1 inhibited the binding of patients IgE to Bet v 1, BAB2 increased IgE recognition of Bet v 1, and, even as Escherichia coli-expressed Fab, augmented Bet v 1-induced immediate type skin reactions. The demonstration that IgG antibodies can enhance allergen-induced allergic reactions is likely to explain the unpredictability of specific immunotherapy.

Quantitative IgE inhibition experiments with purified recombinant allergens indicate pollen-derived allergens as the sensitizing agents responsible for many forms of plant food allergy

BACKGROUND

Type I allergic symptoms in the oropharyngeal mucosa upon contact with plant-derived food in patients with pollen allergies have been termed oral allergy syndrome (OAS). IgE cross-reactivity between pollen and food allergens represents the molecular basis for this phenomenon. The sensitizing allergen source (pollen or plant food) in OAS is a controversial issue.

OBJECTIVE

We sought to determine the primary sensitizing molecules in patients with OAS.

METHODS

We used recombinant birch pollen (rBet v 1 and rBet v 2) and plant food allergens (apple, rMal d 1; celery, rApi g 1; and carrot, rDau c 1), as well as natural pollen (birch and timothy grass) and plant food (apple, peach, kiwi, hazelnut, celery, and carrot) allergens, to identify cross-reactive allergens by using qualitative immunoblot inhibitions. In addition, we determined the percentage of plant food-specific IgE that can be preadsorbed with recombinant and natural pollen allergens by quantitative RAST inhibitions by using sera from 71 patients with OAS.

RESULTS

Preincubation of sera with recombinant and natural pollen allergens led to an almost complete inhibition of IgE binding to plant food allergens in Western blots, as well as in RAST inhibition experiments. In contrast, recombinant plant food allergens poorly inhibited IgE binding to Bet v 1.

CONCLUSION

Most IgE epitopes in plant food recognized by patients with OAS are resembled by pollen allergens. Thus pollen allergens may be responsible for the elicitation and maintenance of OAS.

Engineering, purification and applications of His-tagged recombinant antibody fragments with specificity for the major birch pollen allergen, bet v1

Type I allergy, an immunodisorder affecting almost 20% of the population worldwide, is based on the production of IgE antibodies against per se harmless allergens. We report the expression of hexahistidine-tagged antibody fragments (Fabs) with specificity for Bet v1, the major birch pollen allergen, in Escherichia coli. The cDNA coding for the heavy chain fragment of a mouse monoclonal anti-Bet v1 antibody, Bip 1, was engineered by PCR to contain a hexahistidine-encoding 3' end. The modified Bip1 heavy chain cDNA was co-expressed in E. coli XL-1 Blue with the Bip 1 light chain cDNA using the combinatorial plasmid pComb3H. His-tagged recombinant (r) Bip 1 Fabs were isolated by nickel affinity chromatography and rBip 1 Fabs without His-tag were purified via affinity to rBet v1. rBip 1 Fabs with and without His-tag bound specifically to rBet v1 and, like Bet v1 -specific human serum IgE and rabbit-anti rBet v1 antibodies, cross-reacted with Bet v1-related allergens in other plant-species (alder, oak, hazelnut). We demonstrate the usefulness of His-tagged rBip 1 Fabs (1) for the identification of pollen samples containing Bet v 1 by particle blotting, (2) forthe detection of Bet v1-specific IgE antibodies in human serum samples by sandwich ELISA and (3) for the quantification of Bet v1 in solution. Based on these examples we suggest to use rBip 1 Fabs for the detection of Bet v1 and Bet v1-related allergens in natural allergen sources for allergy prevention, as well as for the standardization of natural allergen extracts produced for diagnosis and immunotherapy of birch pollen allergy.

Immunogold electron microscopic localization of the cross-reactive two-EF-hand calcium-binding birch pollen allergen Bet v 4 in dry and rehydrated birch pollen

BACKGROUND

Recently, a novel family of low-molecular-weight (8-9 kD), two-EF-hand calcium-binding proteins has been described as allergens in plant pollens. Approximately 10% of pollen-allergic patients have IgE antibodies which cross-react with the two-EF-hand allergens in tree, grass and weed pollens. The aim of the present study was to localize Bet v 4, the two-EF-hand allergen from birch, in mature, dry pollen and to study the release of this allergen after hydration of the pollen by immunogold electron microscopy.

METHODS

Using completely anhydrous fixation techniques in combination with immunogold electron microscopy, we localized Bet v 4 and, for control purposes, the major birch pollen allergen Bet v 1, in dry birch pollen as well as in pollen grains after different periods of hydration. Parallel with these morphological studies, we monitored the release of Bet v 4 and Bet v 1 into aqueous supernatants of hydrated birch pollen grains by immunoblotting.

RESULTS

Bet v 4 was found in the electron-dense cytosol, in particular between the vesicles and cisternae of the endoplasmic reticulum, inside mitochondria and in the vegetative as well as in the generative nucleus. Bet v 1 was localized in similar cellular compartments except for the mitochondria. After 30 s to 1 min of hydration, Bet v 4 migrated into the pollen exine and into the aqueous supernatants. Bet v 1 also moved out of the pollen grain, though not as quickly as Bet v 4.

CONCLUSION

Bet v 4 represents an intracellular pollen protein which, following hydration of pollen grains, rapidly migrates to the pollen surface (exine) and is washed out. This behavior explains how Bet v 4, being primarily an intracellular pollen protein, becomes available to sensitize patients.

Molecular, immunological, and structural characterization of Phl p 6, a major allergen and P-particle-associated protein from Timothy grass (Phleum pratense) pollen

Due to the wide distribution and heavy pollen production of grasses, approximately 50% of allergic patients are sensitized against grass pollen allergens. cDNAs coding for two isoforms and four fragments of a major timothy grass (Phleum pratense) pollen allergen, Phl p 6, were isolated by IgE immunoscreening from a pollen expression cDNA library. Recombinant Phl p 6 (rPhl p 6), an acidic protein of 11.8 kDa, was purified to homogeneity as assessed by mass spectrometry and exhibited almost exclusive alpha-helical secondary structure as determined by circular dichroism spectroscopy. Phl p 6 reacted with serum IgE from 75% of grass pollen-allergic patients (n = 171). IgE binding experiments with rPhl p 6 fragments indicated that the N terminus of the allergen is required for IgE recognition. Purified rPhl p 6 elicited dose-dependent basophil histamine release and immediate type skin reactions in patients allergic to grass pollen. A rabbit antiserum raised against purified rPhl p 6 identified it as a pollen-specific protein that, by immunogold electron microscopy, was localized on the polysaccharide-containing wall-precursor bodies (P-particles). The association of Phl p 6 with P-particles may facilitate its intrusion into the deeper airways and thus be responsible for the high prevalence of IgE recognition of Phl p 6. Recombinant native-like Phl p 6 can be used for in vitro as well as in vivo diagnoses of grass pollen allergy, whereas N-terminal deletion mutants with reduced IgE binding capacity may represent candidates for immunotherapy of grass pollen allergy with a low risk of anaphylactic side effects.