Identification of Bet v 1‐related allergens in fig and other Moraceae fruits

Background Allergy to fig fruit (Ficus carica) has been described in patients allergic to Ficus benjamina or rubber latex but may occur also in pollen‐allergic patients. Objective To study the potential cross‐reactivity between fig and taxonomically related fruits with the major birch pollen allergen Bet v 1. Methods One hundred and eighty‐eight patients with or without birch pollen allergy were prick‐to‐prick tested with fig (F. carica), mulberry (Morus alba), jackfruit (Artocarpus heterophyllus; all family Moraceae) and other pollen‐associated foods. Moraceae fruit extracts were separated by SDS‐PAGE and tested with patient sera and polyclonal antisera against Mal d 1. Western blot inhibition was performed with Moraceae fruit extracts, birch pollen and recombinant Bet v 1. Putative Bet v 1 homologs in Moraceae fruits were analysed by liquid chromatography‐ion trap mass spectrometry. Results Among 85 patients with isolated birch pollen allergy, 78% had a positive skin test to fresh fig, 10% to dried fig, 91% to mulberry, 91% to jackfruit, 77% to Rosaceae fruits and 83% to hazelnut. Sixty‐six per cent of birch pollen‐allergic patients positive for fig, reported symptoms after consumption of fresh figs, whereas dried figs were mostly well tolerated. In 60 patients with isolated Ficus benjamina sensitization, the reactivity rates to the same foods were 83‐40‐0‐0‐0‐0%. None of 32 mugwort pollen‐allergic patients reacted to Moraceae fruits. Rabbit anti‐Mal d 1 and patient sera reacted to a 17 kDa band in all Moraceae extracts. IgE binding to these proteins was completely inhibited by birch pollen and rBet v 1. Mass spectrometry identified several peptides from the 17 kDa fig, mulberry and jackfruit allergen with respectively 60%, 56% and 76% homology to Bet v 1. Conclusion Fig and other Moraceae fruits contain allergens homologous to Bet v 1 and represent clinically relevant birch pollen‐associated foods. Cite this as: W. Hemmer, M. Focke, G. Marzban, I. Swoboda, R. Jarisch and M. Laimer, Clinical & Experimental Allergy, 2010 (40) 679–687.     

Isolation of a high‐affinity Bet v 1‐specific IgG‐derived ScFv from a subject vaccinated with hypoallergenic Bet v 1 fragments

Background

Recombinant hypoallergenic allergen derivatives have been used in clinical immunotherapy studies, and clinical efficacy seems to be related to the induction of blocking IgG antibodies recognizing the wild‐type allergens. However, so far no treatment‐induced IgG antibodies have been characterized.

Objective

To clone, express, and characterize IgG antibodies induced by vaccination with two hypoallergenic recombinant fragments of the major birch pollen allergen, Bet v 1 in a nonallergic subject.

Methods

A phage‐displayed combinatorial single‐chain fragment (ScFv) library was constructed from blood of the immunized subject and screened for Bet v 1‐reactive antibody fragments. ScFvs were tested for specificity and cross‐reactivity to native Bet v 1 and related pollen and food allergens, and epitope mapping was performed. Germline ancestor genes of the antibody were analyzed with the ImMunoGeneTics (IMGT) database. The affinity to Bet v 1 and cross‐reactive allergens was determined by surface plasmon resonance measurements. The ability to inhibit patients’ IgE binding to ELISA plate‐bound allergens and allergen‐induced basophil activation was assessed.

Results

A combinatorial ScFv library was obtained from the vaccinated donor after three injections with the Bet v 1 fragments. Despite being almost in germline configuration, ScFv (clone H3‐1) reacted with high affinity to native Bet v 1 and homologous allergens, inhibited allergic patients’ polyclonal IgE binding to Bet v 1, and partially suppressed allergen‐induced basophil activation.

Conclusion

Immunization with unfolded hypoallergenic allergen derivatives induces high‐affinity antibodies even in nonallergic subjects which recognize the folded wild‐type allergens and inhibit polyclonal IgE binding of allergic patients.     

Antibody profiles and self-reported symptoms to pollen-related food allergens in grass pollen-allergic patients from northern Europe

BACKGROUND: Most studies on pollen-related food allergy have so far focused on the association of birch/weed pollen allergens and plant food allergy. The aim of this study was to elucidate the allergen spectrum among a group of grass pollen-allergic patients from northern Europe and to relate the results to clinical histories of pollen-related food allergy. METHODS: Fifty-eight grass pollen-allergic patients answered a questionnaire regarding allergy to foods. Blood samples were taken to test IgE-reactivity to a large panel of pollen allergens and pollen- and nonpollen-related food allergens using crude allergen extracts and recombinant and native allergens. RESULTS: Three different groups of grass pollen-allergic patients were identified according to their IgE antibody profile: a grass pollen group only (19%), a grass and tree pollen group (29%) and a grass, tree and compositae (pan-) pollen group (48%). No sensitization to Bet v 1 as well as almost no IgE to plant food was observed in the grass pollen group. In contrast, nearly all patients in the two tree-related groups had IgE to Bet v 1, which reflected the high frequency of adverse reactions to typical birch-related food in these groups. Only four patients belonging to the pan-pollen group displayed IgE to profilin Phl p 12/Bet v 2. Patients in the pan-pollen group reported significantly more symptoms to food allergens compared with patients in the two other groups. The most frequently reported symptom was the oral allergy syndrome. CONCLUSIONS: Sensitization to grass pollen alone is rare among grass pollen-allergic patients from northern Europe. The majority of patients are in addition sensitized to birch (Bet v 1), which seems to be closely related to their pollen-derived food allergy. The study highlights the advantage of using well-defined allergen molecules for the diagnosis of cross-reactivity between pollen and food allergens.     

How far can we simplify in vitro diagnostics for Fagales tree pollen allergy? A study with three whole pollen extracts and purified natural and recombinant allergens

BACKGROUND: Current diagnostic tests for Fagales tree pollen allergy are often composed of mixtures of pollen of birch, alder and hazel. Their complex composition hampers accurate standardization. OBJECTIVE: The aim of this study was to investigate whether mixtures of tree 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 = 1725) were selected on ground of a general suspicion for inhalant allergy, and tested in a RAST for birch, alder and hazel pollen. Sera with > 0.5 RU/mL for any of the three species were tested in a RAST for natural Bet v 1 and Bet v 2 as well as for recombinant versions of both allergens. RESULTS: Specific IgE antibodies (> 0.3 RU/mL) against birch, alder and hazel were found in 242, 298 and 292 sera, respectively. All sera with a positive RAST for alder and/or hazel and a negative RAST for birch were low-responder sera on alder and hazel, only five sera having a RAST value > 1.0 (all < 2.0). For all sera with a RAST > 0.5 RU/mL (n = 250), the mean of individual ratio's alder/birch and hazel/birch was 1.02 and 0.54, respectively. Of 223 of these sera, 63.2% had specific IgE against natural Bet v 1 and 63.7% against natural Bet v 2. When responses to both allergens were combined 93.7% were positive. The mean ratios Bet v 1 + 2/extract were 1.00, 1.04 and 2. 11 in case of birch, alder and hazel, respectively. For 211 sera the same analysis was performed with recombinant Bet v 1 and Bet v 2. Only six sera with Bet v 1-specific IgE (all < 0.5 RU/mL) were negative (< 0.3 RU/mL) on recombinant Bet v 1. For Bet v 2, 77/132 sera with specific IgE to the natural allergen did not react to the recombinant version. Twelve false-negatives had RAST values > 1.0 RU/mL. The mean of the individual recombinant/natural ratios was 0. 98 for Bet v 1 and 0.38 for Bet v 2 (P < 0.001). The mean ratio rBet v 1 + 2/birch was 0.75 with 17.5% false-negatives on the combination of recombinant allergens. CONCLUSION: Reliable in vitro diagnosis is possible with a single tree pollen extract (birch or alder). The same is true for purified natural Bet v 1 and Bet v 2. A combination of recombinant molecules is slightly less efficient.     

Different IgE reactivity profiles in birch pollen-sensitive patients from six European populations revealed by recombinant allergens: an imprint of local sensitization

BACKGROUND: Sensitivity to birch pollen allergens is a common feature among European patients with seasonal pollen allergy. In this in vitro study, we examined the specific serum IgE binding profiles to individual birch pollen allergens in birch-sensitive patients from six European populations. METHODS: The study included 242 patients from Finland, Sweden, Austria, France, Switzerland and Italy. All suffered from seasonal rhinoconjunctivitis and/or asthma. Their sera were analyzed for specific IgE reactivity to individual birch pollen allergens (recombinant Bet v 1, Bet v 2 and Bet v 4) and natural birch pollen extract using Pharmacia CAP System and immunoblotting. RESULTS: Almost all Finnish, Swedish and Austrian sera contained IgE specific for Bet v 1 (>or=98%). Bet v 1-specific IgE antibodies were found in 90% of the French sera, and in 65 and 62% of the sera from Switzerland and Italy, respectively. Few Finnish (2%) and Swedish (12%) patients had IgE to Bet v 2, while Bet v 2 reactivity was more common in the other populations (20-43%). Reactivity to Bet v 4 was rare in all populations (5-11%) except for the Italian patients, in whom 3 of 11 sera were positive (27%). The immunoblot results supported the specific IgE profiles obtained with Pharmacia CAP System showing a broader IgE reactivity profile in patients from central and southern Europe as compared to northern Europe. CONCLUSION: Component-resolved allergy diagnosis with recombinant allergens reveals that the IgE reactivity profiles to individual birch pollen allergens vary between European populations. This observation may be explained by sensitization to different allergen sources and will have an impact on allergen-specific prevention and therapy strategies.     

Detection of specific IgE antibodies in the sera of patients allergic to birch pollen using recombinant allergens Bet v 1, Bet v 2, Bet v 4: evaluation of different IgE reactivity profiles

BACKGROUND: Birch pollen is a significant cause of immediate hypersensitivity among susceptible subjects in temperate climates, affecting 5-54% of the population in western Europe. We examined the specific serum IgE antibodies towards recombinant allergens Bet v 1, Bet v 2 and Bet v 4 in birch-sensitive patients from the province of Cuneo, north-west Italy. METHODS: Sera were obtained from 372 patients with symptomatic birch pollen-induced allergic rhinitis and/or asthma. A subgroup of these patients suffered from oral allergy syndrome after eating apple. Their sera were evaluated for specific IgE against natural birch pollen and apple extract, as well as Bet v 1, Bet v 2 and Bet v 4 using Pharmacia CAP system (Pharmacia, Uppsala, Sweden). RESULTS: Of 372 patients 215 (57.80%) had serum-specific IgE towards Bet v 1. A total of 166 sera (44.62%) contained serum-specific IgE to Bet v 2, while Bet v 4 IgE reactivity was documented in 35 subjects (9.41%). Moreover, 146 (39.25%) patients were monosensitized to Bet v 1; 96 (25.81%) patients were monosensitized to Bet v 2; only four sera (1.08%) contained specific IgE towards Bet v 4. Thirty-nine sera (11.02%) did not contain specific IgE to these individual birch pollen allergens. Of course, all 372 sera (100%) had specific IgE against natural birch pollen extract, of which 162 (43.55%) contained specific IgE to apple extract (75.35% of Bet v 1 positive sera). CONCLUSION: In this study we observed that three birch pollen recombinant allergens alone, could sufficiently identify 90% of birch pollen-sensitive patients. Therefore, for a more precise IgE profile of patients allergic to birch, further purified birch pollen allergens (i.e. Bet v 6, Bet v 7, Bet v 8) will be required.     

Characterization of allergens in kiwi fruit and detection of cross‐reactivities with allergens of birch pollen and related fruit allergens

The sera of 29 patients who suffered from pollen‐related food hypersensitivities and complained of allergic reactions to kiwi fruit and other tropical fruits were tested for specific IgE antibodies against kiwi fruit, apple, carrot, celery and birch pollen using an enzyme allergosorbent test (EAST). In 20 sera, specific IgE antibodies were detected against all five extracts. Sodium dodecyl sulphate polyacrylamide gel electrophoresis/ immunoblot of kiwi fruit extract revealed two major allergens with molecular weights of approximately 43 and 67 kDa. In EAST inhibition assays, cross‐reactivities between kiwi fruit, apple, birch pollen and, to a lesser degree, carrot and celery were demonstrated. The cross‐reactivities seen between kiwi fruit, birch pollen and apple were not caused by the major allergen of birch pollen (Bet v 1). Allergens with molecular weights of approximately 68 kDa in birch pollen and 67 kDa in apple cross‐reacted with the allergens of kiwi fruit, as demonstrated by immunoblotinhibition. Profilins, which are known plant pan‐allergens, do not seem to be relevant allergens in kiwi fruit.     

IgE reactivity pattern to timothy and birch pollen allergens in Finnish and Russian Karelia

BACKGROUND: Little is known about differences in IgE reactivity patterns to individual allergens in random populations. We studied the IgE reactivity profile to individual recombinant (r) and native (n) allergens in sera from subjects sensitized to timothy and/or birch pollen living in Finnish and Russian Karelia. METHODS: Sera from IgE-sensitized adults were obtained from an epidemiological study on a random sample of 1,177 subjects. The IgE reactivity to pollen extracts and eight timothy (rPhl p 1, 2, 5, 6, 7, 11, 12 and nPhl p 4) and three birch pollen allergens (rBet v 1, 2 and 4) were analyzed with UniCAP. RESULTS: The levels of IgE antibodies to timothy and birch pollen were higher in Finnish (median 5.2, range 0.35 to >100 kUA/l,) than in Russian Karelia (median 1.8 kUA/l, range 0.43-25.2 kUA/l, p <0.01). There was a significantly higher prevalence of IgE reactivity to three timothy pollen allergens in Finnish (n=57) than in Russian Karelia (n=12): rPhl p 2, 28 vs. 0%; rPhl p 5, 60 vs. 0%; rPhl p 6, 47 vs. 0%. The prevalence of IgE reactivity to the birch pollen allergens was similar in the two populations. IgE reactivity to rPhl p 2, 5, 6 and 11 was associated with hay fever symptoms. The timothy-pollen-specific serum IgE levels and the numbers of IgE reactivities to individual allergens correlated significantly (rs=0.87, p <0.0001). CONCLUSIONS: The data indicate that timothy- and birch pollen-specific IgE levels are higher in Finnish compared to Russian Karelia. This is reflected in wider IgE reactivity to individual timothy pollen allergens in Finnish Karelia, including the major allergen Phl p 5, and increased pollen allergy.     

Fagales pollen sensitization in a birch-free area: a respiratory cohort survey using Fagales pollen extracts and birch recombinant allergens (rBet v 1, rBet v 2, rBet v 4)

BACKGROUND: Birch allergy is one of the most common pollinosis in areas where exposure to high levels of birch pollen is common. Little is known about birch sensitivity in areas without birch pollen exposure and reactivity to birch-related species within the Fagales order. OBJECTIVE: the aim was to evaluate Fagales reactivity within a population not exposed to birch pollen using epidemiological, diagnostic, and laboratory approaches by means of extracts and allergenic molecules. METHODS: A cohort of 5335 respiratory allergic patients was screened by means of skin testing birch, hazel, and oak pollen extracts. Patients were from a birch-free area, but exposed to other Fagales pollen species. A subset of patients was from an intensively cultivated hazel area. A sample of the Fagales allergic population was tested with other Fagales pollen extract (alder, hornbeam, beech, chestnut) and with apple and hazelnut. IgE detection was performed with birch, hazel, oak, apple, and hazelnut extracts, and with Bet v 1, Bet v 2, Bet v 4, and bromelain. IgE immunoblots were performed using birch and hazel extracts. Epidemiological, clinical, and laboratory data were analysed by stratifying the allergic population. RESULTS: Twenty-five percent of the pollen allergic cohort was skin test positive to at least one of the three Fagales species. Combined reactivity to the three species was recorded in 80% of this cohort. Isolated hazel pollen reactivity was recorded in 13.5% of the Fagales allergic patients. Sixty-six percent of these subjects were from the intensively cultivated hazel area. Reactivity to apple and hazelnut was detected by skin test (40%) and IgE reactivity (60%), but only 19% of the positive patients reported symptoms related to at least one of the two foods. Reactivity to Bet v 1 was recorded in 84% of the birch/hazel/oak co-reactivity group, and in 28% of the subjects with the same co-reactivity, but associating a multiple pollen sensitization. IgE to Bet v 2 (50%) and Bet v 4 (23%) panallergens were recorded positive in the latter subset. Bet v 1 prevalence ranged between 48% and 21% among subgroups of patients coming from different areas. Furthermore, an IgE reactivity to hazel-restricted allergenic components was detected among subjects coming from the same area and having a hazel isolated reactivity. CONCLUSION: Fagales allergy can be found in birch-free areas caused by the exposure to other Fagales species. Birch allergens can be useful for mimicking the allergenic extract, but are also the exclusive tools for a fine diagnostic and epidemiological approach to Fagales pollen allergy. Allergenic molecules from the hazel family will increase the panel of available reagents for the molecule-based approach to allergy diagnosis and therapy.     

Immune reactivity of candidate reference materials

Immune reactivity is a key issue in the evaluation of the quality of recombinant allergens as potential reference materials. Within the frame of the CREATE project, the immune reactivity of the natural and recombinant versions of the major allergens of birch pollen (Bet v 1), grass pollen (Phl p 1 and 5), olive pollen (Ole e 1), and house dust mite (Der p 1 and 2, and Der f 1 and 2) was analysed. The IgE binding capacity of the allergens was studied by direct RAST and RAST inhibition, and their biological activity by basophil histamine release, using sera of allergic patients selected across Europe. For birch pollen, rBet v 1 is an excellent mimic of the natural allergen. For grass pollen, rPhl p 1 showed a significant lower IgE reactivity and was not considered a suitable candidate, whereas rPhl p 5a exhibited an immune reactivity closer to that of its natural counterpart. For olive, rOle e 1 had a lower IgE binding capacity in RAST but a higher biological activity in histamine release. For house dust mite, recombinant group 1 allergens were significantly less potent than their natural counterparts, but recombinant group 2 allergens were close mimics of their natural homologues.     

Evolution of IgM, IgE and IgG(1-4 )antibody responses in early childhood monitored with recombinant allergen components: implications for class switch mechanisms

The formation of IgE antibodies against environmental allergens represents the hallmark of type I allergy. Data from in vitro cultured cells and experimental animal models provide controversial evidence for isotype switching from IgM to IgE production via sequential as well as non-sequential (i.e. direct) class switch. We analyzed the evolution of IgE responses in 11 children developing birch pollen and/or grass pollen allergy during the first 7 years of life using purified recombinant allergen molecules (major birch pollen allergen, Bet v 1; major timothy grass pollen allergens, Phl p 1, Phl p 2, Phl p 5). Demographic, clinical and serological data indicated a postnatal sensitization to pollen allergens. A parallel development of IgG(1-4) and IgE responses to recombinant allergen molecules compatible with a strictly sequential class switch to IgE was observed only in one child. The only partly synchronized and dissociated development of allergen-specific antibody responses found in all other cases can be best explained by a partly sequential class switch involving few switch stations or, more likely, by direct class switching. Kinetics and courses of allergen-specific antibody responses (IgM, IgG(1-4), IgE) during the first years of life suggest that, once established, allergen-specific IgE responses are driven by antigen contact rather than by cytokines controlling class switch to IgE.     

Transplacental priming of the human immune system with environmental allergens can occur early in gestation

BACKGROUND: Allergen-specific T cells play an important role in the allergic immune response to various environmental allergens. In vitro studies have shown that T-cell responses to these allergens do occur prenatally. Some allergens (milk proteins) appear to lead more often to fetal T-cell priming than others (house dust mite allergen, ovalbumin, and birch and grass pollen allergens). OBJECTIVE: We sought to determine the window of opportunity for prenatal T-cell priming with inhalant and nutritive allergens. METHODS: The T-cell reactivity of cord blood cells derived through cordocentesis from unborn (n = 62) and term babies (n = 114) in response to inhalant allergens (birch pollen major allergen, recombinant Bet v 1, and timothy grass major allergen, recombinant Phl p 1) was investigated. RESULTS: The results demonstrate that allergen-specific T-cell reactivity is as common in preterm as in term infants (Bet v 1, 8% and 5%, respectively; Phl p 1, 20% and 25%, respectively). CONCLUSIONS: Our data support the hypothesis that differential handling of the allergenic proteins by the feto-placental barrier and possibly by antigen-presenting cells may directly modulate the ensuing T-cell immune response.     

Immunotherapy with a modified birch pollen extract in allergic rhinoconjunctivitis: clinical and immunological effects

Background Modification of allergens by glutaraldehyde in extracts used for immunotherapy reduces the risk for side‐effects, but the therapeutic efficacy of such extracts still requires further evaluation. The aim of this study was to show the efficacy and safety of immunotherapy with a single‐strength glutaraldehyde‐modified aluminium hydroxide‐adsorbed extract of birch pollen. Methods In a multi‐centre, randomized, placebo‐controlled double‐blind setting, starting in 2001 between 1 August and 15 December, birch pollen‐allergic subjects (n=62) were injected subcutaneously with increasing doses of the allergen extract or placebo at weekly intervals over a 6‐week period (or longer if adverse reactions occurred). Maintenance dose was given monthly for at least 18 months till June 2003. Efficacy was evaluated on the basis of the clinical index score (CIS), a combined symptom and medication score. Results Fifty‐eight patients could be evaluated for clinical efficacy. Treatment with the birch pollen extract resulted in a lower CIS for the eye and nose during the peak birch pollen season of 2003, compared with placebo (reductions of 42% and 31%, respectively) (P=0.017 and 0.039). Active treatment induced IgG and IgG4 antibodies reacting with Bet v 1 (P<0.001). Sera from treated patients had a blocking effect on Bet v 1‐induced basophil activation (P<0.04). No major adverse reactions occurred, and local reactions, if occurring, were mild. Conclusion Immunotherapy with a modified slow‐release birch pollen extract, administered in a single‐strength preparation with a rapid dose increase, is safe and efficacious. IgG and IgG4 antibodies against native Bet v 1 are induced, which block basophil activation.     

Identification of B-cell epitopes of Bet v 1 involved in cross-reactivity with food allergens

Background:  The pollen-food syndrome (PFS) is an association of food allergies to fruits, nuts, and vegetables in patients with pollen allergy. Mal d 1, the major apple allergen, is one of the most commonly associated food allergens for birch pollen-allergic patients suffering from PFS. Although the reactions are due to cross-reactive IgE antibodies originally raised against pollen Bet v 1, not every Bet v 1-allergic patient develops clinical reactions towards apple.
Aim of the study:  We speculate that distinct IgE epitopes are responsible for the clinical manifestation of PFS. To test this hypothesis we grafted five Mal d 1 stretches onto Bet v 1. The grafted regions were 7- or 8-amino acids long encompassing amino acids residues previously shown to be crucial for IgE recognition of Bet v 1.
Methods:  A Bet v 1-Mal d 1 chimeric protein designated BMC was expressed in Escherichia coli and purified to homogeneity. IgE reactivity of BMC was tested with patients' sera originating from (i) Bet v 1-allergic patients displaying no clinical symptoms upon ingestion of apples; and (ii) Bet v 1-allergic patients displaying allergic symptoms upon ingestion of apples and other Bet v 1-related foods.
Results and conclusion:  Compared to birch pollen-allergic individuals, patients suffering from PFS showed significantly higher IgE reactivity with BMC (chimeric protein). The results suggest that the Mal d 1 regions grafted onto the Bet v 1 sequence comprise important IgE epitopes recognized by Bet v 1-allergic patients suffering from allergy to apples.     

Immunologic significance of respirable atmospheric starch granules containing major birch allergen Bet v 1

BACKGROUND: Birch-pollen allergens are an important cause of early spring hay fever and allergic asthma. Recently, we reported a mechanism for the release of respirable allergenic particles from birch pollen containing the major allergen Bet v 1. In this study, we aimed to assess the immunologic significance of the released Bet v 1-containing starch granules in the environment. METHODS: A two-site monoclonal antibody-based assay (ELISA) was employed to quantitate Bet v 1 in high-volume air sampler filter extracts, and immunogold-labelling was used on sections of these extracts to localize Bet v 1. Immunoblot analyses were performed with pooled sera from patients sensitive to birch pollen. RESULTS: Atmospheric starch granules contained Bet v 1, and the concentration increased upon light rainfall. Sera from patients allergic to birch allergens recognized extracts from isolated starch granules. CONCLUSIONS: The clinical implications of these findings are that starch granules released from birch pollen are potentially able to trigger allergic asthmatic reactions to Bet v 1, since the allergen occurs in respirable particles. Thus, clinicians can advise asthma patients to remain indoors on days of light rainfall during the birch-pollen season to avoid high levels of allergen exposure.     

Intranasal administration of allergen increases specific IgE whereas intranasal omalizumab does not increase serum IgE levels—A pilot study

Background

Administration of the therapeutic anti‐IgE antibody omalizumab to patients induces strong increases in IgE antibody levels.

Objective

To investigate the effect of intranasal administration of major birch pollen allergen Bet v 1, omalizumab or placebo on the levels of total and allergen‐specific IgE in patients with birch pollen allergy.

Methods

Based on the fact that intranasal allergen application induces rises of systemic allergen‐specific IgE, we performed a double‐blind placebo‐controlled pilot trial in which birch pollen allergic subjects were challenged intranasally with omalizumab, placebo or birch pollen allergen Bet v 1. Total and allergen‐specific IgE, IgG and basophil sensitivity were measured before and 8 weeks after challenge. For control purposes, total, allergen‐specific IgE levels and omalizumab‐IgE complexes as well as specific IgG levels were studied in subjects treated subcutaneously with either omalizumab or placebo. Effects of omalizumab on IgE production by IL‐4/anti‐CD40‐treated PBMCs from allergic patients were studied in vitro.

Results

Intranasal challenge with Bet v 1 induced increases in Bet v 1‐specific IgE levels by a median of 59.2%, and this change differed significantly from the other treatment groups (P = .016). No relevant change in allergen‐specific and total IgE levels was observed in subjects challenged with omalizumab. Addition of omalizumab did not enhance IL‐4/anti‐CD40‐induced IgE production in vitro. Significant rises in total IgE (mean IgE before: 131.83 kU/L to mean IgE after: 505.23 kU/L) and the presence of IgE‐omalizumab complexes were observed after subcutaneous administration of omalizumab.

Conclusion

Intranasal administration of allergen induced rises of allergen‐specific IgE levels, whereas intranasal administration of omalizumab did not enhance systemic total or allergen‐specific IgE levels.     

Gastrointestinal digestion of Bet v 1-homologous food allergens destroys their mediator-releasing, but not T cell-activating, capacity

BACKGROUND: Food allergy to apples, hazelnuts, and celery is frequent in individuals with birch pollen allergy because IgE antibodies specific for the major birch pollen allergen, Bet v 1, cross-react with structurally related allergens in these foods. In addition, T lymphocytes specific for Bet v 1 also cross-react with these dietary proteins. OBJECTIVE: We sought to evaluate the effects of simulated gastrointestinal degradation of Bet v 1-related food allergens on their mediator-releasing and T cell-activating capacity. METHODS: Recombinant Mal d 1, Cor a 1.04, and Api g 1 were incubated separately with pepsin and trypsin. Binding of IgE was tested in immunoblots. After successive incubation with both enzymes, allergens were tested in mast cell mediator release assays and used to stimulate PBMCs and Bet v 1-specific T-cell lines and clones. Proteolytic fragments of allergens were analyzed and sequenced by means of mass spectrometry. RESULTS: Pepsin completely destroyed IgE binding of all allergens within 1 second, and trypsin completely destroyed IgE binding of all allergens within 15 minutes, except for the major hazelnut allergen, which remained intact for 2 hours of trypsinolysis. Allergens after gastrointestinal digestion did not induce basophil activation but induced proliferation in PBMCs from allergic and nonallergic individuals. Digested Mal d 1 and Cor a 1.04 still activated Bet v 1-specific T cells, whereas digested Api g 1 did not. Different proteolytic fragments of Mal d 1 and Cor a 1.04 matching relevant Bet v 1 T-cell epitopes were found. CONCLUSION: Gastrointestinal degradation of Bet v 1-related food allergens destroys their histamine-releasing, but not T cell-activating, property. Our data emphasize that birch pollen-related foods are relevant activators of pollen-specific T cells.     

Is allergy immunotherapy with birch sufficient to treat patients allergic to pollen of tree species of the birch homologous group?

Pollen from various Fagales tree species prolongs the season and makes tree pollen allergy a major health problem. Despite involving the same causative allergens, allergy immunotherapy (AIT) treatment habits differ significantly across different geographical regions. Diagnosis and treatment with AIT in patients allergic to tree pollen were discussed by a group of German medical experts who give practical recommendations based on the available data. Regulatory perspective: According to current guidelines on allergen products, birch pollen are the representative allergen source of the birch homologous group including several Fagales trees based on sequence and structural similarity of their allergen proteins. Immunological perspective: A high level of IgE cross-reactivity towards allergens from the birch homologous group has been observed in basic research and clinical trials. Clinical perspective: Clinical trial data show that the efficacy of birch pollen AIT is not only related to birch pollen allergy but extends to pollen from other trees, especially alder, hazel and oak. In order to optimize diagnosis and treatment of tree pollen allergy, the experts recommend to focus diagnosis and respective treatment with AIT primarily to birch as the representative allergen of the Fagales tree homologous group, but further diagnostics may be needed for some patients to determine adequate treatment.