Serological and skin-test diagnosis of birch pollen allergy with recombinant Bet v I, the major birch pollen allergen

Background Type I allergy represents a severe health problem in industrialized countries where up to 20% of the population suffer froin allergic rhinitis, conjunctivitis and allergic asthma bronchiale and in severe cases from anaphylaxis. leading to death.
Objective The aim of this study was to evaluate recombinant Bet v I, the major birch pollen allergen for in vivo and in vitro diagnosis of birch pollen allergy.
Methods A group of 51 birch pollen allergic patients and eight non-allergic control individuals were tested for birch pollen allergy by skin-prick and intradennal testing, comparing commercial birch pollen extracts with recombinant Bet v I. Quantitative and qualitative serological testing was done with natural and recombinant allergens by radioallergosorbent test (RAST), enzyme-linked immunosorbent assay (ELISA) and immunoblotting.
Results Recombinant Bet v I allowed accurate in vivo and in vitro diagnosis of tree pollen allergy in 49/51 patients tested. No false positive results were obtained in any in vitro assay system (ELISA. Westernblot) or by skin testing (skin-prick, intradermal test) with recombinant Bet v I.
Conclusion Our results document that recombinant Bet v I produced in bacterial expression systems allows accurate in vitro and in vivo diagnosis of birch pollen allergy in > 95% of birch pollen allergic patients.     

The non-specific lipid transfer protein, Ara h 9, is an important allergen in peanut

Background Plant food allergy in the Mediterranean area is mainly caused by non-specific lipid transfer proteins (nsLTP). The aim of this study was to characterize peanut nsLTP in comparison with peach nsLTP, Pru p 3, and assess its importance in peanut allergy.
Methods Peanut-allergic patients from Spain ( n =32) were included on the basis of a positive case history and either a positive skin prick test or specific IgE to peanut. For comparison, sera of 41 peanut-allergic subjects from outside the Mediterranean area were used. Natural Ara h 9 and two isoforms of recombinant Ara h 9, expressed in Pichia pastoris , were purified using a two-step chromatographic procedure. Allergen characterization was carried out by N-terminal sequencing, circular dichroism (CD) spectroscopy, immunoblotting, IgE inhibition tests and basophil histamine release assays.
Results Compared with natural peanut nsLTP, the recombinant proteins could be purified in high amounts from yeast supernatant (45 mg/L). The identity of the proteins was verified by N-terminal amino acid sequencing and with rabbit nsLTP-specific antibodies. CD spectroscopy revealed similar secondary structures for all preparations and Pru p 3. The Ara h 9 isoforms showed 62–68% amino acid sequence identity with Pru p 3. IgE antibody reactivity to rAra h 9 was present in 29/32 Spanish and 6/41 non-Mediterranean subjects. Recombinant Ara h 9 showed strong cross-reactivity to nPru p 3 and similar IgE-binding capacity as nAra h 9. The two Ara h 9 isoforms displayed similar IgE reactivity. In peanut-allergic patients with concomitant peach allergy, Ara h 9 showed a weaker allergenic potency than Pru p 3 in histamine release assays.
Conclusions Ara h 9 is a major allergen in peanut-allergic patients from the Mediterranean area. Ara h 9 is capable of inducing histamine release from basophils, but to a lesser extent than Pru p 3.     

Relevance of Ara h1, Ara h2 and Ara h3 in peanut-allergic patients, as determined by immunoglobulin E Western blotting, basophil–histamine release and intracutaneous testing: Ara h2 is the most important peanut allergen

BACKGROUND: A number of allergenic proteins in peanut has been described and the relative importance of these allergens is yet to be determined. OBJECTIVES: We have investigated the relevance of previously identified peanut allergens in well-characterized peanut-allergic patients by in vitro, ex vivo and in vivo assays. METHODS: Thirty-two adult peanut-allergic patients were included based on careful and standardized patient history and the presence of peanut-specific IgE. The diagnosis peanut allergy was confirmed using double-blind placebo-controlled food challenges in 23 patients. Major peanut allergens Ara h1, Ara h2 and Ara h3 were purified from peanuts using ion-exchange chromatography. IgE immunoblotting was performed and IgE-cross-linking capacity was examined by measuring histamine release (HR) after incubating patient basophils as well as passively sensitized basophils with several dilutions of the allergens. Intracutaneous tests (ICTs) using 10-fold dilution steps of the purified allergens and crude peanut extract were performed. RESULTS: Ara h2 was recognized most frequently (26 out of 32) in all tests and induced both positive skin tests and basophil degranulation at low concentrations, whereas Ara h1 and Ara h3 were recognized less frequently and reacted only at 100-fold higher concentrations as analysed with HR and intracutaneous testing (ICT). Next to the three tested allergens, proteins with molecular weights of somewhat smaller than 15 kDa were identified as a IgE-binding proteins on immunoblot in the majority of the patients (20 out of 32). CONCLUSION: We conclude that Ara h2 is, for our patient group, the most important peanut allergen, and that previously unidentified peanut proteins with molecular weights of somewhat smaller than 15 kDa may be important allergens as well. ICT in combination with basophil-HR and IgE immunoblotting provides insight in the patient specificity towards the individual peanut allergens.     

Nasal challenges with recombinant derivatives of the major birch pollen allergen Bet v 1 induce fewer symptoms and lower mediator release than rBet v 1 wild-type in patients with allergic rhinitis

BACKGROUND: Genetic engineering of the major birch pollen allergen (Bet v 1) has led to the generation of recombinant Bet v 1 derivatives with markedly reduced IgE-binding capacity, but with retained T cell activating ability. OBJECTIVE: To compare the mucosal reactivity to rBet v 1 derivatives with rBet v 1 wild-type as basis for new therapeutic strategies for birch pollen allergy based on mucosal tolerance induction. METHODS: Outside the pollen season, 10 patients with birch pollen allergic rhinitis and mild asthma underwent four nasal challenge-sessions in a randomized, double-blind, and cross-over design, employing increasing doses of rBet v 1 fragment mix, rBet v 1 trimer, rBet v 1 wild-type and diluent (albumin). Nasal lavage fluids (NAL) were collected before the challenge-series as well as 10 min, 4 and 24 h thereafter. Nasal lavage fluid levels of tryptase as well as EPO and ECP were measured as indices of mast cell and eosinophil activity, respectively. RESULTS: All 10 patients tolerated the highest accumulated dose, 8.124 microg, when challenged with rBet v 1 trimer, eight with rBet v 1 fragments compared to one when challenged with rBet v 1 wild-type. No late phase reactions were observed. The change in tryptase levels (pre-challenge vs. 10 min) was significantly lower after challenges with rBet v 1 trimer and rBet v 1 fragments than with rBet v 1 wild-type. The change in EPO/ECP concentration pre-challenge versus 4 h post-challenge was lower for rBet v 1 trimer and the change was significantly lower when pre-challenge versus 24 h post-challenge to rBet v 1 fragments and rBet v 1 wild-type was examined. CONCLUSION: The derivatives induced significantly fewer symptoms and lower mast cell and eosinophil activation than rBet v 1 wild-type upon application to the nasal mucosa. They could in the future be candidates for immunotherapy based on mucosal tolerance induction.     

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.     

Evaluation of recombinant allergens Bet v 1 and Bet v 2 (profilin) by Pharmacia CAP System in patients with pollen-related allergy to birch and apple

Sixty-five patients presenting either rhinoconjunctivitis or asthma and sensitized to pollens of trees of the order Fagales were studied by the Pharmacia CAP system in order to assess specific IgE for the important birch pollen allergens Bet v 1 and Bet v 2. All 65 subjects reacted to at least one of the recombinant birch allergens: 43% to Bet v 1, 30.7% to Bet v 2, and 26% to both. Patients monosensitized to birch did not react to Bet v 2. of patients with a history of oral allergy syndrome after eating apples, 16/28 (57%) reacted to Bet v 1; among 20 polysensitized subjects presenting oral allergy syndrome after consumption of apple, four reacted to Bet v 2 (20%). Among patients with IgE against both recombinant allergens, six (35.30%) presented symptoms of allergy after eating apples. Our results indicate that sensitization to Bet v 1 is specific for birch and apple allergies, whereas sensitization to Bet v 2 is common in polysensitized patients.     

Cloning of the minor allergen Api g 4 profilin from celery (Apium graveolens) and its cross-reactivity with birch pollen profilin Bet v 2

BACKGROUND: Profilin is a panallergen that is recognized by IgE from about 20% of birch pollen- and plant food-allergic patients. A subgroup of celery-allergic patients shows IgE-reactivity with this minor allergen. To investigate the IgE-binding potential and cross-reactivity of celery profilin at the molecular level, this study was aimed at the cloning and immunological characterization of this allergen. OBJECTIVES: Cloning, expression and purification of profilin from celery tuber to characterize its immunological properties and its cross-reactivity with birch pollen profilin. METHODS: Cloning of celery profilin was performed by polymerase chain reaction using degenerated primers and a 5'RACE method for the identification of the unknown 5'-end of the cDNA. Expression was carried out in Escherichia coli BL21 (DE3) using a modified vector pET-30a. The recombinant profilin was purified by affinity chromatography on poly L-proline coupled to sepharose. Immunological characterization was performed by immunoblotting, EAST and IgE-inhibition experiments. RESULTS: The coding region of the cDNA of celery profilin was identified as a 399-bp open reading frame, coding for a protein of 133 amino acids with a calculated molecular weight of 14.3 kDa. The deduced amino acid sequence of the corresponding protein showed high identity with other plant profilins (71-82%) recently described as allergens. Celery profilin was isolated as highly pure nonfusion protein. The IgE-reactivity of celery profilin was similar to that of natural protein. Seven of 17 celery-allergic patients tested presented specific IgE-antibodies to the recombinant protein tested by immunoblotting. Inhibition experiments showed high cross-reactivity of IgE with both profilins from celery and birch pollen. Moreover, the biological activity of recombinant celery profilin was demonstrated by a histamine release assay. CONCLUSIONS: Celery profilin is an important allergenic compound in celery and shows high homology to birch pollen profilin, Bet v 2. According to the revised IUIS allergen nomenclature, we suggest naming the celery profilin Api g 4. In addition to the cross-reacting major allergens Api g 1 and Bet v 1, birch pollinosis and associated allergies to celery can therefore additionally be explained by the cross-reactivity between homologous profilins. Moreover, recombinant Api g 4 may be used for target-specific diagnosis and structural analyses.     

Poor association between allergen-specific serum immunoglobulin E levels, skin sensitivity and basophil degranulation: a study with recombinant birch pollen allergen Bet v 1 and an immunoglobulin E detection system measuring immunoglobulin E capable of binding to FcɛRI

BACKGROUND: Results from several studies indicate that the magnitude of immediate symptoms of type I allergy caused by allergen-induced cross-linking of high-affinity Fc epsilon receptors on effector cells (mast cells and basophils) is not always associated with allergen-specific IgE levels. OBJECTIVE: To investigate the association of results from intradermal skin testing, basophil histamine release and allergen-specific IgE, IgG1-4, IgA and IgM antibody levels in a clinical study performed in birch pollen-allergic patients (n = 18). METHODS: rBet v 1-specific IgEs were measured by quantitative CAP measurements and by using purified Fc epsilon RI-derived alpha-chain to quantify IgE capable of binding to effector cells. Bet v 1-specific IgG subclasses, IgA and IgM levels were measured by ELISA, and basophil histamine release was determined in whole blood samples. Intradermal skin testing was performed with the end-point titration method. RESULTS: Our study demonstrates on the molecular level that the concentrations of allergen-specific IgE antibodies capable of binding to Fc epsilon RI and biological sensitivities are not necessarily associated. A moderate association was found between cutaneous and basophil sensitivity. CONCLUSION: Our results highlight the quantitative discrepancies and limitations of the present diagnostic tools in allergy, even when using a single allergenic molecule. The quantity of allergen-specific serum IgE is only one component of far more complex cellular systems (i.e. basophil-based tests, skin tests) used as indirect diagnostic tests for IgE-mediated allergic sensitivity.     

Development and validation of a structured questionnaire for the diagnosis of oral allergy syndrome in subjects with seasonal allergic rhinitis during the UK birch pollen season

Background Birch pollen–associated oral allergy syndrome, also known as pollen–food syndrome (PFS), is the most common food allergy in adults in the United Kingdom. Because of its characteristic rapid onset of oro‐pharyngeal symptoms associated with specific plant foods, it was hypothesized that a history‐based questionnaire could accurately diagnose PFS in subjects with rhino‐conjunctivitis symptoms in the UK springtime. Objective In this study of diagnostic accuracy, we aimed to validate a simple PFS diagnostic questionnaire and algorithm against a reference diagnostic test method (RTM) comprising diagnosis by expert evaluation of clinical history, skin prick tests and oral food challenge, in subjects reporting allergic rhinitis (AR) in the UK birch pollen season from March to May. Methods Participants were UK adults reporting symptoms of spring time‐AR (hayfever). They self‐completed a diagnostic questionnaire in addition to undergoing an RTM comprising clinical history, skin prick testing to foods and pollens and oral food challenge. Subjects who reported anaphylaxis were excluded on the basis that they required specialist referral. Results One hundred and twenty three subjects took part in the study. Data from 110 participants were analysed; of the 13 exclusions, four provided insufficient data and nine reported anaphylaxis such that they warranted specialist assessment. Fifty‐two participants (47%) were diagnosed with PFS by the RTM in comparison with 51 (46%) by a diagnostic questionnaire and algorithm (P=1.000, McNemar's test). The diagnostic questionnaire and algorithm had a sensitivity of 0.90 (0.78–0.96), a specificity of 0.93 (0.82–0.97), a positive predictive value of 0.92 (0.80–0.97) and a negative predictive value of 0.91 (0.80–0.96) when measured against the RTM. Conclusion and Clinical Relevance The diagnostic questionnaire and algorithm is a practical and robust tool, which enables rapid identification, and therefore management, of individuals with PFS who experience rhino‐conjunctivitis symptoms in the UK birch pollen season. Registered with CinicalTrials.Gov. registration number NCT00854958. Cite this as: I. J. Skypala, M. A. Calderon, A. R. Leeds, P. Emery, S.J Till and S. R. Durham, Clinical & Experimental Allergy, 2011 (41) 1001–1011.     

Mucosal tolerance as therapy of type I allergy: intranasal application of recombinant Bet v 1, the major birch pollen allergen, leads to the suppression of allergic immune responses and airway inflammation in sensitized mice

BACKGROUND: Several studies have demonstrated that mucosal administration of soluble antigens can prevent the onset or reduce the severity of certain autoimmune diseases or allergies. Few studies exist showing the efficacy of mucosal tolerance for therapy of such diseases. OBJECTIVE: The aim of the present study was to modulate an allergic immune response by intranasal antigen administration in an already sensitized organism. METHODS: A murine model of allergic asthma to birch pollen (BP) and its major allergen Bet v 1 was utilized. Sensitized mice were intranasally treated with recombinant (r)Bet v 1 in different concentrations and at different intervals. On the day the mice were killed, blood and bronchoalveolar lavage fluids were taken and immediate type I skin tests were performed. T cell proliferation and cytokine production (interleukin (IL)-5, interferon (IFN)-gamma) were measured in spleen and lung cell cultures. RESULTS: Mucosal treatment with rBet v 1 (3 x 50 microg in 4 day intervals) led to a reduction of type I skin reactions, suppressed immunoglobulin (Ig)G1/IgE antibody levels and markedly decreased IL-5 and IFN-gamma production in vitro in spleen and lung cell cultures. Moreover, lung inflammation (i.e. eosinophilia and IL-5 levels in bronchoalveolar lavage fluids) was significantly suppressed by the treatment. CONCLUSION: Our results demonstrate that intranasal treatment with rBet v 1 reduced systemic allergic immune responses as well as airway inflammation in BP-sensitized mice. We therefore suggest that mucosal tolerance induction with recombinant allergens could be a promising concept for the therapy of allergic diseases.     

Suppression of antigen-specific T- and B-cell responses by intranasal or oral administration of recombinant Bet v 1, the major birch pollen allergen, in a murine model of type I allergy

BACKGROUND: Mucosal (nasal or oral) administration of soluble protein antigens induces a state of antigen-specific immunologic hyporesponsiveness. Several studies have shown that induction of mucosal tolerance can prevent the onset or reduce the severity of certain TH1 -mediated experimental autoimmune diseases. Only a few studies describe similar results for type I allergies, which are caused by excessive TH2 cell activities. OBJECTIVE: We sought to investigate whether mucosal tolerance induction would also be efficient in preventing an allergic type I immune response. METHODS: A murine model of inhalative type I allergy, leading to sensitization to birch pollen and its major allergen Bet v 1 in BALB/c mice, was used. Recombinant Bet v 1 was nasally or orally applied in low doses before sensitization. At the time of death, immediate-type skin tests were performed. Blood was taken, and serum was used for measurement of allergen-specific antibodies. Spleen cell cultures were performed to determine cytokine production (IL-4, IL-5, IL-10, and IFN-gamma), as well as levels of TGF-beta mRNA. RESULTS: Both nasal and oral administration of minimal doses of recombinant Bet v 1 before aerosol sensitization with birch pollen suppressed the allergen-specific antibody production of all isotypes. Consequently, the in vivo type I skin test responses to the allergen were negative in the tolerized, in contrast to the sensitized, group. Moreover, allergen-specific lymphoproliferative responses and cytokine production in vitro (ie, IFN-gamma, IL-4, IL-5, and IL-10) were markedly reduced. In contrast, expression of TGF-beta mRNA was markedly increased in spleen cells from nasally tolerized animals, indicating regulatory mechanisms for tolerance induction. CONCLUSION: We conclude from the present study that nasal, as well as oral, administration of recombinant allergen is an effective way to prevent allergen-specific T- and B-cell responses in a TH2 model.