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Dupilumab is a monoclonal antibody against the IL‐4 receptor alpha which has shown efficacy in T2 high severe asthmatics in phase 3 randomized controlled trials. The purpose of this real‐life study is to demonstrate the real‐life effectiveness of dupilumab in Austrian severe asthma patients. We retrospectively analyzed all patients receiving dupilumab at our severe asthma clinic. Thirteen patients have so far received dupilumab at our center. The primary outcome, asthma control questionnaire 6‐item scale at 2 weeks, improved by 0.57 points (p = .014), which is statistically and clinically significant. Similarly, the asthma control test at 4 weeks improved by 3.91 points (p = .024), also statistically and clinically significant. Improvements in forced expiratory volume in 1 s at 2 weeks were neither statistically, nor clinically significant. Improvements at 4 weeks (+220 ml, p = .041), and 3 months (+229 ml, p = .006), were statistically significant and clinically borderline significant. No severe adverse events or hypereosinophilia were observed. No adverse events led to treatment discontinuation. Most patients (85%) had previously received monoclonal antibody treatment for severe asthma. Previous monoclonal antibody treatment had been discontinued in these patients due to a lack of clinical response. Dupilumab is effective and safe in Austrian real‐life severe asthmatics. It provides a possible treatment strategy for T2 high severe asthmatics who do not qualify for anti‐immunoglobulin E or anti‐IL5/IL5R monoclonal antibody treatments or do not adequately respond to these., This is a real‐life study that shows that dupilumab is effective and safe in Austrian real‐life severe asthmatics. It rapidly improved asthma control. These improvements are comparable to previous randomized controlled trials.

Background: Efficacy of mepolizumab in severe eosinophilic asthma has been demonstrated in large randomized controlled trials (RCTs) but patients included in RCTs poorly reflect real-life patients. Objectives: The objective was to investigate whether mepolizumab is effective in a real-life setting. The primary outcome was patient reported asthma control (asthma control test, ACT) Methods: In this single-centre, single-arm, real-life study patients received 100 mg mepolizumab by subcutaneous injection every four weeks for treatment of severe eosinophilic asthma. ACT, FEV1 and OCS dose were collected at baseline and every four weeks for up to 24 weeks. Results: Thirty-five patients with a mean age of 57 years (60% female) were included. The median ACT at baseline was 14.5 and almost two-thirds of patients were on OCS (median dose 9.3 mg). Already at the first follow-up visit, four weeks after the first treatment, median ACT increased to 18 (+3.5, p Conclusion: Mepolizumab is effective and safe in severe eosinophilic asthmatics. This effectiveness is comparable to the efficacy seen in large RCTs.

Amidst the current pandemic there is only little clinical evidence regarding COVID-19 infections in asthma patients. Chinese data [1, 2] suggests that asthma patients might not be of an elevated risk of severe infections. A recent article by Carli et al. [3] hypothesises that asthma might even have a protective effect in COVID-19 infections. It is important to point out, that this is purely theoretical. Eosinophils from healthy probands have an antiviral activity against respiratory syncytial virus and influenza virus, but not eosinophils collected from asthma patients [4]. Eosinopenia, alongside lymphopenia has been seen in COVID-19 patients [2]. Both eosinopenia and lymphopenia are more common in in patients with COVID-19 pneumonitis compared to patients with non-COVID-19 viral pneumonitis [5]. Azkur et al. attribute this to an overwhelming type 1 response [6].

Mepolizumab was effective in several randomized clinical trials (RCTs) in patients with severe eosinophilic asthma, but evidence for symptom control in a real-world population is scarce.To assess asthma symptom control, lung function, use of oral corticosteroids, and biomarkers after mepolizumab initiation in real-world clinical practice.Thirty-five adult patients with severe eosinophilic asthma and inadequate asthma symptom control, including former smokers and patients with cardiac disease, were enrolled in a prospective single-arm real-world study. Asthma control tests (ACT), exacerbations, spirometry (pre-bronchodilator forced expiratory volume in 1 s [FEV1]), and oral corticosteroid doses were documented. Further assessments included peripheral blood eosinophil counts and adverse events.After mepolizumab initiation asthma symptom control was significantly improved with the median ACT score of 12.5 at baseline (interquartile range [IQR ]10.5-19.5) rising to 19 (15-22.5) after 4 weeks. The improvement was maintained throughout the observation period of 20 weeks. Likewise, exacerbations were reduced. After 8 weeks of mepolizumab daily OCS doses were reduced from 6.25 mg daily (0-20) at baseline to 2.5 mg daily (0-11.9) at week 8 (P 0.001). FEV1 remained generally unchanged during the course of the study. Eosinophil counts rapidly declined and remained at a low level during the observation period. No new safety signals were observed in this study.Mepolizumab improved asthma symptom control and had a steroid-sparing effect. Efficacy in this real-world study was comparable to RCTs, despite a history of smoking and comorbidities in many of the patients included.

Introduction XC8 (histamine glutarimide) is a novel agent which targets eosinophilic migration and mast cell degranulation and has shown anti-asthmatic effects in animal studies. Objective The objective of this placebo-controlled phase 1 study was to assess the safety of oral XC8 and to evaluate its pharmacokinetic and pharmacodynamic properties. Methods 32 healthy volunteers in three dose-escalation treatment groups (10 mg [n = 8], 50 mg [n = 8] and 200 mg [n = 16]) were randomized in a 3:1 ratio to XC8 or placebo respectively. The subjects received a single dose of the drug at Day 1 and then once-daily for 14 days (Days 8–21). Results No severe adverse events occurred. The number of adverse events was similar in the treatment arms compared to placebo and all subjects completed the study as planned. No clinically significant changes occurred in hematologic and biochemical blood tests in subjects receiving XC8. The pharmacokinetic data showed similar dose and time dependent mean plasma XC8 concentrations after single (Day 1) and multiple (Day 21) dosing. The mean maximum concentrations were 114–1993 ng/mL after single and 115–2089 ng/mL after multiple dosing. The mean times to maximum concentration were 0.68–1.01 and 0.67–0.98 h, respectively. There was no evidence for accumulation of XC8 after multiple dosing. Conclusion XC8 was safe and well tolerated. A phase 2 study is being performed to further evaluate the potential role of XC8 in asthma treatment. Trial registration ClinicalTrials.gov, NCT02882217.

Objective Evidence of the efficacy of single-inhaler triple therapy in COPD patients inferred from RCTs has not been assessed in a real-world setting in Austria. In this non-interventional study (NIS) tolerability and effectiveness of extrafine beclometasone-dipropionate, formoterol-fumarate and glycopyrronium (Trimbow® 87/5/9 μg) was evaluated in COPD patients. Methods A prospective NIS was conducted over 52 weeks in 24 sites in Austria. Eligible COPD patients had an indication for treatment with single-inhaler BDP/FF/G. In this study tolerability, lung function, exacerbation rate, symptom scores and CAT scores were recorded. Results 265 patients with moderate to very severe airflow limitation (GOLD Grade 2–4: 96.2%) and persistent symptoms (GOLD B: 62.3%, GOLD D: 34%) according to the 2018 GOLD Report were included. After 52 weeks, a significant improvement was detected in lung function (FEV1, FEV1% predicted and FVC; p Conclusions The present results support the tolerability and effectiveness of extrafine BDP/FF/G in COPD patients in a real-world setting, showing an improvement in lung function, symptom control and a significant reduction in exacerbations.

XC8 (histamine glutarimide) is a non-steroidal anti-inflammatory anti-bronchoconstriction agent which targets eosinophilic migration and mast cell degranulation by inhibition of chemokines (CCL2, CCL7, CCL8, CCL13). Previous animal studies have shown beneficial effects of XC8 on airway inflammation. The primary objective of this double-blind placebo-controlled multi-center dose-escalating phase-1 study was to assess the safety of oral XC8. The secondary objective was evaluating the pharmacokinetics (PK). The study population consisted of 32 healthy female (47%) and male adults. Three dose-escalation cohorts (10 mg [n=8], 50 mg [n=8] and 200 mg [n=16]) in two centers were randomized in a 3:1 ratio. The subjects received a single dose at Day 1 and then once-daily for 14 days (Days 8-21). Safety data was collected until Day 36. PK data were collected before (Days 1 and 8-21) and 20 min, 30 min, 1, 2, 4, 8 and 24h after (Days 1 and 21) the administration of the investigational product, respectively. No severe adverse events (AE) occurred. No AEs led to study discontinuation, all subjects completed the study as planned. AEs were not increased in the treatment arms compared to placebo. No clinically significant changes occurred in the safety laboratory in subjects receiving XC8. The PK data showed similar dose and time dependent mean plasma XC8 concentrations both after single (Day 1) and multiple (Day 21) dosing. The median time to maximum plasma concentration was 0.68-1.01 hours after single and 0.67-0.98 hours after multiple dosing. There was no evidence for accumulation of XC8 and it showed linear PK. XC8 was safe and well tolerated. A phase 2 study will be performed to further evaluate the potential role of XC8 in asthma treatment.

The inhaled long-acting muscarinic antagonist aclidinium bromide has been shown to significantly improve lung function parameters and symptom severity in patients with COPD in randomised placebo- and active-controlled clinical studies. To obtain a comprehensive view of the treatment effects, patient-reported outcomes were investigated in a real-life COPD population in routine clinical practice in Austria.Multicentre, prospective, non-interventional study in patients with COPD who were newly initiated on treatment with Eklira® Genuair® (aclidinium bromide; recommended dose 400 μg twice daily) as first-line or add-on therapy. Patients were either treatment naïve or switched from other COPD medications. Health-related quality of life by means of the COPD Assessment Test™ (CAT) and symptom-related variables were evaluated at the first visit (baseline) and after approximately 12 weeks of treatment. Features of the inhaler were assessed by patients and physicians at the follow-up visit.A total of 795 COPD patients (56% male; median age: 64 years) were enrolled and treated. During the observational period, the proportion of patients with at least moderate nighttime symptoms, early-morning symptoms, and limitations in morning activities decreased from 45.0% to 21.4%, from 57.7% to 26.0%, and from 49.9% to 25.3%, respectively. All improvements from baseline in symptom severity and activity limitation were statistically significant (p0.0001, all tests). The mean (±SD) frequency of nocturnal awakenings decreased from 1.2 (±1.4) to 0.7 (±1.2) times per night (p0.0001). Quality of life improved significantly in patients treated with aclidinium bromide over 3 months compared to baseline (p0.0001; mean CAT total score: 18.5 ± 7.5 vs. 13.8 ± 7.3). Up to 90% of the patients and up to 91% of the physicians assessed individual features of the inhaler as 'very good' or 'good'. Aclidinium bromide was well tolerated; 6.9% of the patients reported adverse drug reactions, none of which were serious.This non-interventional study indicated beneficial effects of Eklira® Genuair® in the treatment of COPD with regard to nighttime and early-morning symptoms, limitation of morning activities, and quality of life under routine conditions. The acceptance of the inhaler device was high, which is a prerequisite to ensure adherence in long-term therapy.

Opinion statement Allergic diseases are among the most common health issues worldwide. Specific immunotherapy has remained the only disease-modifying treatment, but it is not effective in all patients and may cause side effects. Over the last 25 years, allergen molecules from most prevalent allergen sources have been isolated and produced as recombinant proteins. Not only are these molecules useful in improved allergy diagnosis, but they also have the potential to revolutionize the treatment of allergic disease by means of immunotherapy. Panels of unmodified recombinant allergens have already been shown to effectively replace natural allergen extracts in therapy. Through genetic engineering, several molecules have been designed with modified immunological properties. Hypoallergens have been produced that have reduced IgE binding capacity but retained T cell reactivity and T cell peptides which stimulate allergen-specific T cells, and these have already been investigated in clinical trials. New vaccines have been recently created with both reduced IgE and T cell reactivity but retained ability to induce protective allergen-specific IgG antibodies. The latter approach works by fusing per se non-IgE reactive peptides derived from IgE binding sites of the allergens to a virus protein, which acts as a carrier and provides the T-cell help necessary for immune stimulation and protective antibody production. In this review, we will highlight the different novel approaches for immunotherapy and will report on prior and ongoing clinical studies.

Allergen-specific immunotherapy is the only allergen-specific and disease-modifying treatment for allergy. The construction and characterization of a vaccine for birch pollen allergy is reported. Two nonallergenic peptides, PA and PB, derived from the IgE-reactive areas of the major birch pollen allergen Bet v 1 were fused to the hepatitis B surface protein, PreS, in four recombinant fusion proteins containing different numbers and combinations of the peptides. Fusion proteins expressed in Escherichia coli and purified to homogeneity showed a lack of IgE reactivity and allergenic activity when tested with sera and basophils from patients allergic to birch pollen. Compared to Bet v 1 allergen, peptides PA and PB showed reduced T cell activation in PBMCs from allergic patients, whereas PreS fusion proteins induced less IL-5 and more IL-10 and IFN-γ. Immunization of rabbits with the fusion proteins, in particular with a PreS fusion protein 2PAPB-PreS, containing two copies of each peptide, induced high levels of IgG Abs against the major IgE-reactive site on Bet v 1 and related allergens. These IgG Abs inhibited allergic patients’ IgE binding to Bet v 1 better than did IgG induced by immunization with complete Bet v 1. Furthermore, 2PAPB-PreS–induced IgG inhibited Bet v 1–induced basophil activation in allergic patients and CD23-facilitated allergen presentation. Our study exemplifies novel beneficial features for a PreS carrier–based peptide vaccine for birch pollen, which, in addition to the established reduction in allergenic activity, include the enhanced focusing of blocking Ab responses toward IgE epitopes, immunomodulatory activity, and reduction of CD23-facilitated allergen presentation.

Background The production of allergen-specific IgE antibodies is a hallmark of IgE-mediated allergy but the contribution of blood cells to allergen-specific IgE production in allergic patients has not been studied in detail. Objective Aim of this study was the characterization of IgE-producing cells in the blood of allergic patients and the determination of the amount of IgE antibodies which are produced by these cells in relation to total amounts of circulating specific IgE. Methods Peripheral blood mononuclear cells (PBMCs) were isolated from allergic patients and cell populations were purified or depleted using magnetically labelled antibodies directed against specific cell surface markers (CD19, CD20, CD22, CD27, CD38, CD126, CD138, CD203c). Allergen-specific IgE was measured in serum samples and cell culture supernatants by quantitative ImmunoCAP measurements and by ELISA using purified recombinant allergens. IgE transcripts were detected using RT-PCR with primers specific for human IgE. Results We found that allergen-specific IgE levels in PBMC supernatants correlated strongly with specific serum IgE but represented less than 1% of circulating IgE. Depletion of basophils resulted in substantial reduction of allergen-specific IgE levels in PBMC culture supernatants suggesting that an important source of allergen-specific IgE in PBMC supernatants could be IgE derived from the surface of basophils. Newly synthesized IgE was derived from CD138+ plasma cells, but not from B and B memory cells, and accounted for only approximately 0.2% of circulating IgE in blood. Conclusion and Clinical Relevance Our finding that the majority of allergen-specific IgE in the peripheral blood is not derived from IgE-secreting cells in the blood suggests local IgE production in tissues as a major source for allergen-specific IgE and possible target for therapeutic intervention.

Immunoglobulin E-mediated allergies affect more than 25% of the population. Allergen exposure induces a variety of symptoms in allergic patients, which include rhinitis, conjunctivitis, asthma, dermatitis, food allergy and life-threatening systemic anaphylaxis. At present, allergen-specific immunotherapy (SIT), which is based on the administration of the disease-causing allergens, is the only disease-modifying treatment for allergy. Current therapeutic allergy vaccines are still prepared from relatively poorly defined allergen extracts. However, with the availability of the structures of the most common allergen molecules, it has become possible to produce well-defined recombinant and synthetic allergy vaccines that allow specific targeting of the mechanisms of allergic disease. Here we provide a summary of the development and mechanisms of SIT, and then review new forms of therapeutic vaccines that are based on recombinant and synthetic molecules. Finally, we discuss possible allergen-specific strategies for prevention of allergic disease.

The intestinal peptide transporter PEPT1 mediates the uptake of di- and tripeptides derived from dietary protein breakdown into epithelial cells. Whereas the transporter appears to be essential to compensate for the reduced amino acid delivery in patients with mutations in amino acid transporter genes, such as in cystinuria or Hartnup disease, its physiological role in overall amino acid absorption is still not known. To assess the quantitative importance of PEPT1 in overall amino acid absorption and metabolism, PEPT1-deficient mice were studied by using brush border membrane vesicles, everted gut sacs, and Ussing chambers, as well as by transcriptome and proteome analysis of intestinal tissue samples. Neither gene expression nor proteome profiling nor functional analysis revealed evidence for any compensatory changes in the levels and/or function of transporters for free amino acids in the intestine. However, most plasma amino acid levels were increased in Pept1−/−compared with Pept1+/+animals, suggesting that amino acid handling is altered. Plasma appearance rates of15N-labeled amino acids determined after intragastric administration of a low dose of protein remained unchanged, whereas administration of a large protein load via gavage revealed marked differences in plasma appearance of selected amino acids. PEPT1 seems, therefore, important for overall amino acid absorption only after high dietary protein intake when amino acid transport processes are saturated and PEPT1 can provide additional absorption capacity. Since renal amino acid excretion remained unchanged, elevated basal concentrations of plasma amino acids in PEPT1-deficient animals seem to arise mainly from alterations in hepatic amino acid metabolism.

Allergic inflammation is based on the cross-linking of mast cell and basophil-bound IgE Abs and requires at least two binding sites for IgE on allergens, which are difficult to characterize because they are often conformational in nature. We studied the IgE recognition of birch pollen allergen Bet v 1, a major allergen for >100 million allergic patients. Monoclonal and polyclonal Abs raised against Bet v 1-derived peptides were used to compete with allergic patients’ IgE binding to Bet v 1 to search for sequences involved in IgE recognition. Strong inhibitions of patients’ IgE binding to Bet v 1 (52–75%) were obtained with mAbs specific for two peptides comprising aa 29–58 (P2) and aa 73–103 (P6) of Bet v 1. As determined by surface plasmon resonance, mAb2 specific for P2 and mAb12 specific for P6 showed high affinity, but only polyclonal rabbit anti-P2 and anti-P6 Abs or a combination of mAbs inhibited allergen-induced basophil degranulation. Thus, P2 and P6 define a surface patch on the Bet v 1 allergen, which allows simultaneous binding of several different IgE Abs required for efficient basophil and mast cell activation. This finding explains the high allergenic activity of the Bet v 1 allergen. The approach of using peptide-specific Abs for the mapping of conformational IgE epitopes on allergens may be generally applicable. It may allow discriminating highly allergenic from less allergenic allergen molecules and facilitate the rational design of active and passive allergen-specific immunotherapy strategies.

Background: Expression of allergens in human cells is a prerequisite for the development of antigen-specific cell therapy in IgE-mediated allergy. We developed a strategy how the clinically relevant major grass pollen allergen Phl p 5 can be efficiently secreted or expressed on the surface of human cells with preserved allergenic activity. Methods: The cDNA of Phl p 5 was fused to a leader peptide with or without a transmembrane domain and both constructs were ligated into a mammalian expression vector. Transfection of these plasmids into human cells resulted in a membrane-anchored or secreted version of Phl p 5, respectively, as determined by ELISA or flow cytometric analysis. Results: Both the secreted and membrane-anchored Phl p 5 proteins bound IgE from allergic patients in an immunoblot assay and induced specific histamine release and CD203c upregulation in basophils of grass pollen-allergic patients. Proliferation of peripheral blood mononuclear cells from Phl p 5-allergic individuals was induced upon stimulation with both variants of Phl p 5 expressed in human cells similar to recombinant Phl p 5. Conclusions: Secreted and membrane-anchored Phl p 5 expressed in human cells preserved B cell as well as T cell epitopes and may be used to develop and test various cell-based strategies for allergen-specific immunomodulation and to delineate the tolerance mechanisms involved therein.

Allergen recognition by IgE antibodies is a key event in allergic inflammation. In this study, the IgE IGHV repertoires of individuals with allergy to the major birch pollen allergen, Bet v 1, were analyzed over a four years period of allergen exposure by RT-PCR and sequencing of cDNA. Approximately half of the IgE transcripts represented non-redundant sequences, which belonged to seventeen different IGHV genes. Most variable regions contained somatic mutations but also non-mutated sequences were identified. There was no evidence for relevant increases of somatic mutations over time of allergen exposure. Highly similar IgE variable regions were found after four years of allergen exposure in the same and in genetically non-related individuals. Our results indicate that allergens select and shape a limited number of similar IgE variable regions in the human IgE repertoire.

Background Commercial extracts used for diagnosis and treatment of allergy are currently prepared from natural allergen sources. The aim of this study was to analyse birch pollen allergen extracts produced for in vivo diagnosis of birch pollen allergy regarding their contents of individual birch pollen allergens (Bet v 1, Bet v 2 and Bet v 4). Methods Protein contents were measured and the allergen composition was analysed by immunoblotting using antibody probes specific for Bet v 1, Bet v 2 and Bet v 4 in birch pollen extracts from five manufacturers of allergen extracts. The contents of the major birch pollen allergen, Bet v 1, were quantified with a specific two-site binding enzyme-linked immunosorbent assay with nanogram sensitivity for Bet v 1. The biological activities of the allergen extracts were evaluated by skin prick testing in birch pollen allergic patients and compared with their sensitization profiles. Results A more than 10-fold variation regarding total protein contents (23·1–314 μg mL−1) and also regarding the amounts of the major birch pollen allergen, Bet v 1 (1·62–19·6 μg mL−1) was found. The highly cross-reactive Bet v 4 allergen was absent in three of the five tested extracts. Furthermore, varying skin test results were obtained in birch pollen allergic patients with the allergen extracts. Conclusions Commercial birch pollen extracts exhibit a considerable variability regarding allergen contents and hence deliver varying in vivo test results. These problems might be overcome with recombinant allergen-based preparations.

Background Increasing evidence suggests that the low-affinity receptor for IgE, CD23, plays an important role in controlling the activity of allergen-specific T cells through IgE-facilitated allergen presentation. Objective We sought to determine the number of CD23 molecules on immune cells in allergic patients and to investigate whether the number of CD23 molecules on antigen-presenting cells is associated with IgE levels and influences allergen uptake and allergen-specific T-cell activation. Methods Numbers of CD23 molecules on immune cells of allergic patients were quantified by using flow cytometry with QuantiBRITE beads and compared with total and allergen-specific IgE levels, as well as with allergen-induced immediate skin reactivity. Allergen uptake and allergen-specific T-cell activation in relation to CD23 surface density were determined by using flow cytometry in combination with confocal microscopy and T cells transfected with the T-cell receptor specific for the birch pollen allergen Bet v 1, respectively. Defined IgE-allergen immune complexes were formed with human monoclonal allergen-specific IgE and Bet v 1. Results In allergic patients the vast majority of CD23 molecules were expressed on naive IgD + B cells. The density of CD23 molecules on B cells but not the number of CD23 + cells correlated with total IgE levels ( R S = 0.53, P = .03) and allergen-induced skin reactions ( R S = 0.63, P = .008). Uptake of allergen-IgE complexes into B cells and activation of allergen-specific T cells depended on IgE binding to CD23 and were associated with CD23 surface density. Addition of monoclonal IgE to cultured PBMCs significantly ( P = .04) increased CD23 expression on B cells. Conclusion CD23 surface density on B cells of allergic patients is correlated with allergen-specific IgE levels and determines allergen uptake and subsequent activation of T cells.

The infection of CD4+ cells by HIV leads to the progressive destruction of CD4+ T lymphocytes and, after a severe reduction of CD4+ cells, to AIDS. The aim of the study was to investigate whether HIV-infected patients with CD4 cell counts

This year we are celebrating not only the centenary of allergen-specific immunotherapy but also the 10-year anniversary of the first administration of recombinant allergen–based vaccines to allergic patients. By using recombinant DNA technology, defined and safe allergy vaccines can be produced that allow us to overcome many, if not all, of the problems associated with the use of natural allergen extracts, such as insufficient quality, allergenic activity, and poor immunogenicity. Here we provide an update of clinical studies with recombinant allergen–based vaccines, showing that some of these vaccines have undergone successful clinical evaluation up to phase III studies. Furthermore, we introduce a strategy for allergen-specific immunotherapy based on recombinant fusion proteins consisting of viral carrier proteins and allergen-derived peptides without allergenic activity, which holds the promise of being free of side effects and eventually being useful for prophylactic vaccination.

Allergen-specific immunotherapy (SIT) is the only specific and disease-modifying approach for the treatment of allergy but several disadvantages have limited its broad applicability. We argue that the majority of the possible disadvantages of SIT such as unwanted effects, poor efficacy and specificity as well as inconvenient application are related to the poor quality of natural allergen extracts, which are the active ingredients of all currently available allergy vaccines. Because of the progress made in the field of molecular allergen characterization, new allergy vaccines based on recombinant allergens, recombinant hypoallergenic allergen derivatives and allergen-derived T cell peptides have entered clinical testing and hold promise to reduce the side-effects and to increase the specificity as well as the efficacy of SIT. Here, we present a refined immunotherapy concept, which is based on the use of peptides derived from allergen surfaces that exhibit reduced, allergen-specific IgE as well as T cell reactivity. These peptides when fused to non-allergenic carriers give rise to allergen-specific protective IgG responses with T cell help from a non-allergenic carrier molecule. We summarize the experimental data demonstrating that such peptide vaccines can bypass allergen-specific IgE as well as T cell activation and may be administered at high doses without IgE- and T cell-mediated side-effects. Should these peptide vaccines prove efficacious and safe in clinical trials, it may become possible to develop convenient, safe and broadly applicable forms of SIT as true alternatives to symptomatic, drug-based allergy treatment.

Summary Background The diagnosis and specific immunotherapy of allergy is currently performed with allergen extracts prepared from natural allergen sources. Objective To analyse commercial timothy grass pollen allergen extracts used for in vivo diagnosis regarding their qualitative and quantitative allergen composition and in vivo biological activity. Methods Antibodies specific for eight timothy grass pollen allergens (Phl p 1, Phl p 2, Phl p 4, Phl p 5, Phl p 6, Phl p 7, Phl p 12, Phl p 13) were used to detect these allergens in timothy grass pollen extracts from four manufacturers by immunoblotting. ELISA assays were developed and used to quantify the three major allergens (Phl p 1, Phl p 2, Phl p 5) in the extracts. The magnitude of skin responses to the four extracts was studied by skin prick testing in 10 grass pollen-allergic patients. Results The allergen extracts showed broad variations in protein compositions and amounts (24.1‐197.7mg/mL extract). Several allergens could not be detected in certain extracts or appeared degraded. A considerable variability regarding the contents of major allergens was found (Phl p 1: 32‐384ng/mL; Phl p 2: 1128‐6530ng/mL, Phl p 5: 40‐793ng/mL). Heterogeneous skin test results were obtained with the extracts in grass pollen-allergic patients. Conclusions Timothy grass pollen extracts from different manufacturers exhibit a considerable heterogeneity regarding the presence of individual allergens and hence yield varying in vivo test results. Problems related to the use of natural grass pollen allergen extracts may be circumvented by using defined recombinant grass pollen allergens.

IgE-dependent activation of basophils is associated with upregulation of several surface molecules. We recently identified the surface enzyme aminopeptidase N (CD13) as a novel activation antigen on human basophils. In the present study, we asked whether CD13 can be employed as a novel marker of allergen-induced activation of basophils in allergic individuals. Patients allergic to major allergens from grass pollen (Phl p 1, Phl p 5), birch pollen (Bet v 1), or house dust mites (Der p 2), were examined. Blood basophils were exposed to various concentrations of recombinant allergens for 15 minutes, and examined for expression of CD13 by multicolor flow cytometry. The allergen-induced upregulation of CD13 was compared with allergen-dependent increases in expression of CD63 and CD203c. Exposure to recombinant allergens resulted in an increase in expression of CD13 on basophils in all sensitized individuals, whereas no increase in CD13 was seen in healthy controls. The effects of the recombinant allergens on CD13-expression were dose- and time-dependent, were not observed in the absence of extracellular calcium, and were counteracted by preincubation of basophils with the PI3-kinase-targeting drugs staurosporin and LY294002. There was a good correlation between allergen-induced upregulation of CD13, CD63, and CD203c on basophils. In aggregate, our data show that recombinant allergens promote expression of CD13 on basophils in sensitized individuals. The functional significance and diagnostic implications of this observation remain to be determined.

Background Grasses belong to the most potent allergen sources worldwide. Group 2 grass pollen allergens are recognized by more than 100 million allergic patients. Objective The aim was to develop an assay for the specific detection and quantification of group 2 grass pollen allergens. Methods We have isolated a monoclonal human IgE Fab specific for group 2 grass pollen allergens by combinatorial cloning from lymphocytes of a grass pollen–allergic patient. This Fab was converted into a complete human IgG 1 antibody and used together with rPhl p 2 to develop a competitive ELISA for the specific measurement of group 2 allergens. ELISA plate-bound purified recombinant human Phl p 2–specific IgG 1 is incubated with a constant amount of biotinylated rPhl p 2 competing with increasing concentrations of group 2 allergens to be determined. Defined concentrations of purified rPhl p 2 are used to establish a standard curve. The concentration of unlabeled group 2 allergens can thus be deduced from the displacement of biotinylated rPhl p 2, which can be detected with peroxidase-labeled streptavidin. Results The competition-ELISA measured rPhl p 2 concentrations ranging from 10 ng/mL to 500 ng/mL and allowed to quantify group 2 allergens from 9 different grass families. The results were in good agreement with immunoblot data. Conclusions The described assay can be used for standardization of diagnostic and therapeutic vaccines as well as for the quantification of group 2 allergens in environmental samples.