EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Tree pollen allergens-an update from a molecular perspective

It is estimated that pollen allergies affect approximately 40% of allergic individuals. In general, tree pollen allergies are mainly elicited by allergenic trees belonging to the orders Fagales, Lamiales, Proteales, and Pinales. Over 25 years ago, the gene encoding the major birch pollen allergen Bet v 1 was the first such gene to be cloned and its product characterized. Since that time, 53 tree pollen allergens have been identified and acknowledged by the WHO/IUIS allergen nomenclature subcommittee. Molecule‐based profiling of allergic sensitization has helped to elucidate the immunological connections of allergen cross‐reactivity, whereas advances in biochemistry have revealed structural and functional aspects of allergenic proteins. In this review, we provide a comprehensive overview of the present knowledge of the molecular aspects of tree pollen allergens. We analyze the geographic distribution of allergenic trees, discuss factors pivotal for allergic sensitization, and describe the role of tree pollen panallergens. Novel allergenic tree species as well as tree pollen allergens are continually being identified, making research in this field highly competitive and instrumental for clinical applications.

Ragweed plants grown under elevated CO2 levels produce pollen which elicit stronger allergic lung inflammation

BACKGROUND

Common ragweed has been spreading as a neophyte in Europe. Elevated CO₂ levels, a hallmark of global climate change, have been shown to increase ragweed pollen production, but their effects on pollen allergenicity remain to be elucidated.

METHODS

Ragweed was grown in climate-controlled chambers under normal (380 ppm, control) or elevated (700 ppm, based on RCP4.5 scenario) CO₂ levels. Aqueous pollen extracts (RWE) from control- or CO₂ -pollen were administered in vivo in a mouse model for allergic disease (daily for 3-11 days, n = 5) and employed in human in vitro systems of nasal epithelial cells (HNECs), monocyte-derived dendritic cells (DCs), and HNEC-DC co-cultures. Additionally, adjuvant factors and metabolites in control- and CO₂ -RWE were investigated using ELISA and untargeted metabolomics.

RESULTS

In vivo, CO₂ -RWE induced stronger allergic lung inflammation compared to control-RWE, as indicated by lung inflammatory cell infiltrate and mediators, mucus hypersecretion, and serum total IgE. In vitro, HNECs stimulated with RWE increased indistinctively the production of pro-inflammatory cytokines (IL-8, IL-1β, and IL-6). In contrast, supernatants from CO₂ -RWE-stimulated HNECs, compared to control-RWE-stimulated HNECS, significantly increased TNF and decreased IL-10 production in DCs. Comparable results were obtained by stimulating DCs directly with RWEs. The metabolome analysis revealed differential expression of secondary plant metabolites in control- vs CO₂ -RWE. Mixes of these metabolites elicited similar responses in DCs as compared to respective RWEs.

CONCLUSION

Our results indicate that elevated ambient CO₂ levels elicit a stronger RWE-induced allergic response in vivo and in vitro and that RWE increased allergenicity depends on the interplay of multiple metabolites.

Multiple roles of Bet v 1 ligands in allergen stabilization and modulation of endosomal protease activity

Background

Over 100 million people worldwide suffer from birch pollen allergy. Bet v 1 has been identified as the major birch pollen allergen. However, the molecular mechanisms of birch allergic sensitization, including the roles of Bet v 1 and other components of the birch pollen extract, remain incompletely understood. Here, we examined how known birch pollen–derived molecules influence the endolysosomal processing of Bet v 1, thereby shaping its allergenicity.

Methods

We analyzed the biochemical and immunological interaction of ligands with Bet v 1. We then investigated the proteolytic processing of Bet v 1 by endosomal extracts in the presence and absence of ligands, followed by a detailed kinetic analysis of Bet v 1 processing by individual endolysosomal proteases as well as the T‐cell epitope presentation in BMDCs.

Results

We identified E₁ phytoprostanes as novel Bet v 1 ligands. Pollen‐derived ligands enhanced the proteolytic resistance of Bet v 1, affecting degradation kinetics and preferential cleavage sites of the endolysosomal proteases cathepsin S and legumain. E₁ phytoprostanes exhibited a dual role by stabilizing Bet v 1 and inhibiting cathepsin protease activity.

Conclusion

Bet v 1 can serve as a transporter of pollen‐derived, bioactive compounds. When carried to the endolysosome, such compounds can modulate the proteolytic activity, including its processing by cysteine cathepsins. We unveil a paradigm shift from an allergen‐centered view to a more systemic view that includes the host endolysosomal enzymes.

Ligand Binding of PR-10 Proteins with a Particular Focus on the Bet v 1 Allergen Family

PURPOSE OF REVIEW

Pathogenesis-related class 10 (PR-10) proteins are highly conserved plant proteins, which are induced in response to abiotic and biotic stress factors. To date, no unique biological function could be assigned to them. Rather a more general role of PR-10 in plant development and defense mechanisms has been proposed. In addition, some PR-10 proteins act as allergens by triggering allergic symptoms in sensitized individuals. Regardless of the diversity of reported activities, all PR-10 proteins share a common fold characterized by a solvent-accessible hydrophobic cavity, which serves as a binding site for a myriad of small-molecule ligands, mostly phytohormones and flavonoids.

RECENT FINDINGS

Most of available data relate to the ligand binding activity of allergenic PR-10, particularly for those belonging to Bet v 1 family of allergens. Bet v 1 and its homologues were shown to bind flavonoids with high affinity, but the specificity appears to differ between homologues from different species. The flavonoid Q3O-(Glc)-Gal was shown to specifically bind to hazelnut Cor a 1 but not to Bet v 1. Similarly, Q3OS bound only to the major isoform Bet v 1.0101 and not to other closely related isoforms. In contrast, Bet v 1 and hazelnut Cor a 1 showed very similar binding behavior towards other flavonoids such as quercetin, genistein, apigenin, daidzein, and resveratrol. Recent research findings highlighted the importance of more precise knowledge of ligand binding for understanding the functional diversification of PR-10 proteins.

Bet v 1--a Trojan horse for small ligands boosting allergic sensitization?

BACKGROUND

Birch pollen allergy represents the main cause of winter and spring pollinosis in the temperate climate zone of the northern hemisphere and sensitization towards Bet v 1, the major birch pollen allergen, affects over 100 million allergic patients. The major birch pollen allergen Bet v 1 has been described as promiscuous acceptor for a wide variety of hydrophobic ligands.

OBJECTIVE

In search of intrinsic properties of Bet v 1, which account responsible for the high allergenic potential of the protein, we thought to investigate the effects of ligand-binding on immunogenic as well as allergenic properties.

METHODS

As surrogate ligand of Bet v 1 sodium deoxycholate (DOC) was selected. Recombinant and natural Bet v 1 were characterised physico-chemically as well as immunologically in the presence or absence of DOC, and an animal model of allergic sensitization was established. Moreover, human IgE binding to Bet v 1 was analysed by nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

Ligand-binding had an overall stabilizing effect on Bet v 1. This translated in a Th2 skewing of the immune response in a mouse model. Analyses of human IgE binding on Bet v 1 in mediator release assays revealed that ligand-bound allergen-induced degranulation at lower concentrations; however, in basophil activation tests with human basophils ligand-binding did not show this effect. For the first time, human IgE epitopes on Bet v 1 were determined using antibodies isolated from patients' sera. The IgE epitope mapping of Bet v 1 demonstrated the presence of multiple binding regions.

CONCLUSIONS AND CLINICAL RELEVANCE

Deoxycholate binding stabilizes conformational IgE epitopes on Bet v 1; however, the epitopes themselves remain unaltered. Therefore, we speculate that humans are exposed to both ligand-bound and free Bet v 1 during sensitization, disclosing the ligand-binding cavity of the allergen as key structural element.

Initiating pollen sensitization - complex source, complex mechanisms

The mechanisms involved in the induction of allergic sensitization by pollen are not fully understood. Within the last few decades, findings from epidemiological and experimental studies support the notion that allergic sensitization is not only dependent on the genetics of the host and environmental factors, but also on intrinsic features of the allergenic source itself. In this review, we summarize the current concepts and newest advances in research focusing on the initial mechanisms inducing pollen sensitization. Pollen allergens are embedded in a complex and heterogeneous matrix composed of a myriad of bioactive molecules that are co-delivered during the allergic sensitization. Surprisingly, several purified allergens were shown to lack inherent sensitizing potential. Thus, growing evidence supports an essential role of pollen-derived components co-delivered with the allergens in the initiation of allergic sensitization. The pollen matrix, which is composed by intrinsic molecules (e.g. proteins, metabolites, lipids, carbohydrates) and extrinsic compounds (e.g. viruses, particles from air pollutants, pollen-linked microbiome), provide a specific context for the allergen and has been proposed as a determinant of Th2 polarization. In addition, the involvement of various pattern recognition receptors (PRRs), secreted alarmins, innate immune cells, and the dependency of DCs in driving pollen-induced Th2 inflammatory processes suggest that allergic sensitization to pollen most likely results from particular combinations of pollen-specific signals rather than from a common determinant of allergenicity. The exact identification and characterization of such pollen-derived Th2-polarizing molecules should provide mechanistic insights into Th2 polarization and pave the way for novel preventive and therapeutic strategies against pollen allergies.

Amb a 1 isoforms: Unequal siblings with distinct immunological features

Background

Ragweed pollen represents a major allergy risk factor. Ragweed extracts contain five different isoforms of the major allergen Amb a 1. However, the immunological characteristics of Amb a 1 isoforms are not fully investigated. Here, we compared the physicochemical and immunological properties of three most important Amb a 1 isoforms.

Methods

After purification, the isoforms were physicochemically characterized, tested for antibody binding and induction of human T‐cell proliferative responses. Their immunological properties were further evaluated in vitro and in vivo in a mouse model.

Results

Amb a 1 isoforms exhibited distinct patterns of IgE binding and immunogenicity. Compared to Amb a 1.02 or 03 isoforms, Amb a 1.01 showed higher IgE‐binding activity. Isoforms 01 and 03 were the most potent stimulators of patients’ T cells. In a mouse model of immunization, Amb a 1.01 induced higher levels of IgG and IgE antibodies when compared to isoforms 02 and 03. Interestingly, ragweed‐sensitized patients also displayed an IgG response to Amb a 1 isoforms. However, unlike therapy‐induced antibodies, sensitization‐induced IgG did not show IgE‐blocking activity.

Conclusion

The present study showed that naturally occurring isoforms of Amb a 1 possess different immunogenic and sensitizing properties. These findings should be considered when selecting sequences for molecule‐based diagnosis and therapy for ragweed allergy. Due to its high IgE‐binding activity, isoform Amb a 1.01 should be included in diagnostic tests. In contrast, due to their limited B‐ and T‐cell cross‐reactivity patterns, a combination of different isoforms might be a more attractive strategy for ragweed immunotherapy.

IgE-cross-blocking antibodies to Fagales following sublingual immunotherapy with recombinant Bet v 1

BACKGROUND

Evidence has accumulated that birch pollen immunotherapy reduces rhinoconjunctivitis to pollen of birch homologous trees. Therapeutic efficacy has been associated with IgE-blocking IgG antibodies. We have recently shown that sera collected after 16 weeks of sublingual immunotherapy with recombinant Bet v 1 (rBet v 1-SLIT) display strong IgE-blocking bioactivity for Bet v 1. Here, we assessed whether rBet v 1-SLIT-induced IgG antibodies display cross-blocking activity to related allergens in Fagales pollen.

METHODS

IgE, IgG1 and IgG4 reactivity to recombinant Bet v 1, Aln g 1, Car b 1, Ost c 1, Cor a 1, Fag s 1, Cas s 1 and Que a 1 were assessed in pre- and post-SLIT samples of 17 individuals by ELISA. A basophil inhibition assay using stripped basophils re-sensitized with a serum pool containing high Bet v 1-specific IgE levels was established and used to assess CD63 expression in response to allergens after incubation with pre-SLIT or post-SLIT samples. IgG1 and IgG4 were depleted from post-SLIT samples to assess its contribution to IgE-cross-blocking.

RESULTS

Sublingual immunotherapy with recombinant Bet v 1 boosted cross-reactive IgE antibodies and induced IgG1 and IgG4 antibodies with inter- and intra-individually differing reactivity to the homologs. Highly variable cross-blocking activities of post-SLIT samples to the different allergens were found. IgG1 and IgG4 antibodies displayed cross-blocking activity with individual variance.

CONCLUSIONS

Our mechanistic approach suggested that immunotherapy with the reference allergen Bet v 1 induces individual repertoires of cross-reactive IgG1 and IgG4 antibodies. The cross-blocking bioactivity of these antibodies was also highly variable and neither predictable from protein homology nor IgE-cross-reactivity.

Context matters: TH2 polarization resulting from pollen composition and not from protein-intrinsic allergenicity

Background

Over 100 million people worldwide suffer from birch pollen allergy. However, identification of molecular determinants driving Th2-biased allergic sensitization to Bet v 1, the major birch pollen allergen, remains elusive.

Objective

Here, we examined whether Bet v 1 or the pollen matrix is responsible for activation of antigen-presenting cells and the subsequent Th2 polarization, relevant in the process of allergic sensitization.

Methods

The allergenicity of Bet v 1 and of birch pollen extract (BPE) was addressed by stimulation of murine and human dendritic cells and by in vivo monitoring of Th2 polarization. Further, Bet v 1 was depleted from BPE by immunoprecipitation in order to analyze its involvement in the occurrence of a Th2 response.

Results

The allergen alone did neither stimulate dendritic cells in vitro nor induced Th2 polarization in vivo, even in the presence of the natural LPS concentration determined in the BPE. In contrast, BPE was shown to activate dendritic cells and strongly promoted a Th2 polarization. Even upon immunization with Bet v 1-depleted BPE the amount of induced Th2 cells remained unaltered.

Conclusion

This finding indicates that the Th2-polarizing potential of BPE is Bet v 1 independent; therefore, sensitization to Bet v 1 is induced by an as-yet-undetermined pollen compound or mechanism in the pollen environment. These data suggest that sensitization is not exclusively linked to the intrinsic properties of individual proteins. These findings are relevant in understanding allergic sensitization towards pollen allergens and might pave the way for future prophylactic approaches.

TGFβ1 mimetic peptide modulates immune response to grass pollen allergens in mice

BACKGROUND

Transforming growth factor β1 (TGFβ1) is a cytokine that exerts immunosuppressive functions, as reflected by its ability to induce regulatory T (Treg) cell differentiation and inhibit Th1 and Th2 responses. Hence, peptides that mimic the active core domain of TGFβ1 may be promising candidates for modulation of the allergic response. This study aimed to investigate a synthetic TGFβ1 mimetic peptide (TGFβ1-mim) for its ability to modulate the immune response during allergic sensitization to grass pollen allergens.

METHODS

The in vitro action of TGFβ1-mim was evaluated in human lung epithelial cells, Jurkat cells, and rat basophilic leukemia cells. The in vivo action was evaluated in a murine model of Phl p 5 allergic sensitization. Additionally, the Th2 modulatory response was evaluated in IL-4 reporter mice.

RESULTS

In vitro, TGFβ1-mim downregulated TNF-α production, IL-8 gene expression, and cytokine secretion, upregulated IL-10 secretion, and inhibited Phl p 5-induced basophil degranulation. During Phl p 5 sensitization in mice, TGFβ1-mim downregulated IL-2, IL-4, IL-5, IL-13, and IFN-γ, upregulated IL-10, and induced Treg cell production. Furthermore, mice treated with TGFβ1-mim had lower levels of IgE, IgG1, IgG2a and higher levels of IgA antibodies than control mice. In a reporter mouse, the mimetic inhibited Th2 polarization.

CONCLUSION

The TGFβ1-mim efficiently modulated various important events that exacerbate the allergic microenvironment, including the production of main cytokines that promote Th1 and Th2 differentiation, and the induction of allergen-specific regulatory T cells, highlighting its potential use in therapeutic approaches to modulate the immune response toward environmental allergens.

A hybrid of two major Blomia tropicalis allergens as an allergy vaccine candidate

Introduction

Allergen‐specific immunotherapy (AIT) represents a curative approach for treating allergies. In the tropical and subtropical regions of the world, Blomia tropicalis (Blo t 5 and Blo t 21) is the likely dominant source of indoor allergens.

Aim

To generate a hypoallergenic Blo t 5/Blo t 21 hybrid molecule that can treat allergies caused by B tropicalis.

Methods

Using in silico design of B tropicalis hybrid proteins, we chose two hybrid proteins for heterologous expression. Wild‐type Blo t 5/Blo t 21 hybrid molecule and a hypoallergenic version, termed BTH1 and BTH2, respectively, were purified by ion exchange and size exclusion chromatography and characterized by physicochemical, as well as in vitro and in vivo immunological, experiments.

Results

BTH1, BTH2 and the parental allergens were purified to homogeneity and characterized in detail. BTH2 displayed the lowest IgE reactivity that induced basophil degranulation using sera from allergic rhinitis and asthmatic patients. BTH2 essentially presented the same endolysosomal degradation pattern as the shortened rBlo t 5 and showed a higher resistance towards degradation than the full‐length Blo t 5. In vivo immunization of mice with BTH2 led to the production of IgG antibodies that competed with human IgE for allergen binding. Stimulation of splenocytes from BTH2‐immunized mice produced higher levels of IL‐10 and decreased secretion of IL‐4 and IL‐5. In addition, BTH2 stimulated T‐cell proliferation in PBMCs isolated from allergic patients, with secretion of higher levels of IL‐10 and lower levels of IL‐5 and IL‐13, when compared to parental allergens.

Conclusions and Clinical Relevance

BTH2 is a promising hybrid vaccine candidate for immunotherapy of Blomia allergy. However, further pre‐clinical studies addressing its efficacy and safety are needed.

Two Distinct Conformations in Bet v 2 Determine Its Proteolytic Resistance to Cathepsin S

Birch pollen allergy affects more than 20% of the European allergic population. On a molecular level, birch pollen allergy can be linked to the two dominant allergens Bet v 1 and Bet v 2. Bet v 2 belongs to the profilin family, which is abundant in the plant kingdom. Importantly, the homologous plant profilins have a conserved cysteine motif with a currently unknown functional relevance. In particular, it is unknown whether the motif is relevant for disulfide formation and to what extent it would affect the profilins’ structural, functional and immunological properties. Here we present crystal structures of Bet v 2 in the reduced and the oxidized state, i.e., without and with a disulfide bridge. Despite overall structural similarity, the two structures distinctly differ at their termini which are stabilized to each other in the oxidized, i.e., disulfide-linked state. These structural differences translate into differences in their proteolytic resistance. Whereas the oxidized Bet v 2 is rather resistant towards the endolysosomal protease cathepsin S, it is rapidly degraded in the reduced form. By contrast, both Bet v 2 forms exhibit similar immunological properties as evidenced by their binding to IgE antibodies from birch pollen allergic patients and by their ability to trigger histamine release in a humanized rat basophilic leukemia cells (RBL) assay, independent of the presence or absence of the disulfide bridge. Taken together our findings suggest that the oxidized Bet v 2 conformation should be the relevant species, with a much longer retention time to trigger immune responses.

In vivo Induction of Functional Inhibitory IgG Antibodies by a Hypoallergenic Bet v 1 Variant

Allergic sensitization to the major allergen Bet v 1 represents the dominating factor inducing a vast variety of allergic symptoms in birch pollen allergic patients worldwide, including the pollen food allergy syndrome. In order to overcome the huge socio-economic burden associated with allergic diseases, allergen-specific immunotherapy (AIT) as a curative strategy to manage the disease was introduced. Still, many hurdles related to this treatment exist making AIT not the patients’ first choice. To improve the current situation, the development of hypoallergen-based drug products has raised attention in the last decade. Herein, we investigated the efficacy of the novel AIT candidate BM4, a hypoallergenic variant of Bet v 1, to induce treatment-relevant cross-reactive Bet v 1-specific IgG antibodies in two different mammals, Wistar rats and New Zealand White rabbits. We further analyzed the cross-reactivity of BM4-induced Wistar rat antibodies with the birch pollen-associated food allergens Mal d 1 and Cor a 1, and the functional capability of the induced antibodies to act as IgE-blocking IgG antibodies. Enzyme-linked immunosorbent assay (ELISA) was used to determine the titers of rat IgG1, IgG2a, IgG2b, and IgE, as well as rabbit IgG and IgE antibodies. To address the functional relevance of the induced IgG antibodies, the capacity of rat sera to suppress binding of human IgE to Bet v 1 was investigated by using an inhibition ELISA and an IgE-facilitated allergen-binding inhibition assay. We found that the treatment with BM4 induced elevated Bet v 1-specific IgG antibody titers in both mammalian species. In Wistar rats, high BM4-specific IgG1, IgG2a, and IgG2b titers (10⁴ to 10⁶) were induced, which cross-reacted with wild-type Bet v 1, and the homologous allergens Mal d 1 and Cor a 1. Rat allergen-specific IgG antibodies sustained upon treatment discontinuation. Sera of rats immunized with BM4 were able to significantly suppress binding of human IgE to the wild-type allergens and CD23-mediated human IgE-facilitated Bet v 1 binding on B cells. By contrast, treatment-induced IgE antibody levels were low or undetectable. In summary, BM4 induced a robust IgG immune response that efficiently blocked human IgE-binding to wild-type allergens, underscoring its potential therapeutic value in AIT.

Effectiveness of Grounded Sleeping on Recovery After Intensive Eccentric Muscle Loading

Purpose: We set out to investigate the effectiveness of grounded sleeping on the time course of recovery with respect to muscle soreness and athletic performance after intensive eccentric muscle loading. Methods: Twenty-two healthy participants were recruited for this study and randomly assigned to an experimental group (GRD, grounded sleeping, n = 12) or control group (UGD, sham-grounded sleeping, n = 10) to evaluate the effects of 10 days recovery with GRD vs. UGD following a single intensive downhill treadmill intervention in a triple-blinded (participant, tester, and data analyst) manner. To operationalize recovery a test battery was performed at baseline and on days 1, 2, 3, 5, 7, and 10 post-intervention: (1) perception of muscle soreness (VAS), (2) creatine kinase blood levels (CK), (3) maximum voluntary isometric contraction (MVIC) for both legs, (4) counter movement jump (CMJ) and drop jump (DJ) performance. Furthermore, in four participants blood was sampled for detailed analysis of complete blood counts and serum-derived inflammation markers. Results: The downhill treadmill running intervention led to distinct changes in all measured parameters related to fatigue. These changes were detectable already 5-min post intervention and were not fully recovered 10 days post intervention. GRD led to less pronounced decrease in performance (CMJ, MVIC) and less increase with respect to CK compared with UGD (all P < 0.05). Detailed blood samples demonstrated that grounded sleeping modulates the recovery process by (a) keeping a constant hemoconcentration, as represented by the number of erythrocytes, and the hemoglobin/hematocrit values; and (b) by the reduction of muscle damage-associated inflammation markers such as, IP-10, MIP-1α, and sP-Selectin. Conclusion: The downhill running protocol is a feasible methodology to produce long term muscle soreness and muscular fatigue. GRD was shown to result in faster recovery and/or less pronounced markers of muscle damage and inflammation. GRD might be seen as a simple methodology to enhance acute and long-term recovery after intensive eccentric exercises.

Identification and Physicochemical Characterization of a New Allergen from Ascaris lumbricoides

To analyze the impact of Ascaris lumbricoides infection on the pathogenesis and diagnosis of allergic diseases, new allergens should be identified. We report the identification of a new Ascaris lumbricoides allergen, Asc l 5. The aim of this study was to evaluate the physicochemical and immunological features of the Asc l 5 allergen. We constructed an A. lumbricoides cDNA library and Asc l 5 was identified by immunoscreening. After purification, rAsc l 5 was physicochemically characterized. Evaluation of its allergenic activity included determination of Immunoglobulin E (IgE) binding frequency (in two populations: 254 children and 298 all-age subjects), CD203c based-basophil activation tests (BAT) and a passive cutaneous anaphylaxis (PCA) mouse model. We found by amino acid sequence analysis that Asc l 5 belongs to the SXP/RAL-2 protein family of nematodes. rAsc l 5 is a monomeric protein with an alpha-helical folding. IgE sensitization to rAsc l 5 was around 52% in general population; positive BAT rate was 60%. rAsc l 5 induced specific IgE production in mice and a positive PCA reaction. These results show that Asc l 5 has structural and immunological characteristics to be considered as a new allergen from A. lumbricoides.

Bet v 1-displaying elastin-like polypeptide nanoparticles induce a strong humoral and weak CD4+ T-cell response against Bet v 1 in a murine immunogenicity model

There is growing concern about the toxicity of colloidal aluminum salts used as adjuvants in subcutaneous allergen immunotherapy (SCIT). Therefore, alternative adjuvants and delivery systems are being explored to replace alum in SCIT. We applied micellar elastin-like polypeptides (ELPs), a type of self-assembling protein, to replace alum as vaccine adjuvant in birch pollen SCIT. ELP and an ELP-Bet v 1 fusion protein were expressed in E. coli and purified by immuno-affinity chromatography and inverse-transition cycling (ITC). Nanoparticles self-assembled from ELP and a 9:1 ELP/ELP-Bet v 1 mixture were characterized by using dynamic light scattering and atomic force microscopy. Allergenicity was assessed by measuring mediator release from rat basophilic leukemia cells transformed with the human FcϵR1 and sensitized with sera derived from human birch pollen allergic patients. Humoral and T-cell immunity were investigated by immunizing naïve mice with the ELP/ELP-Bet v 1 nanoparticles or alum-adsorbed Bet v 1, both containing 36 µg Bet v 1. ELP and ELP/ELP-Bet v 1 self-assembled at 37°C into spherically shaped micelles with a diameter of ~45 nm. ELP conjugation made Bet v 1 hypo-allergenic (10-fold). Compared to alum-adsorbed Bet v 1, ELP/ELP-Bet v 1 nanoparticles induced stronger IgG responses with an earlier onset. Additionally, ELP/ELP-Bet v 1 did not induce Th2 skewing cytokines and IgE. The hypoallergenic character and strong humoral immune response in the absence of a Th2-skewing T-cell response make ELP-based nanoparticles a promising candidate to replace alum in SCIT.

Unique allergen-specific human IgE monoclonal antibodies derived from patients with allergic disease

Introduction

Allergic reactions are mediated by human IgE antibodies that bind to and cross-link allergen molecules. The sites on allergens that are recognized by IgE antibodies have been difficult to investigate because of the paucity of IgE antibodies in a human serum. Here, we report the production of unique human IgE monoclonal antibodies to major inhaled allergens and food allergens that can be produced at scale in perpetuity.

Materials and methods

The IgE antibodies were derived from peripheral blood mononuclear cells of symptomatic allergic patients, mostly children aged 3-18 years, using hybridoma fusion technology. Total IgE and allergen-specific IgE was measured by ImmunoCAP. Their specificity was confirmed through ELISA and immunoblotting. Allergenic potency measurements were determined by ImmunoCAP inhibition. Biological activity was determined in vitro by comparing β-hexosaminidase release from a humanized rat basophilic cell line.

Results

Human IgE monoclonal antibodies (n = 33) were derived from 17 allergic patients with symptoms of allergic rhinitis, asthma, atopic dermatitis, food allergy, eosinophilic esophagitis, or red meat allergy. The antibodies were specific for five inhaled allergens, nine food allergens, and alpha-gal and had high levels of IgE (53,450-1,702,500 kU/L) with ratios of specific IgE to total IgE ranging from <0.01 to 1.39. Sigmoidal allergen binding curves were obtained through ELISA, with low limits of detection (<1 kU/L). Allergen specificity was confirmed through immunoblotting. Pairs of IgE monoclonal antibodies to Ara h 6 were identified that cross-linked after allergen stimulation and induced release of significant levels of β-hexosaminidase (35%-80%) from a humanized rat basophilic cell line.

Conclusions

Human IgE monoclonal antibodies are unique antibody molecules with potential applications in allergy diagnosis, allergen standardization, and identification of allergenic epitopes for the development of allergy therapeutics. The IgE antibody probes will enable the unequivocal localization and validation of allergenic epitopes.

Cationic liposomes bearing Bet v 1 by coiled coil-formation are hypo-allergenic and induce strong immunogenicity in mice

Although aluminum hydroxide (alum) is widely accepted and used as safe vaccine adjuvant, there is some concern about possible toxicity upon long-lasting repeated exposure during subcutaneous allergen immunotherapy (SCIT). Our objective was to evaluate allergen-bearing liposomes as possible alternative for alum-adsorption in SCIT. A self-assembling, coiled-coil forming peptide pair was used to anchor the major birch pollen allergen Bet v 1 to the surface of cationic liposomes. The resulting nanoparticulate liposomes were characterized with respect to their physicochemical, allergenic and immunological properties. Allergenicity was studied by ImmunoCAP inhibition and rat basophil leukemia (RBL) cell assays. Immunogenicity (immunoglobulin responses) and immune skewing (cytokine responses) were evaluated upon immunization of naïve mice, and compared to alum-adsorbed Bet v 1. Bet v 1-bearing cationic liposomes with a diameter of ∼200 nm showed a positive zeta potential. The coiled-coil conjugation of Bet v 1 to the surface of liposomes resulted in about a 15-fold lower allergenicity than soluble Bet v 1 as judged by RBL assays. Moreover, the nanoparticles induced Bet v 1-specific IgG1/IgG2a responses in mice that were several orders of magnitude higher than those induced by alum-adsorbed Bet v 1. This strong humoral response was accompanied by a relatively strong IL-10 induction upon PBMC stimulation with Bet v 1. In conclusion, their hypo-allergenic properties, combined with their capacity to induce a strong humoral immune response and a relatively strong IL-10 production, makes these allergen-covered cationic liposomes a promising alternative for aluminum salt-adsorption of allergen currently used in SCIT.

Bet v 1-independent sensitization to major allergens in Fagales pollen: Evidence at the T-cell level

BACKGROUND

In birch-dominated areas, allergies to pollen from trees of the order Fagales are considered to be initiated by the major birch pollen allergen Bet v 1. However, the sensitizing activity of Bet v 1-homologs in Fagales pollen might be underestimated. Allergen-specific T-cells are crucial in the sensitization process. The T-cell response to major allergens from alder, hazel, oak, hornbeam, chestnut, beech, and chestnut pollen has not yet been analyzed. Here, we characterized the cellular cross-reactivity of major allergens in Fagales pollen with Bet v 1.

METHODS

T-cell-lines (TCL) were established from allergic individuals with Aln g 1, Car b 1, Ost c 1, Cor a 1, Fag s 1, Cas s 1, and Que a 1, and tested for reactivity with Bet v 1 and synthetic overlapping 12-mer peptides representing its primary sequence. Aln g 1-specific TCL was additionally tested with Aln g 1-derived peptides and all allergens. IgE-competition experiments with Aln g 1 and Bet v 1 were performed.

RESULTS

T-cell-lines initiated with Fagales pollen allergens varied strongly in their reactivity with Bet v 1 and by the majority responded stronger to the original stimulus. Cross-reactivity was mostly restricted to the epitope Bet v 1142-153 . No distinct cross-reactivity of Aln g 1-specific T-cells with Bet v 1 was detected. Among 22 T-cell epitopes, Aln g 1 contained two immunodominant epitopes. Bet v 1 inhibited IgE-binding to Aln g 1 less potently than Aln g 1 itself.

CONCLUSION

The cellular cross-reactivity of major Fagales pollen allergens with Bet v 1 was unincisive, particularly for Aln g 1, most akin to Bet v 1. Our results indicate that humoral and cellular responses to these allergens are not predominantly based on cross-reactivity with the major birch pollen allergen but suggest a Bet v 1-independent sensitization in individuals from birch tree-dominated areas.