Allergen-Specific Antibodies Regulate Secondary Allergen-Specific Immune Responses

Outdoor airborne allergens: Characterization, behavior and monitoring in Europe

Aeroallergens or inhalant allergens, are proteins dispersed through the air and have the potential to induce allergic conditions such as rhinitis, conjunctivitis, and asthma. Outdoor aeroallergens are found predominantly in pollen grains and fungal spores, which are allergen carriers. Aeroallergens from pollen and fungi have seasonal emission patterns that correlate with plant pollination and fungal sporulation and are strongly associated with atmospheric weather conditions. They are released when allergen carriers come in contact with the respiratory system, e.g. the nasal mucosa. In addition, due to the rupture of allergen carriers, airborne allergen molecules may be released directly into the air in the form of micronic and submicronic particles (cytoplasmic debris, cell wall fragments, droplets etc.) or adhered onto other airborne particulate matter. Therefore, aeroallergen detection strategies must consider, in addition to the allergen carriers, the allergen molecules themselves. This review article aims to present the current knowledge on inhalant allergens in the outdoor environment, their structure, localization, and factors affecting their production, transformation, release or degradation. In addition, methods for collecting and quantifying aeroallergens are listed and thoroughly discussed. Finally, the knowledge gaps, challenges and implications associated with aeroallergen analysis are described.

Natural human Bet v 1-specific IgG antibodies recognize non-conformational epitopes whereas IgE reacts with conformational epitopes

BACKGROUND

The nature of epitopes on Bet v 1 recognized by natural IgG antibodies of birch pollen allergic patients and birch pollen-exposed but non-sensitized subjects has not been studied in detail.

OBJECTIVE

To investigate IgE and IgG recognition of Bet v 1 and to study the effects of natural Bet v 1-specific IgG antibodies on IgE recognition of Bet v 1 and Bet v 1-induced basophil activation.

METHODS

Sera from birch pollen allergic patients (BPA, n = 76), allergic patients without birch pollen allergy (NBPA, n = 40) and non-allergic individuals (NA, n = 48) were tested for IgE, IgG as well as IgG1 and IgG4 reactivity to folded recombinant Bet v 1, two unfolded recombinant Bet v 1 fragments comprising the N-terminal (F1) and C-terminal half of Bet v 1 (F2) and unfolded peptides spanning the corresponding sequences of Bet v 1 and the apple allergen Mal d 1 by ELISA or micro-array analysis. The ability of Bet v 1-specific serum antibodies from non-allergic subjects to inhibit allergic patients IgE or IgG binding to rBet v 1 or to unfolded Bet v 1-derivatives was assessed by competition ELISAs. Furthermore, the ability of serum antibodies from allergic and non-allergic subjects to modulate Bet v 1-induced basophil activation was investigated using rat basophilic leukaemia cells expressing the human FcεRI which had been loaded with IgE from BPA patients.

RESULTS

IgE antibodies from BPA patients react almost exclusively with conformational epitopes whereas IgG, IgG1 and IgG4 antibodies from BPA, NBPA and NA subjects recognize mainly unfolded and sequential epitopes. IgG competition studies show that IgG specific for unfolded/sequential Bet v 1 epitopes is not inhibited by folded Bet v 1 and hence the latter seem to represent cryptic epitopes. IgG reactivity to Bet v 1 peptides did not correlate with IgG reactivity to the corresponding Mal d 1 peptides and therefore does not seem to be a result of primary sensitization to PR10 allergen-containing food. Natural Bet v 1-specific IgG antibodies inhibited IgE binding to Bet v 1 only poorly and could even enhance Bet v 1-specific basophil activation.

CONCLUSION

IgE and IgG antibodies from BPA patients and birch pollen-exposed non-sensitized subjects recognize different epitopes. These findings explain why natural allergen-specific IgG do not protect against allergic symptoms and suggest that allergen-specific IgE and IgG have different clonal origin.

Omalizumab for the treatment of patients with severe allergic asthma with immunoglobulin E levels above >1500 IU/mL

Immunoglobulin E (IgE) plays a critical role in the allergen-initiated inflammatory pathway and thus serves as a viable therapeutic target in allergic or IgE-mediated diseases such as asthma. Omalizumab, an anti-IgE biologic, has been approved in the United States (US, 2003) and in the European Union (EU, 2005) as an add-on therapy in patients with moderate-to-severe persistent asthma and severe allergic asthma (SAA) aged 6 years and older. The dose and frequency of omalizumab are adjusted based on the patient's body weight and baseline IgE levels, as recommended by its dosing tables. Currently, these dosing recommendations are limited to patients with baseline IgE levels of up to 1500 IU/mL in the European Union and 700 IU/mL in the United States. However, many patients with SAA have IgE levels >1500 IU/mL, highlighting an unmet need. This review presents the current evidence on the treatment benefits of omalizumab in patients with IgE levels >1500 IU/mL. The findings from the reviewed studies which included >3000 patients support the efficacy and effectiveness of omalizumab in reducing exacerbations, and improving asthma control, lung function, and quality of life in patients with severe asthma having IgE levels beyond the current dosing range. Omalizumab was well-tolerated in these patients, with no new safety signals. In addition, high IgE levels (>1500 IU/mL) are also reported in several comorbidities of asthma (allergic rhinitis, atopic dermatitis, allergic bronchopulmonary aspergillosis [ABPA], food allergy, and nasal polyposis) and omalizumab has demonstrated efficacy and safety in these indications. These data suggest that omalizumab may be considered for administration in SAA patients, with high IgE levels outside the current dosing tables. A detailed assessment of patients with high IgE levels is needed before deciding on the optimal treatment approach. A management algorithm for SAA patients with IgE >1500 IU/mL is proposed in this review and a suggestion to follow the Delphi consensus is advised.

Autophagy-related tumor subtypes associated with significant gene expression profiles and immune cell infiltration signatures to reveal the prognosis of non-small cell lung cancer

Autophagy plays an important role in non-small cell lung cancer (NSCLC). We aimed to establish novel autophagy-related tumor subtypes to distinguish the prognosis of NSCLC. In this study, gene expression profiles, mutation data and clinical information obtained from the Cancer Genome Atlas. Kaplan Meier-plotter could evaluate prognostic value of autophagy-related genes. Consensus clustering revealed autophagy-related tumor subtypes. Gene expression profiles, mutation data and immune infiltration signatures were identified, oncogenic pathways and gene-drug interactions were performed according to the clusters. Finally, a total of 23 prognostic genes were screened and consensus clustering analysis divided the NSCLC into 2 clusters. The mutation signature showed that 6 genes are special. Immune infiltration signatures showed that higher fraction of immune cells was associated with cluster 1. The oncogenic pathways and gene-drug interactions also showed different patterns. In conclusion, autophagy-related tumor subtypes have different prognosis. Understanding the subtypes of NSCLC are helpful to accurately identify the NSCLC and personalized treatment.

Allergen immunotherapy: progress and future outlook

INTRODUCTION

Allergy, the immunological hypersensitivity to innocuous environmental compounds, is a global health problem. The disease triggers, allergens, are mostly proteins contained in various natural sources such as plant pollen, animal dander, dust mites, foods, fungi and insect venoms. Allergies can manifest with a wide range of symptoms in various organs, and be anything from just tedious to life-threatening. A majority of all allergy patients are self-treated with symptom-relieving medicines, while allergen immunotherapy (AIT) is the only causative treatment option.

AREAS COVERED

This review will aim to give an overview of the state-of-the-art allergy management, including the use of new biologics and the application of biomarkers, and a special emphasis and discussion on current research trends in the field of AIT.

EXPERT OPINION

Conventional AIT has proven effective, but the years-long treatment compromises patient compliance. Moreover, AIT is typically not offered in food allergy. Hence, there is a need for new, effective and safe AIT methods. Novel routes of administration (e.g. oral and intralymphatic), hypoallergenic AIT products and more effective adjuvants holds great promise. Most recently, the development of allergen-specific monoclonal antibodies for passive immunotherapy may also allow treatment of patients currently not treated or treatable.

Tracking a Major Egg Allergen to Assess Commercial Food Label Compliance: Towards a Simple and Fast Immunosensing Device

An amperometric immunosensor was developed for the analysis of the major egg-white allergen ovotransferrin (Gal d 3) in commercial food products because the (accidental) intake, skin contact with, and/or inhalation of eggs can lead to severe disorders in allergic individuals. Employing a sandwich-type immunosensing strategy, screen-printed carbon electrodes (SPCE) were biomodified with anti-Gal d 3 (capture) antibodies, and the allergen’s detection was achieved with anti-Gal d 3 antibodies labelled with horseradish peroxidase (HRP). The 3,3′,5,5′-tetramethylbenzidine (TMB)/H2O2 reaction with HRP was used to obtain the electrochemical (amperometric) signal. An attractive assay time of 30 min and a remarkable analytical performance was achieved. The quantification range was established between 55 and 1000 ng·mL−1, with a limit of detection of 16 ng·mL−1. The developed method demonstrated good precision (Vx0 = 5.5%) and provided precise results (CV < 6%). The sensor also detected extremely low amounts (down to 0.010%) of egg. The analysis of seven raw and/or cooked egg and egg-white samples indicated that food processing influences the amount of allergen. Furthermore, to assure the compliance of product labelling with EU legislation, 25 commercial food ingredients/products were analysed. The accuracy of the results was confirmed through an ELISA assay. The stability of the ready-to-use sensing surface for 20 days allows a reduction of the reagents’ volumes and cost.

Elevation of IgE in patients with psoriasis: Is it a paradoxical phenomenon?

Immunoglobulin E (IgE) elevation is a hallmark of allergic conditions such as atopic dermatitis (AD). The pathogenesis of AD is typically associated with high levels of IL-4 and IL-13 produced by activated T helper 2 (Th2) cells. Psoriasis, on the other hand, is an inflammatory skin disease mainly driven by Th17 cells and their related cytokines. Although the immunopathologic reactions and clinical manifestations are often easily distinguished in the two skin conditions, patients with psoriasis may sometimes exhibit AD-like manifestations, such as elevated IgE and persistent pruritic lesions. Given the fact that the effective T cells have great plasticity to re-differentiate in response to innate and environmental factors, this unusual skin condition could be a consequence of a cross-reaction between distinct arms of T-cell and humoral immunity. Here we review the literature concerning the roles of IgE in the development of AD and psoriasis, showing that elevated IgE seems to be an important indicator for this non-typical psoriasis.

Blocking function of allergen-specific immunoglobulin G, F(ab')2, and Fab antibodies prepared from patients undergoing Dermatophagoides pteronyssinus immunotherapy

BACKGROUND

The blocking function of allergen-specific F(ab')₂ [sF(ab')₂] and Fab (sFab) fragment antibodies prepared from allergen immunotherapy-induced specific immunoglobulin G (sIgG) has not been fully investigated.

OBJECTIVE

To investigate the inhibitory function of sIgG, sF(ab')₂, and sFab antibodies in patients undergoing Dermatophagoides pteronyssinus (Der-p) subcutaneous immunotherapy (SCIT).

METHODS

This study involved 10 subjects (aged 18-42 years) with house dust mite allergic rhinitis or asthma who received a 156-week course of Der-p SCIT. Total IgG levels were purified from the serum of the participants at weeks 0 and 156 by protein A affinity chromatography. Der-p sIgG was purified by affinity chromatography with Der-p as a ligand at week 156. The sF(ab')₂ and sFab antibodies were prepared from Der-p sIgG by treatment with pepsin and papain, respectively. Furthermore, IgE-facilitated allergen binding assay, basophil activation inhibition test, and cytokine release inhibition assay were used to assess the inhibitory function of Der-p sIgG, sF(ab')₂, and sFab antibodies.

RESULTS

We found that the Der-p sIgG, sF(ab')₂, and sFab antibodies markedly blocked Der-p-allergen sIgE complex binding to B cells, inhibited basophil activation, and markedly reduced the production of interleukin (IL)-5, IL-13, IL-17, and tumor necrosis factor-α by peripheral blood mononuclear cells.

CONCLUSION

SCIT-induced Der-p sIgG, sF(ab')₂, and sFab antibodies may block the formation of Der-p-sIgE complexes and may serve as a potential allergen-targeted biologics candidate for the treatment of allergic asthma.

CLINICAL TRIAL REGISTRATION

This study was approved by the Ethics Committee of the First Affiliated Hospital of Guangzhou Medical University and registered in the Chinese Clinical Trial Registry (ChiCTR-OOC-15006207, https://www.chictr.org.cn/enindex.aspx).

The Effector Function of Allergens

Allergens are antigens that generate an IgE response (sensitization) in susceptible individuals. The allergenicity of an allergen can be thought of in terms of its ability to sensitize as well as its ability to cross-link IgE/IgE receptor complexes on mast cells and basophils leading to release of preformed and newly formed mediators (effector activity). The identity of the allergens responsible for sensitization may be different from those that elicit an allergic response. Effector activity is determined by (1) the amount of specific IgE (sIgE) and in some circumstances the ratio of sIgE to total IgE, (2) the number of high affinity receptors for IgE (FcεR1) on the cell surface, (3) the affinity of binding of sIgE for its epitope and, in a polyclonal response, the collective avidity, (4) the number and spatial relationships of IgE binding epitopes on the allergen and (5) the presence of IgG that can bind to allergen and either block binding of sIgE and/or activate low affinity IgG receptors that activate intracellular inhibitory pathways. This review will discuss these important immunologic and physical properties that contribute to the effector activity of allergens.

First clinical expression of equine insect bite hypersensitivity is associated with co-sensitization to multiple Culicoides allergens

BACKGROUND

Insect bite hypersensitivity (IBH) is an IgE-mediated allergic dermatitis in horses incited by salivary allergens from Culicoides spp. IBH does not occur in Iceland, as the causative agents are absent, however a high prevalence is seen in horses exported to Culicoides-rich environments.

AIMS

To study the natural course of sensitization to Culicoides allergens and identify the primary sensitizing allergen(s) in horses exported from Iceland utilizing a comprehensive panel of Culicoides recombinant (r-) allergens.

METHOD

IgE microarray profiling to 27 Culicoides r-allergens was conducted on 110 serological samples from horses imported to Switzerland from Iceland that subsequently developed IBH or remained healthy. Furthermore, a longitudinal study of 31 IBH horses determined IgE profiles the summer preceding first clinical signs of IBH (TIBH-1), the summer of first clinical signs (TIBH) and the following summer (TIBH+1). In a group of Icelandic horses residing in Sweden, effects of origin (born in Iceland or Sweden) and duration of IBH (<4 years, 4-7 years, >7 years) on Culicoides-specific IgE was evaluated. Sero-positivity rates and IgE levels were compared.

RESULTS

At TIBH, horses were sensitized to a median of 11 r-allergens (range = 0-21), of which nine were major allergens. This was significantly higher than TIBH-1 (3, 0-16), as well as the healthy (1, 0-14) group. There was no significant increase between TIBH and TIBH+1(12, 0-23). IBH-affected horses exported from Iceland had a significantly higher degree of sensitization than those born in Europe, while duration of IBH did not significantly affect degree of sensitization.

CONCLUSION

Significant sensitization is only detected in serum the year of first clinical signs of IBH. Horses become sensitized simultaneously to multiple Culicoides r-allergens, indicating that IgE-reactivity is due to co-sensitization rather than cross-reactivity between Culicoides allergens. Nine major first sensitizing r-allergens have been identified, which could be used for preventive allergen immunotherapy.

Peptide Allergen Immunotherapy: A New Perspective in Olive-Pollen Allergy

Allergic diseases are highly prevalent disorders, mainly in industrialized countries where they constitute a high global health problem. Allergy is defined as an immune response “shifted toward a type 2 inflammation” induced by the interaction between the antigen (allergen) and IgE antibodies bound to mast cells and basophils that induce the release of inflammatory mediators that cause the clinical symptoms. Currently, allergen-specific immunotherapy (AIT) is the only treatment able to change the course of these diseases, modifying the type 2 inflammatory response by an allergenic tolerance, where the implication of T regulatory (Treg) cells is considered essential. The pollen of the olive tree is one of the most prevalent causes of respiratory allergic diseases in Mediterranean countries, inducing mainly nasal and conjunctival symptoms, although, in areas with a high antigenic load, olive-tree pollen may cause asthma exacerbation. Classically, olive-pollen allergy treatment has been based on specific immunotherapy using whole-olive pollen extracts. Despite extracts standardization, the effectiveness of this strategy varies widely, therefore there is a need for more effective AIT approaches. One of the most attractive is the use of synthetic peptides representing the B- or T-cell epitopes of the main allergens. This review summarizes experimental evidence of several T-cell epitopes derived from the Ole e 1 sequence to modulate the response to olive pollen in vitro, associated with several possible mechanisms that these peptides could be inducing, showing their usefulness as a safe preventive tool for these complex diseases.

Microarray-Based Allergy Diagnosis: Quo Vadis?

More than 30% of the world population suffers from allergy. Allergic individuals are characterized by the production of immunoglobulin E (IgE) antibodies against innocuous environmental allergens. Upon allergen recognition IgE mediates allergen-specific immediate and late-phase allergic inflammation in different organs. The identification of the disease-causing allergens by demonstrating the presence of allergen-specific IgE is the key to precision medicine in allergy because it allows tailoring different forms of prevention and treatment according to the sensitization profiles of individual allergic patients. More than 30 years ago molecular cloning started to accelerate the identification of the disease-causing allergen molecules and enabled their production as recombinant molecules. Based on recombinant allergen molecules, molecular allergy diagnosis was introduced into clinical practice and allowed dissecting the molecular sensitization profiles of allergic patients. In 2002 it was demonstrated that microarray technology allows assembling large numbers of allergen molecules on chips for the rapid serological testing of IgE sensitizations with small volumes of serum. Since then microarrayed allergens have revolutionized research and diagnosis in allergy, but several unmet needs remain. Here we show that detection of IgE- and IgG-reactivity to a panel of respiratory allergens microarrayed onto silicon elements is more sensitive than glass-based chips. We discuss the advantages of silicon-based allergen microarrays and how this technology will allow addressing hitherto unmet needs in microarray-based allergy diagnosis. Importantly, it described how the assembly of silicon microarray elements may create different microarray formats for suiting different diagnostic applications such as quick testing of single patients, medium scale testing and fully automated large scale testing.

IgE and IgG4 epitopes revealed on the major fish allergen Lat c 1

BACKGROUND

The IgE- and IgG₄-binding patterns of the major fish allergen parvalbumins are not clearly understood. IgE antibody-binding to parvalbumin from Asian seabass, Lat c 1.01, is implicated in up to 90 % of allergic reactions, although the region of IgE or IgG4 epitopes are unknown. In the present study, we characterized the specific IgE- and IgG₄-binding regions of Lat c 1.01 using serum from pediatric and adult patients with clinically-confirmed fish allergy.

METHODS

A comparative investigation of patient IgE- and IgG₄-binding to recombinant Lat c 1.01 was performed by immunoblotting and indirect ELISA using serum from 15 children and eight adults with clinically confirmed IgE-mediated reactions to fish. The IgE- and IgG₄-binding regions of Lat c 1.01 were determined by inhibition ELISA using seven overlapping peptides spanning the entire 102 amino acid sequence. Elucidated IgE-binding regions were modelled and compared to known antibody-binding regions of parvalbumins from five other fish species.

RESULTS

Ninety five percent (22/23) patients demonstrated IgE-binding to rLat c 1.01, while fewer patients (10/15 children and 7/8 adults) demonstrated robust IgG₄ binding when determined by immunoblots. IgE-binding for both cohorts was significantly higher compared to IgG₄-binding by ELISA. All patients in this study presented individual IgE and IgG₄ epitope-recognition profiles. In addition to these patient-specific antibody binding sites, general IgE epitopes were also identified at the C- and N-terminal regions of this major fish allergen.

CONCLUSIONS AND CLINICAL RELEVANCE

Our findings demonstrate two specific IgE epitopes on parvalbumin from Asian seabass, while IgG₄ binding is much lower and patient specific. This study highlights the importance of advancement in epitope analysis regardless of the age group for diagnostics and immunotherapies for fish allergy.

Past, present, and future of allergen immunotherapy vaccines

Allergen-specific immunotherapy (AIT) is an allergen-specific form of treatment for patients suffering from immunoglobulin E (IgE)-associated allergy; the most common and important immunologically mediated hypersensitivity disease. AIT is based on the administration of the disease-causing allergen with the goal to induce a protective immunity consisting of allergen-specific blocking IgG antibodies and alterations of the cellular immune response so that the patient can tolerate allergen contact. Major advantages of AIT over all other existing treatments for allergy are that AIT induces a long-lasting protection and prevents the progression of disease to severe manifestations. AIT is cost effective because it uses the patient´s own immune system for protection and potentially can be used as a preventive treatment. However, broad application of AIT is limited by mainly technical issues such as the quality of allergen preparations and the risk of inducing side effects which results in extremely cumbersome treatment schedules reducing patient´s compliance. In this article we review progress in AIT made from its beginning and provide an overview of the state of the art, the needs for further development, and possible technical solutions available through molecular allergology. Finally, we consider visions for AIT development towards prophylactic application.

Towards middle-up analysis of polyclonal antibodies: subclass-specific N-glycosylation profiling of murine immunoglobulin G (IgG) by means of HPLC-MS

In recent years, advanced HPLC-MS strategies based on intact protein (“top-down”) or protein subunit (“middle-up/middle-down”) analysis have been implemented for the characterization of therapeutic monoclonal antibodies. Here, we assess feasibility of middle-up/middle-down analysis for polyclonal IgGs exhibiting extensive sequence variability. Specifically, we addressed IgGs from mouse, representing an important model system in immunological investigations. To obtain Fc/2 portions as conserved subunits of IgGs, we made use of the bacterial protease SpeB. For this purpose, we initially determined SpeB cleavage sites in murine IgGs. The resulting Fc/2 portions characteristic of different subclasses were subsequently analysed by ion-pair reversed-phase HPLC hyphenated to high-resolution mass spectrometry. This enabled simultaneous relative quantification of IgG subclasses and their N-glycosylation variants, both of which influence IgG effector functions. To assess method capabilities in an immunological context, we applied the analytical workflow to polyclonal antibodies obtained from BALB/c mice immunized with the grass pollen allergen Phl p 6. The study revealed a shift in IgG subclasses and Fc-glycosylation patterns in total and antigen-specific IgGs from different mouse cohorts, respectively. Eventually, Fc/2 characterization may reveal other protein modifications including oxidation, amino acid exchanges, and C-terminal lysine, and may thus be implemented for quality control of functional antibodies.

Gu-Ben-Fang-Xiao attenuates allergic airway inflammation by inhibiting BAFF-mediated B cell activation

Allergic airway inflammation is one of the major pathological events involved in the development of asthma. The B cell-activating factor (BAFF)-mediated abnormal activation of B cells plays a key role in developing allergic airway inflammation. Here, we investigated the effects of Gu-Ben-Fang-Xiao decoction (GBFXD), a TCM decoction used in the prevention and treatment of allergic asthma, on allergic airway inflammation and BAFF-mediated B cell activation. A mouse model of OVA-Severe respiratory syncytial virus (RSV) induced asthma in the remission stage was administrated with GBFXD by gavage for four weeks, after which, the pulmonary function was evaluated. Pathological changes of the lung were observed by hematoxylin and eosin (HE) staining, and serum levels of IgE, BAFF, and inflammatory factors were detected by ELISA. The expression of BAFF, APRIL, and their related receptors in the lung and spleen was detected by Western blotting and RT-qPCR. Flow cytometry detected B cell subsets in the spleen, PBC, and monocyte subsets in bronchoalveolar lavage fluid (BALF). The results showed that GBFXD improved the lung function, alleviated the inflammatory changes of the lung tissue in OVA-RSV sensitized mice, and reduced levels of IL-6, TNF-α, IL1-β, INOS, IL13 as well as IL-15, IgE, BAFF in the serum of OVA-RAV mice. Additionally, GBFXD significantly reduced the proportion of CD19+CD27+ B cell subpopulation and IgE + B cell subpopulation in the PBC and spleen cells of mice. Furthermore, the expression of BAFF, APRIL, BAFFR, TACI, and AID decreased in the lung and spleen of GBFXD-treated mice, as well as the proportion of CD11b + BAFF + cell subsets in BALF. In conclusion, GBFXD has an inhibitory effect on the secretion of BAFF by pulmonary macrophages and the expression of BAFF-related receptors, thereby reducing B cell activation and the release of IgE. This proposed mechanism contributes to the improvement of allergic airway inflammation and respiratory function in an asthmatic mouse model.

IgE Autoreactivity in Atopic Dermatitis: Paving the Road for Autoimmune Diseases?

Atopic dermatitis (AD) is a common skin disease affecting 20% of the population beginning usually before one year of age. It is associated with the emergence of allergen-specific IgE, but also with autoreactive IgE, whose function remain elusive. This review discusses current knowledge relevant to the mechanisms, which leads to the secretion of autoreactive IgE and to the potential function of these antibodies in AD. Multiple autoantigens have been described to elicit an IgE-dependent response in this context. This IgE autoimmunity starts in infancy and is associated with disease severity. Furthermore, the overall prevalence of autoreactive IgE to multiple auto-antigens is high in AD patients. IgE-antigen complexes can promote a facilitated antigen presentation, a skewing of the adaptive response toward type 2 immunity, and a chronic skin barrier dysfunction and inflammation in patients or AD models. In AD, skin barrier defects and the atopic immune environment facilitate allergen sensitization and the development of other IgE-mediated allergic diseases in a process called the atopic march. AD is also associated epidemiologically with several autoimmune diseases showing autoreactive IgE secretion. Thus, a potential outcome of IgE autoreactivity in AD could be the development of further autoimmune diseases.

Tertiary lymphoid structure related B-cell IgE isotype switching and secondary lymphoid organ linked IgE production in mouse allergy model

Background

Numerous data obtained by different research laboratories indicate that specific IgE production is triggered independently of specific IgG or IgA ones and so it is not linked to fully matured germinal centers formation in the secondary lymphoid organs. The aim of this study was to clarify whether specific IgE production is triggered by low antigen doses administrated in tertiary tissues enriched by lymphoid structures.

Methods

Ovalbumin (OVA) in different doses (100 ng to 10 μg) was administrated three times a week for 4–5 weeks intraperitoneally (i.p.) or subcutaneously (s.c.) to female BALB/c mice in the wither region which is enriched in fat-associated lymphoid clusters or in the foot pad region not containing them.

Results

OVA-specific IgE was predominantly induced by low but not high antigen doses and only after immunization into the withers. IgE isotype switching was triggered exclusively in the withers adipose tissue but not in the regional lymph nodes while mature IgE expressing cells were observed both in the withers and lymph nodes. Anti-proliferative genotoxic stress inducing drugs shifted the balance from IgG1 towards IgE production.

Conclusions

Tertiary lymphoid structures possess unique environment where B-cell antibody isotype switching to IgE predominantly occurs. This phenomenon is partially explained by hampered proliferation of B-cells in these structures.

The Role of IgG4 in the Fine Tuning of Tolerance in IgE-Mediated Allergy and Cancer

Among the four immunoglobulin G (IgG) subclasses, IgG4 is the least represented in serum of a healthy human and it is considered an “odd” antibody. The IgG4 antibody has unique structural features that affect its biological function. These include the ability to undergo antigen-binding fragment (Fab)-arm exchange, to create fragment crystallizable (Fc) – Fc binding with other IgG4 and other IgG subclass antibodies, have a unique affinity profile for Fc gamma receptors (FcγRs) and no binding to complement component C1q. Altogether, these characteristics support anti-inflammatory roles of IgG4 leading to immune tolerance. Under conditions of chronic antigenic stimulation and Th2-type inflammation, both tissue and serum IgG4 levels are increased. This review seeks to highlight how in allergen immunotherapy IgG4 can confer a protective role as a “blocking” antibody and safeguard from subsequent allergen exposure, while IgG4 can confer immunomodulatory functions to support malignancy. While Th2 conditions drive polarization of macrophages to the M2a subtype, chronic antigen stimulation drives B cell class switching to IgG4 to further support phenotypical macrophage changes towards an M2b-like state. M2b-like macrophages can secrete chemokine (C-C motif) ligand 1 (CCL1) and interleukin-10 (IL-10) to support regulatory cell recruitment and to further shape a tolerogenic microenvironment. Thereby, IgG4 have a Janus-faced role, favorable in allergy but detrimental in cancer.

Preventive Allergen-Specific Vaccination Against Allergy: Mission Possible?

Vaccines for infectious diseases have improved the life of the human species in a tremendous manner. The principle of vaccination is to establish de novo adaptive immune response consisting of antibody and T cell responses against pathogens which should defend the vaccinated person against future challenge with the culprit pathogen. The situation is completely different for immunoglobulin E (IgE)-associated allergy, an immunologically-mediated hypersensitivity which is already characterized by increased IgE antibody levels and T cell responses against per se innocuous antigens (i.e., allergens). Thus, allergic patients suffer from a deviated hyper-immunity against allergens leading to inflammation upon allergen contact. Paradoxically, vaccination with allergens, termed allergen-specific immunotherapy (AIT), induces a counter immune response based on the production of high levels of allergen-specific IgG antibodies and alterations of the adaptive cellular response, which reduce allergen-induced symptoms of allergic inflammation. AIT was even shown to prevent the progression of mild to severe forms of allergy. Consequently, AIT can be considered as a form of therapeutic vaccination. In this article we describe a strategy and possible road map for the use of an AIT approach for prophylactic vaccination against allergy which is based on new molecular allergy vaccines. This road map includes the use of AIT for secondary preventive vaccination to stop the progression of clinically silent allergic sensitization toward symptomatic allergy and ultimately the prevention of allergic sensitization by maternal vaccination and/or early primary preventive vaccination of children. Prophylactic allergy vaccination with molecular allergy vaccines may allow halting the allergy epidemics affecting almost 30% of the population as it has been achieved for vaccination against infectious diseases.

New perspectives in allergen specific immunotherapy driven by big trials with house dust mite sublingual SQ® tablets

House-dust mites (HDM) allergy is the prevailing condition in subjects allergic to inhalants. Clinical studies with HDM extracts—either subcutaneous (SCIT) or sublingual (SLIT) have long been characterized by small sample size, varying allergen doses, and poorly defined endpoints assessing disease severity. In the last decade, well-designed, randomized, controlled studies recruiting thousands of patients have been conducted with newly developed HDM sublingual tablets (SQ^®-HDM tablets). This drug is easily dispersible in the oral cavity due to the patented Zydis^® technology and its allergen composition is balanced in terms of group I and group II major mite allergen content, reflecting the equal contribution of the two components to HDM sensitization. HDM is the most common allergen associated with asthma. Clinical efficacy of the SQ^® HDM SLIT-tablet in HDM allergic asthma has been evaluated in randomized, double-blind, placebo-controlled trials. Both endpoints related to “present” asthma control (inhaled corticosteroid—ICS) as well as endpoints related to “future” asthma control (occurrence of asthma exacerbations) were included in these studies, in agreement with GINA (Global Initiative for Asthma) guidelines. Based on the positive results of these studies, SQ^®-HDM SLIT-tablets were approved Europe-wide as registered drug for treating moderate-to-severe allergic rhinitis with or without allergic asthma and not well controlled HDM allergic asthma, associated with allergic rhinitis of any severity. GINA guidelines in 2017 included SLIT-tablet-based immunotherapy as an “add-on” treatment for asthmatic patients sensitized to HDM; indeed, allergen immunotherapy (AIT) is considered to be a complementary treatment option that targets the immunological of allergic diseases, representing the only treatment potentially disease-modifier or, at least, with a long-term efficacy. The availability of a safe, standardized, registered treatment for HDM respiratory allergies is pivotal in the immunotherapy field, pushing it out of a century-long limbo of amatorial interest towards the full dignity deserved by the only casual treatment of respiratory allergies.

Mechanisms of allergen-specific immunotherapy for allergic rhinitis and food allergies

Allergen-specific immunotherapy (AIT) is currently the only potential treatment for allergies including allergic rhinitis (AR) and food allergies (FA) that can modify the underlying course of the diseases. Although AIT has been performed for over a century, the precise and detailed mechanism for AIT is still unclear. Previous clinical trials have reported that successful AIT induces the reinstatement of tolerance against the specific allergen. In this review, we aim to provide an updated summary of the knowledge on the underlying mechanisms of IgE-mediated AR and FA as well as the immunological changes observed after AIT and discuss on how better understanding of these can lead to possible identification of biomarkers and novel strategies for AIT.

Vaccine against peanut allergy based on engineered virus-like particles displaying single major peanut allergens

BACKGROUND

Peanut allergy is a severe and increasingly frequent disease with high medical, psychosocial, and economic burden for affected patients and wider society. A causal, safe, and effective therapy is not yet available.

OBJECTIVE

We sought to develop an immunogenic, protective, and nonreactogenic vaccine candidate against peanut allergy based on virus-like particles (VLPs) coupled to single peanut allergens.

METHODS

To generate vaccine candidates, extracts of roasted peanut (Ara R) or the single allergens Ara h 1 or Ara h 2 were coupled to immunologically optimized Cucumber Mosaic Virus-derived VLPs (CuMVtt). BALB/c mice were sensitized intraperitoneally with peanut extract absorbed to alum. Immunotherapy consisted of a single subcutaneous injection of CuMVtt coupled to Ara R, Ara h 1, or Ara h 2.

RESULTS

The vaccines CuMVtt-Ara R, CuMVtt-Ara h 1, and CuMVtt-Ara h 2 protected peanut-sensitized mice against anaphylaxis after intravenous challenge with the whole peanut extract. Vaccines did not cause allergic reactions in sensitized mice. CuMVtt-Ara h 1 was able to induce specific IgG antibodies, diminished local reactions after skin prick tests, and reduced the infiltration of the gastrointestinal tract by eosinophils and mast cells after oral challenge with peanut. The ability of CuMVtt-Ara h 1 to protect against challenge with the whole extract was mediated by IgG, as shown via passive IgG transfer. FcγRIIb was required for protection, indicating that immune complexes with single allergens were able to block the allergic response against the whole extract, consisting of a complex allergen mixture.

CONCLUSIONS

Our data suggest that vaccination using single peanut allergens displayed on CuMVtt may represent a novel therapy against peanut allergy with a favorable safety profile.

Relationship between serum inhibitory activity for IgE and efficacy of Artemisia pollen subcutaneous immunotherapy for allergic rhinitis: a preliminary self-controlled study

Background

Biomarkers of clinical efficacy for subcutaneous immunotherapy (SCIT) on allergic rhinitis (AR) have not been identified yet. This study aims to assess the clinical relevance of serum inhibitory activity for IgE by the method of enzyme-linked immunosorbent facilitated antigen binding (ELIFAB) during SCIT for Artemisia-sensitized AR patients.

Methods

19 AR patients were studied who had undergone Artemisia-specific SCIT for more than 8 months (19.68 months on average, ranging from 9 to 33 months). Peripheral bloods were collected before and after treatment. The serum inhibitory activity for IgE was tested by ELIFAB and the level of Artemisia-specific IgG4 (Artemisia-sIgG4) was determined by ELISA. Clinical improvement was evaluated based on the symptom scores and rescue medication use (SMS). The 2-tailed Wilcoxon signed-rank test and the Spearman rank test (two-tailed) were used to analyze data by using SPSS 20.0, with P values of less than 0.05 considered as significant.

Results

The SMS decreased significantly after SCIT (before: 12.79 ± 4.250, after: 6.11 ± 3.828, P = 0.000 < 0.01), the treatment was remarkably effective for 6 patients, effective for 10 and ineffective for 3, along with a total effective rate 84.21%. The serum inhibitory activity for IgE increased significantly after SCIT (P < 0.05) and was correlated with the levels of Artemisia-sIgG4 (r = − 0.501, P = 0.002 < 0.01). The levels of Artemisia-sIgG4 elevated dramatically after treatment (P < 0.01) and were related with the duration of treatment (r = 0.558, P = 0.000 < 0.01). But there was no relationship between clinical improvements and the serum inhibitory activity for IgE.

Conclusions

The serum inhibitory activity for IgE increased significantly after SCIT, however, there was no correlation between it and clinical improvements by statistics analysis. So whether the serum inhibitory activity for IgE can act as biomarker of efficacy for SCIT or not needs to be studied further.

Two years of treatment with the recombinant grass pollen allergy vaccine BM32 induces a continuously increasing allergen-specific IgG4 response

Background

BM32, a grass pollen allergy vaccine containing four recombinant fusion proteins consisting of hepatitis B-derived PreS and hypoallergenic peptides from the major timothy grass pollen allergens adsorbed on aluminium hydroxide has been shown to be safe and to improve clinical symptoms of grass pollen allergy upon allergen-specific immunotherapy (AIT). We have investigated the immune responses in patients from a two years double-blind, placebo-controlled AIT field trial with BM32.

Methods

Blood samples from patients treated with BM32 (n = 27) or placebo (Aluminium hydroxide) (n = 13) were obtained to study the effects of vaccination and natural allergen exposure on allergen-specific antibody, T cell and cytokine responses. Allergen-specific IgE, IgG, IgG₁ and IgG₄ levels were determined by ImmunoCAP and ELISA, respectively. Allergen-specific lymphocyte proliferation by ³H thymidine incorporation and multiple cytokine responses with a human 17-plex cytokine assay were studied in cultured peripheral blood mononuclear cells (PBMCs).

Findings

Two years AIT comprising two courses of 3 pre-seasonal injections of BM32 and a single booster after the first pollen season induced a continuously increasing (year 2 > year 1) allergen-specific IgG₄ response without boosting allergen-specific IgE responses. Specific IgG₄ responses were accompanied by low stimulation of allergen-specific PBMC responses. Increases of allergen-specific pro-inflammatory cytokine responses were absent. The rise of allergen-specific IgE induced by seasonal grass pollen exposure was partially blunted in BM32-treated patients.

Interpretation

AIT with BM32 is characterised by the induction of a non-inflammatory, continuously increasing allergen-specific IgG₄ response (year 2 > year1) which may explain that clinical efficacy was higher in year 2 than in year 1. The good safety profile of BM32 may be explained by lack of IgE reactivity and low stimulation of allergen-specific T cell and cytokine responses.

Fundings

Grants F4605, F4613 and DK 1248-B13 of the Austrian Science Fund (FWF).

Dietary Omega-3 Fatty Acid Dampens Allergic Rhinitis via Eosinophilic Production of the Anti-Allergic Lipid Mediator 15-Hydroxyeicosapentaenoic Acid in Mice

The metabolism and generation of bioactive lipid mediators are key events in the exertion of the beneficial effects of dietary omega-3 fatty acids in the regulation of allergic inflammation. Here, we found that dietary linseed oil, which contains high amounts of alpha-linolenic acid (ALA) dampened allergic rhinitis through eosinophilic production of 15-hydroxyeicosapentaenoic acid (15-HEPE), a metabolite of eicosapentaenoic acid (EPA). Lipidomic analysis revealed that 15-HEPE was particularly accumulated in the nasal passage of linseed oil-fed mice after the development of allergic rhinitis with the increasing number of eosinophils. Indeed, the conversion of EPA to 15-HEPE was mediated by the 15-lipoxygenase activity of eosinophils. Intranasal injection of 15-HEPE dampened allergic symptoms by inhibiting mast cell degranulation, which was mediated by the action of peroxisome proliferator-activated receptor gamma. These findings identify 15-HEPE as a novel EPA-derived, and eosinophil-dependent anti-allergic metabolite, and provide a preventive and therapeutic strategy against allergic rhinitis.

Tracing IgE-Producing Cells in Allergic Patients

Immunoglobulin E (IgE) is the key immunoglobulin in the pathogenesis of IgE associated allergic diseases affecting 30% of the world population. Recent data suggest that allergen-specific IgE levels in serum of allergic patients are sustained by two different mechanisms: inducible IgE production through allergen exposure, and continuous IgE production occurring even in the absence of allergen stimulus that maintains IgE levels. This assumption is supported by two observations. First, allergen exposure induces transient increases of systemic IgE production. Second, reduction in IgE levels upon depletion of IgE from the blood of allergic patients using immunoapheresis is only temporary and IgE levels quickly return to pre-treatment levels even in the absence of allergen exposure. Though IgE production has been observed in the peripheral blood and locally in various human tissues (e.g., nose, lung, spleen, bone marrow), the origin and main sites of IgE production in humans remain unknown. Furthermore, IgE-producing cells in humans have yet to be fully characterized. Capturing IgE-producing cells is challenging not only because current staining technologies are inadequate, but also because the cells are rare, they are difficult to discriminate from cells bearing IgE bound to IgE-receptors, and plasma cells express little IgE on their surface. However, due to the central role in mediating both the early and late phases of allergy, free IgE, IgE-bearing effector cells and IgE-producing cells are important therapeutic targets. Here, we discuss current knowledge and unanswered questions regarding IgE production in allergic patients as well as possible therapeutic approaches targeting IgE.