Inhibition of allergen-IgE binding to B cells by IgG antibodies after grass pollen immunotherapy

Single-Domain Antibodies-Novel Tools to Study and Treat Allergies

IgE-mediated allergies represent a major health problem in the modern world. Apart from allergen-specific immunotherapy (AIT), the only disease-modifying treatment, researchers focus on biologics that target different key molecules such as allergens, IgE, or type 2 cytokines to ameliorate allergic symptoms. Single-domain antibodies, or nanobodies, are the newcomers in biotherapeutics, and their huge potential is being investigated in various research fields since their discovery 30 years ago. While they are dominantly applied for theranostics of cancer and treatment of infectious diseases, nanobodies have become increasingly substantial in allergology over the last decade. In this review, we discuss the prerequisites that we consider to be important for generating useful nanobody-based drug candidates for treating allergies. We further summarize the available research data on nanobodies used as allergen monitoring and detection probes and for therapeutic approaches. We reflect on the limitations that have to be addressed during the development process, such as in vivo half-life and immunogenicity. Finally, we speculate about novel application formats for allergy treatment that might be available in the future.

The combination of allergen immunotherapy and biologics for inhalant allergies: Exploring the synergy

The development of monoclonal antibodies that selectively target IgE and type 2 immunity has opened new possibilities in the treatment of allergies. Although they have been used mainly as single therapies found to have efficacy in the management of asthma and other T2-mediated diseases, there is a growing interest in using these monoclonal antibodies in combination with allergen immunotherapy (AIT). AIT has transformed the treatment of allergic diseases by aiming to modify the underlying immune response to allergens rather than just providing temporary symptom relief. Despite the proven efficacy and safety of AIT, unmet needs call for further research and innovation. Combination strategies involving biologics and AIT exhibit potential in improving short-term efficacy, reducing adverse events, and increasing immunologic tolerance. Anti-IgE emerges as the most promising therapeutic strategy, not only enhancing AIT's safety and tolerability but also providing additional evidence of efficacy compared with AIT alone. Anti-interleukin-4 receptor offers a reduction in adverse effects and an improved immunologic profile when combined with AIT; however, its impact on short-term efficacy seems limited. The combination of cat dander subcutaneous immunotherapy with anti-thymic stromal lymphopoietin was synergistic with enhanced efficacy and altered immune responses that persisted for 1 year after discontinuation compared with AIT alone. Long-term studies are needed to evaluate the sustained benefits and safety profiles of combination strategies.

Elevated level of multibranched complex glycan reveals an allergic tolerance status

BACKGROUND

Allergen immunotherapy (AIT) is the only disease-modifying therapy that can achieve immune tolerance in patients through long-term allergen stimulation. Glycans play crucial roles in allergic disease, but no information on changes in glycosylation related to an allergic tolerance status has been reported.

METHODS

Fifty-seven patients with house dust mite (HDM) allergies were enrolled. Twenty-eight patients were not treated with AIT, 19 patients had just entered the AIT maintenance treatment phase, and 10 patients had been in the AIT maintenance phase for more than 1 year. Serum protein N-glycans were analyzed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), which included linkage-specific sialylation information.

RESULTS

Eighty-four N-glycans were identified in all three groups. Compared with the patients treated without AIT, the patients treated with AIT for a shorter time showed downregulated expression of high-mannose glycans and upregulated expression of α2,6 sialic acid. The patients treated with AIT in the maintenance phase for over 1 year, which was considered the start of immunological tolerance, showed downregulated expression of biantennary N-glycans and upregulated expression of multibranched and complex N-glycans. Nine N-glycans were changed between allergic and allergic-tolerant patients.

CONCLUSIONS

The glycan form changed from mannose to a more complex type as treatment time increased, and multibranched complex glycans have the potential to be used as a monitoring indicator of immune tolerance. This serum N-glycome analysis provided important information for a deeper understanding of AIT treatment at the molecular level.

Follow-up to Adolescence after Early Peanut Introduction for Allergy Prevention

BACKGROUND

A randomized trial demonstrated consumption of peanut from infancy to age 5 years prevented the development of peanut allergy. An extension of that trial demonstrated the effect persisted after 1 year of peanut avoidance. This follow-up trial examined the durability of peanut tolerance at age 144 months after years of ad libitum peanut consumption.

METHODS

Participants from a randomized peanut consumption trial were assessed for peanut allergy following an extended period of eating or avoiding peanuts as desired. The primary end point was the rate of peanut allergy at age 144 months.

RESULTS

We enrolled 508 of the original 640 participants (79.4%); 497 had complete primary end point data. At age 144 months, peanut allergy remained significantly more prevalent in participants in the original peanut avoidance group than in the original peanut consumption group (15.4% [38 of 246 participants] vs. 4.4% [11 of 251 participants]; P<0.001). Participants in both groups reported avoiding peanuts for prolonged periods of time between 72 and 144 months. Participants at 144 months in the peanut consumption group had levels of Ara h2-specific immunoglobulin E (a peanut allergen associated with anaphylaxis) of 0.03 ± 3.42 kU/l and levels of peanut-specific immunoglobulin G4 of 535.5 ± 4.98 μg/l, whereas participants in the peanut avoidance group had levels of Ara h2-specific immunoglobulin E of 0.06 ± 11.21 kU/l and levels of peanut-specific immunoglobulin G4 of 209.3 ± 3.84 μg/l. Adverse events were uncommon, and the majority were related to the food challenge.

CONCLUSIONS

Peanut consumption, starting in infancy and continuing to age 5 years, provided lasting tolerance to peanut into adolescence irrespective of subsequent peanut consumption, demonstrating that long-term prevention and tolerance can be achieved in food allergy. (Funded by the National Institute of Allergy and Infectious Diseases and others; ITN070AD, ClinicalTrials.gov number, NCT03546413.).

Venom Immunotherapy Does Not Affect Survival of Patients with Malignant Tumor in Poland

Background: Allergen immunotherapy (AIT) is a well-established and efficient method of causative treatment for allergic rhinitis, asthma and insect venom allergy. Traditionally, a recent history of malignant neoplasm is regarded as a contraindication to AIT due to concerns that AIT might stimulate tumor growth. However, there are no data confirming that the silencing of the Th2 response affects prognosis in cancer. Objectives: The aim of this study was to investigate frequency of malignant tumors in patients undergoing AIT and the association between AIT and cancer-related mortality. Patients and Methods: A group of 2577 patients with insect venom allergy undergoing AIT in 10 Polish allergology centers was screened in the Polish National Cancer Registry. Data on cancer type, diagnosis time and patients' survival were collected and compared with the general population. Results: In the study group, 86 cases of malignancies were found in 85 patients (3.3% of the group). The most common were breast (19 cases), lung (9 cases), skin (8 cases), colon and prostate cancers (5 cases each). There were 21 cases diagnosed before AIT, 38 during and 27 after completing AIT. Laplace's crude incidence rate was 159.5/100,000/year (general population rate: 260/100,000/year). During follow-up, 13 deaths related to cancer were revealed (15% of patients with cancer). Laplace's cancer mortality rate was 37.3/100,000/year (general population rate: 136.8/100,000/year). Conclusions: Malignancy was found in patients undergoing immunotherapy less often than in the general population. Patients with cancer diagnosed during or after AIT did not show a lower survival rate, which suggests that AIT does not affect the prognosis.

Mechanisms and Predictive Biomarkers of Allergen Immunotherapy in the Clinic

Allergen immunotherapy (AIT) remains to be the only disease-modifying treatment for IgE-mediated allergic diseases such as allergic rhinitis. It can provide long-term clinical benefits when given for 3 years or longer. Mechanisms of immune tolerance induction by AIT are underscored by the modulation of several compartments within the immune system. These include repair of disruption in epithelial barrier integrity, modulation of the innate immune compartment that includes regulatory dendritic cells and innate lymphoid cells, and adaptive immune compartments such as induction of regulatory T and B cells. Altogether, these are also associated with the dampening of allergen-specific TH2 and T follicular helper cell responses and subsequent generation of blocking antibodies. Although AIT is effective in modifying the immune response, there is a lack of validated and clinically relevant biomarkers that can be used to monitor desensitization, efficacy, and the likelihood of response, all of which can contribute to accelerating personalized medication and increasing patient care. Candidate biomarkers comprise humoral, cellular, metabolic, and in vivo biomarkers; however, these are primarily studied in small trials and require further validation. In this review, we evaluate the current candidates of biomarkers of AIT and how we can implement changes in future studies to help us identify clinically relevant biomarkers of safety, compliance, and efficacy.

KAAACI Guidelines for Allergen Immunotherapy

Allergen immunotherapy (AIT) is a causative treatment for various allergic diseases such as allergic rhinitis, allergic asthma, and bee venom allergy that induces tolerance to offending allergens. The need for uniform practice guidelines in AIT is continuously growing because of the increasing discovery of potential candidates for AIT and evolving interest in new therapeutic approaches. This guideline is an updated version of the Korean Academy of Asthma Allergy and Clinical Immunology recommendations for AIT published in 2010. This updated guideline proposes an expert opinion by allergy, pediatrics, and otorhinolaryngology specialists with an extensive literature review. The guideline deals with basic knowledge and methodological aspects of AIT, including mechanisms, clinical efficacy, patient selection, allergens extract selection, schedule and doses, management of adverse reactions, efficacy measurements, and special consideration in pediatrics. The guidelines for sublingual immunotherapy will be covered in detail in a separate article.

Mechanisms of Allergen Immunotherapy and Potential Biomarkers for Clinical Evaluation

Allergen-immunotherapy (AIT) is an efficacious and disease-modifying treatment option for IgE-mediated diseases. Among these allergic rhinitis, insect venom allergy, food allergy, and allergic asthma are the most common candidates for AIT. AIT gives rise to clinical immunotolerance which may last for years after the treatment cessation. Mechanisms of AIT include suppression of allergic inflammation in target tissues and stimulation of the production of blocking antibodies, especially IgG4 and IgA. These mechanisms are followed by a reduction of underlying allergen-specific Th2 cell-driven responses to the allergens. Tolerance induction takes place through the desensitization of effector cells and stimulation of regulatory T cells that show their effects by mechanisms involving cell-cell cross-talk, but also other mechanisms, e.g., by the production of immunomodulatory cytokines such as, e.g., IL-10 and TGF-beta. From a personalized medical perspective, there is a need for clinical biomarkers of value in selecting responders and optimizing patient care during AIT. Also, a deeper understanding of underlying mechanistic processes will improve AIT's future outcomes. In this paper, the current knowledge of mechanisms in AIT is reviewed with a special focus on biomarkers of this therapy.

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.

The role of IgG1 and IgG4 as dominant IgE-blocking antibodies shifts during allergen immunotherapy

BACKGROUND

The induction of allergen-specific IgE-blocking antibodies is a hallmark of allergen immunotherapy (AIT). The inhibitory bioactivity has largely been attributed to IgG₄; however, our recent studies indicated the dominance of IgG₁ early in AIT.

OBJECTIVES

Here, the IgE-blocking activity and avidity of allergen-specific IgG₁ and IgG₄ antibodies were monitored throughout 3 years of treatment.

METHODS

Serum samples from 24 patients were collected before and regularly during AIT with birch pollen. Bet v 1-specific IgG₁ and IgG₄ levels were determined by ELISA and ImmunoCAP, respectively. Unmodified and IgG₁- or IgG₄-depleted samples were compared for their inhibition of Bet v 1-induced basophil activation. The stability of Bet v 1-antibody complexes was compared by ELISA and by surface plasmon resonance.

RESULTS

Bet v 1-specific IgG₁ and IgG₄ levels peaked at 12 and 24 months of AIT, respectively. Serological IgE-blocking peaked at 6 months and remained high thereafter. In the first year of therapy, depletion of IgG₁ clearly diminished the inhibition of basophil activation while the absence of IgG₄ hardly reduced IgE-blocking. Then, IgG₄ became the main inhibitory isotype in most individuals. Both isotypes displayed high avidity to Bet v 1 ab initio of AIT, which did not increase during treatment. Bet v 1-IgG₁ complexes were enduringly more stable than Bet v 1-IgG₄ complexes were.

CONCLUSIONS

In spite of the constant avidity of AIT-induced allergen-specific IgG₁ and IgG₄ antibodies, their dominance in IgE-blocking shifted in the course of treatment. The blocking activity of allergen-specific IgG₁ should not be underestimated, particularly early in AIT.

Treating allergies via skin - Recent advances in cutaneous allergen immunotherapy

Subcutaneous allergen immunotherapy has been practiced clinically for decades to treat airborne allergies. Recently, the cutaneous route, which exploits the immunocompetence of the skin has received attention, which is evident from attempts to use it to treat peanut allergy. Delivery of allergens into the skin is inherently impeded by the barrier imposed by stratum corneum, the top layer of the skin. While the stratum corneum barrier must be overcome for efficient allergen delivery, excessive disruption of this layer can predispose to development of allergic inflammation. Thus, the most desirable allergen delivery approach must provide a balance between the level of skin disruption and the amount of allergen delivered. Such an approach should aim to achieve high allergen delivery efficiency across various skin types independent of age and ethnicity, and optimize variables such as safety profile, allergen dosage, treatment frequency, application time and patient compliance. The ability to precisely quantify the amount of allergen being delivered into the skin is crucial since it can allow for allergen dose optimization and can promote consistency and reproducibility in treatment response. In this work we review prominent cutaneous delivery approaches, and offer a perspective on further improvisation in cutaneous allergen-specific immunotherapy.

Allergen immunotherapy: past, present and future

Allergen immunotherapy is a form of therapeutic vaccination for established IgE-mediated hypersensitivity to common allergen sources such as pollens, house dust mites and the venom of stinging insects. The classical protocol, introduced in 1911, involves repeated subcutaneous injection of increasing amounts of allergen extract, followed by maintenance injections over a period of 3 years, achieving a form of allergen-specific tolerance that provides clinical benefit for years after its discontinuation. More recently, administration through the sublingual route has emerged as an effective, safe alternative. Oral immunotherapy for peanut allergy induces effective ‘desensitization’ but not long-term tolerance. Research and clinical trials over the past few decades have elucidated the mechanisms underlying immunotherapy-induced tolerance, involving a reduction of allergen-specific T helper 2 (T_H2) cells, an induction of regulatory T and B cells, and production of IgG and IgA ‘blocking’ antibodies. To better harness these mechanisms, novel strategies are being explored to achieve safer, effective, more convenient regimens and more durable long-term tolerance; these include alternative routes for current immunotherapy approaches, novel adjuvants, use of recombinant allergens (including hypoallergenic variants) and combination of allergens with immune modifiers or monoclonal antibodies targeting the T_H2 cell pathway.

Durham and Shamji review the history and future of allergen immunotherapy for established IgE-mediated hypersensitivity to common allergens. They describe the mechanisms of immunotherapy-induced tolerance and the new strategies being explored to achieve safer, more effective, long-term tolerance.

Bee Pollen: Clinical Trials and Patent Applications

Bee pollen is a natural cocktail of floral nectar, flower pollen, enzymes, and salivary secretions produced by honeybees. Bee pollen is one of the bee products most enriched in proteins, polysaccharides, polyphenols, lipids, minerals, and vitamins. It has a significant health and medicinal impact and provides protection against many diseases, including diabetes, cancer, infectious, and cardiovascular. Bee pollen is commonly promoted as a cost-effective functional food. In particular, bee pollen has been applied in clinical trials for allergies and prostate illnesses, with a few investigations on cancer and skin problems. However, it is involved in several patents and health recipes to combat chronic health problems. This review aimed to highlight the clinical trials and patents involving bee pollen for different cases and to present the role of bee pollen as a supplementary food and a potential product in cosmetic applications.

Mechanisms and biomarkers of subcutaneous immunotherapy and sublingual immunotherapy in allergen immunotherapy

There are currently no biomarkers that can accurately predict clinical outcomes and segregate responders from nonresponders in allergen immunotherapy (AIT). Therefore, identifying a reliable predictive biomarker is essential to enable clinicians to tailor personalized therapy. New developments in AIT biomarkers are currently being explored, and it would be important to identify key areas of development and their feasibility for use in the clinic. Biomarkers can be categorized broadly into seven domains: (i) Immunoglobulin E (IgE), (ii) IgG and IgA responses, (iii) IgE -facilitated allergen binding/blocking factor, (iv) basophil activation, (v) cytokines and chemokines, (vi) cellular markers, and (vii) in vivo biomarkers. Despite their potential, most biomarkers remain infeasible to be translated to the clinical setting due to requirements of complex instruments such as flow cytometry. The identification of suitable biomarkers remains key in predicting outcomes of AIT and requires more research. Additional exploration into integrative biomarkers may be required.

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).

Exploring the role of basophil activation test in diagnosis of Dermatophagoides farinae sensitization and evaluation of therapeutic efficacy of subcutaneous immunotherapy in children

OBJECTIVE

It aims to detect basophil activation ratio (%CD63⁺ ) in peripheral blood of children with allergic asthma and rhinitis by using Flow cytometry (FCM) , so as to analyze the application values and clinical relevance of the Basophil Activation Test (BAT) in diagnosis of Dermatophagoides farinae (Derf) sensitization and monitoring therapeutic efficacy of subcutaneous immunotherapy (SCIT).

METHODS

It was a prospective study. From the newly diagnosed children with asthma and rhinitis in our pediatric clinic, 39 patients diagnosed Derf sensitization and 15 patients not allergic to Derf were enrolled; another 4 healthy children were taken as control group. Using Derf extracts in concentration of 1 μg/ml, 10 μg/ml and 100 μg/ml as the stimulus, BAT results were expressed as %CD63⁺ in diagnosis of Derf sensitization and its correlation with skin prick tests (SPT), serum total IgE (tIgE), specific IgE (sIgE), sIgE/tIgE, specific IgG4 (sIgG4), FEV1%pred in pulmonary ventilation function, exhaled nitric oxide (FeNO), children asthma control test (C-ACT) and visual analogue scale (VAS) were observed. In sensitization group, %CD63⁺ , sIgG4 and clinical indicators were detected again from patients who had received SCIT to analyze their internal connections.

RESULTS

The average levels of %CD63⁺ in three concentrations showed an increasing concentration-dependent trend overall. %CD63⁺ in sensitization group was significantly higher than that in the other two groups. The analysis of ROC for Derf sensitization showed the area under the curve (AUC) for BAT in three concentrations were higher than that for sIgE whose AUC is 0.893. %CD63⁺ was positively correlated with SPT grade, sIgE, sIgE/tIgE and VAS, and negatively correlated with C-ACT. In patients receiving SCIT, %CD63⁺ became lower and sIgG4 level became higher than pretreatment. There was no obvious change in sIgG4 in those who hadn't received SCIT.

CONCLUSIONS

BAT is a reliable and non-invasive tool for diagnosis of Derf sensitization in children with asthma and rhinitis. CD63-based BAT has clinical value to monitor outcome of SCIT, and the change of basophil activation is inherently related to induction of sIgG4.

Allergen Immunotherapy: Current and Future Trends

Allergen immunotherapy (AIT) is the sole disease-modifying treatment for allergic rhinitis; it prevents rhinitis from progressing to asthma and lowers medication use. AIT against mites, insect venom, and certain kinds of pollen is effective. The mechanism of action of AIT is based on inducing immunological tolerance characterized by increased IL-10, TGF-β, and IgG4 levels and Treg cell counts. However, AIT requires prolonged schemes of administration and is sometimes associated with adverse reactions. Over the last decade, novel forms of AIT have been developed, focused on better allergen identification, structural modifications to preserve epitopes for B or T cells, post-traductional alteration through chemical processes, and the addition of adjuvants. These modified allergens induce clinical-immunological effects similar to those mentioned above, increasing the tolerance to other related allergens but with fewer side effects. Clinical studies have shown that molecular AIT is efficient in treating grass and birch allergies. This article reviews the possibility of a new AIT to improve the treatment of allergic illness.

Allergen-Specific IgE and IgG4 as Biomarkers for Immunologic Changes during Subcutaneous Allergen Immunotherapy

(1) Background: Biomarkers of efficacy for subcutaneous immunotherapy (SCIT) on allergic rhinitis have not been evaluated in details. The present study aims to assess the relevance of measuring of sIgE, sIgG4 and IgE/IgG4 ratio during SCIT in patients with allergic rhinitis; (2) Methods: 20 patients, 13 men and 7 women aged 19 to 58 years, with clinically manifested seasonal and perennial allergic rhinitis were studied. At the initiation and in the end of the three-year course of SCIT serum allergen-specific IgE and IgG4 were measured with ImmunoCAP system. The sIgE/sIgG4 ratio was calculated as a biomarker for immunologic effectiveness; (3) Results: There was a significant increase of sIgG4 antibodies (p < 0.05), while at the end of SCIT for the sIgE levels no significant changes were seen (p > 0.05). Moreover, 90% of patients showed a decrease of the IgE/IgG4 ratio; (4) Conclusions: In most of treated patients with AR, SCIT with Bulgarian allergen products leads to clear immunological changes. After a 3-year of SCIT there is a significant increase in allergen specific IgG4 levels and both decrease of sIgE and IgE/IgG4 ratio. sIgE, sIgG4 and IgE/IgG4 ratio can be used as a substantial biomarker for predicting immunological effectiveness of SCIT.

The role of allergen-specific IgE, IgG and IgA in allergic disease

Immunoglobulin E (IgE)‐mediated allergy is the most common hypersensitivity disease affecting more than 30% of the population. Exposure to even minute quantities of allergens can lead to the production of IgE antibodies in atopic individuals. This is termed allergic sensitization, which occurs mainly in early childhood. Allergen‐specific IgE then binds to the high (FcεRI) and low‐affinity receptors (FcεRII, also called CD23) for IgE on effector cells and antigen‐presenting cells. Subsequent and repeated allergen exposure increases allergen‐specific IgE levels and, by receptor cross‐linking, triggers immediate release of inflammatory mediators from mast cells and basophils whereas IgE‐facilitated allergen presentation perpetuates T cell–mediated allergic inflammation. Due to engagement of receptors which are highly selective for IgE, even tiny amounts of allergens can induce massive inflammation. Naturally occurring allergen‐specific IgG and IgA antibodies usually recognize different epitopes on allergens compared with IgE and do not efficiently interfere with allergen‐induced inflammation. However, IgG and IgA antibodies to these important IgE epitopes can be induced by allergen‐specific immunotherapy or by passive immunization. These will lead to competition with IgE for binding with the allergen and prevent allergic responses. Similarly, anti‐IgE treatment does the same by preventing IgE from binding to its receptor on mast cells and basophils. Here, we review the complex interplay of allergen‐specific IgE, IgG and IgA and the corresponding cell receptors in allergic diseases and its relevance for diagnosis, treatment and prevention of allergy.

Autologous enzyme-linked immunosorbent facilitated antigen binding detects IgE-blocking activity based on direct competition between allergen-specific IgE and non-IgE

Aim: To measure IgE-blocking activity induced by allergen immunotherapy (AIT) by an enzyme-linked immunosorbent facilitated antigen binding (ELIFAB) assay based on autologous immunoglobulin competition. Methods: The developed ELIFAB assay was used to investigate the kinetics of IgE-blocking activity in 87 patients at multiple AIT treatment time points, in comparison to the changes in IgG4. Results: High ELIFAB response was observed until 2.5 months of AIT, then significantly decreased after 4 months and remained suppressed during the 3-year AIT period. After treatment cessation, the ELIFAB response was maintained at the level seen at the 4-6 month treatment time point, similar to IgG4, indicating sustained IgE-blocking activity related to IgG4. Conclusion: This ELIFAB assay measures the IgE-blocking activity for autologous allergen-specific IgE and non-IgE during and after immunotherapy. It is suited for measuring the sustained IgE-blocking activity induced by AIT.

The glycosyltransferase ST3GAL2 modulates virus proliferation and the inflammation response in porcine reproductive and respiratory syndrome virus infection

β-galactoside α-2,3-sialyltransferase 2 (ST3GAL2) is a member of the sialyltransferase family that mediates terminal modification of glycoproteins and glycolipids. ST3GAL2 has been found to play a role in obesity, aging, and malignant diseases. In this study, we cloned porcine ST3GAL2 (pST3GAL2) from porcine alveolar macrophages (PAMs), and its role in porcine reproductive and respiratory syndrome virus (PRRSV) infection was investigated by transcriptome analysis. pST3GAL2 was found to be located in the Golgi apparatus, and it was expressed at high levels in PRRSV-infected PAMs. Overexpression of pST3GAL2 resulted in a slight increase in PRRSV proliferation, and the interaction between pST3GAL2 and GP2a of PRRSV was detected by coimmunoprecipitation and confocal microscopy. The expression of pro-inflammatory cytokines (IFN-β, IL-2, IL-6, IL-18, IL-1β and TNF-α) was significantly inhibited in pST3GAL2-overexpressing, PRRSV-infected cells and upregulated in PRRSV-infected pST3GAL2-knockout cells, while the pattern of expression of anti-inflammatory cytokines (IL-4 and IL-10) was diametrically opposite. Our results demonstrate that the regulation of pST3GAL2 plays an important role in PRRSV proliferation and functional alterations in virus-infected cells. These results contribute to our understanding of the role of β-galactoside α-2,3-sialyltransferase 2 in antiviral immunity.

Serum Concentrations of Antigen-Specific IgG4 in Patients with Japanese Cedar Pollinosis

Purpose: To elucidate the usefulness of Japanese cedar pollen (JCP)-specific antigen-specific immunoglobulin (IgG) 4 as a biomarker for predicting the efficacy of sublingual immunotherapy for cedar pollen-induced allergic rhinitis. Methods: We divided a total of 105 cases with Japanese cedar pollinosis into three groups: “SLIT Successful,” SLIT Unsatisfactory,” and “SCIT” groups. The SLIT group patients were treated with JCP Droplet (Torii Pharmaceutical Co. Ltd., Tokyo, Japan) for one year from 2015 and were divided into two groups, the SLIT Successful group or the SLIT Unsatisfactory group. The SLIT Successful group (n = 16) were subjects treated by SLIT only, who were able to experience control of their naso-ocular symptoms without the need for antiallergic rescue agents during the peak season of atmospheric pollen. The SLIT Unsatisfactory group (n = 76) comprised subjects treated with SLIT only, who did not respond successfully, and were administered with rescue agents to control their naso-ocular symptoms. The SCIT group had been treated with standardized JCP extract (Torii Pharmaceutical Co., Ltd., Tokyo, Japan) for three years from 2012, and were also able to experience control of their symptoms during the peak pollen season without the need for antiallergic rescue agents. We determined the serum level of JCP-specific immunoglobulin E (IgE), IgG, and IgG4 used in the 3gAllergy-specific IgE assay (3gAllergy). The serum levels of periostin and SCCA2 were measured using established ELISA procedures (clones SS18A and SS17B; Shino-Test, Japan) following the manufacturer’s instructions. We then made ROC curves for each group and assessed which index was best able to predict the efficacy of sublingual immunotherapy. Results: Serum JCP-specific IgE was significantly lower in the SCIT group than in the SLIT Successful group and the SLIT Unsatisfactory group (p < 0.05). Serum JCP-specific IgG was significantly higher in the SCIT group and the SLIT Successful group than in the SLIT Unsatisfactory group (p < 0.05). Serum JCP-specific IgG4 was also significantly higher in the SCIT group and the SLIT Successful group than in the SLIT Unsatisfactory group (p < 0.05). There was no significant difference among serum levels of periostin in the SCIT group, the SLIT Successful group, or the SLIT Unsatisfactory group. There was also no significant difference in SCCA2 among the three groups. In terms of ROC curves, a serum JCP-specific IgG4 value greater than 989.5 UA/mL showed the best sensitivity (93.3%) and specificity (94.7%) (p < 0.05) among other parameters. Conclusions: The serum JCP-specific IgG4 level is significantly correlated with the clinical efficacy of SLIT. Serum JCP-specific IgG4 cutoff levels greater than 989.5 UA/mL were correlated with an effective clinical response to SLIT, with a sensitivity of 93.3% and a specificity of 94.7%.

The role of CD23 in the regulation of allergic responses

IgE, the key molecule in atopy has been shown to bind two receptors, FcεRI, the high‐affinity receptor, and FcεRII (CD23), binding IgE with lower affinity. Whereas cross‐linking of IgE on FcεRI expressed by mast cells and basophils triggers the allergic reaction, binding of IgE to CD23 on B cells plays an important role in both IgE regulation and presentation. Furthermore, IgE‐immune complexes (IgE‐ICs) bound by B cells enhance antibody and T cell responses in mice and humans. However, the mechanisms that regulate the targeting of the two receptors and the respective function of the two pathways in inflammation or homeostasis are still a matter of debate. Here, we focus on CD23 and discuss several mechanisms related to IgE binding, as well as the impact of the IgE/antigen‐binding on different immune cells expressing CD23. One recent paper has shown that free IgE preferentially binds to FcεRI whereas IgE‐ICs are preferentially captured by CD23. Binding of IgE‐ICs to CD23 on B cells can, on one hand, regulate serum IgE and prevent effector cell activation and on the other hand facilitate antigen presentation by delivering the antigen to dendritic cells. These data argue for a multifunctional role of CD23 for modulating IgE serum levels and immune responses.

Immunological Responses and Biomarkers for Allergen-Specific Immunotherapy Against Inhaled Allergens

Long-term efficacy that occurs with allergen immunotherapy of proven value is associated with decreases in IgE-dependent activation of mast cells and tissue eosinophilia. This suppression of type 2 immunity is accompanied by early induction of regulatory T cells, immune deviation in favor of T_H1 responses, and induction of local and systemic IgG, IgG₄, and IgA antibodies. These "protective" antibodies can inhibit allergen-IgE complex formation and consequent mast cell triggering and IgE-facilitated T_H2-cell activation. Recent studies have highlighted the importance of innate responses mediated by type 2 dendritic cells and innate lymphoid cells in allergic inflammation. These cell types are under the regulation of cytokines such as thymic stromal lymphopoietin and IL-33 derived from the respiratory epithelium. Novel subsets of regulatory cells induced by immunotherapy include IL-35-producing regulatory T cells, regulatory B cells, a subset of T follicular regulatory cells, and IL-10-producing group 2 innate lymphoid cells. These mechanisms point to biomarkers that require testing for their ability to predict clinical response to immunotherapy and to inform novel approaches for better efficacy, safety, and long-term tolerance.

Passive Prophylactic Administration with a Single Dose of Anti-Fel d 1 Monoclonal Antibodies REGN1908-1909 in Cat Allergen-induced Allergic Rhinitis: A Randomized, Double-Blind, Placebo-controlled Clinical Trial

Rationale: Sensitization to Fel d 1 (Felis domesticus allergen 1) contributes to persistent allergic rhinitis and asthma. Existing treatment options for cat allergy, including allergen immunotherapy, are only moderately effective, and allergen immunotherapy has limited use because of safety concerns.

Objectives: To explore the relationship among the pharmacokinetic, clinical, and immunological effects of anti–Fel d 1 monoclonal antibodies (REGN1908–1909) in patients after treatment.

Methods: Patients received REGN1908–1909 (n = 36) or a placebo (n = 37) in a phase 1b study. Fel d 1–induced basophil and IgE-facilitated allergen binding responses were evaluated at baseline and Days 8, 29, and 85. Cytokine and chemokine concentrations in nasal fluids were measured, and REGN1908–1909 inhibition of allergen–IgE binding in patient serum was evaluated.

Measurements and Main Results: Peak serum drug concentrations were concordant with maximal observed clinical response. The anti–Fel d 1 IgE/cat dander IgE ratio in pretreatment serum correlated with Total Nasal Symptom Score improvement. The allergen-neutralizing capacity of REGN1908–1909 was observed in serum and nasal fluid and was detected in an inhibition assay. Type 2 cytokines (IL-4, IL-5, and IL-13) and chemokines (CCL17/TARC, CCL5/RANTES [regulated upon activation, normal T-cell expressed and secreted]) in nasal fluid were inhibited in REGN1908–1909–treated patients compared with placebo (P < 0.05 for all); IL-13 and IL-5 concentrations correlated with Total Nasal Symptom Score improvement. Ex vivo assays demonstrated that REGN1908 and REGN1909 combined were more potent than each alone for inhibiting FcεRI- and FcεRII (CD23)–mediated allergic responses and subsequent T-cell activation.

Conclusions: A single, passive-dose administration of Fel d 1–neutralizing IgG antibodies improved nasal symptoms in cat-allergic patients and was underscored by suppression of FcεRI-, FcεRII-, and T-helper cell type 2–mediated allergic responses.

Clinical trial registered with www.clinicaltrials.gov (NCT02127801)

Induction of IL-10-producing type 2 innate lymphoid cells by allergen immunotherapy is associated with clinical response

The role of innate immune cells in allergen immunotherapy that confers immune tolerance to the sensitizing allergen is unclear. Here, we report a role of interleukin-10-producing type 2 innate lymphoid cells (IL-10⁺ ILC2s) in modulating grass-pollen allergy. We demonstrate that KLRG1⁺ but not KLRG1^- ILC2 produced IL-10 upon activation with IL-33 and retinoic acid. These cells attenuated Th responses and maintained epithelial cell integrity. IL-10⁺ KLRG1⁺ ILC2s were lower in patients with grass-pollen allergy when compared to healthy subjects. In a prospective, double-blind, placebo-controlled trial, we demonstrated that the competence of ILC2 to produce IL-10 was restored in patients who received grass-pollen sublingual immunotherapy. The underpinning mechanisms were associated with the modification of retinol metabolic pathway, cytokine-cytokine receptor interaction, and JAK-STAT signaling pathways in the ILCs. Altogether, our findings underscore the contribution of IL-10⁺ ILC2s in the disease-modifying effect by allergen immunotherapy.

China Consensus Document on Allergy Diagnostics

The prevalence of allergic diseases has increased dramatically in recent years in China, affecting the quality of life in 40% of the population. The identification of allergens is the key to the diagnosis of allergic diseases. Presently, several methods of allergy diagnostics are available in China, but they have not been standardized. Additionally, cross-sensitization and co-sensitization make allergy diagnostics even more complicated. Based on 4 aspects of allergic disease (mechanism, diagnosis procedures, allergen detection in vivo and in vitro as well as the distribution map of the most important airborne allergens in China) and by referring to the consensus of the European Society of Allergy and Clinical Immunology, the World Allergy Organization, and the important literature on allergy diagnostics in China in recent years, we drafted this consensus of allergy diagnostics with Chinese characteristics. It aims to standardize the diagnostic methods of allergens and provides a reference for health care givers. The current document was prepared by a panel of experts from the main stream of professional allergy associations in China.

Clinical and Biological Markers Predict the Efficacy of Glucocorticoid- and Macrolide-Based Postoperative Therapy in Patients With Chronic Rhinosinusitis

BACKGROUND

Although subsequent anti-inflammatory treatments are indispensable for patients with chronic rhinosinusitis (CRS) undergoing sinus surgery, few studies have explored the factors influencing the efficacy of postoperative anti-inflammatory treatment.

OBJECTIVE

We aimed to develop prediction models for the response to glucocorticoid- and macrolide-based postoperative therapy in CRS patients.

METHODS

We performed a post-hoc analysis of our previous study comparing the efficacy of fluticasone propionate and clarithromycin in the postoperative treatment of CRS patients. Clinical characteristics and treatment outcome information were collected. In addition, diseased sinonasal mucosal tissues obtained during surgery were processed for Bio-Plex analysis of protein levels of 34 biomarkers. Classification trees were built to predict refractory CRS based on clinical characteristics and biological markers for patients treated with fluticasone propionate or clarithromycin. A random forest algorithm was used to confirm the discriminating factors that formed the classification trees.

RESULTS

One year after surgery, 22.7% of the patients (17/75) treated with fluticasone propionate, and 24.3% of those (18/74) treated with clarithromycin were diagnosed with refractory CRS. Nasal tissue IL-8 and IgG3 levels and headache VAS scores in the fluticasone propionate group, and nasal tissue IgG4 levels and overall burden of symptoms VAS scores in the clarithromycin group, were identified as discriminating factors forming the classification tree to predict refractory CRS. The overall predictive accuracy of the model was 89.3% and 87.8% for fluticasone propionate- and clarithromycin-based postsurgical treatment, respectively.

CONCLUSIONS

Classification trees built using clinical and biological parameters could be helpful in identifying patients with poor response to fluticasone propionate- and clarithromycin-based postoperative treatment.

Immunogenicity of a new allergoid from Felis domesticus

BACKGROUND

The chemical modification of allergens with glutaraldehyde improves safety while maintaining clinical efficacy, which permits the administration of higher doses of immunotherapy, reducing the risk of adverse reactions. The aim of this study is to evaluate the immunogenic capacity of a new cat dander polymer by immunizing mice and quantifying immunoglobulins in serum, in comparison with the non-modified allergen.

METHODS

The study consists of the immunization of three mice groups with the polymerized and the native extract, together with a negative control group. The immunoglobulin levels in serum have been measured by indirect ELISA. By means of the non-parametric Mann-Whitney U test, it was determined if there were significant differences in the values of specific antibodies between groups.

RESULTS

The group immunized with the allergoid showed significantly higher specific IgG and IgG1 values to dander allergens and specific IgG to the major allergen Fel d 1, while there were no significant changes in IgG2a and IgE values. These results could be due to a higher immunization dose. The vaccine formulation was based on the optimal defined dose for clinical efficacy of allergen immunotherapy.

CONCLUSIONS

This preclinical study carried out with the present assay has established that the allergoid of cat dander extract, as designed for its optimal use in allergen immunotherapy, produces a higher specific IgG than the native extract, in addition to showing significantly higher specific IgG1 levels, evidencing a greater effectiveness in immunization.

EAACI Allergen Immunotherapy User's Guide

Allergen immunotherapy is a cornerstone in the treatment of allergic children. The clinical efficiency relies on a well-defined immunologic mechanism promoting regulatory T cells and downplaying the immune response induced by allergens. Clinical indications have been well documented for respiratory allergy in the presence of rhinitis and/or allergic asthma, to pollens and dust mites. Patients who have had an anaphylactic reaction to hymenoptera venom are also good candidates for allergen immunotherapy. Administration of allergen is currently mostly either by subcutaneous injections or by sublingual administration. Both methods have been extensively studied and have pros and cons. Specifically in children, the choice of the method of administration according to the patient's profile is important. Although allergen immunotherapy is widely used, there is a need for improvement. More particularly, biomarkers for prediction of the success of the treatments are needed. The strength and efficiency of the immune response may also be boosted by the use of better adjuvants. Finally, novel formulations might be more efficient and might improve the patient's adherence to the treatment. This user's guide reviews current knowledge and aims to provide clinical guidance to healthcare professionals taking care of children undergoing allergen immunotherapy.

Induction of IgG2 and IgG4 B-cell memory following sublingual immunotherapy for ryegrass pollen allergy

BACKGROUND

While treatment for atopic rhinitis is aimed mostly to relieve symptoms, only allergen-specific immunotherapy (AIT) is targeted to modify the natural history of allergic diseases. This results in sustained clinical tolerance, even when treatment has stopped. The immunomodulatory effects of AIT are attributed mainly to increased regulatory T-cell function and increased allergen-specific IgG₄ , yet little is known about the effect on the memory B-cell compartment.

OBJECTIVE

We aimed to examine the effects of AIT on the IgE- and IgG subclass-expressing memory B cells.

METHODS

We recruited 29 patients with atopic seasonal rhinoconjunctivitis and performed a longitudinal analysis of the peripheral immune compartment before, during, and after sublingual immunotherapy (SLIT) for allergy to temperate grass pollen, predominantly to ryegrass pollen (RGP; Lolium perenne). Using flow cytometry on peripheral blood mononuclear cells and serum immunoassays, we analyzed the effects of a 4 months preseasonal treatment regimen comprising two or three courses in consecutive years on circulating IgE⁺ and IgG⁺ memory B cells and allergen-specific Ig levels.

RESULTS

SLIT increased RGP-specific serum IgG₂ and IgG₄ , as well as the frequencies of IgG₂ ⁺ and IgG₄ ⁺ memory B cells, whereas no effect was observed on the IgE⁺ memory B-cell compartment. Furthermore, SLIT enhanced proportions of regulatory T cells specific to RGP. These changes were associated with clinical improvement.

CONCLUSION

Our data provide evidence for immunological effects of SLIT on B-cell memory. Skewing responses toward IgG₂ and IgG₄ subclasses might be a mechanism to suppress IgE-mediated allergic responses.

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.

Analysis of the allergenicity and B cell epitopes in tropomyosin of shrimp (Litopenaeus vannamei) and correlation to cross-reactivity based on epitopes with fish (Larimichthys crocea) and clam (Ruditapes philippinarum)

Tropomyosin (TM) is a highly conserved protein that considered as the major allergen of crustacean and mollusk species, while, fish-TM also shares high homology with low allergenicity. In this study, the amino acid sequence, B cell epitopes and allergenicity of shrimp (Litopenaeus vannamei), which is widely consumed, were evaluated by using immunoinformatic tools, dot-blot, enzyme-linked immunosorbent assay (ELISA) and mediator release assay. Meanwhile, cross-reactivity of allergic epitopes of fish-TM, shrimp-TM and clam-TM were assessed. Results showed that three IgE-binding epitopes (X1: 47-61, QKRMQQLENDLDQVQ; X2: 97-108, EDLERSEERLNT and X3: 244-257, RSVQKLQKEVDRLE) of shrimp-TM also exhibited degranulation ability. In comparison with epitopes from shrimp-TM, those from clam-TM showed high cross-reactivity (>80%) and degranulation ability, while those from fish-TM showed low cross-reactivity (<20%). These findings would apply a new understanding of the cross-reactivity of TM from fish, shrimp and clam in terms of allergenic epitopes.

IgE-blocking antibodies following SLIT with recombinant Mal d 1 accord with improved apple allergy

BACKGROUND

We recently reported that 16 weeks of sublingual immunotherapy (SLIT) with recombinant (r) Mal d 1, but not rBet v 1, significantly improved birch pollen-related apple allergy. Allergen-specific IgE-blocking IgG antibodies have been associated with clinical efficacy.

OBJECTIVE

We compared the quantity, quality, and IgE-blocking bioactivity of SLIT-induced Mal d 1-specific IgG antibodies in both treatment groups.

METHODS

Pre- and post-SLIT sera were assessed for rMal d 1-specific IgG antibodies in ELISA and for their ability to inhibit apple allergen-induced upregulation of CD63 on basophils from nontreated individuals with birch pollen-related apple allergy. Post-SLIT sera depleted of IgG1 or IgG4 were compared for their IgE-blocking activity. IgG1 binding to rMal d 1 was competed with rMal d 1 and rBet v 1 in ELISA.

RESULTS

SLIT with rMal d 1 and rBet v 1 induced comparable levels of rMal d 1-specific IgG1, IgG2, IgG3, and IgG4 antibodies. Only post-rMal d 1 SLIT sera displayed IgE-blocking activity, which was significantly reduced by depletion of IgG1 and less so by IgG4 depletion. In competition ELISA, IgG1 binding to Mal d 1 in post-rMal d 1 SLIT sera was fully inhibited with rMal d 1 but not with rBet v 1. Correspondingly, Bet v 1 was the more potent competitor for IgG1 binding to Mal d 1 in post-rBet v 1 SLIT sera.

CONCLUSION

rMal d 1 SLIT for 16 weeks induced functional, primarily Mal d 1-specific IgE-blocking antibodies, whereas rBet v 1 SLIT induced Bet v 1-specific, Mal d 1-cross-reactive IgG antibodies with limited cross-blocking activity. These results provide a possible explanation for the limited effectiveness of birch pollen immunotherapy in birch pollen-related food allergy and indicate a dominant protective role of functional IgE-blocking IgG1 antibodies in the early phase of allergy treatment.

Allergen-specific subcutaneous immunotherapy for Japanese cedar pollinosis decreases the number of metachromatic cells and eosinophils in nasal swabs during the preseason and in season

Background and objective

Nasal symptoms of allergic rhinitis can be reduced with allergen‐specific subcutaneous immunotherapy (SCIT). However, the mechanisms underlying the effectiveness of SCIT for Japanese cedar pollinosis are not well understood. We studied changes in the numbers of metachromatic cells, eosinophils and neutrophils in nasal swabs following SCIT for Japanese cedar pollinosis.

Methods

Subjects were either untreated or given SCIT for 0.5 to 13 years duration. For the 2019 seasons, nasal swabs were taken in the pollinosis preseason (immunotherapy n = 36; untreated control, n = 62) and in the pollinosis season (immunotherapy n = 45; untreated control n = 46) and the numbers of mast cells, eosinophils and neutrophils assessed by microscopy.

Results

There were significant improvements in symptom severities following SCIT in comparison to untreated subjects (P < .0003, the Mann‐Whitney U test) in preseason, and (P < .00001) in season. Metachromatic cell counts from nasal swabs of SCIT subjects in preseason and in the season were lower than those of untreated subjects (P = .0029 and P = .031, respectively). Eosinophil numbers in nasal swabs of subjects given SCIT were lower than in untreated subjects (P = .0031) in season, but not in preseason. There were no significant differences in degrees of neutrophilia between untreated and SCIT subjects in preseason and in season.

Conclusion

One mechanism underlying the effectiveness of SCIT for Japanese cedar pollinosis involves a reduction in the number of metachromatic cells in nasal swabs in the preseason and an inhibition of increases in the number of metachromatic cells and eosinophils in season.

Measurement of Allergen-Specific Inhibitory Antibody Activity

Specific allergen immunotherapy (AIT) is an effective treatment for IgE-mediated allergic diseases and involves T- and B-cell-mediated events. IgE receptors on the surface of antigen-presenting cells facilitate the presentation of allergens in the presence of specific IgE antibody resulting in T-cell activation. Interference with these IgE-dependent mechanisms by "blocking" IgG antibodies suppresses pro-inflammatory Th2 cell responses and manifests as a reduction in allergic responses in vivo.In vitro assays used to measure the inhibition of binding of allergen-IgE complexes have previously utilized proliferation of antigen-specific T-cell clones as an assay readout. Here we describe two simplified assays to measure allergen binding without the complexity of generating T-cell clones. The IgE-facilitated allergen binding assay (IgE-FAB) utilizes flow cytometry to measure the binding of allergen-IgE complexes to EBV-transformed B cells. The enzyme-linked immunosorbent-facilitated antigen binding (ELIFAB) assay uses standard ELISA-based techniques to measure allergen-IgE binding to plate-bound CD23, the low-affinity IgE receptor expressed on B cells.

Allergen Immunotherapy-Induced Immunoglobulin G4 Reduces Basophil Activation in House Dust Mite-Allergic Asthma Patients

It is unclear if allergen immunotherapy (AIT) can reduce allergy effector cell activation. We evaluated the basophil response during Dermatophagoides pteronyssinus (Der p) subcutaneous immunotherapy (SCIT) and its relationship to allergen-specific immunoglobulin G4 (sIgG4) in allergic rhinitis and/or asthma patients. The study included 55 subjects, of which 35 cases received Der p SCIT and 20 controls received standard medications. Symptom and medication scores (SMSs), sIgG4 levels, specific immunoglobulin E (sIgE) levels, allergen-induced basophil activation tests (BATs) in whole blood, and BAT inhibition assays in serum were determined at weeks 0, 4, 12, 16, 52, and 104 of SCIT. Levels of Der p sIgG4 in SCIT patients significantly increased after 12 weeks of treatment compared to week 0. Serum obtained from SCIT patients significantly inhibited basophil activation after 12 weeks of treatment. Removal of immunoglobulin G4 (IgG4) antibodies at week 104 reduced the ability of serum to block basophil activation. An increase of Der p sIgG4 rather than reduction of Der p sIgE correlated with the reduction of basophil activation during SCIT. The sIgG4 antibodies may compete with sIgE binding to allergens to form an immunoglobulin E (IgE)-allergen complex. SCIT reduced the sensitivity of allergen-triggered basophil activation in Der p allergic rhinitis and/or asthma patients through induction of sIgG4.

Allergen-specific IgE levels and the ability of IgE-allergen complexes to cross-link determine the extent of CD23-mediated T-cell activation

Background

CD23 mediates IgE-facilitated allergen presentation and subsequent allergen-specific T-cell activation in allergic patients.

Objective

We sought to investigate key factors regulating IgE-facilitated allergen presentation through CD23 and subsequent T-cell activation.

Methods

To study T-cell activation by free allergens and different types of IgE–Bet v 1 complexes, we used a molecular model based on monoclonal human Bet v 1–specific IgE, monomeric and oligomeric Bet v 1 allergen, an MHC-matched CD23-expressing B-cell line, and a T-cell line expressing a human Bet v 1–specific T-cell receptor. The ability to cross-link Fcε receptors of complexes consisting of either IgE and monomeric Bet v 1 or IgE and oligomeric Bet v 1 was studied in human FcεRI-expressing basophils. T-cell proliferation by monomeric or oligomeric Bet v 1, which cross-links Fcε receptors to a different extent, was studied in allergic patients’ PBMCs with and without CD23-expressing B cells.

Results

In our model non–cross-linking IgE–Bet v 1 monomer complexes, as well as cross-linking IgE–Bet v 1 oligomer complexes, induced T-cell activation, which was dependent on the concentration of specific IgE. However, T-cell activation by cross-linking IgE–Bet v 1 oligomer complexes was approximately 125-fold more efficient. Relevant T-cell proliferation occurred in allergic patients’ PBMCs only in the presence of B cells, and its magnitude depended on the ability of IgE–Bet v 1 complexes to cross-link CD23.

Conclusion

The extent of CD23-mediated T-cell activation depends on the concentration of allergen-specific IgE and the cross-linking ability of IgE-allergen complexes.

Changes in CD4+CD25+FoxP3+ Regulatory T Cells and Serum Cytokines in Sublingual and Subcutaneous Immunotherapy in Allergic Rhinitis with or without Asthma

BACKGROUND

Few studies have directly compared the immunologic responses to specific subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT).

OBJECTIVE

We aimed to directly compare clinical efficacy and immunological responses between SLIT and SCIT in allergic rhinitis (AR) sensitized to house dust mites.

METHODS

Sixty-seven patients (age 5-55 years) with moderate-severe Dermatophagoides pteronyssinus (Der-p) and Dermatophagoides farinae AR with or without asthma were randomized (2:2:1) into SLIT (n = 27), SCIT (n = 26) and placebo (n = 14) groups. Symptom and medication scores, visual analogue score, serum Der-p specific immunoglobulin G4 (Der-p-sIgG4), CD4+CD25+FoxP3+ regulatory T cells (Tregs) and serum cytokines were measured.

RESULTS

After 1-year treatment, a significant improvement of total rhinitis score (TRS), total rhinitis medication score (TRMS) and visual analogue score occurred in both SLIT and SCIT. There were no differences in clinical efficacy except for TRMS (p = 0.026) when SLIT and SCIT were directly compared. CD4+CD25+FoxP3+ Tregs had a trend towards upregulation in the 2 modes and inversely correlated with TRS (p = 0.024) only in SLIT. Der-p-sIgG4 significantly increased in SLIT and SCIT (p < 0.05), and it was 30 times higher in SCIT than SLIT after the treatment (p < 0.05). Serum interferon-γ significantly increased only in SCIT after 1 (p = 0.008), 6 (p = 0.007) and 12 (p = 0.008) months of treatment and inversely correlated with TRS (p = 0.032).

CONCLUSION

While SCIT and SLIT have similar rates of clinical improvement, the 2 modes reveal heterogeneous changes of CD4+CD25+Foxp3+ Tregs, sIgG4 and cytokines.

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.

Hymenoptera Venom Allergy: How Does Venom Immunotherapy Prevent Anaphylaxis From Bee and Wasp Stings?

Hymenoptera stings may cause both local and systemic allergic reactions and even life threatening anaphylaxis. Along with pharmaceutical drugs and foods, hymenoptera venom is one of the most common causes of anaphylaxis in humans. To date, no parameter has been identified that may predict which sensitized people will have a future systemic sting reaction (SSR), however some risk factors, such as mastocytosis and age >40 years are known. Venom immunotherapy (VIT) is the most effective method of treatment for people who had SSR, which is shown to be effective even after discontinuation of the therapy. Development of peripheral tolerance is the main mechanism during immunotherapy. It is mediated by the production of blocking IgG/IgG4 antibodies that may inhibit IgE dependent reactions through both high affinity (FcεRI) and low affinity (FcεRII) IgE receptors on mast cells, basophils and B cells. The generation of antigen specific regulatory T cells produces IL-10 and suppresses Th2 immunity and the immune responses shift toward a Th1-type response. B regulatory cells are also involved in the production of IL-10 and the development of long term immune tolerance. During VIT the number of effector cells in target organs also decreases, such as mast cells, basophils, innate type 2 lymphocytes and eosinophils. Several meta-analyses and randomized controlled studies have proved that VIT is effective for preventing SSR to a sting and improves the quality of life. In this review, the risk of SSR in venom allergy and how VIT changed this risk are discussed.

Role of IL-35 in sublingual allergen immunotherapy

PURPOSE OF REVIEW

Sublingual allergen immunotherapy (SLIT), a disease-modifying treatment for allergic rhinitis, can induce long-term clinical benefits which are mediated by immune responses that include generation of regulatory B (Breg) and T (Treg) cells. The newest member of the IL-12 superfamily, IL-35, is an anti-inflammatory cytokine known to be produced by Breg and Treg cells. Limited studies are available on the role of IL-35 on allergic rhinitis and during SLIT. This review summarizes recent findings relevant to the topic of IL-35 and their role in SLIT.

RECENT FINDINGS

Recombinant IL-35 protein can induce the generation of IL-35-producing Breg and Treg cells with immunosuppressive capacity. Levels of IL-35 and IL-35-inducible Treg (iTR35) cells are dysregulated in allergic rhinitis patients, which can be restored with SLIT. Mechanism of IL-35-mediated tolerance to allergens includes suppressions of T cell proliferation, Th2 cytokine production, and B cell production of IgE antibodies.

SUMMARY

Emerging evidence supports a potential role for IL-35 and iTR35 cells in tolerance maintenance during SLIT. A better understanding for the role of IL-35 and iTR35 cells could provide new avenues for the development of clinical biomarker to assess efficacy of allergen immunotherapy and novel therapeutic strategies for allergic rhinitis.

[Mechanisms of allergen immunotherapy elucidated through integrated comparative analysis]

From the era of subcutaneous immunotherapy (SCIT) in 1960s, allergen immunotherapy (AIT) has been established as a highly effective and curable treatment for allergic diseases. Furthermore, the recent appearance of sublingual immunotherapy (SLIT) in which the complicated administration procedure in SCIT was improved has been causing paradigm shifts in the treatment of allergic rhinitis. During the long history of AIT, the mechanisms by which this therapy leads its strong efficacy have been investigated but not fully clarified yet. The production of blocking antibodies that interrupt allergen-IgE binding, normalization of Th1/Th2 balance, and introduction of regulatory T cells are the major candidate mechanisms, though there are several conflicting reports. In our recent clinical study of SLIT against Japanese cedar pollinosis, we also tried to elucidate its mechanisms. Especially by comparing high-responder and non-responder patients using integrated analysis with multiple data, not by comparing with a placebo control group using individual data, we have successfully identified several target molecules and cascades of SLIT. Herein, we would like to describe the potential mechanisms by which AIT exhibits its strong efficacy with referring our recent novel findings.

Establishment of enzyme-linked immunosorbent facilitated antigen binding as a biomarker assay for Japanese cedar pollen allergy immunotherapy

BACKGROUND

Clinical efficacy of allergen-specific Immunotherapy (AIT) towards Japanese cedar (JC) pollen allergy is firmly established but JC pollen-specific biomarker assays are lacking. Treatment-related increase of allergen-specific antibodies is a robust biomarker of successful AIT. Allergen-specific non-IgE antibodies are believed to reduce the effects of allergen exposure by competing with IgE for allergen binding, and in-vitro assays quantifying the effects of AIT-induced IgE-blocking antibodies are advantageous. A cell-free enzyme-linked immunosorbent facilitated antigen binding (ELIFAB) assay of JC pollen was established.

METHODS

Serum IgE-allergen complexes were captured by immobilized recombinant CD23, and allergen-IgE-CD23 complexes were detected by a biotin-conjugated anti-human IgE antibody. Sera from JC pollen-allergic subjects without or with subcutaneous immunotherapy (SCIT) with JC pollen extract were used (n = 11/group).

RESULTS

Optimal assay conditions were established at 20 μg/mL CD23 and 0.3 μg/mL JC pollen extract, and the dependency on CD23 and IgE was verified. The data show that the JC pollen ELIFAB assay is fit for purpose and demonstrates that the IgE-blocking activity is significantly increased in the JC pollen SCIT group compared with the non-treated group.

CONCLUSION

The JC pollen ELIFAB assay represents a simple, cell-free biomarker assay for monitoring the development of IgE-blocking antibody activity during JC pollen AIT.

Mapping Mimotopes for House Dust Mite Allergen Der f 7 Using a Specific Monoclonal Antibody

BACKGROUND

The dust mite Dermatophagoides farinae is a common worldwide cause of indoor allergies induced by its proteins, including the mid-tier allergen Der f 7.

OBJECTIVE

To identify conformational epitopes in Der f 7 using mimotope mapping and computational modelling.

METHODS

Here, we used standard hybridoma technology to generate 3 new monoclonal antibodies against Der f 7 and performed mimotope mapping by probing a random peptide phage display library. Computational tools, including Minox and the DiscoTope-2.0 Server were used to assess the structure and potential position of antigenic residues within Der f 7.

RESULTS

Thirteen mimotopes sharing the common sequence --XX[LST]P[-E][LI]MLPLR[-S]- were identified. Further, computationally-predicted conformational epitopes were found at residues 1-7, 10, 27, 76-81, 92, and 130-133 of Der f 7, and the key amino acids for these epitopes were deduced to be 2P, 3I, 10E, 27E, 78E, 79E, 81I, 130S, and 132E based on the common mimotope sequence.

CONCLUSION

We identified Der f 7 peptide mimotopes that may model binding sites for blocking antibodies. These may guide the development of immunotherapy for individuals with hypersensitivity to Der f 7.

Allergen-Specific Antibodies Regulate Secondary Allergen-Specific Immune Responses

Immunoglobulin E (IgE)-associated allergy is the most common immunologically-mediated hypersensensitivity disease. It is based on the production of IgE antibodies and T cell responses against per se innocuous antigens (i.e., allergens) and subsequent allergen-induced inflammation in genetically pre-disposed individuals. While allergen exposure in sensitized subjects mainly boosts IgE production and T cell activation, successful allergen-specific immunotherapy (AIT) induces the production of allergen-specific IgG antibodies and reduces T cell activity. Under both circumstances, the resulting allergen-antibody complexes play a major role in modulating secondary allergen-specific immune responses: Allergen-IgE complexes induce mast cell and basophil activation and perpetuate allergen-specific T cell responses via presentation of allergen by allergen presenting cells to T cells, a process called IgE-facilitated antigen presentation (FAP). In addition, they may induce activation of IgE memory B cells. Allergen-induced production of specific IgGs usually exerts ameliorating effects but under certain circumstances may also contribute to exacerbation. Allergen-specific IgG antibodies induced by AIT which compete with IgE for allergen binding (i.e., blocking IgG) inhibit formation of IgE-allergen complexes and reduce activation of effector cells, B cells and indirectly T cells as FAP is prevented. Experimental data provide evidence that by binding of allergen-specific IgG to epitopes different from those recognized by IgE, allergen-specific IgG may enhance IgE-mediated activation of mast cells, basophils and allergen-specific IgE⁺ B cells. In this review we provide an overview about the role of allergen-specific antibodies in regulating secondary allergen-specific immune responses.

The Use of Biomarkers to Predict Aero-Allergen and Food Immunotherapy Responses

The incidence of allergic conditions has continued to rise over the past several decades, with a growing body of research dedicated toward the treatment of such conditions. By driving a complex range of changes in the underlying immune response, immunotherapy is the only therapy that modulates the immune system with long-term effects and is presently utilized for the treatment of several atopic conditions. Recent efforts have focused on identifying biomarkers associated with these changes that may be of use in predicting patients with the highest likelihood of positive clinical outcomes during allergen immunotherapy (AIT), providing guidance regarding AIT discontinuation, and predicting symptomatic relapse and the need for booster AIT after therapy. The identification of such biomarkers in food allergy has the additional benefit of replacing oral food challenges, which are presently the gold standard for diagnosing food allergies. While several markers have shown early promise, research has yet to identify a marker that can invariably predict clinical response to AIT. Skin prick testing (SPT) and specific IgE have commonly been used as inclusion criteria for the initiation of AIT and prediction of reactions during subsequent allergen challenge; however, existing data suggests that changes in these markers are not always associated with clinical improvement and can be widely variable, reducing their utility in predicting clinical response. Similar findings have been described for the use of allergen-specific functional IgG4 antibodies, basophil activation and histamine release, and type 2 innate lymphoid cells. There appears to be a promising association between changes in the expression of dendritic cell-associated markers, as well as the use of DNA promoter region methylation patterns in the prediction of allergy status following therapy. The cellular and molecular changes brought about by immunotherapy are still under investigation, but major strides in our understanding are being made.

Role of Der p 1-specific B cells in immune tolerance during 2 years of house dust mite-specific immunotherapy

BACKGROUND

Long-term follow-up of allergen-specific B cells in terms of immunoglobulin isotype expression, plasmablast differentiation, and regulatory B (Breg) cell development during allergen-specific immunotherapy (AIT) has not been reported.

OBJECTIVE

Allergen-specific B-cell responses during 2 years of house dust mite AIT were compared between responder and nonresponder patients.

METHODS

B cells specific for Der p 1 were detected by using the fluorochrome-labeled allergen method. The frequency of IgA-, IgG₁- and IgG₄-switched Der p 1-specific B cells, plasmablasts, and IL-10- and IL-1 receptor antagonist (IL-1RA)-producing Breg cells were investigated and correlated to clinical response to AIT.

RESULTS

Sixteen of 25 patients completed the 2-year study. Eleven responder patients showed a successful response to AIT, as measured by a decrease in symptom-medication scores from 13.23 ± 0.28 to 2.45 ± 0.24 (P = .001) and a decrease in skin prick test reactivity to house dust mite from 7.0 ± 1.3 to 2.7 ± 0.5 mm (P = .001). IgG₄⁺ and IgA⁺ Der p 1-specific B cells showed a significant increase after AIT, with a significantly greater frequency in responders compared with nonresponders in the IgG₄⁺ but not the IgA⁺ fraction. The frequency of plasmablasts and IL-10- and/or IL-1RA-producing Breg cells was greater among responders compared with nonresponders after 2 years. The increased frequency of Der p 1-specific IgG4⁺ B cells, plasmablasts, and IL-10⁺ and dual-positive IL-10⁺IL-1RA⁺ Breg cells significantly correlated with improved clinical symptoms over the course of AIT.

CONCLUSION

Allergen-specific B cells in patients responding to AIT are characterized by increased numbers of IgA- and IgG₄-expressing Der p 1-specific B cells, plasmablasts, and IL-10⁺ and/or IL-1RA⁺ Breg cells.