Approaches to target IgE antibodies in allergic diseases

The aryl hydrocarbon receptor differentially modulates the expression profile of antibody isotypes in a human B-cell line

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental contaminant and high affinity ligand for the aryl hydrocarbon receptor (AhR). In animal models, AhR activation by TCDD generally inhibits antibody secretion. However, it is less clear if this translates to human antibody production. Using a human Burkitt lymphoma B-cell line (CL-01) that can be stimulated to secrete Ig and undergo class switch recombination to other Ig isotypes, the current study evaluated the effects of AhR activation or antagonism on the human Ig isotypic expression profile with CD40L+IL-4 stimulation. Our results suggest that AhR agonists (TCDD and indirubin) have little to no effect on IgM or IgA secretion, which were also not induced with stimulation. However, AhR activation significantly inhibited stimulation-induced IgG secretion, an effect reversed by the AhR antagonist CH223191. Evaluation of Ig heavy chain (IgH) constant region gene expression (ie Cμ, Cγ1-4, Cα1-2, and Cε that encode for IgM, IgG1-4, IgA1-2, and IgE, respectively) demonstrated differential effects. While Cμ and Cα2 transcripts were unaffected by stimulation or AhR agonists, AhR activation significantly inhibited stimulation-induced Cγ2-4 and Cε mRNA transcripts, which was reversed by AhR antagonism. Notably, AhR antagonism in the absence of exogenous AhR ligands significantly increased IgG and IgA secretion as well as the expression of Cγ2-4 and Cε. These results suggest that modulation of AhR activity differentially alters the IgH isotypic expression profile and antibody secretion that may be partly dependent on cellular stimulation. Since a variety of chemicals from anthropogenic, industrial, pharmaceutical, dietary, and bacterial sources bind the AhR, the ability of environmental exposures to alter AhR activity (i.e. activate or inhibit) may have a direct influence on immune function and antibody-relevant disease conditions.

Safety, Tolerability, Pharmacokinetics, and pharmacodynamics of YH35324, a novel Long-Acting High-Affinity IgETrap-Fc protein in subjects with Atopy: Results from the First-in-Human study

BACKGROUND

YH35324, a long-acting IgETrap-Fc fusion protein, is a novel therapeutic agent for immunoglobulin E (IgE)-mediated allergic diseases. This randomized, double-blind, placebo/active-controlled, single ascending dose Phase 1 study assessed the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of YH35324 in subjects with atopy.

METHODS

Eligible subjects were healthy subjects or atopic adults with mild allergic rhinitis, atopic dermatitis, food allergy, or urticaria, and a serum total IgE level of 30-700 IU/mL (Part A) or > 700 IU/mL (Part B). In Part A, 35 subjects in 5 cohorts received YH35324 (0.3, 1, 3, 6, and 9 mg/kg), 8 received omalizumab (300 mg), and 9 received placebo. In Part B, 8 subjects received YH35324 and 8 received omalizumab.

RESULTS

Twenty subjects (38.5 %) in Part A (YH35324: 37.1 %, omalizumab: 50.0 %, placebo: 33.3 %) and 10 subjects (62.5 %) in Part B (YH35324: 100 %; omalizumab: 25.0 %) experienced treatment-emergent adverse events (TEAEs). TEAEs were mostly grade 1/2; no serious AEs, AE-related treatment discontinuation, or anaphylaxis were reported. YH35324 exhibited dose-proportional increase in Cmax and AUClast over the dose range of 0.3-9 mg/kg. YH35324 rapidly suppressed serum-free IgE levels to a significant extent (< 25 and < 82.8 ng/mL, both P < 0.05) and with longer duration than omalizumab.

CONCLUSION

This study showed that YH35324 has a favorable safety profile and is effective in reducing serum-free IgE levels in subjects with atopic conditions.

A therapeutic strategy to target distinct sources of IgE and durably reverse allergy

Immunoglobulin E (IgE) is a key driver of type 1 hypersensitivity reactions and allergic disorders, which are globally increasing in number and severity. Although eliminating pathogenic IgE may be a powerful way to treat allergy, no therapeutic strategy reported to date can fully ablate IgE production. Interleukin-4 receptor α (IL-4Rα) signaling is required for IgE class switching, and IL-4Rα blockade gradually reduces, but does not eliminate, IgE. The persistence of IgE after IL-4Rα blockade may be due to long-lived IgE+ plasma cells that maintain serological memory to allergens and thus may be susceptible to plasma cell-targeted therapeutics. We demonstrate that transient administration of a B cell maturation antigen x CD3 (BCMAxCD3) bispecific antibody markedly depletes IgE, as well as other immunoglobulins, by ablating long-lived plasma cells, although IgE and other immunoglobulins rapidly rebound after treatment. Concomitant IL-4Rα blockade specifically and durably prevents the reemergence of IgE by blocking IgE class switching while allowing the restoration of other immunoglobulins. Moreover, this combination treatment prevented anaphylaxis in mice. Together with additional cynomolgus monkey and human data, our studies demonstrate that allergic memory is primarily maintained by both non-IgE+ memory B cells that require class switching and long-lived IgE+ plasma cells. Our combination approach to durably eliminate pathogenic IgE has potential to benefit allergy in humans while preserving antibody-mediated immunity.

Therapeutic efficacy of omalizumab in children with moderate-to-severe allergic asthma combined with chronic sinusitis

Background

Omalizumab has been approved for treating moderate-to-severe asthma in children aged over 6 years. Its application to asthmatic children with other allergic diseases has been rarely explored. The present study aims to explore the therapeutic efficacy of omalizumab in children with moderate-to-severe allergic asthma combined with chronic sinusitis.

Methods

The clinical data of children diagnosed with moderate-to-severe allergic asthma combined with chronic sinusitis and treated with omalizumab between September 2020 and April 2022 were retrospectively analyzed. Lung function indexes such as Childhood Asthma Control Test (C-ACT) scores, fractional exhaled nitric oxide (FeNO), and forced expiratory volume in the first second (FEV1) percent predicted (FEV1%pred), small airway function indexes, and the clinical symptoms of chronic sinusitis were analyzed.

Results

A total of 26 children were observed for 16 weeks. After 16 weeks of omalizumab treatment, the significantly increased C-ACT scores (15.57 ± 3.25 points vs. 24.98 ± 5.21 points, F = 15.7112, P < 0.001) and decreased FeNO (31.55 ± 15.57 ppb vs. 19.86 ± 9.80 ppb, F = 4.4265, P = 0.0022), compared with those at baseline, were suggestive of well-controlled symptoms of asthma and improved lung function. FEV1%pred and FEV1/forced vital capacity (FVC) ratio (the ratio of the forced expiratory volume in the first 1 s to the forced vital capacity) increased after omalizumab treatment, although no significant differences were detected (P = 0.9954 and 0.9382, respectively). Peak expiratory flow (PEF) percent predicted (PEF%pred) and forced expiratory flow at 75% of FVC (FEF75%), 50% of FVC (FEF50%), and 25%-75% of FVC (FEF25%-75%) significantly increased after omalizumab treatment (P = 0.0477, <0.001, <0.001, and <0.001, respectively). Visual analog scale scores significantly decreased after omalizumab treatment (6.40 ± 2.98 points vs. 0.85 ± 0.40 points, t = 27.2419, P < 0.001), suggesting alleviation in the clinical symptoms of chronic sinusitis.

Conclusion

In this study, it was found that omalizumab can effectively alleviate clinical symptoms and improve lung function and quality of life in children with moderate-to-severe allergic asthma combined with chronic sinusitis.

Aiming to IgE: Drug development in allergic diseases

The incidence of allergic disease significantly increases in recent decades, causing it become a major public health problem all over the world. The common allergic diseases such as allergic dermatitis, allergy rhinitis, allergic asthma and food allergy are mediated, at least in part, by immunoglobulin E (IgE), and so IgE acts as a central role in allergic diseases. IgE can interact with its high-affinity receptor (FcεRⅠ) which is primarily expressed on tissue-resident mast cells and circulating basophils, initiating intracellular signal transduction and then causing the activation and degranulation of mast cells and basophils. On the other hand, IgE interaction with its low-affinity receptor (CD23), can regulate various IgE-mediated immune responses including IgE-allergen complex presentation, IgE synthesis, the growth and differentiation of both B and T cells, and the secretion of pro-inflammatory mediators. With the deeper mechanism research for allergic diseases, new therapeutic strategies for interfering IgE are developed and receive a great attention. In this review, we summarize a current profile of therapeutic strategies for interfering IgE in allergic diseases. Besides, we suggest that targeting memory B cells (including long-lived plasma cells and (or) IgE⁺ memory B cells) may help to completely control allergic diseases, and highlight that the development of drugs synergistically aiming to multiple targets can be a better choice for improving treatment efficacy which results from allergic diseases as the systemic disorders caused by an impaired immune system.

Feline heartworm disease and environmental allergens hypersensitivity: is there a link?

BACKGROUND

Cats can be infected by Dirofilaria immitis, the causative agent of heartworm disease, characterized by respiratory signs, airway hyperreactivity, remodelling and inflammation. Allergy is a multifactorial pathology, and the role of a number of helminth parasites in the development of allergies in humans and other species has been demonstrated in many studies. The aim of the present study was to verify whether cats seropositive for D. immitis present hypersensitivity to some environmental allergens.

METHODS

Blood samples were collected from 120 cats and tested for the presence of specific immunoglobulin G antibodies against D. immitis and for hypersensitivity to 20 allergens, using commercial allergen test kits.

RESULTS

Of the 120 cats tested, 72 (60.0%) were seropositive for anti-D. immitis IgG and 55 (45.8%) showed clinical signs of heartworm disease of a respiratory nature. The results of testing with the allergen kits showed that 50.8% of cats were seropositive for ≥ 1 allergens, with the most common allergens being Dermatophagoides farinae (25.8%), Dermatophagoides pteronyssinus (20.0%), Malassezia (17.5%) and Ctenocephalides felis (14.2%). The prevalence of allergies was significantly higher-by almost threefold-in cats seropositive for D. immitis (68.1% vs. 25%). There were no significant differences between the prevalence of allergic cats and presence/absence of symptoms, and the results confirmed that symptoms were not a decisive factor for the presence of allergies. The risk for developing allergies was 6.3-fold higher in cats seropositive for D. immitis than in cats that were seronegative, confirming that seropositivity for D. immitis is a risk factor.

CONCLUSIONS

Cats with confirmed heartworm can develop serious respiratory signs, potentially leading to progression to permanent lung injury and predisposing cats to hyperresponsive airway disease. Previous studies have shown that seropositivity for D. immitis and Wolbachia is related to the presence of bronchoconstriction and bronchospasm in the affected cat. The results support the suspicion that contact with D. immitis may be a risk factor for the presence of allergies.

Degranulation of Mast Cells as a Target for Drug Development

Mast cells act as key effector cells of inflammatory responses through degranulation. Mast cell degranulation is induced by the activation of cell surface receptors, such as FcεRI, MRGPRX2/B2, and P2RX7. Each receptor, except FcεRI, varies in its expression pattern depending on the tissue, which contributes to their differing involvement in inflammatory responses depending on the site of occurrence. Focusing on the mechanism of allergic inflammatory responses by mast cells, this review will describe newly identified mast cell receptors in terms of their involvement in degranulation induction and patterns of tissue-specific expression. In addition, new drugs targeting mast cell degranulation for the treatment of allergy-related diseases will be introduced.

Production of monoclonal antibodies for therapeutic purposes: A review

Monoclonal antibodies (mAbs) have been used in the development of immunotherapies that target a variety of diseases, such as cancer, autoimmune diseases, and even viral infections; they play a key role in immunization and are expected after vaccination. However, some conditions do not promote the development of neutralizing antibodies. Production and use of mAbs, generated in biofactories, represent vast potential as aids in immunological responses when the organism cannot produce them on their own, these convey unique specificity by recognizing and targeting specific antigen. Antibodies can be defined as heterotetrametric glycoproteins of symmetric nature, and they participate as effector proteins in humoral responses. Additionally, there are different types of mAbs (murine, chimeric, humanized, human, mAbs as Antibody-drug conjugates and bispecific mAbs) discussed in the present work. When these molecules are produced in vitro as mAbs, several common techniques, such as hybridomas or phage display are used. There are several preferred cell lines that function as biofactories, for the production of mAbs, the selection of which rely on the variation of adaptability, productivity and both phenotypic and genotypic shifts. After the cell expression systems and culture techniques are used, there are diverse specialized downstream processes to achieve desired yield and isolation as well as product quality and characterization. Novel perspectives regarding these protocols represent a potential improvement for mAbs high-scale production.

IgE-neutralizing UB-221 mAb, distinct from omalizumab and ligelizumab, exhibits CD23-mediated IgE downregulation and relieves urticaria symptoms

Over the last 2 decades, omalizumab is the only anti-IgE antibody that has been approved for asthma and chronic spontaneous urticaria (CSU). Ligelizumab, a higher-affinity anti-IgE mAb and the only rival viable candidate in late-stage clinical trials, showed anti-CSU efficacy superior to that of omalizumab in phase IIb but not in phase III. This report features the antigenic-functional characteristics of UB-221, an anti-IgE mAb of a newer class that is distinct from omalizumab and ligelizumab. UB-221, in free form, bound abundantly to CD23-occupied IgE and, in oligomeric mAb-IgE complex forms, freely engaged CD23, while ligelizumab reacted limitedly and omalizumab stayed inert toward CD23; these observations are consistent with UB-221 outperforming ligelizumab and omalizumab in CD23-mediated downregulation of IgE production. UB-221 bound IgE with a strong affinity to prevent FcԑRI-mediated basophil activation and degranulation, exhibiting superior IgE-neutralizing activity to that of omalizumab. UB-221 and ligelizumab bound cellular IgE and effectively neutralized IgE in sera of patients with atopic dermatitis with equal strength, while omalizumab lagged behind. A single UB-221 dose administered to cynomolgus macaques and human IgE (ε, κ)-knockin mice could induce rapid, pronounced serum-IgE reduction. A single UB-221 dose administered to patients with CSU in a first-in-human trial exhibited durable disease symptom relief in parallel with a rapid reduction in serum free-IgE level.

Fluctuations of aeroallergen-specific immunoglobulins and children's allergic profiles: Japan Environment & Children's Study of a pilot cohort

BACKGROUND

Allergen-specific immunoglobulins have a crucial role in allergic diseases. Most wheeze episodes develop before school age, and allergic rhinitis later develops during early elementary school years. However, the clinical background and cytokine/chemokine profiles associated with changes in immunoglobulins during early school-age are poorly understood.

METHODS

This study used blood samples from children participating in the JECS Pilot Study. We examined nineteen kinds of aeroallergen-specific immunoglobulins (IgE, IgG1, IgG4, and IgA) levels in patients at age 6 and age 8. Fluctuations of Der f 1- and Cry j 1-specific immunoglobulins levels during the two periods were compared to assess the frequency of allergic statuses and clusters of cytokine/chemokine profiles.

RESULTS

The medians of aeroallergen-specific IgE levels did not fluctuate, and almost all IgG1 and IgG4 decreased. In IgA, four (e.g., Der f 1) increased, whereas the other four (e.g., Cry j 1) decreased. The ratio of the Der f 1-specific IgG1 level at age 8 to that at age 6 was higher in children with poor asthma control than in children with better asthma control. Moreover, the cytokine/chemokine cluster with relatively lower IL-33 and higher CXCL7/NAP2 was associated with lower Der f 1- and Cry j 1-specific IgG4 levels, but not IgE levels.

CONCLUSIONS

The cluster of cytokine/chemokine profiles characterized by lower IL-33 and higher CXCL7/NAP2 was associated with the maintenance of aeroallergen-specific IgG4 levels. This result provides a basis for considering the control of aeroallergen-specific immunoglobulins.

Human IgE does not bind to human FcRn

The neonatal Fc receptor (FcRn) is known to mediate placental transfer of IgG from mother to unborn. IgE is widely known for triggering immune responses to environmental antigens. Recent evidence suggests FcRn-mediated transplacental passage of IgE during pregnancy. However, direct interaction of FcRn and IgE was not investigated. Here, we compared binding of human IgE and IgG variants to recombinant soluble human FcRn with β2-microglobulin (sFcRn) in surface plasmon resonance (SPR) at pH 7.4 and pH 6.0. No interaction was found between human IgE and human sFcRn. These results imply that FcRn can only transport IgE indirectly, and thereby possibly transfer allergenic sensitivity from mother to fetus.

Extending the capabilities of intact-mass analyses to monoclonal immunoglobulins of the E-isotype (IgE)

Mass spectrometry (MS) has become an indispensable tool in structural characterization and quality control of monoclonal antibodies (mAbs). Intact-mass analysis is a particularly attractive option that provides a powerful and cost-effective means to not only confirm the structural integrity of the protein, but also probe its interactions with therapeutic targets. To a certain extent, this success can be attributed to relatively modest glycosylation levels exhibited by IgG molecules, which limits their structural heterogeneity and enables straightforward mass measurements at the intact molecule level. The recent surge of interest in expanding the repertoire of mAbs to include other classes of immunoglobulins places a premium on efforts to adapt the IgG-tailored experimental strategies to other classes of antibodies, but their dramatically higher levels of glycosylation may create insurmountable obstacles. The monoclonal murine IgE antibody explored in this work provides a challenging model system, as its glycosylation level exceeds that of conventional IgG mAbs by a factor of nine. The commercial sample, which included various IgE fragments, yields a poorly resolved ionic signal in intact-mass measurements, from which little useful information can be extracted. However, coupling MS measurements with the limited charge reduction of select polycationic species in the gas phase gives rise to well-defined charge ladders, from which both ionic masses and charges can be readily determined. The measurements reveal significant variation of the extent of glycosylation within intact IgE molecules, as well as the presence of low-molecular weight impurities in the commercial IgE sample. Furthermore, incubation of the monoclonal IgE with its antigen (ovalbumin) gives rise to the formation of complexes with varying stoichiometries, which can also be uniquely identified using a combination of native MS, limited charge reduction in the gas phase and data fitting procedures. This work demonstrates that following appropriate modifications, intact-mass analysis measurements can be successfully applied to mAbs beyond the IgG isotype, providing a wealth of information not only on the mass distribution of the intact IgE molecules, but also their large-scale conformational integrity, the integrity of their covalent structure, and their interactions with antigens.

IgE and TGF-β Signaling: From Immune to Cardiac Remodeling

Cardiac remodeling is accompanied by cardiac hypertrophy, fibrosis, and dysfunction, eventually leading to heart failure (HF). However, the molecular mechanisms involved in cardiac remodeling are complicated, especially the association with immune. Immunoglobulin E (IgE) is a class of immunoglobulins involved in immune response to specific allergens. Recently, Zhao et al characterized a novel specific role of IgE and its high affinity receptor (FcεR1) in directly promoting pathological myocardial remodeling and cardiac dysfunction. Additionally, upon blocking IgE-FcεR1 signaling using FcεR1 genetic depletion or by administrating the anti-IgE monoclonal antibody omalizumab (Oma) in mice, they observed that cardiac hypertrophy and cardiac interstitial fibrosis induced by angiotensin II (Ang II) or transverse aortic constriction (TAC) were significantly suppressed. In contrast, IgE administration alone can aggravate pathological cardiac remodeling and dysfunction. RNA-seq and downstream analysis indicated that TGF-β was the common pathway and the most pivotal mediator in IgE-FcεR1-induced cardiac remodeling and dysfunction. Furthermore, the administration of a TGF-β inhibitor could ameliorate cardiac remodeling and improve cardiac function. Therefore, these findings suggest that IgE-FcεR1 maybe promising therapeutic targets for cardiac remodeling and provide an experimental basis for the use of omalizumab for HF patients combined with high serum IgE levels or allergic diseases.

Omalizumab Effectiveness in Severe Allergic Asthma with Multiple Allergic Comorbidities: A Post-Hoc Analysis of the STELLAIR Study

Background

Immunoglobulin (Ig) E-mediated pathophysiological mechanisms are common in allergic diseases including severe allergic asthma (SAA). The anti-IgE monoclonal antibody omalizumab may be particularly beneficial for patients with SAA and multiple allergic comorbidities (AC) including perennial/seasonal rhinitis, conjunctivitis, atopic dermatitis (AD), and food allergy.

Methods

We conducted a post-hoc analysis of the patients from the STELLAIR study (n=872, 149 minors and 723 adults). The patients were classified based on the presence of multiple AC (≥3 AC or <3 AC) or AD as assessed by questionnaire. Response to omalizumab was assessed after 4-6 months (T_4-6) and after 12 months (T₁₂). Asthma response at T_4-6 was based on global evaluation of treatment effectiveness, reduction of ≥40% in annual exacerbation rate, and a combination of both. Asthma response at T₁₂ was based on change in yearly exacerbation and hospitalization rates. AC improvement at T₁₂ was based on patient perception.

Results

Patients with ≥3 AC demonstrated a higher combined response to omalizumab (74.7% vs 58.3%) at T_4-6 and had reduced yearly exacerbation and hospitalization rates (88.9% vs 77.4% and -94.0% vs -70.5%, respectively). Patients with ≥3 AC were more likely to show an improvement in their AC (85.3% vs 51.9%) at T₁₂. Results were similar in minors and adults. The presence of AD was associated with greater omalizumab effectiveness at T_4-6 and a greater AC improvement at T₁₂. Improvement of AD and food allergies at T₁₂ were 73.2% and 38.7%, respectively, in the population overall.

Conclusion

This post-hoc analysis of the STELLAIR study shows that omalizumab is beneficial for all SAA patients and especially for patients with multiple AC or AD. In patients with ≥3 AC, omalizumab also improved AC outcomes.

Low-affinity but high-avidity interactions may offer an explanation for IgE-mediated allergen cross-reactivity

Background

Allergy is a global disease with overall frequencies of >20%. Symptoms vary from irritating local itching to life‐threatening systemic anaphylaxis. Even though allergies are allergen‐specific, there is a wide range of cross‐reactivities (eg apple and latex) that remain largely unexplained. Given the abilities of low‐affinity IgG antibodies to inhibit mast cells activation, here we elucidate the minimal affinity of IgE antibodies to induce type I hypersensitivity.

Methods

Three mature (high‐affinity) IgE antibodies recognizing three distinct epitopes on Fel d 1, the major cat allergen, were back‐mutated to germline conformation, resulting in binding to Fel d 1 with low affinity. The ability of these IgE antibodies to activate mast cells in vitro and in vivo was tested.

Results

We demonstrate that affinities as low as 10⁻⁷ M are sufficient to activate mast cells in vitro and drive allergic reactions in vivo. Low‐affinity IgE antibodies are able to do so, since they bind allergens bivalently on the surface of mast cells, leading to high‐avidity interactions.

Conclusions

These results suggest that the underlying mechanism of allergen cross‐reactivity may be low‐affinity but high‐avidity binding between IgE antibodies and cross‐reactive allergen.

Targeted Therapy for Chronıc Spontaneous Urtıcarıa: Ratıonale and Recent Progress

Chronic spontaneous urticaria (CSU) is characterized by the presence of wheals, angioedema, or both for at least 6 weeks. It may persist for a long time-up to 50% of the patients have been reported to be symptomatic 5 years after the onset. Some patients can suffer more than one episode of CSU during their lifetime. Considering the recurrences, disabling symptoms, and significant impact on quality of life, proper and effective treatment of CSU is critical. The use of antihistamines (AHs) is still the mainstay of treatment. However, given the low rates of response to AHs (38.6% and 63.2% to standard doses and higher doses, respectively), the complete control of symptoms seems difficult to attain. The use of omalizumab for CSU has been a major breakthrough in the care of patients with CSU. However, the partial response and lack of response to omalizumab in a subgroup of patients, as high as 70% in some studies, make the development of alternative treatments desirable. Ever-increasing knowledge on the pathogenesis is making new target molecules available and enabling drug development for CSU. In addition to drug repurposing as in anti-IL-4/13, IL-5, and IL-17 antibodies, novel targeted therapy options such as ligelizumab and Bruton's tyrosine kinase inhibitors are currently undergoing clinical trials and will be available in the near future. This article reviews the current challenges in the treatment of CSU, the pathogenesis and potential target molecules, and the rationale for novel treatments and their rapidly developing status.

The Association Between Asthma and Risk of Myasthenia Gravis: A Systematic Review and Meta-analysis

PURPOSE

This study aimed to investigate the association between asthma and risk of myasthenia gravis (MG) using the method of systematic review and meta-analysis.

METHODS

Potentially eligible studies were identified from Medline and EMBASE databases from inception to July 2020 using search strategy that comprised terms for "Asthma" and "Myasthenia Gravis". Eligible cohort study must consist of one cohort of individuals with asthma and another cohort of individuals without asthma. Then, the study must report relative risk (RR) with 95% confidence intervals (95% CIs) of incident MG between the groups. Eligible case-control studies must include cases with MG and controls without MG. Then, the study must explore their history of asthma. Odds ratio (OR) with 95% CIs of the association between asthma status and MG must be reported. Point estimates with standard errors were retrieved from each study and were combined together using the generic inverse variance method.

RESULTS

A total of 6,835 articles were identified. After two rounds of independent review by five investigators, two cohort studies and three case-control studies met the eligibility criteria and were included into the meta-analysis. Pooled analysis showed that asthma was significantly associated with risk of MG with the pooled risk ratio of 1.38 (95% CI 1.02-1.86). Funnel plot was symmetric, which was not suggestive of publication bias.

CONCLUSION

The current study found a significant association between asthma and increased risk of MG.

Use of biologics in allergen immunotherapy

Biologics are drugs that are derived or synthesized from biological sources. A particular class are recombinant monoclonal antibodies. Their targeted application against distinct molecules of intercellular communication is of significant relevance in the treatment of tumor, inflammatory, or allergic diseases. But also in the context of allergen immunotherapy (AIT) they can be of special value. This is exemplified by the anti-IgE antibody omalizumab, which allows to achieve allergen tolerance in patients suffering from severe allergic reactions and increased risk of AIT-induced anaphylaxis. Furthermore, omalizumab administration during AIT effectively lowers the rsik of allergic side effects. This is demonstrated by a variety of studies and case reports of patients suffering either form respiratory, food, or insect venom allergy. Besides a direct blocking of IgE-mediated effects, T-cellular immune mechanisms might also be involved. Another interesting option is the applcation of recombinant IgG antibodes directed against specific epitopes of an allergen. Similar to AIT-induced IgG antibodies they can prevent the binding of allergens to IgE-antibodes as well as the hereby elicited allergic reactions.

IgE in the pathophysiology and therapy of food allergy

Food allergy is becoming a major public health issue, with no regulatory approved therapy to date. Food allergy symptoms range from skin rash and gastrointestinal symptoms to anaphylaxis, a potentially fatal systemic allergic shock reaction. IgE antibodies are thought to contribute importantly to key features of food allergy and anaphylaxis, and measurement of allergen-specific IgE is fundamental in diagnosing food allergy. This review will discuss recent advances in the regulation of IgE production and IgE repertoires in food allergy. We will describe the current understanding of the role of IgE and its high-affinity receptor FcεRI in food allergy and anaphylaxis, by reviewing insights gained from analyses of mouse models. Finally, we will review data derived from clinical studies of the effect of anti-IgE therapeutic monoclonal antibodies (mAbs) in food allergy, and recent insight on the efficiency and mechanisms through which these mAbs block IgE effector functions.

Prediction of clinical response to omalizumab in moderate-to-severe asthma patients using the change in total serum IgE level

Background

Omalizumab (OMA) is an effective anti-immunoglobulin E (IgE) treatment for moderate-to-severe asthma. However, predicting an individual’s response is difficult. Monitoring change of total serum IgE may be useful for predicting the response to OMA. The purpose of this study was to determine if measuring the change in total IgE level could predict the response to OMA in patients with moderate-to-severe asthma.

Methods

This study included 25 patients (11 females and 14 males; mean age =46.1 years; mean pre-bronchodilator FEV1% =67.8%) with moderate-to-severe asthma. All patients were treated with OMA, and total IgE serum concentrations were measured at baseline before treatment (median baseline total serum IgE =210 IU/mL) and at 4 weeks after beginning treatment. Patients were divided into responders (i.e., excellent or good response) and non-responders (i.e., moderate or poor response) using the global treatment effectiveness (GETE) response method after 16 weeks of treatment. The characteristics of responders and non-responders were compared, and receiver operating characteristic (ROC) curve analysis was used to determine the ability of change in IgE level to predict treatment response.

Results

There were 20 responders (80%) and 5 non-responders (20%), and responders demonstrated better improvements of asthma control test (ACT) and asthma control questionnaire (ACQ) scores, and reduction of oral corticosteroid use as compared with non-responders. Twenty-one patients had a total serum IgE 4-week-to-baseline ratio ≥2, and 20 of the patients responded to OMA. The area under the ROC curve (AUC) for baseline IgE level for predicting treatment response was 0.53 (95% CI: 0.18–0.88), and that of the week 4 IgE level was 0.69 (95% CI: 0.42–0.96). Using a cutoff value of 2, the 4-week: baseline IgE ratio achieved the highest AUC of 0.87 (95% CI: 0.64–1), with a sensitivity and specificity of 100% and 80%, respectively, for predicting treatment response.

Conclusions

A total week 4 serum IgE level:baseline level ratio ≥2 can predict the response to OMA in patients with moderate-to-severe asthma after 16 weeks of treatment with high likelihood. Monitoring changes of total IgE level in asthma patients treated OMA may be useful for predicting clinical response.

An Omalizumab Biobetter Antibody With Improved Stability and Efficacy for the Treatment of Allergic Diseases

The critical role of IgE in allergic diseases is well-documented and clinically proven. Omalizumab, a humanized anti-IgE antibody, was the first approved antibody for the treatment of allergic diseases. Nevertheless, omalizumab still has some limitations, such as product instability and dosage restriction in clinical application. In this study, we attempted to develop an omalizumab biobetter antibody with the potential to overcome its limitations. We removed two aspartic acid isomerization hotspots in CDRs of omalizumab to improve antibody candidate’s stability. Meanwhile, several murine amino acids in the framework region of omalizumab were replaced with human source to reduce the potential immunogenicity. Yeast display technology was then applied to screen antibody candidates with high binding affinity to IgE. Moreover, YTE mutation in Fc fragment was introduced into the candidates for extending their serum half-life. A lead candidate, AB1904Am15, was screened out, which showed desired biophysical properties and improved stability, high binding affinity and elevated potency in vitro, prolonged half-life in human FcRn transgenic mouse, and enhanced in vivo efficacy in cynomolgus monkey asthma model. Overall, our study developed a biobetter antibody of omalizumab, AB1904Am15, which has the potential to show improved clinical benefit in the treatment of allergic diseases.

The anti-IgE mAb omalizumab induces adverse reactions by engaging Fcγ receptors

Omalizumab is an anti-IgE monoclonal antibody (mAb) approved for the treatment of severe asthma and chronic spontaneous urticaria. Use of omalizumab is associated with reported side effects ranging from local skin inflammation at the injection site to systemic anaphylaxis. To date, the mechanisms through which omalizumab induces adverse reactions are still unknown. Here, we demonstrated that immune complexes formed between omalizumab and IgE can induce both skin inflammation and anaphylaxis through engagement of IgG receptors (FcγRs) in FcγR-humanized mice. We further developed an Fc-engineered mutant version of omalizumab, and demonstrated that this mAb is equally potent as omalizumab at blocking IgE-mediated allergic reactions, but does not induce FcγR-dependent adverse reactions. Overall, our data indicate that omalizumab can induce skin inflammation and anaphylaxis by engaging FcγRs, and demonstrate that Fc-engineered versions of the mAb could be used to reduce such adverse reactions.

Cornus officinalis Ethanolic Extract with Potential Anti-Allergic, Anti-Inflammatory, and Antioxidant Activities

Atopic dermatitis (AD) is an allergic and chronic inflammatory skin disease. The present study investigates the anti-allergic, antioxidant, and anti-inflammatory activities of the ethanolic extract of Cornus officinalis (COFE) for possible applications in the treatment of AD. COFE inhibits the release of β-hexosaminidase from RBL-2H3 cells sensitized with the dinitrophenyl-immunoglobulin E (IgE-DNP) antibody after stimulation with dinitrophenyl-human serum albumin (DNP-HSA) in a concentration-dependent manner (IC₅₀ = 0.178 mg/mL). Antioxidant activity determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidant power assay, and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging activity, result in EC₅₀ values of 1.82, 10.76, and 0.6 mg/mL, respectively. Moreover, the extract significantly inhibits lipopolysaccharide (LPS)-induced nitric oxide (NO) production and the mRNA expression of iNOS and pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) through attenuation of NF-κB activation in RAW 264.7 cells. COFE significantly inhibits TNF-α-induced apoptosis in HaCaT cells without cytotoxic effects (p < 0.05). Furthermore, 2-furancarboxaldehyde and loganin are identified by gas chromatography/mass spectrometry (GC-MS) and liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis, respectively, as the major compounds. Molecular docking analysis shows that loganin, cornuside, and naringenin 7-O-β-D-glucoside could potentially disrupt the binding of IgE to human high-affinity IgE receptors (FceRI). Our results suggest that COFE might possess potential inhibitory effects on allergic responses, oxidative stress, and inflammatory responses.

Dirofilaria immitis Could Be a Risk Factor for the Development of Allergic Diseases in Humans

Simple Summary

Heartworm is a parasitic infection transmitted by mosquitoes to animals and humans. The risk of human infections is high in those areas with high canine prevalence, such as the Canary Islands. In these islands, there is also a high number of allergic inhabitants. Since some studies have shown a relationship between parasite infections and development of allergies, the aim of this study was to evaluate whether exposure to heartworm may contribute to the development of allergies. A survey carried out on dog owners in the Canary Islands showed that 51.3% of allergic owners had a heartworm-positive dog, and significant differences were found between allergic or not-allergic owners, according to whether the dog was negative or positive to heartworm. Furthermore, 66 serum samples from inhabitants of the Canary Islands were analyzed for the presence of unspecific allergy markers (Immunoglobulin E or IgE) and specific for heartworm (IgE against Dirofilaria immitis and Wolbachia) and the results show that people who were in contact with heartworm showed total IgE and specific IgE against heartworm more frequently. Contact with heartworm may be a risk factor for the development of allergic diseases, although further studies to elucidate the relationship between heartworm and allergies should be carried out.

Abstract

The Canary Islands are hyperendemic for canine heartworm and the risk of zoonotic infection is high. Additionally, there is evidence of development of allergies due to nematode infections in animals and humans. Since the population of the Canary Islands presents high prevalence of allergic comorbidities, and previous studies have shown a possible relationship between allergies and seropositivity to heartworm, the aim was to evaluate whether exposure to heartworm may contribute to the development of allergies in the human population. First, an epidemiological study was conducted on 248 owners of dogs with/without heartworm infection in the Canary Islands. Secondly, a serological analysis of the presence of total IgE and specific IgE against heartworm was conducted in 66 samples of inhabitants of the Canary Islands. The survey showed that allergic owners had heartworm-positive dogs more frequently (p < 0.01). Of the analyzed human samples, 43.9% were seropositive to heartworm and Wolbachia. Total IgE concentrations were increased in 34.5% seropositive samples and 8.1% seronegative samples. Specific IgE against heartworm was only found in human seropositive samples (17.2%). Contact with heartworm may be a risk factor for the development of allergic diseases, although further studies to elucidate the relationship between heartworm and allergies should be carried out.

Past, present, and future of anti-IgE biologics

About 20 years after the identification of immunoglobulin E (IgE) and its key role in allergic hypersensitivity reactions against normally harmless substances, scientists have started inventing strategies to block its pathophysiological activity in 1986. The initial concept of specific IgE targeting through the use of anti-IgE antibodies has gained a lot of momentum and within a few years independent research groups have reported successful generation of first murine monoclonal anti-IgE antibodies. Subsequent generation of optimized chimeric and humanized versions of these antibodies has paved the way for the development of therapeutic anti-IgE biologicals as we know them today. With omalizumab, there is currently still only one therapeutic anti-IgE antibody approved for the treatment of allergic conditions. Since its application is limited to the treatment of moderate-to-severe persistent asthma and chronic spontaneous urticaria, major efforts have been undertaken to develop alternative anti-IgE biologicals that could potentially be used in a broader spectrum of allergic diseases. Several new drug candidates have been generated and are currently assessed in pre-clinical studies or clinical trials. In this review, we highlight the molecular properties of past and present anti-IgE biologicals and suggest concepts that might improve treatment efficacy of future drug candidates.

IgE Effector Mechanisms, in Concert with Mast Cells, Contribute to Acquired Host Defense against Staphylococcusaureus

Allergies are considered to represent mal-directed type 2 immune responses against mostly innocuous exogenous compounds. Immunoglobulin E (IgE) antibodies are a characteristic feature of allergies and mediate hypersensitivity against allergens through activation of effector cells, particularly mast cells (MCs). Although the physiological functions of this dangerous branch of immunity have remained enigmatic, recent evidence shows that allergic immune reactions can help to protect against the toxicity of venoms. Because bacteria are a potent alternative source of toxins, we assessed the possible role of allergy-like type 2 immunity in antibacterial host defense. We discovered that the adaptive immune response against Staphylococcus aureus (SA) skin infection substantially improved systemic host defense against secondary SA infections in mice. Moreover, this acquired protection depended on IgE effector mechanisms and MCs. Importantly, our results reveal a previously unknown physiological function of allergic immune responses, IgE antibodies, and MCs in host defense against a pathogenic bacterium.

Non-tuberculous mycobacterial infection and reactive dermatosis associated with adult-onset immunodeficiency due to anti-interferon-gamma autoantibodies: A case report

INTRODUCTION

Anti-interferon-gamma (anti-IFN-γ) autoantibody increases susceptibility to lower-virulence pathogens and causes immunodeficiency syndrome in HIV-negative patients.

PATIENT CONCERNS

A 69-year-old Chinese man presented with a 2-month history of pruritic skin lesions on his forearms, trunk, and legs. He was diagnosed with 5 opportunistic infections without conventional immunosuppression-associated factors in past. The most conspicuous characteristics were recurrent pulmonary infection, persistent immunoglobulin E elevation and eosinophilia during the whole disease course.

DIAGNOSIS

Enzyme-linked immunosorbent assay showed anti-IFN-γ autoantibody positive. The final diagnosis for the patient was adult-onset immunodeficiency due to anti-IFN-γ autoantibody, non-tuberculous mycobacterial (NTM) infection and reactive dermatosis.

INTERVENTIONS

The patient underwent long-term anti-NTM and corticosteroid maintenance treatment.

OUTCOMES

The patient was followed for 2 years during which opportunistic infection no longer happened, the immunoglobulin E level and eosinophil count reduced, the autoantibody levels remained largely steady and lung lesions absorbed.

CONCLUSION

Clinicians should be vigilant for NTM infection in patients with anti-IFN-γ autoantibodies, even when culture results are negative. Long-term anti-non-tuberculous mycobacteria and glucocorticoid regimens were effective.

The mechanistic and functional profile of the therapeutic anti-IgE antibody ligelizumab differs from omalizumab

Targeting of immunoglobulin E (IgE) represents an interesting approach for the treatment of allergic disorders. A high-affinity monoclonal anti-IgE antibody, ligelizumab, has recently been developed to overcome some of the limitations associated with the clinical use of the therapeutic anti-IgE antibody, omalizumab. Here, we determine the molecular binding profile and functional modes-of-action of ligelizumab. We solve the crystal structure of ligelizumab bound to IgE, and report epitope differences between ligelizumab and omalizumab that contribute to their qualitatively distinct IgE-receptor inhibition profiles. While ligelizumab shows superior inhibition of IgE binding to FcεRI, basophil activation, IgE production by B cells and passive systemic anaphylaxis in an in vivo mouse model, ligelizumab is less potent in inhibiting IgE:CD23 interactions than omalizumab. Our data thus provide a structural and mechanistic foundation for understanding the efficient suppression of FcεRI-dependent allergic reactions by ligelizumab in vitro as well as in vivo.

Immunoglobulin E (IgE) plays a central role in allergic responses, yet therapeutic targeting of IgE with antibodies such as omalizumab is met with various limitations. Here the authors characterize the molecular properties and crystal structure of a new anti-IgE antibody, ligelizumab, for mechanistic insights related to its enhanced suppression activity.

Correlated dynamics of serum IGE and IGE+ clonotype count with allergen air level in seasonal allergic rhinitis

Mechanisms of maintenance of immunological memory in the chronic course of seasonal allergic rhinitis remain poorly understood. The detailed understanding of these mechanisms is required for design of new approaches for allergy treatment. It is known that the level of allergen-specific IgE antibodies (sIgE), which play a key role in the development of the disease, is increased in patients with seasonal allergic rhinitis during pollination season. This study aimed to investigate the dynamics of serum IgE levels and characteristics of the clonal repertoire of IgE-secreting lymphocytes depending on the intensity of the patient's contact with the allergen. For three patients, allergic to birch pollen (22, 22, and 28 y.o.), we measured total IgE and birch pollen specific IgE levels at 6 time points with 2 week interval during the birch pollination season. Immunoglobulin heavy chain gene (IGH) clonal repertoire data for several B-cell subpopulations at different time points were obtained for one patient. We observe growth of the sIgE level (91%, 37%, and 64% compared to the baseline) at the peak of pollination season in all three donors. Initial increase in sIgE and IgE levels coincides with the birch pollination initiation; sIgE and total IgE levels correlate with the birch pollen air level (sIgE: R2 = 0.98 at p < 0.05; total IgE: R2 = 0.95 at p < 0.05). We detected IgE clonotypes only in samples obtained during the birch pollination, which indicates an increase of IGE-expressing cells concentration during this period. The frequency of IgE clonotypes was extremely low compared to that of the clonotypes of other isotypes (IgE — 0.01%, IgM — 48.4%, IgD — 14%, IgG — 17.4%, IgA — 19.8%). Hypermutation and phylogenetic analysis of the sequences from the 13 detected IgE-containing clonal groups showed that these IgE clonotypes could originate from IgG as a result of sequential isotype-switching.

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.

Influence of prolonged treatment with omalizumab on the development of solid epithelial cancer in patients with atopic asthma and chronic idiopathic urticaria: A systematic review and meta-analysis

OBJECTIVE

We investigated whether prolonged treatment with omalizumab influences development or progression of solid epithelial cancer in patients with atopic asthma or chronic idiopathic urticaria.

DESIGN

Systematic review and meta-analysis of intervention and observational studies. Randomized controlled trials were assessed for risk of bias using the Cochrane Risk of Bias tool, comparative observational studies were assessed using the Newcastle-Ottawa Scale, and non-comparative observational studies were assessed using the Joanna Briggs Institute Checklist for Prevalence Studies.

DATA SOURCES

We searched MEDLINE, EMBASE, Cochrane Library and grey literature for eligible studies to November 2017. All searches were updated in January 2019.

ELIGIBILITY CRITERIA FOR INCLUDED STUDIES

Randomized, quasi-randomized, controlled clinical trials and observational studies were included if they involved patients ≥ 12 years with moderate-to-severe persistent asthma or chronic idiopathic urticaria treated with omalizumab for ≥ 40 weeks. Eligible comparators included standard of care, placebo, cromoglycate or no treatment.

RESULTS

One hundred and sixty seven unique studies were eligible for inclusion; however, only twelve (7.2%, n = 11 758) reported any outcome of interest, none of which involved patients with urticaria. 195 cancer events were reported. We found no statistically significant increase in the odds of study-emergent solid epithelial cancer in patients randomized to long-term treatment with omalizumab compared to standard of care (Peto OR: 0.65, 95% CI: 0.11, 3.74, I²  = 41%). Less than one per cent of participants of non-comparative observational studies (n = 2350) were diagnosed with a solid epithelial tumour (meta-proportion: 0.86% [95% CI: 0.24, 1.86%, I²  = 56%]). In the only comparative observational study reporting on cancer, the proportion of study-emergent solid epithelial tumour events was nearly identical in both study groups (omalizumab: 2.3%, standard of care: 2.2%).

CONCLUSIONS

There is insufficient evidence to determine whether long-term treatment with omalizumab influences development or progression of solid epithelial cancer in these patient populations. PROSPERO registration # CRD 42018082211.

Species Specificity on Interaction between IgE and FcεRI

Allergic diseases are one of the most prevalent diseases at present, it is imperative to understanding the pathophysiology and treatment strategies for allergic diseases. In this process, the binding of IgE and FcεRI on effector cells plays a critical role in triggering allergic reactions. However, the species specificity of the interaction between IgE and FcεRI has not been clearly explained. This review described the characteristics and the interaction mechanism in the allergic reaction of IgE and FcεRI and summarized the species specificity between IgE and FcεRI.

Scrodentoid A Inhibits Mast Cell-Mediated Allergic Response by Blocking the Lyn-FcεRIβ Interaction

Background: Mast cells are considered an attractive therapeutic target for treating allergic diseases, and the Lyn–FcεRIβ interaction is essential for mast cell activation. This study investigated the antiallergic effect of scrodentoid A (SA) on mast cells and mast cell–mediated anaphylaxis.

Methods: For in vitro experiments, mast cells were treated with SA. Cell proliferation was tested using the XTT assay. The mRNA expression of various cytokines and chemokines was measured using qPCR. The levels of histamine, eicosanoids (PGD₂, LTC₄), and cytokines were measured using enzyme immunoassay kits. Signaling was investigated using Western blotting and immunoprecipitation. For in vivo experiments, the antiallergic activity of SA was evaluated using two mouse models of passive anaphylaxis as passive cutaneous and systemic anaphylaxis. The mechanism was investigated through immunohistochemistry and immunofluorescence.

Results: SA considerably inhibited immunoglobulin (Ig) E-mediated mast cell activation, including β-hexosaminidase release, mRNA and protein expression of various cytokines, and PGD₂ and LTC₄ release_. Oral administration of SA effectively and dose-dependently suppressed mast cell–mediated passive cutaneous and systemic anaphylaxis. SA significantly attenuated the activation of Lyn, Syk, LAT, PLCγ, JNK, Erk1/2, and Ca²⁺ mobilization without Fyn, Akt, and P38 activation by blocking the Lyn–FcεRIβ interaction.

Conclusions: SA suppresses mast cell–mediated allergic response by blocking the Lyn–FcεRIβ interaction in vitro and in vivo. SA may be a promising therapeutic agent for allergic and other mast cell–related diseases.

IgE-Mediated Multimorbidities in Allergic Asthma and the Potential for Omalizumab Therapy

Allergic asthma often coexists with different pathological conditions, called multimorbidities, that are mostly of allergic nature and share a common underlying inflammatory pathophysiological mechanism. Multimorbidities of allergic asthma may influence asthma control, its severity, and patients' response to treatment, and contribute to the overall socioeconomic burden of the disease. Immunoglobulin E (IgE) is known to play a central role in the pathogenesis of various allergic diseases, including asthma. Thus, IgE-mediated immunologic pathways present an attractive target for intervention in asthma and multimorbidities. In this review, we discuss the most frequently reported IgE-mediated multimorbidities in allergic asthma, including allergic rhinitis, rhinoconjunctivitis, atopic dermatitis, vernal keratoconjunctivitis, chronic rhinosinusitis with nasal polyps, food allergies, and allergic bronchopulmonary aspergillosis. Omalizumab is a recombinant humanized monoclonal antibody against IgE and has been in use to treat allergic asthma for more than a decade. We comprehensively review the clinical evidence for omalizumab in the treatment of the aforementioned multimorbidities in allergic asthma.

Receptor-destroying enzyme (RDE) from Vibrio cholerae modulates IgE activity and reduces the initiation of anaphylaxis

IgE plays a key role in allergies by binding to allergens and then sensitizing mast cells through the Fc receptor, resulting in the secretion of proinflammatory mediators. Therefore, IgE is a major target for managing allergies. Previous studies have reported that oligomannose on IgE can be a potential target to inhibit allergic responses. However, enzymes that can modulate IgE activity are not yet known. Here, we found that the commercial receptor-destroying enzyme (RDE) (II) from Vibrio cholerae culture fluid specifically modulates IgE, but not IgG, and prevents the initiation of anaphylaxis. RDE (II)-treated IgE cannot access its binding site on bone marrow-derived mast cells, resulting in reduced release of histamine and cytokines. We also noted that RDE (II)-treated IgE could not induce passive cutaneous anaphylaxis in mouse ears. Taken together, we concluded that RDE (II) modulates the IgE structure and renders it unable to mediate allergic responses. To reveal the mechanism by which RDE (II) interferes with IgE activity, we performed lectin microarray analysis to unravel the relationship between IgE modulation and glycosylation. We observed that RDE (II) treatment significantly reduced the binding of IgE to Lycopersicon esculentum lectin, which recognizes poly-N-acetylglucosamine and poly-N-acetyllactosamine. These results suggest that RDE (II) specifically modulates branched glycans on IgE, thereby interfering with its ability to induce allergic responses. Our findings may provide a basis for the development of drugs to inhibit IgE activity in allergies.

Current Strategies to Inhibit High Affinity FcεRI-Mediated Signaling for the Treatment of Allergic Disease

Allergies and asthma are a major cause of chronic disease whose prevalence has been on the rise. Allergic disease including seasonal rhinitis, atopic dermatitis, urticaria, anaphylaxis, and asthma, are associated with activation of tissue-resident mast cells and circulating basophils. Although these cells can be activated in different ways, allergic reactions are normally associated with the crosslinking of the high affinity Fc receptor for Immunoglobulin E, FcεRI, with multivalent antigen. Inflammatory mediators released from cytoplasmic granules, or biosynthesized de novo, following FcεRI crosslinking induce immediate hypersensitivity reactions, including life-threatening anaphylaxis, and contribute to prolonged inflammation leading to chronic diseases like asthma. Thus, inappropriate or unregulated activation of mast cells and basophils through antigenic crosslinking of FcεRI can have deleterious, sometimes deadly, consequences. Accordingly, FcεRI has emerged as a viable target for the development of biologics that act to inhibit or attenuate the activation of mast cells and basophils. At the forefront of these strategies are (1) Anti-IgE monoclonal antibody, namely omalizumab, which has the secondary effect of reducing FcεRI surface expression, (2) Designed Ankyrin Repeat Proteins (DARPins), which take advantage of the most common structural motifs in nature involved in protein-protein interactions, to inhibit FcεRI-IgE interactions, and (3) Fusion proteins to co-aggregate FcεRI with the inhibitory FcγRIIb. This review presents the published research studies that support omalizumab, DARPins, and fusion proteins as, arguably, the three most currently viable strategies for inhibiting the expression and activation of the high affinity FcεRI on mast cells and basophils.