Structural and Physical Basis for Anti-IgE Therapy

Abrogation and homeostatic restoration of IgE responses by a universal IgE allergy CTL vaccine-The three signal self/non-self/self (S/NS/S) theory

Natural IgE cytotoxic peptides (nECPs), which are derived from the constant domain of the heavy chain of human IgE producing B cells via endoplasmic reticulum (ER) stress, are decorated onto MHC class 1a molecules (MHCIa) as unique biomarkers for CTL (cytotoxic T lymphocyte)-mediated immune surveillance. Human IgE exhibits only one isotype and lacks polymorphisms; IgE is pivotal in mediating diverse, allergen-specific allergies. Therefore, by disrupting self-IgE tolerance via costimulation, the CTLs induced by nECPs can serve as universal allergy vaccines (UAVs) in humans to dampen IgE production mediated by diverse allergen-specific IgE-secreting B cells and plasma cells expressing surface nECP-MHCIa as targets. The study herein has enabled the identification of nECPs, A32 and SP-1/SP-2 nonameric natural peptides produced through the correspondence principle. Vaccination using nECP induced nECP-specific CTL that profoundly suppressed human IgE production in vitro as well as chimeric human IgE production in human IgE/HLA-A2.01/HLA-B7.02 triple transgenic rodents. Furthermore, nECP-tetramer-specific CTLs were found to be converted into CD4 Tregs that restored IgE competence via the homeostatic principle, mediatepred by SREBP-1c suppressed DCs. Thus, nECPs showed causal efficacy and safety as UAVs for treating categorically type I hypersensitivity IgE-mediated allergies. The applied vaccination concept presented provides the foundation to unify, integrate through a singular class of tetramer-specific TCR clonotypes for regulaing human IgE production. The three signal theory pertains to mechanisms of three cells underlying central tolerance (S), breaking self tolerance (NS) and regaining peripheral tolerance (S) via homeostasis concerning nECP as an efficacious and safe UAV to treat type I IgE-mediated hypersensitivity. The three signal theory impirically extended, may be heuritic for immuno-regulation of adaptive immune repertoire in general.

Solar Urticaria: An Ambispective Study in a Long-term Follow-up Cohort with Emphasis on Therapeutic Predictors and Outcomes

Solar urticaria is a rare photodermatosis with several unknown pathogenic, clinical and therapeutic aspects. This study analysed the clinical and therapeutic features of a long-term follow-up solar urticaria cohort, with a focus on omalizumab management and outcomes, and characterized omalizumab response with the use of the high-affinity immunoglobulin E (IgE) receptor (FcεRI) and the Urticaria Control Test. An observational, unicentric, ambispective study was conducted from 2007 to 2023. Solar urticaria was diagnosed in 41 patients with a median follow-up of 60 months. Thirteen patients were prescribed omalizumab, with a median treatment time of 48 months. A significant decrease in FcεRI baseline levels and subsequent median increase in Urticaria Control Test was evidenced after omalizumab prescription in all patients. Drug survival at 48 months was at 88.9%. Omalizumab stepping-down protocol led to sustained omalizumab discontinuation in only 1 patient. Median basal Urticaria Control Test was lower (p < 0.01) in patients who were prescribed omalizumab and in patients without remission. This study contributes to our knowledge of omalizumab outcomes in real-life clinical practice and highlights the pathogenic importance of IgE-mediated pathways in solar urticaria, where FcεRI emerges as a possible biomarker of omalizumab response.

Type 2 Biomarkers for the Indication and Response to Biologics in CRSwNP

PURPOSE OF REVIEW

Three biologics targeting type 2 inflammation have been approved for the treatment of severe and uncontrolled chronic rhinosinusitis with nasal polyps (CRSwNP). Nevertheless, around 40-60% of patients do not respond well to these biological treatments. Selecting appropriate patients is crucial to improve treatment outcome of biologics. This review summarizes the literature data on type 2 biomarkers, with a specific focus on the indication to biologics for severe CRSwNP.

RECENT FINDINGS

No consensus has been reached on how to define mucosal type 2 inflammation in CRSwNP. Clinical markers (e.g., 22-item Sino-nasal Outcome Test (SNOT-22) score, Lund-Mackay CT score (LMS), ethmoid/maxillary sinus CT score, and CT-radiomics), nasal secretion biomarkers (e.g., eosinophil cationic protein and interleukin-5), blood and nasal cytology eosinophil counts, and nasal swab eosinophil peroxidase activity have been reported to be associated with type 2 inflammation in CRSwNP. The time duration since the last surgery, SNOT-22 score at 1 week of treatment, and baseline serum osteoprotegerin levels might indicate the response to dupilumab. LMS and asthma control test scores were found to have moderate predictive value for acceptable improvement after 24-week treatment of omalizumab. High blood eosinophil levels at baseline were associated with treatment response to mepolizumab and benralizumab. Although several clinical and biological markers might be associated with type 2 inflammation and response to biologics in patients with CRSwNP, their validity requires further investigation. Identifying clinically applicable biomarkers for biologic treatment holds significant promise for advancing personalized approaches to biologics and optimizing treatment outcomes for patients with CRSwNP.

Autoreactive IgE: Pathogenic role and therapeutic target in autoimmune diseases

Autoimmunity is the break of tolerance to self-antigens that leads to organ-specific or systemic diseases often characterized by the presence of pathogenic autoreactive antibodies (AAb) produced by plasmablast and/or plasma cells. AAb are prevalent in the general population and not systematically associated with clinical symptoms. In contrast, in some individuals, these AAb are pathogenic and drive the development of signs and symptoms of antibody-mediated autoimmune diseases (AbAID). AAb production, isotype profiles, and glycosylations are promoted by pro-inflammatory triggers linked to genetic, environmental, and hormonal parameters. Recent evidence supports a role for pathogenic AAb of the IgE isotype in a number of AbAID. Autoreactive IgE can drive the activation of mast cells, basophils, and other types of FcεRI-bearing cells and may play a role in promoting autoantibody production and other pro-inflammatory pathways. In this review, we discuss the current knowledge on the pathogenicity of autoreactive IgE in AbAID and their status as therapeutic targets. We also highlight unresolved issues including the need for assays that reproducibly quantify IgE AAbs, to validate their diagnostic and prognostic value, and to further study their pathophysiological contributions to AbAID.

Abrogation and Homeostatic Restoration of IgE Responses by a Universal IgE Allergy CTL Vaccine-The Three Signal Self/Non-Self/Self (S/NS/S) Model

Natural IgE cytotoxic peptides (nECPs), which are derived from the constant domain of the heavy chain of human IgE producing B cells via endoplasmic reticulum (ER) stress, are decorated onto MHC class 1a molecules (MHCIa) as unique biomarkers for CTL (cytotoxic T lymphocyte)-mediated immune surveillance. Human IgE exhibits only one isotype and lacks polymorphisms; IgE is pivotal in mediating diverse, allergen-specific allergies. Therefore, by disrupting self-IgE tolerance via costimulation, the cytotoxic T lymphocytes (CTLs) induced by nECPs can serve as universal allergy vaccines (UAVs) in humans to dampen IgE production mediated by diverse allergen-specific IgE- secreting B cells and plasma cells expressing surface nECP-MHCIa as targets. The study herein has enabled the identification of nECPs produced through the correspondence principle 1, 2 . Furthermore, nECP-tetramer-specific CTLs were found to be converted into CD4 Tregs that restored IgE competence via the homeostatic principle, mediated by SREBP-1c suppressed DCs. Thus, nECPs showed causal efficacy and safety as UAVs for treating type I hypersensitivity IgE-mediated allergies. The applied vaccination concept presented provides the foundation to unify, integrate through a singular class of tetramer-specific TCR clonotypes. The three signal model is proposed on the mechanisms underlying central tolerance, breaking tolerance and regaining peripheral tolerance via homeostasis concerning nECP as an efficacious and safe UAV to treat type I IgE-mediated hypersensitivity.

One Sentence Summary

Human IgE self-peptides are identified as universal allergy vaccines that inhibit IgE synthesis while allowing homeostatic IgE recovery.Graphic abstract textThree cell S/NS/S model of Universal Allergy Vaccines (UAV): Natural IgE peptides (nECPs) presented by enabler DCs break central IgE tolerance (Self), leading to CTLs that inhibit IgE production (Non-self). Generative DCs converted by the metabolic milieu transform the pre-existing nECP-specific CTLs into nECP-specific Tregs leading to homeostatic recovery of IgE competence (S).

Response to Omalizumab as an Add-On Therapy in the Treatment of Allergic Asthma in Adult Chinese Patients-A Retrospective Study

(a) Background: Omalizumab is an anti-IgE humanized monoclonal antibody marketed in China for the conventional treatment of poorly controlled moderate-to-severe allergic asthma. Numerous clinical trials have demonstrated the effectiveness of omalizumab, but the data from studies in actual clinical treatment are still relatively limited. (b) Methods: Thirty-two patients with moderate-to-severe allergic asthma treated with omalizumab on the basis of ICS-LABA (inhaled corticosteroids/long-acting beta2-agonist) were selected. Clinical characteristics before and after treatment were collected to analyze the relationship between changes in serum total IgE levels and peripheral blood EOS (eosinophil) levels, FEV1 (forced expiratory volume in 1 second), PEF (peak expiratory flow), OCS (oral glucocorticoid) dosage, ATC (asthma control test) score, and the number of acute exacerbations and the treatment response, in order to observe the efficacy of omalizumab in addition to primary therapy, and to investigate whether baseline clinical characteristics such as serum total IgE and EOS levels could predict a treatment response. (c) Results: Using the ACT score as an evaluation, 68.75% of patients benefited from omalizumab treatment at the end of 16 weeks. The response group has a reduction in OCS dosage (p-values of 0.026 and 0.039), a significant reduction in ACT scores (both p < 0.001), and a reduction in the number of acute exacerbations (p = 0.034 and 0.025, respectively) after omalizumab treatment. The binary logistics analysis of factors affecting the effectiveness of omalizumab in the treatment of allergic asthma were total serum IgE and the presence of comorbidities (p-values of 0.039 and 0.046, respectively). (d) Conclusions: Combining omalizumab with ICS-LABA for 16 weeks significantly improves asthma symptoms in Chinese adults and can be used as an add-on treatment. In addition, high serum IgE levels and the presence of comorbidities were predictors of its therapeutic efficacy.

Efficient Strategy to Design Protease Inhibitors: Application to Enterovirus 71 2A Protease

One strategy to counter viruses that persistently cause outbreaks is to design molecules that can specifically inhibit an essential multifunctional viral protease. Herein, we present such a strategy using well-established methods to first identify a region present only in viral (but not human) proteases and find peptides that can bind specifically to this "unique" region by maximizing the protease-peptide binding free energy iteratively using single-point mutations starting with the substrate peptide. We applied this strategy to discover pseudosubstrate peptide inhibitors for the multifunctional 2A protease of enterovirus 71 (EV71), a key causative pathogen for hand-foot-and-mouth disease affecting young children, along with coxsackievirus A16. Four peptide candidates predicted to bind EV71 2A protease more tightly than the natural substrate were experimentally validated and found to inhibit protease activity. Furthermore, the crystal structure of the best pseudosubstrate peptide bound to the EV71 2A protease was determined to provide a molecular basis for the observed inhibition. Since the 2A proteases of EV71 and coxsackievirus A16 share nearly identical sequences and structures, our pseudosubstrate peptide inhibitor may prove useful in inhibiting the two key pathogens of hand-foot-and-mouth disease.

Pharmacological Management of Allergic Rhinitis: A Consensus Statement from the Malaysian Society of Allergy and Immunology

The goal of allergic rhinitis (AR) management is to achieve satisfactory symptom control to ensure good quality of life. Most patients with AR are currently treated with pharmacotherapy. However, knowledge gaps on the use of pharmacotherapy still exist among physicians, particularly in the primary care setting, despite the availability of guideline recommendations. Furthermore, it is common for physicians in the secondary care setting to express uncertainty regarding the use of new combination therapies like intranasal corticosteroid plus antihistamine combinations. Inadequate treatment leads to significant reduction of quality of life that affects daily activities at home, work, and school. With these concerns in mind, a practical consensus statement was developed to complement existing guidelines on the rational use of pharmacotherapy in both the primary and secondary care settings.

Therapeutic Strategies of Biologics in Chronic Rhinosinusitis: Current Options and Future Targets

Chronic rhinosinusitis is a chronic inflammatory disease of the upper airways, for which treatment options include medical or surgical therapy. However, there are limitations to conservative treatment strategies, such as the relapse of nasal polyps. In this review, we discuss the rising role of biomolecular mechanisms associated with various biologics that have been approved or are undergoing clinical trials to treat chronic rhinosinusitis. We also highlight the potential molecular therapeutic targets for managing and treating chronic rhinosinusitis.

Clinical and biological markers in disease and biologics to treat chronic rhinosinusitis

PURPOSE OF REVIEW

Chronic rhinosinusitis (CRS) is a heterogeneous disorder with diverse responses to conventional anti-inflammatory medical and surgical treatments. Even for the newly developed mAbs targeting type 2 (T2) reaction, a considerable number of patients with CRS with nasal polyps (CRSwNP) exhibited unsatisfying response. Identifying patients with a tendency to poor prognosis is critical for selecting targeted therapies to improve the treatment outcome. This review focuses on clinical and biological markers associated with prognosis of CRS patients under conventional medical and surgical treatments and provides an update summary of potential markers for T2 biologics.

RECENT FINDINGS

Allergic rhinitis, asthma, prior sinus surgery, nasal polyps, tissue eosinophilia and neutrophilia, blood eosinophilia and high levels of Charcot-Leyden crystal, cystatin SN, chemokine (C-C motif) ligand 17, macrophage inflammatory protein-1β and interleukin (IL)-5 in nasal secretions have been associated with poor prognosis in CRS patients under conventional medical and surgical treatments. Blood eosinophil level might be a biomarker for anti-IL-5 (mepolizumab) and anti-IL-5R (benralizumab) biologic in patients with refractory CRSwNP.

SUMMARY

Several clinical and biological markers have been associated with poor response to conventional treatments in CRS patients; however, majority of them should be verified by large-scale multicentre studies. More efforts are needed to identify biomarkers for biologics.

Combining Anti-IgE Monoclonal Antibodies and Oral Immunotherapy for the Treatment of Food Allergy

Immunoglobulin E (IgE)-mediated food allergy is a real public health problem worldwide. The prevalence of food allergy is particularly high in children. Patients with food allergy experience high morbidity with a change in quality of life due to the risk of severe anaphylaxis. Current treatment options are poor. Allergen avoidance is widely recommended but exposes patients to accidental ingestion. Oral immunotherapy is also used in patients with food allergies to the most common allergens. Oral immunotherapy consists of a daily administration of small, gradually increasing amounts of allergens to induce desensitisation. This procedure aims at inducing immune tolerance to the ingested food allergens. However, some patients experience adverse reactions and discontinue oral immunotherapy.Given that IgE plays a crucial role in food allergy and anti-IgE are effective in allergic asthma, the use of anti-IgE therapeutic monoclonal antibodies (mAbs) such as omalizumab has been assessed in food allergy patients. The use of omalizumab as a monotherapy in food allergy has not been extensively studied but looks promising. There is more published evidence regarding the effect of omalizumab and oral immunotherapy in food allergy. Given the promising results of oral immunotherapy regarding sustained tolerance in clinical trials and the potential capacity of omalizumab to reduce symptoms in case of accidental exposure, a strategy combining oral immunotherapy with omalizumab pre-treatment has been suggested as a safer option in patients with severe food allergy compared to isolated therapy. Omalizumab seems useful in ensuring safer administration of oral immunotherapy with the oral immunotherapy maintenance dose being reached more rapidly. Quality-of-life improvement is greater with oral immunotherapy + omalizumab compared to oral immunotherapy alone. Moreover, sustained unresponsiveness is achieved more frequently with omalizumab. Considering that precision medicine and personalised therapy are major goals for allergic diseases, predictive biomarkers are crucial in order to identify food allergy patients more likely to benefit from anti-IgE therapies.

The role of omalizumab in the treatment of chronic rhinosinusitits with nasal polyposis

Introduction: Chronic rhinosinusitis with nasal polyposis (CRSwNP) poses a significant healthcare challenge, with diminished quality of life for patients and high costs and resource utilization for disease management. The understanding of CRSwNP pathophysiology has progressed with identification of various inflammatory biomarkers and subsequent development of monoclonal antibodies that target the underlying mechanisms of inflammation.Areas covered: Omalizumab is a biologic agent for CRSwNP treatment that targets immunoglobulin (Ig)-E. The US FDA has approved the use of omalizumab as an add-on biologic therapy for nasal polyposis in December 2020. Two Phase III clinical trials, POLYP 1 and POLYP 2, have shown that omalizumab improves both subjective patient-reported outcomes and objective physician-evaluated metrics for CRSwNP. Ongoing studies are still exploring the efficacy, safety, and cost-effectiveness of biologics for CRSwNP.Expert opinion: Biologics will continue develop as a viable management option for CRSwNP. Omalizumab is regarded as a promising addition to current treatment strategies for refractory disease.

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.

Biotherapy and treatment of adult primary chronic rhinosinusitis with nasal polyps: Cellular and molecular bases

The present article reviews the molecular and cellular mechanisms involved in the pathophysiology of chronic rhinosinusitis with nasal polyps (CRSwCRSwNP) and underlying the action mechanisms of biotherapies. Biotherapy uses substances naturally produced by the organism or their specific antagonists targeting a proinflammatory mechanism. CRSwCRSwNP is a form of chronic rhinosinusitis (CRS), which is classically subdivided in to 2 types according to the presence of polyps. In recent years, the concept of endotypes emerged, with a more exhaustive definition of the types of CRS according to inflammatory mechanism, with a view to developing personalized treatments. CRSwNP pathophysiology is poorly understood. Polyps arise from a primary epithelial lesion in a context of chronic local inflammation, mainly type 2 in Europe, implicating eosinophils, IgE, Th2 cytokines (IL-4/IL-13, IL-5) and T and B cells. Biotherapy seems promising in CRSwNP. The present review details the various pathophysiological pathways underlying the action mechanisms of biotherapies, and the various published studies, assessing efficacy and mode of action in the treatment of CRSwNP.

Chronic Rhinosinusitis with Nasal Polyps: Targeting IgE with Anti-IgE Omalizumab Therapy

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a complex, clinically heterogeneous and persistent inflammatory disorder of the upper airway. Detailed mechanistic insights into disease pathogenesis are lacking, but it is now accepted that local tissue IgE driven T2-high inflammatory pathways are critical to disease. The recent CRSwNP Phase 3 POLYP1 and POLYP2 replicate studies of blocking IgE with omalizumab confirmed rapid improvements in all clinical parameters of sinonasal disease, confirming a pivotal role for IgE driven inflammatory pathways in CRSwNP. This review summarises the biology of IgE in relation to CRSwNP. Insight into how IgE may drive CRSwNP is evaluated in the context of clinical improvements seen with omalizumab. The need for further studies using a broader patient and biomarker specific groups to aid more precise drug-patient selection alongside more detailed mechanistic studies of omalizumab in CRSwNP is highlighted.

Functional and Structural Characterization of a Potent C1q Inhibitor Targeting the Classical Pathway of the Complement System

The classical pathway of complement is important for protection against pathogens and in maintaining tissue homeostasis, but excessive or aberrant activation is directly linked to numerous pathologies. We describe the development and in vitro characterization of C1qNb75, a single domain antibody (nanobody) specific for C1q, the pattern recognition molecule of the classical pathway. C1qNb75 binds to the globular head modules of human C1q with sub-nanomolar affinity and impedes classical pathway mediated hemolysis by IgG and IgM. Crystal structure analysis revealed that C1qNb75 recognizes an epitope primarily located in the C1q B-chain that overlaps with the binding sites of IgG and IgM. Thus, C1qNb75 competitively prevents C1q from binding to IgG and IgM causing blockade of complement activation by the classical pathway. Overall, C1qNb75 represents a high-affinity nanobody-based inhibitor of IgG- and IgM-mediated activation of the classical pathway and may serve as a valuable reagent in mechanistic and functional studies of complement, and as an efficient inhibitor of complement under conditions of excessive CP activation.

Omalizumab treatment in adolescents with chronic spontaneous urticaria: Efficacy and safety

BACKGROUND

Omalizumab is useful as an add-on treatment in patients unresponsive to high doses of second-generation antihistamines. This study aimed to evaluate the efficacy and safety of omalizumab treatment in adolescents with refractory chronic spontaneous urticaria (CSU).

METHODS

CSU patients aged 12-18 years old with the diagnosis of symptomatic CSU and unresponsive to classical treatment were included in the study. All patients had an urticaria-activity-score (UAS7) of ≥16 or and were treated with 300mg omalizumab every four weeks. The degree of response was classified into complete, partial and non-responders due to UAS7.

RESULTS

A total of 29 patients were evaluated. The median age and symptom onset age of the patients was 15.2 (IQR, 12.8-16.5) years and 14.0 (IQR, 11.8-15.9) years, respectively. The median duration of urticaria was eight (IQR, 4-24) months at admission. Eleven (37.9%) patients had angioedema and ten (34.5%) patients had concomitant allergic diseases. The median age at the beginning of treatment with omalizumab was 15.4 (IQR, 12.9-16.9) years. The median symptom duration was 12 (IQR, 6.5-27.5) months before the omalizumab treatment. Twenty-eight (96.5%) of the patients (89.6% complete, 6.9% partial) achieved response; however, one patient was a non-responder (3.5%). The adverse effect was observed in one (3.4%) patient as angioedema after the third dose. Twenty-three patients were followed up for a median of 18 (IQR, 13-27) months. Relapse was observed in three (13%) patients.

CONCLUSIONS

Omalizumab is considered as an effective and safe treatment for CSU in adolescents. Relapses mostly occur within the first year after the cessation of treatment.

Engineering the Fab fragment of the anti-IgE omalizumab to prevent Fab crystallization and permit IgE-Fc complex crystallization

Immunoglobulin E (IgE) plays a central role in the allergic response, in which cross-linking of allergen by FcεRI-bound IgE triggers mast cell and basophil degranulation and the release of inflammatory mediators. The high-affinity interaction between IgE and FcεRI is a long-standing target for therapeutic intervention in allergic disease. Omalizumab is a clinically approved anti-IgE monoclonal antibody that binds to free IgE, also with high affinity, preventing its interaction with FcεRI. All attempts to crystallize the pre-formed complex between the omalizumab Fab and the Fc region of IgE (IgE-Fc), to understand the structural basis for its mechanism of action, surprisingly failed. Instead, the Fab alone selectively crystallized in different crystal forms, but their structures revealed intermolecular Fab/Fab interactions that were clearly strong enough to disrupt the Fab/IgE-Fc complexes. Some of these interactions were common to other Fab crystal structures. Mutations were therefore designed to disrupt two recurring packing interactions observed in the omalizumab Fab crystal structures without interfering with the ability of the omalizumab Fab to recognize IgE-Fc; this led to the successful crystallization and subsequent structure determination of the Fab/IgE-Fc complex. The mutagenesis strategy adopted to achieve this result is applicable to other intractable Fab/antigen complexes or systems in which Fabs are used as crystallization chaperones.

The use of biologics in children with allergic rhinitis and chronic rhinosinusitis: Current updates

The therapeutic goals of the treatment of allergic rhinitis (AR) and chronic rhinosinusitis (CRS) are symptom relief, avoiding complications, and improving quality of life. In the treatment of AR and CRS, several limitations of currently prescribed medicines have been identified. Antihistamine administration (both oral and topical) together with intranasal corticosteroids bring relief to the majority of patients, but their dependency on the medications and a necessity to maintain strict compliance with regular medication regimes pose a challenge. Immunotherapeutic agents are an option in some patients, but polysensitized patients, the risk of anaphylaxis, and the need for daily administration for years are limiting it from becoming the main therapy modality. Immunotherapy in any form requires commitment by the patient, which renders adherence and compliance issues particularly relevant. The procedure involved are generally time-consuming and entail an associated risk of severe adverse reactions. The use of biologics could overcome the limitations of other therapeutic modalities. They could be used as a monotherapy or combined with pre-existing medications. The benefits of targeted therapy include less adverse effects and optimal efficacy. The aim of the present review was to investigate the collective literature to date pertaining to the role of biologics in managing children with AR and CRS.

Atopic Patients Show Increased Interleukin 4 Plasma Levels but the Degree of Elevation Is Not Sufficient to Upregulate Interleukin-4-Sensitive Genes

BACKGROUND

Atopic diseases constitute a major health challenge for industrialized countries, and elevated levels of interleukin 4 (IL-4) frequently characterize these disorders. Previous in vitroanalyses have indicated that IL-4 strongly upregulates the expression of IL-4-sensitive genes in human monocytes.

OBJECTIVE

To explore whether similar expression alterations may contribute to the pathomechanisms of atopic diseases in vivo we carried out a small-scale case-control clinical study (n = 43), in which we quantified the plasma levels of IgE and IL-4 as well as the expression of selected IL-4-sensitive genes in blood leukocytes.

METHODS

34 allergic patients suffering from allergic rhinitis (n = 11), atopic eczema (n = 11) and allergic asthma (n = 12) as well as 9 healthy control individuals were recruited. IgE and IL-4 plasma levels were determined by ELISA, and the expression of selected IL-4-sensitive gene products in blood leukocytes was quantified by qRT-PCR. In addition, the fatty acid oxygenase activity of isolated monocytes was measured by RP-HPLC analysis of the arachidonic acid oxygenation products (ex vivo activity assays).

RESULTS

We found that plasma levels of IgE and IL-4 were significantly elevated in atopic patients but the degree of elevation was not sufficient to upregulate the expression of the selected IL-4-sensitive genes in circulating leukocytes. Moreover, the arachidonic acid oxygenase activity of blood monocytes was not significantly altered in atopic patients.

CONCLUSION

Our data suggest that the IL-4 plasma levels of atopic patients are not high enough to impact the expression of IL-4-sensitive genes.

Biological therapies for atopic dermatitis: An update

Severe atopic dermatitis, which affects both adults and children, is a debilitating disorder with a significant decline of patients' quality of life. Although aetiopathogenic factors are currently a topic of study and interpretation, the main features of atopic eczema are skin barrier disturbance and immune dysregulation. Severe refractory disease that fails to improve with conventional therapy may benefit from biologic therapy. Progress in understanding immunopathology of atopic dermatitis have allowed identification of therapeutic molecular targets in the field of biological therapy. We reviewed the different biological treatments with a focus on novel targeted agents: Systemic immunotherapy (Omalizumab, Dupilumab, Lebrikizumab, Tralokinumab, Nemolizumab, Ustekinumab, Fezakinumab, Tezepelumab, Apremilast, allergen specific immunotherapy), and topical agents (Tofacitinib, Crisaborole).

Chronic rhinosinusitis with nasal polyps: insights into mechanisms of disease from emerging biological therapies

Introduction: Chronic rhinosinusitis with nasal polyps (CRSwNP) is a complex disease of the upper airway, with long-term morbidity. With detailed mechanistic studies currently lacking, understanding of the immunopathogenesis is still limited. However, outcomes from CRSwNP clinical studies using biologics that block key mediators or cells may provide some insights into how immune signaling pathways potentially integrate and modulate each other and contribute to disease. Current treatments are often ineffective and there is an urgent unmet clinical need for effective therapeutic strategies. Emerging biologics hold promise. Areas covered: This review covers the biology of CRSwNP in terms of the clinical outcomes reported from blocking immune cascades with available biologics. Immune amplification mechanisms and how biologics can potentially modulate such 'master' cytokines and signaling proteins that drive inflammation and contribute to tissue remodeling in CRSwNP are discussed. Expert commentary: Biologics have the potential to transform CRSwNP treatment. The ability to predict clinical response in a complex disease as CRSwNP to a biologic cannot necessarily be predicted by measuring a single protein or cell as a biomarker of disease. Further studies with biologics must be carefully undertaken to fully evaluate wider biomarker associated pheno-endotype responses along with any associated asthma outcome measures.

Approaches to target IgE antibodies in allergic diseases

IgE is the antibody isotype found at the lowest concentration in the circulation. However IgE can undeniably play an important role in mediating allergic reactions; best exemplified by the clinical benefits of anti-IgE monoclonal antibody (omalizumab) therapy for some allergic diseases. This review will describe our current understanding of the interactions between IgE and its main receptors FcεRI and CD23 (FcεRII). We will review the known and potential functions of IgE in health and disease: in particular, its detrimental roles in allergic diseases and chronic spontaneous urticaria, and its protective functions in host defense against parasites and venoms. Finally, we will present an overview of the drugs that are in clinical development or have therapeutic potential for IgE-mediated allergic diseases.

Immunoglobulin Glycosylation Effects in Allergy and Immunity

PURPOSE OF REVIEW

The aim of this review will be to familiarize the reader with the general area of antibody (Ab) glycosylation and to summarize the known functional roles of glycosylation and how glycan structure can contribute to various disease states with emphasis on allergic disease.

RECENT FINDINGS

Both immunoglobulin (Ig) isotype and conserved Fc glycosylation sites often dictate the downstream activity of an Ab where complexity and degree of glycosylation contribute to its ability to bind Fc receptors (FcRs) and activate complement. Most information on the effects of glycosylation center on IgG in cancer therapy and autoimmunity. In cancer therapy, glycosylation modifications that enhance affinity for activating FcRs are utilized to facilitate immune-mediated tumor cell killing. In autoimmunity, disease severity has been linked to alterations in the presence, location, and composition of Fc glycans. Significantly less is understood about the role of glycosylation in the setting of allergy and asthma. However, recent data demonstrate that glycosylation of IgE at the asparagine-394 site of Cε3 is necessary for IgE interaction with the high affinity IgE receptor but, surprisingly, glycosylation has no effect on IgE interaction with its low-affinity lectin receptor, CD23. Variations in the specific glycoform may modulate the interaction of an Ig with its receptors. Significantly more is known about the functional effects of glycosylation of IgG than for other Ig isotypes. Thus, the role of glycosylation is much better understood in the areas of autoimmunity and cancer therapy, where IgG is the dominant isotype, than in the field of allergy, where IgE predominates. Further work is needed to fully understand the role of glycan variation in IgE and other Ig isotypes with regard to the inhibition or mediation of allergic disease.

Quantitative in vitro and in vivo models to assess human IgE B cell receptor crosslinking by IgE and EMPD IgE targeting antibodies

Targeting plasma IgE by therapeutic mABs like Omalizumab (Xolair^®) is current clinical practice for severe allergic conditions or other IgE related diseases like chronic urticaria. As an alternative to soluble IgE targeting, IgE supply can be lowered by targeting the Extracellular Membrane Proximal Domain (EMPD) of the IgE B cell receptor (BCR) present on IgE switched B cells. This ultimately leads to apoptosis of these cells upon IgE BCR crosslinking. Since tools to selectively assess the efficacy of IgE BCR crosslinking by IgE targeting antibodies are limited, a readily quantifiable cell model was developed that allows to specifically address IgE BCR crosslinking activity in vitro. The new cell model allowed for a direct quantitative comparison of anti-EMPD IgE therapeutic prototype antibody 47H4 with anti-IgE(Ce3) directed therapeutic antibody Omalizumab and with a newly selected anti-human EMPD IgE monoclonal antibody, designated mAB 15cl12. Furthermore, a complementing mouse model was developed that allows for in vivo validation of antibodies addressing human EMPD IgE. It carries a targetable humanized EMPD IgE sequence that has been introduced by seamless genomic replacement of the endogenous EMPD encoding sequence. The model allowed to directly compare IgE lowering activity of two anti-human EMPD IgE therapeutic antibodies in vivo. Our tools provide the means for quantitative assessment of IgE BCR crosslinking activity which is increasingly gaining attention with respect to forthcoming second generation anti-IgE clinical candidates such as Ligelizumab or other clinical candidates featuring additional effector functions such as IgE BCR crosslinking activity.

Allosteric mechanism of action of the therapeutic anti-IgE antibody omalizumab

Immunoglobulin E and its interactions with receptors FcϵRI and CD23 play a central role in allergic disease. Omalizumab, a clinically approved therapeutic antibody, inhibits the interaction between IgE and FcϵRI, preventing mast cell and basophil activation, and blocks IgE binding to CD23 on B cells and antigen-presenting cells. We solved the crystal structure of the complex between an omalizumab-derived Fab and IgE-Fc, with one Fab bound to each Cϵ3 domain. Free IgE-Fc adopts an acutely bent structure, but in the complex it is only partially bent, with large-scale conformational changes in the Cϵ3 domains that inhibit the interaction with FcϵRI. CD23 binding is inhibited sterically due to overlapping binding sites on each Cϵ3 domain. Studies of omalizumab Fab binding in solution demonstrate the allosteric basis for FcϵRI inhibition and, together with the structure, reveal how omalizumab may accelerate dissociation of receptor-bound IgE from FcϵRI, exploiting the intrinsic flexibility and allosteric potential of IgE.

Oral immunotherapy for food allergy

Food allergy is a pathological, potentially deadly cascade of immune responses to molecules or molecular fragments that are normally innocuous when encountered in foods, such as milk, egg, or peanut. As the incidence and prevalence of food allergy rise, the standard of care is poised to advance beyond food allergen avoidance coupled with injectable epinephrine treatment of allergen-induced systemic reactions. Recent studies provide evidence that oral immunotherapy may effectively redirect the atopic immune responses of food allergy patients as they ingest small but gradually increasing allergen doses over many months, eliciting safer immune responses to these antigens. Research into the molecular and cellular bases of pathological and therapeutic immune responses, and into the possibilities for their safe and effective modulation, is generating tremendous interest in basic and clinical immunology. We synthesize developments, innovations, and key challenges in our understanding of the immune mechanisms associated with atopy and oral immunotherapy for food allergy.

Structural basis of omalizumab therapy and omalizumab-mediated IgE exchange

Omalizumab is a widely used therapeutic anti-IgE antibody. Here we report the crystal structure of the omalizumab-Fab in complex with an IgE-Fc fragment. This structure reveals the mechanism of omalizumab-mediated inhibition of IgE interactions with both high- and low-affinity IgE receptors, and explains why omalizumab selectively binds free IgE. The structure of the complex also provides mechanistic insight into a class of disruptive IgE inhibitors that accelerate the dissociation of the high-affinity IgE receptor from IgE. We use this structural data to generate a mutant IgE-Fc fragment that is resistant to omalizumab binding. Treatment with this omalizumab-resistant IgE-Fc fragment, in combination with omalizumab, promotes the exchange of cell-bound full-length IgE with omalizumab-resistant IgE-Fc fragments on human basophils. This combination treatment also blocks basophil activation more efficiently than either agent alone, providing a novel approach to probe regulatory mechanisms underlying IgE hypersensitivity with implications for therapeutic interventions.

Critical and direct involvement of the CD23 stalk region in IgE binding

BACKGROUND

The low-affinity receptor for IgE, FcεRII (CD23), contributes to allergic inflammation through allergen presentation to T cells, regulation of IgE responses, and enhancement of transepithelial allergen migration.

OBJECTIVE

We sought to investigate the interaction between CD23, chimeric monoclonal human IgE, and the corresponding birch pollen allergen Bet v 1 at a molecular level.

METHODS

We expressed 4 CD23 variants. One variant comprised the full extracellular portion of CD23, including the stalk and head domain; 1 variant was identical with the first, except for an amino acid exchange in the stalk region abolishing the N-linked glycosylation site; and 2 variants represented the head domain, 1 complete and 1 truncated. The 4 CD23 variants were purified as monomeric and structurally folded proteins, as demonstrated by gel filtration and circular dichroism. By using a human IgE mAb, the corresponding allergen Bet v 1, and a panel of antibodies specific for peptides spanning the CD23 surface, both binding and inhibition assays and negative stain electron microscopy were performed.

RESULTS

A hitherto unknown IgE-binding site was mapped on the stalk region of CD23, and the non-N-glycosylated monomeric version of CD23 was superior in IgE binding compared with glycosylated CD23. Furthermore, we demonstrated that a therapeutic anti-IgE antibody, omalizumab, which inhibits IgE binding to FcεRI, also inhibited IgE binding to CD23.

CONCLUSION

Our results provide a new model for the CD23-IgE interaction. We show that the stalk region of CD23 is crucially involved in IgE binding and that the interaction can be blocked by the therapeutic anti-IgE antibody omalizumab.

Omalizumab for the treatment of chronic spontaneous urticaria: A meta-analysis of randomized clinical trials

BACKGROUND

Chronic spontaneous urticaria (CSU) is defined by itchy hives, angioedema, or both for at least 6 weeks. Omalizumab, an anti-IgE antibody that affects mast cell and basophil function, is a promising new treatment option. As of now, however, the efficacy and safety of different doses of omalizumab used in clinical trials for CSU have not been systematically analyzed and summarized.

OBJECTIVE

We sought to assess the efficacy and safety of different doses of omalizumab for the treatment of CSU in a meta-analysis of clinical trial results.

METHODS

Suitable trials were identified by searching PubMed, Medline, Embase, and Web of Science databases and with the help of omalizumab's manufacturers. Only double-blind, randomized, placebo-controlled studies with omalizumab-treated versus placebo-treated patients with CSU were included in this analysis.

RESULTS

We identified 7 randomized, placebo-controlled studies with 1312 patients with CSU. Patients treated with omalizumab (75-600 mg every 4 weeks) had significantly reduced weekly itch and weekly wheal scores compared with the placebo group. Omalizumab's effects were dose dependent, with the strongest reduction in weekly itch and weekly wheal scores observed with 300 mg. Rates of complete response were significantly higher in the omalizumab group (relative risk, 4.55; P < .00001) and dose dependent, with the highest rates in the 300-mg group. Rates of patients with adverse events were similar in the omalizumab and placebo groups.

CONCLUSION

This meta-analysis provides high-quality evidence for the efficacy and safety of omalizumab in patients with CSU and for treating these patients with 300 mg of omalizumab every 4 weeks.