Human FcERI-IgG and humanized anti-IgE monoclonal antibody MaE11 block passive sensitization of human and rhesus monkey lung

Combined IgE neutralization and Bifidobacterium longum supplementation reduces the allergic response in models of food allergy

IgE is central to the development of allergic diseases, and its neutralization alleviates allergic symptoms. However, most of these antibodies are based on IgG1, which is associated with an increased risk of fragment crystallizable-mediated side effects. Moreover, omalizumab, an anti-IgE antibody approved for therapeutic use, has limited benefits for patients with high IgE levels. Here, we assess a fusion protein with extracellular domain of high affinity IgE receptor, FcεRIα, linked to a IgD/IgG4 hybrid Fc domain we term IgE_TRAP, to reduce the risk of IgG1 Fc-mediated side effects. IgE_TRAP shows enhanced IgE binding affinity compared to omalizumab. We also see an enhanced therapeutic effect of IgE_TRAP in food allergy models when combined with Bifidobacterium longum, which results in mast cell number and free IgE levels. The combination of IgE_TRAP and B. longum may therefore represent a potent treatment for allergic patients with high IgE levels.

IgE is a critical component of the allergic response and therapeutic targeting can alleviate symptomology. Here the authors propose the combined use of Bifidobacterium longum and a FcεRIα extracellular domain linked to a IgD/IgG4 hybrid Fc domain fusion protein called IgE_TRAP and show reduction of mast cell and IgE levels in models of food allergy.

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.

Anti-IgE treatment in allergic rhinitis

OBJECTIVES

To review the efficacy of anti-IgE therapy in allergic rhinitis (AR).

METHODS

Literature search was performed using the PubMed and Proquest Central databases at Kırıkkale University Library.

RESULTS

Although the skin prick testing in patients suffering from AR is positive (indicating that antigen-specific Immunoglobulin E has been produced), there is no association with overall circulating IgE levels. Correlation was lacking between circulating IgE level and either skin prick tests or laboratory testing for specific IgE. Omalizumab binds to uncomplexed IgE in man more avidly than does Fc-epsilon. The effect of omalizumab is to lower the level of IgE and downgrade production of FceRI receptors (which bind IgE) in mast cells and basophils, causing less mast cell recruitment and responsivity and thus diminishing eosinophilic infiltration and activation. Anti-IgE therapy through omalizumab may shorten the lifetime of mast cells and causes dendritic cells to downgrade their production of FcεRI. There are reports indicating benefit from omalizumab in managing food allergies, nasal polyp formation, essential anaphylaxis, AR, venom allergy and eczema. Omalizumab acts to lessen circulating IgE levels, whilst reducing production of FceRI by mast cells and basophils. The fact that omalizumab influences how eosinophils respond may be down to disruption of the antigen-IgE-mast cell interactions, with mast cells being recruited at lower levels and thus chemotactic eosinophilic recruitment via cytokines being greatly reduced. Omalizumab has the effect in cases of perennial AR of blocking the increased eosinophilic recruitment and tissue infiltration initiated by seasonal antigens. Likewise, in omalizumab-treated cases, circulating unbound IgE levels showed significant decreases. For patients with perennial AR, the average daily nasal severity score was significantly reduced where omalizumab was administered, compared to placebo.

CONCLUSION

Omalizumab has efficacy in ameliorating symptoms and reduces the necessity for additional medication in both seasonal and perennial allergic rhinitis.

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.

Translational strategies for development of monoclonal antibodies from discovery to the clinic

Successful strategies for the development of monoclonal antibodies require integration of knowledge with respect to target antigen properties, antibody design criteria such as affinity, isotype selection, Fc domain engineering, PK/PD properties and antibody cross-reactivity across species from the early stages of antibody development. Biophysical measurements are one of the critical components necessary for the design of effective translational strategies for lead selection and evaluation of relevant animal species for preclinical safety and efficacy studies. Incorporation of effective translational strategies from the early stages of the antibody development process is a necessity; when considered it not only reduces development time and cost, but also fosters implementation of rational decision-making throughout all phases of antibody development.

The role of anti-IgE therapy in combination with allergen specific immunotherapy for seasonal allergic rhinitis

Novel therapies that interfere specifically with immunologic mechanisms underlying allergen-induced pathology are currently in clinical evaluation. Among these is anti-IgE, which directly targets IgE serum antibodies, thus inhibiting the central mechanism of immediate-type hypersensitivity reactions. Application of anti-IgE antibodies effectively reduces IgE serum levels regardless of allergen specificity. Anti-IgE therapy has been successfully tested in patients with allergic rhinitis, asthma, and food allergy, showing significant efficacy in reducing symptom scores and the use of rescue medications. However, such therapy is limited by high costs and the requirements for permanent or every-season treatment. The advantage of specific immunotherapy (SIT) is the potential to alter the course of the disease, which has been demonstrated in patients with allergic rhinitis, insect venom allergy and, to a lesser degree, asthma. The broader application of SIT is restricted by sometimes life-threatening adverse effects. The combination of anti-IgE with SIT was suggested to be superior to each single treatment protocol in children and adolescents with allergic rhinitis. In a randomized, double-blind trial to assess the efficacy and safety of anti-IgE (omalizumab) or placebo in combination with SIT (birch pollen or grass pollen), the combination therapy reduced symptom load, the sum of daily symptom severity score plus rescue medication use, over the birch and grass pollen seasons by nearly 50% over SIT alone. These data show that the combination of anti-IgE plus SIT may be beneficial for the treatment of allergic diseases, offering improved efficacy, limited adverse effects, and potential immune-modifying effects.

Is there a role for anti-IgE in combination with specific allergen immunotherapy?

PURPOSE OF REVIEW

A line of novel therapeutic approaches that try to interfere more specifically with the immunological mechanisms underlying allergen-induced pathology are currently undergoing clinical evaluation. The most advanced of these is anti-IgE, which directly targets IgE serum antibodies, thus inhibiting the central mechanism of immediate type hypersensitivity reactions. In addition, a lot of interest has recently been focused on allergen-specific immunotherapy due to its potential to cure allergic diseases. In the present review, state-of-the-art treatment of allergic diseases with anti-IgE and allergen-specific immunotherapy is summarized, and the potential of combination therapy with both treatment options is discussed.

RECENT FINDINGS

Application of anti-IgE antibodies effectively reduces IgE serum levels regardless of allergen specificity. This treatment has been successfully tested in patients with allergic rhinitis, asthma and food allergy, showing significant efficacy in reducing symptom scores and rescue medication use. Anti-IgE therapy is limited by high costs and the necessity for permanent or every-season treatment. The strongest argument in favor of allergen-specific immunotherapy is the potential to cure allergic diseases, which has been demonstrated in patients with allergic rhinitis, insect venom allergy and, to a lesser degree, asthma. The broader application of allergen-specific immunotherapy is restricted by sometimes life-threatening side effects. A combination of anti-IgE and allergen-specific immunotherapy was shown to be superior to each single treatment protocol in children and adolescents with allergic rhinitis, as demonstrated by efficacy of symptom scores and rescue medication use.

SUMMARY

There are strong arguments for a combination of anti-IgE plus allergen-specific immunotherapy for treatment of allergic diseases: improved efficacy, limited side effects, and potential curative effects.

Molecular aspects of allergy

Atopic diseases such as asthma, rhinitis, eczema and food allergies have increased in most industrialised countries of the world during the last 20 years. The reasons for this increase are not known and different hypotheses have been assessed including increased exposure to sensitising allergens or decreased stimulation of the immune system during critical periods of development. In allergic diseases there is a polarisation of the Th2 response and an increase in the production of type 2 cytokines which are involved in the production of immunoglobulin E and the development of mast cells, basophils and eosinophils leading to inflammation and disease. The effector phase of atopy is initiated by interaction with Fc epsilon RI expressed on effector cells such as mast cells and basophils but also found on an ever increasing list of cells. Binding of a polyvalent allergen to the variable part of IgE leads to a cross-link of the receptor that triggers the cell to release histamine and pharmacological mediators of the symptomatic allergic response. Cross-linking of Fc epsilon RI by autoantibodies against the alpha-chain of the Fc epsilon RI, causing subsequent histamine release is thought to be involved in the pathogenesis of other diseases such as chronic idiopathic urticaria (CIU). To date, most therapeutic strategies are aimed at inhibiting and controlling components of the inflammatory response. Recently, new treatment strategies have emerged that focus on the development of preventive and even curative treatments. The most promising therapeutic approaches are aimed at inhibiting the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic anti-IgE or anti-Fc epsilon RIalpha autoantibodies. Clinical trials in humans using an humanised anti-IgE antibody showed that this antibody was well tolerated and reduced both symptoms and use of medication in asthma and allergic rhinitis. Thus interruption of the atopic cascade at the level of the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic antibodies is effective and represents an attractive therapy for the treatment of atopic disease.

A minimal receptor-Ig chimera of human FcepsilonRI alpha-chain efficiently binds secretory and membrane IgE

We constructed a soluble minimal receptor-Ig chimera in which the two extracellular domains of human Fcepsilonhain (D1 and D2) were fused to the dimerizing C-terminal domain of human IgG1 heavy chain (gamma1-CH3). The protein was expressed and actively secreted by Chinese hamster ovary (CHO) cells as a fully glycosylated soluble dimeric protein. It showed efficient binding both to human membrane-bound IgE isoforms and to the two secretory IgE isoforms. Moreover, the dimeric receptor binds IgE with the expected 1:2 stoichiometry. The receptor-Ig chimera, in 2-fold molar excess, inhibited engagement of secretory IgE to rat basophilic leukemia cells expressing the human alphabetagamma receptor. Full self-nature and inability to bind Fcgamma receptors make this protein an attractive candidate for clinical applications and a novel biotechnological tool for atopic allergy research.

Conditional autoantibodies in urticaria patients: a unifying hypothesis

Chronic urticaria may be characterized by conditional autoantibodies against the alpha-chain of the high-affinity receptor for IgE (FcepsilonRI). These autoantibodies are termed conditional as they only recognize unoccupied FcepsilonRI. The same conditional reactivity pattern has also been found in sera of atopic and normal healthy donors. Any condition resulting in accessibility of FcepsilonRI will render these autoantibodies anaphylactogenic. This finding offers a unifying hypothesis for the manifestation of different forms of urticaria. Non-immunologic triggers may thereby influence directly or indirectly the number of accessible FcepsilonRI allowing the conditional autoantibodies to induce urticaria symptoms.

Conditional autoimmunity mediated by human natural anti-Fc(epsilon)RIalpha autoantibodies?

Natural antibodies provide an early defense mechanism against pathogens, show a frequent self-reactivity, and are present throughout life. Two questions concern the physiological control of self-reactivity and the pathogenetic link to autoimmune disease. Here we propose a concept of conditional autoimmunity involving natural antibodies against the alpha chain of the high-affinity receptor for IgE (Fc(epsilon)RIalpha ). Like other natural antibodies, anti-Fc(epsilon)RIalpha antibodies are found in sera of healthy donors. We now report the first human recombinant anti-Fc(epsilon)RIalpha autoantibodies isolated by repertoire cloning from a human tonsillar IgM library. These high-affinity antibodies recognize Fc(epsilon)RIalpha on cells and trigger histamine release from freshly isolated blood basophils. However, the latter effect requires IgE removal from the Fc(epsilon)RI. The same conditional histamine release is seen when using sera from individual normal donors and affinity-purified anti-Fc(epsilon)RIalpha antibodies isolated from multidonor therapeutic IgG preparations. We propose that such anti-Fc(epsilon)RIalpha antibodies can become pathogenic and that this is dependent on the state of occupancy of the Fc(epsilon)RIalpha by its natural ligand IgE. We suggest that an imbalance between Fc(epsilon)RIalpha occupancy and natural anti-Fc(epsilon)RIalpha antibodies may be implicated in the pathogenesis of autoimmune urticaria.

Treatment of allergic asthma with monoclonal anti-IgE antibody. rhuMAb-E25 Study Group

BACKGROUND

Immune responses mediated by IgE are important in the pathogenesis of allergic asthma. A recombinant humanized monoclonal antibody (rhuMAb-E25) forms complexes with free IgE and blocks its interaction with mast cells and basophils. We studied the efficacy of rhuMab-E25 as a treatment for moderate-to-severe allergic asthma.

METHODS

After a 4-week run-in period, we randomly assigned 317 subjects (age range, 11 to 50 years) who required inhaled or oral corticosteroids (or both) to receive either placebo or one of two regimens of rhuMAB-E25: high-dose rhuMAb-E25 (5.8 microg per kilogram of body weight per nanogram of IgE per milliliter or low-dose rhuMAb-E25 (2.5 microg per kilogram per nanogram of IgE per milliliter) intravenously on days 0 (half a dose), 4 (half a dose), and 7 (full dose) and then once every 2 weeks thereafter for 20 weeks. For the first 12 weeks of the study, the subjects continued the regimen of corticosteroids they had received before enrollment. During the following eight weeks, the doses of corticosteroids were tapered in an effort to discontinue this therapy. The primary outcome measure was an improvement in the asthma symptom score at 12 weeks, according to a 7-point scale, in which a score of 1 indicated no symptoms and a score of 7 the most severe symptoms.

RESULTS

A total of 106 subjects were assigned to receive a high dose of rhuMAb-E25, 106 were assigned to receive a low dose, and 105 were assigned to receive placebo. At base line, the mean asthma symptom score was 4.0. After 12 weeks of therapy, the mean (+/-SE) scores were 2.8+/-0.1 in the high-dose group (P=0.008) and 2.8+/-0.1 in the low-dose group (P=0.005), as compared with 3.8+/-0.1 in the placebo group. At 20 weeks, the mean scores were 2.7+/-0.1 in both the high-dose group (P=0.048) and the low-dose group (P=0.14), as compared with 2.9+/-0.1 in the placebo group. More subjects in the two rhuMAb-E25 groups were able to decrease or discontinue their use of corticosteroids than in the placebo group, but only some of the differences were significant. After 20 weeks, serum free IgE concentrations decreased by a mean of more than 95 percent in both rhuMAb-E25 groups. The therapy was well tolerated. After 20 weeks, none of the subjects had antibodies against rhuMAb-E25.

CONCLUSIONS

A recombinant humanized monoclonal antibody directed against IgE has potential as a treatment for subjects with moderate or severe allergic asthma.

Production of a Chimeric Form of CD23 That Is Oligomeric and Blocks IgE Binding to the FcεRI

The low affinity receptor for IgE (FcεRII/CD23) has previously been shown to interact with IgE with a dual affinity. Three chimeric constructs were created containing the lectin domain (amino acids 172–188) or the “neck” and lectin domain (amino acids 157–188) attached to subunits of oligomeric proteins. All chimeras were incapable of interacting with IgE with either a high or low affinity, indicating that the α-helical stalk of CD23 is important for orienting the lectin heads such that an interaction with IgE can occur. This concept received further support in that a chimeric CD23 composed of the human CD23 stalk and the mouse CD23 lectin head bound mouse IgE with a dual affinity, but could only bind rat IgE with a low affinity. Effort was next concentrated on a construct consisting of the entire extracellular (EC) region of CD23. A mutation to the first cleavage site of CD23 (C1M) resulted in a more stable molecule as determined by a decrease of soluble CD23 release. A soluble chimeric EC-C1M was prepared by attaching an isoleucine zipper to the amino terminus (lzEC-C1M). The interaction with IgE by lzEC-C1M was found to be superior to that seen with EC-CD23. The lzEC-C1M could inhibit binding of IgE to both CD23 and the high affinity receptor for IgE, FcεRI, providing further evidence for a strong interaction with IgE. FcεRI inhibition (∼70%) was seen at equimolar concentrations of lzEC-C1M, implying the effectiveness of this chimera and suggesting its potential therapeutic value.

Mechanisms of immune sensitization of human bronchus

Bronchial hyperresponsiveness (BHR), the increased sensitivity to a wide variety of stimuli that narrow the airways, is a central abnormality in patients with asthma, and is frequently observed in patients with chronic obstructive pulmonary disease. In the study of the underlying mechanisms of BHR, various animal models have been employed, using methods of active and passive immunization. These studies have led to a changed understanding of smooth muscle hyperreactivity, questioning both the past paradigm of altered neural activity and the modern concepts of inflammation as the single most factor determining BHR, and emphasizing the particular importance of the end organ- the smooth muscle cell. More recently, passive sensitization of human airways has been used by several investigators to describe the mechanisms of allergic sensitization and to study the role of functional abnormalities of human airway smooth muscle, which may represent the key to understanding human BHR, and thus lead to novel treatment approaches for the future.

Increased expression of high affinity IgE (FcepsilonRI) receptor-alpha chain mRNA and protein-bearing eosinophils in human allergen-induced atopic asthma

FcepsilonRI receptors play an important role in allergen-induced mediator release and antigen presentation by mast cells, basophils, and monocyte/macrophages in atopic disorders. The expression of FcepsilonRI by tissue eosinophils in atopic asthma after allergen challenge has not been established. For this reason we attempted to identify mRNA and protein product + FcepsilonRIalpha eosinophils in cytospins made from bronchoalveolar lavage (BAL) from atopic asthmatics (n = 9) and nonatopic normal subjects (n = 4) 24 h after segmental challenge with allergen or diluent. Messenger RNA for FcepsilonRIalpha was determined using in situ hybridization and FcepsilonRIalpha protein expression by immunocytochemistry using a mouse monoclonal antibody 22E7. Colocalization of FcepsilonRIalpha receptors to eosinophils was performed using chromotrope 2R. When compared with a control challenge, segmental challenge with Dermatophagoides pteronyssinus induced significant BAL eosinophilia (p = 0.007). The total number of BAL FcepsilonRIalpha mRNA and protein-positive cells also increased in asthmatics, median values 2 (0.7-7.2) and 11.5 (0.6-65.0) x 10(6) cells (p = 0.02) and 0 (0-0.3 x 10(6)) and 3.1 x 10(6) (0.45 - 162.5 x 10(6)) cells (p = 0.007), respectively, for mRNA and protein. Net increases in FcepsilonRIalpha+ cells correlated with the net increases in BAL eosinophils (r = 0.98, p = 0.0001 for mRNA and r = 0.72, p = 0.02 for protein). Colocalization studies with chromotrope 2R revealed that only 4% of FcepsilonRIalpha+ cells were eosinophils after control challenge and, in contrast, 85 to 95% of FcepsilonRIalpha+ cells were eosinophils after allergen. There were no differences in the numbers of FcepsilonRIalpha+ cells or eosinophils in normal control subjects. Our results demonstrated that local endobronchial allergen provocation in atopic asthmatics results in increased synthesis and expression of FcepsilonRIalpha predominantly on BAL eosinophils.

Anti-immunoglobulin E antibody treatment blocks histamine release and tissue contraction in sensitized mice

Inhibition of antigen-specific IgE response has been shown to lead to amelioration of allergic disease symptoms. In an effort to design a therapy aimed at decreasing IgE levels, we reported previously that treatment of mice with an anti-IgE antibody coincident with the primary antigen immunization resulted in significant decreases in antigen-specific IgE synthesis, without substantially altering IgG levels. In the present study, we employed this mouse model and a surrogate antibody to investigate the capacity of anti-IgE treatment to block an established IgE response in vivo. Results of these experiments suggest that anti-IgE treatment concomitant with an antigen boost results in removal of detectable circulating IgE for at least 7 weeks (the duration of the study). Moreover, tissues removed from mice following anti-IgE treatment failed to release histamine and contract in response to antigen challenge ex vivo. These findings demonstrate that reduction of circulating IgE correlates to an inhibition of tissue mast cell sensitization and mediator release in response to antigen challenge and further supports the concept of anti-IgE treatment as a promising therapy for the treatment of allergic disease.

Inhibition of human airway sensitization by a novel monoclonal anti-IgE antibody, 17-9

We investigated the effect of a novel mouse IgG2b nonanaphylactogenic anti-human IgE antibody, 17-9, on allergen and histamine responses in passively sensitized human airways in vitro to determine the specific contribution of IgE to the sensitization process. Bronchial rings were sensitized with serum containing high levels of allergen-specific IgE (Dermatophagoides farinae), or with a hapten-specific chimeric humanized IgE (JW8). There was a concentration-dependent contraction of serum-sensitized bronchial rings to D. farinae (517 +/- 188 mg tension at 10 U/ml, n = 8) that was not observed in nonsensitized controls. This response was practically abolished when tissues were sensitized in the presence of 100 microg/ml anti-IgE antibody 17-9 (54 +/- 20 mg). In tissues sensitized with the anti-NIP IgE, JW8, there was a concentration-dependent contraction to the specific antigen NIP-BSA (560 +/- 154 mg at 0.3 microg/ml, n = 5) that was not observed in nonsensitized control subjects and that was substantially inhibited when 17-9 was present in the sensitization buffer (124 +/- 109 mg). The inhibition with 17-9 was specific, as pretreatment with a non-IgE-specific IgG2b antibody did not affect allergen responses. Potency and maximal contractions to histamine in serum-sensitized tissues were significantly elevated compared with nonsensitized controls; this was not affected by the presence of 17-9 during sensitization (pEC50 = 5.1 +/- 0.2 versus 5.0 +/- 0.3 in tissues sensitized in the absence of 17-9). In tissues sensitized with JW8 there was no significant increase in responsiveness to histamine. We conclude that allergen responses in sensitized human airways are dependent on IgE levels in the sensitizing serum while nonspecific (hyper)responsiveness depends on serum factors other than IgE. Nonanaphylactogenic anti-human IgE antibodies effectively inhibit allergen responses of human airways in vitro but may not affect other factors inducing hyperresponsiveness.

Inhibition of an established allergic response to ovalbumin in BALB/c mice by killed Mycobacterium vaccae

Allergic disorders are mediated by T lymphocytes secreting T helper 2 (Th2) cytokines, interleukin-4 (IL-4) and interleukin-5 (IL-5), resulting in high levels of serum immunoglobulin E (IgE) and recruitment of eosinophils. One of the treatment strategies is to downregulate the Th2 component by inducing a T helper 1 (Th1) response to the relevant allergen, because Th1 and Th2 cytokines are thought to be mutually antagonistic. In this study, we examined the effects of Mycobacterium vaccae, a potent inducer of Th1 immunity, on allergic responses in a murine model. A single injection of M. vaccae into ovalbumin (OVA)-preimmunized BALB/c mice suppressed serum IgE over a wide dose range (10(7), 10(8) or 10(9) M. vaccae). Further experiments, using 10(7) M. vaccae injected twice, showed that this treatment inhibited not only serum IgE, but also the potential for ovalbumin-induced IL-5 production by spleen cells. This non-specific ability of a mycobacterium to decrease Th2 activity, even when not presented together with the allergen, is in agreement with recent epidemiological studies on the impact of bacillus Calmette-Guérin (BCG) vaccination, and of other potent Th1 stimuli, on the incidence of atopy. The suppression of serum IgE and allergen-specific IL-5 synthesis by M. vaccae suggest that this organism is likely to have clinical application in the immunotherapy of allergy.

Anti-FcepsilonRIalpha autoantibodies in autoimmune-mediated disorders. Identification of a structure-function relationship

Anti-FcepsilonRIalpha autoantibodies (autoAbs) occur and may be of pathogenetic relevance in a subset of chronic urticaria (CU) patients. To analyze the prevalence and magnitude of the humoral anti-FcepsilonRIalpha response in cohorts of CU patients compared with individuals suffering from classic skin- related (auto)immune diseases, we developed an ELISA system for the measurement of anti-FcepsilonRIalpha autoAbs in nonfractionated serum samples. Results obtained using this assay correlated well with those generated by Western blotting. We found IgG anti-FcepsilonRIalpha autoreactivity in 38% of CU patients but not in atopic dermatitis patients, psoriatics, or healthy individuals. We frequently detected anti-FcepsilonRIalpha autoAbs in pemphigus vulgaris (PV, 39%), dermatomyositis (DM, 36%), systemic lupus erythematosus (SLE, 20%), and bullous pemphigoid (BP, 13%). While the autoAb titers in DM, SLE, BP, and PV were similar to those encountered in CU patients, only anti-FcepsilonRIalpha+ CU serum specimens displayed pronounced histamine-releasing activity. The anti-FcepsilonRIalpha autoAbs in CU patients belong predominantly to the complement-fixing subtypes IgG1 and IgG3, whereas in DM, PV, and BP, they were found to be mainly of the IgG2 or IgG4 subtype. Complement-activating properties of anti-FcepsilonRIalpha autoAbs can indeed be of pathogenetic relevance, because C5a receptor blockade on basophils as well as decomplementation reduced drastically the histamine-releasing capacity of most anti-FcepsilonRIalpha-reactive CU sera. As a consequence, therapeutic efforts in CU should aim at altering not only the quantity but also the complement-activating properties of IgG anti-FcepsilonRIalpha autoAbs.

Allergen-induced bronchial hyperreactivity and eosinophilic inflammation occur in the absence of IgE in a mouse model of asthma

In patients with asthma, elevations of IgE correlate both with allergic inflammation of the airways and with bronchial hyperreactivity (BHR). Several investigations, using mouse models of this disease, have indicated a central role for IgE in the pathogenesis of the eosinophilic inflammation as well as in the obstructive airway physiology of BHR. Some diagnostic studies and therapeutic strategies for asthma are based on the putative role of IgE in asthma pathogenesis. Here, we use mice with a null mutation of the C epsilon locus to show that bronchial inflammation and BHR in response to allergen inhalation both can occur in the absence of IgE. We demonstrate that the eosinophilic bronchial inflammation elicited in an established mouse model of hypersensitivity to Aspergillus fumigatus (Af) is accompanied by the asthmatic physiology of BHR. Wild-type and IgE-deficient mice were sensitized intranasally with Af extract. Both groups of animals developed bronchoalveolar lavage eosinophilia and pulmonary parenchymal eosinophilia. This was accompanied by increased serum levels of total and Af-specific IgE in the wild-type animals only. This Af-sensitization protocol resulted in significant BHR in both wild-type mice and IgE-deficient mice. Interestingly, unsensitized IgE-deficient mice had increased bronchial responsiveness compared with unsensitized wild-type controls. We conclude that BHR and airways inflammation can be fully expressed via IgE-independent mechanisms. These may involve the activation of mast cells by factors other than IgE as well as a mucosal lymphocyte-mediated immune response to allergen.

Anti-IgE and anti-Fc epsilon RI autoantibodies in clinical allergy

Autoantibodies recognizing critical effector molecules of type I allergic reactions have been identified. Anti-IgE autoantibodies occur at high frequencies not only in atopic diseases but also in healthy individuals and, depending on their epitope specificities, may promote or prevent the elicitation of allergic symptoms. In contrast, anti-Fc epsilon RI autoantibodies with basophil/mast cell activating properties were selectively found in patients with chronic urticaria, a condition characterized by the continuous degranulation of mast cells. Thus, humoral anti-Fc epsilon RI autoreactivity defines a distinctive subset of chronic urticaria and may well be the causative and pathogenetic principle in this disease.

Binding of cynomolgus monkey IgE to a humanized anti-human IgE antibody and human high affinity IgE receptor

Antibodies which block IgE binding to its high affinity receptor have the therapeutic potential for treating allergic diseases. A humanized anti-human IgE antibody (E25) was developed for this purpose. Cynomolgus monkeys were used for preclinical studies of E25. We studied the binding of purified human IgE and cynomolgus monkey IgE to E25 and the human high affinity IgE receptor alpha-chain-IgG fusion molecule (Fc epsilon RI-IgG) by surface plasmon resonance. Human IgE and cynomolgus monkey IgE bound to immobilized E25 with similar affinity (apparent Kd = 0.06 and 0.19 nM, respectively). Human IgE and cynomolgus monkey IgE also bound to immobilized Fc epsilon RI-IgG with similar affinity (apparent Kd = 0.28 and 0.30 nM, respectively). These data suggest that the cynomolgus monkey is a valid model for preclinical studies of the E25 antibody and probably for other antibodies which block IgE binding to its receptor. An enzyme-linked immunosorbent assay (ELISA) for measuring cynomolgus monkey IgE was developed to support preclinical studies. This ELISA used FcERI-IgG for capture and peroxidase labelled goat polyclonal antibody to human IgE for detection. Using purified cynomolgus monkey IgE as the standard, the serum IgE levels in six cynomolgus monkeys measured were 4-23 micrograms/ml.

Anti-IgE in allergic sensitization

Anti-IgE autoantibodies exist predominantly in the sera of patients with atopic disease. For some time such anti-IgE autoantibodies have been considered a phenomenon that may not be of clinical importance. The cloning of such anti-IgE autoantibodies has eliminated doubts of whether these antibodies exist, but it is still unclear whether such autoantibodies play a pathophysiological role. However, there are ongoing clinical trials that use humanized anti-IgE antibodies for passive immunization of atopic individuals. While this approach may not definitely clarify the role of anti-IgE autoantibodies, it will nevertheless clarify the role of IgE.