Response of FcεRI-bearing leucocytes to omalizumab in chronic spontaneous urticaria

COVID-19 infection in chronic spontaneous urticaria treated with omalizumab: two case reports

Not available

Biomarkers predicting the controller dose of omalizumab in patients with chronic spontaneous urticaria

BACKGROUND

Clinical trials showed the efficacy of 300 mg/4 weeks of omalizumab (OMA) during 6 months in patients with severe chronic spontaneous urticaria (CSU). Nevertheless, in real life, many patients require higher doses and/or longer treatment. This study assesses the real-life performance of OMA in severe CSU and identifies factors associated with the response.

METHODS

CSU patients eligible for OMA were recruited prospectively. Clinical data and a blood test were collected before OMA initiation. Urticaria Activity Score 7 (UAS7) was calculated at baseline and every 3 months during OMA treatment. CSU control was defined as UAS7 <7 points. This work was partially sponsored by OMA manufacturer.

RESULTS

Eighty-nine adults (19.1% males) with severe CSU were recruited. Median duration of CSU prior to OMA initiation was 2 years, and median severity by UAS7 at baseline was 24 points (range 10-42 points). OMA controlled 94.4% of patients, but 17.9% of responders required doses >300 mg/4 weeks. A blood basophil count >20 cells/μL (OR 13.33; 95% CI 3.32-52.63; p < .001) and the absence of hypothyroidism (OR 3.65; 95% CI 0.78-16.95; p = .099) were identified as predictive factors to achieve control with 300 mg/4 weeks. Twelve patients were able to stop OMA during the study (responders in remission, RR). RR had received OMA for a median of 29 months (12-53 months). Conversely, 32 patients had been on OMA for >29 months at the end of the study (active responders, AR). AR had received OMA for a median of 45 months (30-100 months). There were no significant differences in clinical or analytical factors between RR and AR patients.

CONCLUSIONS

Low blood basophil count and the presence of hypothyroidism might serve as biomarkers for the controller dose of OMA in severe CSU patients.

PTGS2: A potential immune regulator and therapeutic target for chronic spontaneous urticaria

AIMS

Chronic spontaneous urticaria (CSU) is a common and debilitating skin disease that is difficult to control with existing treatments, and the pathogenesis of CSU has not been fully revealed. The aim of this study was to explore the underlying mechanisms of CSU and identify potential treatments.

MATERIALS AND METHODS

Microarray datasets of CSU were obtained from Gene Expression Omnibus database. Differentially expressed genes between skin lesions of CSU and normal controls (LNS-DEGs) were identified, and the enrichment analyses of LNS-DEGs were performed. Hub genes of LNS-DEGs were selected by protein-protein interaction analysis. The co-expression and transcriptional regulatory networks of hub genes were conducted using GeneMANIA and TRRUST database, respectively. CIBERSORT was utilized for immune cell infiltration analysis. Experimental validation was performed by β-hexosaminidase release examination and passive cutaneous anaphylaxis (PCA) mouse model.

KEY FINDINGS

A total of 247 LNS-DEGs were identified, which were enriched in cell migration, cell chemotaxis, and inflammatory pathways such as TNF and interleukin (IL) -17 signaling pathway. Among LNS-DEGs, seven upregulated (PTGS2, CCL2, IL1B, CXCL1, IL6, VCAM1, ICAM1) and one downregulated hub gene (PECAM1) were selected. Immune infiltration analysis identified eight different immune cells, such as activated/resting mast cells and neutrophils. Furthermore, PTGS2, encoding cyclooxygenase 2 (COX2), was selected for further validation. COX2 inhibitor, celecoxib, significantly inhibited mast cell degranulation, and reduced vascular permeability and inflammatory cytokine expression in PCA mouse model.

SIGNIFICANCE

PTGS2 may be a potential regulator of immunity and inflammation in CSU. Targeting PTGS2 is a new perspective for CSU treatment.

Biomarkers for Monitoring Treatment Response of Omalizumab in Patients with Chronic Urticaria

Chronic urticaria (CU) is a debilitating skin disease affecting around 1% of the population. CU can be subdivided into chronic spontaneous urticaria (CSU) and chronic inducible urticaria (CIndU). Different pathophysiological mechanisms have been proposed to play a role in the development of CU, and these are also being investigated as potential biomarkers in the diagnosis and management of the disease. As of now the only assessment tools available for treatment response are patient reported outcomes (PROs). Although these tools are both validated and widely used, they leave a desire for more objective measurements. A biomarker is a broad subcategory of observations that can be used as an accurate, reproducible, and objective indicator of clinically relevant outcomes. This could be normal biological or pathogenic processes, or a response to an intervention or exposure, e.g., treatment response. Herein we provide an overview of biomarkers for CU, with a focus on prognostic biomarkers for treatment response to omalizumab, thereby potentially aiding physicians in personalizing treatments.

Basophil Characteristics as a Marker of the Pathogenesis of Chronic Spontaneous Urticaria in Relation to the Coagulation and Complement Systems

Chronic spontaneous urticaria (CSU) is a common skin disorder characterized by daily or almost daily recurring skin edema and flare with itch and pruritus anywhere on the body for more than 6 weeks. Although basophil- and mast cell-released inflammatory mediators, such as histamine, play important roles in the pathogenesis of CSU, the detailed underlying mechanism is not clear. Since several auto-antibodies, IgGs which recognize IgE or the high-affinity IgE receptor (FcεRI) and IgEs against other self-antigens, are detected in CSU patients, they are considered to activate both mast cells in the skin and basophils circulating in the blood. In addition, we and other groups demonstrated that the coagulation and complement system also contribute to the development of urticaria. Here, we summarized the behaviors, markers and targets of basophils in relation to the coagulation-complement system, and for the treatment of CSU.

Urticaria and basophils

Chronic spontaneous urticaria (CSU) is a common skin disease without an etiology in the vast majority of cases. The similarity of symptoms and pathology to allergen-induced skin reactions supports that skin mast cell IgE receptor activation is also involved in CSU. Accumulating evidence also supports a role for blood basophils in disease expression. Blood basopenia is noted in active CSU disease with the recruitment of blood basophils to skin lesion sites. Blood basophils further display altered IgE receptor mediated degranulation patterns in two phenotypes that improve in remission. In active CSU subjects, changes in IgE receptor signaling molecule expression levels accompany the altered degranulation function in blood basophils. The success of therapies targeting IgE in CSU patients have also shown that altered blood basophil phenotypes and enumeration have potential use as a disease biomarker.

Differences in allergen-specific basophil activation and T cell proliferation in atopic dermatitis patients with comorbid allergic rhinoconjunctivitis treated with a monoclonal anti-IL-4Rα antibody or allergen-specific immunotherapy

BACKGROUND

Atopic dermatitis (AD), a chronic inflammatory disorder, is often accompanied by allergic rhinoconjunctivitis (ARC) as a co-morbidity. The use of a monoclonal anti-IL-4Rα antibody has been effective in controlling moderate to severe AD symptoms. Allergen-specific immunotherapy (AIT) is widely used for the treatment of ARC and asthma. The effects of AIT on basophil reactivity/effector functions have already been examined and used as indicators of the treatment efficacy. However, it is unclear, how an anti-IL-4Rα antibody can influence allergen-specific immune responses of basophils and T cells of AD patients with comorbid ARC.

OBJECTIVE

To investigate the effect of a monoclonal anti-IL-4Rα antibody on the in vitro allergic responses of basophils and T cells deriving from AD patients with comorbid ARC.

METHODS

Blood samples of 32 AD patients were obtained before, after 4 and 16 weeks of an anti-IL-4Rα antibody therapy (300 mg subcutaneously/2 weeks; n = 21) or AIT (daily sublingual application; n = 11). Patients treated with an anti-IL-4Rα antibody were grouped according to their serum specific immunoglobulin E levels and ARC symptoms, while patients receiving an AIT were additionally grouped according to the allergen specificity of their AIT. Basophil activation test and T cell proliferation assays were undertaken after an in vitro allergen stimulation.

RESULTS

A significant reduction of the immunoglobulin E levels and the allergen-specific T cell proliferation was observed in AD patients treated with an anti-IL-4Rα -antibody, while the allergen-specific basophil activation/sensitivity were found to be significantly increased. In patients receiving an AIT, the in vitro allergen-specific basophil activation and the T cell proliferation were found to be significantly decreased in response to seasonal allergens.

CONCLUSIONS

An IL-4Rα blockade induced by a monoclonal anti-IL-4Rα antibody leads to an increased activity/sensitivity of early effector cells (such as basophils), in contrast to a decreasing reactivity observed under an AIT. The late-phase T cell reaction to allergens did not differ between the herein assessed treatments.

Comorbidities of Chronic Urticaria: A glimpse into a complex relationship

Chronic Urticaria (CU) is a chronic inflammatory, predominantly mast cell-driven disease, characterized by the development of wheals and/or angioedema for more than 6 weeks. It affects approximately 1%-5% of the total population worldwide and imposes a substantial burden on health-related quality of life, significantly affecting patients' daily life. The economic impact on the health system is also not negligible, with an estimated cost per patient per year of approximately 2.000 $ in the United States. Although the underlying pathophysiology is not fully explored, autoimmune mechanisms have been proposed, including type I ("autoallergy" by means of autoantibodies to self-antigens) and type IIb (autoimmunity). Atopic, autoimmune, and psychiatric disorders are prevalent comorbidities in both children and adults with Chronic Spontaneous Urticaria (CSU). Although malignancies, cardiovascular diseases and other comorbidities have also been reported as associated diseases in patients with CSU, data remain scarce. It is still unknown whether the aforementioned comorbidities share common pathophysiological mechanisms with specific endotypes of CSU. The current review aims to overview current data on comorbidities of CU, and furthermore to comment on the potential linked pathways underlying these diseases.

Ligelizumab impairs IgE ‐binding to plasmacytoid dendritic cells more potently than omalizumab and restores IFN ‐α production and FOXP3 + Treg generation

BACKGROUND

Ligelizumab is an anti-IgE monoclonal antibody binding IgE with higher affinity than omalizumab that is under clinical investigation for several IgE-mediated diseases. We previously showed that omalizumab removes IgE bound to FcεRI on plasmacytoid dendritic cells (pDCs) and restores their ability to produce IFN-α and regulatory T cells (Tregs). The aim of this work is to investigate the capacity of ligelizumab to regulate functional properties of pDCs in comparison with omalizumab.

METHODS

pDCs were isolated from atopic donors and IgE was detached from FcεRI on pDCs with designed ankyrin repeat protein (DARPin) bi53-79. pDCs were resensitized with IgE alone or in the presence of ligelizumab or omalizumab prior to IgE-FcεRI crosslinking and Toll-like receptor 9 (TLR9) stimulation. Flow cytometry, ELISA, coculture experiments and intranuclear staining were performed to determine cytokine production and Treg generation. An antigen-specific model of resensitization and IgE-crosslinking was also performed.

RESULTS

The levels of serum total free IgE show a non-linear positive correlation with the frequency of IgE⁺ pDCs displaying IgE bound to FcεRI within the 43 individual donors included in the study. Ligelizumab displays stronger capacity than omalizumab to block the binding of free IgE to FcεRI on human pDCs, resulting in a greater restoration of TLR9-L-induced IFN-α production. Ligelizumab also restores the ability of pDCs to generate FOXP3⁺ Tregs as previously reported for omalizumab.

CONCLUSIONS

The uncovered novel molecular mechanisms of ligelizumab to regulate functional properties of pDCs from atopic donors might have important clinical implications for anti-IgE treatments in different IgE-mediated diseases.

Decreased peripheral basophil counts in urticaria and mouse model of oxazolone-induced hypersensitivity, the latter suggesting basopenia reflecting migration to skin

A decrease in the number of basophils in the peripheral blood, or basopenia, has been noted, reflecting the activity of chronic spontaneous urticaria (CSU). Infiltration of basophils into the skin has also been reported, but the mechanism of basopenia in CSU has not been clarified. The phenomenon of basopenia during the active phase of urticaria was confirmed, and basophil numbers increased following symptom improvement in 15 out of 17 patients treated with omalizumab and in 13 of 15 patients treated with antihistamines. Our examination by immunostaining also revealed basophil infiltration of the CSU lesions, as in previous reports, but since most of our patients were already taking oral steroids, it was not considered appropriate to examine the relationship between basophil numbers in tissue and peripheral blood. Then, we used mouse model of contact hypersensitivity with a single application of oxazolone, which is known to stimulate basophil infiltration, and investigated basophil counts in the skin, peripheral blood, and bone marrow. In this model, a decrease in peripheral blood basophil numbers was observed one day after challenge, but not after 2 days, reflecting supplementation from the bone marrow. Indeed, when cultured basophils expressing GFP were transplanted into the peripheral blood, GFP-positive basophil numbers in the peripheral blood remained low even after 2 days of challenge. Despite differences among species and models, these results suggest that one reason for the decrease of basophils in the peripheral blood in CSU may involve migration of circulating basophils into the skin.

The Potential Role of Basophils in Urticaria

Urticaria is a symptom of acute skin allergies that is not clearly understood, but mast cell histamine is hypothesized to cause swelling and itching. Omalizumab, an anti-human IgE antibody that traps IgE and prevents its binding to high-affinity IgE receptors, is effective in treating urticaria. We recently experienced a case of urticaria refractory to antihistamine therapy in which the peripheral-blood basophil count responded to omalizumab therapy and its withdrawal. Furthermore, the peripheral-blood basophils showed an unexpected increase in the expression of a cell surface activation marker. This phenomenon has been reported by other analyses of basophil and mast cell dynamics during omalizumab treatment. Here, we analyze these observations and formulate a hypothesis for the role of basophils in urticaria. Specifically, that activated basophils migrate to the local skin area, lowering peripheral-blood counts, omalizumab therapy alters basophilic activity and causes their stay in the peripheral blood. We hope that our analysis will focus urticaria research on basophils and reveal new aspects of its pathogenesis.

Sex differences in the efficacy of omalizumab in the treatment of chronic spontaneous urticaria

Background

Omalizumab is shown to be effective in the treatment of chronic spontaneous urticaria (CSU), a disease with high personal and social impact. Sex differences in CSU are recognized with women more frequently affected. Scarce is the knowledge about response to omalizumab between sex groups. We sought to identify any differences based on the sex of patients receiving omalizumab.

Methods

We evaluated data of patients diagnosed with CSU refractory to high-dose second-generation H1 antihistamines and treated with 300 mg omalizumab every 4 weeks for 6 months and then at relapse.

Results

Discussion: All patients, regardless of sex, age, or any other factor, achieved the clinical remission of the disease after the first 3 doses with a reduction of the disease activity indices and impact on the quality of life. Recurrences predominate in men, two months after the suspension of the drug. Respect to sex and recurrence we did not find any correlation with age, body mass index, peripheral eosinophil counts, total IgE levels, D-dimer, plasma prothrombine level or C-reactive protein. We found no sex differences in tolerability and safety. CSU in girls may persist longer and have worse prognosis, but no one has so far noted sex differences in response to omalizumab.

Conclusions

Although there are no certainties on the mechanism of action of omalizumab in CSU, the noticeable difference in response between males and females lead us to suppose a role of the hormonal balance both on the pathogenesis of the CSU and on the efficacy of OmAb.

Developments in the field of allergy in 2020 through the eyes of Clinical and Experimental Allergy

While 2020 will be remembered for the global coronavirus pandemic, there were also important advances in the field of allergy. In this review article, we summarize key findings reported in Clinical and Experimental Allergy during 2020. We hope this provides readers with an accessible snapshot of the work published in our journal during this time.

Systemic and local evidence for complement involvement in chronic spontaneous urticaria

Background

The pathogenesis of chronic spontaneous urticaria (CSU), including the mechanism of action of omalizumab, remain unclear. We hypothesized complement system involvement given the often fast clinical response induced by treatment, including omalizumab. Therefore, we assessed the role of various complement factors surrounding omalizumab treatment.

Methods

Thirty CSU patients (median age 42 [range 21-70]; 73 % female) with a median once daily Urticaria Activity Score over 7 days (UAS7) score at baseline of 31.5 points were enrolled. Treatment consisted of six administrations of 300 mg omalizumab every 4 weeks succeeded by a follow-up period of 12 weeks. Four punch skin biopsies were taken per patient; at baseline from lesional skin, at baseline from nonlesional skin, and after 1 and 7 days from formerly lesional skin. Complement activity, including C1q, C3, C3bc/C3, C4, C4bc/C4, C5a, and Membrane Attack Complex in peripheral blood were analyzed and complement activation in the skin was determined by the analysis of C4d deposition. Results were related to the clinical response to omalizumab.

Results

Fifteen patients showed a UAS7 score of 6 or lower (median 0) at Week 24, 15 patients did not (median 16). Lesional skin biopsies at baseline revealed complement deposition (C4d) in blood vessels in the papillary dermis of 53% (16/30) of the patients, which suggests involvement of immune complexes in the pathogenesis of urticaria. Moreover, indication of increased complement activation in CSU was substantiated by increased C5a levels in peripheral blood compared to healthy controls (p = 0.010). The clinical effect of omalizumab could not be linked to the variation of complement components.

Conclusions

Both C4d deposition in lesional skin and elevated C5a levels in peripheral blood indicate the involvement of complement activation in the pathogenesis of CSU. No correlation was found between omalizumab and activation of complement indicative of independent processes in the immunopathogenesis of CSU.

Basophils and their effector molecules in allergic disorders

Basophils are the rarest granulocytes which represent <1% of peripheral blood leukocytes. Basophils bear several phenotypic similarities to tissue-resident mast cells and therefore had been erroneously considered as blood-circulating mast cells. However, recent researches have revealed that basophils play nonredundant roles in allergic inflammation, protective immunity against parasitic infections and regulation of innate and acquired immunity. Basophils are recruited to inflamed tissues and activated in an IgE-dependent or IgE-independent manner to release a variety of effector molecules. Such molecules, including IL-4, act on various types of cells and play versatile roles, including the induction and termination of allergic inflammation and the regulation of immune responses. Recent development of novel therapeutic agents has enabled us to gain further insights into basophil biology in human disorders. In this review, we highlight the recent advances in the field of basophil biology with a particular focus on the role of basophils in allergic inflammation. Further studies on basophils and their effector molecules will help us identify novel therapeutic targets for treating allergic disorders.

The efficacy of omalizumab treatment in chronic spontaneous urticaria is associated with basophil phenotypes

BACKGROUND

The mechanisms underlying disease pathogenesis in chronic spontaneous urticaria (CSU) and improvement with omalizumab are incompletely understood.

OBJECTIVES

This study sought to examine whether the rate of clinical remission is concordant with baseline basophil features or the rate of change of IgE-dependent functions of basophils and/or plasmacytoid dendritic cells during omalizumab therapy.

METHODS

Adults (n = 18) with refractory CSU were treated with omalizumab 300 mg monthly for 90 days. Subjects recorded daily urticaria activity scores, and clinical assessments with blood sampling occurred at baseline and on days 1, 3, 6, 10, 20, 30, 60, and 90 following omalizumab. At baseline, subjects were categorized by basophil functional phenotypes, determined by in vitro histamine release (HR) responses to anti-IgE antibody, as CSU-responder (CSU-R) or CSU-non-responder (CSU-NR), as well as basopenic (B) or nonbasopenic (NB).

RESULTS

CSU-R/NB subjects demonstrated the most rapid and complete symptom improvement. By day 6, CSU-R/NB and CSU-NR/NB had increased anti-IgE-mediated basophil HR relative to baseline, and these shifts did not correlate with symptom improvement. In contrast, CSU-NR/B basophil HR did not change during therapy. The kinetics of the decrease in surface IgE/FcεRI was similar in all 3 phenotypic groups and independent of the timing of the clinical response. Likewise, plasmacytoid dendritic cells' surface IgE/FcεRI decline and TLR9-induced IFN-α responses did not reflect clinical change.

CONCLUSIONS

Changes in basophil IgE-based HR, surface IgE, or FcεRI bear no relationship to the kinetics in the change in clinical symptoms. Baseline basophil count and basophil functional phenotype, as determined by HR, may be predictive of responsiveness to omalizumab.

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.

Hematologic parameters as biomarkers for antihistamine and omalizumab resistance in chronic spontaneous urticaria

Background: Biomarkers of resistance to H₁-antihistamines (AH) and omalizumab in chronic spontaneous urticaria (CSU) are still a matter of debate. Objective: To identify clinical and laboratory attributes of the patient that may be predictive of AH and omalizumab resistance in CSU. Methods: We conducted a retrospective observational study by using the electronic patient record data base of patients with CSU and of sex- and age-matched controls. Patients with CSU were divided into three study groups: the CSU group, patients who responded to AHs; the antihistamine-resistant CSU (AH-CSU) group, patients refractory to a fourfold AH dose; and the control group, composed of a random sample of age- and sex-matched subjects, with a case-control ratio of 1:2. The patients in the AH-CSU group treated with omalizumab were compared according to the response or resistance to omalizumab. Results: A total of 106 subjects in the AH-CSU group, 483 in the CSU group, and 1198 in the control group were compared. Both AH-CSU (112.7 ± 43.1 kU/mL) and CSU (129.5 ± 52.4 kU/mL) groups were associated with higher plasma total IgE levels than control group (103.2 ± 49.5 kU/mL; p < 0.001). The AH-CSU group was characterized by a higher plasma high-sensitivity C-reactive protein level (6.4 ± 3.7 mg/L) than the CSU group (4.3 ± 1.4 mg/L; p < 0.001) and the control group (3.1 ± 1.8 mg/L; p < 0.001). The AH-CSU and CSU groups were characterized by a lower mean ± standard deviation basophil counts (0.18 ± 0.16 cells ×10⁹/L and 0.19 ± 0.11 cells ×10⁹/L, respectively) than the control group (0.22 ± 0.09 cells ×10⁹/L; p < 0.001). The mean platelet volume was higher in the AH-CSU group (11.2 ± 0.3 fL) than in the CSU group (11.1 ± 0.4 fL; p = 0.002) and in the control group (10.3 ± 0.4 fL; p < 0.001). There were no significant differences in the mean levels of lymphocytes, monocytes, eosinophils, basophils, and platelets, and the rates of eosinopenia and basopenia between the patients in the AH-CSU group who responded to and those who were resistant to omalizumab. Conclusion: This study provided additional data of interest to examine the pathophysiologic role of low-grade inflammation and basopenia in patients with CSU and resistant to AHs and omalizumab.

Effects of omalizumab on basophils: Potential biomarkers in asthma and chronic spontaneous urticaria

Omalizumab is an anti-IgE humanized monoclonal antibody approved for the treatment of severe asthma and chronic spontaneous urticaria. Omalizumab binds free serum IgE and antagonizes its interaction with FcεRI, which is considered the main pharmacodynamic mechanism responsible for the clinical response to the treatment. The reduction of IgE serum concentration down-regulates the cellular expression of FcεRI on basophils. However, the biological events occurring on basophils during the therapy with omalizumab are multiple and complex. Here we review the current evidence regarding the specific biological effects of omalizumab on basophils in patients with asthma and chronic spontaneous urticaria. In addition to the modulation of IgE receptors, omalizumab may affect basophils homeostasis, intra-cellular signaling, cellular responsiveness/activation and cytokine release. These effects may be partially responsible for the clinical success of omalizumab and potentially provide useful biological markers for future assessment of the clinical response to the treatment. However, further investigation is required to better elucidate the role of basophils during the treatment with omalizumab.

Improved FcεRI-Mediated CD203c Basophil Responsiveness Reflects Rapid Responses to Omalizumab in Chronic Spontaneous Urticaria

BACKGROUND

Omalizumab is effective in patients with chronic spontaneous urticaria (CSU) although its mechanism of action is poorly understood. Several studies reported that decreased high-affinity IgE receptor (FcεRI)-mediated histamine release and/or responsiveness was characteristic of basophils in patients with CSU. However, few studies have focused on the relationship between changes in basophil responsiveness via FcεRI after omalizumab treatment and the therapeutic effect in patients with CSU.

OBJECTIVE

To assess basophil responsiveness via FcεRI stimulation, as well as FcεRI expression and IgE binding on blood basophils from patients with CSU before and after omalizumab treatment and its possible association with the clinical response.

METHODS

We analyzed 34 patients with CSU treated with omalizumab who were categorized as fast responders (FRs) (n = 20) and non or slow responders (N/SRs) (n = 14). CD203c expression induced by FcεRI stimulation, and IgE and FcεRI expressions on blood basophils from patients with CSU before and after omalizumab treatment were analyzed. Basophil responsiveness via FcεRI stimulation was observed in vitro using basophils pretreated with omalizumab.

RESULTS

FRs had increased CD203c responsiveness after treatment with omalizumab compared with N/SRs. This improvement of basophil responsiveness via FcεRI stimulation in FRs was not observed in peripheral blood basophils preincubated with omalizumab in vitro, suggesting that omalizumab does not directly affect circulating pre-existing abnormal basophils.

CONCLUSION

Increased basophil responsiveness via FcεRI after omalizumab treatment is associated with the therapeutic effect and mechanism of action of omalizumab.

Response of FcεRI-bearing leucocytes to omalizumab in chronic spontaneous urticaria

BACKGROUND

The pathogenesis of chronic spontaneous urticaria (CSU) and the mechanism of action of omalizumab in CSU remain unclear.

OBJECTIVE

In this study, we assessed the responsiveness and FcεRI expression of various subsets of leucocytes in patients with CSU treated with omalizumab.

METHODS

In this prospective cohort study, 30 patients were treated with 6 administrations of 300 mg omalizumab every 4 weeks, followed by a follow-up period of 12 weeks. FcεRI expression and the percentage of basophils, monocytes, and dendritic cell subsets were analysed before and during treatment, and after follow-up. In addition, anti-IgE- and C5a-induced basophil degranulation was measured. The results were correlated with disease activity and response to omalizumab.

RESULTS

In addition to a rapid and significant reduction in FcεRI on basophils, we demonstrated a reduction in FcεRI on plasmacytoid dendritic cells during omalizumab treatment, which persisted until 3 months after discontinuation. FcεRI expression on basophils and its reduction did not correlate with the treatment response. Omalizumab led to an increased percentage of basophils in blood but not of the other FcεRI-bearing leucocytes. Basophil responsiveness was differentially affected; anti-IgE-, but not C5a-induced basophil degranulation increased during the treatment. Apart from clinical non-responders showing a stronger increase in anti-IgE-induced basophil degranulation over a period time, no differences were found in omalizumab responders vs non-responders.

CONCLUSIONS/CLINICAL RELEVANCE

FcεRI expression on basophils decreased rapidly, while anti-IgE-induced degranulation significantly increased due to omalizumab treatment in patients with CSU, persisting at least for 3 months after stopping the treatment. None of the markers were able to predict the effectiveness of treatment. Whether basophils play a role in omalizumab responsiveness in CSU remains unclear.