Mast cell silencing: A novel therapeutic approach for urticaria and other mast cell-mediated diseases

Chronic urticaria (CU) is a mast cell (MC)-dependent disease with limited therapeutic options. Current management strategies are directed at inhibiting IgE-mediated activation of MCs and antagonizing effects of released mediators. Due to the complexity and heterogeneity of CU and other MC diseases and mechanisms of MC activation-including multiple activating receptors and ligands, diverse signaling pathways, and a menagerie of mediators-strategies of MC depletion or MC silencing (i.e., inhibition of MC activation via binding of inhibitory receptors) have been developed to overcome limitations of singularly targeted agents. MC silencers, such as agonist monoclonal antibodies that engage inhibitory receptors (e.g., sialic acid-binding immunoglobulin-like lectin8 -[Siglec-8] [lirentelimab/AK002], Siglec-6 [AK006], and CD200R [LY3454738]), have reached preclinical and clinical stages of development. In this review, we (1) describe the role of MCs in the pathogenesis of CU, highlighting similarities with other MC diseases in disease mechanisms and response to treatment; (2) explore current therapeutic strategies, categorized by nonspecific immunosuppression, targeted inhibition of MC activation or mediators, and targeted modulation of MC activity; and (3) introduce the concept of MC silencing as an emerging strategy that could selectively block activation of MCs without eliciting or exacerbating on- or off-target, immunosuppressive adverse effects.

Patients With Chronic Spontaneous Urticaria Who Have Wheals, Angioedema, or Both, Differ Demographically, Clinically, and in Response to Treatment-Results From CURE

BACKGROUND

Patients with chronic spontaneous urticaria (CSU) have spontaneous wheals (W), angioedema (AE), or both, for longer than 6 weeks. Clinical differences between patients with standalone W, standalone AE, and W and AE (W+AE) remain incompletely understood.

OBJECTIVE

To compare W, AE, and W+AE CSU patients regarding demographics, disease characteristics, comorbidities, disease burden, and treatment response.

METHODS

Baseline data from 3,698 CSU patients in the ongoing, prospective, international, multicenter, observational Chronic Urticaria REgistry (CURE) were analyzed (data cut: September 2022).

RESULTS

Across all CSU patients, 59%, 36%, and 5% had W+AE, W, and AE, respectively. The W+AE patients, compared with W and AE patients, showed the lowest male-to-female ratio (0.33), higher rates of concomitant psychiatric disease (17% vs 11% vs 6%, respectively), autoimmune disease (13% vs 7% vs 9%, respectively), and nonsteroidal anti-inflammatory drug (NSAID) hypersensitivity (9% vs 5% vs 2%, respectively) and the highest disease impact. The W patients, compared with W+AE and AE patients, showed the lowest rates of concomitant hypertension (15% vs 21% vs 40%, respectively) and obesity (11% vs 16% vs 17%, respectively), the highest rate of concomitant inducible urticaria (24% vs 22% vs 6%, respectively), and shorter W duration. The AE patients, compared with W+AE and W patients, were older at disease onset, showed longer AE duration, and the best response to increased doses of H1-antihistamines (58% vs 24% vs 31%, respectively) and omalizumab (92% vs 67% vs 60%, respectively).

CONCLUSIONS

Our findings provide a better understanding of CSU phenotypes and may guide patient care and research efforts that aim to link them to pathogenic drivers.

An international Delphi study on the burden of allergic rhinoconjunctivitis and urticaria and the role of bilastine among current treatment options

BACKGROUND

allergic rhinoconjunctivitis and chronic urticaria are common histamine-driven diseases, exerting detrimental effects on cognitive functions, sleep, daily activities and quality of life. Non-sedating second-generation H₁-antihistamines are the first line treatment of choice. Aim of the study was to define the role of bilastine among second-generation H₁-antihistamines in the treatment of allergic rhinoconjunctivitis and urticaria in patients of different ages.

METHODS

an international Delphi study was carried out to assess consensus among experts from 17 European and extra-European countries on three main topics: 1) Burden of disease; 2) Current treatment options; 3) Specific characteristics of bilastine among second generation antihistamines.

RESULTS

here, we present the results obtained for a selection of 15 out of 27 consensus statements, focused on disease burden, role of second-generation antihistamines and bilastine profile. The rate of concordance was ≥ 98% for 4 statements, ≥ 96% for 6, ≥ 94% for 3, and ≥ 90% for 2.

CONCLUSIONS

the high degree of agreement obtained suggests a wide awareness of the burden of allergic rhinoconjunctivitis and chronic urticaria among experts from all over the world and reflect a broad consensus on the role of second generation antihistamines in general and of bilastine in particular for their management.

An evaluation of remission rates with first and second line treatments and indicators of antihistamine refractoriness in chronic urticaria

BACKGROUND

Guidelines recommend standard doses of antihistamines as first-line, and updosing of antihistamines as second-line treatment for the management of chronic urticaria (CU). However, remission rates with different types of first- and second-line treatments and indicators of antihistamine response are largely lacking in the literature.

OBJECTIVES

To examine response rates to first- and second-line treatments in CU, and to identify patient characteristics that can predict antihistamine treatment outcomes.

METHODS

We retrospectively analyzed treatment outcomes of 657 CU (556 chronic spontaneous urticaria (CSU), 101 chronic inducible urticaria (CIndU)) patients who had at least 3-months of follow-up data.

RESULTS

A standard dose of second generation antihistamines (sgAH) was effective in 43.1 % of the patients. An additional 28.8 % of patients were in remission with second-line treatments. Among patients whose disease was in remission with a standard dose of sgAHs, 14.8 % benefited from switching from their current sgAH to another sgAH. Updosing sgAHs, combination of two different sgAHs, sgAH and first generation H1-antihistamine combination, and sgAH and leukotriene receptor antagonist combination provided remission in 38.3 %, 35.8 %, 37.5 % and 25 % of patients who were given these treatments, respectively. Baseline UCT score ≤ 4, emergency referral and family history of CSU were found to be risk factors for antihistamine refractoriness in patients with CSU.

CONCLUSIONS

A step-wise approach to the management of CU is practical as more patients respond to treatment at each step. The presence of baseline UCT score ≤ 4, emergency referral and family history of CSU might be helpful to determine patients who require third-line treatments in advance.

Evidence for histamine release in chronic inducible urticaria – A systematic review

Background

Chronic inducible urticaria (CIndU) constitutes a group of nine different CIndUs in which pruritic wheals and/or angioedema occur after exposure to specific and definite triggers. Histamine released from activated and degranulating skin mast cells is held to play a key role in the pathogenesis of CIndU, but evidence to support this has, as of yet, not been reviewed systematically or in detail. We aim to characterize the role and relevance of histamine in CIndU.

Methods

We systematically searched 3 electronic databases (PubMed, Scopus, and Embase) for studies that reported increased serum or skin histamine concentration (direct evidence) or in vitro or ex vivo histamine release (indirect evidence) following trigger exposure.

Results

An initial total of 3,882 articles was narrowed down to 107 relevant studies of which 52 were in cold urticaria, 19 in cholinergic urticaria, 14 in heat urticaria, 10 in contact urticaria, 7 each in solar urticaria and vibratory angioedema, 4 each in symptomatic dermographism and aquagenic urticaria, and 3 in delayed pressure urticaria. The results of our review support that histamine has a key pathogenic role in the pathogenesis of all CIndUs, but it is not the sole mediator as evidenced by the often poor relationship between the level of histamine and severity of symptoms and the variable clinical efficacy of H1-antihistamines.

Conclusions

Histamine released from skin mast cells is a key driver of the development of signs and symptoms and a promising therapeutic target in CIndU.

Urticaria in Pregnancy and Lactation

Chronic urticaria (CU) is a mast cell-driven chronic inflammatory disease with a female predominance. Since CU affects mostly females in reproductive age, pregnancy is an important aspect to consider in the context of this disease. Sex hormones affect mast cell (MC) biology, and the hormonal changes that come with pregnancy can modulate the course of chronic inflammatory conditions, and they often do. Also, pregnancy-associated changes in the immune system, including local adaptation of innate and adaptive immune responses and skewing of adaptive immunity toward a Th2/Treg profile have been linked to changes in the course of inflammatory diseases. As of now, little is known about the effects of pregnancy on CU and the outcomes of pregnancy in CU patients. Also, there are no real-life studies to show the safety of urticaria medications during pregnancy. The recent PREG-CU study provided the first insights on this and showed that CU improves during pregnancy in half of the patients, whereas it worsens in one-third; and two of five CU patients experience flare-ups of their CU during pregnancy. The international EAACI/GA2LEN/EuroGuiDerm/APAAACI guideline for urticaria recommends adopting the same management strategy in pregnant and lactating CU patients; starting treatment with standard doses of second-generation (non-sedative) H1 antihistamines, to increase the dose up to 4-folds in case of no response, and to add omalizumab in antihistamine-refractory patients; but also emphasizes the lack of evidence-based information on the safety and efficacy of urticaria treatments during pregnancy. The PREG-CU study assessed treatments and their outcomes during pregnancy. Here, we review the reported effects of sex hormones and pregnancy-specific immunological changes on urticaria, we discuss the impact of pregnancy on urticaria, and we provide information and guidance on the management of urticaria during pregnancy and lactation.

The international EAACI/GA²LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis, and management of urticaria

This update and revision of the international guideline for urticaria was developed following the methods recommended by Cochrane and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) working group. It is a joint initiative of the Dermatology Section of the European Academy of Allergology and Clinical Immunology (EAACI), the Global Allergy and Asthma European Network (GA²LEN) and its Urticaria and Angioedema Centers of Reference and Excellence (UCAREs and ACAREs), the European Dermatology Forum (EDF; EuroGuiDerm), and the Asia Pacific Association of Allergy, Asthma and Clinical Immunology with the participation of 64 delegates of 50 national and international societies and from 31 countries. The consensus conference was held on 3 December 2020. This guideline was acknowledged and accepted by the European Union of Medical Specialists (UEMS). Urticaria is a frequent, mast cell-driven disease that presents with wheals, angioedema, or both. The lifetime prevalence for acute urticaria is approximately 20%. Chronic spontaneous or inducible urticaria is disabling, impairs quality of life, and affects performance at work and school. This updated version of the international guideline for urticaria covers the definition and classification of urticaria and outlines expert-guided and evidence-based diagnostic and therapeutic approaches for the different subtypes of urticaria.

A European survey of management approaches in chronic urticaria in children: EAACI pediatric urticaria taskforce

BACKGROUND

Although well described in adults, there are scarce and heterogeneous data on the diagnosis and management of chronic urticaria (CU) in children (0-18 years) throughout Europe. Our aim was to explore country differences and identify the extent to which the EAACI/GA²LEN/EDF/WAO guideline recommendations for pediatric urticaria are implemented.

METHODS

The EAACI Task Force for pediatric CU disseminated an online clinical survey among EAACI pediatric section members. Members were asked to answer 35 multiple choice questions on current practices in their respective centers.

RESULTS

The survey was sent to 2,773 physicians of whom 358 (13.8%) responded, mainly pediatric allergists (80%) and pediatricians (49.7%), working in 69 countries. For diagnosis, Southern European countries used significantly more routine tests (eg, autoimmune testing, allergological tests, and parasitic investigation) than Northern European countries. Most respondents (60.3%) used a 2^nd -generation antihistamine as first-line treatment of whom 64.8% updosed as a second line. Omalizumab was used as a second-line treatment by 1.7% and third line by 20.7% of respondents. Most clinicians (65%) follow EAACI/WAO/GA2LEN/EDF guidelines when diagnosing CU, and only 7.3% follow no specific guidelines. Some clinicians prefer to follow national guidelines (18.4%, mainly Northern European) or the AAAAI practice parameter (1.7%).

CONCLUSIONS

Even though most members of the Pediatric Section of EAACI are familiar with the EAACI/WAO/GA2LEN/EDF guidelines, a significant number do not follow them. Also, the large variation in diagnosis and treatment strengthens the need to re-evaluate, update, and standardize guidelines on the diagnosis and management of CU in children.

Efficacy and Safety of Non-brain Penetrating H1-Antihistamines for the Treatment of Allergic Diseases

H₁ receptor antagonists, known as H₁-antihistamines (AHs), inactivate the histamine H₁-receptor thereby preventing histamine causing the primary symptoms of allergic diseases, such as atopic dermatitis, pollinosis, food allergies, and urticaria. AHs, which are classified into first-generation (fgAHs) and second-generation (sgAHs) antihistamines, are the first line of treatment for allergic diseases. Although fgAHs are effective, they cause adverse reactions such as potent sedating effects, including drowsiness, lassitude, and cognitive impairment; anticholinergic effects, including thirst and tachycardia. Consequently, the use of fgAHs is not recommended for allergic diseases. Today, sgAHs, which are minimally sedating and, therefore, may be used at more effective doses, are the first-line treatment for alleviating the symptoms of allergic diseases. Pharmacologically, the use of sedating fgAHs is limited to antiemetics, anti-motion sickness drugs, and antivertigo drugs. The use of histamine H₁-receptor occupancy (H₁RO) based on positron emission tomography (PET) has been developed for the evaluation of brain penetrability. Based on the results of the H₁RO-PET studies, non-brain-penetrating AHs (nbpAHs) have recently been reclassified among sgAHs. The nbpAHs are rapidly acting and exhibit minimal adverse reactions and, thus, are considered first-line drugs for allergic diseases. In this review, we will introduce recent topics on the pharmacodynamics and pharmacokinetics of AHs and make recommendations for the use of nbpAHs as first-line treatment options for allergic diseases.

Predictors of treatment response in chronic spontaneous urticaria

The current therapeutic algorithm for chronic spontaneous urticaria (CSU), endorsed by the international guideline, entails treatment escalation from second-generation H₁ -antihistamines (sgAHs) to omalizumab and cyclosporine until complete response is achieved. Recently, several predictors of response to these treatment options have been described. Here, we discuss the most promising predictors of response and nonresponse to these treatments in CSU. A systematic search was performed by two independent researchers using the MEDLINE/PubMed database with specific keywords and 73 studies included in the review. Levels of evidence were categorized as strong (robust predictors), weak (emerging predictors) or no association, based on the outcome and number of studies available. High disease activity, high levels of C-reactive protein and D-dimer are robust predictors for a poor or no response to sgAHs. Poor or no response to omalizumab is robustly predicted by low serum levels of total IgE. A good response to cyclosporine is robustly predicted by a positive basophil histamine release assay, whereas low total IgE is an emerging predictor. The response to treatment with sgAHs, omalizumab and cyclosporine can be predicted by the use of markers that are readily available in routine clinical practice. Further studies are needed to confirm these predictors.

Interleukin-17 is a potential player and treatment target in severe chronic spontaneous urticaria

BACKGROUND

Chronic spontaneous urticaria (CSU) is considered an autoimmune disorder in 50% of cases at least, in which T- and mast cell mediators are considered to be the primary cause of symptoms. However, H₁ -antihistamines, cyclosporine A, and omalizumab fail to achieve complete symptom amelioration in up to 70% of patients. This suggests that other inflammatory pathways are involved and that additional and more effective treatments need to be developed.

OBJECTIVE

This preliminary report examines the possibility that interleukin-17 (IL-17), a cytokine involved in the pathogenesis of many autoimmune diseases, may contribute to CSU and its inhibition may offer a relevant therapeutic target.

METHODS

The expression of IL-17A in skin biopsies of 20 CSU patients and 10 healthy controls was determined by quantitative histomorphometry. We also assessed the response to secukinumab (anti-IL-17A) treatment patients of eight severe CSU (7-day urticaria activity score UAS7 32-40) who were H₁ -antihistamine and omalizumab-resistant.

RESULTS

Increased numbers of CD4+ T cells and mast cells were present in both lesional and non-lesional skin of CSU patients compared with healthy controls. Both types of cells were strongly positive for IL-17A and found to be in close proximity to each other. All eight patients treated with the anti-IL-17A antibody, secukinumab, showed significant improvement in CSU disease activity. The action of secukinumab was shown to be relatively slow in onset. The significant reduction in disease activity from baseline UAS7 was demonstrated to be 55% and 82% at 30 and 90 days, respectively.

CONCLUSIONS

These findings suggest that IL-17 is involved in the pathogenesis of CSU and that IL-17 should be investigated as a therapeutic target in future studies with larger numbers of patients.

Acetylcholine-induced whealing in cholinergic urticaria - What does it tell us?

BACKGROUND

Cholinergic urticaria (CholU) is characterized by the occurrence of itchy wheals induced by sweating. Intradermal injections of acetylcholine (ACh) have been proposed to help with diagnosing CholU and subgrouping of patients, but controlled studies are largely missing.

OBJECTIVE

To compare the rates of positive ACh test results in well characterized CholU patients and controls and to identify clinical features of CholU linked to ACh reactivity.

METHODS

Acetylcholine was injected intradermally into 38 CholU patients and 73 matched healthy controls. Wheal and flare skin responses were assessed after 15 and 30 min and correlated with clinical features of CholU.

RESULTS

At 15 min after intradermal injections of ACh, wheal and flare responses were significantly more frequent in CholU patients than healthy controls, wheals: 34 % vs.15% (P = 0.028); flares: 50 % vs.18 % (P <0.001). Also, wheals were 37 % and flares 172 % larger and of longer duration in CholU patients than in healthy controls (both P < 0.01). CholU patients with ACh-induced wheals (ACh⁺) had larger flare but not wheal responses in response to histamine than those without (ACh^-; P = 0.011). Also, ACh-induced wheal responses were significantly correlated with sweating (r = 0.54, P = 0.046) in CholU patients. Finally, wheal responses lasted longer in ACh⁺ than in ACh^- patients (P = 0.03).

CONCLUSION

Intradermal ACh testing does not allow for the identification of CholU patients due to its low sensitivity. ACh-induced wheals, in patients with CholU, is linked to sweating and longer lasting symptoms. Intradermal ACh testing is an interesting tool for mechanistic studies in CholU.

Total IgE as a Marker for Chronic Spontaneous Urticaria

OBJECTIVE

Immunoglobulin E (IgE) and its receptor, FcɛRI, importantly contribute to the pathophysiology of chronic spontaneous urticaria (CSU). Recent findings point to a possible role of total IgE as a marker of CSU disease activity, endotypes, and responses to treatment. The evidence in support of total IgE included in the diagnostic workup of patients with CSU has not yet been reviewed.

METHODS

Publications were searched via PubMed. The search terms used were "chronic urticaria" and "total IgE." Studies were screened by titles and abstracts, and 141 were used in the review.

RESULTS

CSU patients frequently had elevated total IgE serum levels (up to 50%), but normal or very low total IgE levels also occurred. High total IgE may represent high disease activity, longer disease duration, high chance of responding to omalizumab treatment, quick relapse after stopping omalizumab, and lower chance of responding to cyclosporine. Low IgE, in contrast, may suggest Type IIb autoimmune CSU, poor response to treatment with omalizumab and a better chance to benefits from cyclosporine treatment. Furthermore, IgE in different CSU cohorts may have different physicochemical properties that could explain differences in treatment responses to IgE-directed therapies.

CONCLUSION

The results of our review suggest that total IgE is a valuable marker for CSU, and we recommend its assessment in the routine diagnostic workup of CSU patients.

IgM and IgA in addition to IgG autoantibodies against FcɛRIα are frequent and associated with disease markers of chronic spontaneous urticaria

BACKGROUND

IgG autoantibodies against the high-affinity IgE receptor, FcɛRIα, contribute the pathogenesis of autoimmune chronic spontaneous urticaria (CSU). However, it is not known whether such patients also exhibit IgM or IgA autoantibodies against FcɛRIα. To address this question we developed an ELISA to assess serum levels of IgG, IgM, and IgA autoantibodies against FcɛRIα and investigated whether their presence is linked to clinical features of CSU including the response to autologous serum skin testing (ASST).

METHODS

Serum samples of 35 CSU patients (25 ASST-positive) and 52 healthy control individuals were analyzed using a newly developed competitive ELISA for IgG, IgM, and IgA autoantibodies to FcɛRIα.

RESULTS

One in four CSU patients (8/35, 24%) had elevated serum levels of IgG-anti-FcɛRIα compared with (3/52, 6%) healthy controls. More than half of patients had IgM (21/35, 60%) and IgA (20/35, 57%) vs (3/52, 5%) each in healthy controls. Elevated IgM, but not IgG or IgA, autoantibodies were significantly more frequent in ASST-positive CSU patients (18/25, 72%) compared with ASSTnegative patients (3/10, 33%, P = .022). Also, elevated levels of IgM-anti-FcɛRIα, but not of IgG or IgA against FcɛRIα, were linked to low blood basophil (r = .414, P = .021) and eosinophil (r = .623, P < .001) counts.

CONCLUSIONS

Increased serum levels of IgM-anti-FcɛRIα are common in patients with CSU and linked to features of autoimmune CSU. The role and relevance of autoantibodies to FcɛRIα in CSU can and should be further characterized in future studies, and our novel assay can help with this.

Bilastine: a lifetime companion for the treatment of allergies

Objective: Bilastine is a potent and highly selective H₁-antihistamine approved for the treatment of allergic rhinoconjunctivitis and urticaria. This article summarizes available data on the use of bilastine in the treatment of allergic disorders in different age groups, including younger and older adults, and school-age children and adolescents.Methods: A PubMed literature search ("bilastine") was conducted on 25 February 2019. Additional literature known to the authors and identified from the reference lists of cited publications was included.Results: Bilastine is administered orally at a dose of 20 mg once daily in adults and adolescents aged ≥12 years and 10 mg once daily in children aged 6 to <12 years. Clinical trials have demonstrated its efficacy at improving nasal and ocular symptoms in patients with allergic rhinitis, and wheals and itching in patients with urticaria. It has a rapid onset of action and long duration of action. Bilastine does not undergo significant metabolism and does not interact with the CYP450 system, which limits its potential for drug-drug interactions. No dosage adjustments are required in patients with renal or hepatic impairment, or in the elderly. Bilastine is generally well tolerated, even when administered at above-standard doses. It does not exhibit anticholinergic effects or cardiotoxic effects, shows no central nervous system penetration and has minimal sedative properties. It has been shown to improve health-related quality of life.Conclusions: Bilastine is a suitable option for the treatment of patients with allergic rhinoconjunctivitis or urticaria across age groups from school-age children to elderly patients.

Biomarkers and clinical characteristics of autoimmune chronic spontaneous urticaria: Results of the PURIST Study

BACKGROUND

Autoimmune chronic spontaneous urticaria (aiCSU) is an important subtype of chronic spontaneous urticaria (CSU) in which functional IgG autoantibodies to IgE or its high-affinity receptor (FcεRI) induces mast cell degranulation and subsequent symptom development. However, it has not been tightly characterized. This study aimed to better define the clinical and immunological features and to explore potential biomarkers of aiCSU.

METHODS

This was a multinational, multicenter study of 182 CSU patients. The clinical features studied included: urticaria activity and impact (UAS7 and quality of life); autologous serum skin test (ASST); IgG anti-FcεRI and IgG anti-IgE; IgG-anti-thyroperoxidase (IgG anti-TPO); total serum IgE; and basophil reactivity (BASO) using the basophil activation test (BAT) and basophil histamine release assay (BHRA).

RESULTS

Of the 182 patients, 107 (59%) were ASST+, 46 (25%) were BASO+, and 105 (58%) were IgG anti-FcεRI+/IgE+. Fifteen patients (8%) fulfilled all three criteria of aiCSU. aiCSU patients appeared more severe (UAS7 21 vs 9 P < 0.016) but showed no other clinical or demographic differences from non-aiCSU patients. aiCSU patients also had markedly lower total IgE levels (P < 0.0001) and higher IgG anti-TPO levels (P < 0.001). Of biomarkers, positive BAT and BHRA tests were 69% and 88% predictive of aiCSU, respectively.

CONCLUSIONS

aiCSU is a relatively small but immunologically distinct subtype of CSU that cannot be identified by routine clinical parameters. Inclusion of BHRA or BAT in the diagnostic workup of CSU patients may aid identification of aiCSU patients, who may have a different prognosis and benefit from specific management.

Eosinopenia, in Chronic Spontaneous Urticaria, Is Associated with High Disease Activity, Autoimmunity, and Poor Response to Treatment

BACKGROUND

Chronic spontaneous urticaria (CSU) is characterized by the degranulation of skin mast cells and the influx of basophils and eosinophils to affected skin sites. Blood basopenia has been linked to severe antihistamine-resistant CSU and type IIb autoimmunity, whereas the role of eosinophils in CSU is largely unknown.

OBJECTIVE

To analyze data from 1613 patients with CSU from 2 centers to study the prevalence, role, and relevance of eosinopenia in CSU.

METHODS

Peripheral blood eosinophil and basophil counts were measured by automated hematology analyzers. Patient files were screened for clinical characteristics, results of laboratory tests, the autologous serum skin test, the serum-induced basophil histamine release assay, and response to second-generation H₁-antihistamines and omalizumab.

RESULTS

Ten percent of patients with CSU had eosinopenia. Eosinopenia was associated with the female sex, high disease activity, autologous serum skin test and basophil histamine release assay positivity, low total IgE, and high levels of C-reactive protein and IgG-antithyroperoxidase (P ≤ .007). Nonresponders to second-generation H₁-antihistamines or omalizumab had significantly lower eosinophils as compared with responders (P < .05 and P < .01, respectively). Blood eosinophil counts correlated with basophil counts (r = 0.396; P < .001), and 81% of patients with CSU with undetectable eosinophils had basopenia. The combination of eosinopenia and basopenia is a better predictor of nonresponse to second-generation H₁-antihistamines than eosinopenia alone (odds ratio of 9.5 vs 4.8).

CONCLUSIONS

Eosinopenia in patients with CSU is associated with type IIb autoimmunity, high disease activity, and poor response to treatment. Eosinophils should be explored as biomarkers and investigated for their contribution to the pathogenesis of CSU.

Characterization of cowhage-induced pruritus in inflamed and non-inflamed skin

BACKGROUND AND OBJECTIVE

Pruritus is a major symptom of many inflammatory diseases and impacts greatly the quality of life in patients. We aimed to specify the characteristics of experimentally induced pruritus in normal skin and in experimentally induced inflammatory dermatitis in healthy volunteers.

METHODS

Skin inflammation was induced by the repeated application of sodium lauryl sulphate (SLS 2%) on the volar forearms of 30 healthy volunteers. Inflammatory dermatitis intensity was assessed using the eczema score adapted from Frosch and Kligman. Non-histaminergic pruritus was induced by cowhage spicules rubbed on the volar forearms and recorded for 30 min on a 10-cm visual analogue scale (VAS) in both non-inflamed and inflamed skin.

RESULTS

Induction of inflammatory dermatitis by SLS resulted in a mild inflammatory dermatitis with an inflammation score of 2.3 ± 0.1 within 7 days of treatment. Cowhage-induced pruritus was of markedly higher intensity (P < 0.001), and all but two individuals had higher maximum pruritus intensity in inflamed skin as compared to non-inflamed skin, whereas the kinetics of the pruritus response were similar. The quality of cowhage-induced pruritus was significantly different with more 'burning' and 'painful sensations' in inflamed skin (P < 0.01). Maximum pruritus intensity in inflamed skin strongly correlated with maximum pruritus intensity in non-inflamed skin (r = 0.51, P = 0.004). Skin hydration, skin barrier integrity and dermatitis severity did not correlate with pruritus intensity.

CONCLUSION

Taken together, pruritus in inflamed skin is perceived as more intense, painful and burning. This may explain, in part, why pruritus is a major driver of quality-of-life impairment in patients with chronic inflammatory skin conditions such as atopic dermatitis.

Skin microdialysis: methods, applications and future opportunities-an EAACI position paper

Skin microdialysis (SMD) is a versatile sampling technique that can be used to recover soluble endogenous and exogenous molecules from the extracellular compartment of human skin. Due to its minimally invasive character, SMD can be applied in both clinical and preclinical settings. Despite being available since the 1990s, the technique has still not reached its full potential use as a tool to explore pathophysiological mechanisms of allergic and inflammatory reactions in the skin. Therefore, an EAACI Task Force on SMD was formed to disseminate knowledge about the technique and its many applications. This position paper from the task force provides an overview of the current use of SMD in the investigation of the pathogenesis of chronic inflammatory skin diseases, such as atopic dermatitis, chronic urticaria, psoriasis, and in studies of cutaneous events during type 1 hypersensitivity reactions. Furthermore, this paper covers drug hypersensitivity, UVB-induced- and neurogenic inflammation, and drug penetration investigated by SMD. The aim of this paper is to encourage the use of SMD and to make the technique easily accessible by providing an overview of methodology and applications, supported by standardized operating procedures for SMD in vivo and ex vivo.

On the Lipophilic Nature of Autoreactive IgE in Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is a skin disease related to autoreactive IgE in at least a subgroup of patients. However, the nature of this autoreactive IgE remains poorly characterized. This investigation had three objectives: first, to quantity CSU autoreactive IgE; second, to recognize the patterns of CSU autoreactive IgE compared with healthy control IgE; and third, to investigate the physiochemical nature of CSU autoreactive IgE.

Methods: IgE autoreactivity was assessed in sera from 7 CSU and 7 healthy individuals. Autoantigen recognition patterns were assessed using principal component analysis (PCA) and heatmap visualization. Lipophilicity was assessed using NanoOrange reagent.

Results: First, although total IgE levels did not differ significantly, the autoreactive proportion of IgE of CSU patients was 62% ± 37%, 1000-fold higher than that of healthy controls 0.03% ± 0.008% (P = 0.0006). Second, CSU autoreactive IgE differed from healthy control IgE by recognizing more and different autoantigens (226 vs. 34; P = 0.01). Third, the median (with 10-90% percentiles) serum level of lipophilic IgE was 39% (38-40%) in 232 CSU patients, 1.4-fold higher than the 28% (26-29%) of 173 healthy controls (P < 0.0001). Furthermore, lipophilicity correlated with autoreactivity (r = 0.8; P < 0.0001), connecting these two observed features.

Conclusion: We believe that these novel observations about CSU autoreactive IgE, particularly the finding that it is more lipophilic than that of IgE from healthy individuals, will lead to the development of new diagnostic tests and therapies for autoreactive IgE-mediated diseases.

The Role of Histamine and Histamine Receptors in Mast Cell-Mediated Allergy and Inflammation: The Hunt for New Therapeutic Targets

Histamine and its receptors (H1R–H4R) play a crucial and significant role in the development of various allergic diseases. Mast cells are multifunctional bone marrow-derived tissue-dwelling cells that are the major producer of histamine in the body. H1R are expressed in many cells, including mast cells, and are involved in Type 1 hypersensitivity reactions. H2R are involved in Th1 lymphocyte cytokine production. H3R are mainly involved in blood–brain barrier function. H4R are highly expressed on mast cells where their stimulation exacerbates histamine and cytokine generation. Both H1R and H4R have important roles in the progression and modulation of histamine-mediated allergic diseases. Antihistamines that target H1R alone are not entirely effective in the treatment of acute pruritus, atopic dermatitis, allergic asthma, and other allergic diseases. However, antagonists that target H4R have shown promising effects in preclinical and clinical studies in the treatment of several allergic diseases. In the present review, we examine the accumulating evidence suggesting novel therapeutic approaches that explore both H1R and H4R as therapeutic targets for histamine-mediated allergic diseases.

Immunoglobulin E-Mediated Autoimmunity

The study of autoimmunity mediated by immunoglobulin E (IgE) autoantibodies, which may be termed autoallergy, is in its infancy. It is now recognized that systemic lupus erythematosus, bullous pemphigoid (BP), and chronic urticaria, both spontaneous and inducible, are most likely to be mediated, at least in part, by IgE autoantibodies. The situation in other conditions, such as autoimmune uveitis, rheumatoid arthritis, hyperthyroid Graves’ disease, autoimmune pancreatitis, and even asthma, is far less clear but evidence for autoallergy is accumulating. To be certain of an autoallergic mechanism, it is necessary to identify both IgE autoantibodies and their targets as has been done with the transmembrane protein BP180 and the intracellular protein BP230 in BP and IL-24 in chronic spontaneous urticaria. Also, IgE-targeted therapies, such as anti-IgE, must have been shown to be of benefit to patients as has been done with both of these conditions. This comprehensive review of the literature on IgE-mediated autoallergy focuses on three related questions. What do we know about the prevalence of IgE autoantibodies and their targets in different diseases? What do we know about the relevance of IgE autoantibodies in different diseases? What do we know about the cellular and molecular effects of IgE autoantibodies? In addition to providing answers to these questions, based on a broad review of the literature, we outline the current gaps of knowledge in our understanding of IgE autoantibodies and describe approaches to address them.

Potential blood biomarkers in chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is a mast cell-driven disease that is defined as the recurrence of weals, angioedema or both for > 6 weeks due to known or unknown causes. As of yet, disease diagnosis is purely clinical. Objective tools are needed to monitor the activity of CSU and the efficacy of treatment. Recently, several reports have suggested that blood parameters may be considered as potential disease-related biomarkers. Here, we reviewed available literature on blood biomarkers for CSU diagnosis, activity monitoring, duration, patient subgroup allocation or response to treatment. We performed a PubMed, Google Scholar and Web of Science search and identified and analysed 151 reports published prior to January 2016. We found strong evidence for significant differences between patients with CSU and healthy controls in blood levels or values of D-dimer, C-reactive protein (CRP), matrix metalloproteinase-9 (MMP-9), mean platelet volume (MPV), factor VIIa, prothrombin fragment 1 + 2 (F1 + 2), tumour necrosis factor, dehydroepiandrosterone sulphate and vitamin D. Also, there is strong evidence for a significant association between CSU activity and blood levels or values of D-dimer, F1 + 2, CRP, IL-6 and MPV. Strong evidence for reduced basophil count and high levels of IgG anti-FcεRI in the subgroup of CSU patients with positive autologous serum skin test was shown. In contrast, the evidence for all reported blood biomarkers for differentiating CSU from other diseases, or a role in prognosis, is weak, inconsistent or non-existent. Taken together, we identified 10 biomarkers that are supported by strong evidence for distinguishing patients with CSU from healthy controls, or for measuring CSU activity. There is a need for further research to identify biomarkers that predict outcome or treatment response in CSU.

Allergy, Histamine and Antihistamines

This chapter concentrates on the role in allergic disease of histamine acting on H₁-receptors. It is clear that allergy has its roots in the primary parasite rejection response in which mast cell-derived histamine creates an immediate hostile environment and eosinophils are recruited for killing. This pattern is seen in allergic rhinitis where the early events of mucus production and nasal itching are primarily histamine mediated whereas nasal blockage is secondary to eosinophil infiltration and activation. In asthma, the role of histamine is less clear. Urticaria is characterized by mast cell driven pruritic wheal and flare-type skin reactions that usually persist for less than 24 h. Although the events leading to mast cell degranulation have been unclear for many years, it is now becoming evident that urticaria has an autoimmune basis. Finally, the properties of first- and second-generation H₁-antihistamines and their role in allergic is discussed.

Bilastine: a new H1 -antihistamine with an optimal profile for updosing in urticaria

This review set out to examine published papers detailing the efficacy of bilastine in skin models and urticaria to assess whether it meets the optimal profile for updosing in urticaria, that is, strong clinical efficacy and freedom from unwanted side effects, particularly sedation. Bilastine is a highly effective H₁ -antihistamine even when used at the basic dose of 20 mg daily. Its facilitated uptake after oral dosage gives it a rapid onset and long duration of action. In both wheal and flare studies and in urticaria updosing fourfold showed increased effectiveness. With respect to somnolence, bilastine is a substrate for P-glycoprotein, a membrane pump which prevents it crossing the blood-brain barrier. Consequently, bilastine is a practically 'non-sedating' H₁ -antihistamine. In conclusion, the excellent profile of bilastine in both efficacy and safety make it the ideal H₁ -antihistamine for updosing the daily dose fourfold in difficult-to-treat urticaria as recommended by the EAACI/GA² LEN/EDF/WAO guideline for the management of urticaria.

Questions and answers in chronic urticaria: where do we stand and where do we go?

This supplement reports proceedings of the second international Global Urticaria Forum, which was held in Berlin, Germany in November 2015. In 2011, a report of the GA(2) LEN task force on urticaria outlined important and unanswered questions in chronic urticaria (CU). These included, but were not limited to, questions on the epidemiology and course of chronic spontaneous urticaria (CSU) [also called chronic idiopathic urticaria (CIU)], the resources allocated for the diagnosis and treatment of CSU, whether patients with angioedema as an isolated symptom can be regarded as a subgroup of CSU, and the efficacy and long-term safety of therapies. Many of these questions have been addressed by recent studies. Some of the answers obtained raise new questions. Here, we summarize some of the key insights on CU obtained over recent years, and we discuss old and new unmet needs and how to address them with future studies. We need to analyze the influence of recent advances in understanding of the burden of CU on patients and society, disease management and the CU patient journey. Our increased understanding of urticarial pathophysiology and consideration of the patient as a whole will need to be translated to better treatment algorithms and protocols. Actions to address these challenges include the 5th International Consensus Meeting on Urticaria, which will take place later this year. The formation of a global network of Urticaria Centers of Reference and Excellence over the next few years has also been proposed, with the aim of providing consistent excellence in urticaria management and a clear referral route, furthering knowledge of urticaria through additional research and educating/promoting awareness of urticaria.

Efficacy and safety of canakinumab in Schnitzler syndrome: A multicenter randomized placebo-controlled study

BACKGROUND

Schnitzler syndrome is an adult-onset autoinflammatory disease characterized by urticarial exanthema and monoclonal gammopathy accompanied by systemic symptoms such as fever, bone, and muscle pain. Up to now, approved treatment options are not available.

OBJECTIVE

We assessed effects of the anti-IL-1β mAb canakinumab on the clinical signs and symptoms of Schnitzler syndrome.

METHODS

In this phase II, randomized placebo-controlled multicenter study, 20 patients with active disease enrolled in 4 German study centers. Patients were randomly assigned to receive single subcutaneous canakinumab 150 mg or placebo injections for 7 days, followed by a 16-week open-label phase with canakinumab injections on confirmed relapse of symptoms. The primary end point was the proportion of patients with complete clinical response evaluated by physician global assessment at day 7. Key secondary end points included changes in patient-reported disease activity (Schnitzler activity score), inflammation markers (C-reactive protein and serum amyloid A), and quality-of-life assessments (Dermatology Life Quality Index and 36-item short form health survey).

RESULTS

The proportion of patients with complete clinical response at day 7 was significantly higher (P = .001) in the canakinumab-treated group (n = 5 of 7) than in the placebo group (n = 0 of 13). Levels of inflammation markers C-reactive protein and serum amyloid A and quality-of-life scores were significantly reduced in canakinumab-treated but not in placebo-treated individuals. Positive effects continued up to 16 weeks. Adverse events were manageable and included respiratory tract infections, gastrointestinal symptoms, and hypertension.

CONCLUSIONS

In this first placebo-controlled study, canakinumab was effective in patients with Schnitzler syndrome, and thus canakinumab may be further evaluated as a therapeutic option for this rare disease.

Ethyl cellulose nanocarriers and nanocrystals differentially deliver dexamethasone into intact, tape-stripped or sodium lauryl sulfate-exposed ex vivo human skin - assessment by intradermal microdialysis and extraction from the different skin layers

Understanding penetration not only in intact, but also in lesional skin with impaired skin barrier function is important, in order to explore the surplus value of nanoparticle-based drug delivery for anti-inflammatory dermatotherapy. Herein, short-term ex vivo cultures of (i) intact human skin, (ii) skin pretreated with tape-strippings and (iii) skin pre-exposed to sodium lauryl sulfate (SLS) were used to assess the penetration of dexamethasone (Dex). Intradermal microdialysis was utilized for up to 24h after drug application as commercial cream, nanocrystals or ethyl cellulose nanocarriers applied at the therapeutic concentration of 0.05%, respectively. In addition, Dex was assessed in culture media and extracts from stratum corneum, epidermis and dermis after 24h, and the results were compared to those in heat-separated split skin from studies in Franz diffusion cells. Providing fast drug release, nanocrystals significantly accelerated the penetration of Dex. In contrast to the application of cream and ethyl cellulose nanocarriers, Dex was already detectable in eluates after 6h when applying nanocrystals on intact skin. Disruption of the skin barrier further accelerated and enhanced the penetration. Encapsulation in ethyl cellulose nanocarriers delayed Dex penetration. Interestingly, for all formulations highly increased concentrations in the dialysate were observed in tape-stripped skin, whereas the extent of enhancement was less in SLS-exposed skin. The results were confirmed in tissue extracts and were in line with the predictions made by in vitro release studies and ex vivo Franz diffusion cell experiments. The use of 45kDa probes further enabled the collection of inflammatory cytokines. However, the estimation of glucocorticoid efficacy by Interleukin (IL)-6 and IL-8 analysis was limited due to the trauma induced by the probe insertion. Ex vivo intradermal microdialysis combined with culture media analysis provides an effective, skin-sparing method for preclinical assessment of novel drug delivery systems at therapeutic doses in models of diseased skin.

Atopic predisposition in cholinergic urticaria patients and its implications

BACKGROUND

Cholinergic urticaria (CholU) is a frequent chronic urticaria disorder with itchy weal and flare-type skin reactions in response to physical exercise or passive warming. A higher frequency of atopy among CholU patients has been reported, but the significance of this observation is unclear.

OBJECTIVE

To assess the prevalence and relevance of atopy in CholU patients.

MATERIALS AND METHODS

Thirty CholU patients were assessed for atopic skin diathesis (atopic predisposition) by use of the Erlangen Atopy Score and divided into atopic and non-atopic predisposed CholU individuals. Both groups were assessed for disease severity (CholUSI) and activity (CholUAS7), quality of life impairment [Dermatology Life Quality Index (DLQI) and CU-Q₂ OL], seasonal exacerbation, total and specific serum IgE and comorbidities.

RESULTS

CholU patients were found to exhibit high rates of atopic predisposition (57%), with higher prevalence and scores in female than in male patients. High Erlangen Atopy Scores were linked to high CholU severity, activity and impact on QoL. Atopic predisposed CholU patients show different seasonal exacerbation patterns, IgE specificity and comorbidity profiles as compared to non-atopic CholU patients.

CONCLUSION

Atopic predisposition and cholinergic urticaria appear to be linked more closely than previously thought, which suggests shared pathogenetic mechanisms. Atopic patients with cholinergic urticaria have more severe disease and poorer quality of life than those who do not. Thus, all cholinergic urticaria patients should be assessed for atopic predisposition.