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1.  Omalizumab Increases the Intrinsic Sensitivity of Human Basophils to IgE-Mediated Stimulation 
Treatment of allergic patients with omalizumab results in a paradoxical increase in their basophil histamine release response, ex vivo, to crosslinking anti-IgE antibody. It is not known whether this change in response is associated with an increase in intrinsic cellular sensitivity, which would be a paradoxical response.
To determine if the increase in response to anti-IgE Ab is a reflection of an increased cellular sensitivity, expressed as molecules of antigen-specific IgE per basophil required to produce a 50% of maximal response.
Patients were treated with omalizumab or placebo agent for 12 weeks (NCT01003301 at and the metric of basophil sensitivity was assessed at 4 time points, baseline, 6–8 weeks, 12 weeks (after which treatment stopped) and 24 weeks (12 weeks after the end of treatment).
As observed previously, treatment with omalizumab resulted in a marked increase in the maximal histamine release induced by crosslinking anti-IgE Ab. This change was accompanied by a marked shift in intrinsic basophil sensitivity, ranging from 2.5 to 125 fold, with an average of 6 fold at the midpoint of the treatment to 12 fold after 12 weeks. The magnitude of the increase in cellular sensitivity was inversely related to the starting sensitivity or the starting maximum histamine release. The increased cellular sensitivity also occurred when using LTC4 secretion as a metric of the basophil response. 12 weeks after the end of treatment, cellular sensitivity was found to shift towards the baseline level although the return to baseline was not yet complete at this time point.
Treatment with omalizumab results in a markedly increased sensitivity of basophils to IgE-mediated stimulation, in terms of the number of IgE molecules required to produce a given response. These results provide a better quantitative sense of the phenotypic change that occurs in basophils during omalizumab treatment which has implications both mechanistic and clinical.
PMCID: PMC4302343  PMID: 23791510
Human; Basophil; Allergy; Fc Receptors
2.  Update on the Performance and Application of Basophil Activation Tests 
The basophil activation test (BAT) is a flow-cytometry-based functional assay that assesses the degree of cell activation after exposure to a stimuli. Though no standardized technique currently exists, recent advances have improved the performance of this assay, including identification of new basophil-specific markers and comparisons of the expression of CD63 to CD203c during activation. The basophil activation test has also been validated for many IgE-mediated disease conditions, which have been extensively reviewed elsewhere. This review focuses on the most recent applications of this test to the diagnosis of allergy to drugs, foods, venoms, and pollens, and the evolving role of the BAT in monitoring immunotherapy.
PMCID: PMC4078398  PMID: 23188565
Basophil activation test; Basophil; CD63; CD203c; CCR3; Food allergy; Drug allergy; Venom hypersensitivity; Immunotherapy
3.  Kinetics of mast cell, basophil, and oral food challenge responses in omalizumab-treated adults with peanut allergy 
Monoclonal antibodies directed at IgE demonstrate clinical efficacy in subjects with peanut allergy, but previous studies have not addressed the kinetics of the clinical response or the role of mast cells and basophils in the food-induced allergic response.
We sought to determine the kinetics of the clinical response to omalizumab and whether clinical improvement is associated with either mast cell or basophil suppression.
Subjects with peanut allergy were treated with omalizumab for 6 months and assessed for clinical and cellular responses. At baseline, subjects had a double-blind, placebo-controlled oral food challenge (OFC), skin prick test titration (SPTT), and basophil histamine release (BHR) to peanut. BHR was repeated at week 2 and then weekly until it decreased to less than 20% of baseline values. The OFCs and SPTTs were repeated after the BHR reduction (or at week 8 if BHR did not decrease) and again at 6 months.
Fourteen subjects enrolled in the study. At the second food challenge, there was a significant increase in the threshold dose of peanut inducing allergic symptoms (80 to 6500 mg, P < .01). Peanut-induced BHR was either completely suppressed (n = 5) or 10-fold more allergen was required to induce maximal BHR (n = 9), and SPTT responses were not significantly changed from baseline. After 6 months of omalizumab, further changes in the OFC threshold dose or BHR were not observed, but a significant suppression in SPTTs was identified.
The clinical response to omalizumab occurs early in treatment when the basophil, but not the mast cell, is suppressed, supporting a role for the basophil in acute food reactions.
PMCID: PMC3935509  PMID: 22800401
Omalizumab; peanut allergy; oral food challenge; basophil; mast cell
4.  Suppression of the Basophil Response to Allergen During Treatment with Omalizumab is Dependent on Two Competing Factors 
A recent study of peanut allergic subjects treated with omalizumab generated some results that were concordant with a study of cat allergics being treated with omalizumab. However, there were differences that provided additional insights into the nature of the cellular responses in allergic patients.
Determine the cause for failure to suppress the allergen-induced basophil response during treatment with omalizumab.
Peanut allergic patients were treated with omalizumab. Clinical, serological and cellular indices relevant to the response of the patient and their peripheral blood basophils (specific-to-total IgE ratio, cell surface FceRI expression, histamine release responses to anti-IgE Ab or peanut allergen) were obtained at 3 times.
Following treatment, approximately 60% of the subjects’ basophil responses to peanut allergen did not significantly decrease. In 40% of cases, the in vitro basophil response to peanut allergen increased 2–7 fold. The increases were associated with two primary factors, a high (>10%) specific-to-total IgE ratio and an increase in the intrinsic response of the basophil to IgE-mediated stimulation. The extent to which the basophil response to peanut allergen increased was inversely correlated with the improvement in the individual’s ability to tolerate ingestion of peanut.
The basophil response during treatment with omalizumab is a consequence of two competing factors, suppression of allergen-specific IgE on the cell surface vs. increased intrinsic sensitivity to IgE-mediated stimulation. In peanut allergy, the basophil response appears to mitigate against the ability of omalizumab to improve the patients’ tolerance of oral allergen.
PMCID: PMC3488135  PMID: 22800400
basophil; anti-IgE; peanut; syk; IgE receptor
5.  Assessing basophil functional measures during monoclonal anti-IgE therapy 
Journal of immunological methods  2012;383(1-2):60-64.
Several decades of work support that measures of allergen responses of IgE-bearing peripheral blood basophils can reflect clinical expression of allergic disease. Basophils are recognized to respond to allergen exposure with a variety of pro-inflammatory mediators such as histamine, leukotrienes and cytokines such as IL-4 and IL-13. Furthermore, the suppression of established basophil allergen responses has been observed as a consequence of current treatments such as specific allergen immunotherapy (SIT) for allergic airways disease and most recently, in oral immunotherapy for food allergy. In the last decade, an immune-based therapy targeting IgE, omalizumab, has emerged as an adjunct treatment for a variety of allergic diseases. This monoclonal humanized IgG antibody specifically binds circulating IgE at a region in the Fc tail that prevents IgE attachment to high affinity IgE receptor (FcεRI) bearing cell types such as tissue mast cells and blood basophils. As a result of omalizumab capture of IgE, these cells have a significant reduction in surface-bound IgE, FcεRI receptor levels, and their capacity to respond to allergen exposure with mediator release. This review focuses on methods to monitor changes of basophil allergen reactivity with a focus on omalizumab therapy and the implications for clinical disease management.
PMCID: PMC3411906  PMID: 22664098
Basophils; Activation markers; Omalizumab
6.  Diagnosis and Treatment of Urticaria and Angioedema: A Worldwide Perspective 
Urticaria and angioedema are common clinical conditions representing a major concern for physicians and patients alike. The World Allergy Organization (WAO), recognizing the importance of these diseases, has contributed to previous guidelines for the diagnosis and management of urticaria. The Scientific and Clinical Issues Council of WAO proposed the development of this global Position Paper to further enhance the clinical management of these disorders through the participation of renowned experts from all WAO regions of the world. Sections on definition and classification, prevalence, etiology and pathogenesis, diagnosis, treatment, and prognosis are based on the best scientific evidence presently available. Additional sections devoted to urticaria and angioedema in children and pregnant women, quality of life and patient-reported outcomes, and physical urticarias have been incorporated into this document. It is expected that this article will supplement recent international guidelines with the contribution of an expert panel designated by the WAO, increasing awareness of the importance of urticaria and angioedema in medical practice and will become a useful source of information for optimum patient management worldwide.
PMCID: PMC3651155  PMID: 23282382
urticaria; angioedema
7.  Regulation of Syk Kinase and FcRβ Expression in Human Basophils During Treatment with Omalizumab 
In human basophils from different subjects, maximum IgE-mediated histamine release and the level of syk protein expression correlate well. Recent studies suggest that in some patients treated with omalizumab, the response to stimulation with anti-IgE antibody increases. In unrelated studies, there is also evidence that the composition of FcεRI in basophils differs among subjects. This observation raised the possibility that the stoichiometry of FcRβ:FcεRIα is not fixed to 1:1 and might be modifiable during changes in the basophil environment.
To determine if treatment with omalizumab results in increases in syk expression, anti-IgE-mediated histamine release and disproportionately alters the relative presence of FcRβ and FcεRIα.
Syk, FcεRIα, and FcRβ expression was monitored during the treatment of subjects with omalizumab.
Treatment with omalizumab reduced histamine release from peripheral blood leukocytes stimulated with cat-allergen in vitro, but histamine release stimulated with anti-IgE antibody increased 2 fold. Expression of syk increased 1.86 fold. There was no change in the expression of c-cbl, a signaling element that is sensitive to the presence of IL-3, and no increase in response to FMLP, a response that also increases in the presence of IL-3. There was a 60% decrease in the FcRβ:FcεRIα ratio in patients treated with omalizumab.
In the context of previous studies, these studies provide support for a proposal that syk expression is modulated in vivo by an IgE-dependent mechanism and that the ratio of FcεRI alpha and beta subunits in basophils is influenced by factors extrinsic to the cell.
PMCID: PMC2850964  PMID: 20236696
8.  Effects of Omalizumab on Basophil and Mast Cell Responses using an Intranasal Cat Allergen Challenge 
Omalizumab treatment suppresses FcεRI expression faster on blood basophils than skin mast cells.
We utilized omalizumab to elucidate the relative contributions of basophil versus mast cell FcεRI activation in a nasal allergen challenge (NAC) model.
Eighteen cat-allergic subjects were enrolled in a 3.5-month, double-blind, randomized (3.5:1), placebo-controlled trial of omalizumab using standard dosing. At baseline, subjects underwent NAC with lavage for PGD2 measurement, skin prick test titration (SPTT), and blood sampling for basophil histamine release (BHR) and basophil IgE/FcεRI measurements. Basophil studies were repeated at day 3 and then weekly until cat allergen-induced BHR was <20% of baseline or until day 45. Baseline visit procedures were repeated after the BHR reduction (mid-study NAC) and at the treatment period’s completion (final NAC).
Subjects treated with omalizumab who completed all NACs (n=12) demonstrated significant mean reduction in BHR to an optimal dose of cat allergen by mid-study NAC as compared to baseline (74% decrease, p=0.001). In addition, these subjects demonstrated significant decreases in mean combined nasal symptom scores (50% decrease, p=0.007) and total sneeze counts (59% decrease, p=0.01) by mid-study NAC relative to baseline NAC. In contrast, measures of mast cell response (SPTT and nasal lavage PGD2) were only significantly reduced by the final NAC. Subjects on placebo (n=4) did not experience a shift in basophil, NAC symptom, or mast cell measures.
Reduction in nasal symptom scores occurred when the basophil, but not mast cell, response was reduced on omalizumab, implicating a role for basophils in the acute NAC response.
PMCID: PMC2850969  PMID: 19962744
IgE; IgE receptors; omalizumab; basophils; mast cells; basophil histamine release; skin prick test titration; nasal allergen challenge; cat allergy
9.  Effect of in vitro aspirin stimulation on basophils in patients with aspirin-exacerbated respiratory disease 
Basophil activation has been implicated in the pathogenesis of aspirin exacerbated respiratory disease. However, a comprehensive analysis of basophil responses to aspirin in terms of mediator release, cytokine secretion and increased expression of surface activation markers has not been performed.
To study the in vitro effects of aspirin on the concurrent release of histamine, leukotriene C4 and IL-4 from human basophils and to also evaluate changes in surface activation markers (CD63, CD69 and CD203c) expressed by these cells.
Basophil-enriched cell suspensions from 10 patients with aspirin exacerbated respiratory disease and 10 healthy volunteers were incubated with lysine-aspirin for up to 3 hours. Cells were analysed for expression of CD63, CD69 and CD203c using flow cytometry. Cell-free supernatants were evaluated for histamine, and leukotriene C4 release and for IL-4 secretion.
Aspirin-induced expression of CD63, CD69 and CD203c yielded 30%, 80% and 70% sensitivity, respectively, but with poor specificity. There was no significant difference in leukotriene C4 synthesis between groups. None of the patients with aspirin exacerbated respiratory disease (or controls) released IL-4 in response to aspirin. A higher dose of 5 mg/ml aspirin mediated non-specific effects on basophils.
Basophil responses to in vitro aspirin challenge are poor indicators of clinical sensitivity. Aspirin activates some basophils by means of mechanisms which differ from the classical IgE mediated pathway. Our study also shows that the use of 27 mM of aspirin (5 mg/ml) used by previous investigators causes nonspecific basophil activation, thereby eliminating its usefulness in a cell based diagnostic test for AERD. Evaluation of in vitro basophil activation has low clinical value in identifying aspirin- induced respiratory reactions
PMCID: PMC2788679  PMID: 19486029
Aspirin; asthma; aspirin exacerbated respiratory disease; basophil; CD63; CD69; CD203c; histamine; leukotriene C4; flow cytometry
10.  Cultured Peripheral Blood Mast Cells from Chronic Idiopathic Urticaria Patients Spontaneously Degranulate Upon IgE Sensitization: Relationship to Expression of Syk and SHIP-2 
Clinical immunology (Orlando, Fla.)  2009;132(3):342-348.
Recently, signaling changes in the FcεRI pathway involving inositol lipid phosphatases have been identified in the basophils of chronic idiopathic urticaria (CIU) subjects. Based on the profile of basophil FcεRI-mediated histamine degranulation, we have segregated CIU subjects into two groups, CIU Responder (CIU R) or CIU Nonresponder (CIU NR). In the present study, we compared expression of SHIP-1, SHIP-2, and Syk protein to histamine release (HR) from mast cells (MC) cultured from the peripheral blood of CIU R, CIU NR, and normal subjects. The MC of CIU R donors contained significantly increased Syk and decreased SHIP-2 as compared to CIU NR (Syk: p=0.038: SHIP-2: p=0.038) and normals (Syk: p=0.042: SHIP-2: p=0.027). Spontaneous HR from CIU donors was increased two-fold compared to normals (p=0.04). In summary, our results suggest a possible predilection for urticarial MC to spontaneously degranulate upon IgE sensitization contributing to the increased pruritis associated with CIU.
PMCID: PMC2720433  PMID: 19477690
FcεRI; CD34+ stem cell; signal transduction; urticaria; mast cell
11.  New Concepts in Chronic Urticaria 
Current opinion in immunology  2008;20(6):709-716.
Chronic urticaria is a common skin disease without a clear etiology in the vast majority of cases. The similarity of symptoms and lesion pathology to allergen-induced skin reactions supports the idea that skin mast cell and blood basophil IgE receptor activation is involved, however, no exogenous allergen trigger has been identified. The presence of serum IgG autoantibodies targeting IgE or the IgE receptor in ∼40 % of CIU cases supports the theory of an autoimmune basis for the disease. However, issues remain with the assays to detect autoantibodies amongst other serum factors, the relationship of autoantibodies to CIU disease activity, and the occurrence of autoantibodies in healthy subjects. Other studies have identified altered IgE receptor degranulation that reverts in disease remission and is accompanied by changes in signaling molecule expression and function in mast cells and basophils in active CIU subjects. The arrival of therapies targeting IgE and the IgE receptor pathway elements has potential use in CIU.
PMCID: PMC2610333  PMID: 18832031
12.  Diagnostic evaluation of food-related allergic diseases 
Food allergy is a serious and potentially life-threatening problem for an estimated 6% of children and 3.7% of adults. This review examines the diagnostic process that begins with a patient's history and physical examination. If the suspicion of IgE-mediated food allergy is compelling based on the history, skin and serology tests are routinely performed to provide confirmation for the presence of food-specific IgE antibody. In selected cases, a provocation challenge may be required as a definitive or gold standard reference test for confirmation of IgE mediated reactions to food. Variables that influence the accuracy of each of the diagnostic algorithm phases are discussed. The clinical significance of food allergen-specific IgE antibody cross-reactivity and IgE antibody epitope mapping of food allergens is overviewed. The advantages and limitations of the various diagnostic procedures are examined with an emphasis on future trends in technology and reagents.
PMCID: PMC2776233  PMID: 19946406
13.  Efficacy and Safety of Omalizumab in Patients with Chronic Idiopathic/Spontaneous Urticaria Who Remain Symptomatic on H1 Antihistamines: A Randomized, Placebo-Controlled Study 
ASTERIA I was a 40-week, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of subcutaneous omalizumab as add-on therapy for 24 weeks in patients with chronic idiopathic urticaria/spontaneous urticaria (CIU/CSU) who remained symptomatic despite H1 antihistamine treatment at licensed doses. Patients aged 12–75 years with CIU/CSU who remained symptomatic despite treatment with approved doses of H1 antihistamines were randomized (1:1:1:1) in a double-blind manner to subcutaneous omalizumab 75 mg, 150 mg, or 300 mg or placebo every 4 weeks for 24 weeks followed by 16 weeks of follow-up. The primary end point was change from baseline in weekly itch severity score (ISS) at week 12. Among randomized patients (N=319: placebo n=80, omalizumab 75 mg n=78, 150 mg n=80, 300 mg n=81), 262 (82.1%) completed the study. Compared with placebo (n=80), mean weekly ISS was reduced from baseline to week 12 by an additional 2.96 points (95% confidence interval (CI): −4.71 to −1.21; P=0.0010), 2.95 points (95% CI: −4.72 to −1.18; P=0.0012), and 5.80 points (95% CI: −7.49 to −4.10; P<0.0001) in the omalizumab 75-mg (n=77), 150-mg (n=80), and 300-mg groups (n=81), respectively. The omalizumab 300-mg group met all nine secondary end points, including a significant decrease in the duration of time to reach minimally important difference response (⩾5-point decrease) in weekly ISS (P<0.0001) and higher percentages of patients with well-controlled symptoms (urticaria activity score over 7 days (UAS7) ⩽6: 51.9% vs. 11.3% P<0.0001) and complete response (UAS7=0: 35.8% vs. 8.8% P<0.0001) versus placebo. During the 24-week treatment period, 2 (2.9%), 3 (3.4%), 0, and 4 (5.0%) patients in the omalizumab 75-mg, 150-mg, 300-mg, and placebo groups, respectively, experienced a serious adverse event. Omalizumab 300 mg administered subcutaneously every 4 weeks reduced weekly ISS and other symptom scores versus placebo in CIU/CSU patients who remained symptomatic despite treatment with approved doses of H1 antihistamines.
PMCID: PMC4269803  PMID: 25046337

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