Kinetics of mast cell, basophil, and oral food challenge responses in omalizumab-treated adults with peanut allergy.
ABSTRACT BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
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ABSTRACT: Basophils have emerged in recent years as a small but potent subpopulation of leukocytes capable of bridging innate and adaptive immunity. They can be activated through IgE-dependent and IgE-independent mechanisms to release preformed mediators and to produce Th2 cytokines. In addition to their role in protective immunity to helminths, basophils are major participants in allergic reactions as diverse as anaphylaxis and immediate hypersensitivity reactions, late-phase hypersensitivity reactions, and delayed hypersensitivity reactions. Additionally, basophils have been implicated in the pathophysiology of autoimmune diseases such as lupus nephritis and rheumatoid arthritis, and the modulation of immune responses to bacterial infections, as well as being a feature of myelogenous leukemias. Distinct signals for activation, degranulation, transendothelial migration, and immune regulation are being defined, and demonstrate the important role of basophils in promoting a Th2 microenvironment. These mechanistic insights are driving innovative approaches for diagnostic testing and therapeutic targeting of basophils.Current Allergy and Asthma Reports 01/2014; 14(1):408. · 2.75 Impact Factor
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ABSTRACT: A large number of trials show that the anti-immunoglobulin (Ig) E antibody omalizumab is very effective in patients with severe allergic asthma. This is acknowledged in consensus documents. The drug also has a good safety profile and a pharmacoeconomic advantage due to a reduction in the number of hospitalizations for asthma attacks. In recent years, some studies have shown that omalizumab is effective also in nonallergic asthma. Effects on the complex signaling mechanisms leading to activation of effector cells and to mediator release may account for this outcome. Indeed, omalizumab has been reported to be effective in a number of IgE-mediated and non-IgE-mediated disorders. Concerning the former, clinical efficacy has been observed in rhinitis, allergic bronchopulmonary aspergillosis, latex allergy, atopic dermatitis, allergic urticaria, and anaphylaxis. In addition, omalizumab has been demonstrated to be able to prevent systemic reactions to allergen immunotherapy, thus enabling completion of treatment in patients who otherwise would have to stop it. Concerning non-IgE-mediated disorders, omalizumab has been reported to be effective in nasal polyposis, autoimmune urticaria, chronic idiopathic urticaria, physical urticaria, idiopathic angioedema, and mastocytosis. Current indications for treatment with omalizumab are confined to severe allergic asthma. Consequently, any other prescription can only be off-label. However, it is reasonable to expect that the use of omalizumab will be approved for particularly important indications, such as anaphylaxis, in the near future.Drug Design, Development and Therapy 01/2014; 8:197-207. · 3.49 Impact Factor
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ABSTRACT: Up to 30% of patients with food allergies have clinical reactivity to more than one food allergen. Although there is currently no cure, oral immunotherapy (OIT) is under investigation. Pilot data have shown that omalizumab may hasten the ability to tolerate over 4 g of food allergen protein. To evaluate the safety and dose tolerability of a Phase 1 Single Site OIT protocol using omalizumab to allow for a faster and safe desensitization to multiple foods simultaneously. Participants with multiple food allergies received OIT for up to 5 allergens simultaneously with omalizumab (rush mOIT). Omalizumab was administered for 8 weeks prior to and 8 weeks following the initiation of a rush mOIT schedule. Home reactions were recorded with diaries. Twenty-five (25) participants were enrolled in the protocol (median age 7 years). For each included food, participants had failed an initial double-blind placebo-controlled food challenge at a protein dose of 100 mg or less. After pre-treatment with omalizumab, 19 participants tolerated all 6 steps of the initial escalation day (up to 1250 mg of combined food proteins), requiring minimal or no rescue therapy. The remaining 6 were started on their highest tolerated dose as their initial daily home doses. Participants reported 401 reactions per 7,530 home doses (5.3%) with a median of 3.2 reactions per 100 doses. Ninety-four percent (94%) of reactions were mild. There was one severe reaction. Participants reached their maintenance dose of 4,000 mg protein per allergen at a median of 18 weeks. These phase 1 data demonstrate that rush OIT to multiple foods with 16 weeks of treatment with omalizumab could allow for a fast desensitization in subjects with multiple food allergies. Phase 2 randomized controlled trials are needed to better define safety and efficacy parameters of multi OIT experimental treatments with and without omalizumab.Allergy Asthma and Clinical Immunology 01/2014; 10(1):7.