Rapid desensitization of humanized mice with anti-human FcεRIα monoclonal antibodies

Abstract

Background: Anaphylaxis is classically mediated by allergen cross-linking of IgE bound to the a chain of FcεRI, the mast cell/basophil high affinity IgE receptor. Allergen cross-linking of the IgE/FcεRI complex activates these cells, inducing release of disease-causing mediators, cytokines, and enzymes. We previously demonstrated that IgE-mediated anaphylaxis could be safely prevented in wild-type BALB/c mice by rapid desensitization with anti-mouse FcεRIa mAb. Objective: This study sought to use humanized mice to extend these results to humans. Methods: We actively immunized huFcεRIa/F709 mice, which express human (hu) instead of mouse FcεRIa and a mutant IL-4 receptor that lacks inhibitory function. We passively immunized huFcεRIa mice, as well as human cord blood-reconstituted reNSGS mice, which are immune-deficient, produce mast cellstimulating human cytokines, and develop numerous human mast cells. For desensitization, we used anti-huFcεRIa mAbs that bind FcεRIa regardless of its association with IgE (noncompeting mAbs), and/or mAbs that compete with IgE for huFcεRIa binding (competing mAbs). Anaphylaxis was induced by intravenous injection of antigen or anti-huIgE mAb. Results: Anti-huFcεRIa mAb rapid desensitization was safer and more effective than allergen rapid desensitization and suppressed anaphylaxis more rapidly than omalizumab or ligelizumab. Rapid desensitization of na€ ıve, IgE-sensitized huFcεRIa mice and huFcεRIa/F709 mice that were egg-allergic with anti-FcεRIa mAbs safely removed >98% of IgE from peritoneal mast cells and completely suppressed IgE-mediated anaphylaxis. Rapid desensitization of reNSGS mice with anti-FcεRIa mAbs also safely removed 98% of mast cell IgE and prevented IgE-mediated anaphylaxis. Conclusions: Rapid desensitization with anti-FcεRIa mAbs may be a safe, effective, and practical way to prevent IgE-mediated anaphylaxis.

Mouse models of atopic dermatitis: a critical reappraisal

“…[126][127][128] "Humanized" mice are defined here as immunodeficient mice (SCID) that are xenotransplanted with relevant functional human biological systems, as opposed to "fully humanized" mice whose hematopoietic system has been reconstituted by a human one after mouse bone marrow radioablation. 129 While a humanized AD mouse model using human skin transplants has not yet been published, a very interesting humanized mouse model for acute human AD has recently been presented. This uses an in vitro-generated and transplanted human skin "equivalent" that is repetitively injected intradermally with Th2-polarized human CD4+ T lymphocytes over two weeks after partial removal of stratum corneum by tape-stripping.…”

“…Since none of the mouse “AD” models discussed above convincingly mimics enough of the relevant characteristics of human AD (Table 2), investigators have turned to so‐called “humanized” mice as being increasingly important in vivo models for the preclinical study of human skin pathology, including psoriasis and alopecia areata (Text ) 126‐128 . “Humanized” mice are defined here as immunodeficient mice (SCID) that are xenotransplanted with relevant functional human biological systems, as opposed to “fully humanized” mice whose hematopoietic system has been reconstituted by a human one after mouse bone marrow radioablation 129 …”

Suppression of IgE-mediated anaphylaxis and food allergy with monovalent anti-FcεRIα mAbs

“…[11][12][13][14] During the past few years, we have used conventional, then humanized mouse models to study the feasibility of using a rapid desensitization approach that replaces a single allergen with a mAb to FcεRIa (the IgE-binding chain of the FcεRI heterotetramer 15 ), with the goal of suppressing all IgE-mediated allergy rather than only disease caused by the single allergen. 12,16 Our studies have demonstrated the feasibility and efficacy of this approach, which, in addition to suppressing all IgE-mediated anaphylaxis was safer and longer lasting in our models than allergen-mediated desensitization was. 12 However, we also found that an extended period of treatment with very slow increases in anti-FcεRIa mAb dose was required to desensitize mice that were particularly susceptible to anaphylaxis.…”

“…BALB/c background huFcεRIa mice, which lack mouse FcεRIa and express transgenic huFcεRIa, and huFcεRIa/F709 mice, which additionally express IL-4Ra with a mutation (F709) that allows only positive signaling by IL-4 and IL-13, were bred as previously described. [16][17][18] These mice, unlike otherwise identical mice that lack the IL-4Ra F709 mutation, develop egg allergy in response to epicutaneous treatment, followed by oral gavage (og) with egg. 16 Human IL-3/SCF/GM-CSF transgenic, immune-deficient NOD/ LtSz-severe combined immunodeficiency IL-2RG 2/2 (NSGS) or NOD/ Rag1 2/2 /IL-2RG 2/2 mice were bred at a Cincinnati Children's Hospital Medical Center core and engrafted with T cell-depleted human cord blood cells as previously described.…”

“…12 However, we also found that an extended period of treatment with very slow increases in anti-FcεRIa mAb dose was required to desensitize mice that were particularly susceptible to anaphylaxis. 16 This limitation has led us to modify our approach by using an engineered monovalent (mv) anti-FcεRIa mAb for desensitization that has only 1 antigen-binding fragment (Fab), which is associated with complete Fc domains. We initially expected that because an mv antibody would bind to, but not cross-link with its target, it would be unable to either activate or desensitize basophils and mast cells, but could slow FcεRIa cross-linking by a subsequently injected divalent (dv) mAb that had the same variable (V) regions and was bound to the same FcεRIa epitope.…”