Inhibition of allergen-specific IgE reactivity by a human Ig Fcγ-Fcε bifunctional fusion protein

University of California, Los Angeles, Los Ángeles, California, United States
Journal of Allergy and Clinical Immunology (Impact Factor: 11.48). 09/2004; 114(2):321-7. DOI: 10.1016/j.jaci.2004.03.058
Source: PubMed


Coaggregating FcepsilonRI with FcgammaRII receptors holds great potential for treatment of IgE-mediated disease by inhibiting FcepsilonRI signaling. We have previously shown that an Fcgamma-Fcepsilon fusion protein, human IgG-IgE Fc fusion protein (GE2), could inhibit FcepsilonRI-mediated mediator releases in vitro and in vivo.
We sought to test whether GE2 was capable of blocking mediator release from FcepsilonRI cells sensitized with IgE in vivo or in vitro before exposure to GE2, a critical feature for GE2 to be clinically applicable.
GE2 was tested for its ability to inhibit Fel d 1-induced mediator release from human blood basophils from subjects with cat allergy, human lung-derived mast cells, human FcepsilonRIalpha transgenic mice sensitized with human cat allergic serum, and rhesus monkeys naturally allergic to the dust mite Dermatophagoides farinae.
Basophils from subjects with cat allergy and lung mast cells degranulate when challenged with Fel d 1 and anti-IgE, respectively. GE2 itself did not induce mediator release but strongly blocked this Fel d 1- and anti-IgE-driven mediator release. GE2 was able to block Fel d 1-driven passive cutaneous anaphylaxis at skin sites sensitized with human serum from subjects with cat allergy in human FcepsilonRIalpha transgenic mice, but by itself, GE2 did not induce a passive cutaneous anaphylaxis reaction. Finally, GE2 markedly inhibited skin test reactivity to D farinae in monkeys naturally allergic to this allergen, with complete inhibition being observed at 125 ng.
GE2 is able to successfully compete for FcepsilonRs and FcgammaRs on cells presensitized in vitro and in vivo and lead to inhibition of IgE-mediated reactivity through coaggregation of FcepsilonRI with FcgammaRII.

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    • "This concept was exploited in recent studies using two novel bio-engineered fusion proteins, one that consists of human Fc regions of IgG1 and IgE linked together and another a fusion protein made by linking an allergen to human IgG1 Fc region[73]. These proteins block pro-inflammatory mediator and cytokine release from allergic cells and prevent skin, lung and systemic allergic reactivity in a murine model[16], [73]–[77]. Our study demonstrates that FcγRIIb-dependent regulatory mechanism(s) control allergic airway inflammation, making this inhibitory receptor a physiologically relevant therapeutic target in allergic asthma. "
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    ABSTRACT: Allergic asthma is characterized by airway eosinophilia, increased mucin production and allergen-specific IgE. Fc gamma receptor IIb (FcgammaRIIb), an inhibitory IgG receptor, has recently emerged as a negative regulator of allergic diseases like anaphylaxis and allergic rhinitis. However, no studies to date have evaluated its role in allergic asthma. Our main objective was to study the role of FcgammaRIIb in allergic lung inflammation. We used a murine model of allergic airway inflammation. Inflammation was quantified by BAL inflammatory cells and airway mucin production. FcgammaRIIb expression was measured by qPCR and flow cytometry and the cytokines were quantified by ELISA. Compared to wild type animals, FcgammaRIIb deficient mice mount a vigorous allergic lung inflammation characterized by increased bronchoalveolar lavage fluid cellularity, eosinophilia and mucin content upon ragweed extract (RWE) challenge. RWE challenge in sensitized mice upregulated FcgammaRIIb in the lungs. Disruption of IFN-gamma gene abrogated this upregulation. Treatment of naïve mice with the Th1-inducing agent CpG DNA increased FcgammaRIIb expression in the lungs. Furthermore, treatment of sensitized mice with CpG DNA prior to RWE challenge induced greater upregulation of FcgammaRIIb than RWE challenge alone. These observations indicated that RWE challenge upregulated FcgammaRIIb in the lungs by IFN-gamma- and Th1-dependent mechanisms. RWE challenge upregulated FcgammaRIIb on pulmonary CD14+/MHC II+ mononuclear cells and CD11c+ cells. FcgammaRIIb deficient mice also exhibited an exaggerated RWE-specific IgE response upon sensitization when compared to wild type mice. We propose that FcgammaRIIb physiologically regulates allergic airway inflammation by two mechanisms: 1) allergen challenge mediates upregulation of FcgammaRIIb on pulmonary CD14+/MHC II+ mononuclear cells and CD11c+ cells by an IFN-gamma dependent mechanism; and 2) by attenuating the allergen specific IgE response during sensitization. Thus, stimulating FcgammaRIIb may be a therapeutic strategy in allergic airway disorders.
    PLoS ONE 02/2010; 5(2):e9337. DOI:10.1371/journal.pone.0009337 · 3.23 Impact Factor
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    ABSTRACT: The expression of FcR by human skin-derived mast cells of the MCTC type was determined in the current study. Expression of mRNA was analyzed with microarray gene chips and RT-PCR; protein by Western blotting and flow cytometry; function by release of -hexosaminidase, PGD2, leukotriene C4 (LTC4), IL-5, IL-6, IL-13, GM-CSF, and TNF- .F cRIIa was consistently detected along with FcRI at the mRNA and protein levels; FcRIIc was sometimes detected only by RT-PCR; but FcRIIb, FcRI, and FcRIII mRNA and protein were not detected. FcRIIa-specific mAb caused skin MCTC cells to degranulate and secrete PGD2, LTC4, GM-CSF, IL-5, IL-6, IL-13, and TNF- in a dose-dependent fashion. FcRI-specific mAb caused similar amounts of each mediator to be released with the exception of LTC4, which was not released by this agonist. Simultaneous but independent cross-linking of FcRI and FcRIIa did not substantially alter mediator release above or below levels observed with each agent alone. Skin MCTC cells sensitized with dust-mite-specific IgE and IgG, when coaggregated by Der p2, exhibited enhanced degranulation compared with sensitization with either IgE or IgG alone. These results extend the known capabilities of human skin mast cells to respond to IgG as well as IgE-mediated signals. The Journal of Immunology, 2006, 177: 694 -701.
    The Journal of Immunology 06/2006; 177(1). DOI:10.4049/jimmunol.177.1.694 · 4.92 Impact Factor
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