1. Field of the Invention
The field of the invention is measuring processes involving non-membrane antibody-receptor binding, compositions therefore; and processes of forming such compositions.
2. Description of Related Art
The interaction of IgE antibodies with the high affinity IgE receptor, FcεRI, is a critical step in most allergic reactions. The IgE-receptor interaction has been well studied and targeted in the search for treatments for allergic diseases (Wiegand, T. W. et al. 1996 J Immunol 157: 221-230; Nakamura, G. R. et al. 2001 Biochemistry 40: 9828-9835; Stamos, J. et. al. 2004 Structure 12: 1289-1301; Chang, T. W. 2000 Nat Biotechnol 18: 157-162; Mirkina, I., Schweighoffer, T. & Kricek, F. 2007 Immunol Lett 109: 120-128). However, outside of the anti-IgE antibody Omalizumab, there are no compounds that have been identified and approved for the treatment of patients with severe allergies that interfere with the receptor binding. The identification of novel inhibitors of IgE antibody binding to its receptor would therefore represent a significant step forward in developing new approaches to treating allergy and asthma.
Allergic diseases have become the most common immune system disorder, affecting 10˜40% of the population in industrialized countries (Meltzer, E. O. & Grant, J. A. 1999 Ann Allergy Asthma Immunol 83: 455-463; Crater, S. E. & Platts-Mills, T. A. 1998 Curr Opin Pediatr 10: 594-599). Most allergic diseases are triggered by IgE-mediated hypersensitivity reactions (Kraft, S. & Kinet, J.P. 2007 Nat Rev Immunol 7: 365-378). While the primary function of IgE antibodies is to mediate immune response protection to foreign antigens, the overproduction of IgE antibodies to normally benign environmental stimuli, such as dust mites, pet dander, pollen, and mold, can result in inflammatory allergic reactions associated with asthma, allergic rhinitis, atopic dermatitis, and food allergies. IgE-mediated allergic reactions are initiated by the binding of the Fc domain of IgE to the high affinity IgE receptor (FcεRI) expressed on the surface of mast cells and basophils (Kinet, J. P. 1999 Annu Rev Immunol 17: 931-972; Gould, H. J. & Sutton, B. J. 2008 Nat Rev Immunol 8: 205-217). The binding of polyvalent antigens to the receptor-bound IgE leads to the release of histamines in mast cells, followed by the synthesis and release of prostaglandins, leukotrienes, and cytokines, stimulating additional inflammatory responses.
We have previously described a conformational change of IgE that has been observed by comparing the crystal structures of human IgE alone (IgE-Fc) (Wurzburg, B. A., Garman, S. C. & Jardetzky, T. S. 2000 Immunity 13: 375-385) to that of the IgE-Fc: FcεRI complex (Garman, S. C. et al. 2000 Nature 406: 259-266). The IgE heavy chain consists of the N-terminal variable domain followed by four constant domains. It is the C-terminal two constant domains (Cε3-Cε4) that mediate the high affinity binding to the receptor. The high affinity receptor is composed of three separate chains that assemble into an αβγ2 tetramer and it is the extracellular region of the α-chain of FcεRI that is directly involved in binding to the IgE (Nissim, A., Jouvin, M. H. & Eshhar, Z. 1991 Embo J 10: 101-107; Basu, M. et al. 1993 J Biol Chem 268: 13118-13127; Presta, L. et al. 1994 J Biol Chem 269: 26368-26373; Henry, A. J. et al. 1997 Biochemistry 36: 15568-15578). The comparison of these structures has provided evidence that in the receptor-bound state, the IgE-Fc is in an open conformation (Wurzburg, B. A., Garman, S. C. & Jardetzky, T. S. 2000 Immunity 13: 375-385), whereas in the free state, the IgE-Fc can adopt a closed conformation that cannot bind receptor (Garman, S. C. et al. 2000 Nature 406: 259-266). Recent studies of multiple crystal forms of the IgE-Fc demonstrate a range of conformations that the Fc region can adopt, although these are all more closed as compared to the conformation in the receptor-bound state.