CTLA4-Cgamma4 fusion proteins

Abstract

CTLA4-immunoglobulin fusion proteins having modified immunoglobulin constant region-mediated effector functions, and nucleic acids encoding the fusion proteins, are described. The CTLA4-immunoglobulin fusion proteins comprise two components: a first peptide having a CTLA4 activity and a second peptide comprising an immunoglobulin constant region which is modified to reduce at least one constant region-mediated biological effector function relative to a CTLA4-IgG1 fusion protein. The nucleic acids of the invention can be integrated into various expression vectors, which in turn can direct the synthesis of the corresponding proteins in a variety of hosts, particularly eukaryotic cells. The CTLA4-immunoglobulin fusion proteins described herein can be administered to a subject to inhibit an interaction between a CTLA4 ligand (e.g., B7-1 and / or B7-2) on an antigen presenting cell and a receptor for the CTLA4 ligand (e.g. CD28 and / or CTLA4) on the surface of T cells to thereby suppress an immune response in the subject, for example to inhibit transplantation rejection graft versus host disease or autoimmune responses.

Description

BACKGROUND OF THE INVENTION[0001] To induce antigen-specific T cell activation and clonal expansion, two signals provided by antigen-presenting cells (APCs) must be delivered to the surface of resting T lymphocytes (Jenkins M. and Schwartz. R. (1987) J Exp. Med. 165:302-319; Mueller. D. L., et al. (1990) J Immunol. 144:3701-3709: Williams. I. R. and Unanue. E. R. (1990). J Immunol. 145:85-93). The first signal, which confers specificity to the immune response, is mediated via the T cell receptor (TCR) following recognition of foreign antigenic peptide presented in the context of the major histocompatibility complex (MHC). The second signal, termed costimulation, induces T cells to proliferate and become functional (Schwartz, R. H. (1990) Science 248:1349-1356). Costimulation is neither antigen-specific, nor MHC restricted and is thought to be provided by one or more distinct cell surface molecules expressed by APCs (Jenkins. M. K., et al. (1988) J Immunol. 140:3324-3330: Linsley, P....

AI Technical Summary

Benefits of technology

0012] Another aspect of the invention pertains to isolated CTLA4-immunoglobulin fusion proteins comprising a first peptide having a CTLA4 activity and a second peptide comprising an immunoglobulin constant region which is modified to reduce at least one constant region-mediated biological effector function relative to a CTLA4-IgG1 fusion protein. A preferred CTLA4-immunoglobulin fusion protein comprises an extracellular domain of the CTLA4 protein (e.g., amino acid positions 20-144 of the human CTLA4-immunoglobulin fusion protein shown in SEQ ID NO: 24, 26 and 28) linked to an immunoglobulin constant region comprising a hinge region, a CH2 domain and a CH3 domain derived from C.gamma.1, C.gamma.2, C.gamma.3 or C.gamma.4. A preferred constant domain used to reduce the complement activating ability of the fusion protein is C.gamma.4. In one embodiment, the CH2 domain of the immunoglobulin constant region is modified to reduce at least one biological effector function, such as complement activation or Fc receptor interaction. In a particularly preferred embodiment, the CTLA4-immunoglobulin fusion protein includes a CH2 domain which is modified by substitution of an amino acid residue at position 234, 235 and / or 237 of an intact heavy chain protein. One example of such a protein is a CTLA4-immunoglobulin fusion protein fused to IgG4 comprising an amino acid sequence shown in SEQ ID NO: 28 or a CTLA4-immunoglobulin fused to IgG1 fusion protein comprising an amino acid sequence shown in SEQ ID NO: 24.

0013] The CTLA4-immunoglobulin fusion proteins of the invention can be incorporated into pharmaceutical compositions and administered to a subject to inhibit an interaction between a CTLA4 ligand (e.g., B7-1 and / or B7-2) and a receptor therefor (e.g., CD28 and / or CTLA4) on the surface of a T cell, to thereby suppress cell-mediated immune responses in vivo. Inhibition of the CTLA4 ligand / receptor interaction may be useful for both general immunosuppression and to induce antigen-specific T cell tolerance in a subject for use in preventing transplantation rejection (solid organ, skin and bone marrow) or graft versus host disease, particularly in allogeneic bone marrow transplantation. The CTLA4-immunoglobulin fusion proteins can also be used therapeutically in the treatment of autoimmune diseases, allergy and allergic reactions, transplantation rejection and established graft versus host disease in a subject. Moreover, the CTLA4-immunoglobulin fusion proteins of the invention can be used as immunogens to produce anti-CTLA4 antibodies in a subject, to purify CTLA4 ligands and in screening assays to identify molecules which inhibit the interaction of CTLA4 with a CTLA4 ligand.

Problems solved by technology

Fc receptor-mediated phagocytosis or antibody-dependent cellular cytotoxicity, may induce detrimental side effects in the subject and are therefore undesirable.

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