Chemistry: molecular biology and microbiology – Vector – per se
Reexamination Certificate
1999-06-03
2002-09-10
Bansal, Geetha P. (Department: 1642)
Chemistry: molecular biology and microbiology
Vector, per se
C435S069700, C435S325000, C435S252300, C435S254200, C536S023100, C536S023400, C536S024100, C536S024200
Reexamination Certificate
active
06448071
ABSTRACT:
TECHNICAL FIELD
This invention is directed to compositions comprising soluble divalent and multivalent heterodimeric analogs of proteins that are involved in immune regulation and methods of making and using the same. The high affinity that these complexes have for their cognate ligands enables them to be effective competitors to T cell receptors and MHC molecules normally involved in transplant rejection and autoimmune disease. Molecules such as divalent T cell receptors may also have an impact on the diagnosis and treatment of cancer in that they may be used to augment antitumor responses, or may be conjugated to toxins which may then be used to help eliminate tumors. Use of such compositions will allow one to accomplish selective immune modulation without compromising the general performance of the immune system.
BACKGROUND OF THE INVENTION
The process of signal transduction often involves proteins that have extracellular domains, transmembrane domains, and intracellular domains. During ligand binding there is often oligomerization of receptor molecules in order to transmit effectively the signal to the intracellular component of the cell. The immune system is an excellent example of a signal transduction pathway that works by these methods (Rosen et al. J. Med. Chem. 38: 48-55).
The immune system is a defense system found in most advanced forms of higher vertebrates. A properly functioning lymphatic and immune system distinguishes between self and nonself. A healthy body protects against foreign invaders, such as bacteria, viruses, fungi, and parasites. As the body encounters foreign material (nonself), also known as an antigens, the immune system becomes activated. An antigen is recognized by characteristic shapes or epitopes on its surface. This defense mechanism provides a means of rapid and highly specific responses that are used to protect an organism against invasion by pathogenic microorganisms. It is the myriad of pathogenic microorganisms that have principally caused the evolution of the immune system to its current form. In addition to protection against infectious agents. specific immune responses are thought to be involved in surveillance against alterations in self antigens as seen in tumor development. Immune responses are also involved in the development of autoimmune disease, AIDS, as well as rejection of transplanted tissues.
Lymphocytes
Within the immune system, lymphocytes play a central role. Lymphocyte responses to foreign organisms orchestrate the effector limbs of the immune system, and ultimately, determine the fate of an infection. Lymphocytes can be divided into two main categories, B and T cells. These two types of lymphocytes are specialized in that they have different effector functions and play different roles in the development of specific immune responses. Individual lymphocytes are specialized in that they are committed to respond to a limited set of structurally related antigens. Specificity is conferred by an unique set of cell surface receptors expressed on individual lymphocytes. These receptors interact with soluble proteins, in the case of B cells, and with antigenic peptide/major histocompatibility complex (MHC) molecules in the case of T lymphocytes. The nature of the interaction with their ligands also differs between B and T cells. The antigen receptors produced by B cells, immunoglobulins (Igs), interact with their ligands with a high affinity. In contrast, T cell receptors interact with their ligands with low affinity. Thus, the T cell response is driven by the interaction of many T cell receptors (TcR) on the surface of an individual T cell interacting with multiple antigenic peptide/MHC complexes on the surface of the antigen presenting cell. Thus, these two diverse groups of cell-surface glycoproteins, the TcRs and the MHC glycoproteins, form key components of specificity in the T lymphocyte response to antigens.
T cells are a major regulatory cell of the immune system. Their regulatory functions depend not only on expression of a unique T cell receptor, but also on expression of a variety of accessory molecules and effector functions associated with an individual T cell response. Effector functions include responses such as cytotoxic responses or other responses characterized by secretion of effector molecules, i.e., lymphokines. It is this regulatory function that often goes awry in the development of autoimmune diseases. The different effector functions also play a large role in tissue graft rejection, and can be important in tumor rejection.
T cells respond to antigens in the context of either Class I or Class II MHC molecules. Cytotoxic T cells respond mainly against foreign antigens in the context of Class I glycoproteins, such as viral-infected cells, tumor antigens and transplantation antigens. In contrast, helper T cells respond mainly against foreign antigens in the context of Class II molecules. Both types of MHC molecules are structurally distinct, but fold into very similar shapes. Each MHC molecule has a deep groove into which a short peptide, or protein fragment, can bind. Because this peptide is not part of the MHC molecule itself. it varies from one MHC molecule to the next. It is the presence of foreign peptides displayed in the MHC groove that engages clonotypic T cell receptors on individual T cells, causing them to respond to foreign antigens.
Antigen-specific recognition by T cells is based on the ability of clonotypic T cell receptor to discriminate between various antigenic-peptides resident in MHC molecules. These receptors have a dual specificity for both antigen and MHC (Zinkemagel et al.
Nature
248: 701-702 (1974)). Thus, T cells are both antigen-specific and MHC-restricted. A simple molecular interpretation of MHC-restricted recognition by T cells is that TcRs recognize MHC residues as well as peptide residues in the MHC-peptide complex. Independent of the exact mechanism of recognition, the clonotypic T cell receptor is the molecule that is both necessary and sufficient to discriminate between the multitude of peptides resident in MHC.
T cells can be divided into two broad subsets; those expressing &agr;/&bgr; TcR and a second set that expresses &ggr;/&dgr; TcR. Cells expressing &agr;/&bgr; TcR have been extensively studied and are known to comprise most of the antigen-specific T cells that can recognize antigenic peptide/MHC complexes encountered in viral infections, autoimmune responses, allograft rejection and tumor-specific immune responses. Cells expressing &agr;/&bgr; TcRs can be further divided into cells that express CD8 accessory molecules and cells that express CD4 accessory molecules. While there is no intrinsic difference between the clonotypic &agr;/&bgr; T cell receptors expressed either on CD4 and CD8 positive cells, the accessory molecules largely correlate with the ability of T cells to respond to different classes of MHC molecules. Class I MHC molecules are recognized by CD8+, or cytotoxic, T cells and class II MHC molecules by CD4+, or helper, T cells.
&ggr;/&dgr; T cells make up another significant population of T cells seen in circulation as well as in specific tissues. These cells are not well understood; their antigen/MHC specificity is poorly defined and in most cases their ligands arc completely unknown. These cells are present in high quantities in certain tissues, including skin and gut epithelium, and are thought to play a significant role in immune responses of those organs. They have also been implicated in autoimmune responses and may be involved in the recognition of heat shock proteins. A general approach to the identification of antigenic complexes, as outlined in the present invention, would greatly facilitate understanding of how these cells influence the development of both normal and abnormal immune responses. There is a large degree of homology between both &agr;/&bgr; and &ggr;/&dgr; TcR expressed in rodents and humans. This extensive homology has, in general, permitted one to develop murine experimental models from which results and implicatio
O'Herrin Sean
Schneck Jonathan
Banner & Witcoff , Ltd.
Bansal Geetha P.
The Johns Hopkins University
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