Inflammation is a localized protective response elicited by tissues in response to injury, infection, or tissue destruction resulting in the destruction of the infectious or injurious agent and isolation of the injured tissue. A typical inflammatory response proceeds as follows: recognition of an antigen as foreign or recognition of tissue damage; synthesis and release of soluble inflammatory mediators; recruitment of inflammatory cells to the site of infection or tissue damage; destruction and removal of the invading organism or damaged tissue; and deactivation of the system once the invading organism or damage has been resolved.
Cell-cell interactions are involved in the activation of the immune response at each of the stages described above. One of the earliest detectable events in a normal inflammatory response is adhesion of leukocytes to the vascular endothelium, followed by migration of leukocytes out of the vasculature to the site of infection or injury. The adhesion of these leukocytes, or white blood cells, to vascular endothelium is an obligate step in the migration out of the vasculature. Harlan, J. M., Blood 1985, 65, 513-525.
The adhesion of white blood cells to vascular endothelium and other cell types is mediated by interactions between specific proteins, termed "adhesion molecules," located on the plasma membrane of both white blood cells and vascular endothelium. The interaction between adhesion molecules is similar to classical receptor ligand interactions with the exception that the ligand is fixed to the surface of a cell instead of being soluble. The adherence of white blood cells to vascular endothelium appears to be mediated in part if not in toto by the five cell adhesion molecules: intercellular adhesion molecule-1 (ICAM-1); ICAM-2; endothelial leukocyte adhesion molecule-1 (ELAM-1, also called E-selectin); vascular cell adhesion molecule-1 (VCAM-1); and granule membrane protein-140 (GMP-140). Expression on the cell surface of ICAM-1, ICAM-2, ELAM-1, VCAM-1 and GMP-140 adhesion molecules is induced by inflammatory stimuli. The expression of ELAM-1 and VCAM-1 on endothelial cells is induced by cytokines such as interleukin-1.beta. and tumor necrosis factor, but not gamma-interferon. ICAM-1 expression on endothelial cells is induced by the cytokines, interleukin-1 tumor necrosis factor and gamma-interferon.
In organ transplantation, the reaction of host immune cells with transplant cells is mediated by adhesive cell membrane receptors. An essential step in the activation of T lymphocytes is their interaction with endothelial cells of the graft. Binding of T lymphocytes to the endothelial cells requires intercellular adhesion molecules. It is believed that the induction of ICAM-1 influences the leukocyte response in transplanted tissue. ICAM-1 has been shown to be expressed in rejecting kidney and liver allografts; Faull and Russ, Transplantation 1989, 48, 226-230; Adams et al., Lancet 1989, 1122-1125. Other adhesion molecules, including VCAM-1 and ELAM-1, are also known to be involved in interactions between the transplanted tissue and the immune system.
It is believed that compositions comprising inhibitors of ICAM-1, VCAM-1 and ELAM-1 expression could provide a novel therapeutic class of anti-rejection agents. The use of neutralizing monoclonal antibodies against ICAM-1 in animal models provides evidence that such inhibitors, if identified, would have therapeutic benefit for renal allografts (Cosimi et al., J. Immunol. 1990, 144, 4604-4612) and cardiac allografts (Isobe et al., Science 1992, 255, 1125-1127). Experiments in monkeys have been performed to examine the effectiveness of monoclonal antibodies to ICAM-1 in blocking rejection of kidney allografts. Cosimi et al., J. Immunol. 1990, 144, 4604-4612. As in humans, ICAM-1 molecules are expressed on vascular endothelium in normal kidney. During rejection, ICAM-1 expression increased on endothelial and tubular cells and on leukocytes; this increase correlated with massive infiltration of grafts. Treatment with monoclonal antibody to ICAM-1 decreased cellular infiltration and allowed the necessary cyclosporine A dosage to be reduced. Clinical trials conducted in high-risk kidney allograft patients showed that treatment with mouse anti-ICAM-1 monoclonal antibody in a 14-day postoperative period in addition to the triple drug therapy (cyclosporine A, azathioprine and corticosteroids) improved one-year allograft survival from 56% to 78%. Haug et al., Transplantation 1993, 55, 766-773. However, the majority of patients developed human anti-mouse antibodies within the first two weeks following completion of monoclonal treatment.
Current agents which affect intercellular adhesion molecules include synthetic peptides, monoclonal antibodies, and soluble forms of the adhesion molecules. To date, synthetic peptides which block the interactions with VCAM-1 or ELAM-1 have not been identified. Monoclonal antibodies may prove to be useful for the treatment of allograft rejection due to expression of ICAM-1, VCAM-1 and ELAM-1. The role of ICAM-1 and LFA-1 molecules in graft rejection has been previously demonstrated by treatment of heart allograft recipient mice with monoclonal antibodies to ICAM-1 and LFA-1. This combined treatment induced long-term allograft survival and donor-specific transplantation tolerance. Isobe et al., Science 1992, 255, 1125-1127. However, with chronic treatment, the host animal develops an immune response against the monoclonal antibodies thereby limiting their usefulness in long-term therapy. Soluble forms of the cell adhesion molecules suffer from many of the same limitations as monoclonal antibodies in addition to the expense of their production and their low binding affinity. Thus, there is a long felt need for compositions which effectively inhibit allograft rejection.
PCT/US90/02357 (Hession et al.) discloses DNA sequences encoding Endothelial Adhesion Molecules (ELAMs), including ELAM-1 and VCAM-1 and VCAM-1b. A number of uses for these DNA sequences are provided, including (1) production of monoclonal antibody preparations that are reactive for these molecules which may be used as therapeutic agents to inhibit leukocyte binding to endothelial cells; (2) production of ELAM peptides to bind to the ELAM ligand on leukocytes which, in turn, may bind to ELAM on endothelial cells, inhibiting leukocyte binding to endothelial cells; (3) use of molecules binding to ELAMS (such as anti-ELAM antibodies, or markers such as the ligand or fragments of it) to detect inflammation; and (4) use of ELAM and ELAM ligand DNA sequences to produce nucleic acid molecules which intervene in ELAM or ELAM ligand expression at the translational level using antisense nucleic acid and ribozymes to block translation of a specific mRNA either by masking mRNA with antisense nucleic acid or cleaving it with a ribozyme. It is disclosed that coding regions are the targets of choice. For VCAM-1, AUG is believed to be most likely; a 15-mer hybridizing to the AUG site is specifically disclosed in Example 17 of PCT/US90/02357.
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