Use of IL-18 inhibitors for the treatment or prevention of sepsis

FIELD OF THE INVENTION

[0002] The present invention relates to the use of IL-18 inhibitors for treatment and/or prevention of sepsis.

BACKGROUND OF THE INVENTION

[0003] In 1989, a factor induced in the serum from infected mice with mycobacterium bovis and challenged with LPS was detected. This factor was capable of inducing interferon-γ (IFN-γ) in cultures of spleen cells of normal mice in the presence of interleukin-2 (IL-2) (Nakamura et al 1989). This factor functioned not as a direct inducer of IFN-γ but rather as a co-stimulant together with IL-2, anti-CD3 or mitogens. An attempt to further identify this activity from post-endotoxin treated mouse serum revealed an apparently homogeneous 50-55 kDa protein, which was associated with the above activity (Nakamura et al. 1993). Since other cytokines can act as co-stimulants for IFN-γ production, the failure of the neutralizing antibodies to IL-1, IL-4, IL-5, IL-6, or TNF to block the serum activity, suggested that this was a distinct factor. The same authors documented that the endotoxin-induced co-stimulant for IFN-γ production was present in extracts of livers from mice preconditioned with P. acnes (Okamura at al. 1995). According to this experimental model, the hepatic macrophage population (Kupffer cells) expands, and therefore a low dose of bacterial lipopolysaccharide (LPS) becomes lethal. Similar treatment is not lethal for non-pre-conditioned mice. The factor, named IFN-γ-inducing factor (IGIF) and later designated interleukin-18 (IL-18), was purified to homogeneity from these P. acnes-treated mouse livers and a partial amino acid sequence was obtained. Degenerate oligonucleotides derived from the amino acid sequences of purified IL-18 were used to clone a murine IL-18 cDNA (Okamura et al. 1995). The human cDNA sequence for IL-18 was reported in 1996 (Ushio et al. 1996).

[0004] Interleukin IL-18 (Tsutsui et al. 1996, Nakamura et al. 1993, Okamura et. al 1995, Ushio et al. 1996), shares structural features with the IL-1 family of proteins (Bazan et al. 1996), which have an all β-pleated sheet structure unlike most other cytokines, which exhibit a four-helix bundle structure. Similarly to IL-1β, IL-18 is synthesized as a biologically inactive precursor (proIL-18) and lacks a signal peptide (Ushio et al 1996). The IL-1β and IL-18 precursors are cleaved by caspase 1 (IL-1β-converting enzyme, or ICE), which cleaves the precursors after an aspartic acid residue in the P1 position. The resulting mature cytokines are released from the cell (Ghayur et al. 1997 and Gu et al. 1997), despite the lack of signal peptide.

[0005] IL-18 is known to act as a co-stimulant for cytokine production (IFN-γ, IL-2 and granulocyte-macrophage colony stimulating factor) by T helper type I (Th1) cells (Kohnoet al. 1997) and also a co-stimulant for FAS ligand-mediated cytotoxicity by murine natural killer cell clones (Tsutsui et al. 1996).

[0006] Interleukin-12 (IL-12) is an immunoregulatory cytokine produced by monocyte/macrophages and other antigen presenting cells. It is central to the orchestration of both innate and acquired cell-mediated immunoresponses (Trinchieri 1998). It consists of a heterodimer composed of the covalently linked products of two separate genes: a heavy chain (p40) and a light chain (p35). Production of IL-12 is stimulated in response to certain bacteria, bacterial products, intracellular parasites and viruses. The following functions have been attributed to IL-12: 1) it is a potent inducer of IFN-γ from T and natural killer (NK) cells, 2) it is co-mitogenic for such cells, 3) it is critical for development of Th1 responses in most systems (thus leading secondarily, to increases in IFN-γ and TNF production, macrophage activation etc.), 4) it enhances cytotoxic T lymphocytes and NK cell cytotoxicity and 5) it is required for delayed-type hypersensitivity responses. IL-12 production in isolated murine splenic leukocytes treated with Staphylococcus aureus Cowan 1 strain, was shown to be suppressed by IFN-α or IFN-β (Karp et al. 2000).

[0007] Recently IL-12 has been reported to be involved in pathogenesis of organ-specific autoimmune inflammatory diseases such as multiple sclerosis (MS) (Karp et al. 2000) and inflammatory bowel disease (IBD) (Blumberg and Strober 2001 and Fiocchi 1999) and it is thus being regarded as a potential drug target for the treatment of these conditions.

[0008] IL-18 and IL-12 exhibit a marked synergism in induction of IFN-γ in T cells (Okamura et al. 1998). Investigations into the mechanism of this synergism have revealed that IL-12 up-regulates expression of both chains of the IL-18 receptor on cells producing IFN-γ (Kim et al. 2001). Although IL-12 and IL-18 activate both innate and acquired immunity, their excessive production by activated macrophages may induce multiple organ disorders including malfunction of the immune system (Seki et al. 2000).

[0009] Cytokine binding proteins (soluble cytokine receptors) are usually the extracellular ligand binding domains of their respective cell surface cytokine receptors. They are produced either by alternative splicing or by proteolytic cleavage of the cell surface receptor. These soluble receptors have been described in the past: for example, the soluble receptors for IL-6 and IFN-γ (Novick et al. 1989), TNF (Engelmann et al. 1989 and Engelmann et al. 1990), IL-1 and IL-4 (Maliszewski et al. 1990) and IFN-α/β (Novick et al. 1994, Novick et al. 1992). One cytokine-binding protein, named osteoprotegerin (OPG, also known as osteoclast inhibitory factor—OCIF), a member of the TNFR/Fas family, appears to be the first example of a soluble receptor that exists only as a secreted protein (Anderson et al. 1997, Simonet et al. 997, Yasuda et al. 1998).

[0010] An interleukin-18 binding protein (IL-18BP) was affinity purified, on an IL-18 column, from urine (Novick et al. 1999). IL-18BP abolishes IL-18 induction of IFN-γ, and IL-18 activation of NF-kB in vitro. In addition, IL-18-BP inhibits induction of IFN-γ in mice injected with LPS. The IL-18BP gene was localized to the human chromosome 11, and no exon coding for a transmembrane domain could be found in the 8.3 kb genomic sequence comprising the IL-18BP gene. Four isoforms of IL-18BP generated by alternative mRNA splicing have been found in humans so far. They were designated IL-18BP a, b, c, and d, all sharing the same N-terminus and differing in the C-terminus (Novick et al 1999). These isoforms vary in their ability to bind IL-18 (Kim et al. 2000). Of the four, human IL-18BP (hIL-18BP) isoforms a and c are known to have a neutralizing capacity for IL-18. The most abundant IL-18BP isoform, the spliced variant isoform a, exhibits a high affinity for IL-18 with a rapid on-rate and a slow off-rate, and a dissociation constant (Kd) of approximately 0.4 nM (Kim et al. 2000). IL-18BP is constitutively expressed in the spleen, and belongs to the immunoglobulin superfamily. The residues involved in the interaction of IL-18 with IL-18BP have been described through the use of computer modelling (Kim et al. 2000) and based on the interaction between the similar protein IL-1β with the IL-1R type I (Vigers et al. 1997). According to the model of IL-18 binding to the IL-18BP, the Glu residue at position 42 and Lys residue at position 89 of IL-18 have been proposed to bind to Lys-130 and Glu-114 in IL-18BP, respectively (Kim et al. 2000).

[0011] IL-18BP is constitutively present in many cells (Puren et al. 1999) and circulates in healthy humans (Urushihara et al. 2000), representing a unique phenomenon in cytokine biology. Due to the high affinity of IL-IBP to IL-18 (Kd=0.4 nM) as well as the high concentration of IL-18BP found in the circulation (20 fold molar excess over IL-18), it has been speculated that most, if not all of the IL-18 molecules in the circulation are bound to IL-18BP. Thus, the circulating IL-18BP that competes with cell surface receptors for IL-18 may act as a natural anti-inflammatory and an immunosuppressive molecule.

[0012] As mentioned, IL-18 induces IFN-γ which, in turn, was recently reported to induce IL-18BPa mRNA generation in vitro (Muhl et al 2000). Therefore, IL-18BPa could serve as a “shut off” signal, terminating the inflammatory response.

[0013] IL-18BP is significantly homologous to a family of proteins encoded by several Pox viruses (Novick et al. 1999, Xiang and Moss 1999). Inhibition of IL-18 by this putative viral IL-18BP may attenuate the inflammatory antiviral Th1 response.

[0014] The term systemic inflammatory response syndrome (SIRS) describes the familiar clinical syndrome of sepsis, independent of its cause. SIRS can result from trauma, pancreatitis, drug reactions, autoimmune disease, and other disorders; when it arises in response to infection, sepsis is said to be present (Nathens and Marshall 1996).

[0015] Septic shock is the most common cause of death in medical and surgical intensive—care units (Astiz and Rackow 1998). The terms sepsis, severe sepsis and septic shock are used to identify the continuum of the clinical response to infection. Patients with sepsis present evidences of infection and clinical manifestations of inflammation. Patients with severe sepsis develop hypoperfusion whith organ dysfunction. Septic shock is manifested by hypoperfusion and persistent hypotension. Mortality ranges from 16% in patients with sepsis to 40-60% in patients with septic shock. Bacterial infection is the most common cause of septic shock. The most frequent sites of infection are the lungs, abdomen, and urinary tract. General anti-inflammatory therapies such as the use of corticosteroids, failed to show improvement in survival from sepsis and septic shock. Three monoclonal antibodies specific to endotoxin have been tested in clinical trials and have failed to improve survival rates. Therapy with antagonists to tumor necrosis factor, interleukin 1, bradykinin, ibuprofen, and platelet activating-factor, did not show improvement on survival from septic shock (Astiz and Rackow 1998).

[0016] Sepsis is caused inter alia by Gram-positive bacteria e.g., Staphylococcus epidermidis. Lipoteichoic acids and peptidoglycans, which are the main cell wall components of the Staphylococcus species, are thought to be the inducers of cytokine release in this condition (Grupta et al. 1996 and Cleveland et al. 1996). However, other Gram-positive components are considered as stimulators of cytokine synthesis as well (Henderson et al. 1996). Production of IL-1, TNF-α and IFN-γ are thought to be the major contributors in the pathogenesis of septic shock (Dinarello 1996 and Okusawa et al. 1988). In addition, the chemokine IL-8 was shown to be induced by neutrophils in response to S. epidermidis (Hachicha et al. 1998). Important factors in the regulation of IL-1, TNF-α and IFN-γ induction by S epidermidis are IL-18, IL-12, IL-1 β and TNF-α. IL-1β and TNF-α can be considered as a co-stimuli for IFN-γ production by T lymphocytes in a manner similar to IL-18. These two cytokines have a co-stimulatory activity on IFN-γ production in the context of IL-12 or bacterial stimulation (Skeen et al. 1995 and Tripp at al. 1993).

[0017] Recently it was reported by Nakamura et al. (2000) that concomitant administration of IL-18 and IL-12 to mice results in high toxicity similar to that found in endotoxin-induced septic shock.

[0018] The levels of IL-18 have been shown to be elevated in sera from patients with sepsis (Endo et al. 2000) but this increase correlated with creatinine levels suggesting that the elevated levels of IL-18 may result from renal failure. In another study (Grobmyer et al. 2000), the levels of IL-18 in 9 subjects with sepsis during the first 96 hours following hospital admission were high and did not correlate with creatinine levels.

[0019] As is apparent from the above, IL-18 is a pleiotropic interleukin having both inflammatory enhancing and attenuating functions. On the one hand, it enhances production of proinflammatory cytokines like TNF-α, therefore promoting inflammation. On the other hand, it induces the production of nitric oxide (NO), an inhibitor of caspase-1, thus blocking the maturation of IL-1β, and possibly attenuating inflammation. This dual role of IL-18, seriously questions the efficacy of IL-18 inhibitors in the treatment of inflammatory diseases. Furthermore, because of the involvement of a large variety of different cytokines and chemokines in the regulation of inflammation, it cannot always be expected to obtain a beneficial effect by blocking only one of the pathways in such a complicated interaction network.

[0020] Netea et al. (2000) reported that administration of anti-IL-18 polyclonal antibody protected mice against the deleterious effects of both LPS derived from E. coli or S. typhimurium species tested, supporting the concept that IL-18 has an important pathogenic role in lethal endotoxemia. However, the uncertainty regarding the efficiency of a potential treatment formulation based on administration of IL-18 inhibitors, is manifested in that IL-18 knock out mice are not less susceptible to sepsis as compared to wild type animals (Sakao et al. 1999) and in that recent reports suggest that the proinflammatory activity of IL-18 is essential to host defences against severe infections (Nakanishi et al. 2001 and Foss et al. 2001).

[0021] Thus, there exists a need to provide means to treat and/or prevent sepsis despite the above-mentioned considerations regarding the use of IL-18 inhibitors.

SUMMARY OF THE INVENTION

[0022] The invention relates to the use of an inhibitor of IL-18 in the manufacture of a medicament for the treatment and/or prevention of sepsis and other diseases characteristic to the Systemic Inflammatory Response Syndrome (SIRS) selected from severe sepsis and septic shock, and also for sepsis related cardiac dysfunction.

[0023] More specifically the invention relates to the use of an inhibitor of IL-18, selected from caspase-1 (ICE) inhibitors, antibodies against IL-18, antibodies against any of the IL-18 receptor subunits, inhibitors of the IL-18 signaling pathway, antagonists of IL-18 which compete with IL-18 and block the IL-18 receptor, inhibitors of IL-18 production and IL-18 binding proteins, isoforms, muteins, fused proteins, functional derivatives, active fractions or circularly permutated derivatives thereof having at least essentially the same activity as an IL-18 binding protein.

[0024] The IL-18 binding protein used according to the invention is an isoform, a mutein, fused protein (e.g., Ig fused), functional derivative (e.g., PEG-conjugated), active fraction or circularly permutated derivative thereof.

[0025] The antibodies used according to the invention may be anti IL-18 specific antibodies selected from chimeric, humanized and human antibodies.

[0026] In addition, the invention relates to the use of an inhibitor in the manufacture of a medicament further comprising an IL-12 inhibitor, preferably an IL-12 neutralizing antibody, an interferon, preferably interferon α or β, a tumor necrosis factor inhibitor, preferably soluble TNFRI or TNFRII, and/or an IL-1 inhibitor, preferably IL-1 receptor antagonist for simultaneous, sequential or separate administration.

[0027] In one aspect, the invention provides the use of an expression vector comprising the coding sequence of an inhibitor of IL-18 selected from caspase-1 (ICE) inhibitors, antibodies against IL-18, antibodies against any of the IL-18 receptor subunits, inhibitors of the IL-18 signaling pathway, antagonists of IL-18 which compete with IL-18 and block the IL-18 receptor, inhibitors of IL-18 production and IL-18 binding proteins, isoforms, muteins, fused proteins, or circularly permutated derivatives thereof having at least essentially the same activity as an IL-18 binding protein, in the manufacture of a medicament for the treatment and/or prevention of sepsis, for example by gene therapy.

[0028] In another aspect, the invention provides the use of a vector for inducing and/or enhancing the endogenous production of an inhibitor of IL-18 in a cell, in the manufacture of a medicament for the treatment and/or prevention of sepsis.

[0029] In addition, the invention provides the use of a cell that has been genetically modified to produce an inhibitor of IL-18 in the manufacture of a medicament for the treatment and/or prevention of sepsis.

[0030] In another embodiment, the invention relates to a method for the treatment and/or prevention of sepsis and other diseases characteristic to the Systemic Inflammatory Response Syndrome (SIRS), including sepsis related cardiac dysfunction, comprising administrating to a subject in need thereof a pharmaceutically effective amount of inhibitor of IL-18 selected from caspase-1 (ICE) inhibitors, antibodies against IL-18, antibodies against any of the IL-18 receptor subunits, inhibitors of the IL-18 signaling pathway, antagonists of IL-18 which compete with IL-18 and block the IL-18 receptor, inhibitors of IL-18 production, and IL-18 binding proteins, isoforms, muteins, fused proteins, functional derivatives, active fractions or circularly permutated derivatives thereof having essentially the same activity as an IL-18 binding protein. The method may comprise co-administration of a therapeutically effective amount an inhibitor of cytokines selected from IL-12 inhibitor, preferably neutralizing antibodies, Tumor Necrosis Factor inhibitors, preferably soluble portion of TNFRI or TNFRII), IL-1 inhibitors. preferably the IL-1 receptor antagonists and IL-8 inhibitors, and/or an interferon , preferably interferon-α or-β.

[0031] In addition, the invention provides a method for the treatment and/or prevention of sepsis and other diseases characteristic to the Systemic Inflammatory Response Syndrome (SIRS) comprising administrating to a subject in need thereof a pharmaceutically effective amount of vector coding the sequence of an inhibitor of IL-18 selected from caspase-1 (ICE) inhibitors, antibodies against IL-18, antibodies against any of the IL-18 receptor subunits, inhibitors of the IL-18 signaling pathway, antagonists of IL-18 which compete with IL-18 and block the IL-18 receptor, inhibitors of IL-18 production, and IL-18 binding proteins, isoforms, muteins, fused proteins or circularly permutated derivatives thereof.

[0032] In a further embodiment, the invention relates to a method for the treatment and/or prevention of sepsis and other diseases characteristic to the SIRS comprising administrating to a subject in need thereof a pharmaceutically effective amount of a vector for inducing and/or enhancing the endogenous production of an inhibitor of il-18 in a cell.

[0033] In addition, the invention provides a method for the treatment and/or prevention of sepsis and other diseases characteristic to the SIRS comprising administration to a subject in need thereof a cell that has been genetically modified to produce an inhibitor of il-18.

BRIEF DESCRIPTION OF THE FIGURES

[0034]
FIG. 1 shows the distribution of serum IL-18BPa in healthy individuals. Sera of male and female healthy individuals ages 20-60, as assayed for the presence of IL-18BPa by a specific ELISA test (n=107).

[0035]
FIG. 2 A shows the average levels of IL-18 and IL-18BPa in sepsis patients and healthy subjects. Serum IL-18 and IL-18BPa were determined in the healthy individuals (see FIG. 1) and in 198 samples from 42 sepsis patients immediately upon hospital admission and during hospitalisation.

[0036]
FIG. 2 B shows the distribution of the individual levels of IL-18 and IL-18BPa of the healthy subjects and patients described in FIG. 2A. The mean serum levels of IL-18 and IL-18BPa in healthy subjects are indicated by a dashed vertical and horizontal line, respectively.

[0037]
FIG. 3 shows a comparison between the total and free IL-18 in individual sepsis patients upon hospital admission. The level of free IL-18 (closed circles) in sera was calculated based on the concentration of total IL-18 (open circles) and IL-18BPa, taking into account a stoichiometry of 1:1 of IL-18 to IL-18BPa in a complex and a calculated Kd of 400 pM. Each vertical line links total and free IL-18 in an individual serum sample.

[0038]
FIG. 4 shows the effect of IL-18BP on S. epidermidis-induced IFN-γ production in whole blood. Whole blood was stimulated with S. epidermidis alone or S. epidermidis and recombinant IL-18BP at indicated concentrations. After 48 hours of incubation, the blood culture was lysed and IFN-γ was measured. The results are expressed as percentage of S. epidermidis IFN-γ induction. P<0.01 vs. S. epidermidis alone. The data represents the means±standard error of the mean (SEM) of six experiments. SEM represents the spread of the mean of a sample. SEM gives an idea of the accuracy of the mean. SEM=SD/(square root of sample size). The data was analysed with paired Student's test.

[0039]
FIG. 5 shows the inhibitory effect exerted by the double activity of IL-18BPa and anti IL-12 monoclonal antibodies on the production of IFN-γ by whole blood treated with S. epidermidis. Whole blood was stimulated with S. epidermidis in the presence or in the absence or of IL-18BPa (125 ng/ml), IL-12 Mab (2.5 μg/ml) and both. After 48 hours of incubation, the blood culture was lysed and IFN-γ was measured. The data is expressed as percent of IFN-γ induction. P<0.01 vs. S. epidermidis alone. The data represents the mean±standard error of the mean (SEM) of six experiments. SEM represents the spread of the mean of a sample. SEM gives an idea of the accuracy of the mean. SEM=SD/(square root of sample size). The data was analysed with paired Student's test.

[0040]
FIG. 6 shows the quantitation of IL-18BPa as reflected in an ELISA standard curve. Recombinant human IL-18BPa was serially diluted and subjected to ELISA as described in Example 3. The data shows the mean absorbance±SE (standard error) of 10 experiments.

[0041]
FIG. 7 shows the inhibitory effect of IL-18 on the quantitation of IL-18BPa by ELISA assay. The percent of inhibition of the signal is shown.

[0042]
FIG. 8 shows the immunological cross reactivity of human IL-18BP isoforms. The IL-18P ELISA was performed with all isoforms (a-d) of IL-18BP. Stocks (3.2 μg/ml) of the IL-18BP isoforms were serially diluted and tested in IL-18BPa ELISA.

[0043]
FIG. 9 shows myocardial tissue content of IL-18 following LPS administration. Mice were injected with E. coli LPS (0.5 mg/Kg, intraperitonially). Hearts were homogenized at the indicated times at the x axis. ELISA was carried out to determine myocardial IL-18 content. (n=4-5 per group).

[0044]
FIG. 10 shows the effect of anti IL-18 antibody on LPS-induced myocardial dysfunction. Mice were injected with either vehicle (intraperitoneally injected saline n=8) or E. coli LPS (0.5 mg/Kg injected intraperitoneally, n=8) and the left ventricular developed pressure (LVDP) was determined at 6 hours by isolated heart perfusion. In separate experiments, mice were pretreated with either normal rabbit serum (NRS, n=5) or anti-IL-18 antibody (Anti IL-18, n=8) 30 minutes prior to LPS.

DETAILED DESCRIPTION OF THE INVENTION

[0045] The present invention relates to the administration of IL-18 inhibitors to prevent or treat sepsis and is based on the findings described in the examples. It was found in according with the present invention that the levels of effective (free) circulating IL-18 are significantly elevated in serum of sepsis patients in comparison to healthy individuals, and that the inhibition of IL-18 causes a decrease in IFN-γ induction by the Gram-positive bacterium Staphylococcus epidermidis.

[0046] In addition the prevention/treatment of sepsis can be approached by administration of an IL-18 inhibitor in combination of other cytokine inhibitors potentially able to increase its effect.

[0047] Sepsis according to the present invention, comprises SIRS, severe sepsis, septic shock, endotoxic shock etc., and may be caused by Gram-positive or Gram-negative bacteria.

[0048] The term “inhibition of IL-18” within the context of this invention refers to any molecule modulating IL-18 production and/or action in such a way that IL-18 production and/or action is attenuated, reduced, or partially, substantially or completely prevented or blocked.

[0049] An inhibitor of production can be any molecule negatively affecting the synthesis, processing or maturation of IL-18, e.g ICE inhibitor. The inhibitors, considered according to the invention can be, for example, suppressors of gene expression of the interleukin IL-18, antisense mRNAs reducing or preventing the transcription of the IL-18 mRNA or ribozymes leading to degradation of the mRNA, proteins impairing correct folding, or partially or substantially preventing secretion of IL-18, proteases degrading IL-18 and the like.

[0050] Inhibitors of IL-18 action can be IL-18 antagonist for example IL-18BP. Antagonists can either bind to or sequester the IL-18 molecule itself with sufficient affinity and specificity to partially or substantially neutralize the IL-18 or IL-18 active site(s) responsible for IL-18 binding to its ligands (e.g., to its receptors). An antagonist may also inhibit the IL-18 signaling pathway, which is activated within the cells upon IL-18/receptor binding.

[0051] Inhibitors of IL-18 action may be also soluble IL-18 receptors or molecules mimicking the receptors, or agents blocking the IL-18 receptors or molecules mimicking the receptors, or agents blocking the IL-18 receptors, IL-18 antibodies, such as monoclonal antibodies, or any other agent or molecule preventing the binding of IL-18 to its targets, thus diminishing or preventing triggering of intra- or extracellular reactions mediated by IL-18.

[0052] The term “IL-18 binding proteins” is used herein synonymously with “IL18-BP”. It comprises IL-18 binding proteins as defined in WO 99/09063 or in Novick et al., 1999, including splice variants and/or isoforms of IL-18 binding proteins, as defined in Kim et al., 2000. In particular, human isoforms a and c of IL-18BP are useful in accordance with the presence invention. The proteins useful according to the present invention may be glycosylated or non-glycosylated, they may be derived from natural sources, such as urine, or they may preferably be produced recombinantly. Recombinant expression may be carried out in prokaryotic expression systems like E. coli, or in eukaryotic, and preferably in mammalian, expression systems.

[0053] As used herein the term “muteins” refers to analogs of an IL-18BP, or analogs of a viral IL-18BP, in which one or more of the amino acid residues of a natural IL-18BP or viral IL-18BP are replaced by different amino acid residues, or are deleted, or one or more amino acid residues are added to the natural sequence of an IL-18BP, or a viral IL-18BP, without changing considerably the activity of the resulting products as compared with the wild type IL-18BP or viral IL-18BP. These muteins are prepared by known synthesis and/or by site-directed mutagenesis techniques, or any other known technique suitable therefor.

[0054] Any such mutein preferably has a sequence of amino acids sufficiently duplicative of that of an IL-18BP, or sufficiently duplicative of a viral IL-18BP, such as to have substantially similar activity to IL-18BP. One activity of IL-18BP is its capability of binding IL-18. As long as the mutein has substantial binding activity to IL-18, it can be used in the purification of IL-18, such as by means of affinity chromatography, and thus can be considered to have substantially similar activity to IL-18BP. Thus, it can be determined whether any given mutein has substantially the same activity as IL-18BP by means of routine experimentation comprising subjecting such a mutein, e.g., to a simple sandwich competition assay to determine whether or not it binds to an appropriately labeled IL-18, such as radioimmunoassay or ELISA assay.

[0055] Muteins of IL-18BP polypeptides or muteins of viral IL-18BPs, which can be used in accordance with the present invention, or nucleic acid coding therefore, include a finite set of substantially corresponding sequences as substitution peptides or polynucleotides which can be routinely obtained by one of ordinary skill in the art, without undue experimentation, based on the teachings and guidance presented herein.

[0056] Preferred changes for muteins in accordance with the present invention are what are known as “conservative” substitutions. Conservative amino acid substitutions of IL-18BP polypeptides or proteins or viral IL-18BPs, may include synonymous amino acids within a group which have sufficiently similar physicochemical properties that substitution between members of the group will preserve the biological function of the molecule (Grantham, 1974).

[0057] It is clear that insertions and deletions of amino acids may also be made in the above-defined sequences without altering their function, particularly if the insertions or deletions only involve a few amino acids, e.g., under thirty, and preferably under ten, and do not remove or displace amino acids which are critical to a functional conformation, e.g., cysteine residues. Proteins and muteins produced by such deletions and/or insertions come within the purview of the present invention.

[0058] Preferably, the synonymous amino acid groups are those defined in Table I. More preferably, the synonymous amino acid groups are those defined in Table II; and most preferably the synonymous amino acid groups are those defined in Table III.

1TABLE IPreferred Groups of Synonymous Amino AcidsAmino AcidSynonymous GroupSerSer, Thr, Gly, AsnArgArg, Gln, Lys, Glu, HisLeuIle, Phe, Tyr, Met, Val, LeuProGly, Ala, Thr, ProThrPro, Ser, Ala, Gly, His, Gln, ThrAlaGly, Thr, Pro, AlaValMet, Tyr, Phe, Ile, Leu, ValGlyAla, Thr, Pro, Ser, GlyIleMet, Tyr, Phe, Val, Leu, IlePheTrp, Met, Tyr, Ile, Val, Leu, PheTyrTrp, Met, Phe, Ile, Val, Leu, TyrCysSer, Thr, CysHisGlu, Lys, Gln, Thr, Arg, HisGlnGlu, Lys, Asn, His, Thr, Arg, GlnAsnGln, Asp, Ser, AsnLysGlu, Gln, His, Arg, LysAspGlu, Asn, AspGluAsp, Lys, Asn, Gln, His, Arg, GluMetPhe, Ile, Val, Leu, MetTrpTrp

[0059]

2

TABLE II

More Preferred Groups of Synonymous Amino Acids

Amino Acid
Synonymous Group

Ser
Ser

Arg
His, Lys, Arg

Leu
Leu, Ile, Phe, Met

Pro
Ala, Pro

Thr
Thr

Ala
Pro, Ala

Val
Val, Met, Ile

Gly
Gly

Ile
Ile, Met, Phe, Val, Leu

Phe
Met, Tyr, Ile, Leu, Phe

Tyr
Phe, Tyr

Cys
Cys, Ser

His
His, Gln, Arg

Gln
Glu, Gln, His

Asn
Asp, Asn

Lys
Lys, Arg

Asp
Asp, Asn

Glu
Glu, Gln

Met
Met, Phe, Ile, Val, Leu

Trp
Trp

[0060]

3

TABLE III

Most Preferred Groups of Synonymous Amino Acids

Amino Acid
Synonymous Group

Ser
Ser

Arg
Arg

Leu
Leu, Ile, Met

Pro
Pro

Thr
Thr

Ala
Ala

Val
Val

Gly
Gly

Ile
Ile, Met, Leu

Phe
Phe

Tyr
Tyr

Cys
Cys, Ser

His
His

Gln
Gln

Asn
Asn

Lys
Lys

Asp
Asp

Glu
Glu

Met
Met, Ile, Leu

Trp
Met

[0061] Examples of production of amino acid substitutions in proteins which can be used for obtaining muteins of IL-18BP polypeptides or proteins, or muteins of viral IL-18BPs, for use in the present invention include any known method steps, such as presented in U.S. Pat. Nos. RE 33,653, 4,959,314, 4,588,585 and 4,737,462, to Mark et al; 5,116,943 to Koths et al., 4,965,195 to Namen et al; 4,879,111 to Chong et al; and 5,017,691 to Lee et al; and lysine substituted proteins presented in U.S. Pat. No. 4,904,584 (Shaw et al).

[0062] The term “fused protein” refers to a polypeptide comprising an IL-18BP, or a viral IL-18BP, or a mutein or fragment thereof, fused with another protein, which, e.g., has an extended residence time in body fluids. An IL-18BP or a viral IL-18BP may thus be fused to another protein, polypeptide or the like, e.g., an immunoglobulin or a fragment thereof.

[0063] “Functional derivatives” as used herein cover derivatives of IL-18BPs or a viral IL-18BP, and their muteins and fused proteins, which may be prepared from the functional groups which occur as side chains on the residues or the N- or C-terminal groups, by means known in the art, and are included in the invention as long as they remain pharmaceutically acceptable, i.e., they do not destroy the activity of the protein which is substantially similar to the activity of IL-18BP, or viral IL-18BPs, and do not confer toxic properties on compositions containing it.

[0064] These derivatives may, for example, include polyethylene glycol side-chains (PEG-conjugated), which may mask antigenic sites and extend the residence of an IL-18BP or a viral IL-18BP in body fluids. Other derivatives include aliphatic esters of the carboxyl groups, amides of the carboxyl groups by reaction with ammonia or with primary or secondary amines, N-acyl derivatives of free amino groups of the amino acid residues formed with acyl moieties (e.g., alkanoyl or carbocyclic aroyl groups) or O-acyl derivatives of free hydroxyl groups (for example that of seryl or threonyl residues) formed with acyl moieties.

[0065] As “active fractions” of an IL-18BP, or a viral IL-18BP, muteins and fused proteins, the present invention covers any fragment or precursors of the polypeptide chain of the protein molecule alone or together with associated molecules or residues linked thereto, e.g., sugar or phosphate residues, or aggregates of the protein molecule or the sugar residues by themselves, provided said fraction has substantially similar activity to IL-18BP.

[0066] Functional derivatives of IL-18BP may be conjugated to polymers in order to improve the properties of the protein, such as the stability, half-life, bioavailability, tolerance by the human body, or immunogenicity. To achieve this goal, IL18-BP may be linked e.g., to Polyethlyenglycol (PEG). PEG-conjugated may be carried out by known methods, described in WO 92/13095, for example.

[0067] Therefore, in a preferred embodiment of the present invention. IL-18BP is PEG-conjugated.

[0068] In a further preferred embodiment of the invention the inhibitor of IL-18 is a fused protein comprising all or part of an IL-18 binding protein, which is fused to all or part of an immunoglobulin. The person skilled in the art will understand that the resulting fusion protein retains the biological activity of IL-18BP, in particular the binding to IL-18. The fusion may be direct, or via a short linker peptide which can be as short as 1 to 3 amino acid residues in length or longer, for example, 13 amino acid residues in length. Said linker may be a tripeptide of the sequence E-F-M (Glu-Phe-Met), for example, or a 13-amino acid linker sequence comprising Glu-Phe-Gly-Ala-Gly-Leu-Val-Leu-Gly-Gly-Gln-Phe-Met introduced between the IL-18BP sequence and the immunoglobulin sequence. The resulting fusion protein has improved properties, such as an extended residence time in body fluids (half-life), increased specific activity, increased expression level, or the purification of the fusion protein is facilitated.

[0069] IL-18BP may be fused to the constant region of an Ig molecule. Preferably, it is fused to heavy chain regions, like the CH2 and CH3 domains of human IgG1, for example. The generation of specific fusion proteins comprising IL-18BP and a portion of an immunoglobulin are described in Example 11 of WP99/09063, for example. Other isoforms of Ig molecules are also suitable for the generation of fusion proteins according to the present invention, such as isoforms IgG2 or IgG4, or other Ig classes, like IgM or IgA, for example. Fusion proteins may be monomeric or multimeric, hetero- or homomultimeric.

[0070] The inhibitor of IL-18 can be an antagonist for example a molecule that binds the IL-18 receptor but is not able to trigger the signaling pathway activated upon binding of the cytokine to said receptor (e.g., IL1-Ra Dinarello 1996). All groups of antagonists are useful, either alone or together, in combination with an IL-18 inhibitor, in the therapy of sepsis.

[0071] The inhibitor of IL-18 can be an anti-IL-18 specific antibody. Anti-IL-18 antibodies may be polyclonal or monoclonal, chimeric, humanized, or even fully human. Recombinant antibodies and fragments thereof are characterized by high affinity binding to IL-18 in vivo and low toxicity. The antibodies which can be used in the invention are characterized by their ability to treat patients for a period sufficient to have good to excellent regression or alleviation of the pathogenic condition or any symptom or group of symptoms related to a pathogenic condition, and a low toxicity.

[0072] IL-18 has been shown to increase in the course of cardiac dysfunction caused by sepsis. Co-administration of LPS together with an IL-18 inhibitor, such as a neutralizing anti-IL-18 polyclonal antibody, protects from LPS-induced myocardial dysfunction.

[0073] Neutralizing antibodies are readily raised in animals such as rabbits, goat or mice by immunization with IL-18. Immunized mice are particularly useful for providing sources of B cells for the manufacture of hybridomas, which in turn are cultured to produce large quantities of anti-IL-18 monoclonal antibodies.

[0074] Chimeric antibodies are immunoglobulin molecules characterized by two or more segments or portions derived from different animal species. Generally, the variable region of the chimeric antibody is derived from a non-human mammalian antibody, such as murine monoclonal antibody, and the immunoglobulin constant region is derived from a human immunoglobulin molecule. Preferably, both regions and the combination have low immunogenicity as routinely determined (Elliott et al., 1994) Humanized antibodies are immunoglobulin molecules created by genetic engineering techniques in which the murine constant regions are replaced with human counterparts while retaining the murine antigen binding regions. The resulting mouse-human chimeric antibody preferably have reduced immunogenicity and improved pharmacokinetics in humans (Knight et al., 1993).

[0075] Thus, in a further preferred embodiment, IL-18 antibody is a humanized IL-18 antibody. Preferred examples of humanized anti-IL-18 antibodies are described in the European Patent Application EP 0 974 600, for example.

[0076] In yet a further preferred embodiment, the IL-18 antibody is fully human. The technology for producing human antibodies is described in detail e.g., in WO00/76310, WO99/53049, U.S. Pat. No. 6,162,963 or AU5336100. Fully human antibodies are preferably recombinant antibodies, produced in transgenic animals, e.g., xenomice, comprising all or parts of functional human Ig loci.

[0077] The polypeptide inhibitors can be produced in prokaryotic or eukaryotic recombinant systems or can be encoded in vectors designed for gene targeting.

[0078] Other cytokine inhibitors can be used together with inhibitors of IL-18 in the treatment of sepsis. An inhibitor of IL-18 may be used in combination with an IL-12 Inhibitor.

[0079] The term “inhibition of IL-12” within the context of this invention refers to any molecule modulating IL-12 production and/or action in such a way that IL-12 production and/or action is attenuated, reduced, or partially, substantially or completely prevented or blocked.

[0080] An inhibitor of IL-12 production can be any molecule negatively affecting its synthesis e.g interferon α/β (Karp et al. 2000), or molecules negatively affecting processing or maturation of IL-12. The inhibitors, considered according to the invention can be, for example, suppressors of gene expression of the interleukin IL-12, antisense mRNAs reducing or preventing the transcription of the IL-12 mRNA or ribozymes leading to degradation of the IL-12 mRNA, proteins impairing correct folding, or partially or substantially preventing secretion of IL-12, proteases degrading IL-12 and the like.

[0081] IL-12 antagonists exert their activity in several ways. Antagonists can bind to or sequester the IL-12 molecule itself with sufficient affinity and specificity to partially or substantially neutralize the IL-12 epitope or epitopes responsible for IL-12 receptor binding (hereinafter termed “sequestering antagonists”). A sequestering antagonist may be, for example, an antibody directed against IL-12, a truncated form of IL-12 receptor, comprising the extracellular domains of the receptor or functional portions thereof etc. An antagonist may also inhibit the IL-12 signaling pathway, which is activated within the cells upon IL-12/receptor binding (hereinafter termed “signalling antagonists”). All groups of antagonists are useful, either alone or together, in combination with an IL-18 inhibitor, in the therapy of sepsis. IL-12 antagonists are easily identified and evaluated by routine screening of candidates for their effect on the activity of native IL-12 on susceptible cell lines in vitro. For example mouse splenocytes in which phorbol ester and IL-12 causes proliferation. The assay contains IL-12 formulation at varying dilutions of candidate antagonist, e.g., from 0.1 to 100 times the molar amount of IL-12 used in the assay, and controls with no IL-12, antagonist only or phorbol ester and IL-2 (Tucci et al., 1992).

[0082] Sequestering antagonists are the preferred IL-12 antagonists to be used according to the present invention. Amongst sequestering antagonists, antibodies that neutralize Il-12 activity are preferred. The simultaneous, sequential, or separate use of the IL-18 inhibitor with the IL-12 antagonist is preferred, according to the invention. Anti IL-12 is the preferred IL-12 antagonist to be used in combination with an IL-18 inhibitor as well as antibody derivatives, fragments, regions and biologically active portions of the antibody. The IL-18 inhibitor can be used simultaneously, sequentially or separately with the IL-12 inhibitor.

[0083] In addition, an inhibitor of IL-18 may be used in combination with inhibitors of other cytokines, known to play an important role in septic shock e.g.. IL-1. TNF, IL-8 etc Dinarello 1996 and Okusawa et al. 1988. An example for an inhibitor of IL-1 is IL1-receptor antagonist, and for TNF the soluble portion of receptors TNFR1 and TNFR2.

[0084] The term “inhibition of cytokines” within the context of this invention refers to any molecule modulating the referred cytokine production (e.g., ICE inhibitors in the case of IL-1) and/or action in such a way that its production and/or action is attenuated, reduced, or partially, substantially or completely prevented or blocked.

[0085] An inhibitor of production can be any molecule negatively affecting the synthesis, processing or maturation of said cytokine. The inhibitors, considered according to the invention can be, for example, suppressors of gene expression of the cytokine, antisense mRNAs reducing or preventing the transcription of the cytokine mRNA or ribozymes leading to degradation of the mRNA, proteins impairing correct folding, or partially or substantially preventing secretion of said cytokine, proteases degrading the cytokine and the like.

[0086] Cytokine antagonists exert their activity in several ways. Antagonists can bind to or sequester the cytokine molecule itself with sufficient affinity and specificity to partially or substantially neutralize the cytokine epitope or epitopes responsible for the cytokine receptor binding (hereinafter termed “sequestering antagonists”). A sequestering antagonist may be, for example, an antibody directed against the cytokine, a truncated form of the cytokine receptor (e.g., soluble receptor TNFRI and TNFRII in the case of TNF), comprising the extracellular domains of the receptor or functional portions thereof etc. Alternatively, cytokine antagonists can inhibit the cytokine-signaling pathway activated by the cell surface receptor after cytokine binding (hereinafter termed “signaling antagonists”). An antagonist can be also a molecule that binds the receptor but is not able to trigger the signaling pathway activated upon binding of the cytokine to said receptor (e.g., IL1-Ra Dinarello 1996). All groups of antagonists are useful, either alone or together, in combination with an IL-18 inhibitor, in the therapy of sepsis.

[0087] The IL-18 inhibitor can be used simultaneously, sequentially or separately with the above described cytokine inhibitors.

[0088] The invention further relates to the use of an expression vector comprising the coding sequence of an inhibitor of IL-18 in the preparation of a medicament for the prevention and/or treatment of sepsis. A gene therapeutical approach is thus used for treating and/or preventing the disease. Advantageously, the expression of the IL-18 inhibitor will then be in situ, thus efficiently blocking IL-18 directly in the tissue(s) or cells affected by the disease.

[0089] The use of a vector for inducing and/or enhancing the endogenous production of an inhibitor of IL-18 in a cell normally silent for expression of an IL-18 inhibitor, or which expresses amounts of the inhibitor which are not sufficient, are also contemplated according to the invention. The vector may comprise regulatory sequences functional in the cells desired to express the inhibitor or IL-18. Such regulatory sequences may be promoters or enhancers, for example. The regulatory sequence may then be introduced into the right locus of the genome by homologous recombination, thus operably linking the regulatory sequence with the gene, the expression of which is required to be induced or enhanced. The technology is usually referred to as “endogenous gene activation” (EGA), and it is described, e.g., in WO 91/09955.

[0090] The invention comprise also the administration of genetically modifid cells, able to produce an inhibitor of IL-18 for the treatment or prevention of sepsis.

[0091] It will be understood by the person skilled in the art that it is also possible to shut down IL-18 expression using the same technique, i.e., by introducing a negative regulation element, e.g., a silencing element, into the gene locus of IL-18, thus leading to down-regulation or prevention of IL-18 expression. The person skilled in the art will understand that such down-regulation or silencing of IL-18 expression has the same effect as the use of an IL-18 inhibitor in order to prevent and/or treat disease.

[0092] The definition of “pharmaceutically acceptable” is meant to encompass any carrier, which does not interfere with effectiveness of the biological activity of the active ingredient and that is not toxic to the host to which it is administered. For example, for parenteral (e.g., intravenous, subcutaneous, intramuscular) administration, the active protein(s) may be formulated in a unit dosage form for injection in vehicles such as saline, dextrose solution, serum albumin and Ringer's solution.

[0093] The active ingredients of the pharmaceutical composition according to the invention can be administered to an individual in a variety of ways. The routes of administration include intradermal, transdermal (e.g., in slow release formulations), intramuscular, intraperitoneal, intravenous, subcutaneous, oral, epidural, topical, and intranasal routes. Any other therapeutically efficacious route of administration can be used, for example absorption through epithelial or endothelial tissues or by gene therapy wherein a DNA molecule encoding the active agent is administered to the patient (e.g., via a vector), which causes the active agent to be expressed and secreted in vivo. In addition, the protein(s) according to the invention can be administered together with other components of biologically active agents such as pharmaceutically acceptable surfactants, excipients, carriers, diluents and vehicles.

[0094] For parenteral (e.g., intravenous, subcutaneous, intramuscular) administration, the active protein(s) can be formulated as a solution, suspension, emulsion or lyophilised powder in association with a pharmaceutically acceptable parenteral vehicle (e.g., water, saline, dextrose solution) and additives that maintain isotonicity (e.g., mannitol) or chemical stability (e.g., preservatives and buffers). The formulation is sterilized by commonly used techniques.

[0095] The bioavailability of the active protein(s) according to the invention can also be ameliorated by using conjugation procedures which increase the half-life of the molecule in the human body, for example linking the molecule to polyethylenglycol, as described in the PCT Patent Application WO 92/13095.

[0096] The therapeutically effective amounts of the active protein(s) will be a function of many variables, including the type of antagonist, the affinity of the antagonist for IL-18, any residual cytotoxic activity exhibited by the antagonists, the route of administration, the clinical condition of the patient (including the desirability of maintaining a non-toxic level of endogenous IL-18 activity).

[0097] A “therapeutically effective amount” is such that when administered, the IL-18 inhibitor results in inhibition of the biological activity of IL-18. The dosage administered, as single or multiple doses, to an individual will vary depending upon a variety of factors, including IL-18 inhibitor pharmacokinetic properties, the route of administration, patient conditions and characteristics (sex, age, body weight, health, size), extent of symptoms, concurrent treatments, frequency of treatment and the effect desired. Adjustment and manipulation of established dosage ranges are well within the ability of those skilled in the art, as well as in vitro and in vivo methods of determining the inhibition of IL-18 in an individual.

[0098] According to the invention, the IL-18 inhibitor can be administered prophylactically or therapeutically to an individual in need prior to, simultaneously or sequentially with other therapeutic regimens or agents (e.g., multiple drug regimens), in a therapeutically effective amount, in particular with an IL-12 inhibitor and/or IL-1 inhibitor, interferon and TNF antagonist. Active agents that are administered simultaneously with other therapeutic agents can be administered in the same or different compositions.

[0099] The invention further relates to a method for the preparation of a pharmaceutical composition comprising admixing an effective amount of an IL-18 inhibitor and/or an IL-12 inhibitor and/or IL-1 inhibitor, interferon and/or a TNF antagonist with a pharmaceutically acceptable carrier.

[0100] Having now described the invention, it will be more readily understood by reference to the following examples that are provided by way of illustration and are not intended to be limiting of the present invention.

EXAMPLES

Example 1

[0101] Levels of serum IL-18BPa and IL-18 in healthy individuals and sepsis patients.

[0102] Measurement of specific circulating cytokines, and their natural inhibitors in health and disease provides information about their involvement in progression and severity of a disease. As mentioned in the background section, one of the key mediators of sepsis is IFN-γ. Since IL-18 is a coinducer of IFN-γ, the level of IL-18 and its natural inhibitor, IL-18BP splice variant a, were monitored in sepsis patients and compared to the levels found in healthy subjects by using specific ELISAs (example 3).

[0103] Levels of IL-18 and IL-18BPa in healthy subjects.

[0104] The mean level of IL-18 in 107 healthy donors was 64±17 pg/ml as measured by the ECL assay (Pomerantz et al. 2001). The ECL assay was tested for interference by related proteins. It was found that it was no affected by the presence of mature IL-1β or proIL1β, whereas pro-IL-18 was cross-reactive. Therefore, as much as 20% of the detected mature IL-18 in human serum samples in the present study may be pro-IL-18. The ECL assay of IL-18 was not affected by IL18BPa at a concentration≦160 ng/ml.

[0105] The levels of IL-18BPa were tested in the serum from the 107 healthy individuals by ELISA (example 3). The levels of IL-18BPa ranged from 0.5 ng/ml to as high as 7 ng/ml, with an average of 2.15±0.15 ng/ml (FIG. 1).

[0106] Because both IL-18 and IL-18BPa are concomitantly present in the serum, some of the IL-18 may be present in a complex with IL-18BPa. The level of free IL-18 was calculated based on the average level of total IL-18 (2.15 ng/ml). Free IL-18 was determined according to the law of mass action. The calculation was based on the following parameters: the concentrations of total IL-18 as determined by the ECL assay; the concentration of total IL-18BPa as determined by the ELISA; a 1:1 stoichiometry in the complex of IL-18BPa and IL-18 and a dissociation constant (Kd) of 0.4 nM (Novick et al. 1999 and Kim et al. 2000). In an equilibrium system L+R⇄LR where L represents IL-18 and R represents IL-18BP the following equations are applicable:

Kd=[LR]/[L

free

][R

free
]

L

free

=L

total

−LR

R

free

=R

total

−LR

[0107] By substituting: Ltotal=64±17 pg/ml (mean level). Rtotal=2.15±0.15 ng/ml (average) and Kd=0.4 nM, it was found that in healthy subjects about 51.2 pg/ml IL-18 (about 80% from total) is in its free form.

[0108] Levels of IL-18 and IL-18BPa in Sepsis Patients.

[0109] The levels of IL-18 and of IL-18BPa were tested in 192 sera samples from 42 septic patients immediately upon admission and during hospitalisation. The levels of both IL-18 and IL-18BPa were significantly more elevated in sepsis patients in comparison with the healthy subjects (FIG. 2 A), and a broad distribution of the values was observed (FIG. 2 B). Moreover, these levels were even higher in these patients at the day of admission, showing a 22 fold increase in the level of IL-18 compared with healthy individuals (1.5±0.4 ng/ml versus 0.064±0.17 ng/ml) and a 13 fold increase in the level of IL-18BPa (28.6±4.5 versus 2.15±0.15 ng/ml, FIG. 2A). No statistically significant correlation between creatinine levels and either IL-18 or IL-18BPa concentrations in these sera could be observed (assessed by APACHE II score Knaus et al. 1993), suggesting that elevated IL-18 and IL-18BPa levels in these patients were not due to renal failure.

[0110] Because serum IL-18 and IL-18BPa levels in sepsis patients varied considerably (FIG. 2B) the levels of free serum IL-18 in individual samples were calculated. The calculations were done as previously described, using the same three equations and substitution of the Kd, Ltotal, Rtotal values found experimentally. The calculations show that IL-18BPa reduced the level of free IL-18 in most patients (FIG. 3). Notably, this effect was particularly strong when total IL-18 was very high. For example, in two patients, serum IL-18 reached 0.5 nM (10 ng/ml), a 150-fold increase over healthy individuals. However, considering binding to the circulating IL-18BPa (27 ng/ml and 41.2 ng/ml), the level of free IL-18 in these two patients dropped by 78% and 84%, respectively (FIG. 3). Therefore, most of the serum IL-18 is blocked by the circulating IL-18BPa. Yet, according to these calculations, the remaining free IL-18 is still higher than that found in healthy individuals. Therefore, administration of exogenous IL-18BPa to septic patients is expected to further lower the free circulating IL-18 level, causing alleviation of the disease outcome.

Example 2

[0111] Effect of IL-18BPa on S. epidermidis-induced IFN-γ Production in Cells Present in Whole Blood Samples from Healthy Subjects.

[0112] As mentioned in the background section the Gram-positive bacteria Staphylococcus epidermidis is known to cause sepsis. Induction of cytokines, e.g., IL-1, IFN-γ and TNF-α are key mediators for this pathology. Since IL-18 is a co-inducer of IFN-γ, the effect of its inhibition on Staphylococcus epidermidis IFN-γ induction, was tested. The IL-18BPa, used as the IL-18 inhibitor, was a recombinant histidine tagged version produced in CHO cells.

[0113] 0.5 ml of blood was mixed in 5 ml 12×75 mm round-bottom polypropylene tubes (Falcon, Becton Dickinson Labware, Franklin Lakes, NL) with 0.5 ml of RPMI growth medium (Cellgro Mediatech, Hendon, Va. supplemented with 10 mM L-glutamine, 100 U/ml penicillin 100 μg/ml streptomycin and 10% FBS [Gibco BRL, Grand Island, N.Y.]) containing S. epidermidis (from ATCC) with or without IL-18BP. The samples were incubated at 37° C. (5% CO2) for 48 hours followed by treatment with triton X-100 (Bio-Rad Laboratories, Richmond, Calif.) at 0.5% final concentration to lyse the cells present in the whole blood sample. The tubes containing the samples were inverted several times until the blood sample showed a clear appearance. IFN-γ concentration in the lysed samples of blood, which represents both intracellular and secreted cytokine, was measured by electrochemiluminescence (ECL) as described by Pomerantz et al. (2001).

[0114] For this study whole blood from healthy, non-smoking volunteers was used. The blood was taken by venipuncture and kept in heparinized tubes. S. epidermidis was propagated in brain-heart infusion broth for 24 hours, washed in pyrogen free saline and boiled as described by Aiura et al. (1993). The concentration of heat-killed bacteria was adjusted to 10 bacterial cells per white blood cell (WBC).

[0115] The results in FIG. 4 show that IL-18BPa is able to inhibit the S. epidermidis induction of IFN-γ.

[0116] Since IFN-γ is known to be co-stimulated by IL-18 and IL-12, the eftect of the combination of IL-18BPa and anti IL-12 specific antibodies (anti human IL-12 Mab 11.5.14, Preprotech, Rocky Hill, N.J.) on IFN-γ induction directed by S. epidermidis, was tested. This induction was tested in the presence of 125 ng/ml IL-18BPa (histidine tagged IL-18BPa produced in COS cells and purified over a talon column as described by Novick et al. 1999) and 2.5 μg/ml anti human IL-12 specific antibody. The results shown in FIG. 5 suggest that anti IL-12 specific antibodies potentiate the inhibitory effect of IL-18BPa on the IFN-γ induction by S. epidermidis.

Example 3

[0117] Development of an IL-18BP Specific ELISA Test.

[0118] ELISA comprised two anti IL-18BPa antibodies: murine Mab 582.10, a subclone of Mab 582 described in Example 4, as the capture antibody and rabbit polyclonal antibody for detection (Example 4). Microtiter 96-well ELISA plates (Maxisorb; Nunc A/S, Roskilde, Denmark) were coated with anti IL-18BPa MAb No. 582.10 (a subclone of MAb 582, 4 μg/ml in PBS) overnight at 4° C. The plates were washed with PBS containing 0.05% Tween 20 (washing solution) and blocked (2 h, 37° C.) with BSA stock solution (KPL, Geithersburg, Md.) diluted 1:10 in water. BSA stock solution was diluted 1:15 in water (diluent) for the dilution of all tested samples and the detecting antibody. Sera samples were diluted at least 1:5 in the diluent and 100 μl aliquots were added to the wells. Highly pure rIL-18BPa (prepared in CHO and purified by immunoaffinity using protein G-purified Mab N 430 specific for IL-18BP shown in table 1 example 4) was diluted by 7 serial two-fold dilutions (4 to 0.062 ng/ml) and added to each ELISA plate for the generation of a standard curve. The plates were incubated for 2 hrs at 37° C. and washed 3 times with the washing solution. Rabbit anti IL-18BPa serum (1:5000 in diluent, 100 μl/well) was added and the plates were further incubated for 2 hrs at 37° C. The plates were washed 3 times, a conjugate of goat-anti-rabbit horseradish peroxidase (HRP, Jackson ImmunoResearch Labs, 1:10,000 in PBS, 100 pl/well) was added and the plates were incubated for 1 h at 37° C. The plates were washed 3 times and developed by the addition of OPD Peroxidase substrate (o-phenylenediamine dihydrochloride tablets, Sigma) for 30 min at room temperature. The reaction was stopped by 3N HCl (100 μl) and the absorbance at 492 nm was determined by an ELISA reader. The OD was plotted as a function of IL-18BPa concentration and linearity was observed in a range of 0.12-2.00 ng/ml IL-18BPa (FIG. 6).

[0119] The IL-18BPa standard curve in the absence of serum or in the presence of up to 20% human serum remained the same. Since IL-18BPa binds IL-18 with a very high affinity, it was necessary to determine whether ELISA distinguishes between free and bound IL-18BPa. It was found that IL-18 interferes with the IL-18 ELISA however, the interference is insignificant in serum samples. In 90% of sepsis patients, serum IL-18 levels were under 4 ng/ml (see below). Such sera samples have elevated IL-18BPa, requiring a 5 to 20-fold dilution prior to measuring IL-18BPa. At such dilutions, IL-18 interference with the IL-18BPa ELISA is less than 10% (FIG. 7). Other related cytokines, including prolL-18, used at a 10-fold molar excess over IL-1 8BPa, as well as a 200-fold excess of mature IL-1β do not interfere with the assay.

[0120] The most abundant isoform of human IL-18BP is IL-18BPa, whereas isoforms b, c and d are minor splice variants (Novick et al. 1999 and Kim et al. 2000). IL-18BPa exhibits the highest affinity for IL-18 (Kim et al 2000). The affinity of IL-18BPc for IL-18 is 10 fold lower, whereas isoforms b and d do not bind or neutralize IL-18. It was therefore important to determine the cross-reactivity of IL-18BPa in ELISA with the other isoforms of IL-18BP. As shown in FIG. 8, human IL-18BPc generated a 10-fold lower signal on a weight basis compared with huIL-18BPa, whereas human isoforms b and d generated an insignificant signal in the ELISA.

Example 4

[0121] Generation of Anti IL-18BP Specific Antibodies.

[0122] A rabbit was injected with rIL-18BPa-His6 for the generation of polyclonal antibodies.

[0123] For the production of monoclonal antibodies, female Balb/C mice were injected 5 times with 10 μg of recombinant histidine tagged IL-18BPa (rIL-18BPa-His6). The mouse exhibiting the highest titer as determined by an inverted radioimmunoassay (IRIA example 5) or solid phase RIA (sRIA, example 5) was given a final boost intraperitoneally 4 and 3 days before fusion. Lymphocytes were prepared from spleen and fusion to NSO/1 myeloma cells was performed. Hybridomas that were found to produce antibodies to IL-18BPa were subcloned by limiting dilution. The clones generated were assayed by IRIA (Example 5). Representative hybridomas are shown in Table 1.

4TABLE 1representative hybridomas producing anti IL-18BPaIRIA1sRIA2MAb No.(cpm)(cpm)14823912794129716526483369316127624306887325443310091530046031994326485400130105821500017897601104619281Plates coated with goat anti mouse antibodies and hybridomas detected with 1251 IL 18BPa. 2Plates coated with urinary IL 18BP and hybridomas detected with 125I goat anti mouse antibodies.

[0124] Hybridomas secreting antibodies directed against the histidine tag were discarded. Antibodies were further characterized by sRIA for their ability to recognize the naturally occurring IL-18BP (purified from urine). Binding characteristics of several positive hybridomas are shown in Table 1. Hybridomas No. 148, 430, 460 and 582 were positive with both, recombinant and urinary IL-18BP. Antibodies suitable for Western blotting, immunoprecipitation, immunoaffinity purification and for development of a specific ELISA were obtained. Positive clones producing anti IL-18BP specific antibodies were injected into Balb/C mice pre-primed with pristane for the production of ascites. The isotypes of the antibodies were defined with the use of an anti mouse IgG ELISA (Amersham-Pharmacia Biotech). Mab 582, which was highly reactive with the recombinant and the native IL-18BP (Table 1) was used for the assembly of the IL-18BP specific ELISA (Example 3).

[0125] Antibodies were tested by sRIA in the presence of IL-18 (Example 5) for their ability to recognize a complex of IL-18BPa with IL-18. Most antibodies were unable to recognize

[0126] IL-18BP when it was complexed to IL-18. Therefore, these antibodies appear to be directed against the ligand-binding domain of IL-18BPa.

Example 5

[0127] Radioimunoassays for the Detection of Anti IL-18BP Antibody Producing Cell Clones.

[0128] Inverted Radioimmunoassay (IRIA).

[0129] PVC microtiter plates (Dynatech Laboratories, Alexandria, Va.) were coated overnight at 4° C. with affinity-purified goat anti-mouse F (ab) 2 antibodies (10 μg/ml, 100 μl/well; Jackson ImmunoResearch Labs). The plates were then washed twice with PBS containing 0.05% Tween 20 (washing solution) and blocked with BSA (0.5% in washing solution) for 2 hrs at 37° C. Hybridoma culture supernatants (100 μl/well) were added and the plates were incubated for 2 hrs at room temperature. The plates were washed three times, 125I-rIL-18BPa-His6 (105 cpm in 100 μl) was added to each well and the plates were incubated for 5 hrs at 22° C. The plates were then washed three times and individual wells were counted in a gamma counter. Hybridomas generating supernatants, which exhibited bound radioactivity at levels 5 folds higher than the negative control, were considered positive.

[0130] Solid phase RIA (sRIA).

[0131] rIL-18BPa (5 μg/ml) was used as the capture antigen and 125I-goat anti mouse antibodies (100 μl, 105 cpm) were used for detection. Blocking and washings were done as above. Positive clones were further screened by sRIA for their ability to recognize the IL-18BP isolated from concentrated human urine (Novick et al. 1999). Microtiter plates were coated with ligand-affinity purified urinary IL-18BP (1 μg/ml), blocked and washed as above. Hybridoma supernatants (100 μl) were added and detection was done with 125I-goat anti mouse antibodies (105 cpm in 100 μl).

[0132] sRIA for Antibodies Specific for the Ligand-binding Site of IL-18BP.

[0133] Microtiter plates were coated with either urinary IL-18BP (0.5 μg/ml) or rIL-18BPa (5 μg/ml), blocked and washed as in sRIA. Recombinant human IL-18 (50 μl) was added to a final concentration of 1.5 μg/ml (15 min at room temperature), followed by the addition of hybridoma supernatants (50 μl). Detection was done with 125I-goat anti mouse antibodies (105 cpm in 100 μl, 2 h at room temperature).

Example 6

[0134] Myocardial IL-18 Content Following LPS.

[0135] TNFα and IL-1β have been implicated in cardiac dysfunction during sepsis, since IL-18 is a pro-inflammatory cytokine known to mediate the production of TNFα and IL-1β, the concentration of IL-18 on LPS-induced cardiac dysfunction was tested.

[0136] Mice were treated with either vehicle (saline) or LPS. Hearts were harvested at 2, 4 and 6 hours following LPS administration and homogenized to determine myocardial IL-18 content by ELISA (Kit purchased from R&D Systems (Minneapolis Minn.). The results in FIG. 9 show a two-fold increase in myocardial IL-18 content at 4 hours following LPS administration, which indicates that IL-18 is involved in cardiac dysfunction during sepsis.

Example 7

[0137] Effect of Neutralization of IL-18 on LPS-induced Myocardial Dysfunction.

[0138] In the previous example an increase in the IL-18 content has been found in cardiac dysfunction induced by LPS. Therefore, the effect of neutralization of IL-18 on LPS-induced myocardial dysfunction was evaluated.

[0139] Myocardial function was determined by an isovolumetric, nonrecirculating Langendorff technique as described previously (Meng et al. 1998). Isolated hearts were perfused with normothermic Krebs-Henseleit solution containing 11.0 mmol/l glucose, 1.2 mmol/l CaCl2, 4.7 mmol/l KCL, 25 mmol/l NaHCO3, 119 mmol/l NaCl, 1.17 mmol/l MgSO4 and 1.18 mmol/l KH2PO4. A latex balloon was inserted in the left ventricle via the left atrium and inflated with water to achieve a left ventricular and diastolic pressure (LVEDP) of 10 mmHg. Pacing wires were attached to the right atrium and hearts were paced at 300 beats per minute. Coronary flow was quantified by collecting the effluent from the pulmonary arteries. Myocardial temperature was maintained at 37° C. Left ventricular developed pressure (LVDP), its first derivatives (+dP/dt, −dP/dt) and LVEDP were continuously recorded by a computerized pressure amplifier-digitizer (Maclab 8, AD Instrument, Cupertino, Calif.). After a 20 minutes equilibration period LVDP and +/−dP/dt were determined at varied LVEDP levels (10, 15, and 20 mmHg).

[0140] Following LPS administration, the left ventricular developed pressure (LVDP) was reduced by 38% compared to saline controls (36.3+/−1.9 mmHg vs. 59.1+/− mmHg, P<0.001, FIG. 10). Pre treatment of mice 30 minutes prior to LPS administration with normal rabbit serum (NRS) had minimal influence on LPS-induced myocardial dysfunction; however pretreatment with IL-18 neutralizing antibody abrogated dysfunction (FIG. 10). Coronary flow was not different between the groups (not shown).

[0141] The results indicate that neutralization of IL-18 protects against LPS-induced myocardial dysfunction.

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Use of IL-18 inhibitors for the treatment or prevention of sepsis

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