Ixodes scapularis tissue factor pathway inhibitor

FIELD OF THE INVENTION

[0002] The present invention relates to the field of molecular biology. The present invention discloses the discovery of the novel protein Ixolaris. Ixolaris has anticoagulant activity and can be isolated and purified from the salivary glands of ticks or made by recombinant methods using various DNA expression techniques.

BACKGROUND OF THE INVENTION

[0003] Following tissue injury, exposition of membrane-bound Tissue Factor (TF), is a crucial step in the initiation of blood coagulation. TF binds to blood coagulation Factor VIIa, and the binary Factor VIIa/TF complex then activates Factor X to Factor Xa, leading to thrombin generation and fibrin formation (Broze, G. J. Jr. et al. 1988 Blood 71:335-343; Pedersen, A. H. et al. 1990 J Biol Chem 254:16786-16793; Rao, L. V. M., and Rapaport, S. I. 1987 Blood 69:645-651). Initiation of blood coagulation by Factor VIIa/TF is under control of tissue factor pathway inhibitor (TFPI) (Pedersen, A. H. et al. 1990 J Biol Chem 254:16786-16793; Rao, L. V. M., and Rapaport, S. I. 1987 Blood 69:645-651; Broze, G. J. Jr, and Miletich, J. P. 1987 PNAS USA 84:1886-1890; Rapaport, S. I. 1989 Blood 73:359-365), a 34- to 43-kDa multidomain protein with an acidic aminoterminus, three typical Kunitz-type inhibitor domains, and a basic carboxy terminus (Girard, T. J. et al. 1990 Science 248:1421-1424: Wun, T-C. et al. 1988 J Biol Chem 263:6001-6004). The second Kunitz domain binds and inhibits Factor Xa, and the first Kunitz domain binds to Factor VIIa/TF through formation of a final quarternary inhibitory complex consisting of Factor Xa-TFPI-Factor VIIa/TF (Lindhout, T., Fransen, J., and Willems, G. 1995 Thromb Haemost 74:910-915; Hamamoto, T. et al 1993 J Biol Chem 268:8704-8710; Broze, G. J. et al. 1990 Biochemistry 29:7539-7546; Rao, L. V. M., and Ruf, W. 1995 Biochemistry 34:10867-10871;. Baugh, R. J. et al. 1998 J Biol Chem 273:4378-4386; Wesselschmidt, R. et al. 1992 Blood 79:2004-2010). In addition to TFPI and other physiologic inhibitors of blood coagulation (e.g., antithrombin), a number of coagulation inhibitors from the salivary gland of blood-sucking invertebrates have been characterized (Law, L. H., Ribeiro, J. M., and Wells, M. A. 1992 Annu Rev Biochem 61:87-111; Markwardt, F. 1994 Pharmazie 49:313-316).

[0004] Ticks, such as Ixodes scapularis, are ectoparasites that feed for several days with their mouthparts embedded in their vertebrate hosts. Ixodes scapularis is a vector of Lyme disease. Lyme disease is a spirochetal illness caused by Borrelia burgdorferi, which is injected into the vertebrate host together with tick saliva. A number of pharmacologic properties have been described in I. scapularis saliva including inhibitors of neutrophil function (Ribeiro, J. M. C., Weis, J. J., and Telford, S. R. III 1990 Exp Parasitol 70:382-388), anticomplement (Ribeiro, J. M. C., 1987 Exp Parasitol 64:347-353; Valenzuela, J. G. et al. 2000 J Biol Chem 275:18717-18723), and anaphilatoxin-inactivating activities (Ribeiro, J. M. C., and Spielman A. 1986 Exp Parasitol 62:292-297) in addition to antiinflammatory and immunosuppresive components (Ribeiro, J. M. C. et al. 1985 J Exp Med 161:332-344). Antihemostatic compounds have also been molecularly characterized in the soft tick O. moubatta, including a platelet integrin αIIbβ3 integrin antagonist (Karczewski, J. et al. 1994 J Biol Chem 269:6702-6708) and inhibitors of blood coagulation such as ornithodorin, a thrombin inhibitor (Locht, A. et al. 1996 EMBO J 15:6011-6017), and tick anticoagulant peptide, a Factor Xa inhibitor (Waxman, L. et al. 1990 Science 248:593-596). The presence of thrombin and Factor Xa inhibitors seems to be a successful strategy evolutionarily developed by ticks to successfully feed on blood, because both molecules play an essential role in two key steps necessary for maintenance of the blood coagulation cascade (Jenny, N. S., and Mann K. G. in: Thrombosis and Hemorrhage, 2d ed. 1998, Loscalzo J, Schafer A I eds. Baltimore, Md.: Williams and Wilkins 1998 p 3; Davie, E. W. et al. 1991 Biochemistry 30:10363-10370) however, an inhibitor of Factor VIIa/TF has not yet been molecularly characterized.

SEGUE TO THE DESCRIPTION

[0005] To understand the complexity of I. scapularis saliva, with a primary focus on antihemostatic molecules, massive sequencing of a cDNA library of the salivary gland of I. scapularis has been performed. Together with a complementary functional approach, a clone with sequence homology to TFPI has been expressed as an active molecule and its anticoagulant mechanism studied. The recombinant protein has the same properties found in saliva. This molecule, called Ixolaris, is characterized as a specific inhibitor of FactorVIIa/TF, with unique binding properties to Factor X.

SUMMARY OF THE INVENTION

[0006] Saliva of the hard tick, Ixodes scapularis, has a repertoire of compounds that counteracts host defenses. Following sequencing of an I. scapularis salivary gland cDNA library, a clone with sequence homology to tissue factor pathway inhibitor (TFPI) was identified. This cDNA codes for a mature protein, herein called Ixolaris, with 140 amino acids containing 10 cysteines and two Kunitz-like domains. Recombinant Ixolaris inhibits Factor VIIa(FVIIa)-induced Factor X(FX) activation with an IC50 in the pM range. Ixolaris behaves as a fast-and-tight ligand of FXa and des-Gla-FXa (γ-carboxyglutamic acid domainless FXa), increasing their esterolytic activity ˜2fold. Ixolaris blocks the amidolytic activity of FVIIa/TF only in the presence of DEGR-FX or DEGR-FXa, but not des-Gla-DEGR-FXa. This result indicates that both FXa and FX are scaffolds for Ixolaris and implies that Gla-domain is necessary for Ixolaris/FX(a)/FVIIa/TF complex formation. Additionally, we show that Ixolaris inhibits FIX activation by FVIIa/TF (Factor VIIa exosite inhibitor), and remarkable inhibition was achieved in the presence of FX/FXa. Ixolaris/FXa forms a 1:1 complex with FVIIa/TF. Western blotting using antibodies to Factor X and Factor VIIa shows that Ixolaris shifts the migration pattern of both Factor X and Factor Xa, but not Factor VIIa. Ixolaris also inhibits Factor Xa generated by human umbilical vein endothelial cells (HUVEC) expressing TF. Ixolaris is envisioned as being useful as an alternative anticoagulant in cardiovascular diseases as well as a vaccine target to prevent Lyme disease.

SUMMARY OF SEQUENCES

[0007] Appendix A depicts Ixolaris and its carboxy truncations. Appendix B depicts Ixolaris and its amino truncations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]
FIG. 1. Hypothetical Model for Ixolaris Binding. The second Kunitz domain of Ixolaris binds to Factor Xa or Factor X. Subsequently, the first Kunitz domain of Ixolaris in this complex binds to the Factor VIIa/TF complex.

[0009]
FIG. 2. Blood Coagulation Cascade. Ixolaris disrupts the extrinsic pathway in the blood coagulation cascade by inhibiting factor VIIa dependent Factor X activation. By inhibiting Factor Xa and Factor VIIa/TF, Ixolaris prevents thrombin generation and fibrin formation. Through this mechanism blood coagulation is inhibited.

[0010]
FIG. 3. (A) Nucleotide sequence (SEQ ID NO: 470) and deduced amino acid sequence of Ixolaris (SEQ ID NO: 471). The nucleotides and amino acids are numbered from the translation starting site ATG. The signal peptide sequence is underlined. (B) Alignment of mature Ixolaris (SEQ ID NO: 138) with human TFPI (SEQ ID NO: 472). Identical amino acids are in bold and underlined.

[0011]
FIG. 4. Predicted secondary folding structure for Ixolaris. Disulfide bonds are assumed on the basis of the crystal structure of bovine pancreatic trypsin inhibitor (Huber, R. et al. 1974 J Mol Biol 89:73-101). The charges of the amino acid side chains are shown. Predicted N-linked glycosylation sites are Asn65, Asn98, and Asn136.

[0012]
FIG. 5. Identification of TFPI-like activity in the saliva of I. Scapularis (30 μL) (A) or the 20×concentrated supernatant of High Five cells transfected with the full-length clone coding for Ixolaris (B). Molecular sieving chromatography was done with a 3.2×300 mm Superdex 75 column eluted at 0.05 mL/min with 10 mM Hepes buffer pH 7.2, 0.15 M NaCl. Fractions were collected every two drops, with time recording for change in fractions done by a program linking the fraction collector to a computer. An aliquot was taken from each fraction and tested for inhibition of Factor X activation by factor VIIa/Tissue Factor, as described in Example. Absorbance at 280 nm (—); inhibitory activity (-&Circlesolid;-).

[0013]
FIG. 6. Purification of Ixolaris. Recombinant Ixolaris was purified in (A) a MonoQ anion-exchange column, (B) Vydac 218TP510 octadecyl-silica reverse-phase column and (C) Macrosphere octadecylsilica reverse-phase column (—). Column fractions were diluted 1:4,000 (A), 1:125,000 (B), and 1:800,000 (C) and measured for inhibition of Factor VIIa/TF-mediated Factor X activation (-&Circlesolid;-). (D) An aliquot (0.2 μg) of the fraction eluted at 83 minutes of retention time was treated under non-reducing (Lane 1, NR) and reducing (lane 2, R) conditions and applied to 12% NU-PAGE (MOPS buffer) in the presence of an antioxidant. Lane 3, N: PAGE of Ixolaris under native conditions. Arrows and arrowheads show Ixolaris. Gels were silver stained.

[0014]
FIG. 7. Inhibition of Factor VIIa/TF-induced Factor X activation by Ixolaris. (A) Progress curves: Factor VIIa (1 nM)/TF (0.2 pM) was added to a mixture containing Factor X (200 nM), previously incubated with increasing concentrations of Ixolaris (a, 0 nM; b, 0.1 nM; c, 0.25 nM; d, 0.5 nM; e, 1 nM; f, 2.5 nM; g, 5 nM; h, 10 nM), and S2222 (250 μM). (B) The data generated in (A) were transformed as described in Example to estimate steady-state Factor Xa production, between 0-4 minutes. (C) For determination of the IC50, Vs and Vo obtained between 0-4 minutes were plotted against Ixolaris concentration, at different Factor X concentration: (&Circlesolid;) 3 nM; (▪) 15 nM; (▴) 40 nM; (▾) 75 nM; (∘) 100 nM; (□) 140 nM; (Δ) 175 nM; (∇) 200 nM (n=3). (D) Increase of the K0.5 at different concentrations of Factor X. Vs, inhibited velocity; Vo, control (uninhibited velocity). Progress curves are representative experiments.

[0015]
FIG. 8. Ixolaris binds to Factor X, and Factor Xa, but not to Factor VIIa. Ixolaris (20 nM) was preincubated with Factor X (20 nM), Factor Xa (20 nM), or Factor VIIa (20 nM). PAGE of the sample under non-denaturating conditions was followed by transfer of proteins to PVDF membrane. Factor Xa and Factor VIIa detection was performed using polyclonal anti-Factor Xa or monoclonal antibody anti-Factor VIIa, described in Example. (A) Lane 1, Factor X; lane 2, Factor X plus Ixolaris. (B) Lane 1, Factor Xa; lane 2, Factor Xa plus Ixolaris. (C) Lane 1, Factor VIIa; lane 2, Factor VIIa plus Ixolaris. Each blotting is a representative experiment. Arrows, enzyme; arrowheads, enzyme-inhibitor complex.

[0016]
FIG. 9. Ixolaris binds to Factor Xa and Factor X. (A) Buffer (control; curve a), Ixolaris (0.8 nM, curve b), or human TFPI (20 nM, curve c) and chromogenic substrate (S2222, 250 μM) were incubated at 37° C. for 15 min before addition of Factor Xa (125 pM). (B) Factor Xa (125 pM) and Ixolaris (0-1600 pM) were incubated at 37° C. for 15 min followed by addition of S2222 (250 μM). Reaction was followed for 1 hour at 37° C. ED50 159±3.8 pM. Inset: progress curves of the effects of Ixolaris on Factor Xa esterolytic activity: Ixolaris (a) 0 nM; (b) 40 pM; (c) 80 pM; (d) 160 pM; (e) 300 pM; (f) 600 pM; and (g) 1600 pM. (C) Ixolaris (1.6 nM) was incubated with Factor Xa (125 pM), des-Gla-Factor Xa (600 pM), or thrombin (150 pM), followed by addition of S2222, or S2238 for thrombin. (D) Ixolaris (400 pM) was added to a mixture containing Factor Xa (640 pM) and (▪) DEGR-FXa (0-3.2 nM), or (&Circlesolid;) des-Gla-DEGR-FXa (0-4.8 nM), or (▴) DEGR-FX (0-3.2 nM). After 15 min incubation, reactions were inititated with S2222 (250 μM). Inset: Ixolaris was incubated with DEGR-FXa (0-3.2 nM), or des-Gla-DEGR-FXa (0-3.2 nM), or DEGR-FX (0-3.2 nM), and S2222 (250 μM) followed by addition of Factor Xa (640 pM). Reactants were diluted in Buffer A and substrate hydrolysis was detected at 405 nm. Experiments were performed 3-4 times, in duplicates or triplicates.

[0017]
FIG. 10. Factor Xa and Factor X are scaffolds for Ixolaris in assays for FVIIa/TF amidolytic activity. (A) Ixolaris (15 nM) and DEGR-Factor Xa (0-8 nM) were incubated for 15 min in the presence of S2288 (250 μM) followed by the addition of Factor VIIa/TF (1 nM). a, control; b, Ixolaris; c, Ixolaris plus 0.08 nM DEGR-Factor Xa; d, Ixolaris plus 0.8 nM DEGR-Factor Xa; e, Ixolaris plus 8 nM DEGR-Factor Xa. (B) Ixolaris (15 nM) and DEGR-Factor X (0-8 nM) were incubated for 15 min in the presence of S2222 (250 μM) followed by the addition of Factor VIIa/TF (1 nM). a, control; b, Ixolaris; c, Ixolaris plus 0.08 nM DEGR-Factor X; d, Ixolaris plus 0.8 nM DEGR-Factor X; e, Ixolaris plus 8 nM DEGR-Factor X. (C) Vs/Vo transformation of the data in (A) for DEGR-Factor Xa (&Circlesolid;), (B) for DEGR-Factor X (▴). Ixolaris in the presence of des-Gla-DEGR-Factor Xa did not affect Factor VIIa/TF amidolytic activity (▪). (D) Factor VIIa (1 nM)/TF (0.2 pM) was incubated for 10 min with buffer; 100 pM Ixolaris; 100 pM DEGR-Factor X/Ixolaris; 100 pM DEGR-Factor Xa/Ixolaris; 100 pM DEGR-des-Gla-Factor Xa and added to Factor X (200 nM) and S2222 (250 μM). Chromogenic substrate hydrolysis was followed at absorbance reading at 405 nm, for 1 hour. Three independent experiments were performed.

[0018]
FIG. 11. Ixolaris is a direct inhibitor of Factor VIIa/TF-mediated FIX activation. (A) Factor VIIa/TF (1 nM) was incubated with Ixolaris (0-266 nM) followed by addition of Factor IX (1.4 μM). Factor IXa activation was identified by 4-12% NU-PAGE. The bands correspond to (from the top): uncleaved Factor IX, the heavy chain of Factor IXα, the heavy chain of Factor IXaβ, and the light chain of Factor aβ. Lane 1, 0 min incubation between Factor VIIa/TF and Factor IX. Other lanes, 40 min incubation. Ixolaris concentration are: lane 2, 0 nM; lane 3, 0.26 nM; lane 4, 1.04 nM; lane 5, 2.66 nM; lane 6, 10.4 nM; lane 7, 26.6 nM; lane 8, 104 nM; lane 9, 266 nM (n=4). (B) Densitometry of the bands corresponding to the heavy chain of Factor IXaβ, the light chain of Factor IXaβ is shown. (C) Quantification of the densitometry (for Factor IXaβ) shows dose-dependent inhibition of Factor VIIa/TF-mediated Factor IX activation by Ixolaris (&Circlesolid;). No inhibition of Factor VIIa/TF (1 nM/1 nM) amidolytic activity upon S2288 by Ixolaris was detected (∘) (n=3).

[0019]
FIG. 12. Factor X and Factor Xa are scaffolds for Ixolaris in FVIIa/TF-mediated Factor IX activation assays. (A) Ixolaris (10 nM) was incubated with Factor X derivatives followed by addition of Factor VIIa/TF (0.5 nM). Lane 1, no incubation; lane 2, 0 nM Ixolaris; lane 3, Ixolaris (10 nM); lane 4, DEGR-FX (7.5 nM); lane 5, DEGR-FX (7.5 nM) plus Ixolaris (10 nM); lane 6, DEGR-FXa (7.5 nM); lane 7, DEGR-FXa (7.5 nM) plus Ixolaris (10 nM); lane 8, des-Gla-DEGR-FXa (7.5 nM); lane 9, des-Gla-DEGR-FXa (7.5 nM) plus Ixolaris (10 nM). (B) Ixolaris (20 nM) was incubated with Factor X derivatives followed by addition of Factor VIIa/TF (0.5 nM). Lane 1, no incubation; lane 2, 0 nM Ixolaris; lane 3, Ixolaris (20 nM); lane 4, DEGR-FX (15 nM); lane 5, DEGR-FX (15 nM) plus Ixolaris (20 nM); lane 6, DEGR-FXa (15 nM); lane 7, DEGR-FXa (15 nM) plus Ixolaris (20 nM); lane 8, des-Gla-DEGR-FXa (15 nM); lane 9, des-Gla-DEGR-FXa (15 nM) plus Ixolaris (20 nM). (C) Quantification of the bands corresponding to the heavy chain of Factor IXα,β was performed as in FIG. 11.

[0020]
FIG. 13. Ixolaris inhibits Factor VIIa-TF amidolytic activity in a DEGR-Factor Xa-dependent manner. Ixolaris was incubated with DEGR-Factor Xa (0-4 nM) for 15 minutes at 37° C. followed by addition of Factor VIIa/TF (1 nM/0.8 nM) for 15 minutes at 37° C. S2288 (1 mM) was added, and reactions were followed for 1 hour. (A) Linear regression of the progress curves of the inhibition of Factor VIIa-TF esterolytic activity by Ixolaris (3 nM) in the presence of increasing concentrations of DEGR-Factor Xa: (a) 0 nM; (c) 0.1 nM; (d) 0.25 nM; (e) 0.5 nM; (f) 1 nM; (g) 2.5 nM; (h) 5 nM. In (b), Ixolaris was added in the absence of DEGR-Factor Xa. (B) Progress curves are expressed as Vs/Vo, yielding an IC50 of 0.41±0.04 nM in the presence of DEGR-Factor Xa and Ixolaris (&Circlesolid;). No inhibition was detected in the absence of Ixolaris (▪).

[0021]
FIG. 14. Ixolaris inhibits HUVEC-triggered formation of Factor Xa. A mixture of Factor X (200 nM) and Ixolaris (0-8 nM) previously incubated together at 37° C. for 15 min was added to confluent HUVECs. This step was followed immediately by addition of Factor VIIa (1 nM) to start reactions. After 30 min, 100 μl was removed and added to a 96 well plate containing 100 μl of S2222 (500 μM) diluted in 50 mM Hepes, 100 mM NaCl, 50 mM EDTA, 0.5% BSA, pH 7.4. Absorbance reading at 405 nm (substrate hydrolysis) was followed for 1 h and Factor Xa concentration was estimated by a standard curve, using known concentrations of Factor Xa. Appropriate controls were run in parallel: HUVEC that have not been exposed to LPS (68.4±8.7 pM Factor Xa). LPS-exposed HUVEC in the absence of Factor VIIa (78.08±6.59 pM Factor Xa). Data is the mean ±SE of triplicate experiment. Experiments were performed with HUVEC in the 2nd or 3rd passages.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Hemostasis is the physiological mechanism by which an organism prevents blood loss at a site of injury. The process is comprised of activation of the blood coagulation cascade, vasoconstriction and platelet aggregation. Specifically, exposure of blood to the cell surface tissue factor (TF) and formation of the TF/VII (VIIa) complex initiate the blood coagulation. The TF/VIIa complex then activates both factors IX and X leading to thrombin generation and fibrin formation. Abnormal coagulation underlies pathogenesis of many serious illnesses. In particular, induced expression of TF and TF-mediated coagulation occurs in atherosclerotic plaques, sepsis, malignancy, ARDS and glomerulonephritis. A plasma physiological inhibitor that counteracts the activity of TF/VIIa has been identified—Tissue Factor Pathway Inhibitor (TFPI). TFPI has also been studied for therapeutic purposes. Accordingly, alternative strategies to prevent initiation of blood coagulation, such as the identification of new inhibitors of TF/VIIa, can lead ultimately to the identification of new potential therapeutic agents. In this context, we cloned and expressed tick's tissue factor pathway inhibitor, named Ixolaris. Recombinant Ixolaris is a highly specific inhibitor of the extrinsic pathway that blocks generation of Xa by TF/VIIa with an apparent Ki in the pM range. The mechanism of action of Ixolaris has been studied in detail. Because inactivation of Ixolaris by antibodies will make transmission of Borrelia burgdorferi (the bacteria responsible for Lyme disease) to humans more difficult, Ixolaris is envisioned as a vaccine to protect humans (and their pets) against Lyme disease. It can also be useful as an anticoagulant and antimetastatic molecule in a number of pathological conditions.

[0023] Ixolaris is envisioned as being effective as an anti-coagulant molecule to prevent or ameliorate the morbidity of cardiovascular syndromes, including, but not limited to, coronary heart disease, deep vein thrombosis, pos-infarctus angioplasty, hypercoagulable states, restenosis, arterial thrombosis, microvascular anastomosis, stroke and ischemia-reperfusion injury. Ixolaris is also envisioned as being effective as an anti-metastatic molecule for the treatment of malignant tumors that stain positively to TF (e.g. breast, lung, pancreas, colon, and stomach cancers). It is also envisioned as being used as an anti-coagulant molecule to prevent sepsis-related hypercoagulation states, particularly, endotoxin-induced tissue factor-mediated disseminated intravascular coagulation (DIC). Additionally, it is also envisioned as being effective as an anticoagulant to prevent or ameliorate Acute Respiratory Distress Syndrome (ARDS). Furthermore, it is envisioned as acting as a prototype molecule to study the structure and function of blood coagulation factors involved in the initiation of blood coagulation by the extrinsic pathway, particularly factor Xa, X, and Factor VIIa/TF.

[0024] A salivary gland cDNA library of the tick Ixodes scapularis was randomly cloned and sequenced, identifying a cDNA with high similarity to rabbit tissue factor pathway inhibitor. The full-length nucleotide (SEQ ID NO: 470) and deduced amino acid sequences (SEQ ID NO: 471) of Ixodes TFPI-like protein are shown in FIG. 3A. The translated protein has a short hydrophobic sequence of 25 amino acids typical of signal peptide and an alanine at the N-terminus, according to Signal P software for prediction of N-terminal of proteins (Nielsen, H. et al. 1997 Protein Eng 10:1-6). The mature protein, herein called Ixolaris, contains 140 amino acids (15.7 kDa) (SEQ ID NO: 138), including 10 cysteines and a pI of 4.56. Ixolaris is similar to other members of the Kunitz family of proteins including human TFPI precursor (e value=4e−14, P10646); lacunin from Manduca sexta (1e−12, AAF04457.1); hepatocyte growth factor pathway inhibitor (8e−12, AAF02490.1); inter-α-trypsin inhibitor (bikunin) (7e−11, P04365); amyloid-precursor-like protein (1e−11, CAA54906.1); and basic pancreatic trypsin inhibitor (aprotinin, 1e−05, 1510193A). For comparison, the alignment of Ixolaris and human TFPI sequence (SEQ ID NO: 472) is shown (FIG. 3B). FIG. 4 shows the predicted structure of Ixolaris assumed on the basis of the crystal structure of bovine pancreatic trypsin inhibitor (Huber, R. et al. 1974 J Mol Biol 89:73-101).

[0025] Ixolaris sequence indicates the existence of a salivary anticoagulant directed toward the extrinsic pathway. Thus, we tested chromatographically separated saliva of I. scapularis in an assay measuring activation of Factor X by Factor VIIa/TF. Inhibition of Factor X activation was detected in fractions eluted between 11 and 17 minutes of retention time (FIG. 5A). Because control experiments showed that the activity was not related to a specific inhibitor of Factor Xa, we concluded that saliva of I. scapularis contains TFPI-like molecule(s). Inhibition of α-trombin and trypsin amidolytic activity was also found in other fractions, indicating that other protease inhibitor(s) are present in the salivary gland of I. scapularis.

[0026] To determine whether Ixolaris accounts for the inhibitory activity identified in the saliva, the full-length cDNA of Ixolaris was expressed in insect cells as described in Example. The concentrated supernatant was applied to a gel-filtration column under conditions identical to those described in FIG. 5A. Inhibitory activity was found with the same retention time as described for the salivary fractions (FIG. 5B). No activity was found with the supernatants of cells transfected with the control plasmid. These data indicate that Ixolaris and the salivary TFPI-like molecule have similar chromatographic properties on gel-filtration.

[0027] To obtain larger amounts of purified Ixolaris, supernatants of transfected cells were chromatographically purified (FIG. 6). The resulting final fraction was analyzed by PAGE under denaturating and non-reducing conditions (FIG. 6D, lane 1, NR), where a major band of approximately 24 kDa in addition to a minor component of approximately 15.5 kDa were silver stained. Under reducing conditions, a band of approximately 27 kDa and a minor component of approximately 15.5 kDa band were detected (FIG. 6D, lane 2, R), PAGE of the sample under native conditions shows that only one major band has been stained (FIG. 6D, lane 3, N).

[0028] The mechanism of inhibition of blood coagulation by Ixolaris was then studied. In these experiments, Ixolaris (0-10 nM) and Factor X (200 nM) were incubated at 37° C. for 15 minutes, followed by addition of Factor VIIa (1 nM)/TF (0.2 pM) and chromogenic substrate for Factor Xa (S2222). The progress curves were characterized by a lag-phase, followed by significant hydrolytic increase between 5 and 20 minutes, and a linear augmentation thereafter showing accumulative production of Factor Xa (FIG. 7A). To estimate the production of Factor Xa at each minute, Δ absorbance (A 405/min) was used (Lindhout, T. et al. 1995 Thromb Haemost 74:910-915) and a linear increase of Factor Xa production was thus observed (FIG. 7B). Experiments were then performed at different concentrations of Factor X, ranging from 3 to 200 nM. Data were transformed according to Vs/Vo, where Vs and Vo are the velocities of Factor Xa production in the presence and absence of inhibitor, respectively. Experimental results indicate that Ixolaris blocks Factor Xa production at all Factor X concentrations tested (FIG. 7C), However, significant increases of Ixolaris IC50 was attained at higher Factor X concentrations; from 30 pM at 3 nM FX to 420 pM at 200 nM FX (FIG. 7C). At 1 nM Factor X, IC50 as low as 3 pM was obtained. Ixolaris IC50 varied linearly as a function of Factor X concentration (FIG. 7D). Under identical experimental conditions, recombinant full-length clone human TFPI (0-10 nM) blocks Factor Xa production with IC50 of approximately 610 pM at 15 nM Factor X, approximately 620 pM at 75 nM Factor X and approximately 625 pM at 200 nM Factor X. The remarkable effect of Factor X concentration in the IC50 of Ixolaris for this assay, but not for human TFPI, was strong evidence that both molecules operate by distinct mechanisms.

[0029] To detect Ixolaris binding to Factor X and Factor Xa, reactants were incubated in equimolar concentrations (20 nM) for 15 minutes at 37° C. followed by PAGE under non-denaturating conditions. Proteins were transferred to PVDF membrane. Experiments were performed using anti-human Factor X polyclonal antibodies. Results indicate complex formation between Ixolaris and Factor X (FIG. 8A) and Factor Xa (FIG. 8B). On the other hand, complex formation between Ixolaris and Factor VIIa was not detected using anti-human Factor VIIa MoAb (FIG. 8C), even when 10 times molar excess Ixolaris was used, indicating that Ixolaris is not a tight-inhibitor of VIIa, in contrast to Factor X and Factor Xa.

[0030] To determine whether the binding of Ixolaris to Factor Xa was accompanied by a change in the esterolytic activity of Factor Xa, inhibitor and chromogenic substrate (S2222) were incubated for 15 minutes at 37° C., followed by addition of Factor Xa (125 pM). Ixolaris, at a concentration similar to the enzyme, instantaneously increased Factor Xa activity (FIG. 9A) indicating that it is a tight-and-fast ligand of Factor Xa, with an ED50 of 159±3.8 pM (FIG. 9B). In contrast, full-length human TFPI behaves as a typical slow-binding inhibitor of Factor Xa (Wesselschmidt, R. et al. 1992 Blood 79:2004-2010) (FIG. 9A). Similar results were obtained with γ-carboxyglutamic acid domainless Factor Xa (des-Gla-Factor Xa), (FIG. 9C) whose proteolytic activity increased 1.98 fold in the presence of Ixolaris (control, 0.4 nM des-Gla-Factor Xa: 1.4±0.12 units of Vmax; 0.4 nM des-Gla-Factor Xa plus 1.6 nM Ixolaris: 2.78±0.1 units of Vmax; triplicate determination). Similar results were obtained for Factor Xa, but not for thrombin (FIG. 9C).

[0031] Because both Factor Xa and Factor X interact with Ixolaris as determined by native PAGE, we aimed to determine the relative affinities of Ixolaris for Factor X and Factor Xa. FIG. 9D shows that Ixolaris (400 pM) increases by ˜40% the amidolytic activity of Factor Xa (640 pM). When Ixolaris (400 pM) was incubated for 15 min with a pre-formed mixture of Factor Xa (640 pM) and increasing concentrations (0-3.2 nM) of DEGR-Factor Xa, or des-Gla-DEGR-Factor Xa, followed by addition of S2222, the Ixolaris-dependent increase of Factor Xa activity was inhibited. Interestingly, this effect was not observed when increasing concentrations of Factor X were used (up to 16 nM). However, when Ixolaris was preincubated with Factor X or DEGR-Factor Xa and S2222, followed by addition of Factor Xa, inhibition of Ixolaris-enhanced increase of Factor Xa amidolytic activity was attained in all cases (inset, triplicate determination). Thus, Ixolaris binds with fast-and-tight kinetics to Factor Xa, whereas it binds to Factor X with lower apparent affinity and/or with slow kinetics, as indicated by the competition experiments with Factor Xa (FIG. 9D).

[0032] TFPI blocks the catalytic activity of Factor VIIa, in a Factor Xa dependent manner (Broze, G. J. Jr. et al. 1988 Blood 71:335-343; Pedersen, A. H. et al. 1990 J Biol Chem 254:16786-16793; Rao, L. V. M., and Rapaport, S. I. 1987 Blood 69:645-651; Broze, G. J. Jr. and Miletich, J. P. 1987 PNAS USA 84:1886-1890; Rapaport, S. I. 1989 Blood 73359-365). In an attempt to determine whether Ixolaris (or Ixolaris Factor X/Xa complex) inhibits Factor VIIa/TF catalytic activity, inhibitor and increasing concentrations of DEGR-Factor Xa (0-4 nM) or DEGR-Factor X (0-4 nM) were incubated with S2288 (1 mM) for 15 minutes, followed by addition of Factor VIIa (1 nM)/TF (1 nM) to start reactions. The rationale for using DEGR-Factor X is based upon experiments showing that serine catalytic site mutated Factor X (FXS195A) has been used as an effective scaffold for NAPc2, a TFPI-like molecule from Ancylostoma caninum (Bergum, P. W. et al. 2001 J Biol Chem 276:10063-10071). FIGS. 10B and 10C shows that no inhibition of the Factor VIIa/TF amidolytic activity was obtained in the presence of Ixolaris alone (up to 266 nM). However, instantaneous inhibition was attained in a dose-dependent manner in the presence of DEGR-Factor Xa (FIG. 10A). When DEGR-Factor X was used as a scaffold, immediate inhibition was observed as well (FIG. 10B). In contrast to DEGR-Factor Xa, however, inhibition of Factor VIIa/TF amidolytic activity by Ixolaris/Factor X was reproducibly and consistently partial, and never total at the highest DEGR-Factor X concentration tested (8 nM). FIG. 10C summarizes the effects of both scaffolds in the amidolytic activity of Factor VIIa/TF, and it also shows that des-Gla-DEGR-Factor Xa did not affect the amidolytic activity of Factor VIIa/TF. It seems plausible to indicate that γ-carboxyglutamic acid is involved with Ixolaris/FX-FVIIa/TF complex formation.

[0033] Interestingly, the partial inhibition of Factor VIIa/TF amidolytic activity after incubation with Ixolaris/Factor X is similar to the pattern described for a Factor VIIa peptide exosite inhibitor selected from naïve peptide libraries displayed on M13 phage (Dennis, M. S. et al. 2000 Nature 404:465-470). This information led us to hypothesize that Ixolaris/Factor X could be interacting with Factor VIIa exosite. To test this hypothesis, Factor VIIa/TF (1 nM/0.2 pM) was incubated for 15 min with buffer, Ixolaris alone (100 pM), Ixolaris/DEGR-Factor X (100 pM), Ixolaris/DEGR-Factor Xa (100 pM) or Ixolaris/DEGR-des-Gla-Factor Xa (100 pM). Subsequently this mixture was added to Factor X (200 nM). FIG. 10D shows that in the presence of buffer, Factor Xa was produced after addition of Factor VIIa/TF to Factor X (control). However, incubation of Ixolaris alone with Factor VIIa/TF resulted in ˜65% inhibition, that was enhanced (>85%) with Ixolaris-DEGR-Factor X or Ixolaris/DEGR-Factor Xa. Ixolaris/DEGR-des-Gla-Factor Xa had little effect in this assay. The data from in FIG. 10D immediately indicated that Ixolaris in the absence of scaffolds inhibits the interactions of Factor VIIa/TF with macromolecular substrates at a site distinct (exosite) from the catalytic site, this interaction being positively modulated by Factor X and Factor Xa, and dependent on γ-carboxyglutamic acid residues.

[0034] Experiments were then performed in an attempt to characterize Ixolaris as a Factor VIIa exosite inhibitor. Factor VIIa/TF catalyzes the activation of Factor IX to Factor IXa. Factor IX activation proceeds throught two consecutive steps. Cleavage of the Arg145-Ala146 peptide bond yields the intermediate heavy-chain fragment, indicative of Factor IXα. Subsequent cleavage of Arg180-Val181 bond releases the 35-aminoacid activation peptide and generates the heavy chain fragment of active Factor IXaβ. FIG. 11A shows that Factor IX was not activated when incubation with Factor VIIa/TF was not allowed to proceed (0 min incubation time, lane 1). However, after 40 min of Factor IX incubation with Factor VIIa/TF, bands corresponding to the heavy chain of Factor IXα, the heavy chain of Factor IXaβ, and the light chain of Factor aβ can be visualized in the NU-PAGE gel (Lane 2). When Ixolaris (0-266 nM) was preincubated with Factor VIIa/TF, a dose-dependent inhibition of Factor IX activation was attained (lanes 3-9). Densitometry of the bands corresponding to heavy chain of Factor IXaβ was performed to quantify the effects of Ixolaris (FIG. 11B). The results are plotted as a function of Ixolaris concentration (0-266 nM) showing a dose-dependent inhibition of Factor IX activation by Factor VIIa/TF (1 nM) (FIG. 11C). By comparison, Ixolaris in the same concentration range (up to 266 nM) did not affect the amidolytic activity of Factor VIIa/TF (1 nM) (FIG. 11C). Accordingly, Ixolaris inhibits Factor VIIa/TF interactions with macromolecules (exosite mediated) but is not an inhibitor of small chromogenic substrates cleavage by Factor VIIa/TF (catalytic site mediated).

[0035] Next we tested the effects of scaffolds for Ixolaris in this assay. FIG. 12A shows that Ixolaris partially inhibits Factor IX activation (lane 3); however, this inhibition was remarkable when Factor VIIa/TF was incubated with Ixolaris/DEGR-FX (lane 5), and Ixolaris/DEGR-Factor Xa (lane 7). At higher concentrations of Ixolaris and Factor X/Xa inhibition was even more pronounced (FIG. 12B). This set of data confirmed that both Factor Xa and Factor X are scaffolds for Ixolaris, increasing its affinity for Factor VIIa/TF. As expected, we could not detect inhibition with Ixolaris/des-Gla-FXa (lane 9) indicating that γ-carboxyglutamic acid has a definite role in Ixolaris/FX(a) interaction with FVIIa/TF. Actually, in the presence of Ixolaris/DEGR-des-Gla-FXa, Ixolaris produced less inhibition in this assay. Band densitometry was performed for quantification of the results presented in FIG. 12A and FIG. 12B, as summarized in FIG. 12C.

[0036] We then attempted to determine the stoichiometry of the interaction between Ixolaris/Factor Xa and Factor VIIa/TF. FIG. 13A shows the progress curves for inhibition of Factor VIIa (1 nM)/TF (0.8 nM) amidolytic activity on S2288 by Ixolaris (3 nM) in the presence of increasing concentrations of DEGR-Factor Xa (0-5 nM). A transformation of the data as Vs/Vo yields an IC50 of 0.41±0.04 nM. Almost complete (>95%) inhibition was observed at Ixolaris/DEGR-FXa concentration of 1 nM (FIG. 13B). This result indicates that Ixolaris, Factor Xa, Factor VIIa and TF react stoichiometrically. The finding that Ixolaris inhibits Factor VIIa-TF activity in a Factor Xa-dependent manner was confirmed by increasing the concentration of Ixolaris (0-5 nM) at one concentration of DEGR-Factor Xa (3 nM).

[0037] In an attempt to study the effects of Ixolaris under relevant physiological conditions, human umbilical vein endothelial cells (HUVEC) were stimulated to express TF after 4-hours incubation with lipopolysaccharide (LPS). Then a mixture containing Factor X (200 nM) and Ixolaris (0-4 nM) previously incubated together for 15 min was added to the cells, followed by immediate addition of Factor VIIa (1 nM). After 30 min, Factor Xa production was detected using chromogenic substrate for Factor Xa. FIG. 14 shows that Ixolaris dose-dependently inhibits Factor Xa production, with an IC50˜500 pM.

[0038] Table 1 shows that Ixolaris is a specific inhibitor for Factor VIIa/TF-induced Factor X activation.

1TABLE 1Specificity of Ixolaris to Factor VIIa/TF-induced Factor Xactivation. Ixolaris (32 nM, final concentration) was preincubated for 15minutes at 37° C. with the enzymes listed below, followed by additionof the appropriate chromogenic substrate. Reactions were followed for 30minutes at 37° C., and the effect of Ixolaris was estimated by setting theinitial velocity obtained in the presence of enzyme alone (withoutinhibitor) as 100%.Enzymes/SubstratesResidual activity (%)VIIa/TF (6.4 pM)/S2288 (1 mM)0Thrombin (125 pM)/S2238 (250 μM) 103 ± 1.56Chymotrypsin (22.4 nM)/S2222 (250 μM)101.5 ± 0.09Factor XIa (58.7 pM)/S2256 (250 μM)89.2 ± 3.1Reptilase (0.3125 BU/mL)/S2238 (250 μM) 98.5 ± 0.52Plasmin (5 mU/mL)/S2251 (250 μM)107.5 ± 0.75Elastase (250 pM)/Substrate (500 μM) 106 ± 8.02Tryptase (0.4 μg/mL)/S2222 (250 μM) 101 ± 0.07

Ixolaris

[0039] The recombinant tick salivary protein of this invention, called Ixolaris, potently inhibits factor VIIa/TF-induced Factor X activation with an IC50 in the pM range. Ixolaris is functionally and structurally distinct from its endogenous counterpart, TFPI (Broze, G. J. et al. 1990 Biochemistry 29:7539-7546; Sprecher, C. A. et al. 1994 PNAS USA 91:3353-3357; Laskowski, M. Jr. and Kato I. 1980 Annu Rev Biochem 49:593-626): although the six cysteines that characterize the first Kunitz domain (Laskowski, M. Jr, and Kato I. 1980 Annu Rev Biochem 49:593-626) of TFPI are conserved in Ixolaris, only four of six cysteines present in the second Kunitz domain of human TFPI are present. Also, whereas the sixth and the first cysteines that, respectively, terminate and initiate the first and second Kunitz domains in human TFPI are separated by 20 amino acids, only 7 amino acids separate the corresponding cysteines in Ixolaris. Additionally, the Kunitz-type domain 2 in Ixolaris is unusual by containing 4 additional amino acids between the fourth and fifth cysteine residues, making this loop longer than most Kunitz-type family members. Also, the presumed P1 reactive-site residue of the first domain in Ixolaris is Glu, whereas Lys occupies this position in TFPI (Broze, G. J. et a. 1990 Biochemistry 29:7539-7546). Finally, Ixolaris has a short and basic carboxy terminus but, unlike TFPI, it has only 14 amino acids where the positively charged amino acids are not organized as a cluster. In human TFPI, this basic carboxy terminus has been consistently shown to increase its anticoagulant activity (Wesselschmidt, R. et al. 1992 Blood 79:2004-2010; Nordfang, O. et al. 1991 Biochemistry 30:10371-10376) and to shorten its half-life (Warshawasky, I. et al. 1995 J Clin Invest 95:1173-1181; Ho, G. et al. 2000 Blood 95:1973-1978). The Ixolaris cDNA also encodes three putative N-linked glycosylation sites, at Asn65, Asn98, and Asn136. Consistent with a calculated mass of 15.7 kDa for the carbohydrate-free protein, we could detect a band of ˜15.5 kDa in the gels loaded with recombinant Ixolaris; however, an intense smear was observed in PAGE of Ixolaris at a molecular weight range of ˜24 kDa. Accordingly, it is likely that these Asn residues are indeed glycosylated, and this is the most abundant form (>95%) of the secreted recombinant molecule.

[0040] TFPI and Ixolaris are unrelated in many functional aspects. Ixolaris is a highly specific inhibitor that, unlike human TFPI, does not inhibit trypsin or chymotrypsin (Petersen, L. C. et al. 1996 Eur J Biochem 235:310-316). Ixolaris increases the amidolytic activity of Factor Xa toward chromogenic substrates and behaves as a fast ligand of Factor Xa, in contrast to TFPI, a typical Factor Xa slow-binding inhibitor (Wesselschmidt, R. et al. 1992 Blood 79:2004-2010). Additionally, Ixolaris binds to des-Gla-Factor Xa and to a tripeptidyl chloromethylketone covalently occupied catalytic site of Factor Xa (DEGR-Factor Xa), two properties not shared by TFPI (Broze, G. J. Jr. et al. 1988 Blood 71:335-343; Hamamoto, T. et al. 1993 J Biol Chem 268:8704-8710). This result indicates that Ixolaris binds at the exosite of Factor Xa and implies that γ-carboxyglutamic acid is not involved in the interaction between enzyme and inhibitor. Remarkably, Ixolaris also binds to Factor X, in addition to Factor Xa, although relative affinities or the kinetics of the interaction (slow vs. fast) may be different as depicted in the competition experiments shown in FIG. 9D (inset). This result may be due to how the exosite is exposed in Factor Xa in comparison to a putative Factor X proexosite (Krishnaswamy, S. and Betz, A. 1997 Biochemistry 36:12080-12086). Interestingly, it has been recently shown that NAPc2, a TFPI-like molecule from Ancylostoma caninum, also binds to Factor X (in addition to Factor Xa). NAPc2 also displays slow association kinetics for interaction with Factor X that is at 5˜10 lower rates than those measured with Factor Xa (Bergum, P. W. et al. 2001 J Biol Chem 276:10063-10071). It has been proposed that the structural features of Factor X requires an induced fit during the association phase of NAPc2 with Factor X (Bergum, P. W. et al. 2001 J Biol Chem 276:10063-10071). We suggest that a similar mechanism may operate for Ixolaris.

[0041] According to the data gathered in FIGS. 10 and 12, it is also clear that both zymogen (DEGR-Factor X) and enzyme (DEGR-Factor Xa) operate as scaffolds for Ixolaris. Because Ixolaris/Factor X only partially attenuates Factor VIIa/TF amidolytic activity it was hypothesized that inhibitor/zymogen complex does not have complete access to the catalytic site of Factor VIIa, or alternatively, it binds to a site distinct (exosite) from the catalytic site. This pattern of inhibition is consistent with Factor VIIa exosite inhibitors recently described in a naïve peptide library displayed on M13 phage (Dennis, M. S. et al. 2000 Nature 404:465-470). These inhibitors block the interactions of Factor VIIa/TF with macromolecular substrates, but only partially attenuate the amidolytic activity of FVIIa/TF. In the experiments described here, Ixolaris alone also prevents Factor IX activation by Factor VIIa/TF (exosite mediator), without affecting Factor VIIa/TF amidolytic (catalytic) activity (S2288) (FIGS. 10C, 11C). This result indicates that Ixolaris interacts with Factor VIIa exosite. Because inhibition is this assays occurs at [I]>>[E], we conclude that Ixolaris is not a tight inhibitor of Factor VIIa/TF; this point is consistent with no detection of complex formation between enzyme and inhibitor as assessed in native PAGE. Importantly, control experiments revealed that this inhibition was not due to trace levels of Factor X or Factor Xa contaminating the Factor IX preparation. Interestingly, TFPI also partly blocks the amidolytic activity of Factor VIIa/TF (Pedersen, A. H. et al. 1990 J Biol Chem 254:16786-16793; Hamamoto, T. et al. 1993 J Biol Chem 268:8704-8710; Iakhiaev, A. et al. 2001 Thromb Haemost 85:458-463), whereas it completely inhibits the activation of Factor IX by Factor VIIa in complex with cell surface TF, in the absence of scaffolds (Hamamoto, T. et al. 1993 J Biol Chem 268:8704-8710). More recently it has been shown that TFPI-Xa complex interacts with both the catalytic site and the macromolecular substrate exosite of Factor VIIa/TF (Iakhiaev, A. et al. 2001 Thromb Haemost 85:458-463). Accordingly, there is a contrast between TFPI, which interacts also with the catalytic site, and Ixolaris, which interacts solely with the exosite. In a recept paper, Baugh et al. (Baugh, R. J. et al. 2000 J Biol Chem 275:28826-28833) concluded that exosite-dependent interactions play a predominant role in determining the affinity for protein substrates and kinetics of interaction involving at least two enzymes of the blood coagulation cascade. Clearly, this point has important implications for the targeting of enzyme exosites by a natural inhibitor like Ixolaris that will effectively disrupt coagulation enzyme complexes.

[0042] The anionic Gla-domain of Factor X is known to play a crucial role in the interaction of Factor Xa with pro-coagulant membrane surface, and directly with Factor VIIa/TF complex (Ruf, W. et al. 1999 Biochemistry 38:1957-1966). To demonstrate the importance of this domain for the activity of scaffolds we used DEGR-des-Gla-Factor Xa, a Factor X derivative lacking the Gla-domain. The binding of des-Gla-FXa to Ixolaris was similar to Factor Xa (FIGS. 9C, 9D), demonstrating that this domain is not crucial for inhibitor binding to zymogen/enzyme. However, DEGR-des-Gla-Factor Xa was a completely ineffective scaffold for Ixolaris in the inhibition of Factor VIIa/TF-mediated FIX activation and amidolytic activity. Actually, des-Gla-Factor Xa attenuated the inhibition of Factor VIIa/TF activity detected in the presence of Ixolaris alone (FIG. 10D and FIG. 12C). Accordingly, it seems that des-Gla-Factor Xa tight-binding to Ixolaris prevents its interaction with Factor VIIa/TF, an interaction that is characteristically not tight. In other words, in the absence of Gla-Domain, des-Gla-Factor Xa and Factor VIIa/TF compete for Ixolaris.

[0043] Regarding the interaction of Ixolaris with Factor Xa and Ixolaris/Factor X(a) with VIIa/TF, they are kinetically fast. In fact, instantaneous increase of chromogenic substrate hydrolysis was attained when Factor Xa was added to a mixture containing Ixolaris and S2222 (FIG. 9A). Likewise, Factor VIIa/TF amidolytic activity was immediately blocked when the enzyme was added to a mixture containing Ixolaris/Factor Xa and S2288 (FIG. 10A), or Ixolaris/Factor X and S2288 (FIG. 10B). This finding is also consistent with the data presented in FIG. 7B, where the production of Factor Xa was blocked without delay when Factor VIIa/TF was added to a mixture containing Ixolaris/Factor X and S2222.

[0044] Our results also show that Ixolaris blocks the catalytic activity of Factor VIIa/TF in the presence of increasing concentrations of DEGR-Factor Xa, and maximal inhibition was attained with a 1:1 stoichiometry, indicating that Ixolaris/Factor Xa behaves as a tight inhibitor of Factor VIIa/TF. Due to the tight interaction between Ixolaris and Factor X detected by native PAGE, we suggest that Ixolaris forms a stable complex with physiologic concentration of Factor X. This finding seems relevant since Ixolaris/Factor X may inhibit Factor VIIa/TF before Factor Xa production. Similar conclusions have been obtained for NAPc2 that also shares with Ixolaris dependency on Factor X and Factor Xa as scaffolds (Bergum, P. W. et al. 2001 J Biol Chem 276:10063-10071; Stanssens, P. et al. 1996 PNAS USA 93:2149-2154). However, both molecules differ from each other in structural and kinetic aspects. NAPc2 is a protein of 84 amino acids with a distinct pattern of cysteines when compared to Ixolaris. Also, we could not identify an arginine between two cysteines that have been characterized in NAPc2 as the cleavage site for Factor Xa. NAPc2 partially blocks Factor Xa proteolytic activity toward chromogenic substrates, whereas Ixolaris enhances it. Moreover, NAPc2 at high concentrations, but not Ixolaris, blocks the amidolytic activity of Factor VIIa/TF. In addition, Ixolaris/DEGR-FXa behaves as a fast inhibitor of Factor VIIa/TF, whereas NAPc2/DEGR-FXa is a slow inhibitor of Factor VIIa/TF (Bergum, P. W. et al. 2001 J Biol Chem 276:10063-10071; Stanssens, P. et al. 1996 PNAS USA 93:2149-2154).

[0045] Despite clear structural and functional differences among Ixolaris, NAPc2, and human TFPI, these inhibitors may affect Factor Xa production in an equivalent manner through binding to Factor Xa (or Factor X) preceding formation of a quaternary complex consisting of inhibitor/Factor X(a)/Factor VIIa/TF (Sprecher, C. A. et al. 1994 PNAS USA 91:3353-3357). However, we cannot predict at present whether the first and second Kunitz domains of Ixolaris bind respectively to Factor Xa and Factor VIIa, as described for human TFPI (Sprecher, C. A. et al. 1994 PNAS USA 91:3353-3357). It also remains to be determined how the presence of scaffolds induces Ixolaris to block the catalytic activity of Factor VIIa/TF. Finally, the finding that Ixolaris blocks Factor Xa generation by endothelial cells expressing TF indicates that Ixolaris exerts anticoagulant effect under relevant physiological conditions.

[0046] The proposed inhibitory mechanism of Ixolaris is schematically shown below. Ixolaris binds to Factor X (step 1) or Factor Xa (step 2). Subsequently, this interaction is followed by stable complex formation with Factor VIIa/TF (step 3 or 3′). In vitro, Ixolaris also binds to Factor VIIa/TF, in the absence of scaffolds (step 4), the physiological relevance of this interaction being currently unknown since Ixolaris should circulate bound to Factor X in the blood.

[0047] Novel molecules that block initiation of blood coagulation, such as Ixolaris, are envisioned as being useful as inhibitors to prevent or ameliorate a number of pathologic conditions leading to cardiovascular diseases provoked or amplified by abnormal expression of TFPI (Weitz, J. I. in: Hematology 2000 City, ST, The American Society of Hematology Education (Program Book) p 266-268; Bajaj, M. S. and Bajaj S. P. 1997 Thromb Haemost 78:471-477; Brown, D. M. et al. 1996 Arch Surg 131:1086-1090; Warr T. A. et al. 1990 Blood 75:1481-1489; Han, X. et al. 1999 Arterioscler Thromb Vasc Biol 19:2563-2567; Blomberg, M. E. and Cappello, M. 1999 Cancer J 5:132-138; Jonge, E. et al. 1999 Blood 95:1124-1129). More recently, NAPc2 was shown to be effective in preventing deep-venous thrombosis in patients undergoing total knee replacement surgery (Lee, A. et al. 2000 Blood 96:491a). Given the finding that Ixolaris is a fast ligand of Factor Xa (indicating rapid inhibition) and that it has a short carboxy terminus (suggesting less cell surface binding and slow clearance in vivo) (Warshawasky, I. et al. 1995 J Clin Invest 95:1173-1181; Ho, G. et al. 2000 Blood 95:1973-1978; Petersen, L. C. et al. 1996 Eur J Biochem 235:310-316) and the recent studies suggesting that agents targeting Factor VIIa/TF (eg, VIIai, anti-TF antibodies, TFPI) may induce less bleeding than agents that target coagulation at later stages (Jeske, W. et al. 1996 Sem Thromb Hemost 22:213-219; Himber, J. et al. 1997 Thromb Haemost 78:1142-1149; Harker, L. A. et al. 1996 Haemostasis 26:76-82), Ixolaris is envisioned as being an alternative to conventional anticoagulants such as heparin in a number of clinical conditions. Finally, because Ixolaris presumably participates in the feeding process of the tick, it is envisioned as being useful, together with other molecules such as Ixodes anticomplement (Isac) (Valenzuela et al. 2000 J. Biol. Chem. 275:18717-23), as a target for a vaccine (Thanassi and Schoen 2000 Ann. Intern. Med. 132:661-668) to prevent Lyme disease.

[0048] Definitions

[0049] The term “isolated” requires that a material be removed from its original environment (e.g., the natural environment if it is naturally occurring). For example, a naturally occurring polynucleotide or polypeptide present in a living cell is not isolated, but the same polynucleotide or polypeptide, separated from some or all of the coexisting materials in the natural system, is isolated.

[0050] The term “purified” does not require absolute purity; rather it is intended as a relative definition, with reference to the purity of the material in its natural state. Purification of natural material to at least one order of magnitude, preferably two or three magnitudes, and more preferably four or five orders of magnitude is expressly contemplated.

[0051] The term “enriched” means that the concentration of the material is at least about 2, 5, 10, 100, or 1000 times its natural concentration (for example), advantageously 0.01% by weight. Enriched preparations of about 0.5%, 1%, 5%, 10%, and 20% by weight are also contemplated.

[0052] The Ixolaris Gene

[0053] The cDNA sequence (SEQ. ID. NO. 470) and deduced amino acid sequence (SEQ. ID. No. 471) of Ixolaris are shown in FIG. 3. The signal sequence extends from amino acid residue 1 to 25. The mature protein contains 140 amino acids, including 10 cysteines (SEQ ID NO: 138).

[0054] The Ixolaris nucleotide sequences of the invention include: (a) the cDNA sequence shown in FIG. 3; (b) nucleotide sequence that encodes the amino acid sequence shown in FIG. 3, its functional domains, truncations thereof, as well as substitutions, insertions, and deletions (including fusion proteins) thereof; (c) any nucleotide sequence that hybridizes to the complement of the cDNA sequence shown in FIG. 3 under highly stringent conditions, e.g., hybridization to filter-bound DNA in 0.5 M NaHPO4, 7% sodium dodecyl sulfate (SDS), 1 mM EDTA at 65° C., and washing in 0.1 times SSC/0.1% SDS at 68° C. (Ausubel F. M. et al. eds. 1989 Current Protocols in Molecular Biology, Vol. I, Green Publishing Associates, Inc., and John Wiley & sons, Inc., New York, at p. 2.10.3) and encodes a functionally equivalent gene product; and (d) any nucleotide sequence that hybridizes to the complement of the cDNA sequence shown in FIG. 3 under less stringent conditions, such as moderately stringent conditions, e.g., washing in 0.2 times SSC/0.1% SDS at 42° C. (Ausubel et al. 1989, supra), yet which still encodes a functionally equivalent gene product. Functional equivalents of Ixolaris include those naturally occurring and engineered, as judged by any of a number of criteria, including, but not limited to, the binding affinity for Factor Xa, X, or VIIa, the resulting biological effect of factor Xa, X, or VIIa binding, anticoagulant activity, generation of antibodies that specifically bind Ixolaris, and identification of compounds that can be used to modulate coagulation function.

[0055] The invention also includes nucleic acid molecules, preferably DNA molecules, that hybridize to, and are therefore the complements of, the nucleotide sequences (a) through (d), in the preceding paragraph.

[0056] In addition to the Ixolaris nucleotide sequences described above, full or partial length Ixolaris cDNA present in the same species and/or homologs of the Ixolaris gene present in other species can be identified and readily isolated, without undue experimentation, by molecular biological techniques well known in the art. For example, expression libraries of cDNAs synthesized from salivary gland mRNA derived from the organism of interest can be screened using labeled Factor Xa, X, or VIIa derived from that species, e.g., a Factor Xa, X, or VIIa fusion protein. Alternatively, such cDNA libraries, or genomic DNA libraries derived from the organism of interest can be screened by hybridization using the nucleotides described herein as hybridization or amplification probes. Furthermore, genes at other genetic loci within the genome that encode proteins which have extensive homology to one or more domains of the Ixolaris gene product can also be identified via similar techniques. In the case of cDNA libraries, such screening techniques can identify clones derived from alternatively spliced transcripts in the same or different species.

[0057] Screening can be by filter hybridization, using duplicate filters. The labeled probe can contain at least 15-30 base pairs of the Ixolaris nucleotide sequence, as shown in FIG. 3. The hybridization washing conditions used should be of a lower stringency when the cDNA library is derived from an organism different from the type of organism from which the labeled sequence was derived. With respect to the cloning of a human Ixolaris homolog, using tick Ixolaris probes, for example, hybridization can, for example, be performed at 65° C. overnight in Church's buffer (7% SDS, 250 mM NaHPO4, 2 μM EDTA, 1% BSA). Washes can be done with 2 times SSC, 0.1% SDS at 65° C. and then at 0.1 times SSC, 0.1% SDS at 65° C.

[0058] Low stringency conditions are well known to those of skill in the art, and will vary predictably depending on the specific organisms from which the library and the labeled sequences are derived. For guidance regarding these and other hybridization conditions see, for example, Sambrook et al. 1989 Molecular Cloning, A Laboratory Manual, Cold Springs Harbor Press, N.Y.; Ausubel et al. 1989 Current Protocols in Molecular Biology, Green Publishing Associates and Wiley Interscience, N.Y.

[0059] Alternatively, the labeled Ixolaris nucleotide probe may be used to screen a genomic library derived from the organism of interest, again, using appropriately stringent conditions.

[0060] Further, a full or partial length Ixolaris cDNA present in the same species and/or homologs of the Ixolaris gene present in other species may be isolated from nucleic acid of the organism of interest by performing PCR using two degenerate oligonucleotide primer pools designed on the basis of amino acid sequences within the Ixolaris gene product disclosed herein. The template for the reaction may be cDNA obtained by reverse transcription of mRNA prepared from, for example, cell lines or tissue, such as salivary gland, known or suspected to express an Ixolaris gene allele.

[0061] The PCR product may be subcloned and sequenced to ensure that the amplified sequences represent the sequences of an Ixolaris gene. The PCR fragment may then be used to isolate a full length cDNA clone by a variety of methods. For example, the amplified fragment may be labeled and used to screen a cDNA library, such as a bacteriophage cDNA library. Alternatively, the labeled fragment may be used to isolate genomic clones via the screening of a genomic library.

[0062] PCR technology may also be utilized to isolate full length cDNA sequences. For example, RNA may be isolated, following standard procedures, from an appropriate cellular or tissue source (i.e., one known, or suspected, to express the Ixolaris gene, such as, for example, salivary gland). A reverse transcription reaction may be performed on the RNA using an oligonucleotide primer specific for the most 5′ end of the amplified fragment for the priming of first strand synthesis. The resulting RNA/DNA hybrid may then be “tailed” with guanines using a standard terminal transferase reaction, the hybrid may be digested with RNAase H, and second strand synthesis may then be primed with a poly-C primer. Thus, cDNA sequences upstream of the amplified fragment may easily be isolated. For a review of cloning strategies which may be used, see e.g., Sambrook et al. 1989, supra.

[0063] In addition to nucleotide sequences encoding the full-length Ixolaris protein 140-mer, other embodiments of the invention may include nucleotide sequences encoding truncations of the Ixolaris protein which exhibit binding affinity for Factor Xa, X, or VIIa, the resulting biological effect of Factor Xa, X, or VIIa binding, anticoagulant activity, generation of antibodies that specifically bind Ixolaris, or identification of compounds that can be used to modulate coagulation function. Truncations of Ixolaris peptides may comprise peptides of between 3 and 140 amino acid residues (i.e., peptides ranging in size from a tripeptide to a 140-mer polypeptide), as shown in Appendix A (Table I) and Appendix B (Table II). Peptide sequences in these tables are listed from amino (left) to carboxy (right) terminus. “X” may represent an amino group (—NH2) and “Z” may represent a carboxyl (—COOH) group. Alternatively, “X” may represent a hydrophobic group, including but not limited to carbobenzyl, dansyl, or T-butoxycarbonyl; an acetyl group; a 9-fluorenylmethoxy-carbonyl (FMOC) group; or a covalently attached macromolecular group, including but not limited to a lipid-fatty acid conjugate, polyethylene glycol, carbohydrate or peptide group. Further, “Z” may represent an amino group; a T-butoxycarbonyl group; or a covalently attached macromolecular group, including but not limited to a lipid-fatty acid conjugate, polyethylene glycol, carbohydrate or peptide group. A preferred “X” or “Z” macromolecular group is a peptide group.

[0064] The invention encompasses nucleotide sequences that encode not only Ixolaris but also its functional domains, besides truncations thereof, as well as substitutions, insertions, and deletions (including fusion proteins) thereof. These include, but are not limited to nucleotide sequences encoding a Kunitz domain of the Ixolaris protein. It is believed that a Kunitz domain is responsible for the observed anticoagulant activity. Certain representative Kunitz domains include the amino acid sequences depicted in FIG. 3, particularly the sequences between the cysteines designated as cysteine 1 and cysteine 10; also between amino acids 18 and 68 (first Kunitz domain) and its amino and carboxy truncations:

2CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:276) LDPEQVTCESQEGTHASYNRKTGQCEEQKQTECGGGENHFETLLKCNESC(SEQ ID NO:277) DPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:278) PEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:279) EQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:280) QVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:281) VTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:282) TCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:283) CESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:284) ESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:285) SQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:286) QEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:287) EGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:288) GTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:289) THASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:290) HASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:291) ASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:292) SYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:293) YNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:294) NRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:295) RKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:296) KTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:297) TGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:298) GQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:299) QCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:300) CEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:301) EEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:302) EQKGTECGGGENHFETLLKCNESC(SEQ ID NO:303) QKGTECGGGENHFETLLKCNESC(SEQ ID NO:304) KGTECGGGENHFETLLKCNESC(SEQ ID NO:305) GTECGGGENHFETLLKCNESC(SEQ ID NO:306) TECGGGENHFETLLKCNESC(SEQ ID NO:307) ECGGGENHFETLLKCNESC(SEQ ID NO:308) CGGGENHFETLLKCNESC(SEQ ID NO:309) GGGENHFETLLKCNESC(SEQ ID NO:310) GGENHFETLLKCNESC(SEQ ID NO:311) GENHFETLLKCNESC(SEQ ID NO:312) ENHFETLLKCNESC(SEQ ID NO:313) NHFETLLKCNESC(SEQ ID NO:314) HFETLLKCNESC(SEQ ID NO:315) FETLLKCNESC(SEQ ID NO:316) ETLLKCNESC(SEQ ID NO:317) TLLKCNESC(SEQ ID NO:318) LLKCNESC(SEQ ID NO:319) LKCNESC(SEQ ID NO:320) KCNESC(SEQ ID NO:321) CNESC(SEQ ID NO:322) NESC(SEQ ID NO:323) ESC(SEQ ID NO:324)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNESC(SEQ ID NO:276)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCNES(SEQ ID NO:325)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTEGGGGENHFETLLKCNE(SEQ ID NO:326)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKCN(SEQ ID NO:327)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLKC(SEQ ID NO:328)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLLK(SEQ ID NO:329)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETLL(SEQ ID NO:330)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFETL(SEQ ID NO:331)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFET(SEQ ID NO:332)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHFE(SEQ ID NO:333)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENHF(SEQ ID NO:334)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGENH(SEQ ID NO:335)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGEN(SEQ ID NO:336)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGGE(SEQ ID NO:337)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGGG(SEQ ID NO:338)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECGG(SEQ ID NO:339)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTECG(SEQ ID NO:340)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTEC(SEQ ID NO:341)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGTE(SEQ ID NO:342)CLDPEQVTCESQEGTHASYNRKTGQCEEQKGT(SEQ ID NO:343)CLDPEQVTCESQEGTHASYNRKTGQCEEQKG(SEQ ID NO:344)CLDPEQVTCESQEGTHASYNRKTGQCEEQK(SEQ ID NO:345)CLDPEQVTCESQEGTHASYNRKTGQCEEQ(SEQ ID NO:346)CLDPEQVTCESQEGTHASYNRKTGQCEE(SEQ ID NO:347)CLDPEQVTCESQEGTHASYNRKTGQCE(SEQ ID NO:348)CLDPEQVTCESQEGTHASYNRKTGQC(SEQ ID NO:349)CLDPEQVTCESQEGTHASYNRKTGQ(SEQ ID NO:350)CLDPEQVTCESQEGTHASYNRKTG(SEQ ID NO:351)CLDPEQVTCESQEGTHASYNRKT(SEQ ID NO:352)CLDPEQVTCESQEGTHASYNRK(SEQ ID NO:353)CLDPEQVTCESQEGTHASYNR(SEQ ID NO:354)CLDPEQVTCESQEGTHASYN(SEQ ID NO:355)CLDPEQVTCESQEGTHASY(SEQ ID NO:356)CLDPEQVTCESQEGTHAS(SEQ ID NO:357)CLDPEQVTCESQEGTHA(SEQ ID NO:358)CLDPEQVTCESQEGTH(SEQ ID NO:359)CLDPEQVTCESQEGT(SEQ ID NO:360)CLDPEQVTCESQEG(SEQ ID NO:361)CLDPEQVTCESQE(SEQ ID NO:362)CLDPEQVTCESQ(SEQ ID NO:363)CLDPEQVTCES(SEQ ID NO:364)CLDPEQVTCE(SEQ ID NO:365)CLDPEQVTC(SEQ ID NO:366)CLDPEQVT(SEQ ID NO:367)CLDPEQV(SEQ ID NO:368)CLDPEQ(SEQ ID NO:369)CLDPE(SEQ ID NO:370)CLDP(SEQ ID NO:371)CLD(SEQ ID NO:372)

[0065] as well as between amino acids 76 and 126 (second Kunitz domain) and its amino and carboxy truncations:

3CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:373) SLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:374) LEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:375) EVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:376) VDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:377) DYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNEESEEECKETC(SEQ ID NO:378) YGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:379) GVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:380) VGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:381) GRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:382) RANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:383) ANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:384) NIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:385) IPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:386) PRWYYDTNNATCEMFTYGGITGNKNNEESEEECKETC(SEQ ID NO:387) RWYYDTNNATCEMETYGGITGNKNNFESEEECKETC(SEQ ID NO:388) WYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:389) YYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:390) YDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:391) DTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:392) TNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:393) NNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:394) NATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:395) ATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:396) TCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:397) CEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:398) EMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:399) MFTYGGITGNKNNFESEEECKETC(SEQ ID NO:400) FTYGGITGNKNNFESEEECKETC(SEQ ID NO:401) TYGGITGNKNNFESEEECKETC(SEQ ID NO:402) YGGITGNKNNFESEEECKETC(SEQ ID NO:403) GGITGNKNNFESEEECKETC(SEQ ID NO:404) GITGNKNNFESEEECKETC(SEQ ID NO:405) ITGNKNNFESEEECKETC(SEQ ID NO:406) TGNKNNFESEEECKETC(SEQ ID NO:407) GNKNNFESEEECKETC(SEQ ID NO:408) NKNNFESEEECKETC(SEQ ID NO:409) KNNFESEEECKETC(SEQ ID NO:410) NNFESEEECKETC(SEQ ID NO:411) NFESEEECKETC(SEQ ID NO:412) FESEEECKETC(SEQ ID NO:413) ESEEECKETC(SEQ ID NO:414) SEEECKETC(SEQ ID NO:415) EEECKETC(SEQ ID NO:416) EECKETC(SEQ ID NO:417) ECKETC(SEQ ID NO:418) CKETC(SEQ ID NO:419) KETC(SEQ ID NO:420) ETC(SEQ ID NO:421)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKETC(SEQ ID NO:373)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKET(SEQ ID NO:422)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECKE(SEQ ID NO:423)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEECK(SEQ ID NO:424)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEEC(SEQ ID NO:425)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEEE(SEQ ID NO:426)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESEE(SEQ ID NO:427)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFESE(SEQ ID NO:428)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGMKNNFES(SEQ ID NO:429)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNFE(SEQ ID NO:430)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNNF(SEQ ID NO:431)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKNN(SEQ ID NO:432)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNKN(SEQ ID NO:433)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGNK(SEQ ID NO:434)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITGN(SEQ ID NO:435)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGITG(SEQ ID NO:436)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGIT(SEQ ID NO:437)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGGI(SEQ ID NO:438)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYGG(SEQ ID NO:439)CSLEVDYGVGRANIPRWYYDTNNATCEMFTYG(SEQ ID NO:440)CSLEVDYGVGRANIPRWYYDTNNATCEMFTY(SEQ ID NO:441)CSLEVDYGVGRANIPRWYYDTNNATCEMFT(SEQ ID NO:442)CSLEVDYGVGRANIPRWYYDTNNATCEMF(SEQ ID NO:443)CSLEVDYGVGRANIPRWYYDTNNATCEM(SEQ ID NO:444)CSLEVDYGVGRANIPRWYYDTNNATCE(SEQ ID NO:445)CSLEVDYGVGRANIPRWYYDTNNATC(SEQ ID NO:446)CSLEVDYGVGRANIPRWYYDTNNAT(SEQ ID NO:447)CSLEVDYGVGRANIPRWYYDTNNA(SEQ ID NO:448)CSLEVDYGVGRANIPRWYYDTNN(SEQ ID NO:449)CSLEVDYGVGRANIPRWYYDTN(SEQ ID NO:450)CSLEVDYGVGRANIPRWYYDT(SEQ ID NO:451)CSLEVDYGVGRANIPRWYYD(SEQ ID NO:452)CSLEVDYGVGRANIPRWYY(SEQ ID NO:453)CSLEVDYGVGRANIPRWY(SEQ ID NO:454)CSLEVDYGVGRANIPRW(SEQ ID NO:455)CSLEVDYGVGRANIPR(SEQ ID NO:456)CSLEVDYGVGRANIP(SEQ ID NO:457)CSLEVDYGVGRANI(SEQ ID NO:458)CSLEVDYGVGRAN(SEQ ID NO:459)CSLEVDYGVGRA(SEQ ID NO:460)CSLEVDYGVGR(SEQ ID NO:461)CSLEVDYGVG(SEQ ID NO:462)CSLEVDYGV(SEQ ID NO:463)CSLEVDYG(SEQ ID NO:464)CSLEVDY(SEQ ID NO:465)CSLEVD(SEQ ID NO:466)CSLEV(SEQ ID NO:467)CSLE(SEQ ID NO:468)CSL(SEQ ID NO:469)

[0066] Amino acid substitutions may be of a conserved or non-conserved nature. Conserved amino acid substitutions consist of replacing one or more amino acids of the Ixolaris or Ixolaris-related sequence with amino acids of similar charge, size, and/or hydrophobicity characteristics, such as, for example, a glutamic acid (E) to aspartic acid (D) amino acid substitution. Non-conserved substitutions consist of replacing one or more amino acids of the Ixolaris or Ixolaris-related sequence with amino acids possessing dissimilar charge, size, and/or hydrophobicity characteristics, such as, for example, a glutamic acid (E) to valine (V) substitution. For example, nonpolar (hydrophobic) amino acids include alanine, leucine, isoleucine, valine, proline, phenylalanine, tryptophan, and methionine; polar neutral amino acids include glycine, serine, threonine, cysteine, tyrosine, asparagine, and glutamine; positively charged (basic) amino acids include arginine, lysine, and histidine; and negatively charged (acidic) amino acids include aspartic acid and glutamic acid. One or more such substitutions may be introduced into the Ixolaris or Ixolaris-related sequence, as long as such substitutions result in variants which exhibit binding affinity for Factor Xa, X, or VIIa, the resulting biological effect of Factor Xa, X, or VIIa binding, anticoagulant activity, generation of antibodies that specifically bind Ixolaris, or identification of compounds that can be used to modulate coagulation function.

[0067] Amino acid insertions may consist of single amino acid residues or stretches of residues. The insertions may be made at the carboxy or amino terminal end of the Ixolaris or Ixolaris-related sequence, as well as at a position internal to the sequence. Such insertions made at either the carboxy or amino terminus of the sequence of interest may be of a broader size range. One or more such insertions may be introduced into the Ixolaris or Ixolaris-related sequence, as long as such insertions result in variants which exhibit binding affinity for Factor Xa, X, or VIIa, the resulting biological effect of Factor Xa, X, or VIIa binding, anticoagulant activity, generation of antibodies that specifically bind Ixolaris, or identification of compounds that can be used to modulate coagulation function.

[0068] Deletions of Ixolaris or Ixolaris-related sequences are also within the scope of the invention. Such deletions consist of the removal of one or more amino acids from the Ixolaris or Ixolaris-related sequence. Such deletions may involve a single contiguous or greater than one discrete portion of the original sequences. One or more such deletions may be introduced into the Ixolaris or Ixolaris-related sequence, as long as such deletions result in variants which exhibit binding affinity for Factor Xa, X, or VIIa, the resulting biological effect of Factor Xa, X, or VIIa binding, anticoagulant activity, generation of antibodies that specifically bind Ixolaris, or identification of compounds that can be used to modulate coagulation function.

[0069] The invention also encompasses (a) DNA vectors that contain any of the foregoing Ixolaris or Ixolaris-related coding sequences and/or their complements; (b) DNA expression vectors that contain any of the foregoing Ixolaris or Ixolaris-related coding sequences operatively associated with a regulatory element that directs the expression of the coding sequences; and (c) genetically engineered host cells that contain any of the foregoing Ixolaris or Ixolaris-related coding sequences operatively associated with a regulatory element that directs the expression of the coding sequences in the host cell. As used herein, regulatory elements include but are not limited to inducible and non-inducible promoters, enhancers, operators and other elements known to those skilled in the art that drive and regulate expression. Such regulatory elements include but are not limited to the cytomegalovirus hCMV immediate early gene, the early or late promoters of SV40 adenovirus, the lac system, the trp system, the TAC system, the TRC system, the major operator and promoter regions of phage A, the control regions of fd coat protein, the promoter for 3-phosphoglycerate kinase, the promoters of acid phosphatase, and the promoters of the yeast alpha-mating factors.

[0070] Ixolaris Proteins, Polypeptides and Peptides

[0071] The Ixolaris protein, its functional domains, truncations thereof, as well as substitutions, insertions, and deletions (including fusion proteins) thereof can be prepared for a number of uses, including, but not limited to, binding Factor Xa, X, or VIIa, the resulting biological effect of Factor Xa, X, or VIIa binding, anticoagulant activity, generation of antibodies that specifically bind Ixolaris, and identification of compounds that can be used to modulate coagulation function.

[0072] The amino acid sequences of the invention include the amino acid sequence shown in FIG. 3 (SEQ. ID. No: 471). Further, Ixolaris and Ixolaris-related amino acid sequences are encompassed by the invention, including mature Ixolaris protein, its functional domains, truncations thereof, as well as substitutions, insertions, and deletions thereof. In fact, any Ixolaris or Ixolaris-related protein, polypeptide or peptide encoded by the Ixolaris or Ixolaris-related nucleotide sequences described in the section above are within the scope of the invention.

[0073] The preferred isolated Ixolaris and Ixolaris-related amino acid sequences of the present invention may be isolated and purified from natural sources. Preferred as natural sources are ticks; suitable ticks include Ixodes scapularis, Ixodes ricinus, and Ornithodorus moubatta. Especially preferred as a natural source is Ixodes scapularis.

[0074] The preferred amino acid sequences of the present invention are isolated from their natural source by methods known in the biochemical arts. These methods include preparing a soluble extract and enriching the extract using chromatographic methods on different solid support matrices. An example of a preferred method of purification of an isolated protein of the present invention would include that as disclosed in the Example.

[0075] The preferred isolated Ixolaris and Ixolaris-related amino acid sequences of the present invention may be synthesized by standard methods known in the chemical arts.

[0076] The isolated amino acid sequences of the present invention may be prepared using solid-phase synthesis, such as that described by Merrifield, 1964 J Amer Chem Soc 85:2149 or other equivalent methods known in the chemical arts, such as the method described by Houghten 1985 PNAS USA 82:5132 (1985).

[0077] Alternatively, the preferred isolated Ixolaris and Ixolaris-related amino acid sequences of the present invention may be made by recombinant DNA methods taught herein and well known in the biological arts (Sambrook et al. 1989 Molecular Cloning, A Laboratory Manual, Cold Springs Harbor Press, N.Y.; Ausubel et al. 1989 Current Protocols in Molecular Biology, Green Publishing Associates and Wiley Interscience, N.Y.). Such methods can be used to construct expression vectors containing the cDNA and other nucleotide sequences described in the section above and appropriate transcriptional and translational control signals. These methods include, for example, in vitro recombinant DNA techniques, synthetic techniques, and in vivo genetic recombination.

[0078] A variety of host-expression vector systems may be utilized to express the cDNA and other nucleotide sequences of the invention. The expression systems that may be used for purposes of the invention include but are not limited to microorganisms such as bacteria (e.g., E. coli, B. subtilis) transformed with recombinant bacteriophage DNA, plasmid DNA or cosmid DNA expression vectors containing Ixolaris and Ixolaris-related nucleotide sequences; yeast (e.g., Saccharomyces, Pichia) transformed with recombinant yeast expression vectors containing Ixolaris and Ixolaris-related nucleotide sequences; insect cell systems infected with recombinant virus expression vectors (e.g., baculovirus) containing Ixolaris and Ixolaris-related nucleotide sequences; plant cell systems infected with recombinant virus expression vectors (e.g., cauliflower mosaic virus, CaMV; tobacco mosaic virus, TMV) or transformed with recombinant plasmid expression vectors (e.g., Ti plasmid) containing Ixolaris and Ixolaris-related nucleotide sequences; or mammalian cell systems (e.g., COS, CHO, BHK, 293, 3T3) harboring recombinant expression constructs containing promoters derived from the genome of mammalian cells (e.g., metallothionein promoter) or from mammalian viruses (e.g., the adenovirus late promoter; the vaccinia virus 7.5 K promoter).

[0079] In bacterial systems, a number of expression vectors may be advantageously selected depending upon the use intended for the Ixolaris and Ixolaris-related gene product being expressed. For example, when a large quantity of such a protein is to be produced, for the generation of pharmaceutical compositions of Ixolaris and Ixolaris-related amino acid sequences or for raising antibodies that specifically bind to the Ixolaris and Ixolaris-related amino acid sequences, for example, vectors which direct the expression of high levels of fusion protein products that are readily purified may be desirable. Such vectors include, but are not limited, to the E. coli expression vector pUR278 (Ruther et al. 1983 EMBO J 2:1791), in which the Ixolaris and Ixolaris-related coding sequence may be ligated individually into the vector in frame with the lacZ coding region so that a fusion protein is produced; pIN vectors (Inouye & Inouye 1985 Nucleic Acids Res 13:3101-3109; Van Heeke & Schuster 1989 J Biol Chem 264:5503-5509) and the like. pGEX vectors may also be used to express foreign sequences as fusion proteins with glutathione S-transferase (GST). In general, such fusion proteins are soluble and can easily be purified from lysed cells by adsorption to glutathione-agarose beads followed by elution in the presence of free glutathione. The pGEX vectors are designed to include protease cleavage sites so that the cloned target gene product can be released from the GST moiety.

[0080] In an insect system, Autographa californica nuclear polyhidrosis virus (AcNPV) is used as a vector to express foreign genes. The virus grows in Spodoptera frugiperda cells. The Ixolaris and Ixolaris-related gene coding sequence may be cloned individually into non-essential regions (for example the polyhedrin gene) of the virus and placed under control of an AcNPV promoter (for example the polyhedrin promoter). Successful insertion of Ixolaris and Ixolaris-related gene coding sequence will result in inactivation of the polyhedrin gene and production of non-occluded recombinant virus, (i.e., virus lacking the proteinaceous coat coded for by the polyhedrin gene). These recombinant viruses are then used to infect Spodoptera frugiperda cells in which the inserted gene is expressed. (E.g., see Smith et al. 1983 J Virol 46:584; Smith, U.S. Pat. No. 4,215,051).

[0081] In mammalian host cells, a number of viral-based expression systems may be utilized. In cases where an adenovirus is used as an expression vector, the Ixolaris and Ixolaris-related nucleotide sequence of interest may be ligated to an adenovirus transcription/translation control complex, e.g., the late promoter and tripartite leader sequence. This chimeric gene may then be inserted in the adenovirus genome by in vitro or in vivo recombination. Insertion in a non-essential region of the viral genome (e.g., region E1or E3) will result in a recombinant virus that is viable and capable of expressing the Ixolaris and Ixolaris-related gene product in infected hosts (e.g., see Logan & Shenk 1984 PNAS USA 81:3655-3659). Specific initiation signals may also be required for efficient translation of inserted Ixolaris and Ixolaris-related nucleotide sequences. These signals include the ATG initiation codon and adjacent sequences. In cases where an entire Ixolaris gene or cDNA, including its own initiation codon and adjacent sequences, is inserted into the appropriate expression vector, no additional translational control signals may be needed. However, in cases where only a portion of the Ixolaris coding sequence is inserted, exogenous translational control signals, including, perhaps, the ATG initiation codon, must be provided. Furthermore, the initiation codon must be in phase with the reading frame of the desired coding sequence to ensure translation of the entire insert. These exogenous translational control signals and initiation codons can be of a variety of origins, both natural and synthetic. The efficiency of expression may be enhanced by the inclusion of appropriate transcription enhancer elements, transcription terminators, etc. (see Bittner et al. 1987 Methods in Enzymol 153:516-544).

[0082] In addition, a host cell strain may be chosen which modulates the expression of the inserted sequences, or modifies and processes the gene product in the specific fashion desired. Such modifications (e.g., glycosylation) and processing (e.g., cleavage) of protein products may be important for the function of the protein. Different host cells have characteristic and specific mechanisms for the post-translational processing and modification of proteins and gene products. Appropriate cell lines or host systems can be chosen to ensure the correct modification and processing of the foreign protein expressed. To this end, eukaryotic host cells which possess the cellular machinery for proper processing of the primary transcript, glycosylation, and phosphorylation of the gene product may be used. Such mammalian host cells include but are not limited to CHO, VERO, BHK, HeLa, COS, MDCK, 293, 3T3, W138, and in particular, salivary gland cell lines.

[0083] For long-term, high-yield production of recombinant proteins, stable expression is preferred. For example, cell lines which stably express the Ixolaris and Ixolaris-related nucleotide sequences described above may be engineered. Rather than using expression vectors which contain viral origins of replication, host cells can be transformed with DNA controlled by appropriate expression control elements (e.g., promoter, enhancer sequences, transcription terminators, polyadenylation sites, etc.), and a selectable marker. Following the introduction of the foreign DNA, engineered cells may be allowed to grow for 1-2 days in an enriched media, and then are switched to a selective media. The selectable marker in the recombinant plasmid confers resistance to the selection and allows cells to stably integrate the plasmid into their chromosomes and grow to form foci which in turn can be cloned and expanded into cell lines. This method may advantageously be used to engineer cell lines which express the Ixolaris and Ixolaris-related gene product.

[0084] A number of selection systems may be used, including but not limited to the herpes simplex virus thymidine kinase (Wigler, et al. 1977 Cell 11:223), hypoxanthine-guanine phosphoribosyltransferase (Szybalska & Szybalski 1962 PNAS USA 48:2026), and adenine phosphoribosyltransferase (Lowy, et al. 1980 Cell 22:817) genes can be employed in tk-, hgprt- or aprt-cells, respectively. Also, antimetabolite resistance can be used as the basis of selection for the following genes: dhfr, which confers resistance to methotrexate (Wigler, et al. 1980 PNAS USA 77:3567; O'Hare, et al. 1981 PNAS USA 78:1527); gpt, which confers resistance to mycophenolic acid (Mulligan & Berg 1981 PNAS USA 78:2072); neo, which confers resistance to the aminoglycoside G-418 (Colberre-Garapin, et al. 1981 J Mol Biol 150:1); and hygro, which confers resistance to hygromycin (Santerre et al. 1984 Gene 30:147)

[0085] Alternatively, any fusion protein may be readily purified by utilizing an antibody specific for the fusion protein being expressed. For example, a system described by Janknecht et al allows for the ready purification of non-denatured fusion proteins expressed in human cell lines (Janknecht et al. 1991 PNAS USA 88:8972-8976). In this system, the gene of interest is subcloned into a vaccinia recombination plasmid such that the gene's open reading frame is translationally fused to an amino-terminal tag consisting of six histidine residues. Extracts from cells infected with recombinant vaccinia virus are loaded onto Ni2+nitriloacetic acid-agarose columns and histidine-tagged proteins are selectively eluted with imidazole-containing buffers.

[0086] Antibodies to Ixolaris Proteins

[0087] Antibodies that specifically recognize one or more epitopes of Ixolaris, or epitopes of conserved variants of Ixolaris, or peptide fragments of Ixolaris are also encompassed by the invention. Such antibodies include but are not limited to polyclonal antibodies, monoclonal antibodies (mAbs), humanized or chimeric antibodies, single chain antibodies, Fab fragments, F(ab′)2 fragments, fragments produced by a Fab expression library, anti-idiotypic (anti-Id) antibodies, and epitope-binding fragments of any of the above.

[0088] The antibodies of the invention may be used, for example, for diagnostic purposes and for the identification of concentration levels of Ixolaris in various biological fluids. Immunoassays utilizing these antibodies may be used as a diagnostic test, such as to detect infection of a mammalian host by a tick or to detect Ixolaris from a tick in a tissue of the mammalian host. Also, such immunoassays may be used in the detection and isolation of Ixolaris from tissue homogenates, cloned cells, and the like. Alternatively, antibodies against Ixolaris can be used as a vaccine against tick infections in mammals. Or, antibodies can be used in conjunction with drug screening schemes.

[0089] For the production of antibodies, various host animals may be immunized by injection with Ixolaris, an Ixolaris peptide (e.g., one corresponding to a functional domain), truncated Ixolaris proteins, polypeptides, or peptides, functional equivalents of Ixolaris or variants of Ixolaris. Such host animals may include but are not limited to rabbits, mice, and rats, to name but a few. Various adjuvants may be used to increase the immunological response, depending on the host species, including but not limited to Freund's (complete and incomplete), mineral gels such as aluminum hydroxide, surface active substances such as lysolecithin, pluronic polyols, polyanions, peptides, oil emulsions, keyhole limpet hemocyanin, dinitrophenol, and potentially useful human adjuvants such as BCG (bacille Calmette-Guerin) and Corynebacterium parvum. Polyclonal antibodies are heterogeneous populations of antibody molecules derived from the sera of the immunized animals.

[0090] Monoclonal antibodies, which are homogeneous populations of antibodies to a particular antigen, may be obtained by any technique which provides for the production of antibody molecules by continuous cell lines in culture. These include, but are not limited to, the hybridoma technique of Kohler and Milstein, (1975 Nature 256:495-497; and U.S. Pat. No. 4,376,110), the human B-cell hybridoma technique (Kosbor et al. 1983 Immunology Today 4:72; Cole et al. 1983 PNAS USA 80:2026-2030), and the EBV-hybridoma technique (Cole et al. 1985 Monoclonal Antibodies And Cancer Therapy, Alan R. Liss, Inc., pp. 77-96). Such antibodies may be of any immunoglobulin class including IgG, IgM, IgE, IgA, IgD and any subclass thereof. The hybridoma producing the mAb of this invention may be cultivated in vitro or in vivo. Production of high titers of mAbs in vivo makes this the presently preferred method of production.

[0091] In addition, techniques developed for the production of “chimeric antibodies” (Morrison et al. 1984 PNAS USA 81:6851-6855; Neuberger et al. 1984 Nature 312:604-608; Takeda et al. 1985 Nature 314:452-454) by splicing the genes from a mouse antibody molecule of appropriate antigen specificity together with genes from a human antibody molecule of appropriate biological activity can be used. A chimeric antibody is a molecule in which different portions are derived from different animal species, such as those having a variable region derived from a murine mAb and a human immunoglobulin constant region.

[0092] Alternatively, techniques described for the production of single chain antibodies (U.S. Pat. No. 4,946,778; Bird 1988 Science 242:423-426; Huston et al. 1988 PNAS USA 85:5879-5883; and Ward et al. 1989 Nature 334:544-546) can be adapted to produce single chain antibodies against Ixolaris gene products. Single chain antibodies are formed by linking the heavy and light chain fragments of the Fv region via an amino acid bridge, resulting in a single chain polypeptide.

[0093] Antibody fragments which recognize specific epitopes may be generated by known techniques. For example, such fragments include but are not limited to: the F(ab′)2 fragments which can be produced by pepsin digestion of the antibody molecule and the Fab fragments which can be generated by reducing the disulfide bridges of the F(ab′) 2 fragments. Alternatively, Fab expression libraries may be constructed (Huse et al. 1989 Science 246:1275-1281) to allow rapid and easy identification of monoclonal Fab fragments with the desired specificity.

[0094] Antibodies to Ixolaris can, in turn, be utilized to generate anti-idiotype antibodies that “mimic” Ixolaris, using techniques well known to those skilled in the art. (See, e.g., Greenspan & Bona 1993 FASEB J 7(5):437-444; and Nissinoff 1991 J Immunol 147(8):2429-2438). For example antibodies which bind to a Kunitz domain and competitively inhibit the binding of Factor Xa, X, or VIIa to Ixolaris can be used to generate anti-idiotypes that “mimic” the Kunitz domain and, therefore, bind and neutralize Ixolaris. Such neutralizing anti-idiotypes or Fab fragments of such anti-idiotypes can be used in regimens to neutralize Ixolaris.

[0095] Diagnostic and Prognostic Assays of Ixolaris

[0096] A variety of methods can be employed for the diagnostic and prognostic evaluation of Ixolaris and Ixolaris gene specific nucleic acid molecules for the identification and concentration levels of Ixolaris and Ixolaris gene specific nucleic acid molecules in various biological tissues and fluids. These assays may be used to detect infection of a mammalian host by a tick or to detect Ixolaris from a tick in a tissue of a mammalian host. Also, such assays may be used in the detection of Ixolaris expression patterns to aid in diagnosis and prognosis of pathological states associated with Ixolaris.

[0097] Such methods may, for example, utilize reagents such as the Ixolaris nucleotide sequences described above, Ixolaris amino acid sequences described above, and Ixolaris antibodies described above. Specifically, such reagents may be used, for example, for: (1) the detection of the presence of Ixolaris expression or the detection of either an over- or under-expression of Ixolaris mRNA; (2) the detection of the presence of Ixolaris gene product or the detection of either an over- or under-abundance of Ixolaris gene product; and (3) the detection of the presence of Ixolaris antibodies.

[0098] The methods described herein may be performed, for example, by utilizing pre-packaged diagnostic kits comprising at least one specific Ixolaris nucleotide sequence, Ixolaris amino acid sequence or Ixolaris antibody reagent described herein, which may be conveniently used, e.g., in clinical settings, to diagnose patients exhibiting a pathological state associated with Ixolaris.

[0099] Information about Ixolaris gene specific nucleic acid molecules can be detected by utilizing a number of techniques. Nucleic acid from any nucleated cell can be used as the starting point for such assay techniques, and may be isolated according to standard nucleic acid preparation procedures which are well known to those of skill in the art. The use of microarrays to deternine gene expression requires DNA from the Ixolaris gene that can serve as a probe for detecting which genes in the microarray are active in different types of cells.

[0100] DNA may be used in hybridization or amplification assays. Such assays may include, but are not limited to, Southern analyses, dot blots, single stranded conformational polymorphism analyses (SSCP), restriction fragment length polymorphims (RFLPs) and PCR analyses.

[0101] Such diagnostic methods for the detection of Ixolaris gene specific nucleic acid molecules can involve for example, contacting and incubating nucleic acids, including recombinant DNA molecules, cloned genes or degenerate variants thereof, obtained from a sample, e.g., derived from a patient sample or other appropriate cellular source, with one or more labeled nucleic acid reagents, including recombinant DNA molecules, cloned genes or degenerate variants thereof under conditions favorable for the specific annealing of these reagents to their complementary sequences within the Ixolaris gene. Preferably, the lengths of these nucleic acid reagents are at least 15 to 30 nucleotides. After incubation, all non-annealed nucleic acids are removed from the nucleic acid:Ixolaris molecule hybrid. The presence of nucleic acids which have hybridized, if any such molecules exist, is then detected. Using such a detection scheme, the nucleic acid from the cell type or tissue of interest can be immobilized, for example, to a solid support, such as a membrane, or a plastic surface such as that on a microtiter plate or polystyrene beads. In this case, after incubation, non-annealed, labeled nucleic acid reagents are easily removed. Detection of the remaining, annealed, labeled Ixolaris nucleic acid reagents is accomplished using standard techniques well-known to those in the art. The Ixolaris gene sequences to which the nucleic acid reagents have annealed can be compared to the annealing pattern expected from a control gene sequence in order to detect Ixolaris gene specific nucleic acid molecules.

[0102] Alternative diagnostic methods for the detection of Ixolaris gene specific nucleic acid molecules, in patient samples or other appropriate cell sources, may involve their amplification, e.g., by PCR (the experimental embodiment set forth in Mullis, K. B. 1987 U.S. Pat. No. 4,683,202), followed by the detection of the amplified molecules using techniques well known to those of skill in the art. The resulting amplified sequences can be compared to those which would be expected if the nucleic acid being amplified contained control gene copies in order to detect Ixolaris gene specific nucleic acid molecules.

[0103] The level of Ixolaris gene expression can also be assayed by detecting and measuring Ixolaris transcription. For example, RNA from a cell type or tissue known, or suspected to express the Ixolaris gene, such as salivary gland, may be isolated and tested utilizing hybridization or PCR techniques such as are described, above. The isolated cells can be derived from cell culture or from a patient. The analysis of cells taken from culture may be a necessary step in the assessment of cells to be used as part of a cell-based therapy or, alternatively, to test the effect of compounds on the expression of the Ixolaris gene. Such analyses may reveal both quantitative and qualitative aspects of the expression pattern of the Ixolaris gene, including activation or inactivation of Ixolaris gene expression.

[0104] In one embodiment of such a detection scheme, cDNAs are synthesized from the RNAs of interest (e.g., by reverse transcription of the RNA molecule into cDNA). A sequence within the cDNA is then used as the template for a nucleic acid amplification reaction, such as a PCR amplification reaction, or the like. The nucleic acid reagents used as synthesis initiation reagents (e.g., primers) in the reverse transcription and nucleic acid amplification steps of this method are chosen from among the Ixolaris nucleic acid reagents described above. The preferred lengths of such nucleic acid reagents are at least 9-30 nucleotides. For detection of the amplified product, the nucleic acid amplification may be performed using radioactively or non-radioactively labeled nucleotides. Alternatively, enough amplified product may be made such that the product may be visualized by standard ethidium bromide staining or by utilizing any other suitable nucleic acid staining method.

[0105] Additionally, it is possible to perform such Ixolaris gene expression assays “in situ”, ie., directly upon tissue sections (fixed and/or frozen) of patient tissue obtained from biopsies or resections, such that no nucleic acid purification is necessary. Nucleic acid reagents such as those described above may be used as probes and/or primers for such in situ procedures (See, for example, Nuovo, G. J. 1992 “PCR In Situ Hybridization: Protocols And Applications”, Raven Press, NY).

[0106] Alternatively, if a sufficient quantity of the appropriate cells can be obtained, standard Northern analysis can be performed to determine the level of mRNA expression of the Ixolaris gene.

[0107] Immunoassays and non-immunoassays for Ixolaris gene products or conserved variants or peptide fragments thereof will typically comprise incubating a sample, such as a biological fluid, a tissue extract, freshly harvested cells, or lysates of cells which have been incubated in cell culture, in the presence of a detectably labeled antibody capable of identifying Ixolaris gene products or conserved variants or peptide fragments thereof, and detecting the bound antibody by any of a number of techniques well-known in the art.

[0108] The biological sample may be brought in contact with and immobilized onto a solid phase support or carrier such as nitrocellulose, or other solid support which is capable of immobilizing cells, cell particles or soluble proteins. The support may then be washed with suitable buffers followed by treatment with the detectably labeled Ixolaris antibody or Ixolaris gene product. The solid phase support may then be washed with the buffer a second time to remove unbound antibody or gene product. The amount of bound label on solid support may then be detected by conventional means.

[0109] By “solid phase support or carrier” is intended any support capable of binding an antigen or an antibody. Well-known supports or carriers include glass, polystyrene, polypropylene, polyethylene, dextran, nylon, amylases, natural and modified celluloses, polyacrylamides, gabbros, and magnetite. The nature of the carrier can be either soluble to some extent or insoluble for the purposes of the present invention. The support material may have virtually any possible structural configuration so long as the coupled molecule is capable of binding to an antigen or antibody. Thus, the support configuration may be spherical, as in a bead, or cylindrical, as in the inside surface of a test tube, or the external surface of a rod. Alternatively, the surface may be flat such as a sheet, test strip, etc. Preferred supports include polystyrene beads. Those skilled in the art will know many other suitable carriers for binding antibody or antigen, or will be able to ascertain the same by use of routine experimentation.

[0110] The binding activity of a given lot of Ixolaris antibody or Ixolaris gene product may be determined according to well known methods. Those skilled in the art will be able to determine operative and optimal assay conditions for each determination by employing routine experimentation.

[0111] With respect to antibodies, one of the ways in which the Ixolaris antibody can be detectably labeled is by linking the same to an enzyme and use in an enzyme immunoassay (EIA) (Voller, A., “The Enzyme Linked Immunosorbent Assay (ELISA)”, 1978, Diagnostic Horizons 2:1-7, Microbiological Associates Quarterly Publication, Walkersville, Md.; Voller, A. et al. 1978 J Clin Pathol 31:507-520; Butler, J. E. 1981 Meth Enzymol 73:482-523; Maggio, E. (ed.) 1980, Enzyme Immunoassay, CRC Press, Boca Raton, Fla.; Ishikawa, E. et al., (eds.) 1981 Enzyme Immunoassay, Kgaku Shoin, Tokyo). The enzyme which is bound to the antibody will react with an appropriate substrate, preferably a chromogenic substrate, in such a manner as to produce a chemical moiety which can be detected, for example, by spectrophotometric, fluorimetric or by visual means. Enzymes which can be used to detectably label the antibody include, but are not limited to, malate dehydrogenase, staphylococcal nuclease, delta-5-steroid isomerase, yeast alcohol dehydrogenase, alphaglycerophosphate, dehydrogenase, triose phosphate isomerase, horseradish peroxidase, alkaline phosphatase, asparaginase, glucose oxidase, beta-galactosidase, ribonuclease, urease, catalase, glucose-6-phosphate dehydrogenase, glucoamylase and acetylcholinesterase. The detection can be accomplished by calorimetric methods which employ a chromogenic substrate for the enzyme. Detection may also be accomplished by visual comparison of the extent of enzymatic reaction of a substrate in comparison with similarly prepared standards.

[0112] Detection may also be accomplished using any of a variety of other immunoassays. For example, by radioactively labeling the antibodies or antibody fragments, it is possible to detect Ixolaris through the use of a radioimmunoassay (RIA) (see, for example, Weintraub, B., Principles of Radioimmunoassays, Seventh Training Course on Radioligand Assay Techniques, The Endocrine Society, March, 1986, which is incorporated by reference herein). The radioactive isotope can be detected by such means as the use of a gamma counter or a scintillation counter or by autoradiography.

[0113] It is also possible to label the antibody with a fluorescent compound. When the fluorescently labeled antibody is exposed to light of the proper wave length, its presence can then be detected due to fluorescence. Among the most commonly used fluorescent labeling compounds are fluorescein isothiocyanate, rhodamine, phycoerythrin, phycocyanin, allophycocyanin, o-phthaldehyde and fluorescamine.

[0114] The antibody can also be detectably labeled using fluorescence emitting metals such as 152Eu, or others of the lanthanide series. These metals can be attached to the antibody using such metal chelating groups as diethylenetriaminepentacetic acid (DTPA) or ethylenediaminetetraacetic acid (EDTA).

[0115] The antibody also can be detectably labeled by coupling it to a chemiluminescent compound. The presence of the chemiluminescent-tagged antibody is then determined by detecting the presence of luminescence that arises during the course of a chemical reaction. Examples of particularly useful chemiluminescent labeling compounds are luminol, isoluminol, theromatic acridinium ester, imidazole, acridinium salt and oxalate ester.

[0116] Likewise, a bioluminescent compound may be used to label the antibody of the present invention. Bioluminescence is a type of chemiluminescence found in biological systems in, which a catalytic protein increases the efficiency of the chemiluminescent reaction. The presence of a bioluminescent protein is determined by detecting the presence of luminescence. Important bioluminescent compounds for purposes of labeling are luciferin, luciferase and aequorin.

[0117] Screening Assays for Compounds that Bind Ixolaris

[0118] The following assays are designed to identify compounds that interact with (e.g., bind to) Ixolaris.

[0119] Such compounds may include, but are not limited to, peptides such as, for example, soluble peptides, including but not limited to members of random peptide libraries; (see, e.g., Lam, K. S. et al. 1991 Nature 354:82-84; Houghten, R. et al. 1991 Nature 354:84-86), and combinatorial chemistry-derived molecular library made of D- and/or L-configuration amino acids, phosphopeptides (including, but not limited to, members of random or partially degenerate, directed phosphopeptide libraries; see, e.g., Songyang, Z. et al. 1993 Cell 72:767-778), antibodies (including, but not limited to, polyclonal, monoclonal, humanized, anti-idiotypic, chimeric or single chain antibodies, and FAb, F(ab′)2 and FAb expression library fragments, and epitope-binding fragments thereof), and small organic or inorganic molecules.

[0120] Computer modelling and searching technologies permit identification of compounds, or the improvement of already identified compounds, that can modulate Ixolaris activity. Having identified such a compound or composition, the active sites or regions are identified. Such active sites might typically be ligand binding sites. The active site can be identified using methods known in the art including, for example, from the amino acid sequences of peptides, from the nucleotide sequences of nucleic acids, or from study of complexes of the relevant compound or composition with its natural ligand. In the latter case, chemical or X-ray crystallographic methods can be used to find the active site by finding where on the factor the complexed ligand is found. Next, the three dimensional geometric structure of the active site is determined. This can be done by known methods, including X-ray crystallography, which can determine a complete molecular structure. On the other hand, solid or liquid phase NMR can be used to determine certain intra-molecular distances. Any other experimental method of structure determination can be used to obtain partial or complete geometric structures. The geometric structures may be measured with a complexed ligand, natural or artificial, which may increase the accuracy of the active site structure determined.

[0121] If an incomplete or insufficiently accurate structure is determined, the methods of computer based numerical modelling can be used to complete the structure or improve its accuracy. Any recognized modelling method may be used, including parameterized models specific to particular biopolymers such as proteins or nucleic acids, molecular dynamics models based on computing molecular motions, statistical mechanics models based on thermal ensembles, or combined models. For most types of models, standard molecular force fields, representing the forces between constituent atoms and groups, are necessary, and can be selected from force fields known in physical chemistry. The incomplete or less accurate experimental structures can serve as constraints on the complete and more accurate structures computed by these modeling methods.

[0122] Finally, having determined the structure of the active site, either experimentally, by modeling, or by a combination, candidate modulating compounds can be identified by searching databases containing compounds along with information on their molecular structure. Such a search seeks compounds having structures that match the determined active site structure and that interact with the groups defining the active site. Such a seach can be manual, but is preferably computer assisted. These compounds found from this search are potential Ixolaris modulating compounds.

[0123] Alternatively, these methods can be used to identify improved modulating compounds from an already known modulating compound or ligand. The composition of the known compound can be modified and the structural effects of modification can be determined using the experimental and computer modelling methods described above applied to the new composition. The altered structure is then compared to the active site structure of the compound to determine if an improved fit or interaction results. In this manner systematic variations in composition, such as by varying side groups, can be quickly evaluated to obtain modified modulating compounds or ligands of improved specificity or activity.

[0124] Further experimental and computer modeling methods useful to identify modulating compounds based upon identification of the active sites of Ixolaris will be apparent to those of skill in the art.

[0125] Examples of molecular modelling systems are the CHARMM and QUANTA programs (Polygen Corporation, Waltham, Mass.). CHARMM performs the energy minimization and molecular dynamics functions. QUANTA performs the construction, graphic modelling and analysis of molecular structure. QUANTA allows interactive construction, modification, visualization, and analysis of the behavior of molecules with each other.

[0126] A number of articles review computer modelling of drugs interactive with specific-proteins, such as Rotivinen, et al. 1988 Acta Pharmaceutical Fennica 97:159-166; Ripka, 1988 New Scientist 54-57; McKinaly and Rossmann 1989 Annu Rev Pharmacol Toxiciol 29:111-122; Perry and Davies, OSAR: Quantitative Structure-Activity Relationships in Drug Design pp. 189-193 (Alan R. Liss, Inc. 1989); Lewis and Dean, 1989 Proc R. Soc Lond 236:125-140 and 141-162; and, with respect to a model receptor for nucleic acid components, Askew, et al. 1989 J Am Chem Soc 111:1082-1090. Other computer programs that screen and graphically depict chemicals are available from companies such as BioDesign, Inc. (Pasadena, Calif.), Allelix, Inc. (Mississauga, Ontario, Canada), and Hypercube, Inc. (Cambridge, Ontario). Although these are primarily designed for application to drugs specific to particular proteins, they can be adapted to design of drugs specific to regions of DNA or RNA, once that region is identified.

[0127] Although described above with reference to design and generation of compounds which could alter binding, one could also screen libraries of known compounds, including natural products or synthetic chemicals, and biologically active materials, including proteins, for compounds which are inhibitors or activators.

[0128] Compounds identified via assays such as those described herein may be useful, for example, in modulating the blood coagulation cascade.

[0129] In Vitro Screening Assays

[0130] In vitro systems may be designed to identify compounds capable of interacting with (e.g., binding to) Ixolaris. The principle of the assays used to identify compounds that bind to Ixolaris involves preparing a reaction mixture of Ixolaris and the test compound under conditions and for a time sufficient to allow the two components to interact and bind, thus forming a complex which can be removed and/or detected in the reaction mixture. The Ixolaris species used can vary depending upon the goal of the screening assay.

[0131] The screening assays can be conducted in a variety of ways. For example, one method to conduct such an assay would involve anchoring the Ixolaris protein, polypeptide, peptide or fusion protein or the test substance onto a solid phase and detecting Ixolaris/test compound complexes anchored on the solid phase at the end of the reaction. In one embodiment of such a method, the Ixolaris reactant may be anchored onto a solid surface, and the test compound, which is not anchored, may be labeled, either directly or indirectly.

[0132] In practice, microtiter plates may conveniently be utilized as the solid phase. The anchored component may be immobilized by non-covalent or covalent attachments. Non-covalent attachment may be accomplished by simply coating the solid surface with a solution of the protein and drying. Alternatively, an immobilized antibody, preferably a monoclonal antibody, specific for the protein to be immobilized may be used to anchor the protein to the solid surface. The surfaces may be prepared in advance and stored.

[0133] In order to conduct the assay, the nonimmobilized component is added to the coated surface containing the anchored component. After the reaction is complete, unreacted components are removed (e.g., by washing) under conditions such that any complexes formed will remain immobilized on the solid surface. The detection of complexes anchored on the solid surface can be accomplished in a number of ways. Where the previously nonimmobilized component is pre-labeled, the detection of label immobilized on the surface indicates that complexes were formed. Where the previously nonimmobilized component is not pre-labeled, an indirect label can be used to detect complexes anchored on the surface; e.g., using a labeled antibody specific for the previously nonimmobilized component (the antibody, in turn, may be directly labeled or indirectly labeled with a labeled anti-Ig antibody).

[0134] Alternatively, a reaction can be conducted in a liquid phase, the reaction products separated from unreacted components, and complexes detected; e.g., using an immobilized antibody specific for Ixolaris protein, polypeptide, peptide or fusion protein or the test compound to anchor any complexes formed in solution, and a labeled antibody specific for the other component of the possible complex to detect anchored complexes.

[0135] In Vivo Screening Assays

[0136] In vivo systems may be designed to identify compounds capable of interacting with (e.g., binding to) Ixolaris. One method which detects protein interactions in vivo, the two-hybrid system, is described in detail for illustration only and not by way of limitation. One version of this system has been described (Chien et al. 1991 PNAS USA, 88:9578-9582) and is commercially available from Clontech (Palo Alto, Calif.).

[0137] Briefly, utilizing such a system, plasmids are constructed that encode two hybrid proteins: one plasmid consists of nucleotides encoding the DNA-binding domain of a transcription activator protein fused to an Ixolaris nucleotide sequence encoding Ixolaris, an Ixolaris polypeptide, peptide or fusion protein, and the other plasmid consists of nucleotides encoding the transcription activator protein's activation domain fused to a cDNA encoding an unknown protein which has been recombined into this plasmid as part of a cDNA library. The DNA-binding domain fusion plasmid and the cDNA library are transformed into a strain of the yeast Saccharomyces cerevisiae that contains a reporter gene (e.g., HBS or lacZ) whose regulatory region contains the transcription activator's binding site. Either hybrid protein alone cannot activate transcription of the reporter gene: the DNA-binding domain hybrid cannot because it does not provide activation function and the activation domain hybrid cannot because it cannot localize to the activator's binding sites. Interaction of the two hybrid proteins reconstitutes the functional activator protein and results in expression of the reporter gene, which is detected by an assay for the reporter gene product.

[0138] The two-hybrid system or related methodology may be used to screen activation domain libraries for proteins that interact with the “bait” gene product. By way of example, and not by way of limitation, Ixolaris may be used as the bait gene product. Total genomic or cDNA sequences are fused to the DNA encoding an activation domain. This library and a plasmid encoding a hybrid of a bait Ixolaris gene product fused to the DNA-binding domain are cotransformed into a yeast reporter strain, and the resulting transformants are screened for those that express the reporter gene. For example, and not by way of limitation, a bait Ixolaris gene sequence, such as the open reading frame of Ixolaris (or a Kunitz domain), can be cloned into a vector such that it is translationally fused to the DNA encoding the DNA-binding domain of the GAL4 protein. These colonies are purified and the library plasmids responsible for reporter gene expression are isolated. DNA sequencing is then used to identify the proteins encoded by the library plasmids.

[0139] A cDNA library of the cell line from which proteins that interact with bait Ixolaris gene product are to be detected can be made using methods routinely practiced in the art. According to the particular system described herein, for example, the cDNA fragments can be inserted into a vector such that they are translationally fused to the transcriptional activation domain of GAL4. This library can be co-transformed along with the bait Ixolaris gene-GAL4 fusion plasmid into a yeast strain which contains a lacZ gene driven by a promoter which contains GAL4 activation sequence. A cDNA encoded protein, fused to GAL4 transcriptional activation domain, that interacts with bait Ixolaris gene product will reconstitute an active GAL4 protein and thereby drive expression of the HIS3 gene. Colonies which express HIS3 can be detected by their growth on petri dishes containing semi-solid agar based media lacking histidine. The cDNA can then be purified from these strains, and used to produce and isolate the bait Ixolaris gene-interacting protein using techniques routinely practiced in the art.

[0140] Assays for Compounds that Modulate the Interaction of Binding Partners with Ixolaris

[0141] The macromolecules that interact with Ixolaris are referred to, for purposes of this discussion, as “binding partners”. These binding partners are likely to be involved in the Ixolaris mediated blood coagulation cascade. Therefore, it is desirable to identify compounds that modulate the interaction of such binding partners with Ixolaris.

[0142] The basic principle of the assay systems used to identify compounds that modulate the interaction between Ixolaris and its binding partner (e.g., Factor Xa, X, or VIIa, or Factor VIIa/TF complex) involves preparing a reaction mixture containing Ixolaris protein, polypeptide, peptide or fusion protein as described above, and the binding partner under conditions and for a time sufficient to allow the two to interact and bind, thus forming a complex. In order to test a compound for modulating activity, the reaction mixture is prepared in the presence and absence of the test compound. The test compound may be initially included in the reaction mixture, or may be added at a time subsequent to the addition of the Ixolaris moiety and its binding partner. Control reaction mixtures are incubated without the test compound or with a placebo. The formation of any complexes between the Ixolaris moiety and the binding partner is then detected. The formation of a complex in the control reaction, but not in the reaction mixture containing the test compound, indicates that the compound modulates the interaction of Ixolaris and the interactive binding partner.

[0143] The assay for compounds that modulate the interaction of Ixolaris and binding partners can be conducted in a heterogeneous or homogeneous format. Heterogeneous assays involve anchoring either the Ixolaris moiety product or the binding partner onto a solid phase and detecting complexes anchored on the solid phase at the end of the reaction. In homogeneous assays, the entire reaction is carried out in a liquid phase. In either approach, the order of addition of reactants can be varied to obtain different information about the compounds being tested. For example, test compounds that inhibit the interaction by competition can be identified by conducting the reaction in the presence of the test substance; i.e., by adding the test substance to the reaction mixture prior to or simultaneously with the Ixolaris moiety and interactive binding partner. Alternatively, test compounds that disrupt preformed complexes, e.g. compounds with higher binding constants that displace one of the components from the complex, can be tested by adding the test compound to the reaction mixture after complexes have been formed. The various formats are described briefly below.

[0144] In a heterogeneous assay system, either the Ixolaris moiety or the interactive binding partner, is anchored onto a solid surface, while the non-anchored species is labeled, either directly or indirectly. In practice, microtiter plates are conveniently utilized. The anchored species may be immobilized by non-covalent or covalent attachments. Non-covalent attachment may be accomplished simply by coating the solid surface with a solution of the Ixolaris gene product or binding partner and drying. Alternatively, an immobilized antibody specific for the species to be anchored may be used to anchor the species to the solid surface. The surfaces may be prepared in advance and stored.

[0145] In order to conduct the assay, the partner of the immobilized species is exposed to the coated surface with or without the test compound. After the reaction is complete, unreacted components are removed (e.g., by washing) and any complexes formed will remain immobilized on the solid surface. The detection of complexes anchored on the solid surface can be accomplished in a number of ways. Where the non-immobilized species is pre-labeled, the detection of label immobilized on the surface indicates that complexes were formed. Where the non-immobilized species is not pre-labeled, an indirect label can be used to detect complexes anchored on the surface; e.g., using a labeled antibody specific for the initially non-immobilized species (the antibody, in turn, may be directly labeled or indirectly labeled with a labeled anti-Ig antibody). Depending upon the order of addition of reaction components, test compounds which inhibit complex formation or which disrupt preformed complexes can be detected.

[0146] Alternatively, the reaction can be conducted in a liquid phase in the presence or absence of the test compound, the reaction products separated from unreacted components, and complexes detected; e.g., using an immobilized antibody specific for one of the binding components to anchor any complexes formed in solution, and a labeled antibody specific for the other partner to detect anchored complexes. Again, depending upon the order of addition of reactants to the liquid phase, test compounds which inhibit complex or which disrupt preformed complexes can be identified.

[0147] In an alternate embodiment, a homogeneous assay can be used. In this approach, a preformed complex of the Ixolaris moiety and the interactive binding partner is prepared in which either the Ixolaris or its binding partners is labeled, but the signal generated by the label is quenched due to formation of the complex (see, e.g., U.S. Pat. No. 4,109,496 by Rubenstein which utilizes this approach for immunoassays). The addition of a test substance that competes with and displaces one of the species from the preformed complex will result in the generation of a signal above background. In this way, test substances which disrupt Ixolaris/binding partner interaction can be identified.

[0148] In a particular embodiment, an Ixolaris fusion can be prepared for immobilization. For example, Ixolaris or a peptide fragment, e.g., corresponding to a Kunitz domain, can be fused to a glutathione-S-transferase (GST) gene using a fusion vector, such as pGEX-5X-1, in such a manner that its binding activity is maintained in the resulting fusion protein. The interactive binding partner can be purified and used to raise a monoclonal antibody, using methods routinely practiced in the art and described above. This antibody can be labeled with the radioactive isotope 125I, for example, by methods routinely practiced in the art. In a heterogeneous assay, e.g., the GST-Ixolaris fusion protein can be anchored to glutathione-agarose beads. The interactive binding partner can then be added in the presence or absence of the test compound in a manner that allows interaction and binding to occur. At the end of the reaction period, unbound material can be washed away, and the labeled monoclonal antibody can be added to the system and allowed to bind to the complexed components. The interaction between the Ixolaris gene product and the interactive binding partner can be detected by measuring the amount of radioactivity that remains associated with the glutathione-agarose beads. A successful inhibition of the interaction by the test compound will result in a decrease in measured radioactivity.

[0149] Alternatively, the GST-Ixolaris fusion protein and the interactive binding partner can be mixed together in liquid in the absence of the solid glutathione-agarose beads. The test compound can be added either during or after the species are allowed to interact. This mixture can then be added to the glutathione-agarose beads and unbound material is washed away. Again the extent of inhibition of the Ixolaris/binding partner interaction can be detected by adding the labeled antibody and measuring the radioactivity associated with the beads.

[0150] In another embodiment, these same techniques can be employed using peptide fragments that correspond to a Kunitz domain of Ixolaris and/or the interactive binding partner (in cases where the binding partner is a protein), in place of one or both of the full length proteins. Any number of methods routinely practiced in the art can be used to identify and isolate the binding sites. These methods include, but are not limited to, mutagenesis of the gene encoding one of the proteins and screening for disruption of binding in a co-immunoprecipitation assay. Compensating mutations in the gene encoding the second species in the complex can then be selected. Sequence analysis of the genes encoding the respective proteins will reveal the mutations that correspond to the region of the protein involved in interactive binding. Alternatively, one protein can be anchored to a solid surface using methods described above, and allowed to interact with and bind to its labeled binding partner, which has been treated with a proteolytic enzyme, such as trypsin. After washing, a short, labeled peptide comprising the binding domain may remain associated with the solid material, which can be isolated and identified by amino acid sequencing. Also, once the gene coding for the binding partner is obtained, short gene segments can be engineered to express peptide fragments of the protein, which can then be tested for binding activity and purified or synthesized.

[0151] Assays for Identification of Compounds that Modulate Coagulation

[0152] Compounds, including but not limited to binding compounds identified via assay techniques such as those described in the sections can be tested for the ability to modulate the blood coagulation cascade. The assays described above can identify compounds which affect Ixolaris activity (e.g., compounds that bind to Ixolaris, inhibit binding of the natural ligand, and either activate signal transduction (agonists) or block activation (antagonists), and compounds that bind to the natural ligand of Ixolaris and neutralize ligand activity). Such compounds can be used as part of a therapeutic regimen.

[0153] The invention encompasses cell-based and animal model-based assays for the identification of compounds exhibiting such an ability to modulate the blood coagulation cascade.

[0154] Cell-based systems can be used to identify compounds which may act to modulate the blood coagulation cascade. Such cell systems can include, for example, recombinant or non-recombinant cells, such as cell lines, which express a tissue factor. In addition, expression host cells (e.g., COS cells, CHO cells, fibroblasts) genetically engineered to express a tissue factor and to respond to activation by Ixolaris, e.g., as measured by a chemical or phenotypic change, induction of another host cell gene, change in ion flux, tyrosine phosphorylation of host cell proteins, etc., can be used as an end point in the assay.

[0155] In addition, animal-based systems may be used to identify compounds capable of modulating the blood coagulation cascade. Such animal models may be used as test substrates for the identification of pharmaceuticals, therapies and interventions which may be effective in such modulation. For example, animal models may be exposed to a compound, suspected of exhibiting an ability to modulate the blood coagulation cascade, at a sufficient concentration and for a time sufficient to elicit such a modulation in the exposed animals. The response of the animals to the exposure may be monitored by assessing the responses associated with activation or deactivation of the blood coagulation cascade.

[0156] Vaccine and Pharmaceutical Preparations and Methods of Administration and Other Uses

[0157] The compounds of the present invention when made and selected as disclosed are useful as potent inhibitors of blood coagulation in vitro and in vivo. As such, these compounds are useful as in vitro diagnostic reagents to prevent the clotting of blood and are also useful as in vivo pharmaceutical agents to inhibit the blood coagulation cascade in mammals.

[0158] The compounds of the present invention are useful as in vitro diagnostic reagents for inhibiting clotting in blood drawing tubes. The use of stoppered test tubes having a vacuum therein as a means to draw blood obtained by venipuncture into the tube is well known in the medical arts (Kasten, B. L., “Specimen Collection”, Laboratory Test Handbook, 2nd Edition, Lexi-Comp Inc., Cleveland pp. 16-17 eds. Jacobs, D. S. et al. 1990). Such vacuum tubes may be free of clot-inhibiting additives, in which case, they are useful for the isolation of mammalian serum from the blood. They may alternatively contain clot-inhibiting additives (such as heparin salts, EDTA salts, citrate salts or oxalate salts), in which case, they are useful for the isolation of mammalian plasma from the blood. The compounds of the present invention are potent inhibitors of blood clotting and as such, can be incorporated into blood collection tubes to prevent clotting of the mammalian blood drawn into them.

[0159] The compounds of the present invention are used alone, in combination of other compounds of the present invention, or in combination with other known inhibitors of clotting, in the blood collection tubes, for example, with heparin salts, EDTA salts, citrate salts or oxalate salts.

[0160] The amount to be added to such tubes, or effective amount, is that amount sufficient to inhibit the formation of a blood clot when mammalian blood is drawn into the tube. The compounds of the present invention are added to blood collection tubes in such amounts that, when combined with 2 to 10 ml of mammalian blood, the concentration of such compounds will be sufficient to inhibit the formation of blood clots. Typically, this effective amount is that required to give a final concentration in the blood of about 1 to 10,000 nM, with 10 to 1000 nM being preferred.

[0161] The compounds of the present invention may also be used to prepare diagnostic compositions. In one embodiment, diagnostic compositions are prepared by dissolving the compounds of the present invention into diagnostically acceptable carriers, which carriers include phosphate buffered saline (0.01 M sodium phosphate, 0.15 M sodium chloride, pH 7.2), or Tris buffered saline (0.05 M Tris-HCl 0.15 M sodium chloride, pH 8.0). In another embodiment, the compounds of the present invention may be blended with other solid diagnostically acceptable carriers by methods well known in the art to provide solid diagnostic compositions. These carriers include buffer salts.

[0162] The addition of the compounds of the present invention to blood collection tubes may be accomplished by methods well known in the art, which methods include introduction of a liquid diagnostic composition thereof, a solid diagnostic composition thereof, or a liquid diagnostic composition which is lyophilized in such tubes to a solid plug of a solid diagnostic composition.

[0163] The use of blood collection tubes containing the diagnostic compositions of the present invention comprises contacting a effective amount of such diagnostic composition with mammalian blood drawn into the tube. Typically, when a sample of 2 to 10 ml of mammalian blood is drawn into a blood collection tube and contacted with such diagnostic composition therein; the effective amount to be used will include those concentrations of the comopunds formulated as a diagnostic composition which in the blood sample are sufficient to inhibit the formation of blood clots. Preferred effective concentrations would be about 1 to 10,000 nM, with 10 to 1000 nM being especially preferred.

[0164] According to an alternate aspect of our invention, the nucleic acid and amino acid compounds of the present invention are also useful as pharmaceutical agents for modulating the blood coagulation cascade in a mammal. This modulation of the blood coagulation cascade includes facilitating or inhibiting coagulation. Preferred is inhibiting.

[0165] The nucleic acid and amino acid compounds can alternatively be used, with suitable adjuvants, as a gene or component vaccine against tick and tick-borne infections in mammals. Immunization with tick vaccine may be used in both the prophylaxis and therapy of parasitic infections. Disease conditions caused and transmitted by ticks may be treated by administering to an animal infected with these parasites anti-Ixolaris antibody.

[0166] The vaccine or pharmaceutical compositions of the present invention are administered in vivo, ordinarily in a mammal, preferably in a human. In employing them in vivo, the vaccine or pharmaceutical compositions can be administered to a mammal in a variety of ways, including orally, parenterally, intravenously, subcutaneously, intramuscularly, colonically, rectally, nasally or intraperitoneally, employing a variety of dosage forms. Administration is preferably parenteral, such as intravenous on a daily basis. Alternatively, administration is preferably oral, such as by tablets, capsules or elixers taken on a daily basis.

[0167] In addition to the active ingredients, these vaccine and pharmaceutical compositions may contain suitable pharmaceutically-acceptable carriers comprising excipients and auxiliaries which facilitate processing of the active compounds into preparations which can be used pharmaceutically. Further details on techniques for formulation and administration may be found in the latest edition of Remington's Pharmaceutical Sciences (Maack Publishing Co., Easton, Pa.).

[0168] Pharmaceutical formulations suitable for parenteral administration may be formulated in aqueous solutions, preferably in physiologically compatible buffers such as Hanks' solution, Ringer's solution, or physiologically buffered saline. Aqueous injection suspensions may contain substances which increase the viscosity of the suspension, such as sodium carboxymethyl cellulose, sorbitol, or dextran. Additionally, suspensions of the active compounds may be prepared as appropriate oily injection suspensions. Suitable lipophilic solvents or vehicles include fatty oils such as sesame oil, or synthetic fatty acid esters, such as ethyl oleate or triglycerides, or liposomes. Optionally, the suspension may also contain suitable stabilizers or agents which increase the solubility of the compounds to allow for the preparation of highly concentrated solutions.

[0169] Pharmaceutical compositions for oral administration can be formulated using pharmaceutically acceptable carriers well known in the art in dosages suitable for oral administration. Such carriers enable the pharmaceutical compositions to be formulated as tablets, pills, dragees, capsules, liquids, gels, syrups, slurries, suspensions, and the like, for ingestion by the patient.

[0170] For topical or nasal administration, penetrants appropriate to the particular barrier to be permeated are used in the formulation. Such penetrants are generally known in the art.

[0171] The pharmaceutical compositions of the present invention may be manufactured in a manner that is known in the art, e.g., by means of conventional mixing, dissolving, granulating, dragee-making, levigating, emulsifying, encapsulating, entrapping, or lyophilizing processes.

[0172] After pharmaceutical compositions have been prepared, they can be placed in an appropriate container and labeled for treatment of an indicated condition.

[0173] Pharmaceutical compositions suitable for use in the invention include compositions wherein the active ingredients are contained in an effective amount to achieve the intended purpose. The determination of an effective dose is well within the capability of those skilled in the art.

[0174] For any compound, the therapeutically effective dose can be estimated initially either in cell culture assays, e.g., of cell lines, or in animal models, usually mice, rabbits, dogs, or pigs. The animal model may also be used to determine the appropriate concentration range and route of administration. Such information can then be used to determine useful doses and routes for administration in humans.

[0175] A therapeutically effective dose refers to that amount of active ingredient, for example Ixolaris or fragments thereof, antibodies of Ixolaris, agonists, antagonists or etc of Ixolaris, which ameliorates the symptoms or condition. Therapeutic efficacy and toxicity may be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., ED50 (the dose therapeutically effective in 50% of the population) and LD50 (the dose lethal to 50% of the population). The dose ratio between therapeutic and toxic effects is the therapeutic index, and it can be expressed as the ratio, LD50/dED50. Pharmaceutical compositions which exhibit large therapeutic indices are preferred. The data obtained from cell culture assays and animal studies is used in formulating a range of dosage for human use. The dosage contained in such compositions is preferably within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage varies within this range depending upon the dosage form employed, sensitivity of the patient, and the route of administration.

[0176] The exact dosage will be determined by the practitioner, in light of factors related to the subject that requires treatment. Dosage and administration are adjusted to provide sufficient levels of the active moiety or to maintain the desired effect. Factors which may be taken into account include the severity of the disease state, general health of the subject, age, weight, and gender of the subject, diet, time and frequency of administration, drug combination(s), reaction sensitivities, and tolerance/response to therapy. Long-acting pharmaceutical compositions may be administered every 3 to 4 days, every week, or once every two weeks depending on half-life and clearance rate of the particular formulation.

[0177] Normal dosage amounts may vary from 0.1 to 100,000 micrograms, up to a total dose of about 1 g, depending upon the route of administration. Guidance as to particular dosages and methods of delivery is provided in the literature and generally available to practitioners in the art. For the present invention, alone or as part of a pharmaceutical composition, such doses are between about 0.01 mg/kg and 100 mg/kg body weight, preferably between about 0.01 and 10 mg/kg, body weight.

EXAMPLE 1

[0178] Materials. Factor VIIa, Tissue Factor (lipidated), TFPI-depleted plasma, truncated TFPI(1-161) (4900T), and full-length TFPI (4900PC) were purchased from American Diagnostica (Greenwich, Conn.). Factor X, Factor Xa, Factor XIa, Factor IX, Factor V, prothrombin, thrombin, [5-(dimethylamino)-1-naphthalenesulfonyl]glutamylgly cylarginyl chloromethyl ketone (dansyl-Glu-Gly-Arg-CK or DEGR-CK), elastase, and activated protein C chromogenic substrate were purchased from CalBiochem (San Diego, Calif.). γ-Carboxyglutamic acid domainless Factor Xa (Gla-Factor Xa) and Human DEGR-Factor Xa (Factor VII/VIIa free; 0 units/mg of Factor Xa), and monoclonal anti-human Factor VIIa were obtained from Hematologic Technologies (Essex Junction, Vt.). Goat anti-human Factor X affinity-purified IgG was from Enzyme Research Laboratoires (South Bend, Ind.). Chromogenic substrates for Factor Xa (N-Benzoyl-L-isoleucyl-L-glutamyl-glycyl-L-arginine-p-nitroaniline hydrochloride, S2222), thrombin (H-D-Phenylalanyl-L-pipecolyl-L-arginine-p-nitroaniline dihydrochloride, S2238), Factor VIIa (H-D-Isoleucyl-L-prolyl-L-arginine-p-nitroaniline dihydrochloride, S2288), Factor XIa (L-Pyroglutamyl-L-proplyl-L-arginine-p-nitroaniline dihydrochloride, S2366), and plasmin (H-D-Valyl-L-leucyl-L-lysine-p-nitroaniline dihydrochloride, S2251) were purchased from Chromogenix (Milano, Italy). Thrombomax with calcium reagent, trypsin, chymotrypsin, clastase, tryptase, and rabbit anti-goat alkaline phosphatase (AP)-coupled secondary antibody was obtained from Sigma Chemical (St. Louis, Mo.). Anti-mouse AP-coupled secondary antibody and Western Blue stabilized substrate for AP were obtained from Promega (Madison, Wis.). Reptilase (Bothrops atrox thrombin-like enzyme) and coat-test kit for Factor VIII were obtained from Diagnostica Stago (Les Ulis, France). Precast 12% Tris glycine gel, precast 12% Nu-PAGE, MES buffer, NuPAGE LDS sample buffer, and NuPAGE antioxidant were purchased from Novex Experimental Technology (Santa Cruz, Calif.). Silver-staining kit was obtained from Bio-Rad (Hercules, Calif.). Macrosphere octadecylsilica column was from Alltech (Deerfield, Ill.), Centripep filters from Millipore (Bedford, Mass.), and MonoQ column from Amersham Pharmacia Biotech (Piscataway, N.J.). Vydac C18 column was purchased from The Separation Group, Inc. (Hesperia, Calif.). Other equipment used were CM-4100 pumps and SM-4100 UV detector from ThermoSeparation Products (Riviera Beach, Fla.) and a FC203-B fraction collector from Gilson (Middleton, Wis.).

[0179] Ticks and tick saliva. Tick saliva was obtained by inducing partially engorged adult female I. scapularis to salivate into capillary tubes using the modified (Valenzuela, J. G. et al. 2000 J Biol Chem 275:18717-18723) pilocarpine induction method (Tatchell, R. J. 1967 J Parasitol 53:1106-1107). Tick salivary gland extracts were prepared by collecting glands from partially engorged female I. scapularis as described (Valenzuela, J. G. et al. 2000 J Biol Chem 275:18717-18723). Glands were stored frozen at −75° C. until needed.

[0180] Salivaty gland cDNA construction. This procedure was performed as detailed before (Valenzuela, J. G. et al. 2000 J Biol Chem 275:18717-18723). Briefly, the Micro-FastTrack mRNA isolation kit (Invitrogen, San Diego, Calif.) was used to isolate the mRNA. The I. scapularis salivary gland mRNA (200 ng) was reverse-transcribed to cDNA, followed by double-strand synthesis and ligated into a Lambda Triplex2 vector, and the resulting ligation reaction was packed using Gigapack gold III from Stratagene/Biocrest (Cedar Creek, Tenn.). The library obtained was plated by infecting log-phase XL1-blue cells. Randomly picked clones from this library were sequenced exactly as described before (Valenzuela, J. G. et al. 2000 J Biol Chem 275:18717-18723). After identifying a cDNA with high similarity to TFPI following blastx program of the cDNA against the National Center for Biotechnological Information (NCBI) non-redundant database (Altschul, S. F. et al. 1997 Nucl Acid Res 25:3389-3402), an aliquot (˜100 ng) of Ixolaris PCR sample was re-amplified, and the entire cDNA was fully sequenced using custom primers.

[0181] Ixolaris Expression vector. For expression of Ixolaris, full-length cDNA was used as a template to amplify only the cDNA that begins at the initial methionine and ends at the first stop codon. A Kozak consensus sequence (ANNATGG) (SEQ ID NO:473) was added, the DNA amplified forward primer: 5′-AAA ATG GGC GCT GTT TCC TGC TTC-3′ (SEQ ID NO:474); reverse primer: 5′-GGA TGA TCA GTT AAT AGT GAC ATT TAC-3′ (SEQ ID NO:475) and cloned into the vector pIB/V5-His TOPO (Invitrogen, San Diego, Calif.) following manufacturer's specifications. Amplification conditions were: 1 hold at 95° C. for 1 min, and 25 cycles at 94° C. for 1 min, 55° C. for 30 s, and 68° C. for 1 min. Amplified products were visualized on a 1.1% agarose gel with ethidium bromide. The single amplified product obtained was immediately cloned into the vector pIB/V5-His TOPO (Invitrogen, San Diego, Calif.) following manufacturer's specifications. The ligation mixture was used to transform TOP10 cells (Invitrogen), and the cells were incubated overnight at 37° C. Eight colonies were selected and mixed with 10 μL of sterile water. Five μL of each sample were transfered to Luria broth with ampicillin (100 μg/mL) and grown at 37° C. The remaining 5 μL were used as a template for a PCR reaction using two vector-specific primers from the pIB/V5-His TOPO vector to confirm the presence of the insert and for sequencing analysis. After visualization of the PCR product on a 1.1% agarose gel, we completely sequenced the eight PCR products described above with a CEQ2000 DNA sequencing instrument (Beckman Coulter, Fullerton, Calif.). We chose two samples, one of which contained the complete sequence (from methionine to stop codon) in the correct orientation of Ixolaris for expression on this vector. The second sample (control), was the complete Ixolaris sequence in reverse orientation for expression in this cell vector. Cells containing the sample and control were grown overnight at 37° C. on Luria broth with ampicillin (100 μg/mL), and plasmid isolation was performed using the Wizard miniprep kit (Promega). After plasmid isolation, the sample and control plasmids were washed three times with ultrapure water using an Amicon-100 (Millipore), the concentration of sample was measured, and the samples were stored at −30° C. before High Five cell transformation.

[0182] Expression of Ixolaris in insect cell line BTI-TN-5B1-4 (High Five). High Five cells (Invitrogen) were cultivated in High Five serum-free medium (Invitrogen) supplemented with 10 μg/mL gentamycin. Cell density of 2.0×106 cells/mL and 60% to 70% confluency were used for transfection of I. scapularis TFPI cDNA and I. scapularis TFPI anti-sense construct (control). Transfections were performed using 70 μL of Insectin-Plus Liposomes (Invitrogen) added to 5 mL of Ultimate Insect Serum-Free medium (Invitrogen) containing 1 μg plasmid DNA/mL of medium in a 15-mL sterile tube. After vortexing for 10 seconds, the mixture was incubated at room temperature for 15 minutes. The mixture was then added very slowly to a monolayer of High Five cells (in a 25-cm2 flask) from which the culture medium had just been removed. The flasks were then transferred to a rocking platform at a speed of 2 side-to-side per minute for 4 hours at room temperature. Finally, the cells were incubated at 27° C. for up to 4 days. After 2 days of incubation, the supernatant (5 mL) was collected and stored for further analysis. High Five cells (Invitrogen), cultivated in High Five serum-free medium (Invitrogen) supplemented with 10 μg/mL gentamycin were used for transfection with Ixolaris and anti-sense (control) constructs plasmid as indicated by the manufacturer. After 2 days of incubation, the supernatant (5 mL) was collected and stored for further analysis.

[0183] Sequence analysis. Sequence similarity searches were performed using the Blast (Altschul, S. F. et al. 1997 Nucl Acids Res 25:3389-3402) program. Cleavage site predictions of the mature proteins used the SignalP (Nielsen, H. et al. 1997 Protein Eng 10:1-6) program. Alignments of protein sequences were done with the ClustalW program version 1.7 (Thompson, J. D. et al. 1994 Nucl Acids Res 22:4673-4686). Protein parameters were obtained at http://www.mbshortcuts.com: Mr, 15738.35; pI, 4.56; Σ A280, 20260; A280/cm (1 mg/mL), 1.287. Detection of N-linked glycosylation sites was obtained at http://molbio.info.nih.gov/molbio/gcglite.

[0184] Chromatographic procedures and purification of recombinant Ixolaris. Supernatants of transformed cells were filtrated with Centriprep filter (50 kDa cutoff). The filtrate was concentrated 20 fold using a Centriprep (3 kDa cutoff). One mL of concentrated supernatant (˜8 mg) was diluted to 5 mL with water and applied to a 5×100 mm Pharmacia MonoQ eluted with a gradient from 25 mM Hepes pH 7.2 to 1 M NaCl in the same buffer, for 1 hour, at 0.5 mL/minute. Active fractions were pooled and applied to a Vydac 218TP510 octadecyl-silica column (10×250 mm) eluted at 1.5 mL/minute with a 60-minute gradient from 10% to 80% acetonitrile in water containing 0.1% trifluoroacetic acid (TFA). Active fractions were pooled, diluted with water to 8 mL, and re-chromatographed in a 2.1×250 mm Macrosphere octadecylsilica column eluted at 0.2 mL/minute for 55 minutes, and at 0.1 mL/minute afterward.

[0185] Estimation of Ixolaris concentration. Concentration of Ixolaris (corrected for Σ280) was estimated by the area of absorbance at A280 nm (calibration with BSA) of the peak containing Ixolaris activity obtained in the last purification step (FIG. 6C). Human TFPI nominal concentration was estimated according to the concentration provided by the manufacturer.

[0186] PAGE of recombinant lxolaris. Three μL of SDS (20%)+30 μL of Fraction 83 (˜0.5 μg Ixolaris in acetonitrile) obtained from the last purification step of Ixolaris (FIG. 6C) were vacuum dried overnight at room temperature. The sample was resuspended in 30 μL of distilled water and divided in two aliquots. NU-PAGE loading buffer was added to sample #1 (15 μL, 0.25 μg) (denaturating conditions), and DTT was included in the loading buffer for sample #2 (reducing conditions). The samples were boiled for 5 minutes at 100° C., and additional reducing agent (β-mercaptoethanol, 1% final concentration) was added to sample #2 just before loading into a 12% NU-PAGE gel, MOPS buffer containing NuPAGE antioxidant. For PAGE under native conditions, 0.25 μg Ixolaris dried without SDS was applied to a 12% gel. Gels were silver stained according to manufacture's instructions.

[0187] Binding of Ixolaris to Factor X, Factor Xa and Factor VIIa. Ixolaris (20 nM) was preincubated with Factor X (20 nM), Factor Xa (20 nM), or Factor VIIa (20 nM) in 5 mM HEPES, pH 7.4, for 10 minutes. The sample was loaded into a 8% precast PAGE and proteins were then transferred to PVDF membrane in 10 mM CAPS, 10% methanol, pH 11. Primary antibody (polyclonal antibody anti-Factor X, 10 μg/mL, or MoAb anti-Factor VII, 5 μg/mL) was incubated for 1 hour in TBS-T (Tris-buffered saline, with 0.05% Tween and 5% non-fat milk). After three 10-minute washes with TBS-T, the membranes were incubated for 30 minutes with rabbit anti-goat AP-coupled secondary antibody (1:20,000 in TBS-T) for detection of Factor X and Factor Xa, or with anti-mouse AP-coupled secondary antibody (1:10,000 in TBS-T) for detection of Factor VIIa. After membrane washing, Western Blue Stabilized substrate for AP (Promega) was added. Reactions were stopped by addition of water.

[0188] Kinetic assay of Factor Xa production by Factor VIIa/TF. This assay was performed as described by Lindhout et al (Lindhout, T. et al. 1995 Thromb Haemost 74:910-915). Ixolaris was incubated with Factor X, followed by addition of Factor VIIa/TF (1 nM/0.2 pM) previously incubated at 37° C. in buffer containing 50 mM Hepes, 0.1 M NaCl, 5 mM CaCl2, 0.5% BSA, pH 7.4 (Buffer A). Chromogenic substrate (S2222, 250 μM) hydrolysis was detected using a Versamax microplate ELISA reader (Molecular Devices, Sunnyvale, Calif.) equipped with a microplate mixer and heating system (Francischetti, I. M. B. et al. 1999 Biochemistry 3:16674-16685). The total volume of the reactions was 200 μl. Care was taken to ensure that substrate was less than 20% hydrolyzed. Reactions were continuously recorded at 405 nm for 1 hour at 37° C. To have an estimation of Factor Xa production at each time point, data was transformed as Δ absorbance (Δ A405/min) as described (Hamamoto, T. et al. 1993 J Biol Chem 268:8704-8710) using Excel 2000 software (MicroSoft Excel Analysis Tools, Seattle, Wash.). Factor Xa concentrations were interpolated from a standard curve relating Δ A405/min and known Factor Xa concentrations (Hamamoto, T. et al. 1993 J Biol Chem 268:8704-8710). Amidolytic activity by Factor VIIa/TF alone upon S2222 alone was not detected. In some experiments, data were plotted as Vs/Vo against Ixolaris concentration, where Vs is the velocity of substrate hydrolysis in the presence of inhibitor and Vo in its absence (Williams, J. W., and Morrison J. F. 1979 Methods Enzymol 63:437-467; Cha, S. 1975 Biochem Pharmacol 24:2177-2185). Enzymes, Ixolaris, and chromogenic substrate were diluted in a Buffer A. Specific assay conditions are described in the figure legends.

[0189] Preparation of DEGR-FX and des-Gla-DEGR-Xa. This procedure was performed as described by Husten et al. (Husten, E. J. et al 1987 J Biol Chem 262:12953-12961), with modifications. DEGR (40 μM) was added to des-Gla-Factor Xa (2 μM) in 100 mM Tris, 100 mM NaCl, and incubated overnight at room temperature. The mixture was extensively dialyzed against 1 liter TBS (3 times), and recovered to test for amidolytic activity that was not detectable after 1-hour incubation of des-Gla-DEGR-Factor Xa (40 nM) with S2222 (1 mM) at 37° C. Factor X (2 μM) was incubated with DEGR, and dialyzed as described above. DEGR-Factor X was devoid of coagulant activity and exhibited no amidolytic activity following incubation with Factor VIIa/TF. DEGR-Factor X or DEGR-Factor Xa (10 nM) did not interfere with the amidolytic activity of FVIIa/TF (1 nM/1 nM) upon S2288, indicating that complete removal of free DEGR was achieved by extensive dialysis.

[0190] Factor VIIa/TF amidolytic activity. Ixolaris was incubated for 15 minutes at 37° C. with Factor VIIa/TF (1 nM/1 nM) (previously incubated for 15 min at 37° C.) followed by addition of S2288 (1 mM) (Hamamoto, T. et al. 1993 J Biol Chem 268:8704-8710). Substrate hydrolysis was followed at 405 nm, at 37° C. In some experiments, reactions were initiated with Ixolaris or Ixolaris/scaffold that was added to a mixture containing Factor VIIa/TF and S2288.

[0191] Activation of Factor IX. This procedure was performed as described by Komiyama et al. (Komiyama, Y. et al. 1990 Biochemistry 29:9418-9425). Briefly, Factor VIIa (1 nM)/TF (1 nM) was incubated with Ixolaris for 15 min at 37° C. followed by addition of Factor IX (1.4 μM). In some experiments, Ixolaris was previously incubated with DEGR-FX or DEGR-FXa for 15 min at 37° C., before addition of Factor VIIa/TF. After 15 minutes, Factor IX (1.4 μM) was added and reactions continued for 40 minutes at 37° C. Reactions were stopped by addition of Laemmly buffer, and boiling for 5 min. Proteins were separated by 4 -12% NU/PAGE with MES buffer. All reactants were incubated in 50 mM Hepes, 100 mM NaCl, 5mM CaCl2, 0.01% BSA. Factor IX (1.4 μM) was devoid of amidolytic activity after 1 hour incubation with S2222 (250 μM), indicating that Factor Xa was not a contaminant of the preparation. Under identical experimental conditions, Factor Xa could be detected at concentration as low as 20 pM. To test whether Factor IX was contaminated with Factor X, Factor IX (1.4 μM) was incubated with Factor VIIa/TF (4 nM/1 pM) and S2222 and no substrate hydrolysis could be detected. Control experiments showed that 50 pM Factor X incubated with FVIIa/TF was followed by substrate hydrolysis. This result indicated that Factor IX was not contaminated with detectable concentration of Factor X. Bands were analyzed by densitometry (SigmaScan software) and the area calculated for quantification of Factor IX activation.

[0192] Human umbilical vein endothelial cells (HUVEC) culture, and generation of FXa by HUVEC. This procedure was performed as described by Orthner et al (Orthner, C. et al. 1995 Blood 86:436-443). Primary culture of HUVEC, harvested from umbilical veins was purchased from Clonetics (San Diego, Calif.). After trypsinization cells were grown to confluence in 96-well plates in 200 μl EBM-2 medium in a humidified incubator at 37° C. with 5% CO2. On the day of experiment EBM-2 was replaced by 200 μl fresh EBM-2, and LPS (10 μg/ml) was added for 4 hours to induce TF expression. Subsequently, cells were rinsed three times with HEPES-buffer (10 mM HEPES, 135 mM NaCl, 4 mM KCl, 1 mM MgCl2, 4 mM CaCl2, 11 mM D-glucose, and 0.5% BSA). HEPES-buffer was removed and a mixture of 180 μl containing Factor X (200 nM) and Ixolaris (0-8 nM) previously incubated together at 37° C. for 15 min was added to the cells. This step was followed immediately by addition of Factor VIIa (1 nM) to start reactions. After 30 min, 100 μl was removed and added to 100 μl of S2222 (500 μM) diluted in Buffer A. Absorbance reading at 405 nm (substrate hydrolysis) was followed for 1 h and Factor Xa concentration was estimated by a standard curve, using known concentrations of Factor Xa. Appropriate controls were run in parallel.

[0193] Prothrombin time. This procedure was performed using thromboMAX with Calcium reagent (Sigma) following manufacturer's instructions. Ixolaris (0-10 nM) was incubated with pre-warmed (37° C.) plasma (100 μl), followed by addition of pre-warmed thromboplastin reagent (200 μl). Tubes were shaken and the time necessary for clot formations was detected by visual inspection.

[0194] Specificity of Ixolaris. Ixolaris (32 nM, final concentration) was preincubated for 15 minutes at 37° C. with the enzymes listed in Table 1, followed by addition of the appropriate chromogenic substrate as indicated in Table 1.

[0195] Statistical analysis, curve fitting, and data handling. Data are presented as the mean±SE, using SigmaPlot Graphing software, statistical mode (Jandel Scientific).

[0196] While the present invention has been described in some detail for purposes of clarity and understanding, one skilled in the art will appreciate that various changes in form and detail can be made without departing from the true scope of the invention. All references referred to above are hereby incorporated by reference.

	Number	Date	Country
Parent	PCT/US01/42472	Oct 2001	US
Child	10408166	Apr 2003	US

Ixodes scapularis tissue factor pathway inhibitor

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