WO2001000667A2 - Anti-thrombin peptide from anopheles albimanus salivary gland - Google Patents

Abstract

The DNA and amino acid sequences are disclosed for a novel anti-thrombin peptide, anophelin, one embodiment of which was isolated form the salivary glands of the mosquito Anopheles albimanus. Also disclosed are anti-thrombotic therapeutic applications of anophelin.

Description

NOVEL ANΠ-THROMBIN PEPTΓDE

FIELD

This disclosure relates to nucleic acid and amino acid sequences corresponding to the anti- thrombin peptide anophelin, isolated from the salivary glands of the mosquito Anopheles albimanus. The sequences are useful for inhibiting platelet aggregation and blood clotting.

BACKGROUND

Normal hemostasis is the result of a complex balance between the processes of clot formation (blood coagulation) and clot dissolution (fibrinolysis). The complex interactions between blood cells, specific plasma proteins and the vascular surface, maintain the fluidity of blood unless injury and blood loss occur (for review see Kalafatis et al. Crit. Rev. Eukaryot. Gene Expr. 7:241- 80, 1997).

Immediately following a trauma, blood platelets begin to adhere to the edges of the lesion. Once in contact with collagen or α-thrombin, platelets release several chemicals, including ADP (adenosine diphosphate) and thromboxane A₂. This chemical release causes additional platelets from the blood to aggregate to those already attached to the vessel wall. Platelets also release platelet factor 3, which promotes the clotting cascade, which generates α-thrombin. α-Thrombin binds to receptors on the platelet membrane and causes further platelet aggregation and release. This cascade ultimately results in fibrin deposition at the site of injury, forming a mixed clot composed of aggregated platelets and polymerized fibrin.

The formation of α-thrombin, the primary mediator of thrombus (blood clot) formation, is catalyzed by factor Xa following the assembly of the catalytic prothrombinase complex (Mann et al., Blood, 76: 1-16, 1990). α-Thrombin specifically cleaves circulating fibrinogen, forming insoluble fibrin which spontaneously aggregates to form a fibrin clot. In addition, α-thrombin activates several proteases including factors V, VIII, and XIII and protein C in the clotting cascade (Fenton et al. , Chemistry and Biology of Thrombin, Lundblad et al. , Eds. , pp 43-70, Ann Arbor Science Publishers, Ann Arbor, MI, 1977). Beyond its direct role in the formation and stabilization of fibrin clots, α-thrombin also has bioregulatory effects on several cellular components within the vasculature and blood (Shuman, Ann. NY Acad. Sci. , 405:349, 1986).

These diverse biological functions of α-fhrombin rely on its individual functional domains (for review of α-thrombin structure see Stubbs et al. Thromb. Res. 1993 69: 1-58). α-Thrombin contains a catalytic triad within a deep canyon-like active site cleft (catalytic site) and two extended surfaces mainly composed of positively charged residues known as anion binding exosites (TABE1 and TABE2) (Grutter et al. EMBO J. 9:2361-5, 1990; Rydel et al. Science 249:277-80, 1990; Bode et al. Protein Sci. 1 :426-471, 1992). Although necessary for normal hemostasis, blood clot formation resulting from platelet aggregation and chemical release is also responsible for several life-threatening vascular diseases, including myocardial infarction, stroke, pulmonary embolism, deep vein thrombosis, peripheral arterial occlusion, disseminated intravascular coagulation (DIC), and other cardiovascular thromboses. Other pathophysiological conditions associated with blood clot formation include post operative trauma, obesity, pregnancy, side effects of oral contraceptives, and prolonged immobilization. In patients suffering from such diseases or conditions, platelet aggregation is an undesirable event which should be inhibited. Inhibition of platelet aggregation may also be desirable in extracorporeal treatments of blood, such as dialysis, and storage of platelets in platelet concentrates. In vascular surgery, the inhibition of blood clotting is essential for maintaining the integrity of the blood vessel, such as a vascular graft. If clot formation occurs after such surgery on a vessel that perfuses a critical organ, it may threaten the life of the patient.

Alpha-thrombin has been reported to be the primary pathophysiologic-mediator of platelet- dependent arterial thrombus formation (Eidt et al. , J. Clin. Invest. , 84: 18-27, 1989) indicating that it plays a central role in the diseases and conditions described above. In addition, thrombin is responsible for the degradation of platelets during their storage, which results in a decreased storage life (Bode and Miller, Vox Sang., 51 : 192-96, 1986). As a result of these deleterious effects due to α-thrombin, there is a continual search for new or improved α-thrombin inhibitors and anticoagulants. Currently, treatment and prophylaxis of thrombotic diseases involve therapeutics which act in one of two different ways. The first type inhibits α-thrombin activity or α-thrombin formation, thus preventing clot formation. The second category accelerates thrombolysis and dissolves the blood clot, thereby removing it from the blood vessel and unblocking the flow of blood (Cazenave et al, Agents Action, 15:24-49, 1984). Heparin, a compound of the first class, is currently the most widely used anticoagulant and anti-thrombotic drug. It is used to treat conditions, such as venous thromboembolism, in which α- thrombin activity is responsible for the development or expansion of a thrombus. Heparin exerts its effects by accelerating the anticoagulant activity of antifhrombin III, a protein which complexes with and inactivates thrombin. In spite of its wide-spread usage, heparin can produce many undesirable side effects, including hemorrhaging and heparin-induced thrombocytopenia. In patients suffering from heparin-induced thrombocytopenia, heparin accelerates platelet aggregation, often with fatal consequences. In patients having an anti-thrombin III deficiency, for example in the cases of thrombosis associated with nephrosis or disseminated intravascular coagulation syndrome (DIC), heparin is simply less effective. Accordingly, the need exists for alternatives to conventional heparin-based therapies.

Hirudin, a member of the second class of anti-thrombotic drugs, is a naturally occurring polypeptide produced in the salivary gland of the blood sucking leech Hirudo medicinalis (Markwardt, Thromb. Haemost. 72:477-80, 1994). Hirudin is a low molecular weight peptide (7 kD) comprised of 65 amino acids (Dodt et al. , FEBS Lett. , 165: 180-4, 1984) which prevents blood from coagulating by binding to both exosite I (TABEl) and the catalytic site of α-thrombin (Stone and Hofsteenge, Biochem. , 25:4622-28, 1986). This interaction inhibits the binding of α-thrombin to platelets (Ganguly and Sonnichsen, Br. J. Haemotol , 34:291-301 , 1976; Tam and Detwiler, Biochim. Biophys. Acta, 543: 194-201, 1978), prevents α-thrombin-induced platelet aggregation (Tam et al., J. Biol. Chem. , 254:8723-5, 1979) and inhibits α-thrombin from catalyzing the conversion of fibrinogen to fibrin. U.S. Patent No. 5,256,559 to Maraganore et al. teaches the use of hirudin and its derivatives for decreasing or preventing platelet aggregation and platelet activation. Hirudin is particularly useful in patients for whom standard heparin therapy is contraindicated due to a history of heparin-induced thrombocytopenia or an antithrombin III deficiency.

Although hirudin has demonstrated efficacy in preventing venous thrombosis, vascular shunt occlusion and thrombin-induced disseminated intravascular coagulation, there are disadvantages to its use. Hirudin prolongs bleeding time in a dose-dependent manner, thus making the determination and administration of proper dosages critically important. Furthermore, the high cost and low supply of the naturally occurring product has prevented its widespread use, in spite of the ability to produce hirudin through recombinant DNA techniques (EP Patent Nos. 200,655, 158,564, 168,342 and 171,024). The need still exists for effective α-thrombin inhibitors, which inhibit clot formation, platelet aggregation and secretion, that is not characterized by some of the severe side effects associated with conventional agents, and which can be produced in commercially feasible amounts.

SUMMARY The salivary anti-thrombin protein of Anopheles albimanus mosquitoes, herein called anophelin, is a novel, specific, tight-binding and effective inhibitor of α-thrombin. The interaction of anophelin with α-thrombin inhibits platelet aggregation and blood clotting. Anophelin forms an equimolecular complex of high affinity to the catalytic and TABEl site of α-thrombin, but does not substantially interact with prothrombin, factor X, active protein C, trypsin, chymotrypsin, factor IXa, plasmin, elastase, reptilase, or factor Xa. Interestingly, anophelin contains no cysteine residues. This property makes anophelin easier to produce in large amounts using chemical synthesis.

Disclosed herein is a purified protein having anophelin biological activity, which inhibits α-thrombin and platelet aggregation. In some disclosed embodiments, the anophelin protein has the amino acid sequence shown in either SEQ ID NOs 3-5, or amino acid sequences that differ from those specified in SEQ ID NOs 3-5 by one or more conservative amino acid substitutions, or amino acid sequences having at least 60% sequence identity to those sequences, for example sequences that are at least 75% , 90% , 95% or even 98 or 99% identical. Other embodiments include a purified biologically active anophelin protein that is at least 50% , 75% or 95 % pure. Also included is an isolated nucleic acid molecule encoding a biologically active anophelin protein, particularly such molecules that include a promoter sequence operably linked to the nucleic acid molecule for expression of the anophelin protein. In addition to such variants that retain biological activity of the anophelin protein, fragments of the sequences that retain such activity may be used. Such fragments may, for example, include at least 50% , 75 % , 90% or 95% of the amino acid resudies of the native peptide sequence.

In particular embodiments, the isolated nucleic acid molecule includes at least 30 contiguous nucleotides of a sequence selected from SEQ ID NO 1 or its complementary strand; or at least 21 contiguous nucleotides of a sequence selected SEQ ID NO 2 or its complementary strand. Alternatively, the isolated nucleic acid molecule includes at least 40 or 50 contiguous nucleotides of SEQ ID NO 1 or at least 30 or 50 contiguous nucleotides of SEQ ID NO 2, or a nucleic acid molecule that is at least 60% homologous to SEQ ID NOs 1 or 2, and encodes a protein having anophelin biological activity. Alternatively, the nucleic acid molecule has a sequence which hybridizes under conditions of at least 75% or 90% stringency to the sequences defined in SEQ ID NOs 1 or 2, or which has the full length sequence of SEQ ID NO 1 or its complementary strand, or SEQ ID NO 2 or its complementary strand.

Also disclosed herein are recombinant vectors that include any of the nucleic acid molecules, and transgenic hosts into which the recombinant vector is incorporated. Also disclosed are the purified peptides encoded by any of these nucleic acid molecules, such as proteins having anophelin biological activity which can be used to inhibit α-thrombin activity and platelet aggregation.

In addition, also disclosed are particular embodiments in which an extract containing water soluble components of a salivary gland homogenate of a mosquito of A. albimanus is prepared by sonicating A. albimanus salivary glands in buffer containing about 10 mM sodium phosphate pH 7.0, and about 150 mM NaCl. The homogenate is centrifuged to separate soluble from insoluble components. In a particular embodiment, the extract contains anophelin biological activity. A particular embodiment of a purified protein having anophelin biological activity, wherein the protein may optionally be purified from the extract described above, has an ability to inhibit platelet aggregation by thrombin by a factor of at least 1.5, for example at least 2. In more particular examples, the protein may have a molecular weight of about 6.2-6.6, for example 6.3- 6.5 kD, and/or a pi of about 3.5, and/or lack cysteine residues, and/or has non-covalent interactions with both the anion binding exosite (TABE) and the catalytic site of α-thrombin, and/or has anti-α-fhrombin activity with a K, of less than about 100 nM, for example less than about 100 pM, for example such as less than 50 pM, for example about 34 pM or less, in the absence of salt, and antagonizes clotting and inhibits platelet aggregation as disclosed. Also disclosed is a purified protein having anophelin biological activity generated from the extract with a purity of at least 50 % , 90 % , or 95 % . In another embodiment, a purified protein having anophelin biological activity may be prepared by chemical synthesis followed by HPLC purification and concentration. Also disclosed are specific binding agents capable of specifically binding to a A. albimanus anophelin protein, for example polyclonal antibodies, monoclonal antibodies, and fragments of monoclonal antibodies that specifically bind to the A. albimanus anophelin protein. Such specific binding agents can be used in assays for quantitating amounts of purified anophelin.

Other embodiments inlcude a composition having a therapeutically effective amount of a protein with anophelin biological activity, in combination with a pharmaceutically acceptable carrier. In other embodiments (examples), the composition further includes one or more anti-α- thrombin compounds. The protein having anophelin biological activity contained within such compositions includes any anophelin protein or peptide described herein, including fragments and variants. In other examples, the composition can include a therapeutically effective amount of the extract described above and a pharmaceutically acceptable carrier. The disclosed compositions can be used for in inhibiting thrombin activity, for example in anti-thrmobotic amounts sufficient to inhibit thrombin activity in a subject, such as a human, in whom pathological thrombosis is not desired. The compositions can be used in subjects who suffer from a condition such as myocardial infarction, stroke, pulmonary embolism, deep vein thrombosis, peripheral arterial occlusion, disseminated intravascular coagulation, cardiovascular and cerebrovascular thrombosis, thrombosis associated with post-operative trauma, obesity, pregnancy, side effects of oral contraceptives, prolonged immobilization, and hypercoaguable states associated with hematalogic, immunologic or rheumatological disorders. Alternatively, the subject may suffer from unstable angina, arteriosclerosis, a reblockage of vessels after angioplasty with a balloon catheter, or blood clotting in hemodialysis. The disclosed compositions can be used as anti-coagulants to inhibit thrombin activity by inhibiting platelet aggregation in extracorporeal blood, for example by admixing an effective amount of the composition with the extracorporeal blood. In addition, the disclosed compositions can be used to inhibit thrombin activity by inhibiting platelet aggregation in stored platelets, by storing platelets in the presence of an effective amount of the composition. The disclosed compositions can also be used to inhibit thrombin activity by inhibiting platelet aggregation in a subject by administering an effective amount of the composition to the subject.

Also disclosed herein are methods for inhibiting α-thrombin activity by contacting blood with an effective amount of a purified protein, extract, or composition, having anophelin biological activity. For example, α-thrombin activity in a subject can be inhibited by administering a therapeutically effective amount of a protein (including variants and fragments), extract or composition having anophelin biological activity to a subject, sufficient to inhibit α-fhrombin activity in the subject. In one embodiment the subject is one in whom pathological thrombosis is not desired. In other embodiments, the subject suffers from a condition such as: myocardial infarction, stroke, pulmonary embolism, deep vein thrombosis, peripheral arterial occlusion, disseminated intravascular coagulation, cardiovascular and cerebrovascular thrombosis, thrombosis associated with post-operative trauma, obesity, pregnancy, side effects of oral contraceptives, prolonged immobilization, and hypercoaguable states associated with hematalogic, immunologic or rheumatological disorders. The subject may, for example, be someone with unstable angina, arteriosclerosis, a reblockage of vessels after angioplasty with a balloon catheter, or blood clotting in hemodialysis. Also disclosed is a method that includes administering an effective amount of a composition having anophelin biological activity to a subject, sufficient to inhibit α-thrombin activity by inhibiting platelet aggregation. The subject includes humans.

The foregoing and other objects, features, and advantages disclosed herein will become more apparent from the following detailed description of a several embodiments which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a graph showing the inhibition of α-thrombin-induced platelet aggregation by a salivary gland homogenate of A. albimanus.

FIG. 2 is a graph showing the HPLC purification of A. albimanus salivary anti-α- fhrombin. The eluted proteins were detected at 280 nm (A), and tested for anti-α-thrombin activity (B).

FIG. 3 is a graph showing the second purification step of the A. albimanus salivary anti-α- fhrombin protein. The eluent was monitored at 220 nm (A) and the fractions tested for anti-α- thrombin activity using an α-thrombin chromogenic assay (B) or a platelet aggregation assay (C).

FIG. 4 is a graphical representation of the mass spectroscopy analysis of the purified A. albimanus anti-α-thrombin protein.

FIG. 5 A shows the predicted DNA and protein sequences of the AlbieAT clone. Underlined amino acids represent sequences obtained by Edman degradation of Asp-N digestion products from purified anti-α-thrombin.

FIG. 5B shows the alignment of the AlbieAT clone with two cDNA clones from A. gambiae: cE5 (Accession number Y17717) (SEQ ID NO 12) and FI (Accession number AJ000038) (SEQ ID NO 13). Identical amino acids within the three sequences are shaded. Bold type indicates a substitution of a charged amino acid by another charge amino acid.

FIG. 6 is a graph showing the mass spectra analysis of synthetic anophelin.

FIG. 7 is a graph showing the effect of synthetic anophelin in the recalcification time assay (A), and in the α-thrombin induced platelet aggregation assay (B). Each data point indicates the average ± S.E.M. of triplicate experiments. FIG. 8 is a graph showing the effect of synthetic anophelin in an α- thrombin chromogenic substrate assay (■) and on a thrombin fibrinogen assay (#). Each data point indicates the average ± S.E.M. of triplicate experiments.

FIG. 9 is a graph showing the anophelin interaction with α-thrombin. The effect of anophelin was measured in the presence of 0.52 nM (_#), 1.05 nM (>) and 2.1 nM (A) thrombin. The inset shows α-thrombin activity as a function of the concentration of anophelin divided by the concentration of α-thrombin used in each data point. Each data point is the average ± S.E.M. of triplicate experiments.

FIG. 10 is a graph which demonstrates the specificity of anophelin to α-thrombin (•), as compared to activated factor Xa (■), trypsin (A) and activated protein C (▼).

FIG. 11A is a graph showing the results of band densitometry quantitation, and a digital image of a protein gel (inset) showing that anophelin binds to α-thrombin. Lanes 1 and 7, α- thrombin (8.3 μM); lane 2, anophelin (4.5 μM); lane 3, α-thrombin (1.38 μM) and anophelin (4.5 μM); lane 4, α-thrombin (2.76 μM) and anophelin (4.5 μM); lane 5, α-fhrombin (4.5 μM) and anophelin (4.5 μM); lane 6, α-thrombin (8.3 μM) and anophelin (4.5 μM); lane 8, anophelin (33.2 μM). Inset: arrows, α-thrombin; arrowhead, anophelin-α-thrombin complex; open arrows, anophelin.

FIG. 1 IB are two graphs showing the results of band densitometry quantitation which show the disappearance of the band corresponding to anophelin (inset, right y axis, closed circles) and the appearance of α-thrombin activity (inset, left y axis, open triangles) with increasing α- thrombin- anophelin molar ratios.

FIG. 12 is a graph showing progress curves for α-thrombin-mediated S-2238 hydrolysis in the absence (curve a) and presence of anophelin (curves b and c), which demonstrates the slow- binding inhibition of α-thrombin by anophelin when α-thrombin is added to a mixture of anophelin and substrate.

FIG. 13 is a graph representing the kinetics of α-thrombin-induced chromogenic substrate hydrolysis by anophelin. Inset: relationship of the apparent dissociation constant, Ki*, to substrate concentration, when reactions were initiated by the addition of α-thrombin. The points in each figure are the mean + SE of six independent experiments. FIG. 14 is a graph showing the relationship between the apparent first-order rate constant, k_obs, and the concentration of anophelin. Inset: plots of the slope (K/(l + [S]/K_m) of the main graph and three additional curves at different substrate concentrations against 1/(1 + [S]/K_m).

FIG. 15 A is a graph showing progress curves obtained by adding α-thrombin to a mixture containing anophelin (a, 0 nM; b, 0.625 nM; c, 1.25 nM; d, 2.5 nM; e, 5 nM; f, 10 nM; g, 20 nM; h, 30 nM; i, 40 nM) and chromogenic substrate. FIG. 15B is a graph showing the double-reciprocal plot of the inhibition of α-thrombin by anophelin (• 0.625 nM; ■ 1.25 nM; ▲ 2.5 nM; T 5 nM; ♦ 10 nM) at different substrate concentrations (62.5- 500 μM). The points in each figure are the mean ± SE of seven independent experiments. FIG. 15C is a graph showing the kinetics of anophelin inhibition of fibrinogen clotting by α-thrombin.

FIG. 16A is a graph showing progress curves, which demonstrate the fast-binding inhibition of γ-thrombin by anophelin (a, 0 nM; b, 1.125 nM; c, 2.25 nM; d, 4.5 nM; e, 9 nM; f, 18 nM; g, 36 nM; h, 54 nM; i, 72 nM). FIG. 16B is graph of the double-reciprocal plot of the K,* data from steady-state velocities.

FIG. 16C is a digital image of a protein gel showing that anophelin binds to γ-thrombin but not to PPACK-γ-thrombin. Lane 1, γ-fhrombin; lane 2, γ-thrombin and anophelin; lane 3, PPACK-γ-thrombin; lane 4, PPACK-γ-fhrombin and anophelin. Arrow, γ-thrombin; arrowhead, anophelin-γ-thrombin complex; open arrow, PPACK-treated γ-thrombin.

FIG. 17 is a graph showing the kinetics of anophelin inhibition of chromogenic substrate hydrolysis by γ-thrombin when the reactions were initiated by the addition of chromogenic substrate.

FIG. 18A is a graph showing the effect of C-terminal hirudin fragment 54-65 on α- thrombin inhibition by anophelin.

FIG. 18B is a digital image of a protein gel stained with Coomassie blue, α-thrombin was incubated with buffer (lanes 1 and 3) or anophelin (lanes 2 and 4) in the absence (lanes 1 and 2) or presence (lanes 3 and 4) of trypsin.

FIG. 19 is a graph showing the effect of anophelin on clot-bound α-thrombin. FIG. 20 is a graph showing the effect of anophelin on α-thrombin generation in plasma.

SEQUENCE LISTING

The nucleic and amino acid sequences listed in the accompanying sequence listing are shown using standard letter abbreviations for nucleotide bases, and three letter code for amino acids. Only one strand of each nucleic acid sequence is shown, but the complementary strand is understood as included by any reference to the displayed strand.

SEQ ID NO 1 shows the nucleotide sequence of the Anopheles albimanus anophelin cDNA.

SEQ ID NO 2 shows the ORF of the A. albimanus anophelin cDNA. SEQ ID NO 3 shows the amino acid sequence of the A. albimanus anophelin protein encoded by the cDNA.

SEQ ID NO 4 shows the amino acid sequence of the last 61 amino acids of anophelin. SEQ ID NO 5 shows the amino acid sequence of the last 59 amino acids of anophelin.

SEQ ID NOs 6-8 show the peptide fragments generated from Asp-N enzymatic cleavage of anophelin.

SEQ ID NOs 9-10 show PCR primers that can be used to amplify the anophelin sequence of A. albimanus.

SEQ ID NO 11 shows a highly conserved amino acid sequence within anophelin.

SEQ ID NO 12 shows the amino acid sequence of Accession No. Y17717 from A. gambiae.

SEQ ID NO 13 shows the amino acid sequence of Accession No. AJOO0038 from A. gambiae.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS Abbreviations and Definitions

The following definitions and methods are provided to better define the materials and methods disclosed herein and to guide those of ordinary skill in the art in the practice of the materials and methods disclosed herein. As used herein (including the appended claims), the singular forms "a" or "an" or "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a protein" includes a plurality of such proteins and reference to "the antibody" includes reference to one or more antibodies and equivalents thereof known to those skilled in the art, and so forth.

Anophelin biological activity: In its broadest sense, such biological activity includes the ability to inhibit platelet aggregation by thrombin, by a factor of at least 1.5, for example at least 2, as determined by the assay described in EXAMPLE 2 (where the factor refers to at least approximately double the recalcification time of citrated plasma using the assay described in EXAMPLE 7 from zero to 250 nM of the anophelin). Alternatively (or in addition), the protein has the ability to bind to both the catalytic and the TABEl sites of α-thrombin, and/or can inhibit α-thrombin as determined by either a chromogenic or fibrinogen assay in the range of 1 nM as described in EXAMPLE 7. Such activity inhibits α-thrombin with a K_:* and a K_j of less than about lnm, for example less than 100 pM, for example approximately 30 pM, and clot-bound α-thrombin with an IC₅₀ of about 45 nM. In other embodiment, the protein inhibits in vitro α-thrombin generation as described in EXAMPLE 15. In addition, such activity is sensitive to salt concentration, as described in EXAMPLE 10, and shown in Table 2. In very particular embodiments, the biological activity includes any combination of the characteristics in this paragraph, or all of them. Anophelin gene: A gene which encodes a protein having anophelin biological activity.

The definition of an anophelin gene includes the various sequence polymorphisms that may exist in other species. Anophelin cDNA: The Anophelin cDNA is functionally defined as a cDNA molecule which encodes a protein having anophelin biological activity. The Anophelin cDNA is derived by reverse transcription from the mRNA encoded by the Anophelin gene and lacks internal non-coding segments and transcription regulatory sequences found in the Anophelin gene. Anophelin protein: The protein encoded by Anophelin cDNA. This protein may be functionally characterized by its biological ability as described above. Anophelin proteins include the full-length cDNA transcript (SEQ ID NO 3), as well as shorter peptides such as SEQ ID NOs 4 and 5, which retain Anophelin biological activity.

Anti-α-Thrombin Compounds: Compounds which inhibit α-thrombin activity, which can be determined using assays described in EXAMPLES 2, 7 and 9. cDNA (complementary DNA): A piece of DNA lacking internal, non-coding segments (introns) and regulatory sequences which determine transcription. cDNA is synthesized in the laboratory by reverse transcription from messenger RNA extracted from cells.

Chemical synthesis: The artificial means by which one can make a protein or peptide, for example as described in EXAMPLES 6 and 22.

Classical inhibition: An inhibitor that behaves according to the Michaelis Menten Equation.

Extracorporeal Blood: Blood which is outside of the body.

Fast inhibitor: When the enzyme-inhibitor complex formation is attained immediately, after the mixing of both the enzyme and the inhibitor.

HPLC purification and concentration: A method of purifying anophelin subsequent to its chemical synthesis (see EXAMPLES 6 and 22) recombinant synthesis (see EXAMPLE 18) or purifying anophelin from a salivary gland extract (see EXAMPLE 3).

Isolated: An "isolated" nucleic acid has been substantially separated or purified away from other nucleic acid sequences in the cell of the organism in which the nucleic acid naturally occurs, i.e., other chromosomal and extrachromosomal DNA and RNA. The term "isolated" thus encompasses nucleic acids purified by standard nucleic acid purification methods. The term also embraces nucleic acids prepared by recombinant expression in a host cell as well as chemically synthesized nucleic acids. K_J: Inhibition constant

Mimetic: A molecule (such as an organic chemical compound) that mimics the activity of a protein, such as the biological activity of anophelin. Peptidomimetic and organomimetic embodiments are within the scope of this term, whereby the three-dimensional arrangement of the chemical constituents of such peptido- and organomimetics mimic the three-dimensional arrangement of the peptide backbone and component amino acid side chains in the peptide, resulting in such peptido- and organomimetics of the peptides having substantial specific inhibitory activity. For computer modeling applications, a pharmacophore is an idealized, three-dimensional definition of the structural requirements for biological activity. Peptido- and organomimetics can be designed to fit each pharmacophore with current computer modeling software (using computer assisted drug design or CADD). See Walters, "Computer-Assisted Modeling of Drugs", in Klegerman & Groves, eds., 1993, Pharmaceutical Biotechnology, Interpharm Press: Buffalo Grove, IL, pp. 165-174 and Principles of Pharmacology (ed. Munson, 1995), chapter 102 for a description of techniques used in computer assisted drug design.

Oligonucleotide: A linear polynucleotide sequence of up to about 200 nucleotide bases in length, for example a polynucleotide (such as DNA or RNA) which is at least 6 nucleotides, for example at least 15, 50, 100 or even 200 nucleotides long. Operably linked: A first nucleic acid sequence is operably linked with a second nucleic acid sequence when the first nucleic acid sequence is placed in a functional relationship with the second nucleic acid sequence. For instance, a promoter is operably linked to a coding sequence if the promoter affects the transcription or expression of the coding sequence. Generally, operably linked DNA sequences are contiguous and, where necessary to join two protein coding regions, in the same reading frame.

ORF (open reading frame): A series of nucleotide triplets (codons) coding for amino acids without any termination codons. These sequences are usually translatable into a peptide.

Ortholog: Two nucleotide sequences are orthologs of each other if they share a common ancestral sequence and diverged when a species carrying that ancestral sequence split into two species. Orthologous sequences are also homologous sequences.

Pharmaceutically acceptable carriers: The pharmaceutically acceptable carriers useful in this disclosure are conventional. Remington 's Pharmaceutical Sciences, by E. W. Martin, Mack Publishing Co., Easton, PA, 15fh Edition (1975), describes compositions and formulations suitable for pharmaceutical delivery of the anophelin protein herein disclosed. In general, the nature of the carrier will depend on the particular mode of administration being employed. For instance, parenteral formulations usually comprise injectable fluids that include pharmaceutically and physiologically acceptable fluids such as water, physiological saline, balanced salt solutions, aqueous dextrose, glycerol or the like as a vehicle. For solid compositions (e.g., powder, pill, tablet, or capsule forms), conventional non-toxic solid carriers can include, for example, pharmaceutical grades of mannitol, lactose, starch, or magnesium stearate. In addition to biologically-neutral carriers, pharmaceutical compositions to be administered can contain minor amounts of non-toxic auxiliary substances, such as wetting or emulsifying agents, preservatives, and pH buffering agents and the like, for example sodium acetate or sorbitan monolaurate.

Platelet Aggregation: For example, as determined by the assay described in EXAMPLES 2 and 7.

Probes and primers: Nucleic acid probes and primers may readily be prepared based on the nucleic acids provided herein. A probe comprises an isolated nucleic acid attached to a detectable label or reporter molecule. Typical labels include radioactive isotopes, ligands, chemiluminescent agents, and enzymes. Methods for labeling and guidance in the choice of labels appropriate for various purposes are discussed, e.g. , in Sambrook et al. (Molecular Cloning: A

Laboratory Manual, Cold Spring Harbor, New York, 1989) and Ausubel et al. (Current Protocols in Molecular Biology , Greene Publishing Associates and Wiley-Intersciences, 1987).

Primers are short nucleic acids, for example DNA oligonucleotides 15 nucleotides or more in length. Primers may be annealed to a complementary target DNA strand by nucleic acid hybridization to form a hybrid between the primer and the target DNA strand, and then extended along the target DNA strand by a DNA polymerase enzyme. Primer pairs can be used for amplification of a nucleic acid sequence, e.g. , by the polymerase chain reaction (PCR) or other nucleic-acid amplification methods known in the art.

Methods for preparing and using probes and primers are described, for example, in

Sambrook et al. (Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, New York,

1989), Ausubel et al. (Current Protocols in Molecular Biology, Greene Publishing Associates and Wiley-Intersciences, 1987), and Innis et al. , (PCR Protocols, A Guide to Methods and

Applications, Innis et al. (eds.), Academic Press, Inc. , San Diego, California, 1990). PCR primer pairs can be derived from a known sequence, for example, by using computer programs intended for that purpose such as Primer (Version 0.5, ^® 1991, Whitehead Institute for Biomedical Research,

Cambridge, MA). Polynucleotide: A linear nucleic acid sequence of any length. Therefore, a polynucleotide includes molecules which are 15, 50, 100, 200 (oligonucleotides) and also nucleotides as long as a full length cDNA.

Promoter: An array of nucleic acid control sequences which direct transcription of a nucleic acid. A promoter includes necessary nucleic acid sequences near the start site of transcription, such as, in the case of a polymerase II type promoter, a TATA element. A promoter also optionally includes distal enhancer or repressor elements which can be located as much as several thousand base pairs from the start site of transcription.

Purified: The term purified does not require absolute purity; rather, it is intended as a relative term. Thus, for example, a purified anophelin protein preparation is one in which the anophelin protein is more pure than the protein in its natural environment within a cell. Preferably, a preparation of anophelin protein is purified such that the anophelin protein represents at least 50% of the total protein content of the preparation.

Recombinant: A recombinant nucleic acid is one that has a sequence that is not naturally occurring or has a sequence that is made by an artificial combination of two otherwise separated segments of sequence. This artificial combination is often accomplished by chemical synthesis or, more commonly, by the artificial manipulation of isolated segments of nucleic acids, e.g., by genetic engineering techniques. Salivary gland extract: The resulting supernatant after the removal, homogenization by sonication and centrifugation of salivary glands from A. albimanus mosquitoes, as described in EXAMPLE 1.

Sequence identity: The similarity between two nucleic acid sequences, or two amino acid sequences, is expressed in terms of the similarity between the sequences, otherwise referred to as sequence identity. Sequence identity is frequently measured in terms of percentage identity (or similarity or homology); the higher the percentage, the more similar are the two sequences. Methods of alignment of sequences for comparison are well-known in the art. Homologs or orthologs of nucleic acid or amino acid sequences will possess a relatively high degree of sequence identity when aligned using standard methods. This homology will be more significant when the orthologous proteins or nucleic acids are derived from species which are more closely related (e.g. , human and chimpanzee sequences), compared to species more distantly related (e.g., human and C. elegans sequences). Typically, orthologs are at least 50% identical at the nucleotide level and at least 50% identical at the amino acid level when comparing orthologous sequences. Methods of alignment of sequences for comparison are well known in the art. Various programs and alignment algorithms are described in: Smith and Waterman, Adv. Appl. Math. 2:482, 1981; Needleman and Wunsch, J. Mol. Bio. 48:443, 1970; Pearson and Lipman, Meth. Mol. Biol. 24: 307-31, 1988; Higgins and Sharp, Gene 73:237-44, 1988; Higgins and Sharp, CABIOS 5: 151-3, 1989; Corpet et al. , Nuc. Acids Res. 16: 10881-90, 1988; Huang et al , Comp. Appl. BioSci. 8: 155-65, 1992; and Pearson et al , Meth. Mol. Biol. 24:307-31 , 1994. Altschul et al, . J. Mol. Biol. 215:403-10, 1990, presents a detailed consideration of sequence alignment methods and homology calculations.

The NCBI Basic Local Alignment Search Tool (BLAST) (Altschul et al , J. Mol. Biol. 215:403-10, 1990) is available from several sources, including the National Center for Biological Information (NCBI, National Library of Medicine, Building 38A, Room 8N805, Bethesda, MD 20894) and on the Internet, for use in connection with the sequence analysis programs blastp, blastn, blastx, tblastn and tblastx. Additional information can be found at the NCBI web site.

Homologs of the anophelin protein are typically characterized by possession of at least 70 % sequence identity counted over the full length alignment with the disclosed amino acid sequence using the NCBI Basic Blast 2.0, gapped blastp with databases such as the nr or swissprot database set to default parameters. Queries searched with the blastn program are filtered with DUST (Hancock, and Armstrong, 1994, Comput. Appl. Biosci. 10:67-70). Other programs use SEG. Alternatively, one may manually align the sequences and count the number of identical amino acids. This number divided by the total number of amino acids in the reference sequence multiplied by 100 results in the percent identity.

For comparisons of amino acid sequences of greater than about 30 amino acids, the Blast 2 sequences function may be employed using the default BLOSUM62 matrix set to default parameters, (gap existence cost of 11, and a per residue gap cost of 1) When aligning short peptides (fewer than around 30 amino acids), the alignment may be performed using the Blast 2 sequences function, employing the PAM30 matrix set to default parameters (open gap 9, extension gap 1 penalties) Proteins with even greater similarity to the reference sequence will show increasing percentage identities when assessed by this method, such as at least 70%, at least 75%, at least 80%, at least 90%, at least 95%, at least 98%, or at least 99% sequence identity When less than the entire sequence is being compared for sequence identity, homologs will typically possess at least 75% sequence identity over short windows of 10-20 amino acids, and may possess sequence identities of at least 85% or at least 90% or 95% dependmg on their similarity to the reference sequence Methods for determining sequence identity over such short windows are described at the NCBI web site

One of ordinary skill in the art will appreciate that these sequence identity ranges are provided for guidance only, it is entirely possible that strongly significant homologs could be obtained that fall outside of the ranges provided The present invention provides not only the peptide homologs that are described above, but also nucleic acid molecules that encode such homologs

An alternative indication that two nucleic acid molecules are closely related is that the two molecules hybridize to each other under stringent conditions Stringent conditions are sequence- dependent and are different under different environmental parameters Generally, stringent conditions are selected to be about 5° C to 20° C lower than the thermal melting pomt (Tm) for the specific sequence at a defined ionic strength and pH The T_m is the temperature (under defined ionic strength and pH) at which 50% of the target sequence remains hybridized to a perfectly matched probe or complementary strand Conditions for nucleic acid hybridization and calculation of stringencies can be found in Sambrook et al ((1989) In Molecular Cloning A Laboratory Manual, CSHL, New York) and Tijssen ((1993) Laboratory Techniques in Biochemistry and Molecular Biology— Hybridization with Nucleic Acid Probes Part I, Chapter 2, Elsevier, New York) Nucleic acid molecules that hybridize under stringent conditions to an anophelin gene sequence will typically hybridize to a probe based on either an entire anophelin gene or selected portions of the gene under wash conditions of 2x SSC at 50° C A more detailed discussion of hybridization conditions is presented in Example 17

Nucleic acid sequences that do not show a high degree of identity may nevertheless encode similar amino acid sequences, due to the degeneracy of the genetic code It is understood that changes in nucleic acid sequence can be made using this degeneracy to produce multiple nucleic acid molecules that all encode substantially the same protein

Such homologous peptides may, for example, possess at least 75% , 80% , 90%, 95% , 98% , or 99% sequence identity determined by this method When less than the entire sequence is bemg compared for sequence identity, homologs may, for example, possess at least 75% , 85 %

90%, 95% , 98% or 99% sequence identity over short wmdows of 10-20 ammo acids Methods for determining sequence identity over such short windows can be found at the NCBI web site One of skill m the art will appreciate that these sequence identity ranges are provided for guidance only, it is entirely possible that strongly significant homologs or other variants could be obtained that fall outside of the ranges provided.

The disclosure provides not only the peptide homologs that are described above, but also nucleic acid molecules that encode such homologs. An alternative (and not necessarily cumulative) indication that two nucleic acid sequences are substantially identical is that the polypeptide which the first nucleic acid encodes is immunologically cross reactive with the polypeptide encoded by the second nucleic acid.

Nucleic acid sequences that do not show a high degree of identity may nevertheless encode similar amino acid sequences, due to the degeneracy of the genetic code. It is understood that changes in nucleic acid sequence can be made using this degeneracy to produce multiple nucleic acid sequences that all encode substantially the same protein.

Slow inhibitor: When the enzyme-inhibitor complex formation is attained after a period of minutes, for example 3-10 minutes, after mixing of the enzyme and inhibitor.

Subject: Living multicellular vertebrate organisms, a category which includes, both human and veterinary subjects for example, mammals and birds.

Therapeutically Effective Amount: An anti-thrombotic concentration of anophelin, for example an amount that is effecitve to inhibit or reduce platelet aggregation in a subject to whom it is administered. In particular detailed examples, it is an amount required to inhibit α-thrombin, platelet aggregation and/or blood clotting as described in EXAMPLES 2 and 7. Such inhibition will decrease (inlcuding preventing) blood clotting and platelet aggregation in a patient.

The therapeutically effective amount also includes a quantity of anophelin protein sufficient to achieve a desired effect in a subject being treated. For instance, this can be the amount necessary to inhibit α-thrombin or to measurably decrease platelet aggregation and/or blood clotting mechanisms. In general, this amount will be sufficient to measurably inhibit platelet aggregation and/or blood clotting

An effective amount of anophelin may be administered in a single dose, or in several doses, for example daily, during a course of treatment. However, the effective amount of anophelin will be dependent on the source of anophelin applied (i.e. anophelin isolated from an extract versus a chemically synthesized and purified anophelin, or a variant or fragment that may not retain full anophelin activity), the subject being treated, the severity and type of the condition being treated, and the manner of administration of anophelin. For example, a therapeutically effective amount of anophelin can vary from about 0.01 mg/kg body weight to about 1 g/kg body weight.

The anophelin protein disclosed herein has equal application in medical and veterinary settings. Therefore, the general term "subject being treated" is understood to include all animals (e.g. humans, apes, dogs, cats, horses, and cows) that require anti-thrombin activity that is susceptible to anophelin-mediated inhibition. Therapeutically effective dose: A dose sufficient to decrease α-thrombin activity, or to cause a decrease in platelet aggregation and/or blood clotting resulting in a regression of a pathological condition, or which is capable of relieving signs or symptoms caused by the condition, such as angina, claudication, myocardial infarction, ischemia due to peripheral vascular disease (such as diabetic vascular insufficiency), or transient ischemic attacks caused by clot formation in the central nervous system, associated with blood-clot formation.

Thrombin activity: The activity of thrombin which results in blood clot formation, α- thrombin activity can be determined using assays described in EXAMPLES 2, 7 and 9.

Tight inhibition: High affinity of an enzyme inhibitor, such as anophelin, for a substrate, such as α-thrombin. Enzymes inhibitors with a K, < 10 nM, for example 1 nM or less, as determined in EXAMPLE 9, are considered to be tight inhibitors. When the concentration of enzyme used in the assay described in EXAMPLE 9 is 100 times larger than the calculated K, value, this is indicative of a tight inhibitor.

Transformed: A transformed cell is a cell into which has been introduced a nucleic acid molecule by molecular biology techniques. As used herein, the term transformation encompasses all techniques by which a nucleic acid molecule might be introduced into such a cell, including transfection with viral vectors, transformation with plasmid vectors, and introduction of naked DNA by electroporation, lipofection, and particle gun acceleration.

Variants or fragments: Anophelin proteins which contain either variant amino acid sequences, and/or a fragment of the full-length anophelin protein. Variant anophelin proteins have an amino acid sequence which varies from the amino acid sequence of anophelin as disclosed herein. For example, variant anophelin proteins, can have at least 70% , 75% , 80% , 90%, 95% , 98% , or 99% sequence identity to anophelin. Fragments of anophelin protein contain a portion of the full-length anophelin protein disclosed herein, or variants thereof (such as fragments containing one or more conservative substitutions). Examples of anophelin fragments are shown in, but not limited to, SEQ ID NOs 4-8. Additional guidance about making variants is provided in Example 5 and FIG. 5B, which shows the highly conserved regions of homologous proteins.

In particular examples, variants and fragments are at least 50 amino acid residues in length, for example at least 59 or 61 residues in length. Vector: A nucleic acid molecule as introduced into a host cell, thereby producing a transformed host cell. A vector may include nucleic acid sequences that permit it to replicate in a host cell, such as an origin of replication. A vector may also include one or more selectable marker genes and other genetic elements known in the art.

This disclosure provides a particular nucleotide sequence of the Anopheles albimanus mosquito Anophelin cDNA, which is depicted in SEQ ID NO 1. The Anophelin cDNA contains an ORF (SEQ ID NO 2) which encodes a protein of 83 amino acids. This 83 amino acid protein appears to contain a signal peptide at its N-terminus. The amino acid sequence of anophelin is also part of this disclosure and is depicted in SEQ ID NOs 3-5. The mature peptide is predicted to contain 61 amino acids (SEQ ID NO 4) or 59 amino acids (SEQ ID NO 5). Variants and fragments may include any of these sequences, or subsequences (including variants) thereof.

EXAMPLE 1 Insect Rearing and Generation of Salivary Gland Extract This example describes how mosquitoes were reared and how their salivary glands were homogenized to generate a salivary gland extract. Anopheles albimanus mosquitoes (Santa Tecla strain) were reared at 27°C and 80% relative humidity. Adult mosquitoes were offered cotton swabs containing 10% Karo syrup (CPC International Inc. Englewood Cliffs, NJ). Salivary glands from female mosquitoes at least three days old were dissected in groups of 20 pairs in 20 μl of phosphate buffered saline (10 mM sodium phosphate at pH 7.0 with 150 mM NaCl) and kept at -75°C until needed. The salivary glands were homogenized by ultrasound with a Branson sonifier (model 450) with the probe immersed 2 cm in a 100 ml beaker containing 80 ml of water at room temperature (RT). The 1.5 ml conical tube containing the glands was held with clamping forceps so that its conical tip was just under the tip of the probe. The power was set at six and a 50% cycle was run for one minute. Disruption of the glands was assessed under a stereoscope, and a new cycle was repeated if some of the glands appeared intact. The homogenate was centrifuged for two minutes at 10,000 g and the supernatant was recovered for use in the assays described below. This salivary gland extract was used for purification of the salivary anti-α-thrombin protein anophelin (EXAMPLE 3) and for the generation of a cDNA library (EXAMPLE 5). For cDNA library construction, pools of female salivary glands were obtained at the day of adult emergence and at one day following emergence.

EXAMPLE 2 Platelet Aggregation Assay This example describes experiments which measure the amount of platelet aggregation inhibition induced by the anti-α-thrombin activity in the A. albimanus salivary gland extract prepared in EXAMPLE 1. This assay demonstrates the anti-platelet anti-thrombotic activity of the protein, and is an excellent assay for screening fragments and variants for retention of activity.

Briefly, 50 μl of HEPES saline (10 mM HEPES pH 7.4, 150 mM NaCl) was mixed in 96- well flat bottom plates (Falcon 3912, Beckton and Dickinson, Oxnard, CA) in the presence of thrombin (2.5 U/ml) which serves as an agonist of platelet aggregation, the peptide GPRP amide (1 mM) which inhibits fibrin polymerization, and the salivary extract generated in EXAMPLE 1 (0.03, 0.12 or 0.24 salivary gland pairs). Platelet aggregation was initiated by the addition of 50 μl of human citrated (0.38%) platelet rich plasma. The plate was stirred on a microplate mixer (Cole Palmer Series 4732, Vernon Hills, IL) for five seconds before being transferred to the microplate reader (Thermomax, Molecular Devices, Menlo Park, CA) where the samples were read at 650 nm. Salivary gland apyrase enzyme inhibits ADP (adenosine diphosphate) activity and thus inhibits α-thrombin activity and may inhibit platelet aggregation. Therefore, the presence of apyrase in the salivary gland extract may interfere with the interpretation of the results of the platelet aggregation assay. To ensure that platelet aggregation inhibition was not due to the salivary apyrase, but instead due to the anti-α-thrombin activity of the salivary extract, an excess of potato apyrase (0.8 mg/ml) was added to the reaction. The results shown in FIG. 1 demonstrate that in the presence of ADP (2 μM) and excess apyrase (FIG. 1, ADP + Apyrase), platelet aggregation did not occur. Therefore, the α-thrombin-induced platelet aggregation observed in this assay is independent of the ADP pathway.

Under the assay conditions described above, α-thrombin-induced inhibition of platelet aggregation was observed in the presence of 0.03 homogenized salivary gland pairs (each pair of glands has approximately 1 μg of total protein), and complete inhibition was observed with 0.24 salivary gland pairs per 0.1 ml assay (FIG. 1). Inhibition of α-thrombin was also observed with the salivary gland extract using the chromogenic assay, fibrinogen assay and recalcification assay as described below in EXAMPLE 7. These results indicate that salivary gland extracts of A. albimanus contains a potent inhibitor of α-thrombin-induced platelet aggregation.

EXAMPLE 3 Purification of A. albimanus Salivary Anti-α-Thrombin

This example describes how a protein responsible for the inhibition of α-thrombin-induced platelet aggregation in EXAMPLE 2, was isolated from salivary gland extracts of A. albimanus mosquitoes.

A. albimanus salivary gland homogenate (1,000 salivary gland pairs, EXAMPLE 1) was separated by molecular sieving HPLC, followed by reverse-phase HPLC. Chromatographic protocols were performed using a CM4100 pump and a SM4100 dual wavelength detector (Thermo Separation Products, Riviera Beach, FL). Molecular sieving HPLC was performed using an TSK 2000 SW column (600 x 7.5 mm) with 10 mM HEPES at pH 7.0 and 150 mM NaCl at a flow rate of 1 ml/min. Eluates were monitored at 220 and 280 nm. Fractions were collected at 0.4 minute intervals (FIG. 2 A) and tested for anti-thrombin activity using the chromogenic assay as described in EXAMPLE 7 (FIG. 2B). Active (anti-thrombin) fractions were pooled and injected into a reverse phase, non- porous, polymer based column (PRP-infinity, Hamilton, USA), and eluted with a gradient from 10% to 60% acetonitrile, 0.1 % trifluoroacetic acid in 60 minutes at a flow rate of 0.5 ml/min. The eluent was monitored at 220 nm. Fractions were collected at one minute intervals. This resulted in the separation of three major peaks (FIG. 3A). An aliquot of each fraction was dried in the presence of 10 μl bovine serum albumin (BSA) (1 mg/ml), resuspended in 30 μl of HEPES saline buffer (pH 7.0) and tested for anti-α-thrombin activity using the assays described in EXAMPLE 7. The 220 nm absorbing peak eluting at minute 27 (FIG. 3 A) inhibited α-thrombin activity in a chromogenic assay (FIG. 3B) and inhibited α-thrombin-induced platelet aggregation with approximately 0.74 ng peptide (FIG. 3C). Fractions rich in anti-thrombin activity also inhibited α- thrombin in a fibrinogen assay, delayed the recalcification time of human citrated plasma and inhibited α-thrombin induced platelet aggregation (not shown) (see EXAMPLES 2 and 7 for methods).

EXAMPLE 4 Peptide Sequencing of the A. albimanus Salivary Anti-α-Thrombin Protein

This example describes how a partial amino acid sequence of the purified protein obtained in EXAMPLE 3, was obtained.

Mass spectroscopy of the purified material obtained in EXAMPLE 3, resulted in a peak of 6342.4 Da (FIG. 4). Attempts at N-terminal sequencing of the protein using Edman degradation were unsuccessful. Therefore, the purified anti-thrombin protein was enzymatically cleaved with Asp-N. From this digestion, three internal peptides were obtained: DPGRRLGEGSKP (SEQ ID NO 6), TFNT (SEQ ID NO 7), and DKLVENN (SEQ ID NO 8).

EXAMPLE 5 Cloning of the A. albimanus Salivary Anti-α-Thrombin Protein

This example describes how an A. albimanus salivary anti-α-thrombin protein, herein called anophelin, was cloned using the peptide sequence obtained in EXAMPLE 4.

Preparation of an A. albimanus Salivary Gland cDNA Library

A. albimanus salivary gland mRNA was isolated from 260 gland pairs using a Micro- FastTrack mRNA isolation kit as described in the manufacturer's instructions (Invitrogen, San Diego, CA). This yielded approximately 250 ng of poly(A)+ mRNA. A PCR-based cDNA library was generated from the poly( A) + RNA following the instructions for the SMART cDN A library construction kit (Clontech, Palo Alto, CA).

The mRNA was reverse transcribed to cDNA using Superscript II RNase H^" reverse transcriptase (GIBCO-BRL, Gaithersburg, MD) and the CDS/3 ' primer (Clontech) for one hour at 42°C. The complementary strand was obtained using a PCR-based protocol using the SMART primer (Clontech) as the sense primer and the CDS/3' primer as anti-sense primer using a Perkin Elmer 2400 Thermal cycler and Klen-Taq DNA polymerase (Clontech) under the following conditions: 94°C for two minutes; 22 cycles of 94°C for 15 seconds and 68°C for five minutes. EcoRI adapters were ligated to the obtained cDNA. The cDNA was fractionated using columns provided by the manufacturer (Clontech). Fractions containing cDNA molecules longer than 400 base pairs were pooled and ligated into the Lambda-ZAP II vector (Stratagene, La Jolla, CA). The unamplified library obtained had a complexity of 5.7 x 10⁶ recombinants.

Cloning Anophelin by PCR

For PCR cloning of anophelin, mRNA from 60 pairs of A. albimanus salivary glands were isolated, reverse transcribed and PCR amplified to generate the complementary strand, as described above. To obtain the partial DNA sequence of the A. albimanus anti-thrombin protein, cDNA obtained by PCR amplification containing the SMART sequence was used as a template for the PCR reaction. The primers used in this reaction were the 5 ' primer that recognizes the SMART sequence (Clontech) and primers designed from two internal peptides obtained by Asp-N digestion of the purified anti-thrombin. 5 '- TT(AG) TT(TC) TC(ATCG) AC(I) A(AG)(I) TT(AG) TC- 3 ' (SEQ ID NO 9) and 5 '- GG(TC) TT(I) (GC)(AT)(I) CC(TC) TC(I) CC(I) A(AG)- 3 ' (SEQ ID NO 10). PCR amplification was performed under the following conditions: one minute at 95°C; 5 cycles of one minute at 94°C, 30 seconds at 40°C, 45 seconds at 68°C; and 20 cycles of one minute at 94°C, 30 seconds at 45°C, 45 seconds at 68°C.

The resulting PCR products were separated on a 1.0 % agarose gel, excised and purified using the Sephaglas Bandprep Kit (Amersham Pharmacia Biotech Inc. , Piscataway, NJ ), and cloned into the PCRscript vector (Stratagene) using the PCRscript cloning system (Stratagene). Competent bacterial cells were transformed following the manufacturer's protocol. Resulting white colonies were isolated and grown overnight in Luria broth containing ampicillin (100 μg/ml) at 37°C. Plasmids from two independent clones were isolated using the Wizard Miniprep kit (Promega, Madison, WI), sequenced using dye terminator reactions (DNA sequencing kit #402079, Perkin Elmer Applied Biosystems, Foster City, CA) and analyzed by an automated ABI sequencer (ABI prism, 377 DNA sequencer, Perkin Elmer) all according to the manufacturer's instructions.

After confirming that the sequence of the PCR product contained the predicted sequence of the internal peptides of the Anopheles anti-thrombin (EXAMPLE 4), the PCR insert was digested from the plasmid with EcoRI, gel purified and cleaned as described above. The purified PCR insert was labeled with dUTP-digoxigenin using specific forward and reverse primers with the following PCR conditions: 75°C for five minutes; 94°C for two minutes; 25 cycles of one minute at 94°C, 1.5 minutes at 42°C, one minute at 72°C; and five minutes at 72°C. The reaction mixture included the PCR insert as a template, 2.5 mM MgCl₂, 50 mM KC1, 10 mM Tris pH 8.3, 0.01 % gelatin, 0.2 mM of each dNTP, DNA labeling mix (Genius system; Boehringer Mannheim, Indianapolis, IN), and 2 units (U) Ampli-Taq polymerase (GIBCO-BRL). The resulting 300-bp PCR clone labeled with dUTP-digoxigenin was used to screen the A. albimanus salivary gland cDNA library generated above. Phage plaques were lifted with a Hybond-N nylon membrane (Amersham, Arlington Heights, IL) and hybridized with the digoxigenin-labeled PCR probe using the plaque hybridization protocol of the Genius system (Boehringer Mannheim). Positive plaques were picked and plated again for a secondary screening. Well-isolated positive plaques were selected, and the phagemid carrying the peroxidase clone was isolated from the phage using the in vivo excision protocol from the UNI-ZAP vector manual (Stratagene).

White colonies that originated from the phagemid excision protocol were isolated and grown overnight in Luria broth containing ampicillin (100 μg/ml) at 37°C. Plasmid isolation was performed using the Wizard Miniprep kit (Promega). The insert of the isolated plasmid was sequenced as described above using the M 13 and M13 reverse primers.

Sequence Analysis Analysis of the predicted protein sequence was performed using the BLAST programs

(Altschul et al., 1997, Nucleic Acids Res. 25:3389-3402), and the Sequence analysis services programs which can be found at the NCBI web site.

To obtain full sequence information of the salivary anti-thrombin of A. albimanus, the amino acid sequence of the internal peptides (SEQ ID NOs 6-8 and EXAMPLE 4) were used to design oligonucleotide primers for a PCR reaction, using as a template cDNA of A. albimanus salivary glands. A single PCR product of 300 base pairs (bp) was obtained and its sequence contained the sequence of the three internal peptides obtained with Asp-N digestion of the purified anti-thrombin (EXAMPLE 4). The PCR product was then labeled by digoxigenin and used to screen the A. albimanus salivary gland cDNA library described above. A positive clone (AlbieAT) of 484 bp in length was obtained and sequenced (SEQ ID NO 1).

The AlbieAT cDNA clone contains an open reading frame of 249 bp that codes for a protein of 83 amino acids (FIG. 5 A and SEQ ID NOs 2 and 3, respectively). This sequence was deposited into GenBank under accession number AF 125095, and is herein called anophelin. The sequences of all three internal peptides of A. albimanus anti-thrombin were represented in the deduced protein (FIG. 5 A, underlined amino acids). The first 22 amino acids were predicted to be the signal peptide using the SignalP program (Nielsen et al. , Protein. Eng. 10: 1-6, 1997), and the remaining 61 amino acids (SEQ ID NO 4) to constitute the mature protein. Analysis of the predicted processed protein indicated a molecular mass of 6,538.74 Da and an acidic isoelectric point of 3.52 with minus 13.07 charge units at pH 7.0. There are 17 strongly acidic amino acids in the sequence: 10 aspartic acids and 7 glutamic acids. These two amino acids represent one third of the total amino acids of the protein. A comparison of the protein AlbieAT sequence using the non-redundant protein data base at NCBI (Befhesda, MD) using the gapped blastp program found homology with two hypothetical proteins from cDNA clones of Anopheles gambiae salivary gland: cE5 protein (Accession number Y17717; SEQ ID NO 12) and FI (Accession number AJ000038; SEQ ID NO 13). Alignment of the A. albimanus anti-thrombin sequence with cE5 and FI sequences from A. gambiae (FIG. 5B) and comparison of their predicted pi (A. albimanus: 3.52; cE5: 4.04; FI : 4.05), suggest that these two hypothetical salivary proteins are anti-α-thrombins from A. gambiae. The alignment shows highly conserved regions at the predicted N-terminal site (APQYA, SEQ ID NO 11), conserved negatively charged amino acids (D₈, D₁₃, E_u, D₁₈, D_3I, E₄₃) and a conserved arginine (R₅₃) at the carboxy-terminal region. This sequence homology provides very helpful information in designing variants and fragments of anophelin, because it provides guidance about the highly conserved regions of the protein where substitutions are likely to have more of an effect on biological activity.

Although there are no obvious sequence analogies between hirudin and anophelin, both peptides are rich in negatively charged amino acids. However, hirudin has a higher density of negatively charged amino acids on the carboxy-terminal region, while anophelin's amino-terminal region has a higher negative-charge density. In the case of hirudin, these negatively charged residues are important to interact with thrombin' s anion-binding exosite (a positively charged cleft in the thrombin molecule, near the active site, where part of the fibrinogen substrate fits).

EXAMPLE 6 Chemical Synthesis of Anophelin

This example describes how the predicted active anophelin peptide of 61 amino acids (SEQ ID NO 4) was chemically synthesized and purified. These same techniques can also be extended to synthesize biologically active variants and fragments. The measurement of human plasma clotting activity, chromogenic assay, and other assays disclosed in this Example, are excellent examples of convenient assays that may be used to screen for biologically active fragments and variants, as well as mimetics.

To confirm the AlbieAT cDNA clone (EXAMPLE 5) was responsible for the anti-α- thrombin activity observed in EXAMPLE 2 (since the sequence of anophelin was not similar to other known anti-α-thrombin proteins, or to any other proteins with known function in the data bases searched) a peptide with sequence based on the predicted mature product of AlbieAT cDNA was synthesized. Peptide synthesis was performed at the Peptide Synthesis Laboratory, Structural biology section, NIAID (Rockville, MD). A 61 amino acid peptide (SEQ ID NO 4) was synthesized with the inclusion of an amide linked to the proline at the carboxy-terminal end. The synthetic peptide was subjected to mass spectroscopy to verify its size and to reverse-phase HPLC for cleaning and concentration of the sample. The MALDI spectra of the synthetic peptide, indicating a main ion of 6,540 (Expected: 6,539 + H⁺ = 6,540 Da) is shown in FIG. 6. Impurities of lower molecular mass may be due to the lack of addition of Asp or Glu or Ile/Leu, as indicated by the contaminants of masses 6,426.5 and 6,298.6. HPLC fractionation of the synthetic product showed a single major peak and two minor impurities (less than 5 % total area) with molecular masses corresponding to the acid hydrolysis of the Asp-Pro bond between amino acids 50 and 51.

The discrepancy between the molecular mass obtained from the native antithrombin (6,342.2 Da, FIG. 4) and the predicted mass of the native peptide resulting from the albieAT cDNA (6,538 Da, FIG. 6) can be explained by a post-translational modification of the protein. It is likely that the first amino acid of the secreted protein is glutamine, the third amino acid on the predicted mature peptide. Therefore, the mature peptide may only contain 59 amino acids (SEQ ID NO 5). Glutamine can be converted to pyroglutamic acid (Abraham and Podell, Mol. Cell. Biochem. 38: 181-90, 1981), which would block the peptide sequence. This would explain the inability to perform Edman degradation on the native peptide (EXAMPLE 4). The predicted mass of the 59 amino acid peptide (SEQ ID NO 5) would be 6370.55, still 28.35 mass units above the value of 6,342.2 found for the native peptide. The 28 mass difference could result from a single formylation of an amino acid residue. This represents a 0.4% discrepancy. Because the resolution for externally calibrated MALDI analysis is on the order of 0.25 % , there may be some other modification of the native molecule. However, as shown in the following EXAMPLES, the 61 amino acid synthetic anophelin is a potent anti-α-thrombin protein, and therefore has similar biological activity as native anophelin.

EXAMPLE 7 Functional Analysis of Synthetic Anophelin This example describes assays used to confirm that the synthetic anophelin peptide generated in EXAMPLE 6, functions as an α-thrombin inhibitor in the same manner as observed with the salivary extract (EXAMPLE 2).

The synthetic anophelin generated in EXAMPLE 6 (SEQ ID NO 4) was reconstituted in 10 mM HEPES saline buffer and injected into a molecular sieving HPLC column. Anophelin concentration was estimated by measuring protein absorbance at 280 nm (Perkin-Elmer, UV/VIS spectrometer Lambda 18). Chromatographic conditions were as described above in EXAMPLE 3 for the purification of the native protein. Eluted fractions were tested for anti-α-thrombin activity and the amount of protein with anti-α-thrombin activity was estimated by measuring the area under the absorbance/time graphs standardized with bovine serum albumin. Synthetic peptide was tested as an anti-α-thrombin molecule on a chromogenic assay, fibrinogen assay, recalcification time assay, and a platelet aggregation assay as described below. All data were analyzed by Jandel Sigma-Stat 2.0 statistical software (Jandel Corp.) and are reported as means ± SE. Measurement of human plasma clotting activity

Blood-clotting activity was measured by the recalcification time of human citrated plasma using a Thermomax microplate reader. Briefly, 30 μl of citrated human platelet poor plasma, 30 μl of HEPES saline (10 mM HEPES pH 7.4, 150 mM NaCl) and synthetic anophelin (0, 60, 120, and 240 nM) were mixed in 96-well flat bottom plates (Falcon 3912, Beckton and Dickinson, Oxnard, CA) for two minutes at 37°C, followed by addition of 30 μl of 25 mM CaCl₂ (8.3 mM final). The plate was continually mixed and maintained at 37°C, and absorbance readings at 650 nm were taken at 11 second intervals. A fast and sharp increase in the absorbance after a lag phase indicates clotting has occurred. The length of time taken for reaching a 0.06 or 0.03 absorbance value (onset O.D.) was chosen as a measure of clotting (recalcification) time.

Chromogenic Assay

Cleavage of the chromogenic substrate benzoyl-Phe-Val-Arg-pNA (Calbiochem, San Diego, CA) by α-thrombin (Calbiochem) was measured spectrophotometrically at 405 nm on a

Thermomax microplate reader (see EXAMPLE 2). Briefly, 10 μL of α-thrombin (20 nM, 10 nM, or 5 nM) and various concentrations of anophelin (see FIGS, for amounts added) was mixed with 60 μL of buffer (10 mM HEPES pH 7.4, 150 mM NaCl, 200 μg/ml BSA) and the mixture pre- incubated for two minutes at 37°C. The chromogenic substrate (20 μl of a 0.5 mg/ml solution) was added to the mixture and the sample was read at 405 nm with the temperature controlled at 37°C . Anophelin specificity was tested by a 10 minute incubation of anophelin with different enzymes at 37°C, diluted in buffer (10 mM HEPES pH 7.4, 150 mM NaCl, 200 μg/ml BSA), except when indicated otherwise. Enzyme and substrate concentrations were as noted in Table 1. Factor Xa, trypsin, and chymotrypsin activities were detected by addition of 200 μM chromogenic substrate (Chromogenix; Boehringer Mannheim Co. , Indianapolis, IN). Activated protein C (aPC) activity was started by addition of 600 μM chromogenic substrate for aPC (Calbiochem). Plasmin and elastase activity were tested by addition of 200 μM Val-Leu-Arg-p-Na (Sigma Chemical Co.) or chromogenic substrate for elastase (Calbiochem), respectively. Reptilase activity (βothrops atrox thrombin-like enzyme; Diagnostica Stago, France) was assayed by addition of 250 μM S- 2238 to 0.3125 BU (batroxobin units)/ml of enzyme. Papain (Calbiochem) was diluted to 0.2 mg/ml in PBS containing 3 mM DTT and 2 mM EDTA, followed by addition of 200 μM chromogenic substrate for papain (Calbiochem). To test the effects of anophelin on factor IXa activity, factor Xa generation by intrinsic Xase complex was performed with Coatest factor VIII (Chromogenix, Sweden), according to manufacturer's instructions, except that factor VIII (monoclonal antibody affinity purified, Baxter, CA) at 1 : 15000 dilution was used instead of plasma. Fibnnogen Assay

The activity of α-fhrombin on fibrinogen was measured by mixing 10 μl α-thrombin (20 nM, 10 nM, or 5 nM) with 30 μl of 10 mM HEPES buffer pH 7 0 The addition of 60 μl of fibrmogen (Sigma, St Louis, MO) (2 mg/ml) started the assay Factor Xa, trypsin and activated protein C activities were determmed with a 10 minute incubation of anophelin with each enzyme (see Figures for concentrations used) m HEPES-buffer, pH 7 4, followed by addition of 600 μM chromogenic substrate for Factor Xa or trypsin (Chromogenix, Boehrmger Mannheim Co , IN) or 640 μM chromogemc substrate specific for activated protein C (Calbiochem) The activity of α- thrombin on fibrmogen was measured spectrophotometπcally at 405 nm on a microplate reader at 37°C This measures the turbidity increase following formation of fibrin clot

Platelet Aggregation Assay

Platelet rich plasma was incubated with 0-4 5 nM synthetic anophelin and platelet aggregation initiated with 0 83 nM of thrombin The reaction was measured as described in EXAMPLE 2

Synthetic anophelin doubled the recalcification time of human citrated plasma when added in the range of 250 nM (FIG 7A) and inhibited α-thrombin induced platelet aggregation in the range of 1 nM (FIG 7B) The need for a larger concentration of peptide required to inhibit the recalcification time of plasma may be due to the 'explosive' formation of thrombin following Factor X activation Additionally, the synthetic anophelin displayed anti-α-fhrombin activity on a chromogemc substrate assay in the range of 0 6 nM (FIG 8, squares), and on the fibrmogen assay in the range of 0 2 nM (FIG 8, circles), m the nominal presence of 1 05 nM of thrombin Synthetic anophelin had no effect on platelet aggregation induced by ADP (10 μM), collagen (10 μg/ml) and the thromboxane analog U46610 (1 4 μM) when used at a concentration of 9 nM (data not shown), indicating that the inhibition observed in the platelet aggregation assay is due to its activity on the thrombin pathway

To determme whether anophehn was a tight inhibitor of α-fhrombin, the activity of α- fhrombin at 0 52 nM, 1 05 nM and 2 1 nM, as a function of the concentration of anophelin, was measured usmg the chromogenic assay The resulting curve (FIG 9) shows a parallel mcrease in the doses of anophehn needed to give the same inhibition of α-thrombin Plottmg the data as the inhibition of α-fhrombin against the concentration of anophelin divided by the concentration of α- fhrombin (FIG 9, mset), the lmes overlap, indicatmg that the concentration of enzyme is more than 100 times larger than the K, value which is indicative of a tight inhibitor The specificity of anophelin to thrombm is mdicated by its inability to inhibit a number of serme proteases mcludmg activated factor X, activated factor IXa (detected by factor Xa generation by intrinsic Xase), activated protem C, trypsin, chymotrypsin, neutrophil elastase, and plasmin, even at high concentrations (FIG. 10 and Table 1). In addition, anophelin does not affect the proteolytic activity of reptilase (a thrombin-like enzyme from Bothrops atrox) or the thiol-protease activity of papain (Table 1). Anophelin (0-1000 nM; 2 μM for Table 1) was incubated with 2 nM α-thrombin, 250 nM chymotrypsin, 12.8 nM factor Xa, 64 nM activated protein C IXa (intrinsic Xase), 64 nM activated protein C, 0.3125 batroxobin unit (BU)/mL of reptilase, 0.02 unit/mL plasmin, 0.2 mg/mL papain, 10 nM neutrophil elastase, or 0.66 nM trypsin for 10 minutes at 37°C, before addition of chromogenic substrate specific for each enzyme. Reactions were followed for 15 minutes and the effects of anophelin estimated by setting the initial velocity obtained in the presence of enzyme alone (without inhibitor) as 100% .

Table 1: Specificity of Anophelin to Thrombin

*Enzyme activities in the absence of inhibitor were set as 100% . Data are the mean ± SE of triplicate experiments.

Any one or more (or all) of these specificity characteristics can be used to identify particular embodiments of biologically active anophelin. For example, a residual activity of less than about 50% only for thrombin, but not for the other enzymes listed in Table 1 , can be used as an identifier of some variants or fragments of anophelin. In particular embodiments, a residual activity of less than 10% for thrombin, but greater than 90% for the other enzymes in Table 1, would be an indication of a fragment or variant with highly specific activity. EXAMPLE 8

Nondenaturating Gel Electrophoresis This example describes the use of nondenaturating gel electrophoresis to measure the formation of complexes between anophelin and other proteins. As demonstrated in EXAMPLE 7, the particular embodiment of the anophelin in that example behaves in vitro as a tight α-thrombin inhibitor with a Kj of ^" 100 pM. To investigate the mechanism of α-fhrombin inhibition by the anophelin synthesized in EXAMPLE 6 (SEQ ID No 4), kinetic and biochemical assays described in the examples below were conducted.

To study the direct interaction of enzyme and inhibitor, complex formation of anophelin and various proteins (α-thrombin, γ-fhrombin, prothrombin, Factor X, and Factor Xa) was analyzed by polyacrylamide gel electrophoresis under nondenaturating conditions. To detect complex formation, anophelin (4.5 μM, final concentration) was preincubated for 30 minutes at 37°C, with increasing concentrations of α-thrombin (1.38-8.3 μM, final concentrations) in 50 mM HEPES, pH 7.4, forming a total volume of 30 μl. Aliquots (0.5 μl) of α-thrombin were taken before and after addition of anophelin and diluted in 1000 μl of 50 mM HEPES, BSA 0.5% , pH 7.4. A fraction of this sample (90 μl) was taken to detect residual α-fhrombin activity, by addition of 10 μL of S-2238 (500 μM, final concentration). Reactions were followed for 10 minutes, and α- thrombin inhibition was estimated according to a decrease in the initial velocity of α-thrombin activity. The remaining sample, 29 μl, was applied to 4-20% precast polyacrylamide gels. Electrophoresis was performed using a NOVEX Powereasy500 apparatus; the migration buffer consisted of 68.5 mM Tris at pH 8.8. In some experiments, anophelin-α-fhrombin complexes were studied under both denaturing and reducing conditions. Protein complexes were detected by staining with Coomassie Brilliant Blue and destained in 15 % methanol, 10% acetic acid. Gels were scanned (Hewlett-Packard Scanjet 4p), and densitometry of bands was performed to quantify complex formation.

Complex formation and the disappearance of the band corresponding to anophelin were detected by nondenaturing gel electrophoresis (FIG. 11 A, inset) and quantified by band densitometry (FIGS. 11A and 11B). The area corresponding to anophelin was plotted against different enzyme/inhibitor molar ratios (FIG. 11B, inset, left y axis, closed circles), and the detection of the residual catalytic activity of α-thrombin was performed using a chromogenic assay (FIG. 11B, inset, right y axis, open triangles).

FIG. 11 A, and inset, demonstrates that this anophelin protein (referred to as anophelin in this Example)(4.5 μM) is stained as a fast migrating protein (lane 2), whereas α-fhrombin (8.3 μM) behaves as a slow-speed migrating protein, in the absence of inhibitor (lanes 1 and 7). In the presence of 1.26 and 2.76 μM anophelin (FIG. 11 A, lanes 3 and 4, respectively), α-thrombin migrates as a broad band of faster-speed migrating behavior than α-thrombin, whereas anophelin (4.5 μM), which is in excess, can be detected as a single band (FIGS. 11A and 11B, inset). These results demonstrate that α-fhrombin is complexed with anophelin. At this enzyme/inhibitor molar ratio, the catalytic activity of α-thrombin is almost completely blocked (FIG. 11B, inset). Incubation of 4.5 μM anophelin with 4.5 μM α-thrombin resulted in a broad band with a fast migration pattern (FIG. 11 , lane 5), together with an almost complete disappearance of anophelin (FIGS. 11A and 11B, insets) and more than 95% inhibition of α-thrombin catalytic activity (FIGS. 1 IB, inset). Lane 6 demonstrates that when an excess of α-thrombin is present, yielding an α- thrombin/anophelin molar ratio of 1.84, the enzyme's residual activity is ^" 45% , and anophelin cannot be detected in the gel as a single fast-migrating band; in addition, part of α-fhrombin behaves like the noncomplexed molecule. This results indicates that enzyme-inhibitor formation occurs at a 1 1 molar concentration The anophelm-α-thrombin mteraction is not covalent, since it can be disrupted by SDS (see FIG 18B)

To demonstrate that the observed interaction of anophelin is specific for α-thrombin, in some experiments, anophehn (10 μM) was incubated with profhrombin (6 9 μM), factor X (6 9 μM), or factor Xa (6 9 μM) followed by resolution of complex formation by nondenaturmg gel electrophoresis as described above Incubation with anophelin did not modify the migration pattern of the factors tested Therefore, anophelm does not form significant complexes with these proteins In addition, mcubation of anophelm (6 75 μM) with α-thrombin (8 3 μM) for up to six hours at 37 °C, followed by separation of the complex with Laemmh buffer, boiling, and 4-20% SDS- PAGE, did not modify the amount of anophelin detected as a low molecular weight protem, indicatmg that cleavage of anophelm, at least in its functional inhibitory domain, did not occur

EXAMPLE 9 Calculation of K * and K, for α-Thrombin This example describes methods used to calculate the apparent inhibition constant (K *) and the real inhibition constant (K,) of the particular anophehn synthesized in EXAMPLE 6 (referred to in this example as anophelm) on α-thrombin

Chromogenic substrate hydrolysis was detected as described in EXAMPLE 7 Briefly, anophelm (300 pM) was incubated for 15 minutes at 37°C with chromogenic substrate S-2238 (500 μM) followed by addition of α-fhrombin (50 pM) (FIG 12, curve b) Alternatively, reactions were started by addition of chromogemc substrate S-2238 (500 μM) after a 30 mmute premcubation of α-thrombm (50 pM) and anophelin (300 pM) at 37 °C (to form the complex first) (FIG 12, curve c) Substrate hydrolysis was followed for two hours at 37°C, at 405 nm In all kinetic measurements care was taken to ensure that substrate was less than 20% hydrolyzed The total volume of the reaction was 200 μL All reagents were diluted in the reaction buffer, HEPES-BSA (50 mM HEPES, 0 5% BSA, pH 7 4)

Premcubation of anophehn with α-thrombm prior to the addition of substrate showed a product progress curve with an upward concavity (FIG 12, curve c) However, when α-thrombin was added to the reaction medium containing anophelm, the progress curve displayed a downward concavity (FIG 12, curve b) This experiment demonstrates that the interaction of anophelin with α-thrombin displays slow-binding kmetics as seen with many peptidic inhibitors of serme protemases

In addition to exhibiting slow-binding kmetics, anophehn significantly inhibits α-fhrombin at concentrations similar to that of the enzyme (FIGS 11 and 12), mdicatmg that anophelm is also a tight-bindmg inhibitor Conventional Michaehs-Menten kinetics do not apply to the study of tight-binding inhibitors, because it assumes that the free inhibitor concentration is equal to the total inhibitor concentration, a condition met when the enzyme used is at a much lower concentration than the inhibitor. Therefore, Morrison's equation for tight-binding inhibition (Morrison, Biochem. Biophys. Ada 185:269-86, 1969; Williams and Morrison, Methods Enzymol. 63:437-63, 1979) was used to obtain apparent dissociation constants for anophelin:

V_s/V₀ = {([E_t-]-[IJ-K,*) + [([IJ +K,*-[EJ² + 4Ki*[EJ]^1/2}/2[EJ (1) where Ki* is the apparent dissociation constant for the enzyme-inhibitor complex, Vs is the inhibited steady-state velocity, V₀ is the control (uninhibited) velocity, [IJis the total inhibitor concentration, and [EJ is the total enzyme (α-thrombin) concentration. If inhibition is noncompetitive, then K, will be equal to K ,*; however, if inhibition is competitive, K * will be dependent on substrate concentration. Using this method, K * was calculated at various substrate concentrations (FIG. 13).

In these experiments, the enzyme α-thrombin (50 pM) was allowed to interact for one hour with anophelin (0-600 pM), in the presence of several concentrations of chromogenic substrate S-2238 (37.5-500 μM), before product rate formation for the following 30 minutes was recorded as described above. Resulting steady-state rates were fit by nonlinear regression to eq 1 for several substrate concentrations.

FIG. 13 shows V_s/V₀ plotted against anophelin concentration for a 500 μM substrate concentration, the line being the best sum of squares fit obtained with a K * of 63 pM. The reactions were initiated by the addition of α-thrombin (50 pM) to a mixture containing anophelin and S-2238 (500 μM) and was followed for two hours at 37°C. When the K * for several substrate concentrations was plotted against the substrate concentration, a linear regression line (r² = 0.9941) indicated a y-intercept of 5.87 ± 1.46 pM (FIG. 13, inset), which is an estimate of anophelin's K, for R-fhrombin. These results demonstrate a linear relationship between K * and substrate concentration, indicating that the inhibition is competitive and follows the expression:

K,*=K,(1 + [S]/K_m) (2) Slow-binding, competitive inhibition can be described by at least two mechanisms

(Morrison, Biochem. Biophys. Ada 185:269-86, 1969; Williams and Morrison, Methods Enzymol. 63:437-63, 1979).

Scheme 1 E + S ^> ES » P

K K.

El Scheme 2

k-2

Scheme 1 predicts the formation of a single El complex, while Scheme 2 postulates the rapid formation of an El complex which then slowly isomerizes to a more stable complex (El*). In Scheme 1 there is a linear relationship between inhibitor concentration and the apparent first-order rate constant, k„_bs (eq 3), while Scheme 2 predicts a hyperbolic relationship (eq 4), where K_{i app} ) = K,(l + [SJK and K, = k ,/k, :

*_Λ. - *-, ⁺ *i -r]/(l ⁺ [S-/* (3) „bs = * -2 ⁺ £2 [I]/(lI] ⁺ ,,app) (4)

To obtain kobs, progress curves of product formation by α-thrombin (not preincubated with inhibitor) were analyzed by using the rate equations of Morrison (Morrison, Biochem. Biophys. Ada 185:269-86, 1969; Williams and Morrison, Methods Enzymol. 63:437-63, 1979) and Cha (Cha, Biochem. Pharmacol. 24:2177-85, 1975):

P = VJ + rVo - Vjα - e**") **, (5)

The integrated first-order rate equation describes the slow establishment of equilibrium between enzyme and inhibitor where P is the measured absorbance defined as a function of initial (V₀) and final (V_s) steady-state velocities and the apparent first-order rate constant, &_obs, which describes the equilibration from the initial to the final steady state (Jordan et al., Biochemistry 29: 11095-100, 1990). Progress curves obtained in different inhibitor and substrate concentrations were fit by nonlinear regression to eq 5 to obtain A;_obs at different inhibitor and substrate concentrations. Plots of k_obs thus obtained against anophelin (0-600 pM) concentrations were fit by linear regression, with a correlation coefficient higher than 0.95 for each of the four substrate concentrations used (FIG. 14). The plots did not indicate a hyperbolic relationship as proposed by Scheme 2. Therefore, Scheme 1 is a good model for the interaction of anophelin with α-thrombin. According to eq 3, k can be estimated from the y axis intercepts of k_obs versus inhibitor plots (FIG. 14). The slope of such graphs represents the expression kf(\ + [S]/K . A plot of these slopes obtained at several substrate concentrations, plotted as a function of 1/(1 + [S]/K_m), should thus yield a straight line crossing the origin, with a slope numerically equal to k, (FIG. 14, inset). A &, of 2.11 + 0.06 x 10⁸ M^"1 s ¹ and a :._! of 4.05 ± 0.97 x 10^"4 s^"1 (mean + SE) were calculated. Since K, = k.fk an independent estimate of Ki is obtained (1.91 pM), which is in reasonable agreement (considering the standard errors involved) with the Ki of 5.87 pM obtained above, with a different set of experiments and equations. These experiments also confirm the competitive nature of the inhibition of α-thrombin by anophelin.

EXAMPLE 10 Determination of Salt Effect This example describes methods used to determine the effect of salt concentration on the affinity of the anophelin-α-fhrombin complex using the chromogenic assay described in EXAMPLES 7 and 9. The kinetic constants obtained in the above EXAMPLES were obtained under low ionic strength conditions. Because anophelin is a highly charged molecule, higher ionic strength may increase anophelin' s K, by decreasing ionic interactions between the enzyme and the inhibitor. Therefore, the effects of salt concentration on the affinity of anophelin-α-fhrombin was tested. α-fhrombin (50 pM) was added to a mixture containing the anophelin of SEQ ID NO 4)(0 nM-40 nM) and chromogenic substrate (S-2238, 250 μM) in the presence of 0.15 M or 0.4 M NaCl, and the mixture analyzed as described in EXAMPLE 7. At 0.15 M NaCl, anophelin behaved as a typical slow-binding inhibitor (FIG. 15A), and considerably higher concentrations of the anophelin (0.625-40 nM) were necessary for inhibition of α-thrombin (50 pM) (FIG. 15A). At such salt concentrations, anophelin concentration is far above enzyme concentration, as described for many classical enzyme inhibitors. Double-reciprocal plots were used to calculate the K ,*, and by using the expression K * = K,(l + [IJ7K , a K, of 103.8 + 14.3 pM was obtained (FIG. 15B). At 0.4 M NaCl, even higher concentrations of anophelin were necessary to inhibit α-thrombin, and a K, of 1.22 nM was calculated. The increase in the K, observed at higher salt concentrations suggests that ionic interactions mediate anophelin-α-thrombin complex formation.

Fibrinogen was used as an alternative to the chromogenic substrate, to better mimic in vivo conditions. The reactions were initiated by the addition of α-thrombin (0.6 nM) to a mixture containing various concentrations of anophelin (0-0.8 nM) and fibrinogen at (•) 0.625 mg/mL, (■) 1.25 mg/mL, (A) 2.5 mg/mL, (T) 5 mg/mL, and (♦) 10 mg/mL. When fibrinogen was used as substrate, slow-binding inhibition was observed (not shown) and a shift to the right was obtained for the inhibitory activity of anophelin, indicating that α-thrombin inhibition was competitive (FIG. 15C). Linear regression of the data yielded a K, of 263.8 pM (r=0.96). When α-thrombin was equilibrated with anophelin before the addition of fibrinogen, the K * did not change, indicating that anophelin-α-thrombin complex dissociates slowly. EXAMPLE 11 Identification of the Anophelin Binding site on α-Thrombin

This example describes assays that were used to determine which site anophelin was binding to on α-thrombin. α-Thrombin has two primary functional domains: the catalytic site, which cleaves fibrinogen, and TABEl, which mediates α-thrombin interaction with a number of molecules including fibrinogen, protein C, fhrombomodulin, and thrombin receptor. One additional site, TABE2, mediates α-fhrombin binding to heparin-anti-fhrombin III complex.

To identify the role of α-thrombin functional domains on the inhibitory properties of anophelin, experiments were performed using γ-thrombin. γ-thrombin is produced by limited proteolysis of α-fhrombin by trypsin, where TABEl is suppressed. Anophelin (0-72 nM), was incubated for 15 minutes with chromogenic substrate (125 μM) followed by the addition of γ- fhrombin (0.45 nM) using the assay described in EXAMPLE 7. In contrast to its effects on α- thrombin, anophelin behaves as a fast and classical inhibitor of γ-thrombin, and inhibition is observed at inhibitor concentrations far above the enzyme concentration (FIG. 16A). Incubation of γ-fhrombin (4 μM) with anophelin (10 μM), followed by nondenaturing electrophoresis of the mixture using the methods described in EXAMPLE 8, a mobility shift of γ- thrombin was observed (FIG. 16C, lanes 1 and 2) that reaches a maximum when the anophelin-γ- thrombin molar ratio is 1. These results provide direct evidence that anophelin binds to γ- thrombin, most likely by interaction with the catalytic site. Since TABE2 is also present in γ-fhrombin, experiments were conducted to determine if the catalytic site was the only domain involved in the anophelin-γ-fhrombin interaction, γ-thrombin (4 μM) was incubated with 5 μM D-Phe-Pro-Arg chloromethyl ketone (PPACK, CalBiochem, San Diego, CA), a reagent that irreversibly modifies the catalytic site of thrombin by alkylating active- site histidine (Bode et al. , EMBO J. 11 :3467-75, 1989) in 0.75 M NaCl, 100 mM Tris, pH 8.0 at 37 °C for 30 minutes. This was followed by several washings (with HEPES 50 mM, pH 7.4), and concentration of the samples in 3-kDa cutoff Microcon (Millipore Co. , Bedford) at 4°C. As shown in FIG. 16C, PPACK-γ-thrombin (lane 3) has a slower migration pattern than nontreated γ- thrombin (lane 1). Incubation of PPACK-γ-fhrombin with an excess of anophelin (10 μM) did not change the migration pattern (lane 4), in contrast to nontreated γ-fhrombin (lane 2). Similar results were obtained with PPACK-α-thrombin (0.83 μM), whose migration is not modified by anophelin. These results indicate that at least part of the high-affinity interaction involving γ-thrombin and anophelin is mediated by the catalytic site. EXAMPLE 12 Calculation of K₍* and K| for γ-Thrombin

This example describes experiments to calculate the K * and K, of the anophelin (the embodiment synthesized in Example 6) for γ-fhrombin. Apparent Ki* from steady-state velocities was determined by the addition of γ-thrombin (0.45 nM) to a mixture containing various concentrations of anophelin (•, 1.125 nM; ■, 2.25 nM; ▲, 4.5 nM; T, 9 nM; ♦, 18 nM) and chromogenic substrate (62.5 - 500 μM). A double-reciprocal plot of the data yielded a K, of 0.694 ± 0.063 nM (FIG. 16B). The larger K, for anophelin when using γ-fhrombin, together with the effects of NaCl in the dissociation constant of anophelin vs α-thrombin interaction, strongly suggests that TABEl is involved in the interaction of anophelin with α-thrombin.

In contrast to α-thrombin, addition of chromogenic substrate (125 μM) to a mixture containing anophelin (0-24 nM) and γ-fhrombin (160 pM) changed the K * of enzyme-inhibitor complex (FIG. 17), indicating that the interaction of γ-fhrombin with anophelin dissociates faster than the α-fhrombin-anophelin complex. A K, of 0.36 + 0.03 nM was obtained under these conditions.

EXAMPLE 13 Determination of TABEl Contribution to the α-Thrombin-anophelin Complex This example describes assays used to determine if the TABEl site of α-thrombin is involved in the formation of the α-thrombin-anophelin complex.

Anophelin is an acidic protein (pi 3.52), containing (in some embodiments) 17 (out 60) strongly acidic amino acids in its sequence: 10 aspartic acids, and 7 glutamic acids. Therefore, the TABEl site may be involved in the interaction between anophelin and α-fhrombin. The possible contribution of TABEl on the interaction of α-thrombin with anophelin was determined using two assays.

First, α-thrombin (0.75 nM) was incubated at 37°C for 10 minutes with (•) buffer, (■) 0.5, (A) 1, (T) 2, or (♦) 4 μM C-terminal hirudin fragment 54-65 ([tyr(S0₃H)⁶³]-hirudin fragment 54-65, Sigma Chemical Co. St. Louis, MO), followed by addition of anophelin and 200 μM chromogenic substrate. Samples were read as described in EXAMPLE 7. Increasing the C- terminal hirudin fragment concentration decreased the inhibitory property of anophelin on α- hrombin-mediated chromogenic substrate hydrolysis, with a right-shifted inhibitory dose-response curve (FIG. 19A). This indicates that anophelin binds to TABEl, because the C-terminal sequence of hirudin binds to TABEl without affecting the catalytic activity of α-thrombin (Rydel et al. , Science 249:277 '-80, 1990; Fareed et al , Sem. Hematol. 36:42-56, 1999; Maraganore et ai , Biochem. 29:7095-101, 1990). Trypsin cleaves the Arg73-Asn74 bond of α-thrombin, disrupting the enzyme TABEl (Bτaun et al, Thromb. Res. 50:273-83, 1988). The effect of anophelin on trypsin-mediated proteolysis of α-thrombin was determined by incubating α-fhrombin (4.1 μM, 47 pmoles) with buffer or anophelin (10 μM) in the absence or presence of trypsin (250 ng) in 50 mM HEPES, pH 7.4, forming a total volume of 10 μl, for 10 minutes. Mixtures were incubated for one hour at

37°C, and reactions were terminated by addition of Laemmli buffer containing 2% SDS and 5 % β- mercaptoefhanol (final concentrations) and boiling for five minutes. Complex formation was analyzed using 4-20% SDS-PAGE as described above.

As shown in FIG. 18B, incubation of α-thrombin with buffer (lane 1) or the anophelin of Example 6 (lane 2), followed by denaturing SDS-PAGE, does not result in the formation of an enzyme-inhibitor complex. This result demonstrates that anophelin-α-thrombin complex is not covalent. In addition, as expected for a high-affinity TABEl inhibitor, trypsin-mediated hydrolysis of α-thrombin (lane 3) was completely blocked by anophelin (lane 4). Control experiments indicated that anophelin (up to 15 μM, highest concentration tested) does not function as a trypsin inhibitor. However, anophelin did not modify the migration of PPACK-α-fhrombin (data not shown), suggesting that the interaction of anophelin with TABEl alone may be of lower affinity, in comparison to native α-thrombin.

Anophelin interaction with TABE 1 is substantiated by the finding that its affinity for α- thrombin is dramatically reduced in the presence of salts and it behaves as a lower-affinity, fast- inhibitor of γ-thrombin, in comparison to intact α-thrombin molecule. Anophelin therefore appears to bind to the catalytic site of α-thrombin and this interaction is strengthened when TABEl is preserved. In this respect, anophelin resembles hirudin that behaves as a bivalent α-fhrombin inhibitor. However, the sequence homology clearly distinguishes both molecules, and hirudin behaves as a slow binding inhibitor only at 0.2 M or higher salt concentrations (Stone and Hofsteenge, Biochem. 25:4622-8, 1986). Table 2 summarizes the findings concerning the kinetic pattern of the interaction between anophelin and α-thrombin or γ-thrombin.

Table 2. Kinetic pattern of anophelin-thrombin interactions

Ki (pM) Type of inhibition Fold decrease in K, ^a α-Thrombin plus: O NaCl 5.87 + 1.46 slow and tight 0.15 M NaCl 103.8± 14.3 slow and classical 17.6 0.4 M NaCl 1220± 150 slow and classical 207.8 γ-thrombin (0 NaCl) 694±63.52 fast and classical 118.2

"Comparison with the Ki obtained for α-i thrombin-anophelin interaction, in the absence of NaCl. EXAMPLE 14 Effect of Anophelin on Clot-Bound α-Thrombin

This example describes assays used to determine whether anophelin can inhibit the α- thrombin within a blood clot (a thrombus). Production of α-fhrombin in vivo is accompanied by formation of a clot, and a fraction of α-thrombin remains associated with insoluble fibrin.

Although the clot behaves mainly as a trap for α-fhrombin, it can also act as a reservoir for active α-thrombin. Clot-bound α-thrombin can cleave fibrinogen and activate factors V and VIII and platelets. This can lead to persistent activation of the coagulation cascade at sites of thrombus formation (Francis et al. , J. Lab. Clin. Med. 102:220-30, 1983; Bar Shavit et al. , J. Clin .Invest. 84: 1096-104, 1989; Weitz and Hirsh, . /. Lab. Clin. Med. 122:364-373, 1993). α-fhrombin in this environment is protected from inhibition by heparin-antithrombin III complex, the current mainstay of antithrom-botic therapy (Stone and Tapparelli, J. Enzyme Inhibition 9:3-15, 1995). Heparin acts primarily by accelerating the rate at which antifhrombin inactivates α-thrombin and factor Xa. Although heparin is effective in the prevention and treatment of thromboembolic disorders, one of the most serious limitations of heparin is its inability to catalyze the inactivation of clot-bound α- fhrombin. Since anophelin is a small molecule with high affinity for α-thrombin, experiments were conducted to determine its effect on clot-bound α-thrombin.

Clot-bound α-thrombin was tested for its activity on chromogenic substrate hydrolysis. Fibrin clots were prepared by incubating 300 μl of purified fibrinogen (2 mg/ml in 50 mM HEPES, pH 7.5, 150 mM NaCl, and 10 mg/ml CaCl₂) with 30 nM α-thrombin. After two hours at 37°C, the clots were extensively washed in the same buffer, which was changed eight times over 24 hours. The clots were carefully transferred to a new eppendorf tube and incubated with 200 μl of increasing concentrations of anophelin (diluted in 50 mM HEPES, pH 7.5, 150 mM NaCl, 0.5% BSA) for 30 minutes at 37 °C. Chromogenic substrate (final concentration 200 μM) was then added and the reaction mixture incubated for 90 minutes at 37 °C. Aliquots were taken and substrate hydrolysis estimated by end point reading at 405 nm, using a Thermomax microplate reader. Experiments were performed in quadruplicate.

Clot-bound α-thrombin-induced chromogenic substrate was inhibited by anophelin in a concentration-dependent manner, with a IC₅₀ of 45 nM (FIG. 19). This indicates that anophelin, in contrast to heparin and like PPACK, hirulog, and hirudin, can inactivate the α-fhrombin bound to fibrin (Weitz and Hirsh, /. Lab. Clin. Med. 122:364-73, 1993; Weitz et al., /. Clin. Invest. 86:385-91, 1990). EXAMPLE 15 Determination of in vitro α-Thrombin Generation

This example describes assays used to determine the effect of anophelin on the production of α-thrombin. Generation of α-thrombin is triggered by a cascade of enzyme activation leading to an explosive production of the enzyme. In addition, α-thrombin amplifies its own generation by a feed-back mechanism: traces of α-thrombin formed during the initial lag phase activate factor V and factor VIII, leading to a steep increase in thrombin formation (Gallistl et al. , Thromb. Haemost. 74: 1163-8, 1995; Ofosu et al, Sem. Thromb. Hemost. 22:303-8, 1996; Prasa er α/. , Thromb. Haemost. 77:498-503, 1997). To observe the effects of anophelin in the explosive production of α-thrombin, its production was activated by addition of APTT reagent and CaCl₂ to plasma in the presence of increasing concentrations of anophelin. Free α-fhrombin generation was assessed by measuring chromogenic substrate hydrolysis, using GPRP to prevent fibrinogen polymerization.

Human platelet-poor plasma (500 μl) was activated by addition of 16 μl APTT reagent (cephalin plus ellagic acid, Sigma, St. Louis, MO) and 20 μl 0.5 M CaCl₂ in the presence of (•) buffer, or (■) 0.5 μM, or (A) 1 μM anophelin. At 15-second time intervals, 10 μL of activated plasma was removed and transferred into 200 μl of substrate solution (200 μM S2238 in HEPES- BSA, pH 7.4). After 10 minutes, 50 μl of glacial acetic acid was added, and absorbance was measured at 405 nm against a blank. This assay measures free, uninhibited α-thrombin rather than total α-thrombin production. The amidolytic activity of α-fhrombin is expressed as the equivalent amount of α-thrombin considering an activity of 3 mOD/min nM of α-thrombin.

As shown in FIG. 20, 0.5 μM of this synthetic anophelin increases the lag phase of explosive α-thrombin production. At 1 μM, increase in the lag phase is accompanied by a decrease in the total production of thrombin. Similar results were obtained with hirudin. These findings demonstrate that α-thrombin inhibition by anophelin (and hirudin) is related to direct inactivation of already-generated α-thrombin, rather than formation of it.

EXAMPLE 16 Cloning Anophelin in Other Species Having presented the nucleotide sequence of A. albimanus anophelin cDNA and the amino acid sequence of the encoded protein, this disclosure now also facilitates the identification of DNA molecules, and thereby proteins, which are the anophelin homologs in other species, for example in other species of mosquitoes. These other homologs can be derived from those sequences disclosed, but which vary in their precise nucleotide or amino acid sequence from those disclosed. Such variants may be obtained through a combination of standard molecular biology laboratory techniques and the nucleotide and amino acid sequence information disclosed herein. The anophelin homologs in other organisms may be identified by using the anophelin sequences to design probes, for example an oligonucleotide or polynucleotide. Such probes can be used to screen a genomic or cDNA library from any organism using standard hybridization methods. In addition, primers or degenerate primers covering regions of anophelin thought to be important for its function (for example the last 59 amino acids), can be designed for use in a PCR reaction to amplify anophelin homologs from a genomic or cDNA library.

EXAMPLE 17 Production of Sequence Variants of Anophelin cDNA and Protein SEQ ID NO 1 shows the nucleotide sequence of the A. albimanus mosquito anophelin cDNA, and the amino acid sequence of the mosquito anophelin protein encoded by this cDNA is shown in SEQ ID NO 3. The distinctive functional characteristic of anophelin is its ability to inhibit α-fhrombin, prevent platelet aggregation, and thus inhibit blood clotting. This activity of the anophelin protein may readily be determined using the assays described above, for examples those described in EXAMPLES 2 and 7.

Having presented the nucleotide sequence of the A. albimanus anophelin cDNA and the amino acid sequence of the encoded protein, this disclosure facilitates the creation of DNA molecules, and thereby proteins, derived from those disclosed but which vary in their precise nucleotide or amino acid sequence from those disclosed. Such variants may be obtained through a combination of standard molecular biology laboratory techniques and the nucleotide sequence information disclosed herein.

Anophelin variants and fragments will retain the ability to inhibit α-thrombin (for example with a Ki of 3-100 pM), prevent platelet aggregation and blood clotting. The prior art indicates that negatively charged amino acids are important for the inhibition of α-fhrombin by hirudin. Since the amino terminal portion of anophelin has a higher negative charge density, in particular embodiments these residues of anophelin ideally do not substantially diverge from the wild-type sequence shown in SEQ ID NOs 3-5. Other important residues include the N-terminal site (APQYA, SEQ ID NO 11), as well as the conserved negatively charged amino acids (D₈, D_B, E₁₄, D₁₈, D₃₁, E₄₃) and a conserved arginine (R₅₃) at the carboxy terminal region. However, conservative substitutions will be better tolerated than non-conservative substitutions. The indication of highly conserved regions in FIG. 5B provides further guidance in helping select residues that may be substituted or deleted. Variants and fragments may retain at least 60% , 70% , 80% , 85% , 95% , 98% , or greater sequence identity to the anophelin amino acid sequences disclosed herein, and in particular embodiments at least this much identity to SEQ ID NO 4. Less identity is allowed, as long as the variant anophelin sequence maintains the functional activity of the anophelin protein as defined herein. Such activity can be readily determined using the assays disclosed herein. The simplest modifications involve the substitution of one or more amino acid residues (for example 2, 5 or 10 residues) for amino acid residues having similar biochemical properties. These so-called conservative substitutions are likely to have minimal impact on the activity of the resultant protein. Substitutional variants are those in which at least one residue in the amino acid sequence has been removed and a different residue inserted in its place. Such substitutions generally are conservative when it is desired to finely modulate the characteristics of the protein. Examples of amino acids which may be substituted for an original amino acid in a protein and which are regarded as conservative substitutions include: Ser for Ala; Lys for Arg; Gin or His for Asn; Glu for Asp; Ser for Cys; Asn for Gin; Asp for Glu; Pro for Gly; Asn or Gin for His; Leu or Val for lie; He or Val for Leu; Arg or Gin for Lys; Leu or He for Met; Met, Leu or Tyr for Phe; Thr for Ser; Ser for Thr; Tyr for Trp; Tip or Phe for Tyr; and He or Leu for Val.

Amino acid substitutions are typically of single residues, for example 1, 2, 3, 4, 5, 10 or more substitutions; insertions usually will be on the order of about from 1 to 10 amino acid residues; and deletions will range about from 1 to 30 residues. Substitutions, deletions, insertions or any combination thereof may be combined to arrive at a final construct. Obviously, the mutations that are made in the DNA encoding the protein must not place the sequence out of reading frame and preferably will not create complementary regions that could produce secondary mRNA structure.

Substantial changes in function or immunological identity are made by selecting substitutions that are less conservative than those listed above, i.e., selecting residues that differ more significantly in their effect on maintaining (a) the structure of the polypeptide backbone in the area of the substitution, for example, as a sheet or helical conformation, (b) the charge or hydrophobicity of the molecule at the target site, or (c) the bulk of the side chain. The substitutions which in general are expected to produce the greatest changes in protein properties will be those in which (a) a hydrophilic residue, e.g. , seryl or threonyl, is substituted for (or by) a hydrophobic residue, e.g. , leucyl, isoleucyl, phenylalanyl, valyl or alanyl; (b) a cysteine or proline is substituted for (or by) any other residue; (c) a residue having an electropositive side chain, e.g., lysyl, arginyl, or histadyl, is substituted for (or by) an electronegative residue, e.g., glutamyl or aspartyl; or (d) a residue having a bulky side chain, e.g., phenylalanine, is substituted for (or by) one not having a side chain, e.g. , glycine. Such variants can be readily selected for additional testing by performing an assay (such as that shown in EXAMPLE 11) to determine if the variant is a tightly binding inhibitor with a K, of less than a desired amount, for example less than about 10 nM, for example less than about 100 pM. Anti-thrombin activity can also be readily assayed, for example by testing the effect of the variant on clot-bound α-thrombin as in EXAMPLE 14, inhibition of α-thrombin generation as in EXAMPLE 15, inhibition of platelet aggregation as in EXAMPLE 7.

The effects of these amino acid substitutions or deletions or additions may be assessed for derivatives of the anophelin protein by the assays as described in the EXAMPLES above. Variant DNA molecules include those created by standard DNA mutagenesis techniques, for example, M13 primer mutagenesis. Details of these techniques are provided in Sambrook et al. (Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, New York, 1989, Chapter 15). By the use of such techniques, variants may be created which differ in minor ways from the disclosed sequences. DNA molecules and nucleotide sequences which are derivatives of those specifically disclosed herein, and which differ from those disclosed by the deletion, addition or substitution of nucleotides while still encoding a protein which possesses the functional characteristic of the anophelin protein, are comprehended by this disclosure.

Also within the scope of this disclosure are small DNA molecules which are derived from the disclosed DNA molecules. Such small DNA molecules include oligonucleotides suitable for use as hybridization probes or polymerase chain reaction (PCR) primers. As such, these small DNA molecules comprise at least a segment of an anophelin cDNA molecule or gene and, for the purposes of PCR, will comprise at least 30, 40, or 50 contiguous nucleotides of the anophelin cDNA or gene from SEQ ID NO 1 or its complementary strand, or at least 21, 25, 30, or 50 contiguous nucleotides of the anophelin cDNA or gene from SEQ ID NO 2 or its complementary strand. It will be appreciated that such longer length nucleotide sequences will provide greater specificity in hybridization or PCR applications than shorter length sequences. Accordingly, superior results may be obtained using these longer stretches of consecutive nucleotides.

DNA molecules and nucleotide sequences which are derived from the disclosed DNA molecules as described above may also be defined as DNA sequences which hybridize under stringent conditions to the DNA sequences disclosed, or fragments thereof. Hybridization conditions resulting in particular degrees of stringency will vary depending upon the nature of the hybridization method of choice and the composition and length of the hybridizing DNA used. Generally, the temperature of hybridization and the ionic strength (especially the Na⁺ concentration) of the hybridization buffer will determine the stringency of hybridization. Calculations regarding hybridization conditions required for attaining particular degrees of stringency are discussed by Sambrook et al. (Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, New York, 1989, Chapters 9 and 11), herein incorporated by reference.

Specific hybridization refers to the binding, duplexing, or hybridizing of a molecule only or substantially only to a particular nucleotide sequence when that sequence is present in a complex mixture (e.g. total cellular DNA or RNA). Specific hybridization may also occur under conditions of varying stringency.

Hybridization conditions resulting in particular degrees of stringency will vary depending upon the nature of the hybridization method of choice and the composition and length of the hybridizing DNA used. Generally, the temperature of hybridization and the ionic strength

(especially the Na⁺ concentration) of the hybridization buffer will determine the stringency of hybridization. Calculations regarding hybridization conditions required for attaining particular degrees of stringency are discussed by Sambrook et al. (Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, New York, 1989 ch. 9 and 11). By way of illustration only, a hybridization experiment may be performed by hybridization of a DNA molecule to a target DNA molecule which has been electrophoresed in an agarose gel and transferred to a nitrocellulose membrane by Southern blotting (Southern, . Mol. Biol. 98:503, 1975), a technique well known in the art and described in Sambrook et al. (Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, New York, 1989).

By way of illustration only, a hybridization experiment may be performed by hybridization of a DNA molecule (for example, a variant of the anophelin cDNA) to a target DNA molecule (for example, the anophelin cDNA) which has been electrophoresed in an agarose gel and transferred to a nitrocellulose membrane by Southern blotting (Southern, J. Mol. Biol. 98:503, 1975), a technique well known in the art and described in Sambrook et al. (Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, New York, 1989). Hybridization with a target probe labeled, for example, with [³²P]-dCTP is generally carried out in a solution of high ionic strength such as 6xSSC at a temperature that is 20-25 °C below the melting temperature, T_m, described below. For such

Southern hybridization experiments where the target DNA molecule on the Southern blot contains 10 ng of DNA or more, hybridization is typically carried out for 6-8 hours using 1-2 ng/ml radiolabeled probe (of specific activity equal to 10⁹ CPM/μg or greater). Following hybridization, the nitrocellulose filter is washed to remove background hybridization. The washing conditions should be as stringent as possible to remove background hybridization but to retain a specific hybridization signal.

The term T_m represents the temperature (under defined ionic strength, pH and nucleic acid concentration) at which 50% of the probes complementary to the target sequence hybridize to the target sequence at equilibrium. Because the target sequences are generally present in excess, at T_m 50% of the probes are occupied at equilibrium. The T_m of such a hybrid molecule may be estimated from the following equation (Bolton and McCarthy, Proc. Natl. Acad. Sci. USA 48: 1390, 1962): T_m = 81.5°C - 16.6(log₁₀[Na⁺]) + 0.41(%G+C) - 0.63(% formamide) - (600/1); where 1 = the length of the hybrid in base pairs.

This equation is valid for concentrations of Na⁺ in the range of 0.01 M to 0.4 M, and it is less accurate for calculations of T_m in solutions of higher [Na⁺] . The equation is also primarily valid for DNAs whose G+C content is in the range of 30% to 75 % , and it applies to hybrids greater than 100 nucleotides in length (the behavior of oligonucleotide probes is described in detail in Ch. 11 of Sambrook et al. , Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, New York, 1989). Thus, by way of example, for a 150 base pair DNA probe with a hypothetical GC content of 45 % , a calculation of hybridization conditions required to give particular stringencies may be made as follows: For this example, it is assumed that the filter will be washed in 0.3 xSSC solution following hybridization, thereby [Na⁺] = 0.045M; %GC = 45% ; Formamide concentration = 0; 1 = 150 base pairs; T_m = 81.5 - 16(log₁₀[Na⁺]) + (0.41 x 45) -(600/150) and so T_m = 74.4°C.

The T_m of double-stranded DNA decreases by 1-1.5°C with every 1 % decrease in homology (Bonner et al. , 1973, /. Mol. Biol. 81 :123). Therefore, for this given example, washing the filter in 0.3 xSSC at 59.4-64.4°C will produce a stringency of hybridization equivalent to 90% ; that is, DNA molecules with more than 10% sequence variation relative to the target cDNA will not hybridize. Alternatively, washing the hybridized filter in 0.3 xSSC at a temperature of 65.4- 68.4°C will yield a hybridization stringency of 94% ; that is, DNA molecules with more than 6% sequence variation relative to the target cDNA molecule will not hybridize. The above example is given entirely by way of theoretical illustration. One skilled in the art will appreciate that other hybridization techniques may be utilized and that variations in experimental conditions will necessitate alternative calculations for stringency.

Examples of stringent conditions are those under which DNA molecules with more than 25 % , 15 % , 10% , 6% or 2% sequence variation (also termed "mismatch") will not hybridize.

Stringent conditions are sequence dependent and are different in different circumstances. Longer sequences hybridize specifically at higher temperatures. Generally, stringent conditions are selected to be no more than about 5°C lower than the thermal melting point T_m for the specific sequence at a defined ionic strength and pH. An example of stringent conditions is a salt concentration of at least about 0.01 to 1.0 M Na ion concentration (or other salts) at pH 7.0 to 8.3 and a temperature of at least about 30°C for short probes (e.g. 10 to 50 nucleotides). Stringent conditions can also be achieved with the addition of destabilizing agents such as formamide. For example, conditions of 5X SSPE (750 mM NaCl, 50 mM Na Phosphate, 5 mM EDTA, pH 7.4) and a temperature of 25-30°C are suitable for allele-specific probe hybridizations. A perfectly matched probe has a sequence perfectly complementary to a particular target sequence. The test probe is typically perfectly complementary to a portion (subsequence) of the target sequence. The term "mismatch probe" refers to probes whose sequence is deliberately selected not to be perfectly complementary to a particular target sequence.

Transcription levels can be quantitated absolutely or relatively. Absolute quantitation can be accomplished by inclusion of known concentrations of one or more target nucleic acids (for example control nucleic acids such as Bio B or with a known amount the target nucleic acids themselves) and referencing the hybridization intensity of unknowns with the known target nucleic acids (for example by generation of a standard curve).

The degeneracy of the genetic code further widens the scope of the present disclosure as it enables major variations in the nucleotide sequence of a DNA molecule while maintaining the amino acid sequence of the encoded protein. For example, the second amino acid residue of the anophelin protein is alanine. This is encoded in the Anophelin cDNA by the nucleotide codon triplet GCT. Because of the degeneracy of the genetic code, three other nucleotide codon triplets, GCG, GCC and GCA, also code for alanine. Thus, the nucleotide sequence of the Anophelin cDNA could be changed at this position to any of these three codons without affecting the amino acid composition of the encoded protein or the characteristics of the protein. Based upon the degeneracy of the genetic code, variant DNA molecules may be derived from the cDNA molecules disclosed herein using standard DNA mutagenesis techniques as described above, or by synthesis of DNA sequences. DNA sequences which do not hybridize under stringent conditions to the cDNA sequences disclosed by virtue of sequence variation based on the degeneracy of the genetic code are herein also comprehended by this disclosure. One skilled in the art will recognize that the DNA mutagenesis techniques described above may be used not only to produce variant DNA molecules, but will also facilitate the production of proteins which differ in certain structural aspects from the anophelin protein, yet which proteins are clearly derivative of this protein and which maintain the essential functional characteristic of the anophelin protein as defined above. Newly derived proteins may also be selected in order to obtain variations on the characteristic of the anophelin protein, as will be more fully described below. Such derivatives include those with variations in the amino acid sequence including minor deletions, additions and substitutions.

While the site for introducing an amino acid sequence variation is predetermined, the mutation per se need not be predetermined. For example, in order to optimize the performance of a mutation at a given site, random mutagenesis may be conducted at the target codon or region and the expressed protein variants screened for optimal activity. Techniques for making substitution mutations at predetermined sites in DNA having a known sequence as described above are well known.

The A. albimanus Anophelin gene, Anophelin cDNA, DNA molecules derived therefrom and the protein encoded by these cDNAs and derivative DNA molecules may be utilized in aspects of both the study of anophelin and for diagnostic and therapeutic applications related to anophelin. Utilities disclosed herein include, but are not limited to, the anti-thrombotic activity disclosed herein. Those skilled in the art will recognize that the utilities herein described are not limited to the specific experimental modes and materials presented and will appreciate the wider potential utility of this disclosure.

EXAMPLE 18 Recombinant Expression of Anophelin

With the provision of the Anophelin cDNA, the expression and purification of Anophelin protein, or variants or fragments thereof, by standard laboratory techniques is now enabled. The purified protein may be used for functional analyses, antibody production and therapy in a subject. Furthermore, the DNA sequence of the Anophelin cDNA generated as disclosed in EXAMPLE 5 can be manipulated in studies to understand the expression of the gene and the function of its product Partial or full-length cDNA sequences encoding the Anophehn protein, may be ligated into bacterial expression vectors Methods for expressing large amounts of protein from a cloned gene introduced into E coh may be utilized for the purification, localization and functional analysis of proteins For example, fusion proteins consisting of amino termmal peptides encoded by a portion of the E coh lacZ or trpE gene linked to anophelm may be used to prepare polyclonal and monoclonal antibodies against anophelin Thereafter, these antibodies may be used to purify proteins by immunoaffinity chromatography, in diagnostic assays to quantitate the levels of protein and to localize anophelin in tissues and individual cells by lmmunofluorescence Intact native protein, or variants or fragments thereof, may also be produced in E coh in large amounts for functional studies Methods and plasmid vectors for producmg fusion protems and intact native proteins in bacteria are described in Sambrook et al (Molecular Cloning A Laboratory Manual, Cold Spring Harbor, New York, 1989, chapter 17, herein incorporated by reference) Such fusion proteins can be made in large amounts, are easy to purify, and can be used to elicit antibody response Native protems can be produced in bacteria by placmg a strong, regulated promoter and an efficient nbosome bmdmg site upstream of the cloned gene If low levels of protem are produced, additional steps may be taken to increase protein production, if high levels of protein are produced, purification is relatively easy Suitable methods are presented in Sambrook et al (Molecular Cloning A Laboratory Manual, Cold Spring Harbor, New York, 1989) and are well known in the art Often, protems expressed at high levels are found m insoluble inclusion bodies Methods for extracting protems from these aggregates are described by Sambrook et al (Molecular Cloning A Laboratory Manual, Cold Sprmg Harbor, New York, 1989, Chapter 17)

Vector systems suitable for the expression of lacZ fusion genes mclude the pUR series of vectors (Ruther and Muller-Hill, EMBO J 2 1791 , 1983), pEXl-3 (Stanley and Luzio, EMBO J 3 1429, 1984) and pMRlOO (Gray et al , Proc Natl Acad Sci USA 79 6598, 1982) Vectors suitable for the production of intact native protems mclude pKC30 (Simatake and Rosenberg, Nature 292 128, 1981), pKK177-3 (Amann and Brosius, Gene 40 183, 1985) and pET-3 (Studiar and Moffatt, J Mol Biol 189 113, 1986) Anophehn fusion protems may be isolated from protein gels, lyophihzed, ground mto a powder and used as an antigen The DNA sequence can also be transferred to other cloning vehicles, such as other plasmids, bacteriophages, cosmids, animal viruses and yeast artificial chromosomes (YACs) (Burke et al , Science 236 806-12, 1987) These vectors may then be introduced into a variety of hosts including somatic cells, and simple or complex organisms, such as bacteria, fungi (Timberlake and Marshall, Science 244 1313-7, 1989), invertebrates, plants (Gasser and Fraley, Science 244 1293, 1989), and mammals (Pursel et al , Science 244 1281-8, 1989), which cell or organisms are rendered transgenic by the mtroduction of the heterologous Anophelin cDNA In another approach, the recombinant anophelin protein may be generated using a baculovirus system, which has been used to produce other mosquito proteins (Stark and James, J. Biol. Chem. , 273:20802-9, 1998; Xu, Int. Arch. Allergy Immunol. , 115:245-51 , 1998, both herein incorporated by reference) and is therefore well-known by those skilled in the art. Briefly, the desired anophelin cDNA sequence (for example SEQ ID NOs 1 or 2, or variants or fragments thereof) is cloned into a vector, for example pGem-T (Promega) or pBlueScript, then subsequently subcloned into a baculovirus transfer vector such as pVL1393 or pAC360 (Invitrogen). This recombinant virus can then be used to infect insect (for examples see McCarroll and King, Curr. Opin. Biotech. 8:590-4, 1997) or other cells, for example Sc9 cells. The recombinant virus is then plaque -purified, and high-titer virus used for recombinant protein production expanding in other cells, such as Hi-5 cells (Invitrogen).

For expression in mammalian cells, the cDNA sequence may be ligated to heterologous promoters, such as the simian virus SV40, promoter in the pSV2 vector (Mulligan and Berg, Proc. Natl. Acad. Sci. USA 78:2072-6, 1981), and introduced into cells, such as monkey COS-1 cells (Gluzman, Cell 23: 175-82, 1981), to achieve transient or long-term expression. The stable integration of the chimeric gene construct may be maintained in mammalian cells by biochemical selection, such as neomycin (Southern and Berg, J. Mol. Appl. Genet. 1 :327-41 , 1982) and mycophoenolic acid (Mulligan and Berg, Proc. Natl. Acad. Sci. USA 78:2072-6, 1981).

DNA sequences can be manipulated with standard procedures such as restriction enzyme digestion, fill-in with DNA polymerase, deletion by exonuclease, extension by terminal deoxynucleotide transferase, ligation of synthetic or cloned DNA sequences, site-directed sequence- alteration via single-stranded bacteriophage intermediate or with the use of specific oligonucleotides in combination with PCR.

The cDNA sequence (or portions derived from it) or a mini gene (a cDNA with an intron and its own promoter) may be introduced into eukaryotic expression vectors by conventional techniques. These vectors are designed to permit the transcription of the cDNA eukaryotic cells by providing regulatory sequences that initiate and enhance the transcription of the cDNA and ensure its proper splicing and polyadenylation. Vectors containing the promoter and enhancer regions of the SV40 or long terminal repeat (LTR) of the Rous Sarcoma virus and polyadenylation and splicing signal from SV40 are readily available (Mulligan and Berg, Proc. Natl. Acad. Sci. USA 78:2072-6, 1981 ; Gorman et al. , Proc. Natl. Acad. Sci USA 78:6777-81, 1982). The level of expression of the cDNA can be manipulated with this type of vector, either by using promoters that have different activities (for example, the baculovirus pAC373 can express cDNAs at high levels in S. frugiperda cells (Summers and Smith, Genetically Altered Viruses and the Environment, Fields et al. (Eds.) 22:319-328, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York, 1985) or by using vectors that contain promoters amenable to modulation, for example, the glucocorticoid- responsive promoter from the mouse mammary tumor virus (Lee et al., Nature 294:228, 1982). The expression of the cDNA can be monitored in the recipient cells 24 to 72 hours after introduction (transient expression).

In addition, some vectors contain selectable markers such as the gpt (Mulligan and Berg, Proc. Natl. Acad. Sci. USA 78:2072-6, 1981) or neo (Southern and Berg, J. Mol. Appl. Genet. 1:327-41, 1982) bacterial genes. These selectable markers permit selection of transfected cells that exhibit stable, long-term expression of the vectors (and therefore the cDNA). The vectors can be maintained in the cells as episomal, freely replicating entities by using regulatory elements of viruses such as papilloma (Sarver et al. , Mol. Cell Biol. 1 :486, 1981) or Epstein-Barr (Sugden et al. , Mol. Cell Biol. 5:410, 1985). Alternatively, one can also produce cell lines that have integrated the vector into genomic DNA. Both of these types of cell lines produce the gene product on a continuous basis. One can also produce cell lines that have amplified the number of copies of the vector (and therefore of the cDNA as well) to create cell lines that can produce high levels of the gene product (Alt et al , J. Biol. Chem. 253: 1357, 1978).

The transfer of DNA into eukaryotic, in particular human or other mammalian cells, is now a conventional technique. The vectors are introduced into the recipient cells as pure DNA

(transfection) by, for example, precipitation with calcium phosphate (Graham and vander Eb, Virology 52:466, 1973) or strontium phosphate (Brash et al., Mol. Cell Biol. 7:2013, 1987), electroporation (Neumann et al, EMBO J 1 :841, 1982), lipofection (Feigner et al., Proc. Natl. Acad. Sci. U S A. 84:7413-7, 1987), DEAE dextran (McCuthan et al, J. Natl Cancer Inst. 41 :351, 1968), microinjection (Mueller et al , Cell 15:579, 1978), protoplast fusion (Schafher, Proc. Natl. Acad. Sci. USA 77:2163-7, 1980), or pellet guns (Klein et al , Nature 327:70, 1987). Alternatively, the cDNA can be introduced by infection with virus vectors. Systems are developed that use, for example, retroviruses (Bernstein et al., Gen. Eng. 7:235, 1985), adenoviruses (Ahmad et al. , J. Virol 57:267, 1986), or Herpes virus (Spaete et al , Cell 30:295, 1982). These eukaryotic expression systems can be used for studies of the Anophelin gene and mutant forms of this gene, the Anophelin protein and mutant forms of this protein.

Using the above techniques, the expression vectors containing the Anophelin gene or cDNA sequence or fragments or variants or mutants thereof can be introduced into human cells, mammalian cells from other species or non-mammalian cells as desired. The choice of cell is determined by the purpose of the treatment. For example, monkey COS cells (Gluzman, Cell 23: 175-82, 1981) that produce high levels of the SV40 T antigen and permit the replication of vectors containing the SV40 origin of replication may be used. Similarly, Chinese hamster ovary (CHO), mouse NIH 3T3 fibroblasts or human fibroblasts or lymphoblasts may be used.

Expression of the Anophelin protein, or fragments of variants thereof, in eukaryotic cells may be used as a source of proteins to raise antibodies. The Anophelin protein may be extracted following release of the protein into the supernatant as described above, or, the cDNA sequence may be incorporated into a eukaryotic expression vector and expressed as a chimeric protein with, for example, β-globin. Antibody to β-globin is thereafter used to purify the chimeric protein. Corresponding protease cleavage sites engineered between the β-globin gene and the cDNA are then used to separate the two polypeptide fragments from one another after translation. One useful expression vector for generating β-globin chimeric proteins is pSG5 (Stratagene, La Jolla, CA). This vector encodes rabbit β-globin.

The recombinant cloning vector then comprises the selected DNA of the DNA sequences disclosed herein for expression in a suitable host. The DNA is operatively linked in the vector to an expression control sequence in the recombinant DNA molecule so that the anophelin polypeptide can be expressed. The expression control sequence may be selected from the group consisting of sequences that control the expression of genes of prokaryotic or eukaryotic cells and their viruses and combinations thereof. The expression control sequence may be specifically selected from the group consisting of the lac system, the trp system, the tac system, the trc system, major operator and promoter regions of phage lambda, the control region of fd coat protein, the early and late promoters of SV40, promoters derived from polyoma, adenovirus, retrovirus, baculovirus and simian virus, the promoter for 3-phosphoglycerate kinase, the promoters of yeast acid phosphatase, the promoter of the yeast alpha-mating factors and combinations thereof.

The host cell, which may be transfected with the vector disclosed herein, may be selected from the group consisting of bacteria, yeast, fungi, plant, insect, mouse or other animal subject; or human tissue cells. It is appreciated that for mutant or variant DNA sequences, similar systems are employed to express and produce the mutant or variant product.

EXAMPLE 19 Production of Anti-Anophelin Antibodies Monoclonal or polyclonal antibodies may be produced to either the normal anophelin protein, or variants, fragments and mutant forms thereof. Optimally, antibodies raised against anophelin will specifically detect anophelin protein. That is, antibodies raised against anophelin protein would recognize and bind anophelin protein and would not substantially recognize or bind to other proteins found in mosquito cells. The determination that an antibody specifically detects anophelin is made by any one of a number of standard immunoassay methods; for instance, the Western blotting technique (Sambrook et al , Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, New York, 1989). To determine that a given antibody preparation (such as one produced in a mouse against anophelin) specifically detects the anophelin protein by Western blotting, total cellular protein is extracted from mosquito cells (for example, a salivary gland extract prepared as described in Example 1) and electrophoresed on a sodium dodecyl sulfate- polyacrylamide gel. The proteins are then transferred to a membrane (for example, nitrocellulose) by Western blotting, and the antibody preparation is incubated with the membrane. After washing the membrane to remove non-specifically bound antibodies, the presence of specifically bound antibodies is detected by the use of an anti-mouse antibody conjugated to an enzyme such as alkaline phosphatase; application of the substrate 5-bromo-4-chloro-3-indolyl phosphate/nitro blue tetrazolium results in the production of a dense blue compound by immuno- localized alkaline phosphatase. Antibodies which specifically detect anophelin will, by this technique, be shown to bind to the anophelin protein band (which will be localized at a given position on the gel determined by its molecular weight). Non-specific binding of the antibody to other proteins may occur and may be detectable as a weak signal on the Western blot. The nonspecific nature of this binding will be recognized by one skilled in the art by the weak signal obtained on the Western blot relative to the strong primary signal arising from the specific antibody-anophelin protein binding.

Antibodies that specifically bind to anophelin belong to a class of molecules that are referred to herein as "specific binding agents." Specific binding agents that are capable of specifically binding to anophelin may include polyclonal antibodies, monoclonal antibodies (including humanized monoclonal antibodies) and fragments of monoclonal antibodies such as Fab, F(ab')2 and Fv fragments, as well as any other agent capable of specifically binding to anophelin. Substantially pure anophelin protein suitable for use as an immunogen is isolated from the transfected or transformed cells as described above. Concentration of protein in the final preparation is adjusted, for example, by concentration on an Amicon filter device, to the level of a few micrograms per milliliter. Monoclonal or polyclonal antibodies to the protein can then be prepared as follows.

Monoclonal Antibody Production by Hybridoma Fusion

Monoclonal antibody to epitopes of the anophelin protein identified and isolated as described can be prepared from murine hybridomas according to the classical method of Kohler and Milstein (Nature 256:495, 1975) or derivative methods thereof. Briefly, a mouse is repetitively inoculated with a few micrograms of the selected protein over a period of a few weeks. The mouse is then sacrificed, and the antibody-producing cells of the spleen isolated. The spleen cells are fused by means of polyethylene glycol with mouse myeloma cells, and the excess unfused cells destroyed by growth of the system on selective media comprising aminopterin (HAT media). The successfully fused cells are diluted and aliquots of the dilution placed in wells of a microtiter plate where growth of the culture is continued. Antibody-producing clones are identified by detection of antibody in the supernatant fluid of the wells by immunoassay procedures, such as ELISA, as originally described by Engvall (Enzymol 70:419, 1980), and derivative methods thereof. Selected positive clones can be expanded and their monoclonal antibody product harvested for use. Detailed procedures for monoclonal antibody production are described in Harlow and Lane (Antibodies, A Laboratory Manual, Cold Spring Harbor Laboratory, New York, 1988). In addition, protocols for producing humanized forms of monoclonal antibodies (for therapeutic applications) and fragments of monoclonal antibodies are known in the art.

Polyclonal Antibody Production by Immunization Polyclonal antiserum containing antibodies to heterogeneous epitopes of a single protein can be prepared by immunizing suitable animals with the expressed protein, which can be unmodified or modified to enhance immunogenicity. Effective polyclonal antibody production is affected by many factors related both to the antigen and the host species. For example, small molecules tend to be less immunogenic than others and may require the use of carriers and adjuvant. Also, host animals vary in response to site of inoculations and dose, with both inadequate or excessive doses of antigen resulting in low titer antisera. Small doses (ng level) of antigen administered at multiple intradermal sites appears to be most reliable. An effective immunization protocol for rabbits can be found in Vaitukaitis et al. (J. Clin. Endocrinol. Metab. 33:988-91 , 1971).

Booster injections can be given at regular intervals, and antiserum harvested when antibody titer thereof, as determined semi-quantitatively, for example, by double immunodiffusion in agar against known concentrations of the antigen, begins to fall. See, for example, Ouchterlony et al. (Handbook of Experimental Immunology, Wier, D. (ed.) Chapter 19. Blackwell, 1973). Plateau concentration of antibody is usually in the range of 0.1 to 0.2 mg/ml of serum (about 12 μM). Affinity of the antisera for the antigen is determined by preparing competitive binding curves, as described, for example, by Fisher (Manual of Clinical Immunology, Chapter 42, 1980).

Antibodies Raised against Synthetic Peptides

A third approach to raising antibodies against anophelin is to use synthetic peptides synthesized on a commercially available peptide synthesizer based upon the predicted amino acid sequence of the anophelin protein, for example SEQ ID NOs 3-5. The chemical synthesis described in EXAMPLES 6 and 22 for example may be used to generate a synthetic anophelin protein.

Antibodies Raised by Injection of Anophelin cDNA

Antibodies may be raised against the anophelin protein by subcutaneous injection of a DNA vector which expresses the anophelin protein into laboratory animals, such as mice. Delivery of the recombinant vector into the animals may be achieved using a hand-held form of the Biolistic system (Sanford et al , Paniculate Sci. Technol. 5:27-37, 1987) as described by Tang et al (Nature 356: 152-4, 1992). Expression vectors suitable for this purpose may include those which express the Anophelin cDNA under the transcriptional control of either the human β-actin promoter or the cytomegalovirus (CMV) promoter.

Antibody preparations prepared according to these protocols are useful in quantitative immunoassay s which determine concentrations of antigen-bearing substances in biological samples; hey are also used semi-quantitatively or qualitatively to identify the presence of antigen in a biological sample.

EXAMPLE 20 Use of Anophelin to Inhibit Thrombin Activity and Platelet Aggregation

One major application of the Anophelin cDNA and protein sequence information presented herein is in the area of inhibiting the formation of blood clots, and helping dissolve them once formed. Using anophelin (or variants or fragments thereof) is advantageous over other therapies because it contains no cysteine residues, making its chemical and recombinant synthesis less complicated.

Delivery of the Therapeutic Molecules

For administration to a subject, purified therapeutically (biologically) active molecules are generally combined with a pharmaceutically acceptable carrier. Pharmaceutical preparations may contain only one type of therapeutic molecule, or may be composed of a combination of several types of therapeutic molecules. In general, the nature of the carrier will depend on the particular mode of administration being employed. For instance, parenteral formulations usually comprise iηjectable fluids that include pharmaceutically and physiologically acceptable fluids such as water, physiological saline, balanced salt solutions, aqueous dextrose, glycerol or the like as a vehicle. For solid compositions (e.g. , powder, pill, tablet, or capsule forms), conventional non-toxic solid carriers can include, for example, pharmaceutical grades of mannitol, lactose, starch, or magnesium stearate. In addition to biologically-neutral carriers, pharmaceutical compositions to be administered can contain minor amounts of non-toxic auxiliary substances, such as wetting or emulsifying agents, preservatives, and pH buffering agents and the like, for example sodium acetate or sorbitan monolaurate.

As is known in the art, protein-based pharmaceuticals may be only inefficiently delivered through ingestion. However, pill-based forms of pharmaceutical proteins may be administered subcutaneously, particularly if formulated in a slow-release composition. Slow-release formulations may be produced by combining the target protein with a biocompatible matrix, such as cholesterol. Another possible method of administering protein pharmaceuticals is through the use of mini osmotic pumps. As stated above a biocompatible carrier would also be used in conjunction with this method of delivery.

It is also contemplated that the therapeutic molecules could be delivered to cells in the nucleic acid form and subsequently translated by the host cell (for example as in gene therapy). This could be done, for example through the use of viral vectors or liposomes. The use of liposomes as a delivery vehicle is one delivery method of particular interest. The liposomes fuse with the target site and deliver the contents of the lumen intracellularly. The liposomes are maintained in contact with he target cells for a sufficient time for fusion to occur, using various means to maintain contact, such as isolation and binding agents. Liposomes may be prepared with purified proteins or peptides that mediate fusion of membranes, such as Sendai virus or influenza virus. The lipids may be any useful combination of known liposome forming lipids, including cationic lipids, such as phosphatidylcholine. Other potential lipids include neutral lipids, such as cholesterol, phosphatidyl serine, phosphatidyl glycerol, and the like. For preparing the liposomes, the procedure described by Kato et al (J. Biol Chem. 266:3361 , 1991) may be used.

The pharmaceutical compositions disclosed herein may be administered by any means that achieve their intended purpose. Amounts and regimens for the administration of the therapeutic molecules, or a therapeutically active fragment thereof, can be determined readily by those with ordinary skill in the clinical art of treating diseases associated with platelet aggregation and blood clot formation. For use in treating these conditions, molecules are administered in an amount effective to inhibit α-fhrombin, platelet aggregation and blood clot formation. Typical amounts initially administered would be those amounts adequate to achieve concentrations in the blood which have been found to achieve the desired effect in vitro. The peptides or proteins may be administered to a subject in vivo, for example through systemic administration, such as intravenous or intraperitoneal administration. Also, the peptides or proteins may be administered intralesionally: i.e. the peptide or protein is injected directly into the lesion (blood clot) or affected area, particularly using endovasular catheters. Alternatively, the peptides or proteins can be placed in a stent or other intravascular implant, or expressed from cells that have been transformed to express the anophelin (where the cells may be carried by or placed within the implant).

Effective doses of the therapeutic molecules will vary depending on the nature and severity of the condition to be treated, the age and condition of the patient and other clinical factors. Thus, the final determination of the appropriate treatment regimen will be made by the attending clinician. Typically, the dose range will be from about 0.1 μg/kg body weight to about 100 mg/kg body weight. Other suitable ranges include doses of from about 1 μg/kg to 10 mg/kg body weight. The dosing schedule may vary from once a week to daily depending on a number of clinical factors, such as the subject's sensitivity to the protein. In the case of a more aggressive thrombotic condition, it may be preferable to administer doses such as those described above by alternate routes including intravenously or intrathecally. Continuous infusion may also be appropriate, for example at 0.001- 10 mg/kg/hr.

As mentioned above the anophelin protein will be useful for the treatment of blood clots by inhibiting α-thrombin and platelet aggregation. Such treatment should be useful for treating such diseases as myocardial infarction, stroke, pulmonary embolism, deep vein thrombosis, peripheral arterial occlusion, disseminated intravascular coagulation, cardiovascular and cerebrovascular thrombosis. This treatment will also be effective propholactically in preventing blood clot formation, in situations where clotting is not desired such as thrombosis associated with post- operative trauma, obesity, pregnancy, side effects of oral contraceptives, prolonged immobilization, hypercoaguable states associated with hematalogic, immunologic or rheumatological disorders, unstable angina, arteriosclerosis, a reblockage of vessels after angioplasty with a balloon catheter, or blood clotting in hemodialysis.

EXAMPLE 21 Peptide Modifications

Also disclosed are biologically active molecules that mimic the action (mimetics) of the anophelin protein disclosed herein. Synthetic embodiments of naturally-occurring peptides, as well as analogues (non-peptide organic molecules), derivatives (chemically functionalized peptide molecules obtained starting with the disclosed peptide sequences) and variants (homologs) of these peptides that specifically inhibit the conversion assay reaction are disclosed. Each peptide ligand disclosed herein is comprised of a sequence of amino acids, which may be either L- and/or D- amino acids, naturally occurring and otherwise. Peptides may be modified by a variety of chemical techniques to produce derivatives having essentially the same activity as the unmodified peptides, and optionally having other desirable properties. For example, carboxylic acid groups of the peptide, whether carboxyl-terminal or side chain, may be provided in the form of a salt of a pharmaceutically-acceptable cation or esterified to form a C1-C16 ester, or converted to an amide of formula NR1R2 wherein Rl and R2 are each independently H or C1-C16 alkyl, or combined to form a heterocyclic ring, such as a 5- or 6- membered ring. Amino groups of the peptide, whether amino-terminal or side chain, may be in the form of a pharmaceutically-acceptable acid addition salt, such as the HC1, HBr, acetic, benzoic, toluene sulfonic, maleic, tartaric and other organic salts, or may be modified to C1-C16 alkyl or dialkyl amino or further converted to an amide. Hydroxyl groups of the peptide side chain may be converted to C1-C16 alkoxy or to a Cl-

C16 ester using well-recognized techniques. Phenyl and phenolic rings of the peptide side chain may be substituted with one or more halogen atoms, such as fluorine, chlorine, bromine or iodine, or with C1-C16 alkyl, C1-C16 alkoxy, carboxylic acids and esters thereof, or amides of such carboxylic acids. Methylene groups of the peptide sidechains can be extended to homologous C2-C4 alkylenes. Thiols can be protected with any one of a number of well-recognized protecting groups, such as acetamide groups. Those skilled in the art will also recognize methods for introducing cyclic structures into the peptides disclosed herein to select and provide conformational constraints to the structure that result in enhanced stability. For example, a carboxyl-terminal or amino-terminal cysteine residue can be added to the peptide, so that when oxidized the peptide will contain a disulfide bond, thereby generating a cyclic peptide. Other peptide cyclizing methods include the formation of thioethers and carboxyl- and amino-terminal amides and esters. To maintain an optimally functional peptide, particular peptide variants will differ by only a small number of amino acids from the peptides disclosed herein. Such variants may have deletions (for example of 1-3 or more amino acid residues), insertions (for example of 1-3 or more residues), or substitutions that do not interfere with the desired activity of the peptides. Substitutional variants are those in which at least one residue in the amino acid sequence has been removed and a different residue inserted in its place. For example, such variants can have amino acid substitutions of single residues, for example 1, 3, 5 or even 10 substitutions in the full-length anophelin protein (SEQ ID NOs 3-5).

Peptidomimetic and organomimetic embodiments are also disclosed, whereby the fhree- dimensional arrangement of the chemical constituents of such peptido- and organomimetics mimic the three-dimensional arrangement of the peptide backbone and component amino acid sidechains in the peptide, resulting in such peptido- and organomimetics of the peptides having substantial anti-α- fhrombin and anti-platelet aggregation activities. For computer modeling applications, a pharmacophore is an idealized, three-dimensional definition of the structural requirements for biological activity. Peptido- and organomimetics can be designed to fit each pharmacophore with current computer modeling software (using computer assisted drug design or CADD). See Walters, "Computer- Assisted Modeling of Drugs" , in Klegerman & Groves, eds., 1993, Pharmaceutical Biotechnology, Interpharm Press: Buffalo Grove, IL, pp. 165-174 and Principles of Pharmacology (ed. Munson, 1995), chapter 102 for a description of techniques used in CADD. Also disclosed are mimetics prepared using such techniques that produce either peptides or conventional organic pharmaceuticals that retain the biological activity of the ligand or receptor.

The above described mimetics are examined for their anti-α-thrombin, anti-platelet aggregation and anti-blood clotting activity. Such activities can be readily determined using the assays disclosed herein, for example using the methods described in EXAMPLES 2, 7, and 9. Suitable mimetics would demonstrate anophelin biological activity as defined above.

EXAMPLE 22 Method for Generating Mimetics

Compounds or other molecules which mimic normal anophelin function, such as compounds which interacts with α-thrombin to inhibit platelet aggregation and blood clotting, can be identified and/or designed. These compounds or molecules are known as mimetics, because they mimic the biological activity of the normal protein.

Crystallography To identify the amino acids that interact between anophelin and α-thrombin, anophelin is co-crystallized in the presence of α-thrombin. One method that can be used is the hanging drop method. In this method, a concentrated salt, α-thrombin and anophelin protein solution is applied to the underside of a lid of a multiwell dish. A range of concentrations may need to be tested. The lid is placed onto the dish, such that the droplet "hangs" from the lid. As the solvent evaporates, a protein crystal is formed, which can be visualized with a microscope. This crystallized structure is then subjected to X-ray diffraction or NMR analysis which allows for the identification of the amino acid residues that are in contact with one another. The amino acids that contact α-thrombin establish a pharmacophore that can then be used to identify drugs that interact at that same site.

Identification of drugs

Once these amino acids have been identified, one can screen synthetic drug databases (which can be licensed from several different drug companies), to identify drugs that interact with the same amino acids of α-thrombin that anophelin interacts with. Moreover, structure activity relationships and computer assisted drug design can be performed as described in Remington, The Science and Practice of Pharmacy, Chapter 28.

Designing synthetic peptides

In addition, synthetic peptides can be designed from the sequence of α-thrombin that interacts with anophelin. Several different peptides could be generated from this region. This could be done with or without the crystallography data. However, once crystallography data is available, peptides can also be designed that bind better than anophelin. The chimeric peptides may be expressed recombinantly, for example in E. coll One advantage of synthetic peptides over monoclonal antibodies is that they are smaller, and therefore diffuse easier, and are not as likely to be immunogenic. Standard mutagenesis of such peptides can also be performed to identify variant peptides having even greater anti-platelet aggregation and anti- blood clotting activity. After synthetic drugs or peptides that bind to α-thrombin have been identified, their ability to inhibit platelet aggregation and blood clotting, can be tested as described in the above EXAMPLES. Those that are positive would be good candidates for therapies, such as inhibiting-α- fhrombin is desired.

EXAMPLE 23

Peptide Synthesis and Purification

The disclosed peptides (and variants and fragments thereof) can be chemically synthesized using the methods described above in EXAMPLE 6, or by any of a number of manual or automated methods of synthesis known in the art. For example, solid phase peptide synthesis (SPPS) is carried out on a 0.25 millimole (mmole) scale using an Applied Biosystems Model 431 A Peptide

Synthesizer and using 9-fluorenylmethyloxycarbonyl (Fmoc) amino-terminus protection, coupling with dicyclohexylcarbodiimide/ hydroxybenzotriazole or 2-(lH-benzo-triazol-l-yl)-l,l,3,3- tetramefhyluronium hexafluorophosphate/ hydroxybenzotriazole (HBTU/HOBT), and using p- hydroxymefhylphenoxymefhylpolystyrene (HMP) or Sasrin resin for carboxyl-terminus acids or Rink amide resin for carboxyl-terminus amides.

Fmoc-derivatized amino acids are prepared from the appropriate precursor amino acids by tritylation and triphenylmethanol in trifluoroacetic acid, followed by Fmoc derivitization as described by Atherton et al. (Solid Phase Peptide Synthesis, IRL Press: Oxford, 1989).

Sasrin resin-bound peptides are cleaved using a solution of 1 % TFA in dichloromethane to yield the protected peptide. Where appropriate, protected peptide precursors are cyclized between the amino- and carboxyl-termini by reaction of the amino-terminal free amine and carboxyl-terminal free acid using diphenylphosphorylazide in nascent peptides wherein the amino acid sidechains are protected.

HMP or Rink amide resin-bound products are routinely cleaved and protected sidechain- containing cyclized peptides deprotected using a solution comprised of trifluoroacetic acid (TFA), optionally also comprising water, thioanisole, and ethanedithiol, in ratios of 100 : 5 : 5 : 2.5, for 0.5 - 3 hours at room temperature.

Crude peptides are purified by preparative high pressure liquid chromatography (HPLC), for example using a Waters Delta-Pak C18 column and gradient elution with 0.1 % TFA in water modified with acetonitrile. After column elution, acetonitrile is evaporated from the eluted fractions, which are then lyophilized. The identity of each product so produced and purified may be confirmed by fast atom bombardment mass spectroscopy (FABMS) or electrospray mass spectroscopy (ESMS).

In view of the many possible embodiments to which the principles of our disclosure may be applied, it should be recognized that the illustrated embodiments are only particular examples of the disclosure and should not be taken as a limitation on the scope of the disclosure. Rather, the scope of the disclosure is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims.

Claims

We claim:

1. A purified or synthetic protein having anophelin biological activity, and comprising an amino acid sequence selected from the group consisting of:

(a) the amino acid sequence shown in SEQ ID NO 5; (b) amino acid sequences that differ from those specified in (a) by one or more conservative amino acid substitutions that retain anophelin biological activity;

(c) fragments of the amino acid sequence shown in SEQ ID NO 5 that retain anophelin biological activity; and

(d) amino acid sequences having at least 60% sequence identity to the sequences specified in (a), (b) and (c) that retain anophelin biological activity.

2. The protein of claim 1 , wherein the amino acid sequence comprises an amino acid sequence selected from the group consisting of:

(a) the amino acid sequence shown in SEQ ID NO 3;

(b) amino acid sequences that differ from those specified in (a) by one or more conservative amino acid substitutions that retain anophelin biological activity;

(c) fragments of the amino acid sequence shown in SEQ ID NO 3 that retain anophelin biological activity; and

(d) amino acid sequences having at least 60% sequence identity to the sequences specified in (a), (b) and (c) that retain anophelin biological activity. 3. The protein of claim 1 , wherein the amino acid sequence comprises a sequence selected from the group consisting of:

(a) the amino acid sequence shown in SEQ ID NO 4;

(b) amino acid sequences that differ from those specified in (a) by one or more conservative amino acid substitutions that retain anophelin biological activity; (c) fragments of the amino acid sequence shown in SEQ ID NO 4 that retain anophelin biological activity; and (d) amino acid sequences having at least 60% sequence identity to the sequences specified in (a), (b) and (c) that retain anophelin biological activity.

4. The protein of claim 1, wherein the protein is at least 50% pure. 5. The protein of claim 1 , wherein the protein is at least 75% pure.

6. The protein of claim 1 , wherein the protein is at least 95 % pure.

7. An isolated nucleic acid molecule encoding a protein according to claim 1.

8. An isolated nucleic acid molecule encoding a protein according to claim 2.

9. An isolated nucleic acid molecule encoding a protein according to claim 3. 10. The isolated nucleic acid of claim 7, further comprising a promoter sequence operably linked to the nucleic acid of claim 7. - so ¬

i l . An isolated nucleic acid molecule including at least 30 contiguous nucleotides of a sequence selected from the group consisting of:

(a) SEQ ID NO 1 or its complementary strand; and

(b) SEQ ID NO 2 or its complementary strand. 12. An isolated nucleic acid molecule according to claim 11 wherein the nucleic acid molecule includes at least 35 contiguous nucleotides of the selected sequence.

13. An isolated nucleic acid molecule according to claim 11 wherein the nucleic acid molecule includes at least 50 contiguous nucleotides of the selected sequence.

14. A recombinant vector including a nucleic acid molecule according to claim 11. 15. A transgenic host cell containing a recombinant vector according to claim 14.

16. An isolated nucleic acid molecule including the sequence selected from the group consisting of:

(a) SEQ ID NO 1 or its complementary strand; and

(b) SEQ ID NO 2 or its complementary strand. 17. An isolated nucleic acid molecule that:

(a) is at least 60% homologous to SEQ ID NO 1 or SEQ ID NO 2; and

(b) encodes a protein having anophelin biological activity.

18. A recombinant vector including a nucleic acid molecule according to claim 17.

19. A transgenic cell produced by introducing into a cell a recombinant vector according to claim 18.

20. A purified peptide encoded by the nucleic acid molecule according to claim 17.

21. The peptide of claim 20 wherein the peptide has an amino acid sequence as shown in SEQ ID NO 5.

22. An isolated nucleic acid molecule having a nucleotide sequence selected from the group consisting of the sequences shown in:

(a) SEQ ID NO 1 or its complementary strand;

(b) SEQ ID NO 2 or its complementary strand; and

(c) Sequences which hybridize under conditions of at least 75 % stringency to the sequences defined in (a) or (b). 23. The nucleic acid molecule of claim 22 wherein the nucleic acid molecule encodes a peptide capable of anophelin biological activity.

24. An isolated nucleic acid molecule according to claim 22(c) wherein the nucleic acid molecule hybridizes under conditions of at least 90% stringency to the sequences defined in claim 22(a) or claim 22(b). 25. A purified Anopheles albimanus anophelin protein.

26. An isolated nucleic acid molecule which encodes a protein according to claim 25.

27. An extract containing water soluble components of a salivary gland homogenate of a mosquito of Anopheles albimanus generated by:

(a) sonicating Anopheles albimanus salivary glands in buffer containing about 10 mM sodium phosphate pH 7.0, and about 150 mM NaCl to generate the homogenate; and (b) centrifuging the homogenate to separate soluble from insoluble components.

28. The extract of claim 27, wherein the extract contains anophelin biological activity.

29. The extract of claim 28, wherein the extract contains the protein of claim 4.

30. A purified protein having anophelin biological activity, wherein the protein can be purified from the extract of claim 27; has a molecular weight of about 6.5 kD, is an acidic protein with a pl of about 3.5, lacks cysteine residues, has non-covalent interactions with both the anion binding exosite (TABE) and the catalytic site of α-thrombin, has anti-thrombin activity with a K, of about 34 pM in the absence of salt, antagonizes clotting and inhibits platelet aggregation.

31. A purified protein according to claim 1 , wherein the purified protein is prepared by chemical synthesis followed by HPLC purification and concentration. 32. An isolated oligonucleotide comprising a sequence selected from the group consisting of:

(a) at least 30 contiguous nucleotides of the sequence shown in SEQ ID NO 1 or the complementary strand of said sequence;

(b) at least 40 contiguous nucleotides of the sequence shown in SEQ ID NO 1 or the complementary strand of said sequence;

(c) at least 50 contiguous nucleotides of the sequence shown in SEQ ID NO 1 or the complementary strand of said sequence;

(d) at least 21 contiguous nucleotides of the sequence shown in SEQ ID NO 2 or the complementary strand of said sequence; (e) at least 25 contiguous nucleotides of the sequence shown in SEQ ID NO 2 or the complementary strand of said sequence;

(f) at least 30 contiguous nucleotides of the sequence shown in SEQ ID NO 2 or the complementary strand of said sequence; and

(g) at least 50 contiguous nucleotides of the sequence shown in SEQ ID NO 2 or the complementary strand of said sequence.

33. A purified peptide encoded by a nucleic acid molecule according to claim 32.

34. The purified peptide of claim 33, wherein the purified peptide is prepared by chemical synthesis followed by HPLC purification and concentration.

35. A specific binding agent capable of specifically binding to a Anopheles albimanus anophelin protein. 36 The specific binding agent of claim 35 wherein the specific binding agent is selected from the group consistmg of polyclonal antibodies, monoclonal antibodies and fragments of monoclonal antibodies

37 A composition comprising a therapeutically effective amount of a protein havmg anophelin biological activity and a pharmaceutically acceptable carrier

38 The composition of claim 37, further comprising one or more anti-thrombin compounds

39 The composition of claim 37, wherein the protein is the protein of claim 25

40 The composition of claim 37, wherein the protein is the protein of claim 31 41 A composition comprising a therapeutically effective amount of the extract of claim

27 and a pharmaceutically acceptable carrier

42 A composition compnsmg a therapeutically effective amount of the peptide of claim 21 , and a pharmaceutically acceptable carrier

43 A composition comprising a therapeutically effective amount of the peptide of claim 34, and a pharmaceutically acceptable carrier

44 A method of inhibiting thrombin activity comprising contacting blood with an effective amount of a purified protem having anophelm biological activity

45 A method of inhibiting thrombin activity comprising contacting blood with an effective amount of a composition having anophehn biological activity 46 The method of claim 45, wherein the composition is the composition of claim 37

47 The method of claim 45, wherem the composition is the composition of claim 41

48 A method of inhibiting thrombin activity, comprising administering a therapeutically effective amount of a protem having anophelin biological activity to a subject, sufficient to inhibit thrombin activity in the subject 49 The method of claim 48, wherem the protein is provided in the composition of claim

37

50 The method of 48, wherem administering a therapeutically effective amount of the protem comprises administering a therapeutically effective amount of the protein to a subject in whom pathological thrombosis is not desired 51 The method of claim 50, wherein the subject suffers from a condition selected from the group consisting of myocardial infarction, stroke, pulmonary embolism, deep vein thrombosis, peπpheral arterial occlusion, dissemmated mtravascular coagulation, cardiovascular and cerebrovascular thrombosis, thrombosis associated with post-operative trauma, obesity, pregnancy, side effects of oral contraceptives, prolonged immobilization, and hypercoaguable states associated with hematalogic, immunologic or rheumatological disorders

52. The method of claim 50, wherein the subject is someone with unstable angina, arteriosclerosis, a reblockage of vessels after angioplasty with a balloon catheter, or blood clotting in hemodialysis.

53. A method of inhibiting thrombin activity, comprising administering a therapeutically effective amount of the composition of claim 37 to a subject.

54. The method of claims 48-53 wherein the subject is a human.

55. The method of claim 44, wherein inhibiting thrombin activity involves inhibiting platelet aggregation in extracorporeal blood, comprising admixing an effective amount of the composition of claim 37, with the extracorporeal blood. 56. The method of claim 44, wherein inhibiting thrombin activity involves inhibiting platelet aggregation in stored platelets comprising storing platelets in the presence of an effective amount of the composition of claim 37.

57. The method of claim 44, wherein inhibiting thrombin activity involves inhibiting platelet aggregation in a subject comprising administering an effective amount of the composition of claim 37 to the subject.

58. A purified protein having anophelin biological activity, wherein the protein is isolated from a salivary gland extract of Anopheles albimanus mosquitoes at a purity of at least 50% .

59. The purified protein of claim 58, wherein the protein is synthesized chemically, and has a purity of at least 90% . 60. The purified protein of claim 58, wherein the protein is synthesized chemically, and has a purity of at least 95 % .

61. The compositions of claims 37-43, for use in inhibiting thrombin activity.

62. The composition of claim 61 , for use in a subject, in an amount sufficient to inhibit thrombin activity in the subject. 63. The composition of claim 61, for use in a subject in whom pathological thrombosis is not desired.

64. The composition of claim 62, for use in the treatment of myocardial infarction, stroke, pulmonary embolism, deep vein thrombosis, peripheral arterial occlusion, disseminated intravascular coagulation, cardiovascular and cerebrovascular thrombosis, thrombosis associated with post-operative trauma, obesity, pregnancy, side effects of oral contraceptives, prolonged immobilization, or hypercoaguable states associated with hematalogic, immunologic or rheumatological disorders.

65. The composition of claim 62, for use in the treatment of unstable angina, arteriosclerosis, a reblockage of vessels after angioplasty with a balloon catheter, or blood clotting in hemodialysis.

66. The composition of claim 62, for use in a human subject.

67. The composition of claim 61 , for use in inhibiting platelet aggregation in extracorporeal blood by admixing an effective amount of the composition with the extracorporeal blood.

68. The composition of claim 61, for use in inhibiting platelet aggregation in stored platelets.