TREATMENT OF ENDOTOXEMIA

Abstract: Disclosed is a method for treating endotoxemia and other types of infection by gram-negative or similar pathogens. The method includes providing a therapeutic agent that is a non-immunoglobulin polypeptide, soluble in the circulation, and has the ability to bind endotoxin-related substances; and administering to the circulation of a subject a therapeutic amount of the agent. This conjugate has reduced toxicity and reduced pathogenicity relative to unconjugated endotoxin-related substances. In preferred embodiments, the therapeutic agent is at least a portion of the extracellular portion of the scavenger receptor protein.

Description: TREATMENT OF ENDOTOXEMTA BACKGROUND OF THE INVENTION The technical field of this invention is the diagnosis and treatment of endotoxemia and related disease states and/ in particular, relates to the inactivation of endotoxin-related substances by the systemic administration of genetically engineered or chemically modified native polypeptides of the scavenger receptor protein. Endotoxins are the lipopolysaccharides (LPS) uniquely found on the outer surface of gram-negative bacteria. They are responsible in large part for the pathophysiological phenomena associated with gram- negative infections. The outer monolayer of the outer membrane of most gram-negative bacteria includes a unique hydrophobic component called lipid A which is the active moiety of lipopolysaccharide. The jsn-l 2-diacylglycerol moiety of classical membrane phospholipids is absent in lipid A, and the acyl chains linked to its glucosamine backbone differ from those of glycerolphospholipids in that they are 2-6 carbon atoms shorter and contain an R-3-hydroxyl substituent. The unique structure of Lipid A reflects its role in membrane assembly and function, including providing resistance to phospholipases. Lipid A and its precursor lipid IV^ are also potent activators of macrophages, resulting in the rapid production of a wide array of immune mediators such as interleukin-1, tumor necrosis factor, and platelet activating factor, among others (see, Raetz (1990) Ann. Rev. Biochem. 59:129-170). When tumor necrosis factor is rapidly secreted into the system, a shock syndrome (septic, endotoxic, or toxic shock or endotoxemia) may occur (see e.g., Beutler et al. (1986) Nature 320:584; and Old (1988) Scientific American 258:59). Incipient septic shock is characterized in part by body temperature extremes, altered mental status, a decrease in orthostatic blood pressure, decreased urine output, a decreased serum albumin concentration, and tachypnea with hypoxemia. The high morbidity associated with endotoxin-induced shock remains a major clinical problem, especially in debilitated and immunosuppressed patients. Traditional anti-shock therapy includes replacement of plasma volume with plasma expanders containing, for example, vasoactive compounds, anti-inflammatory drugs, and/or various anti-prostaglandins. However, since such measures have been only partially successful in controlling the morbidity associated with endotoxemia, other types of therapy have been developed such as the systemic administration of transforming growth factor B (PCT/US89/03162), interleukin-1 (PCT US87/02065), agonists of platelet activating factor (EP 89104429.9), and the parenteral administration of taurolidine and/or taurultam (EP 87306297.0). Immunotherapy methods have also been developed including the systemic administration of antibody to endotoxin (see, for example, U.S. Patent No. 4,120,950; PCT/US84/00688; EP 84308218.1) or to the TNF binding protein (Beutler et al. (1985) Science 229:869-871: EP 89104494.3). These immunotherapies may suffer from the disadvantages of unfavorable kinetics, short biological half-life, and the potential for anti-idiotype antibody generation that would in some cases neutralize the therapeutic antibody. Accordingly, there exists a need for improved methods of treating endotoxemia, more effective techniques for inactivating gram-negative pathogens, and therapeutic agents useful in these methods. SUMMARY OF THE INVENTION It has been discovered that endotoxin-related substances can be inactivated by being bound to a non-immunoglobulin polypeptide therapeutic agent, such as a soluble form of the scavenger receptor protein. When an endotoxin-related substance is bound to the therapeutic agent, a conjugate is formed that has reduced toxicity and reduced pathogenicity relative to the unconjugated endotoxin-related substance. "Endotoxin-related substances" as used herein refers to endotoxin, the lipopolysaccharides found on the surface of gram-negative pathogens, to endotoxin-like, lipid A-like molecules, to molecules which bind the scavenger receptor and have toxic or otherwise pathogenic effects, and to organisms which express such endotoxin, endotoxin-like, toxic, or pathogenic molecules on.their surfaces or at sites which are accessible to the soluble scavenger receptor protein. In preferred embodiments of the invention, the therapeutic agent contains an extracellular fragment of the scavenger receptor protein which is soluble. Native scavenger receptor protein is not soluble because of the presence of transmembranous and cytoplasmic domains which anchor the protein firmly within the membrane of the macrophage. One preferred embodiment of the therapeutic agent includes the collagen-binding domain of the native scavenger receptor protein. • Another embodiment includes the α-helical coiled coil domain and/or the cysteine-rich domain. Yet another embodiment includes, in addition to the collagen binding domain, the spacer domain of the scavenger receptor protein. The soluble fragment may be obtained from isolated native scavenger receptor protein that has been subjected to various biochemical cleavage techniques. Alternatively/ the fragment can be an analog produced by recombinant DNA methodologies such as a secreted form of the scavenger receptor protein. This analog can be a truncated form of the scavenger receptor protein having at least its intracellular and transmembranous domains deleted, and can have an amino acid sequence sufficiently duplicative of the amino acid sequence of a portion of the extracellular region of the scavenger receptor protein such that it binds and thereby inactivates endotoxin-related substances. In addition, the analog can be engineered to have a greater binding affinity for an endotoxin-related substance than the native scavenger receptor protein or than the extracellular fragment thereof, or can be engineered to more effectively neutralize the toxic or pathogenic effects of molecules which bind the scavenger receptor or of organsms which express such molecules on their surfaces or at sites which are accessible to the soluble receptor protein. This neutralization is the consequence of direct inactivation, steric hindrance, more rapid clearance from the circulation, or some other mechanism. In some aspects of the invention, the therapeutic agent binds specifically to the lipid A moiety of endotoxin. In other aspects, the therapeutic agent has an affinity for acetylated low density lipoprotein of about 0.5 to 5.0 microgram protein per milliliter. In addition, the therapeutic agent may be further characterized by the ability to bind chemically-modified low density lipoprotein (LDL), or negatively-charged macromolecules including polyvinylsulfate, maleyl-BSA, fucoidan, and purine polynucleotides, poly[I-C], poly[I] and poly[G] , and/or gram-negative bacteria. It has also been discovered that the therapeutic agent with the ability to bind an endotoxin-related substance can be used for treating endotoxemia or other toxemias resulting from infection by an organism expressing the endotoxin-related substance, or from the ingestion or invasion of endotoxin-related substances. The terms "endotoxemia," "toxic shock", "septic shock", and "endotoxic shock" are used herein to describe the shock syndrome resulting in response to infection by gram-negative bacteria or in response to invasion by other endotoxin-related substances. The method includes providing the therapeutic agent and administering to the circulation of a subject an endotoxemia-inhibiting, effective amount of the agent in a pharmaceutically acceptible carrier. The term "subject" as used herein refers to humans and animals. The agent binds endotoxin-related substances it encounters, thereby forming a conjugate that has reduced toxicity and pathogenicity relative to unconjugated endotoxin-related substances. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects of this invention, the various features thereof, as well as the invention itself may be more fully understood from the following description when read together with the accompanying drawings in which: FIG. 1 is a schematic representation of the type I and type II scavenger receptor proteins and their protein domains; and FIGS. 2A-2D are diagrammatic representations of the construction of plasmids used to transfect host cells with a gene encoding a soluble scavenger receptor protein; FIG. 2A shows the insertion of the myelin associated glycoprotein leader sequence into pCDNAl; FIG. 2B shows the construction of the pCDNAl/common vector; FIG. 2C shows the insertion of unique regions to create soluble scavenger receptor type I and type II in the pCDNAl-MAG vector; and FIG. 2D shows the transfer of the secreted soluble scavenger receptor gene including the MAG leader into a pRc/CMV vector. DESCRIPTION OF THE INVENTION It has been discovered that a soluble form of a scavenger receptor protein can act as a therapeutic agent by binding endotoxin-related substances, thereby inactivating them and aiding in their clearance from the circulation. The therapeutic agent can be administered to patients who are at high risk, or symptomatic, of endotoxic shock. The native scavenger receptor is a membrane bound protein taking two forms, type I and type II, both found on the surface of macrophages. This protein has an apparent molecular weight on SDS- polyacrylamide gels of about 220,000 daltons (220 kD) in the case of the type I receptor, and a binding affinity for chemically modified low density lipoprotein (LDL) such as acetylated or oxaloacetylated LDL. For example, it has a binding affinity for acetylated.LDL (Ac-LDL) of about 0.5-5.0 micrograms protein per milliliter. This protein is functional when combined with two other scavenger receptor subunits forming a trimer of subunits, each of which having an apparent molecular weight on SDS-polyacrylamide gels of about 77 kD in the case of the type I receptor, and including an asparagine (Asn)-linked carbohydrate chain. As shown in FIG. 1, each native protein subunit includes an N-terminal cytoplasmic domain and a domain which spans the membrane (transmembrane domain), followed by a spacer region, an alpha-helical coiled coil.domain, and an extracellular collagen domain. The term "collagen domain" is used herein to encompass a region of a polypeptide which is substantially analogous to that of collagen or an analog or portion thereof. Linked to the collagen domain of the type I receptor is another extracellular domain which is rich in cysteine residues ("Cys-rich" domain). TABLE I illustrates the location of the various domains within the amino acid sequence of the scavenger receptor protein. TABLE I * *based on the molecular weight of the individual amino acids Each subunit has at least one asparagine (Asn)-linked carbohydrate chain determined by treatment with various deglycosylation enzymes. By analysis of its amino acid sequence, these carbohydrate attachment sites are located in the spacer and alpha helical coiled coil domains. The assignment of residues 341-453 as a Cys-rich domain is based on the fact that it contains multiple Cys amino acids. In addition, because this domain is the most distal external domain, and because several other known cell surface receptors have Cys-rich ligand binding domains, this domain may also serve as a ligand binding site. However, since the collagen binding domain (amino acid numbers 272-343) is positively charged and since the ligands are often negatively charged, the collagen domain alternatively or additionally may participate in ligand binding. The same may be true for a portion or all of the alpha helical coiled coil in the Asn-linked sugar domain. The soluble therapeutic agent includes at least a portion of the extracellular region of the native scavenger receptor protein (amino acid nos. 77-453) responsible for binding endotoxin-related substances. This extracellular portion may include the spacer region, all or part of the a-helical coiled coil domain, all or part of the collagen binding domain, and/or all or part of the Cys-rich domain. Alternatively, the soluble protein is a recombinantly produced analog having an amino acid sequence sufficiently duplicative of the amino acid sequences of at least a portion of the extracellular region such that the protein binds endotoxin-related substances with a similar, greater, or slightly lesser affinity as the native, insoluble, membrane-bound protein or as a soluble fragment thereof. The therapeutic agent can be prepared by isolating native scavenger receptor protein from macrophages or a related cell line expressing the scavenger receptor protein on its surface, as disclosed in PCT/US89/05115, herein incorporated by reference, and then subjecting the purified protein to proteolytic cleavage to remove the intracellular and transmembranous portions of the protein from the extracellular domains. A number of proteolytic enzymes are known in the art that recognize and cleave at a particular amino acid or amino acid sequence. Such commercially available enzymes include trypsin, chymotrypsin, pepsin, Endo Lys C, and Endo Arg C. After digestion, the fragments of the protein can be isolated by any number of chromatographic methods including, differential centrifugation, affinity and column chromatography, among many others. Alternatively, the therapeutic agent can be obtained from cell lines genetically engineered to express the scavenger receptor protein or fragments thereof. For example, a nucleic acid sequence encoding the extracellular domain of the scavenger receptor protein, or a particular fragment thereof, may be used to produce a protein in an appropriate microbial, yeast, insect, or mammalian host cell. To accomplish this, the sequence is inserted into an expression system such as a vector which is suitable for transforming or transfecting a prokaryotic (bacterial) or eucaryotic (yeast, insect, or mammalian) host cell. Some useful mammalian host cells include Chinese Hamster Ovary (CHO) cells, COS M6 cells, and THP-1 cells. ' These standard procedures have been followed to produce well-known proteins such as insulin, interferons, human growth hormone, and the like. Similar procedures, or obvious modifications thereof, can also be employed to prepare the scavenger receptor protein and fragments or analogs thereof in accord with the subject invention, using the nucleic acid sequence for the scavenger receptor protein set forth below in the sequence listing as SEQ ID NO: 1 and SEQ ID NO: 3. A major portion of the amino acid sequence of the protein has been derived from the nucleic acid sequence of a gene encoding the protein. However, because more than one nucleotide triplet (codon) can encode a single amino acid, a number of different nucleotide sequences can encode a single protein. Hence, the peptide fragment disclosed herein may be encoded by nucleic acid sequences which are functionally equivalent to the one shown above, and which may also be prepared by known synthetic procedures. Accordingly, the invention includes such functionally equivalent nucleotide sequences. In addition, one skilled in the art, knowing the amino acid sequence of the receptor protein, could synthetically or biosynthetically prepare a functionally equivalent analog of the receptor protein of the invention having substantially the same biological activity. In particular, fragments of the protein, especially portions of the extracellular domain, can be obtained for the disclosures herein without undue experimentation. Thus, the scope of the invention includes the amino acid sequences and corresponding nucleic acid sequences depicted herein, as well as all functionally equivalent amino acid sequences (and corresponding nucleic acid sequences) for molecules with substantially the same biological activities as the soluble scavenger receptor protein. For example, one embodiment of the invention includes a polypeptide having an amino acid sequence sufficiently duplicative of the amino acid sequence of a subunit of the soluble scavenger receptor protein such that the polypeptide, when trimerized with two other like polypeptides or with two subunits of the scavenger receptor protein, bind chemically modified forms of LDL and endotoxin-related substances with the same or greater affinity than the native protein. The scavenger receptor protein can be used for a variety of diagnostic and therapeutic purposes. In a simple embodiment, insoluble or soluble receptor proteins are harvested and purified from eucaryotic cells which are preferably mammalian, or from eucaryotic or prokaryotic cells engineered by recombinant means to produce such proteins, and used in both radiolabelled and unlabelled states in competitive binding assays to test for the presence of the receptor. The receptor protein, or fragments or analogs thereof, can also be fixed to inert supports for purification and assay purposes. For example, the collagen binding domain of the receptor protein can be linked to an inert support material for uses in affinity chromatographic methods to isolated lipids and lipid-containing substance such as endotoxin, or to purify inhibitors which may be useful diagnostic, analytic, or therapeutic agents. Other uses include various assay techniques which can be practiced employing the reagents disclosed herein, including radioimmunoassays, enzyme immunoassays, heterogeneous and homogeneous assays, enzyme linked immunoabsorbent assays ("ELISA"), and the like. An exemplary assay for endotoxin-related substances can be carried out as follows. The sample (having an unknown concentration of an endotoxin- related substance) is first contacted with a known quantity of insoluble receptor protein (or analog or a portion thereof containing the epitope and ability to bind an endotoxin-related substance), during which time the endotoxin-related substance in the sample becomes bound to the receptor protein. The mixture is then treated with a known quantity of radiolabeled analyte which binds to those sites on the fixed support which were unoccupied. Excess label is then washed off, and the quantity of label remaining on the support is inversely proportional to the amount of analyte originally present in the sample. The soluble form of the receptor protein can be useful as a therapeutic sequestering agent which would render less toxic and pathogenic endotoxin-related substances which bind to the scavenger receptor. Effective dosages of the therapeutic agents and modes of their administration in the treatment of endotoxemia can be determined by routine experimentation. The pharmaceutical forms suitable for injectable use include sterile aqueous solutions or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions. In all cases the form must be sterile and must be fluid to the extent that easy syringability exists. It must be stable under the conditions of manufacture and storage and may be preserved against the contaminating action of microorganisms, such as bacterial and fungi. The carrier can be a solvent or dispersion medium containing, for example, water, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like), suitable mixtures thereof, and vegetable oils. The proper fluidity can be maintained, for example, by the use of a coating, such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In some cases, it may be preferable to include isotonic agents, for example, sugars or sodium chloride. Prolonged absorption of the injectable therapeutic agents can be brought about by the use in the compositions of agents delaying absorption. Sterile injectable solutions are prepared by incorporating the therapeutic agent in the required amount in the appropriate solvent with various of the other ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the various sterilized active ingredients into a sterile vehicle which contains the basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum-drying and freeze-drying techniques which yield a powder of the active ingredient plus any additional desired ingredient from previously sterile-filtered solution thereof. The therapeutic agent may be administered parenterally or intraperitoneally. Solutions of the therapeutic agent as pharmacologically acceptable salts can be prepared in water suitably mixed with a surfactant, such as hydroxypropylcellulose. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, and mixtures thereof and in oils. Under ordinary conditions of storage and use, these preparations contain a preservative to prevent the growth of microorganisms. The therapeutic agent also may be orally administered, for example, with an inert dilutent or with an assimilable edible carrier, or they may be enclosed in hard or soft shell gelatin capsules, or they may be compressed into tablets, or they may be incorporated directly with the food of the diet. For oral administration, the therapeutic agent may be incorporated with excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspension syrups, wafers, and the like. Such compositions and preparations should contain at least 0.1% of therapeutic agent. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 2 to about 60% of the weight of the unit. The amount of therapeutic agent in such useful compositions is such that a suitable dosage will be obtained. The tablets, troches, pills, capsules and the like may also contain the following: excipients, such as dicalcium phosphate; a disintegrating agent; and a sweetening agent, such as sucrose, lactose or saccharin may be added or a flavoring agent, such as peppermint, oil of wintergreen, or cherry flavoring. When the dosage unit form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier. Various other materials may be present as coatings or to otherwise modify the physical form of the dosage unit. For instance, tablets, pills, or capsules may be coated with shellac, sugar, or both. A syrup or elixir may contain the active compounds sucrose as a sweetening agent, methyl and propylparabens as preservatives, a dye and flavoring, such as cherry or orange flavor. Of course, any material used in preparing any dosage unit form should be pharmaceutically pure and substantially non-toxic in the amounts employed. In addition, the active compounds may be incorporated into sustained-release preparations and formulations. As used herein, "pharmaceutically acceptable carrier" includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents and the like. The use of such media and agents for pharmaceutically active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active ingredient, its use in the therapeutic compositions is contemplated. Supplementary active ingredients can also be incorporated into the compositions. The invention will next be described in connection with certain illustrated embodiments. However, it should be clear that various modifications, additions and subtractions can be made without departing from the spirit or scope of the invention. EXAMPLE 1 Preparation of the Soluble Scavenger Receptor from ative PrpteJ-PS The soluble form of the scavenger receptor protein may be obtained by enzymatic cleavage of isolated native protein as follows. Membrane proteins from 500 g of liver are prepared essentially by the method of Schneider et al. (Vol. 225, i. Biol. Chem.. pp. 11442-11447 (1980)), herein incorporated as reference. The proteins are resuspended in 500 ml of 10 mM Tris-HCl, pH 8, 1 mM CaCl2, 0.15 M NaCl and 1 mM PMSF (Buffer A), sonicated twice, and then dissolved by the addition of 55 ml of 20% Triton X-100 with stirring for 30 min. Insoluble material is removed by centrifugation (33,000 rpm, 1 hr, Beckman Type 35 rotor). The supernatant (500 ml) is applied at 75 ml/hr to an M-BSA-coupled Sepharose 4B column (Pharmacia, 9.8 x 12 cm, containing about 10 mg of M-BSA/ml of gel) which had been equilibrated with Buffer A containing 1% Triton X-100. The column is washed overnight with the same buffer and then washed with two column volumes of Buffer A containing 40 mM octyglucoside. The receptor protein is eluted with Buffer B (1 M NaCl, 20 mM Tris HC1, pH 8, 1 mM CaCl2 1 mM PMSF, and 40 mM octyglucoside). The fractions obtained are tested for their ability to bind Ac-LDL and endotoxinas described below; those containing Ac-LDL and endotoxin-related substances binding activity are pooled and concentrated using ultrafiltration (Diaflo membrane PM30, Amicon) . The sample buffer is changed to 25 mM potassium phosphate, 40 mM octyglucoside, 1 mM PMSF, pH 6.8 using PD10 desalting columns (Pharmacia). The M-BSA affinity purified fraction (50 ml) is then applied to an Ultrogel-Ha (LKB) column (2.5 x 13 cm) at a flow rate of 75 ml/hr, and the proteins eluted with a gradient of phosphate buffer (25 mM to 350 mM) containing 40 mM octyglucoside. The 220 kD scavenger receptor protein is recovered at phosphate concentrations between 100 and 200 mM and is further purified by non-reducing SDS-PAGE on a 3-10% acrylamide gradient gel as described by Laemmli (Vol. 227, Nature pp. 680-685 (1970)), herein incorporated as reference). A 220 kD protein with Ac-LDL binding activity was electroeluted from the gel in 0.1% SDS, 10 mM Tris-HCl, pH 8 using an ISCO 1750 electrophoretic concentrator. The scavenger receptor protein was also purified by a combination of M-BSA affinity chromatography, and IgG-Dl immunoaffinity chromatography, using an antibody to the scavenger receptor protein. All procedures are performed at 4 β C. 100 ml of Buffer C (0.1% SDS, 0.1% sodium deoxycholate, 1% Nonidet P40, 50 mM Tris-HCl, pH 8, 150 mM NaCl, and 1 mM PMSF) are added to M-BSA affinity purified proteins from 500 g of liver or lung (or a smaller amount of THP-1 cells) in 100 ml Buffer B. The sample is applied to Sepharose 4B (Pharmacia) coupled with IgG-Dl (4 mg antibody/ml gel), prepared as described below, at a flow rate of 50 ml/hr, and recycled overnight. The column is washed consecutively with 50 ml of Buffer C, 50 ml of Buffer D (0.2% Triton X-100, 10 mM Tris-HCl, pH 8), 50 ml of Buffer D containing 2 M NaCl, and 20 ml of Buffer E (40 mM octylglucoside containing 10 mM Tris-HCl, pH 8). The bound proteins are then eluted with 20 ml of Buffer E containing 2 M guanidine thiocyanate. After elution, the buffer is changed to Buffer A containing 40 mM octyglucoside using PD10 columns (Pharmacia) . Isolated scavenger receptor protein is then subjected to proteolytic cleavage using serine-, sulfhydryl-, metallo-, or aspartyl proteases to cleave the receptor to remove the membrane spanning domain from the extracellular domain containing the ligand binding site. • Alternatively, a soluble form of the scavenger receptor protein can be generated by cleaving at the sulfhydryl group in the spacer region using cyanogen bromide (see, e.g.. Cross in Meth. EL∑ULi. (Heis, ed.) Academic Press, N.Y. (1967) 2:238). EXAMPLE 2 Preparation of the Soluble Scavenger Receptor Protein bv Recombinant DNA Technology A soluble form of the scavenger receptor protein can also be obtained by using recombinant DNA technology. Methodology for the production of recombinant soluble scavenger receptor, unless otherwise noted, were standard procedures such as those described in Maniatis et al. (Molecular Cloning. A Laboratory Model (1982) Cold Spring Harbor Laboratory), and Davis et. al. (Basic Methods In Molecular Biology (1988) Elsevier Scientific Publishing Co., Inc., NY). The nucleic acid sequence of the scavenger receptor protein is determined as follows. Isolated scavenger receptor protein is further purified using RP-300 (Brownlee Laboratory, Emeryville, CA) reverse phase HPLC. The receptor is solubilized in 70% formic acid. It is then cleaved by cyanogen bromide (CNBr) (25 mg/100 ml solution) at room temperature, overnight, resulting in the formation of a number of cleavage fragments. The fragments are separated chromotographically on the RP-300 column. One of the fragments is isolated and subjected to automated amino acid analysis using an Applied Biosystems Amino Acid Sequencer (Foster City, CA). A second sequence is obtained from a similar CNBr digestion using the gel electrophoresis/ immunoblotting method of Matsudaira ( J. Biol. Chem. (1987) 262:10035-10038). A size fractionated (less than 800 base pairs) cDNA library in lambda ZAPII (Stratogene) is prepared as follows. Poly(Z) + mRNA is isolated by acid guanidium thiocyanate/phenol/chloroform extraction as described by Cho czynski. (Anal. Biochem. (1987) 162:156-159) from bovine lung, and is used to construct a random primed cDNA library. The library is screened with pools of a 3 P end-labelled 41mer oligonucleotide probes that include 5-fluorodeoxyuridine (F) as described by Habener et al. (Proc. Natl. Acad. Sci. (USA) (1988) 85:1735-1739), ANTCAGTAN^ T j TCN j GA^ N^AGGC j A ^ N j TXN j TN j GANG C. For each pool, 5 X 10 5 plaques are screened by hybridization at 37°C and washing at 50°C in 6 x SSC (Maniatis et al. ibid, pp. 447) with 0.1% SDS. Putative positive clones are purified and in vivo excised into picoblue (pBluscript)-derived plasmids (Short, ibid... The inserts are screened by Southern blot hybridization (Southern (1975) J. Mol. Biol. 98:503) using the 17mer oligonucleotide probe ARRTTNGCYT CRTTRTC, and the 26mer oligonucleotide probes TN j CARTAN j N j^ TN 1 TCN 1 GAN 1 AA N j GARGC and ATN 2 CARTAN 1 N 1 TN^GN j GA^ N^ARGC. Five positive clones (including pBSR7 an pBSR3 14 ) were sequenced by the dideoxy-chain termination method, all contained sequences encoding peptides I and II. Additional overlapping clones were isolated from an oligo (dT)-primed bovine lung cDNA library. SEQ. ID NOS: 3 and 4 show the nucleic acid sequence and correspondingly deduced amino acid sequence, respectively, of soluble scavenger receptor derived from bovine clones. The Human sequence can also be derived, for example, by the method of Matsumopo et al. (Proc. Natl. Acad. Sci. (1990) 87:9133-9137). The human nucleic acid sequence and amino acid sequence are shown in SEQ. ID NOS: 1 and 2 , respectively. Vectors for the expression of soluble, secreted scavenger receptor type I (bSRI) and type II (bSRII) are generated as follows. A DNA fragment containing the myelin associated glycoprotein (MAG) leader sequence and a portion of the fibronectin gene is obtained by digesting the vector pMIT (gift from Dr. Richard Hynes, MIT) with BamHl and Xbal. This is ligated with a pCDNAl backbone generated by digestion of pXbSR3 (pCDNAl/Type II) with BamHl/Xbal. The pCDNAl vector is commercially available (Invitrogen) ; however the pCDNAl/Type II (pXbSR3) vector shown in FIG. 2A has additional features (see Rohrer et al. Nature) . The resulting vector is called pCDNAl/MAG (see FIG. 2A) . The pCDNAl/MAG vector is digested with Xhol, Klenow blunted, and digested with Xbal to yield a linear fragment with a 5' blunt end and a 3' sticky Xbal end. This construction is then ligated to a Smal and Xbal digested polymerase chain reaction (PCR) product described below, to form the construct called pCDNAl/common (see FIG. 2B) . The term "common" refers to the fact that the PCR product contains sequence common to both the type I and the type II bovine scavenger receptor cDNAs. A region common to secreted bSRI and bSRII is obtained by utilizing PCR technology as described in PCR Technology; Principles and Applications for DNA Amplification (Henry R. Erlich, ed.) Stockton Press, 1989, and in Freeman et al (Proc. Natl. Acad. Sci. (USA) £2:8810-8814). The oligonucleotides MKSec5* and MKTK8 are used to generate a 620 base pair fragment by PCR using native pCDNAl-bSRI (pXbSR7) as a template. This fragment is digested with Smal (site in the primer MkSec5') and Xbal (site in the common scavenger receptor cDNA sequence), and ligated to the pCDNAl-MAG construct as described above to generate pCDNAl/common. The pCDNAl/common encodes at its 5' end the MAG leader sequence which is attached directly to the cDNA which encodes scavenger receptor amino acids 77-227. The construction results in the conversion of the lysine at position 77 of the receptor to the two amino acids, argenine-glycine. This site is expected to be the N-terminal amino acid after the MAG-receptor primary translation product is cleaved during translocation into the endoplasmic reticulum. The remainder of the secreted bSRI is added by obtaining an Xbal-Xbal fragment from the full length pCDNAl/Type I (pXbSR7, see Kodama et al.. Nature (1990) 343:531-535) encoding the 3' portion of the gene, and ligating it with the Xbal digested pCDNAl/common vector, resulting in the creation of the construction called pCDNAl/bSR-I-sec (see FIG. 2C) . The vector pCDNAl/bSR-II-sec is generated identically using an Xbal-Xbal fragment from pCDNAl/Type II (pxbSR3) as described by Rohrer et al. Nature (1990) Hi:531-535). The region encoding the secreted bSRI including the MAG leader is excised from pCDNAl/bSR-I-sec with Hindlll and ligated with a Hindlll digested pRc/CMV (Invitrogen) backbone as shown in FIG. 2D. Secreted bSRII is transferred to PRc/CMV using an identical strategy. CHO host cells are transfected with the ρRc/CMV/bSR-I-sec vector using the polybrene method described in Maniatis et al. (Molecular Cloning. A laboratory Manual. Cold Spring Harbor Laboratory, 1982, pp. 16-47). Neomycin-resistant cells are selected using G418 (Gibco), a neomycin analog. G418-resistant colonies are picked at random and screened for expression of the protein product using a 30 minute pulse with 400 μCi/ml 35s-methionine followed by lysis and immunoprecipitation with an anti-peptide antibody which was raised against a peptide in the Cys rich domain. Media from a positive colony are examined for the presence of secreted bSR-I as follows. The cells are grown in the presence of 80 μCi/ml 35 S-methionine for 5 hours, at which time the media is harvested. PMSF was added to 1 mM and leupeptin to 0.1 mM. The media is then centrifuged at 1500 x g for 15 minutes to remove cellular debris. The labelled media is diluted 3:1 with buffer A (20 nM Tris, pH 8.0, 150 mM NaCl, 1 mM CaCl2) containing 2 mg/ml bovine serum albumin. To this is added 25 μl AG-PolyG beads (Pharmacia) which had been washed in buffer A. This mixture is vortexed and placed on a rotator at 4°C overnight. The beads are then washed twice with buffer A and protein eluted by the addition of 30 μl sample buffer and boiling. The eluate is run on an 8% Laemmli gel, which was dried and exposed to pre-flashed Kodak XR7 film. A band of 72 kD is seen in transfected cells but not in untransfected CHO cells. EXAMPLE 3 Demonstration of Utility The utility of the soluble scavenger receptor protein is determined by measuring its ability to block scavenger receptor-mediated cellular metabolism of known scavenger receptor ligands (such as radiolabelled endotoxin or 125 I-AcLDL) . That the soluble receptor protein is inhibited by the same ligands as the membrane-bound form is demonstrated by the ability of such ligands to interfere with the binding of radioactively or otherwise labelled soluble forms of the receptor to PolyG beads (Pharmacia) . For example, the inhibitors poly G, poly I, malelyated BSA, and AcLDL are successful competitors at 400 μg/ml, while poly C, LDL, and BSA fail to compete. This demonstrates that the soluble receptor protein has similar binding specificity and and hence utility as the full-length, membrane-bound form. This bead-binding assay can be used to measure the association of endotoxin, lipid IVA, and similar molecules, to soluble forms of the scavenger receptor. The ability of the scavenger receptor to bind lipid IV A is determined by the methods of Raetz et al. (Cold Spring Harbor Sv p. Quant. Biol. (1988) 53:973-982) and Hampton et al. (J. Biol. Chem. (1988) 263:14802-14807). The binding activity of the soluble receptor protein is also measured by filter binding and ligand blotting assays performed with minor modification, according to the methods of Schneider et al. (ibid.) and Daniel et al. (Vol. 258, _L_ Biol. Chem. pp. 4606-4611 (1983)), respectively, herein incorporated as reference. Ligand binding specificity is also determined by polynucleic acid affinity chromatography. M-BSA-purified soluble proteins having endotoxin-related- sustance binding activity in 4 ml of buffer containing 40 mM octyl glucoside, are applied to polynucleic ac d coupled agarose columns (AG-POLY series, prepacked column, Pharmacia). After washing with the same buffer, the bound protein is removed with 5 ml of elution buffer. It is this protein that is useful as a therapeutic agent in the treatment of endotoxemia. It can be seen from the foregoing description and examples that soluble forms of the scavenger receptor protein can be prepared by purification from various appropriate mammalian tissues followed by proteolytic cleavage, or by recombinant DNA methodologies. Because these proteins can bind endotoxin-related substances, they are useful as therapeutic agents in sequestering and promoting the clearance of endotoxins and other endotoxin-related substances found in the circulation of a subject suffering from septic shock. The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. SEQUENCE LISTING (1) GENERAL INFORMATION: (i) APPLICANT: Krieger, Monty (ii) TITLE OF INVENTION: Treatment of Endotoxemia (iii) NUMBER OF SEQUENCES: 4 (iv) CORRESPONDENCE ADDRESS: (A) ADDRESSEE: Kilpatrick & Cody (B) STREET: 100 Peachtree Street (C) CITY: Atlanta (D) STATE: Georgia (E) COUNTRY: US (F) ZIP: 30303 (v) COMPUTER READABLE FORM: (A) MEDIUM TYPE: Floppy disk (B) COMPUTER: IBM PC compatible (C) OPERATING SYSTEM: PC-DOS/MS-DOS (D) SOFTWARE: Patentin Release #1.0, Version #1.25 (vi) CURRENT APPLICATION DATA: (A) APPLICATION NUMBER: US 07/662227 (B) FILING DATE: 22-FEB-1991 (C) CLASSIFICATION: (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 07/555528 (B) FILING DATE: 05-SEP-1990 (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 07/391486 (B) FILING DATE: 09-AUG-1989 (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 07/272002 (B) FILING DATE: 15-NOV-1988 (viϋ) ATTORNEY/AGENT INFORMATION: (A) NAME: Pabst, Patrea L. (B) REGISTRATION NUMBER: 31,284 (C) REFERENCE/DOCKET NUMBER: MIT5358 (ix) TELECOMMUNICATION INFORMATION: (A) TELEPHONE: 404-572-6508 (B) TELEFAX: 404-572-6555 (2) INFORMATION FOR SEQ ID NO:l: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 2037 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: cDNA (iii) HYPOTHETICAL: NO (iv) ANTI-SENSE: NO (v) FRAGMENT TYPE: N-terminal (vi) ORIGINAL SOURCE: (A) ORGANISM: homo sapien (vii) IMMEDIATE SOURCE: (A) LIBRARY: THP-1 (Xi) SEQUENCE DESCRIPTION: SEQ ID NO:l: AGAGAAGTGG ATAAATCAGT GCTGCTTTCT TTAGGACGAA AGAAGTATGG AGCAGTGGGA 60 TCACTTTCAC AATCAACAGG AGGACACTGA TAGCTGCTCC GAATCTGTGA AATTTGATGC 120 TCGCTCAATG ACAGCTTTGC TTCCTCCGAA TCCTAAAAAC AGCCCTTCCC TTCAAGAGAA 180 ACTGAAGTCC TTCAAAGCTG CACTGATTGC CCTTTACCTC CTCGTGTTTG CAGTTCTCAT 240 CCCTCTCATT GGAATAGTGG CAGCTCAACT CCTGAAGTGG GAAACGAAGA ATTGCTCAGT 300 TAGTTCAACT AATGCAAATG ATATAACTCA AAGTCTCACG GGAAAAGGAA ATGACAGCGA 360 AGAGGAAATG AGATTTCAAG AAGTCTTTAT GCAACACATG AGCAACATGG AGAAGAGAAT 420 CCAGCATATT TTAGACATGG AAGCCAACCT CATGGACACA GAGCATTTCC AAAATTTCAG 480 CATGACAACT GATCAAAGAT TTAATGACAT TCTTCTGCAG CTAAGTACCT TGTTTTCCTC 540 AGTCCAGGGA CATGGGAATG CAATAGATGA AATCTCCAAG TCCTTAATAA GTTTGAATAC 600 CACATTGCTT GATTTGCAGC TCAACATAGA AAATCTGAAT GGCAAAATCC AAGAGAATAC 660 CTTCAAACAA CAAGAGGAAA TCAGTAAATT AGAGGAGCGT GTTTACAATG TATCAGCAGA 720 AATTATGGCT ATGAAAGAAG AACAAGTGCA TTTGGAACAG GAAATAAAAG GAGAAGTGAA 780 AGTACTGAAT AACATCACTA ATGATCTGAG ACTGAAAGAT TGGGAACATT CTCAGACCTT 840 GAGAAATATC ACTTTAATTC AAGGTCCTCC TGGACCCCCG GGTGAAAAAG GAGATCGAGG 900 TCCCACTGGA GAAAGTGGTC CACGAGGATT TCCAGGTCCA ATAGGTCCTC CGGGTCTTAA 960 AGGTGATCGG GGAGCAATTG GCTTTCCTGG AAGTCGAGGA CTCCCAGGAT ATGCCGGAAG 1020 GCCAGGAAAT TCTGGACCAA AAGGCCAGAA AGGGGAAAAG GGGAGTGGAA ACACATTAAC 1080 TCCATTTACG AAAGTTCGAC TGGTCGGTGG GAGCGGCCCT CACGAGGGGA GAGTGGAGAT 1140 ACTCCACAGC GGCCAGTGGG GTACAATTTG TGACGATCGC TGGGAAGTGC GCGTTGGACA 1200 GGTCGTCTGT AGGAGCTTGG GATACCCAGG TGTTCAAGCC GTGCACAAGG CAGCTCACTT 1260 TGGACAAGGT ACTGGTCCAA TATGGCTGAA TGAAGTGTTT TGTTTTGGGA GAGAATCATC 1320 TATTGAAGAA TGTAAAATTC GGCAATGGGG GACAAGAGCC TGTTCACATT CTGAAGATGC 1380 TGGAGTCACT TGCACTTTAT AATGCATCAT ATTTTCATTC ACAACTATGA AATCGCTGCT 1440 CAAAAATGAT TTTATTACCT TGTTCCTGTA AAATCCATTT AATCAATATT TAAGAGATTA 1500 AGAATATTGC CCAAATAATA TTTTAGATTA CAGGATTAAT ATATTGAACA CCTTCATGCT 1560 TACTATTTTA TGTCTATATT TAAATCATTT TAACTTCTAT AGGTTTTTAA ATGGAATTTT 1620 CTAATATAAT GACTTATATG CTGAATTGAA CATTTTGAAG TTTATAGCTT CCAGATTACA 1680 AAGGCCAAGG GTAATAGAAA TGCATACCAG TAATTGGCTC CAATTCATAA TATGTTCACC 1740 AGGAGATTAC AATTTTTTGC TCTTCTTGTC TTTGTAATCT ATTTAGTTGA TTTTAATTAC 1800 TTTCTGAATA ACGGAAGGGA TCAGAAGATA TCTTTTGTGC CTAGATTGCA AAATCTCCAA 1860 TCCACACA A TTGTTTTAAA ATAAGAATGT TATCCAACTA TTAAGATATC TCAATGTGCA 1920 ATAACTTGTG TATTAGA AT CAATGTTAAT GATATGTCTT GGCCACTATG GACCAGGGAG 1980 CTTATTTTTC TTGTCATGTA CTGACAACTG TTTAATTGAA TCATGAAGTA AATTGCC 2037 (2) INFORMATION FOR SEQ ID NO:2: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 451 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (iii) HYPOTHETICAL: YES (iv) ANTI-SENSE: NO (v) FRAGMENT TYPE: N-terminal (vi) ORIGINAL SOURCE: (A) ORGANISM: homo sapien (F) TISSUE TYPE: platelets (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2: Met Glu Gin Trp Asp His Phe His Asn Gin Gin Glu Asp Thr Asp Ser 1 5 10 15 Cys Ser Glu Ser Val Lys Phe Asp Ala Arg Ser Met Thr Ala Leu Leu 20 25 30 Pro Pro Asn Pro Lys Asn Ser Pro Ser Leu Asp Glu Lys Leu Lys Ser 35 40 45 Phe Lys Ala Ala Leu He Ala Leu Tyr Leu Leu Val Phe Ala Val Leu He Pro Leu He Gly He Val Ala Ala Gin Leu Leu Lys Trp Glu Thr 65 70 75 80 Lys Asn Cys Ser Val Ser Ser Thr Asn Ala Asn Asp He Thr Gin Ser 85 90 95 Leu Tyr Gly Lys Gly Asn Asp Ser Glu Glu Glu Met Arg Phe Gin Glu 100 105 110 Val Phe Met Glu His Met Ser Asn Met Glu Lys Arg He Gin His He 115 120 125 Leu Asp Met Glu Ala Asn Leu Met Asp Thr Glu His Phe Gin Asn Phe 130 135 140 Ser Met Thr Thr Asp Gin Arg Phe Asn Asp He Leu Leu Gin Leu Ser 145 150 155 160 Thr Leu Phe Ser Ser Val Gin Glu His Glu Asn Ala He Asp Glu He 165 170 175 Ser Lys Ser Leu He Ser Leu Asn Thr Thr Leu Leu Asp Leu Gin Leu 180 185 190 Asn He Glu Asn Leu Asn Gly Lys He Gin Glu Asn Thr Phe Lys Gin 195 200 205 Gin Glu Glu He Ser Lys Leu Glu Glu Arg Val Tyr Asn Val Ser Ala 210 215 220 Glu He Met Ala Met Lys Glu Gly Gin Val His Leu Glu Gin Glu He 225 230 235 240 Lys Gly Glu Val Lys Asp Trp Glu His Ser Gin Thr Leu Arg Asn He Thr Leu He Gin 260 265 270 (2) INFORMATION FOR SEQ ID NO:3: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 1588 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: cDNA (iii) HYPOTHETICAL: NO (iv) ANTI-SENSE: NO (v) FRAGMENT TYPE: N-terminal (vi) ORIGINAL SOURCE: (A) ORGANISM: Bos taurus (F) TISSUE TYPE: lung (Vii) IMMEDIATE SOURCE: (A) LIBRARY: lambda ZAPII (Xi) SEQUENCE DESCRIPTION: SEQ ID NO:3: AGTATGGCAC AGTGGGATGA CTTTCCTGAT CAGCAAGAGG ACACTGACAG CTGTACAGAG 60 TCTGTGAAGT TCGATGCTCG CTCAGTGACA GCTTTGCTTC CTCCCCATCC TAAAAATGGC 120 CCAACTCTTC AAGAGAGGAT GAAGTCTTAT AAAACTGCAC TGATCACCCT TTATCTCATT 180 GTGTTTGTAG TTCTCGTGCC CATCATTGGC ATAGTGGCAG CTCAGCTCCT GAAATGGGAA 240 ACGAAGAATT GCACGGTTGG CTCAGTTAAT GCAGATATAT CTCCAAGTCC GGAAGGCAAA 300 GGAAATGGCA GTGAAGATGA AATGAGATTT CGAGAAGCTG TGATGGAACG CATGAGCAAC 360 ATGGAAAGCA GAATCCAGTA TCTTTCAGAT AATGAAGCCA ATCTCCTAGA TGCTAAGAAT 420 TTCCAAAATT TCAGCATAAC AACTGATCAA AGATTTAATG ATGTTCTTTT CCAGCTAAAT 480 TCCTTACTTT CCTCCATCCA GGAACATGAG AATATCATAG GGGATATCTC CAAGTCATTA 540 GTAGGTCTGA ACACCACAGT ACTTGATTTG CAGTTCAGTA TTGAAACACT GAATGGCAGA 600 GTCCAAGAGA ATGCATTTAA ACAACAAGAG GAGATGCGTA AATTAGAGGA GCGTATATAC 660 AATGCATCAG CAGAAATTAA GTCTCTAGAT GAAAAACAAG TATATTTGGA ACAGGAAATA 720 AAAGGGGAAA TGAAACTGTT GAATAATATC ACTAATGATC TGAGGCTGAA GGATTGGGAA 780 CATTCTCAGA CATTGAAAAA TATCACTTTA CTCCAAGGTC CTCCTGGACC TCCAGGTGAA 840 AAAGGAGATA GAGGCCCTCC TGGACAAAAT GGTATACCAG GCTTTCCAGG TCTAATAGGT 900 ACTCCAGGTC TTAAAGGTGA TCGGGGGATC TCTGGTTTAC CTGGAGTTCG AGGATTCCCA 960 GGACCAATGG GGAAGACCGG GAAGCCAGGA CTTAATGGAC AAAAAGGCCA GAAGGGAGAA 1020 AAACCCACTC CAACCATCCA AACACAATCT AATACAGTCC GACTGGTGGG TGGCAGCGGC 1080 CCTCACGAAG GCAGAGTGGA GATTTTTCAC GAAGGCCAGT GGGGTACGGT GTGTGACGAC 1140 CGCTGGGAAC TGCGTGGAGG ACTGGTCGTC TGCAGGAGCT TGGGATACAA AGGTGTTCAA 1200 AGTGTGCATA AGCGAGCTTA TTTTGGAAAA GGTACGGGTC CAATATGGCT GAATGAAGTA 1260 TTTTGTTTCC CCAAAGAGTC ATCCATTGAA GAGTGCAGAA TTAGACAGTG GGGTGTGAGA 1320 GCCTGTTCGC ACGACGAAGA TGCTGGGGTC ACTTGCACTA CATAATGCAT CATATTTTCA 1380 TTCACATTTT TTAAACTGTT ATAAAGTGAT TTTTTTCCTT TGCTTCACTA AAATCAGCTT 1440 AATTAATATT TAAGAAACTA AGAATTTTAT CCACAGAAAA GGAATATTTA AAAATCACTG 1500 GATAAACATA TAAAATAGCT TCATATTTGC TTCAAATACC AGAACCATTT CAACTTCTGT 1560 AGGTTTTTAA GTGGCTCGTG CCGAATTC 1588 (2) INFORMATION FOR SEQ ID NO:4: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 453 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (iii) HYPOTHETICAL: NO (iv) ANTI-SENSE: NO (v) FRAGMENT TYPE: N-terminal (Vi) ORIGINAL SOURCE: (A) ORGANISM: bos taurus (F) TISSUE TYPE: lung (Vii) IMMEDIATE SOURCE: (A) LIBRARY: lambda ZAPII (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4: Met Ala Gin Trp Asp Asp Phe Pro Asp Gin Gin Glu Asp Thr Asp Ser 1 5 10 15 Cys Thr Glu Ser Val Lys Phe Asp Ala Arg Ser Val Thr Ala Leu Leu 20 25 30 Pro Pro His Pro Lys Asn Gly Pro Thr Leu Gin Glu Arg Met Lys Ser 35 40 45 Tyr Lys Thr Ala Leu He Thr Leu Tyr Leu He Val Phe Val Val Leu 50 55 60 Val Pro He He Gly He Val Ala Ala Gin Leu Leu Lys Trp Glu Thr 65 70 75 80 Lys Asn Cys Thr Val Gly Ser Val Asn Ala Asp He Ser Pro Ser Pro 85 90 95 Glu Gly Lys Gly Asn Gly Ser Glu Asp Glu Met Arg Phe Arg Glu Ala 100 105 110 Val Met Glu Arg Met Ser Asn Met Glu Ser Arg He Gin Tyr Leu Ser 115 120 125 Asp Asn Glu Ala Asn Leu Leu Asp Ala Lys Asn Phe Gin Asn Phe Ser 130 135 140 He Thr Thr Asp Gin Arg Phe Asn Asp Val Thr Phe Gin Thr Asn Ser 145 150 155 160 Leu Leu Ser Ser He Gin Glu His Glu Asn He He Gly Asp He Ser 165 170 175 Lys Ser Leu Val Gly Leu Asn Thr Thr Val Leu Asp Leu Gin Phe Ser 180 185 190 He Glu Thr Leu Asn Gly Arg Val Gin Glu Asn Ala Phe Lys Gin Gin 195 200 205 Glu Glu Met Arg Lys Leu Glu Glu Arg He Tyr Asn Asn Ser Asn Glu 210 215 220 He Lys Ser Leu Asp Glu Lys Gin Val Tyr Leu Glu Gin Glu He Lys 225 230 235 240 Gly Glu Met Lys Leu Leu Asn Asn He Thr Asn Asp Leu Arg Leu Lys 245 250 255 Asp Trp Glu His Ser Gin Thr Leu Lys Asn He Thr Leu Leu Gin Gly 260 265 270 Pro Pro Gly Pro Pro Gly Glu Lys Gly Asp Arg Gly Pro Pro Gly Gin 275 280 285 Asn Gly He Pro Gly Phe Pro Gly Leu He Gly Thr Pro Gly Leu Lys 290 295 300 Gly Asp Arg Gly He Ser Gly Leu Pro Gly Val Arg Gly Phe Pro Gly 305 310 315 320 Pro Met Gly Lys Thr Gly Lys Pro Gly Leu Asn Gly Gin Lys Gly Gin 325 330 335 Lys Gly Glu Lys Gly Ser Gly Ser Met Gin Arg Gin Ser Asn Thr Val 340 345 350 Arg Leu Val Gly Gly Ser Gly Pro His Glu Gly Arg Val Glu He Phe 355 360 365 His Glu Gly Gin Trp Gly Thr Val Cys Asp Asp Arg Trp Glu Leu Arg 370 375 380 Gly Gly Leu Val Val Cys Arg Ser Leu Gly Tyr Lys Gly Val Gin Ser 385 390 395 400 Val His Lys Arg Ala Tyr Phe Gly Lys Gly Thr Gly Pro He Trp Leu 405 410 415 Asn Glu Val Phe Cys Phe Gly Lys Glu Ser Ser He Glu Glu Cys Arg

Claims: I claim: 1. A method for treating endotoxemia comprising: providing a therapeutic agent that is a non-immunoglobulin polypeptide soluble in the circulation and has the ability to bind endotoxin; and administering to the circulation of a subject an endotoxemia-inhibiting, effective amount of said agent in a pharmaceutically acceptible carrier, said agent binding endotoxin-related substances in the circulation, thereby forming a conjugate with reduced toxicity and pathogenicity. 2. The method of claim 1 wherein said providing step comprises providing a therapeutic agent including a fragment of the scavenger receptor protein, said fragment including an extracellular portion of the scavenger receptor protein. 3. The method of claim 2 wherein said providing step comprises providing the collagen binding domain. 4. The method of claim 3 wherein said providing step further comprises providing a fragment of the scavenger receptor protein further including the spacer domain. 5. The method of claim 2 wherein said providing step comprises providing the α-helical coiled coil domain. 6. The method of claim 2 wherein said providing step comprises providing the cysteine-rich domain. 7. The method of claim 2 wherein said providing step comprises cleaving said fragment by biochemical means from substantially purified native scavenger receptor protein. 8. The method of claim 2 wherein said providing step comprises providing an analog of the scavenger receptor protein produced by recombinant DNA technology. 9. The method of claim 1 wherein said providing step comprises providing a therapeutic agent further characterized by having an affinity for acetylated low density lipoprotein of about 0.5 to 5.0 microgram(s) protein per milliliter. 10. The method of claim 1 wherein said providing step comprises providing a therapeutic agent further characterized by having the ability to bind chemically-modified low density lipoprotein. 11. The method of claim 1 wherein said providing step comprises providing a therapeutic agent further characterized by the ability to bind a negatively- charged macromolecule selected from the group consisting of polyvinylsulfate, maleyl-BSA, fucoidan, and purine polynucleotides, poly[I-C], poly[I] and poly[G] . 12. The method of claim 1 wherein said providing step comprises providing a therapeutic agent that binds the Lipid A portion of endotoxin. 13. The method of claim 1 wherein said providing step comprises providing a therapeutic agent that binds gram-negative bacteria. 14. A pharmaceutical composition for treating endotoxemia, comprising: a non-immunoglobulin polypeptide therapeutic agent soluble in the circulation, and having the ability to bind endotoxin-related substances to form a conjugate with reduced toxicity and reduced pathogenicity; and a pharmaceutically acceptible carrier. 15. The pharmaceutical composition of claim 14 wherein said agent comprises a fragment of the scavenger receptor protein, said fragment including an extracellular portion of the scavenger receptor protein. 16. The pharmaceutical composition of claim 15 wherein said extracellular portion of the scavenger receptor protein comprises the collagen-binding domain. 17. The pharmaceutical composition of claim 16 wherein said extracellular portion of the scavenger receptor protein further comprises the spacer domain. 18. The pharmaceutical composition of claim 15 wherein said extracellular portion of the scavenger receptor protein comprises the α-helical coiled coil domain. 19. The pharmaceutical composition of claim 15 wherein said extracellular portion of the scavenger receptor protein comprises the cysteine-rich domain. 20. The pharmaceutical composition of claim 14 wherein said agent comprises an active analog of the scavenger receptor protein produced by recombinant DNA technology. 21. The pharmaceutical composition of claim 14 further characterized by having an affinity for acetylated low density lipoprotein of about 0.5 to 5.0 microgram(s) protein per milliliter. 22. The pharmaceutical composition of claim 14 further characterized by the ability to bind a negatively-charged macromolecule selected from the group consisting of polyvinylsulfate, maleyl-BSA, fucoidan, and purine polynucleotides, ρoly[I-C], poly[I] and poly[G] . 23. The pharmaceutical composition of claim 14 further characterized by the ability to bind chemically-modified low density lipoprotein. 24. The pharmaceutical composition of claim 13 further characterized by binding the Lipid A moiety of endotoxin. 25. The pharmaceutical composition of claim 13 further characterized by binding gram-negative bacteria. [received by the International Bureau on 3 August 1992 (03.08.92); original claims 2 and 15 cancelled; claims 3-14 and 16-25 renumbered as claims 2-13 and 14-23 other claims unchanged (3 pages)] 1. A method for treating endotoxemia comprising: administering to a patient in need of therapy an effective amount to bind endotoxin of a polypeptide fragment of the extracellular portion of a substantially pure macrophage scavenger receptor protein, formed from three subunits each having an apparent molecular weight on SDS- polyacrylamide gels of about 77,000 daltons, the receptor protein when glycosylated having an apparent molecular weight on SDS-polyacrylamide gels of about 220,000 daltons, and a binding capacity for acetylated low density lipoprotein of at least 1.4 mg of Acetyl-LDL protein/mg receptor protein. 2. The method of claim 1 wherein said fragment comprises the collagen binding domain. 3. The method of claim 2 wherein said fragment of the scavenger receptor protein further includes the spacer domain. 4. The method of claim 1 wherein said fragment comprises the α-helical coiled coil domain. 5. The method of claim 1 wherein said fragment comprises the cysteine-rich domain. 6. The method of claim 1 further comprising cleaving said fragment by biochemical means from substantially purified native scavenger receptor protein. 7. The method of claim 1 further comprising expressing the fragment from an isolated DNA fragment encoding the scavenger receptor protein in an appropriate host expression system. 8. The method of claim 1 wherein said fragment has an affinity for acetylated low density lipoprotein of about 0.5 to 5.0 microgram(s) protein per milliliter. 9. The method of claim 1 wherein said fragment can bind chemically-modified low density lipoprotein. 10. The method of claim 1 wherein said fragment can bind a negatively-charged macromolecule selected from the group consisting of polyvinylsulfate, maleyl-BSA, fucoidan, and purine polynucleotides, poly[I-C], polyfl] and poly[G] . 11. The method of claim 1 wherein said fragment binds the Lipid A portion of endotoxin. 12. The method of claim 1 wherein said fragment binds gram- negative bacteria. 13. A pharmaceutical composition for treating endotoxemia, comprising: a polypeptide fragment of the extracellular portion of a substantially pure macrophage scavenger receptor protein, formed from three subunits each having an apparent molecular weight on SDS-polyacrylamide gels of about 77,000 daltons, the receptor protein when glycosylated having an apparent molecular weight on SDS- polyacrylamide gels of about 220,000 daltons, and a binding capacity for acetylated low density lipoprotein of at least 1.4 mg of Acetyl-LDL protein/mg receptor protein; and a pharmaceutically acceptable carrier. 14. The pharmaceutical composition of claim 13 wherein said fragment comprises the collagen-binding domain. 15. The pharmaceutical composition of claim 14 wherein said fragment further comprises the spacer domain. 16. The pharmaceutical composition of claim 13 wherein said fragment comprises the α-helical coiled coil domain. 17. The pharmaceutical composition of claim 13 wherein said fragment comprises the cysteine-rich domain. 18. The pharmaceutical composition of claim 13 wherein said fragment is expressed from a DNA fragment encoding a protein consisting essentially of the scavenger receptor protein in an appropriate expression system. 19. The pharmaceutical composition of claim 13 further characterized by having an affinity for acetylated low density lipoprotein of about 0.5 to 5.0 microgram(s) protein per milliliter. 20. The pharmaceutical composition of claim 13 further characterized by the ability to bind a negatively-charged macromolecule selected from the group consisting of polyvinylsulfate, maleyl-BSA, fucoidan, and purine polynucleotides, poly[I-C], poly[I] and poly[G] . 21. The pharmaceutical composition of claim 13 further characterized by the ability to bind chemically-modified low density lipoprotein. 22. The pharmaceutical composition of claim 13 further characterized by binding the Lipid A moiety of endotoxin. 23. The pharmaceutical composition of claim 13 further characterized by binding gram-negative bacteria.

Inventors: KRIEGER MONTY, KRIEGER, MONTY
Applicants: MASSACHUSETTS INST TECHNOLOGY, MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Application year: 1992
Main classification: A61K37
IPC codes: A61K38, C07K14