POLYALKYLENE OXIDE-MODIFIED SINGLE CHAIN POLYPEPTIDES

Abstract: The present invention relates to the chemical modification of single chain polypeptides by means of covalent attachment of strands of poly(ethylene glycol) PEG and similar poly(alkylene oxides) to single chain polypeptide binding molecules that have the three dimensional folding and, thus, the binding ability and specificity, of the variable region of an antibody. Such preparations of modified single chain polypeptide binding molecules have reduced immugenicity and antigenicity as well as having a longer halflife in the bloodstream as compared to the parent polypeptide. These beneficial properties of the modified single chain polypeptide binding molecules make them very useful in a variety of therapeutic applications. The invention also relates to multivalent antigen-binding molecules capable of PEGylation. Compositions of, genetic constructions for, methods of use, and methods for producing PEGylated antigen-binding proteins are disclosed.

Description: Polyalkylene Oxide-Modified Single Chain Polypeptides Background of the Invention 1. Field of the Invention The present invention relates to the chemical modification of single chain polypeptides by means of covalent attachment of strands of poly(ethylene glycol) PEG and similar poly(alkylene oxides) to single chain polypeptide binding molecules that have the three dimensional folding and, thus, the binding ability and specificity, of the variable region of an antibody. Such preparations of modified single chain polypeptide binding molecules have reduced immugenicity and antigenicity as well as having a longer halflife in the bloodstream as compared to the parent polypeptide. These beneficial properties of the modified single chain polypeptide binding molecules make them very useful in a variety of therapeutic applications. The invention also relates to multivalent antigen-binding molecules capable of PEGylation. Compositions of, genetic constructions for, methods of use, and methods for producing PEGylated antigen-binding proteins are disclosed. 2. Description of Related Art Antibodies are proteins generated by the immune system to provide a specific molecule capable of complexing with an invading molecule, termed an antigen. Natural antibodies have two identical antigen-binding sites, both of which are specific to a particular antigen. The antibody molecule "recognizes" the antigen by complexing its antigen-binding sites with areas of the antigen termed epitopes. The epitopes fit into the conformational architecture of the antigen- binding sites of the antibody, enabling the antibody to bind to the antigen. The antibody molecule is composed of two identical heavy and two identical light polypeptide chains, held together by interchain disulfide bonds. The remainder of this discussion on antibodies will refer only to one pair of light/heavy chains, as each light/heavy pair is identical. Each individual light and heavy chain folds into regions of approximately 110 amino acids, assuming a conserved three- dimensional conformation. The light chain comprises one variable region (V L ) and one constant region (C L ), while the heavy chain comprises one variable region (V H ) and three constant regions (C H 1, C H 2 and C H 3). Pairs of regions associate to form discrete structures. In particular, the light and heavy chain variable regions associate to form an "Fv" area which contains the antigen-binding site. The constant regions are not necessary for antigen binding and in some cases can be separated from the antibody molecule by proteolysis, yielding biologically active (i.e., binding) variable regions composed of half of a light chain and one quarter of a heavy chain. Further, all antibodies of a certain class and their F ab fragments (i.e., fragments composed of V L , C L , V H , and C H 1) whose structures have been determined by x-ray crystallography show similar variable region structures despite large differences in the sequence of hypervariable segments even when from different animal species. The immunoglobulin variable region seems to be tolerant towards mutations in the antigen-binding loops. Therefore, other than in the hypervariable regions, most of the so-called "variable" regions of antibodies, which are defined by both heavy and light chains, are, in fact, quite constant in their three dimensional arrangement. See for example, Huber, R., Science 233:702-703 (1986)). Recent advances in immunobiology, recombinant DNA technology, and computer science have allowed the creation of single polypeptide chain molecules that bind antigen. These single-chain antigen-binding molecules ("SCA") or single-chain variable fragments of antibodies ("sFv") incorporate a linker polypeptide to bridge the individual variable regions, V L and V H , into a single polypeptide chain. A description of the theory and production of single-chain antigen-binding proteins is found in Ladner et al., U.S. Patent Nos. 4,946,778, 5,260,203, 5,455,030 and 5,518,889. The single-chain antigen-binding proteins produced under the process recited in the above U.S. patents have binding specificity and affinity substantially similar to that of the corresponding Fab fragment. A computer-assisted method for linker design is described more particularly in Ladner etal., U.S. Patent Nos. 4,704,692 and 4,881,175, and WO 94/12520. The in vivo properties of sFv (SCA) polypeptides are different from MAbs and antibody fragments. Due to their small size, sFv (SCA) polypeptides clear more rapidly from the blood and penetrate more rapidly into tissues (Milenic, D.E. et al. , Cancer Research 51.6363-6371 (1991 ); Colcher et al, J. Natl. Cancer Inst. 82:1191 (1990); Yokota et al., Cancer Research 52:3402 (1992)). Due to lack of constant regions, sFv (SCA) polypeptides are not retained in tissues such as the liver and kidneys. Due to the rapid clearance and lack of constant regions, sFv (SCA) polypeptides will have low immunogenicity. Thus, sFv (SCA) polypeptides have applications in cancer diagnosis and therapy, where rapid tissue penetration and clearance, and ease of microbial production are advantageous. A multivalent antigen-binding protein has more than one antigen-binding site. A multivalent antigen-binding protein comprises two or more single-chain protein molecules. Enhanced binding activity, di- and multi-specific binding, and other novel uses of multivalent antigen-binding proteins have been demonstrated. See, Whitlow, M., et al., Protein Engng. 7:1017-1026 (1994); Hoogenboom, H.R., Nature Biotech. 75:125-126 (1997); and WO 93/11161. Ladner et al. also discloses the use of the single chain antigen binding molecules in diagnostics, therapeutics, in vivo and in vitro imaging, purifications, and biosensors. The use of the single chain antigen binding molecules in immobilized form, or in detectably labeled forms is also disclosed, as well as conjugates of the single chain antigen binding molecules with therapeutic agents, such as drugs or specific toxins, for delivery to a specific site in an animal, such as a human patient. Whitlow et al. {Methods: A Companion to Methods in Enzymology 2(2):97- 105 (June, 1991 )) provide a good review of the art of single chain antigen binding molecules and describe a process for making them. In U.S. Patent 5,091,513, Huston et al. discloses a family of synthetic proteins having affinity for preselected antigens. The contents of U.S.Patent 5,091,513 are incorporated by reference herein. The proteins are characterized by one or more sequences of amino acids constituting a region that behaves as a biosynthetic antibody binding site (BABS). The sites comprise (1) noncovalently associated or disulfide bonded synthetic V H and V L regions, (2) V H -V L or V L -V H single chains wherein the V H and V L are attached to a polypeptide linker, or (3) individual V H or V L domains. The binding domains comprises complementarity determining regions (CDRs) linked to framework regions (FRs), which may be derived from separate immunoglobulins. U.S. Patent 5,091,513 also discloses that three subregions (the CDRs) of the variable domain of each of the heavy and light chains of native immunoglobulin molecules collectively are responsible for antigen recognition and binding. These CDRs consist of one of the hypervariable regions or loops and of selected amino acids or amino acid sequences disposed in the framework regions that flank that particular hypervariable region. It is said that framework regions from diverse species are effective in maintaining CDRs from diverse other species in proper conformation so as to achieve true immunochemical binding properties in a biosynthetic protein. U.S. Patent 5,091 ,513 includes a description of a chimeric polypeptide that is a single chain composite polypeptide comprising a complete antibody binding site. This single chain composite polypeptide is described as having a structure patterned after tandem V H and V L domains, with a carboxyl terminal of one attached through an amino acid sequence to the amino terminal of the other. It thus comprises an amino acid sequence that is homologous to a portion of the variable region of an immunoglobulin heavy chain (V H ) peptide bonded to a second amino acid sequence that was homologous to a portion of the variable region of an immunoglobulin light chain (V L ). The covalent attachment of strands of a polyalkylene glycol to a polypeptide molecule is disclosed in U.S. Patent No.4, 179,337 to Davis et al. , as well as in Abuchowski and Davis "Enzymes as Drugs," Holcenberg and Roberts, Eds., pp. 367-383, John Wiley and Sons, New York (1981). These references disclosed that proteins and enzymes modified with polyethylene glycols have reduced immunogenicity and antigenicity and have longer lifetimes in the bloodstream, compared to the parent compounds. The resultant beneficial properties of the chemically modified conjugates are very useful in a variety of therapeutic applications. Although amino acid sequences such as the single chain polypeptides described above, and fusion proteins thereof, have not been associated with significant antigenicity in mammals, it has been desirable to prolong the circulating life and even further reduce the possibility of an antigenic response. The relatively small size of the polypeptides and their delicate structure/activity relationship, however, have made polyethylene glycol modification difficult and unpredictable. Most importantly, it was unknown how to modulate retained activity of the polypeptides after conjugation with polymers, such as PEG. To effect covalent attachment of polyethylene glycol (PEG) or polyalkalene oxides to a protein, the hydroxyl end groups of the polymer must first be converted into reactive functional groups. This process is frequently referred to as "activation" and the product is called "activated PEG" or activated polyalkylene oxide. Methoxy poly(ethylene glycol) (mPEG), capped on one end with a functional group, reactive towards amines on a protein molecule, is used in most cases. The activated polymers are reacted with a therapeutic agent having nucleophilic functional groups that serve as attachment sites. One nucleophilic functional group commonly used as an attachment site is the e-amino groups of lysines. Free carboxylic acid groups, suitably activated carbonyl groups, oxidized carbohydrate moieties and mercapto groups have also been used as attachment sites. The hydroxyl group of PEG has been activated with cyanuric chloride and the resulting compound is then coupled with proteins (Abuchowski et al, J. Biol. Chem. 252:3578 (1977); Abuchowski & Davis, supra (1981)). However, there are disadvantages in using this method, such as the toxicity of cyanuric chloride and its non-specific reactivity for proteins having functional groups other than amines, such as free essential cysteine or tyrosine residues. In order to overcome these and other disadvantages, alternative activated PEGs, such as succinimidyl succinate derivatives of PEG ("SS-PEG"), have been introduced (Abuchowski et al, Cancer Biochem. Biophys. 7:175-186 (1984)). SS-PEG reacts quickly with proteins (30 minutes) under mild conditions yielding active yet extensively modified conjugates. Zalipsky, in U.S. PatentNo.5,122,614, discloses poly(ethylene glycol)-N- succinimide carbonate and its preparation. This form of the polymer is said to react readily with the amino groups of proteins, as well as low molecular weight peptides and other materials that contain free amino groups. Other linkages between the amino groups of the protein, and the PEG are also known in the art, such as urethane linkages (Veronese et al, Appl. Biochem. Biotechnol 77:141-152 (1985)), carbamate linkages (Beauchamp et al, Analyt. Biochem. 131:25-33 (1983)), and others. Suzuki et al. (Biochimica et Biophysica Acta, 788: 248-255 (1984)) covalently couples immunoglobulin G (IgG) to poly(ethylene glycol) that has previously been activated by cyanuric chloride. The coupled IgG was studied for physicochemical and biological properties such as molecular structure, size- exclusion chromatographic behavior, surface activity, interfacial aggregability, heat aggregability inducing nonspecific complement activation, and antigen- binding activity. The poly(ethylene glycol) coupling to IgG increased the apparent Stokes' radius and the surface activity of IgG and stabilized IgG on heating and/or on exposure to interfaces, while no structural denaturation of IgG was observed. The suppressed nonspecific aggregability was interpreted mainly by difficulty in association between the modified IgG molecules. These results indicated the use of the poly(ethylene glycol)-coupled IgG as an intravenous preparation and also as an additive stabilizing intact IgG for intravenous use. Sharp et al {Analytical Biochemistry 154: 110-117 (1986)) investigated the possibility of producing biospecific affinity ligands for separating cells in two polymer aqueous phase systems on the basis of cell surface antigens. Rabbit anti- human erythrocyte IgG was reacted with cyanuric chloride-activated monomethyl poly(ethylene glycol) fractions (molecular weights approximately 200, 1900, and 5000) at various molar ratios of PEG to protein lysine groups. The partition coefficient of the protein in a Dextran/PEG two phase system increased with increasing degree of modification and increasing PEG molecular weight. There was a concomitant loss in ability to agglutinate human erythrocytes. Tullis, in U.S. PatentNo.4,904,582, describes oligonucleotide conjugates wherein the oligonucleotides are joined through a linking arm to a hydrophobic moiety, which could be a polyalkyleneoxy group. The resulting conjugates are said to be more efficient in membrane transport, so as to be capable of crossing the membrane and effectively modulating a transcriptional system. In this way, the compositions can be used in vitro and in vivo, for studying cellular processes, protecting mammalian hosts from pathogens, and the like. Excessive polymer conjugation and/or conjugation involving a therapeutic moietie's active site where groups associated with bioactivity are found, however, often result in loss of activity and, thus, therapeutic usefulness. This is often the case with lower molecular weight peptides which have few attachment sites not associated with bioactivity. For example, Benhar et al {Bioconjugate Chem. 5:321-326 (1994)) observed that PEGylation of a recombinant single-chain immunotoxin resulted in the loss of specific target immunoreactivity of the immunotoxin. The loss of activity of the immunotoxin was the result of PEG conjugation at two lysine residues within the antibody-combining region of the immunotoxin. To overcome this problem, Benhar et al. replaced these two lysine residues with arginine residues and were able to obtain an active immunotoxin that was 3-fold more resistant to inactivation by derivatization. Another suggestion for overcoming these problems discussed above is to use longer, higher molecular weight polymers. These materials, however, are difficult to prepare and expensive to use. Further, they provide little improvement over more readily available polymers. Another alternative suggested is to attach two strands of polymer via a triazine ring to amino groups of a protein. See, for example, Enzyme 26:49-53 (1981) and Proc. Soc. Exper. Biol. Med, 188:364-369 (1988). However, triazine is a toxic substance that is difficult to reduce to acceptable levels after conjugation. Thus, non-triazine-based activated polymers would offer substantial benefits to the art. Summary of the Invention The present invention relates to polyalkylene oxide/amino acid sequence conjugates and processes for preparing them. Suitable amino acid sequences are peptides, such as, single chain polypeptides having binding affinity for an antigen, for example, those described by Ladner et al in U.S. Patent No. 4,946,778 and Huston et al. in U.S. Patent No. 5,091,513. More particularly, the present invention relates to a physiologically active, substantially non-immunogenic polypeptide conjugate containing at least one polyalkylene oxide strand coupled to a single chain polypeptide having binding affinity for an antigen. The single chain polypeptide includes: (a) a first polypeptide comprising the binding portion of the light chain variable region of an antibody; (b) a second polypeptide comprising the binding portion of the heavy chain variable region of an antibody; and (c) at least one peptide linker linking said first and second polypeptides (a) and (b) into said single chain polypeptide having binding affinity for the antigen. In another aspect, the present invention relates to a process for preparing physiologically active, substantially non-immunogenic polypeptide compositions. The process includes coupling a polyalkylene oxide to a single chain polypeptide having the attributes described above. Preferably, the poly(alkylene oxides) used herein are poly(ethylene glycols) that have been activated for coupling to the target polypeptide. The invention is also directed to a single-chain antigen-binding polypeptide -polyalkylene oxide conjugate, comprising: (a) a first polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide-polyalkylene oxide conjugate has an antigen binding affinity within a range of about one-fold to about ten-fold of the antigen binding affinity of the native, unconjugated form of the single-chain antigen-binding polypeptide. The invention is also directed to a single-chain antigen-binding polypeptide -polyalkylene oxide conjugate, comprising: (a) a first polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide-polyalkylene oxide conjugate has an antigen binding affinity within about ten-fold of the antigen binding affinity of the native, unconjugated form of the single-chain antigen-binding polypeptide. The invention is also directed to a single-chain antigen-binding polypeptide -polyalkylene oxide conjugate, comprising: (a) a first polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide-polyalkylene oxide conjugate has an antigen binding affinity within about five-fold of the antigen binding affinity of the native, unconjugated form of the single-chain antigen-binding polypeptide. The invention is also directed to a single-chain antigen-binding polypeptide -polyalkylene oxide conjugate, comprising: (a) a first polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide-polyalkylene oxide conjugate has an antigen binding affinity within about two-fold of the antigen binding affinity of the native, unconjugated form of the single-chain antigen-binding polypeptide. The invention is also directed to a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least one Cys residue wherein the Cys residue is capable of polyalkylene oxide conjugation and the Cys residue is located at a position selected from the group consisting of (i) the amino acid position 11 , 12, 13, 14 or 15 ofthe light chain variable region; (ii) the amino acid position 77, 78 or 79 ofthe light chain variable region; (iii) the amino acid position 11, 12, 13, 14 or 15 ofthe heavy chain variable region; (iv) the amino acid position 82B, 82C or 83 ofthe heavy chain variable region; (v) any amino acid position ofthe peptide linker; (vi) adjacent to the C-terminus of polypeptide (a) or (b); and (vii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. The invention is also directed to a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least three consecutive Lys residues wherein the consecutive Lys residues are capable of polyalkylene oxide conjugation and any one of the consecutive Lys residues is located at a position selected from the group consisting of (i) any amino acid position ofthe peptide linker; (ii) adjacent to the C-terminus of polypeptide (a) or (b); and (iii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. These consecutive lysine residues in the sFv (SCA) protein (i.e., oligo-lysine sFv) generate a "hot spot" for polyalkylene oxide conjugation. The invention is also directed to a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least two consecutive Cys residue wherein the consecutive Cys residues are capable of polyalkylene oxide conjugation and any one of the consecutive Cys residues is located at a position selected from the group consisting of (i) any amino acid position ofthe peptide linker; (ii) adjacent to the C-terminus of polypeptide (a) or (b); and (iii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. These consecutive cysteine residues in the sFv (SCA) protein (i.e., oligo-cysteine sFv) generate a "hot spot" for polyalkylene oxide conjugation. The invention is further directed to a genetic sequence encoding a single- chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least one Cys residue wherein the Cys residue is capable of polyalkylene oxide conjugation and the Cys residue is located at a position selected from the group consisting of (i) the amino acid position 11, 12, 13, 14 or 15 ofthe light chain variable region; (ii) the amino acid position 77, 78 or 79 ofthe light chain variable region; (iii) the amino acid position 11, 12, 13, 14 or 15 of the heavy chain variable region; (iv) the amino acid position 82B, 82C or 83 ofthe heavy chain variable region; (v) any amino acid position ofthe peptide linker; (vi) adjacent to the C-terminus of polypeptide (a) or (b); and (vii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. The invention is further directed to a genetic sequence encoding a single- chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least three consecutive Lys residue wherein the consecutive Lys residues are capable of polyalkylene oxide conjugation and any one of the consecutive Lys residues is located at a position selected from the group consisting of (i) any amino acid position ofthe peptide linker; (ii) adjacent to the C-terminus of polypeptide (a) or (b); and (iii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. These consecutive lysine residues in the sFv (SCA) protein (i.e., oligo-lysine sFv) generate a "hot spot" for polyalkylene oxide conjugation. The invention is further directed to a genetic sequence encoding a single- chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least two consecutive Cys residue wherein the consecutive Cys residues are capable of polyalkylene oxide conjugation and any one of the consecutive Cys residues is located at a position selected from the group consisting of (i) any amino acid position ofthe peptide linker; (ii) adjacent to the C-terminus of polypeptide (a) or (b); and (iii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. These consecutive cysteine residues in the sFv (SCA) protein (i.e., oligo-cysteine sFv) generate a "hot spot" for polyalkylene oxide conjugation. The genetic sequence may be DNA or RNA. The invention is directed to a replicable cloning or expression vehicle comprising the above described DNA sequence. The invention is also directed to such vehicle which is a plasmid. The invention is further directed to a host cell transformed with the above described DNA. The host cell may be a bacterial cell, a yeast cell or other fungal cell, an insect cell or a mammalian cell line. A preferred host is Pichia pastoris. The invention is directed to a method of producing a single-chain antigen- binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) providing a first genetic sequence encoding a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) providing a second genetic sequence encoding a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) linking the first and second genetic sequences (a) and (b) with a third genetic sequence encoding a peptide linker into a fourth genetic sequence encoding a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least one Cys residue wherein the Cys residue is capable of polyalkylene oxide conjugation and the Cys residue is located at a position selected from the group consisting of (i) the amino acid position 11, 12, 13, 14 or 15 ofthe light chain variable region; (ii) the amino acid position 77, 78 or 79 ofthe light chain variable region; (iii) the amino acid position 11, 12, 13, 14 or 15 of the heavy chain variable region; (iv) the amino acid position 82B, 82C or 83 ofthe heavy chain variable region; (v) any amino acid position ofthe peptide linker; (vi) adjacent to the C-terminus of polypeptide (a) or (b); and (vii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen; (d) transforming a host cell with the fourth genetic sequence encoding a single-chain antigen-binding polypeptide of (c); and (e) expressing the single-chain antigen-binding polypeptide of (c) in the host, thereby producing a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation. The invention is further directed to a multivalent single-chain antigen- binding protein, comprising two or more single-chain antigen-binding polypeptides, each single-chain antigen-binding polypeptide comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least one Cys residue wherein the Cys residue is capable of polyalkylene oxide conjugation and the Cys residue is located at a position selected from the group consisting of (i) the amino acid position 11, 12, 13, 14 or 15 ofthe light chain variable region; (ii) the amino acid position 77, 78 or 79 ofthe light chain variable region; (iii) the amino acid position 11, 12, 13, 14 or 15 of the heavy chain variable region; (iv) the amino acid position 82B, 82C or 83 ofthe heavy chain variable region; (v) any amino acid position ofthe peptide linker; (vi) adjacent to the C-terminus of polypeptide (a) or (b); and (vii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. In the above described embodiments ofthe invention, the Cys polyalkylene oxide conjugation sequence may be capable of attaching a polyalkylene oxide moiety and the Cys residue is located at a position selected from the group consisting of (i ? ) the amino acid position 77 ofthe light chain variable region; (ii') the amino acid position 82B ofthe heavy chain variable region; (iii') the amino acid position 3 ofthe peptide linker; (iv') adjacent to the C-terminus of polypeptide (a) or (b); (v') N-terminus and C-terminus; and (vi') combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. In the above described embodiments of the invention, the oligo-Lys polyalkylene oxide conjugation sequence may be capable of attaching a polyalkylene oxide moiety at the oligo-Lys residues located adjacent to the C- terminus ofthe protein, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. In the above described embodiments ofthe invention, the C-terminus of the second polypeptide (b) may be the native C-terminus. The C-terminus ofthe second polypeptide (b) may comprise a deletion of one or plurality of amino acid residue(s), such that the remaining N-terminus amino acid residues ofthe second polypeptide are sufficient for the polyalkylene oxide conjugated polypeptide to be capable of binding an antigen. The C-terminus ofthe second polypeptide may comprise an addition of one or plurality of amino acid residue(s), such that the polyalkylene oxide conjugated polypeptide is capable of binding an antigen. In a preferred embodiment ofthe invention, the first polypeptide (a) may comprise the antigen binding portion ofthe variable region of an antibody light chain and the second polypeptide (b) comprises the antigen binding portion ofthe variable region of an antibody heavy chain. The invention is also directed to a method of detecting an antigen suspected of being in a sample, comprising: (a) contacting the sample with the polyalkylene oxide conjugated polypeptide or protein ofthe invention, wherein the polyalkylene oxide conjugated polypeptide is conjugated to one or plurality of detectable label molecule(s), or conjugated to a carrier having one or plurality of detectable label molecule(s) bound to the carrier; and (b) detecting whether the polyalkylene oxide conj ugated single-chain antigen-binding polypeptide has bound to the antigen. The invention is further directed to a method of imaging the internal structure of an animal, comprising administering to the animal an effective amount of the polyalkylene oxide conjugated polypeptide or protein of the invention, wherein the polyalkylene oxide conjugated polypeptide is conjugated to one or plurality of detectable label or chelator molecule(s), or conjugated to a carrier having one or plurality of detectable label or chelator molecule(s) bound to the carrier, and measuring detectable radiation associated with the animal. Animal includes human and nonhuman. The invention is also directed to a method for treating a targeted disease, comprising administering an effective amount of a composition comprising the polyalkylene oxide conjugated polypeptide or protein of the invention and a pharmaceutically acceptable carrier vehicle, wherein the polyalkylene oxide conjugated polypeptide is conjugated to one or plurality of bioactive molecules, such as peptides, lipids, nucleic acids (i.e., phosphate-lysine complexes), drug, toxin, boron addend or radioisotope molecule(s), or conjugated to a carrier having one or plurality of peptides, lipids, nucleic acids (i.e., phosphate-lysine complexes), drug, toxin, boron addend or radioisotope molecule(s) bound to the carrier. Brief Description ofthe Drawings Figure 1 is a graphical representation of three competition ELISA's in which unlabeled PEG modified CC49/212 SCA (closed squares), CC49/212 SCA (open squares), CC49 IgG (open circles), and MOPC-21 IgG (+) competed against a CC49 IgG radiolabeled with I25 I for binding to the TAG-72 antigen on a human breast carcinoma extract. Figure 2 shows the DNA and protein sequence of CC49/218 SCA which has four engineered cysteine residues at the positions indicated by the codons underlined and marked by an asterisk. Also highlighed are the CDR sequences (double underlined) and the 218 linker (underlined and labeled). In addition, there are four natural cysteine residues in the protein which are involved in two disulfide bonds. These are not underlined. The four engineered cysteine residues occur independently in four different mutants currently, but may be combined in the exact four-mutant codon version shown in this figure. Figure 3 shows the DNA and protein sequence of CC49/218 SCA with an engineered oligo-lysine C-terminal tail segment. The eight new lysine residues were genetically engineered at a B stEII site and are shown underlined and marked with asterisks. Also highlighted are the CDR sequences (double underlined), the 218 linker (underlined and labeled) and selected restriction sites. Figure 4 is a graphical representation of three competition ELISA's in which unlabeled SC-PEG unreacted CC49/218 SCA (closed squares), CC49/218 SCA (open squares), unlabeled XUS-PEG unreacted CC49/218 SCA (open circles), SC-PEG modified CC49/218 SCA (closed circles), XUS-PEG modified CC49/218 SCA (open triangles), CC49 IgG (closed triangles), an Anti-FITC SCA (dashed line) or BL-3 IgG (dotted line) were competed against a CC49 IgG radiolabeled with 125 I for binding to the TAG- 72 antigen on a human breast carcinoma extract. Figure 5 shows the pharmacokinetics of plasma retention of SCA and PEG-SCA. The details ofthe experiment are described in Example 13. Figure 6 shows an SDS-PAGE of the purified CC49-multimers cross- linked by PEG5000 under reducing conditions. The details ofthe experiment are described in Example 14. The lanes ofthe gel contain the following: 1) trimeric form; 2) dimeric form; 3) dimeric form; 4) mixed population; 5) native CC49; 6) PEG-CC49 monomer; 7) PEG-CC49 monomer; 8) empty; 9) empty; and 10) molecular weight standards. Figure 7 shows the binding kinetics of Mono-, Di-, Tri-, -PEG-CC49. The details of the experiment are described in Example 14. Native CC49 is represented by the solid box. PEG-mono-CC49 is represented by the open box. PEG-Di-CC49 is represented by the solid diamond. PEG-Tri-CC49 is represented by the open diamond. Figure 8 shows the results ofthe competition assay performed in Example 16. Nat is native CC49-SCA, C2 is PEG SC2000-CC49-SCA; GC is glyco- CC49-SCA; B* is the biotinylated CC49-SCA; C 12 is the PEG-SC 12,000-CC49- SCA; F5 is PEG-Flan-5000-CC49-SCA; and C20 is PEG-SC20000-CC49-SCA. Description ofthe Embodiments The present invention is directed to the novel combination of a polyalkylene glycol and a single chain polypeptide having binding affinity for an antigen, the polyalkylene glycol and polypeptide preferably being joined together by means of a coupling agent. Single Chain Polypeptides The invention relates to the discovery that polyalkylene oxide conjugated single-chain antigen-binding proteins ("SCA") or single-chain variable fragments of antibodies ("sFv"), such as PEGylated SCA proteins, have significant utility beyond that of the nonPEGylated single-chain antigen-binding proteins. In addition to maintaining an antigen binding site, a PEGylated SCA protein has a PEG moiety which reduces antigenicity and increases the halflife ofthe modified polypeptide in the bloodstream. Accordingly, the invention is directed to monovalent and multivalent SCA proteins capable of PEGylation, compositions of monovalent and multivalent PEGylated SCA proteins, methods of making and purifying monovalent and multivalent PEGylated SCA proteins, and uses for PEGylated SCA proteins. The invention is also directed to PEGylated SCA proteins having a diagnostic or therapeutic agent covalently attached to an Cys- linked PEGylated polypeptide or an oligo-Lys linked PEGylated polypeptide. Theterms "single-chain antigen-binding molecule" (SCA) or "single-chain Fv" (sFv) are used interchangeably. They are structurally defined as comprising the binding portion of a first polypeptide from the variable region of an antibody V L (or V H ), associated with the binding portion of a second polypeptide from the variable region of an antibody V H (or V L ), the two polypeptides being joined by a peptide linker linking the first and second polypeptides into a single polypeptide chain, such that the first polypeptide is N-terminal to the linker and second polypeptide is C-terminal to the first polypeptide and linker. The single polypeptide chain thus comprises a pair of variable regions connected by a polypeptide linker. The regions may associate to form a functional antigen- binding site, as in the case wherein the regions comprise a light-chain and a heavy- chain variable region pair with appropriately paired complementarity determining regions (CDRs). In this case, the single-chain protein is referred to as a "single- chain antigen-binding protein" or "single-chain antigen-binding molecule." Single-chain Fvs can and have been constructed in several ways. Either V L is the N-terminal domain followed by the linker and V H (a V L -Linker- V H construction) or V H is the N-terminal domain followed by the linker and V L (V H -Linker- V L construction). The preferred embodiment contains V L in the N- terminal domain (see, Anand, N.N., et al, J. Biol. Chem. 266:21874-21879 (1991)). Alternatively, multiple linkers have also been used. Several types of sFv (SCA) proteins have been successfully constructed and purified, and have shown binding affinities and specificities similar to the antibodies from which they were derived. A description ofthe theory and production of single-chain antigen-binding proteins is found in Ladner et al, U.S. Patent Nos. 4,946,778, 5,260,203, 5,455,030 and 5,518,889, and in Huston et al, U.S. Patent No. 5,091,513 ("biosynthetic antibody binding sites" (BABS)), all incorporated herein by reference. The single-chain antigen-binding proteins produced under the process recited in the above patents have binding specificity and affinity substantially similar to that ofthe corresponding Fab fragment. Typically, the Fv domains have been selected from the group of monoclonal antibodies known by their abbreviations in the literature as 26-10, MOPC 315, 741F8, 520C9, McPC 603, D1.3, murine phOx, human phOx, RFL3.8 sTCR, 1 A6, Sel55-4, 18-2-3, 4-4-20, 7A4-1, B6.2, CC49, 3C2, 2c, MA- 15C5/K 12 G 0 , Ox, etc. (see, Huston, J.S. et al, Proc. Natl. Acad. Sci. USA £5:5879-5883 (1988); Huston, J.S. et al, SIM News 38(4) (Supp.):\ \ (1988); McCartney, J. et al , ICSU Short Reports 70:114 (1990); McCartney, J.E. et al. , unpublished results (1990); Nedelman, M.A. et al, J. Nuclear Med. 32 (Supp.):1005 (1991); Huston, J.S. et al, In: Molecular Design and Modeling: Concepts and Applications, Part B, edited by J.J. Langone, Methods in Enzymology 203:46-88 (1991); Huston, J.S. et al, In: Advances in the Applications of Monoclonal Antibodies in Clinical Oncology, Epenetos, A.A. (Ed.), London, Chapman & Hall (1993); Bird, R.E. et al, Science 242:423-426 (1988); Bedzyk, W.D. et al, J. Biol Chem. 265: 18615-18620 (1990); Colcher, D. et al, J. Nat. Cancer Inst. 82:1191-1197 (1990); Gibbs, R.A. et al, Proc. Natl. Acad. Sci. USA 88:4001 -4004 ( 1991 ); Milenic, D.E. et al. , Cancer Research 57:6363-6371 (1991); Pantoliano, M.W. et al, Biochemistry 30:10117-10125 (1991); Chaudhary, V.K. et al, Nature 339:394-397 (1989); Chaudhary, V.K. et al, Proc. Natl Acad. Sci. USA 57:1066-1070 (1990); Batra, J.K. et al, Biochem. Biophys. Res. Comm. 777:1-6 (1990); Batra, J.K. et al, J. Biol. Chem. 2(55:15198-15202 (1990); Chaudhary, V.K. et al, Proc. Natl. Acad. Sci. USA 57:9491-9494 (1990); Batra, J.K. et al, Mol. Cell Biol. 77:2200-2205 (1991); Brinkmann, U. et al, Proc. Natl Acad. Sci. USA 55:8616-8620 (1991); Seetharam, S. et al, J. Biol. Chem. 26(5:17376-17381 (1991); Brinkmann, U. et al, Proc. Natl. Acad. Sci. USA 5 :3075-3079 (1992); Glockshuber, R. et al, Biochemistry 2P:1362-1367 (1990); Skerra, A. et al, Bio/Technol P:273-278 (1991); Pack, P. et al, Biochemistry 37:1579-1534 (1992); Clackson, T. et al, Nature 352:624-62% {1991); Marks, J.D. etα/.,J. Mol. Biol. 222:581-597 (1991); Iverson, B.L. et al. , Science 249:659-662 (1990); Roberts, V. A. et al , Proc. Natl Acad. Sci. USA 57:6654-6658 (1990); Condra, J.H. et al, J. Biol Chem. 265:2292-2295 (1990); Laroche, Y. et al, J. Biol. Chem. 26(5:16343-16349 (1991); Holvoet, P. et /., J. Biol. Chem. 266:19717-19724 (1991); Anand, Ν.Ν. et al, J. Biol. Chem. 266:21874-21879 (1991); Fuchs, P. et al, Bio/Technol. P:1369-1372 (1991); Breitling, F. et al, Gene 104:104-153 (1991); Seehaus, T. et al, Gene 114:235-237 (1992); Takkinen, K. et al, Protein Engng. 4:837-841 (1991); Dreher, M.L. et al, J. Immunol. Methods 139:197-205 (1991); Mottez, E. et al, Eur. J. Immunol. 27:467-471 (1991); Traunecker, A. et al, Proc. Natl. Acad. Sci. USA 55:8646-8650 (1991); Traunecker, A. et al, EMBO J. 10:3655- 3659 (1991); Hoo, W.F.S. et al, Proc. Natl. Acad. Sci. USA 5P:4759-4763 (1993)). Linkers of the invention used to construct sFv (SCA) polypeptides are designed to span the C-terminus of V L (or neighboring site thereof) and the Ν- terminus of V H (or neighboring site thereof) or between the C-terminus of V H and the Ν-terminus of V L . The preferred length ofthe peptide linker should be from 2 to about 50 amino acids. In each particular case, the preferred length will depend upon the nature ofthe polypeptides to be linked and the desired activity ofthe linked fusion polypeptide resulting from the linkage. Generally, the linker should be long enough to allow the resulting linked fusion polypeptide to properly fold into a conformation providing the desired biological activity. Where conformational information is available, as is the case with sFv (SCA) polypeptides discussed below, the appropriate linker length may be estimated by consideration ofthe 3-dimensional conformation ofthe substituent polypeptides and the desired conformation ofthe resulting linked fusion polypeptide. Where such information is not available, the appropriate linker length may be empirically determined by testing a series of linked fusion polypeptides with linkers of varying lengths for the desired biological activity. Such linkers are described in detail in WO 94/12520, incorporated herein by reference. Preferred linkers used to construct sFv (SCA) polypeptides have between 10 and 30 amino acid residues. The linkers are designed to be flexible, and it is recommended that an underlying sequence of alternating Gly and Ser residues be used. To enhance the solubility ofthe linker and its associated single chain Fv protein, three charged residues may be included, two positively charged lysine residues (K) and one negatively charged glutamic acid residue (E). Preferably, one ofthe lysine residues is placed close to the N-terminus of V H , to replace the positive charge lost when forming the peptide bond ofthe linker and the V H .Such linkers are described in detail in U.S. Patent Application S. N. 08/224,591, filed April 7, 1994, incorporated herein by reference. See also, Whitlow, M., et al, Protein Engng. 7:1017-1026 (1994). For multivalent sFvs (SCA), the association of two or more sFvs (SCA) is required for their formation. Although, multivalent sFvs (SCA) can be produced from sFvs (SCA) with linkers as long as 25 residues, they tend to be unstable. Holliger, P., et al, Proc. Natl. Acad. Sci. USA P0:6444-6448 (1993), have recently demonstrated that linkers 0 to 15 residues in length facilitate the formation of divalent Fvs. See, Whitlow, M., etal, Protein Engng. 7:1017-1026 (1994); Hoogenboom, H.R., Nature Biotech. 75:125-126 (1997); and WO 93/11161. An object ofthe present invention is to produce a single-chain antigen- binding polypeptide-polyalkylene oxide conjugate which retains antigen binding affinity within a range of about two-fold to about ten-fold ofthe antigen binding affinity ofthe native single-chain antigen-binding polypeptide. Another object ofthe present invention is to produce an sFv (SCA) having one or more Cys residues such that the Cys residue is capable of being conjugated with PEG and the PEGylated polypeptide is capable of binding an antigen (i.e., the PEGylated polypeptide's ability to bind an antigen is not disrupted). A further object ofthe present invention is to produce an sFv (SCA) having three or more consecutive Lys residues such that the Lys residues are capable of being conjugated with PEG and the PEGylated polypeptide is capable of binding an antigen (i.e., the PEGylated polypeptide's ability to bind an antigen is not disrupted). These novel sFv (SCA) proteins may be conjugated to activated polyethylene glycol (PEG) such that the PEG modification occurs only (or preferentially) at the specifically engineered sites. The activated PEG molecules would be thiol-reactive or amine-reactive polymers such as are well known in the art. The designed changes correspond to amino acid residues on the sFv (SCA) surface which are well separated spatially from the antigen-binding site as deduced from known three-dimentional models ofthe antibody Fv domain. A further object ofthe invention is to produce monovalent and multivalent sFvs (SCA) having one or more Cys PEG conjugation sequence(s). A further object of the invention is to produce monovalent and multivalent sFvs (SCA) having three or more consecutive Lys (i.e., oligo-Lys) PEG conjugation sequence(s). For multivalent sFv (SCA), the association of two or more sFvs (SC As) is required for their formation. For example, multivalent sFvs (SCAs) may be generated by chemically crosslinking two sFvs (SCAs) with C-terminal cysteine residues (Cumber et al. , J. Immunol. 149:120- 126 ( 1992)) and by linking two sFvs (SCAs) with a third polypeptide linker to form a dimeric Fv (SCA)(George et al, J. Cell. Biochem. 15E 27 (1991)). Details for producing multivalent sFvs (SCAs) by aggregation are described in Whitlow, M., et al, Protein Engng. 7: 1017- 1026 ( 1994). Multivalent antigen-binding fusion proteins of the invention can be made by any process, but preferably according to the process formaking multivalent antigen-binding proteins set forth in WO 93/11161, incorporated herein by reference. Identification and Synthesis of Site Specific PEGylation Sequences In the present invention, Cys PEGylation sites may occur in the V L and V H regions, adjacent to the C-terminus ofthe polypeptide (V L , V H or neighboring site thereof), the N-terminus ofthe polypeptide (V L , V H or neighboring site thereof), the linker region between the first and second polypeptide regions, or occur in a combination of these regions. In the present invention, oligo-Lys PEGylation sites may occur in the polypeptide linker or in the C-terminus or adjacent to the C-terminus of the polypeptide. The design of the PEG conjugaton sites on a protein involves examining the structural information known about the protein and the residues in the proteins involved in antigen binding. The PEG conjugaton sites are chosen to be as far from these residues as possible so as to prevent disruption ofthe antigen-binding site. The Cys or the oligo-Lys PEGylation site may occur in (1) the native C- terminus of V L (or V H ), (2) the C-terminus of V L (or V H ) wherein the C-terminus has a deletion of one or plurality of amino acid residue(s), such that the remaining N-terminus amino acid residues ofthe peptide are sufficient for the PEGylated polypeptide to be capable of binding an antigen or (3) the C-terminus of V L (or V H ) wherein the C-terminus has an addition of one or plurality of amino acid residue(s), such that the remaining N-terminus amino acid residues ofthe peptide are sufficient for the PEGylated polypeptide to be capable of binding an antigen. By "native" is intended the naturally occurring C-terminus ofthe immunoglobulin (first or second polypeptide). By "C-terminus" it is well understood in the art as intending the C-terminal amino acid residue or the C-terminal region of the polypeptide, which could include up to all of the amino acid residues of the polypeptide excluding the first N-terminal amino acid residue ofthe polypeptide. However, in the present invention, "C-terminus" is intended as the C-terminal amino acid residue ofthe above mentioned three types of C-terminus ( 1 , 2, or 3), unless otherwise indicated or intended. PEGylation sites were identified and engineered at residues within loop sites in regions of the sFv (SCA) that are diametrically opposed to the antigen binding site. The five loop regions and C-terminal extension chosen as preferred sites of glycosylation are among the most distant regions spatially removed from the binding site. The six furthest portions of an sFv (SCA) from the antigen binding site are as follows: 1) The loop made up of residues 11 to 15 in the light chain; 2) The loop made up of residues 77 to 79 in the light chain; 3) The N-terminus ofthe linker; 4) The loop made up of residues 11 to 15 in the heavy chain; 5) The loop made up of residues 82B, 82C and 83 in the heavy chain; and 6) The C-terminus of the sFv (or SCA). The residues are identified as according to Kabat et al. , Sequences of Proteins of Immunological Interest, 5th ed., U.S. Dept. Health and Human Services, Bethesda, MD (1991). These possible PEGylation sites were determined by examining the 4-4-20 mouse Fab structure {see, Whitlow, M. et al, Protein Engng. 8:749-761 (1995), incorporated herein by reference). After identifying the loops furthest from the antigen binding site, the nucleic and amino acid sequences of each loop are examined for possible Cys PEGylation sites that may be engineered into the loop region. The engineered placement ofthe Cys residue anywhere in these six identified regions can generate a preferred site for sFv (SCA) PEGylation. The engineered placement of the oligo-Lys residues in the linker, the C-terminus ofthe sFv (SCA)and/ or adjacent to the C-terminus of the sFv (SCA) can generate a preferred site for sFv PEGylation. The design approach described above has been used for the CC49/218 SCA. Figure 2 shows the following resulting designs: designed PEGylation site no. 1 in the light chain ofthe CC49/218 SCA; designed PEGylation site no.2 in the N-terminal end ofthe linker in CC49/218 SCA; designed PEGylation site no. 3 in the heavy chain ofthe CC49/218 SCA; designed PEGylation site no.4 at the C-terminus of the CC49/218 SCA. Figure 3 shows the following resulting designs: designed oligo-Lys "hot spot" PEGylation sites at the C-terminus ofthe CC49/218 SCA. Any combination of these sites could be used. The particular nucleotide sequence which is used to introduce a Cys or oligo-Lys PEGylation site into the various positions will depend upon the naturally-occurring nucleotide sequence. The most preferred sites are those in which it takes a minimum number of changes to generate the PEGylation site. Of course, based on the redundancy ofthe genetic code, a particular amino acid may be encoded by multiple nucleotide sequences. Site-directed mutagenesis is used to change the native protein sequence to one that incorporates the Cys residue or oligo-Lys residues for PEGylation. The mutant protein gene is placed in an expression system, such as bacterial cells, yeast or other fungal cells, insect cells or mammalian cells. The mutant protein can be purified by standard purification methods. Oligonucleotide-directed mutagenesis methods for generating the Cys or oligo-Lys PEGylation sites and related techniques for mutagenesis of cloned DNA are well known in the art. See, Sambrook et al, MOLECULAR CLONING: A LABORATORY MANUAL, 2nd ed., Cold Spring Harbor Laboratory, Cold Spring Harbor, N. Y. ( 1989); Ausubel et al. (eds.), CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley and Sons ( 1987), both incorporated herein by reference. A preferred oligonucleotide-directed mutagenesis method for the present invention is according to Ho etal, Gene 77:51-59 (1989), incorporated herein by reference. Hosts and Vectors After mutating the nucleotide sequence of the sFv (SCA), the mutated DNA can be inserted into a cloning vector for further analysis, such as for confirmation ofthe DNA sequence. To express the polypeptide encoded by the mutated DNA sequence, the DNA sequence is operably linked to regulatory sequences controlling transcriptional expression and introduced into either a prokaryotic or eukaryotic host cell. Although sFvs (SCAs) are typically produced by prokaryotic host cells, eukaryotic host cells are the preferred host cells. Preferred host cells include yeast or other fungal cells, insect cells or mammalian cells. Standard protein purification methods may be used to purify these mutant proteins. Only minor modification to the native protein's purification scheme may be required. Also provided by the invention are DNA molecules such as purified genetic sequences or plasmids or vectors encoding the sFv (SCA) ofthe invention that have engineered Cys residues and/or oligo-Lys residues capable of PEG conjugation. The DNA sequence for the PEGylated sFv (SCA) polypeptide can be chosen so as to optimize production in organisms such as prokaryotes, yeast or other fungal cells, insect cells or mammalian cells. The DNA molecule encoding an sFv (SCA) having Cys residues and/or oligo-Lys residues for PEG conj ugation can be operably linked into an expression vector and introduced into a host cell to enable the expression ofthe engineered sFv (SCA) protein by that cell. A DNA sequence encoding an sFv (SCA) having Cys and/or oligo-Lys PEGylation sites may be recombined with vector DNA in accordance with conventional techniques. Recombinant hosts as well as methods of using them to produce single chain proteins ofthe invention are also provided herein. The expression of such sFv (SCA) proteins of the invention can be accomplished in procaryotic cells. Preferred prokaryotic hosts include, but are not limited to, bacteria such as Neisseria, Mycobacteria, Streptococci, Chlamydia and E coli. Eukaryotic hosts for cloning and expression of such sFv (SCA) proteins ofthe invention include insect cells, yeast, fungi, and mammalian cells (such as, for example, human or primate cells) either in vivo, or in tissue culture. A preferred host for the invention is Pichia pastoris. The appropriate DNA molecules, hosts, methods of production, isolation and purification of monovalent, multivalent and fusion forms of proteins, especially sFv (SCA) polypeptides, are thoroughly described in the prior art, such as, e.g., U.S. Patent No. 4,946,778, which is fully incorporated herein by reference. The sFv (SCA) encoding sequence having Cys residues and/or oligo-Lys residues for PEG conjugation and an operably linked promoter may be introduced into a recipient prokaryotic or eukaryotic cell either as a non-replicating DNA (or RNA) molecule, which may either be a linear molecule or, more preferably, a closed covalent circular molecule. Since such molecules are incapable of autonomous replication, the expression of the desired sFv (SCA) protein may occur through the transient expression ofthe introduced sequence. Alternatively, permanent expression may occur through the integration of the introduced sFv (SCA) sequence into the host chromosome. In one embodiment, the sFv (SCA) sequence can be integrated into the host cell chromosome. Cells which have stably integrated the introduced DNA into their chromosomes can be selected by also introducing one or more markers which allow for selection of host cells which contain the sFv (SCA) sequence and marker. The marker may complement an auxotrophy in the host (such as his4, leu2, or ura3, which are common yeast auxotrophic markers), biocide resistance, e.g., antibiotics, or resistance to heavy metals, such as copper, or the like. The selectable marker gene can either be directly linked to the sFv (SCA) DNA sequence to be expressed, or introduced into the same cell by co-transfection. In another embodiment, the introduced sequence will be incoφorated into a plasmid vector capable of autonomous replication in the recipient host cell. Any of a wide variety of vectors may be employed for this purpose. Factors of importance in selecting a particular plasmid or viral vector include: the ease with which recipient cells that contain the vector may be recognized and selected from those recipient cells which do not contain the vector; the number of copies ofthe vector which are desired in a particular host; and whether it is desirable to be able to "shuttle" the vector between host cells of different species. Any of a series of yeast vector systems can be utilized. Examples of such expression vectors include the yeast 2-micron circle, the expression plasmids YEP13, YCP and YRP, etc., or their derivatives. Such plasmids are well known in the art (Botstein et al, Miami Wntr. Symp. 7P:265-274 (1982); Broach, J.R., In: The Molecular Biology of the Yeast Saccharomyces: Life Cycle and Inheritance, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, p. 445- 470 (1981); Broach, J.R., Cell 25:203-204 (1982)). For a mammalian host, several possible vector systems are available for expression. One class of vectors utilize DNA elements which provide autonomously replicating extra-chromosomal plasmids, derived from animal viruses such as bovine papilloma virus, polyoma virus, adenovirus, or S V40 virus. A second class of vectors relies upon the integration ofthe desired gene sequences into the host chromosome. Cells which have stably integrated the introduced DNA into their chromosomes may be selected by also introducing one or more markers which allow selection of host cells which contain the expression vector. The marker may provide for prototrophy to an auxotrophic host, biocide resistance, e.g., antibiotics, or resistance to heavy metals, such as copper or the like. The selectable marker gene can either be directly linked to the DNA sequences to be expressed, or introduced into the same cell by co-transformation. Additional elements may also be needed for optimal synthesis of mRNA. These elements may include splice signals, as well as transcription promoters, enhancers, and termination signals. The cDNA expression vectors incorporating such elements include those described by Okayama, H., Mol Cell. Biol. 3:280 (1983), and others. Among vectors preferred for use in bacteria include pQE70, pQE60 and pQE-9, available from Qiagen; pBS vectors, Phagescript vectors, Bluescript vectors, pNH8A, pNHlόa, pNH18A, pNH46A, available from Stratagene; and ptrc99a, pKK223-3, pKK233-3, pDR540, pRIT5 available from Pharmacia. Among preferred eukaryotic vectors are pWLNEO, pSV2CAT, pOG44, pXTl and pSG available from Stratagene; and pSVK3, pBPV, pMSG and pSVL available from Pharmacia. Preferred vectors for expression in Pichia are pHIL-S 1 (Invitrogen Corp.) and pPIC9 (Invitrogen Corp.). Other suitable vectors will be readily apparent to the skilled artisan. Once the vector or DNA sequence containing the constructs has been prepared for expression, the DNA constructs may be introduced or transformed into an appropriate host. Various techniques may be employed, such as transformation, transfection, protoplast fusion, calcium phosphate precipitation, electroporation, or other conventional techniques. After the cells have been transformed with the recombinant DNA (or RNA) molecule, the cells are grown in media and screened for appropriate activities. Expression of the sequence results in the production of the mutant sFv (SCA) for PEG conjugation of the present invention. Straight chain Polymers The straight chain polyalkylene glycols employed in the practice of the present invention are ofthe structural formula wherein R is selected from the group consisting of hydrogen, lower alkyl, and mixtures thereof, R 1 is selected from the group consisting of hydrogen and lower alkyl, and n is a positive integer. By "lower alkyl" is meant an alkyl group having from one to four carbon atoms, i.e., methyl, ethyl, propyl, butyl, and isomers of the foregoing. R is preferably selected from the group consisting of hydrogen, methyl, and mixtures thereof, R 1 is preferably selected from the group consisting of hydrogen and methyl, and n is preferably a positive integer of 500 or less. R is most preferably hydrogen, R 1 is most preferably methyl, and n is most preferably an integer of 7 to 150. It will be readily apparent to those skilled in the art that the preferred poly(alkylene glycols) employed in the practice ofthe present invention are poly(ethylene glycol), poly(propylene glycol), mixtures thereof, and copolymers of poly(ethylene glycol) and poly(propylene glycol), wherein one of the terminal hydroxyl groups ofthe polymer may be substituted with a lower alkyl group. A preferred polyalkylene glycol for use in the present invention is poly(ethylene glycol)-hydrazine. The most preferred polyalkylene glycol for use in the present invention is methoxy polyethylene glycol). Hereinafter, for convenience, the polyalkylene glycol employed in the practice ofthe present invention will be designated PAG, which term is intended to include both compounds wherein R 1 is hydrogen and compounds wherein R 1 is alkyl. PEG refers to poly(ethylene glycol) and mPEG refers to methoxy poly(ethylene glycol). The PAG does not have to be of a particular molecular weight, but it is preferred that the molecular weight be between about 500 and about 40,000; more preferably, between about 2,000 and about 20,000. The choice of molecular weight of PAG is made based on the nature of the particular polypeptide employed, for example, the number of amino or other groups available on the polypeptide for modification. Molecular weights of about 10,000 and about 20,000 are most preferred. It is well known in the art that PAGs that contain two terminal hydroxyl groups per moiety are capable of crosslinking other polymers, e.g. proteins. Where, as is often the case, crosslinking would be deemed undesirable, such crosslinking can be minimized or prevented by means known in the art. For example, Davis et al. in U.S. Patent No. 4,179,337 have pointed out that a preferred means for preventing crosslinking is to preblock one end ofthe PAG, such as is done in the commercially available methoxy poly(ethylene glycol). The P AGs employed in the practice ofthe present invention are preferably coupled to polypeptides by means of suitable coupling agents . A useful review of a number of coupling agents that can be employed in the practice ofthe present invention appears in Dreborg etal, Critical Reviews in Therapeutic Drug Carrier Systems 6(4):315-365 (1990), see, especially, pp. 317-320. Probably the best known coupling agent for this purpose is cyanuric chloride. Its use has been described in numerous references, see, for example, Abuchowski et al, J. Biol. Chem. 252(77):3578-3581 (June 10, 1977). Zalipskyet /.,Ewr. Pol J. 7P(72J:1177-1183 (1983), among others, have described the reaction of methoxy poly(ethylene glycol) with succinic anhydride: O II mPΕGOH + CH 2 C O \ O > ■ mPΕG— O— C II— CH 2 CH,COOH / CH 2 C It is also known to alkylate mPΕG with ethylbromoacetate in the presence of a base such as K-tertiary butoxide in tertiary butanol, Na-naphthal ene in tetrahydrofuran, or butyl lithium in benzene: Base mPΕGOH + BrCHjCOOR +- mPΕG— OCH 2 COOH The terminal hydroxyl groups of PEG can be transformed into amine, carboxyl, or hexamethyl isocyanate groups. See, for example, Zalipsky et al, 1983, supra. A mixed anhydride derivative of carboxylated mPEG can be prepared in the presence of triethylamine and then reacted with proteins: Carboxylated mPEG can also be reacted with hydroxysuccinimide in the presence of dicyclohexylcarbodumide and dimethyl formamide for reaction with protein: King and Weiner {Int. J. Peptide Protein Res. 16: 147 ( 1980) describe the dithiocarbonate of mPEG: 1. cs 2 mPEGONa > ■ mPEG— OCSCH 2 CNH 2 2. CICH CONH, II II * * S O Beauchamp et al, Analytical Biochem. 737:25-33 (1983) describe the activation of PEG with 1 , 1 '-carbonyldiimidazole. Reaction of this derivative with a peptide yields a carbamate linkage: mPEGOH Veronese et al, Appl. Biochem. & Biotechnol 77:141-152 (1985) describe the activation of methoxy poly(ethylene glycol) with phenylchloroformates, e.g., 2,4,5-trichlorophenylchloroformate or p -nitrophenylchloroformate. These derivatives are linked to peptides by urethane linkages: mPEGOH + mPEGOH + Ueno et al. in European Patent Application 87103259.5 form mPEG imidoesters from the corresponding nitriles by reaction with dry hydrogen chloride in the presence of a dehydrated lower alcohol: PEGOH + _.rCH 2 CH 2 CH 2 CN — * ■ mPEGOCH 2 CH 2 CH 2 CN CH3OH HCl mPEGOCH 2 CH 2 CH 2 C=NH - HCl I OCH3 NaH mPEGOH + CH 2 =CHCN » ■ mPEGOCH 2 CH 2 CN CH 3 OH HCl mPEGOCH 2 CH 2 C=NH-HCI I OCH3 Abuchowski et al, Cancer Biochem. Biophys. 7.T75-186 (1984) have described forming mPEG succinate as described above and then forming methoxy polyethylene glycolyl succinimidyl succinate ("SS-PEG") by reaction with hydroxysuccinimide in the presence of dicyclohexylcarbodumide: c — CH, / DCC mPEGOCCH,CH,COOH + HON \ C — CH, II II NH 2 -Protein mPEGOCCH 2 CH 2 C— H-Protein -* — SS-PEG Sano et al, European Patent Application No. 89107960.0 disclose the phenyl glyoxal derivative of methoxy poly(ethylene glycol), which is capable of modifying the guanidino groups in peptides: mPEGOH + mP Zalipsky, in U.S. Patent No. 5,122,614, describes the activation of PEG by conversion into its N-succinimide carbonate derivative ("SC-PEG"): o o II II mPEGOH + C—CI 2 *- mPEGOCCI 1. N-hydroxysuccinimide 2. triethylamine methoxypoly(ethylene glycol) - succinyl carbonate SC - PEG Zalipsky etal.,J. Macromol. Sci. Chem..427:839, disclose the amino acid ester derivative of methoxy poly(ethylene glycol): O R II I PEG— O— C— CH— H 2 Davis etal, U.S. Patent No.4,179,337, disclose a hydrazide derivative of methoxy poly(ethylene glycol), which is capable of modifying aldehydes and ketones and other functional groups: o PEG— O— CH 2 — C— NH — NH 3 + Cr HZ-PEG It is further disclosed that the bifunctional derivative of PEG, i.e., polyethylene glycol-bis-succinidyl carbonate ("BSC-PEG") can be prepared by similar means. The SC-PEG and BSC-PEG compounds are then reacted with amine groups in a protein and attached thereto via urethane (carbamate) linkages. It will be readily apparent to those skilled in the art that other activated P AGs can also be employed in the practice ofthe present invention. The preferred activated PAG for use in the practice ofthe present invention is selected from the group consisting of SS-PEG and SC-PEG. The use of SC-PEG is most preferred. Branched Polymers The invention further provides for the use of branched, substantially non- antigenic polymers for polyalkylene oxide conjugation ofthe sFv (SCA) proteins corresponding to the formula: (R) n L-A (II) wherein (R) includes a water-soluble non-antigenic polymer; (n) = 2 or 3; (L) is an aliphatic linking moiety covalently linked to each (R); and (A) represents an activated functional group capable of undergoing nucleophilic substitution. For example, (A) can be a group which is capable of bonding with biologically active nucleophiles or moieties capable of doing the same. In particularly preferred aspects of the invention (R) includes a poly(alkylene oxide) PAO such as poly(ethylene glycol) PEG or mPEG. It is preferred that each chain have a molecular weight of between about 200 and about 12,000 daltons and preferably between about 1,000 and about 10,000 daltons. Molecular weights of about 5,000 daltons are most preferred. As shown in Formula II, 2 or 3 polymer chains, designated (R) herein, are joined to the alphatic linking moiety (L). Suitable aliphatics included substituted alkyl diamines and triamines, lysine esters and malonic ester derivatives. The linking moieties are perferably non-planar, so that the polymer chains are not rigidly fixed. The linking moiety (L) is also a means for attaching the mulitple polymer chains or "branches" to (A), the moeity through which the polymer attaches to the sFv (SCA) protein. (L) preferably includes a multiply-functionalized alykyl group containing up to 18, and more preferably between 1-10 carbon atoms. A heteroatom such as nitrogen, oxygen or sulfur may be included within the alkyl chain. The alkyl chain may also be branched at a carbon or nitrogen atom. In another aspect ofthe invention, (L) is a single nitrogen atom. (L) and (R) are preferably joined by a reaction between nucleophilic functional groups on both (R) and (L). Each (R) is suitably functionalized to undergo nucleophilic substitution and bond with (L). Such functionalization of polymers is readily apparent to those of ordinary skill in the art. A wide variety of linkages are contemplated between (R) and (L). Urethane (carbamate) linkages are preferred. The bond can be formed, for example, by reacting an amino group such as l,3-diamino-2-propanol with methoxypolyethylene glycol succinimidyl carbonate as described in U.S. Patent No. 5,122,614. Amide linkages, which can be formed by reacting an amino- terminated non-antigenic polymer suchas methoxypolyethylene glycol-amine (mPEG amine) with an acyl chloride functional group. Examples of other such linkages include ether, amine, urea, and thio and thiol analogs thereof, as well as the thio and thiol analogs ofthe urethane and amide linkages discussed supra. The moiety (A) of Formula II represents groups that "activate" the branched polymers ofthe present invention for conjugation with biologically active materials. (A) can be a moiety selected from: 1. Functional groups capable of reacting with an amino group such as: a) carbonates such as the p-nitrophenyl or succinimidyl; b) carbonyl imidazole; c) azlactones; d) cyclic imide thiones; or e) isocyanates or isothiocyanates. 2. Functional groups capable of reacting with carboxylic acid groups and reactive with carbonyl groups such as: a) primary amines; or b) hydrazine and hydrazide functional groups such as the acyl hydrazides, carbazates, semicarbamates, thiocarbazates, etc. 3. Functional groups capable of reacting with mercapto or sulfhydryl groups such as phenyl glyoxals; see, for example, U.S. Patent No. 5,093,531. 4. Other nucleophiles capable of reacting with an electrophilic center. A non-limiting list includes, for example, hydroxyl, amino, carboxyl, thiol groups, active methylene and the like. The moiety (A) can also include a spacer moiety located proximal to the aliphatic linking moiety (L). The spacer moiety may be a heteroalkyl, alkoxyl, alkyl containing up to 18 carbon atoms or even an additional polymer chain. The spacer moieties can be added using standard synthesis techniques. The branched polymers, generally, U-PAO's or U-PEG's, are formed using conventional reaction techniques known to those of ordinary skill in the art. These umbrella-like branched polymers ofthe present invention (U-PAO' s or U-PEG's) react with biologically active nucleophiles to form conjugates. The point of polymer attachment depends upon the functional group (A). For example, (A) can be a succinimidyl succinate or carbonate and react with e-amino lysines. The branched polymers can also be activated to link with any primary or secondary amino group, mercapto group, carboxylic acid group, reactive carbonyl group or the like found on biologically active polypeptides. Other groups are apparent to those of ordinary skill in the art. One ofthe main advantages ofthe use ofthe branched polymers is that the branching imparts an umbrella-like three dimensional protective covering to the materials they are conjugated with. This contrasts with the string-like structure ofthe straight chain polymers discussed, supra. An additional advantage of the branched ploymers is that they provide the benefits associated with attaching several strands of polymers to a sFv protein but require substantially fewer conjugation sites. The desired properties of PEGylation are realized and the loss of bioactivity is minimized. One or more of the activated branched polymers can be attached to a biologically active nucleophile, such as an sFv protein, by standard chemical reactions. The conjugate is represented by the formula: [(R) n L-A'] z - (nucleophile) (III) wherein (R) is a water-soluble substantially non-antigenic polymer; n=2 or 3; (L) is an aliphatic linking moiety; (A 1 ) represents a linkage between (L) and the nucleophile and (z) is an integer > 1 representing the number of polymers conjugated to the biologically active nucleophile. The upper limit for (z) will be determined by the number of available nucleophilic attachment sites and the degree of polymer attachment sought by the artisan. The degree of conjugation can be modified by varying the reaction stoichimetry using well-known techniques. More than one polymer conjugated to the nucleophile can be obtained by reacting a stoichimetric excess ofthe activated polymer with the nucleophile. Puriflcation ofsFv Proteins A generic protocol that has been developed and used to produce twelve different single chain antigen binding molecules. It involves cell lysis and washing, solubilization in a denaturing solvent, refolding by dilution, and two ion-exchange HPLC chromatography steps. Such isolated sFvs (SCAs) are capable of being PAG conjugated according to the present invention. The fermentation of the sFv-producing E coli strains are performed at 32 °C using a casein digest-glucose-salts medium. At an optical density of 18 to 20 at 600 nm, sFv expression is induced by a 42° C temperature shock for one hour. After the fermentation is cooled to 10°C, the cells are harvested by centrifugation at 7000g for ten minutes. The wet cell paste is then stored frozen at -20 °C. Approximately 200 to 300 g of wet cell paste is normally recovered from one 10-liter fermentation. For protein recovery, the cell paste from three 10-liter fermentations (600- 900 g) is thawed overnight at 4°C and gently resuspended at 4°C in 50 mM Tris- HC1, 1.0 mM ΕDTA, 100 mM KC1, 0.1 mM phenylmethylsulfonyl chloride (PMSF), pH 8.0 (lysis buffer), using 10 liters of lysis buffer for every kilogram of wet cell paste. When thoroughly resuspended, the chilled mixture is passed three times through a Manton-Gaulin cell homogenizer to fully lyse the cells. Because the cell homogenizer raises the temperature ofthe cell lysate to 25±5 °C, the cell lysate is cooled to 5±2°C with a Lauda/Brinkman chilling coil after each pass. Complete lysis is verified by visual inspection under a microscope. The cell lysate is centrifuged at 24,3 OOg for thirty minutes at 6 °C using a Sorvall RC-5B centrifuge. The pellet contains the insoluble sFv and the supernatant is discarded. The pellet is washed by gently scraping it from the centrifuge bottles and resuspending it in 5 liters of lysis buffer/kg of wet cell paste. The resulting 3.0-4.5-liter suspension is again centrifuged at 24,300g for 30 min at 6 °C, and the supernatant is discarded. This washing ofthe cell pellet removes soluble E. coli proteins and can be repeated as many as five times. At any time during this washing procedure the material can be stored as a frozen pellet at -20 °C. A substantial time saving in the washing steps can be accomplished by utilizing a Pellicon tangential flow apparatus equipped with 0.22-μm microporous filters. The washed cell pellet is solubilized at 4°C in freshly prepared 6 M guanidine hydrochloride, 50 mM Tris-HCl, 10 mM CaCl 2 , 50 mM KC1, pH 8.0 (denaturing buffer), using 6 ml/g of pellet. If necessary, a few quick pulses from a Heat Systems Ultrasonics tissue homogenizer can be used to complete the solubilization. The resulting suspension is centrifuged at 24,300g for 45 minutes at 6°C and the pellet is discarded. The optical density of the supernatant is determined at 280 nm and if the OD 280 is above 30, additional denaturing buffer is added to obtain an OD 2g0 of approximately 25. The supernatant is slowly diluted into cold (4-7 °C) refolding buffer (50 mM Tris-HCl, 10 mM CaCl 2 , 50 mM KC1, 0.1 mM PMSF, pH 8.0) until a 1 :10 to 1:100 dilution is reached (final volume 70-120 liters). The refolding buffer should be prepared at least one day prior to use, to allow sufficient time for it to cool to 4°C. The best results will be obtained when the supernatant is slowly added to the refolding buffer over a two hour period, with gentle mixing. The solution is left undisturbed for at least twenty hours and then filtered through a Millipore Pellicon tangential flow apparatus at 4°C with four to six 0.45-μm microporous membranes (HVLP 000 C5). The filtrate is concentrated to 1 to 2 liters using a Pellicon apparatus with four to six 10,000 NMWL cassettes (SK1PA156A4), again at 4°C. The concentrated crude sFv sample is buffer exchanged at 4°C into 20 mM 2-[N-morpholino]ethanesulfonic acid (Mes), 0.3 mM CaCl 2 , pH 6.0, using the Pellicon ultrafiltration apparatus equipped with four to six 10,000 NMWL cassettes. The sample is then chromatographed on a Waters Accell Plus CM ion- exchange (RCM) column (4.7 x 30.0 cm). Prior to loading on the HPLC, the material is filtered through a 0.22-μm filter and the Accell column is equilibrated with Buffer A (40 mM Mes, 1 mM CaCl 2 , pH 6.0). Following sample loading, the Accell column is eluted over a 55-minute period with a linear gradient of Buffer A and Buffer B (40 mM Mes, 100 mM CaCl 2 , pH 7.0). (See Table 1). The Accell Plus CM column has a capacity of about 3 g and thus all the crude sFv sample can normally be loaded in a single run. The fractions are analyzed using 4-20% Novex SDS-PAGE gels and the peak fractions are pooled. Normally, the sFv elutes from the Accell ion-exchange column quite early in the gradient. To enhance resolution for certain sFv proteins, holds in the gradient can be implemented. The pooled fractions from the Accell HPLC purification are dialyzed against Buffer D (40 mM 3-[N-mo holino]propanesulfonic acid (Mops), 0.5 mM Ca acetate, pH 6.0) until the conductivity is lowered to that of Buffer D. The sample is then loaded on a 21.5 x 150-mm poly aspartic acid Poly CAT A column. If more than 60 mg is loaded on this column, the resolution begins to deteriorate; thus, the pooled fractions from the Accell HPLC purification often must be divided into several PolyCAT A runs. Most sFv proteins have an extinction coefficient of about 2.0 mg ml "1 cm '1 at 280 nm and this can be used to determine protein concentration. The sFv sample is eluted from the PolyCAT A column with a 50-min linear gradient of Buffer D and Buffer E (40 mM Mops, 10 mM Ca acetate, pH 8.0). See Table 2. The sFv proteins will often elute between 20 and 26 min when this gradient is used. This corresponds to an eluting solvent composition of approximately 70% Buffer D and 30% Buffer E. This purification procedure yields sFv proteins that are more than 95% pure as examined by SDS-PAGE and Scatchard analysis. Modifications ofthe above procedure may be dictated by the isoelectric point of the particular sFv being purified, which is often between 8.0 and 9.3. The polyalkylene glycols (PAGs) employed in the practice ofthe present invention, which, as indicated above, are preferably activated by reaction with a coupler, can be reacted with any of several groups that may be present attached to the chain ofthe single chain antigen binding molecules, e.g. terminal carboxyl groups, thiol groups, phenolic hydroxyl groups, or primary amino groups located at the chain terminus or along the chain. It is preferred to react activated PAGs with primary amine groups, especially those occurring along the peptide chain. It is most preferred that the activated PAGs be coupled to the e amino groups of lysine residues as well as cysteine residues in the polypeptide. The reaction between the PAG and the single chain polypeptide is normally carried out in solution, preferably an aqueous buffer solution providing a pH in the range of from about 6 to about 10, preferably from about 7 to about 9, most preferably from about 7 to about 8. As examples of buffer solutions that will provide pH's in these ranges at 25° C may be listed: 50 ml of 0.1 molar potassium dihydrogen phosphate + 5.6 to 46.1 ml 0.1 molar NaOH diluted to 100 ml 50 ml of 0.025 molar borate + 2.0 to 20.5 ml 0.1 molar HCl diluted to 100 ml 50 ml of 0.025 molar borate + 0.9 to 18.3 ml 0.1 molar NaOH diluted to 100 ml 50 ml of 0.05 molar sodium bicarbonate + 5.0 to 10.7 ml 0.1 molar NaOH diluted to 100 ml The precise adjustment of the quantity of acid or base to be used to provide a particular desired pH will be readily determinable by those skilled in the art. If, in a given instance, the use of a biological buffer should be required, one ofthe following may be employed: 3-(N-Morpholino)propanesulfonic acid (MOPS) 3-(N-Morpholino)-2-hydroxypropanesufonic acid (MOPSO) Piperazine-N,N'-bis(2-hydroxypropanesulfonic acid) (POPSO) The reaction between the PAG and the single chain polypeptide will normally be run under conditions that will not give rise to denaturation, e.g. mild temperatures and no more agitation than necessary. The reaction will preferably be run at a temperature in the range of from about 4° C to about 25° C. More preferably, the reaction will be run at room temperature, i.e. from about 20° C to about 25° C. It will be readily understood by those skilled in the art that the amount of PAG employed relative to the amount of single chain polypeptide will be dependent upon the desired nature ofthe reaction product. Where, for example, it is desired to react a PAG with each lysine residue along the polypeptide chain, an amount of PAG at least equimolar to the lysine concentration will be required. It will be advantageous to employ an excess of PAG, where possible, in order to increase the reaction rate and the likelihood of a complete reaction. Clearly, if fewer than all ofthe possible reaction sites along the polypeptide chain are to be derivatized, correspondingly less PAG will be used. In general, however, where molar excesses of PAG's are used, it has been determined that molar excesses on the order of 2 - 100 of the PAG can be used; molar excesses of 2 - 10 are preferred. The time required for the reaction will depend upon a number of factors, such as reaction temperature, concentration of reactants, and whether full or partial reaction is desired. The course of the reaction can be monitored by conventional means, such as the analysis of periodic samples by size exclusion chromatography or gel electrophoresis. The reaction can conveniently be terminated when desired by the addition of a compound having a primary amine group, e.g. glycine, to scavenge the excess PAG. A reaction time of about 15 - 120 minutes will typically be required to fully react the PAG with the primary amine groups of the lysine residues of the single chain polypeptide at room temperature. The skilled practitioner will understand that the time for conjugation, as well as the amount and type of PAG, must not be such as to inactivate the polypeptide being employed. Purification ofthe PAG/single chain polypeptide reaction product can be effected by means commonly employed by those skilled in the art, such as, for example, size exclusion chromatography, ion-exchange chromatography, ultrafiltration, dialysis, and the like. Solutions of the reaction product can, if desired, be concentrated with a rotary evaporator and can be obtained in the dry state by lyophilization. Depending upon the particular single chain antigen binding molecule chosen and the extent to which it is reacted with the PAG, the resulting adduct is expected to be useful both diagnostically and therapeutically, exhibiting, as compared to the unreacted single chain polypeptide, decreased immunogenicity, increased circulating life, and increased stability while maintaining an acceptable level of activity. The single chain antigen binding polypeptide can be reacted with the activated branched polyethylene glycol polymers discussed above in an aqueous reaction medium which can be buffered, depending on the pH requirements ofthe nucleophile. The optimum pH for the reaction is generally between about 6.5 and about 8.0 and preferably about 7.4 for polypeptides. The optimum reaction conditions for the sFv stability, reaction efficiency, etc., is within the level of ordinary skill in the art. The preferred temperature range is between 4°C and 37 °C. The reaction temperature cannot exceed the temperature at which the nucleophile may denature or decompose. It is preferred that the nucleophile be reacted with an excess ofthe activated branched polymer. Following the reaction, the cojugate is recovered and purified, for example, by diafiltration, column chromatography, combinations thereof, or the like. Conjugates Upon production ofthe polyalkylene oxide conjugated sFv (SCA) ofthe present invention, the polyalkylene oxide conjugated sFv may further be modified by conjugating a diagnostic or therapeutic agent to the polyalkylene oxide conjugated sFv. The general method of preparing an antibody conjugate according to the invention is described in Shih, L.B., etal, Cancer Res. 57:4192 (1991); Shih, L.B., and D.M. Goldenberg, Cancer Immunol. Immunother. 37:197 (1990); Shih, L.B., et al, Intl. J. Cancer 46:1101 (1990); Shih, L.B., et al, Intl. J. Cancer 47:832 (1988), all incorporated herein by reference. The indirect method involves reacting an antibody (or sFv), whose polyalkylene oxide has a functional group, with a carrier polymer loaded with one or plurality of bioactive molecules, such as, peptides, lipids, nucleic acids (i.e., phosphate-lysine complexes), drug, toxin, chelator, boron addend or detectable label molecule(s). Alternatively, the polyalkylene oxide conjugated sFv may be directly conjugated with a diagnostic or therapeutic agent. The general procedure is analogous to the indirect method of conjugation except that a diagnostic or therapeutic agent is directly attached to an oxidized sFv component. See Hansen et al, U.S. Patent No. 5,443,953, incorporated herein by reference. The polyalkylene oxide conjugated sFv can be attached to a derivative of the particular drug, toxin, chelator, boron addend or label to be loaded, in an activated form, preferably a carboxyl-activated derivative, prepared by conventional means, e.g., using dicyclohexylcarbodumide (DCC) or a water soluble variant thereof, to form an intermediate adduct. Many drugs and toxins are known which have a cytotoxic effect on tumor cells or microorganisms that may infect a human and cause a lesion, in addition to the specific illustrations given above. They are to be found in compendia of drugs and toxins, such as the Merck Index and the like. Any such drug can be loaded onto a carrier or directly onto a polyalkylene oxide conjugated sFv by conventional means well known in the art, and illustrated by analogy to those described above. Chelators for radiometals or magnetic resonance enhancers are also well known in the art. Typical are derivatives of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTP A). These typically have groups on the side chain by which the chelator can be attached to a carrier or directly onto a polyalkylene oxide conjugated sFv. Such groups include, e.g., a benzylisothiocyanate, by which the DTP A or EDTA can be coupled to the reactive group of an sFv. Labels such as radioisotopes, enzymes, fluorescent compounds, electron transfer agents, and the like can also be linked to carrier or directly onto a polyalkylene oxide conjugated sFv by conventional methods well known to the art. These labels and the sFv conjugates prepared from them can be used for immunoassays and for immunohistology, much as the sFv conjugate prepared by direct attachment ofthe labels to the sFv. However, the loading ofthe conjugates according to the present invention with a plurality of labels can increase the sensitivity of assays or histological procedures, where only low extent of binding ofthe sFv to target antigen is achieved. Boron addends, e.g., carboranes, when attached to single-chain antigen binding molecules and targeted to lesions, can be activated by thermal neutron irradiation and converted to radioactive atoms which decay by alpha emission to produce highly cytotoxic short-range effects. High loading of boron addends, as well as of magnetic resonance enhancing ions, is of great importance in potentiating their effects. Carboranes can be made with carboxyl functions on pendant side chains, as is well known in the art. Loading of drugs on the carrier will depend upon the potency ofthe drug, the efficiency of sFv targeting and the efficacy ofthe conjugate once it reaches its target. In most cases, it is desirable to load at least 20, preferably 50, and often 100 or more molecules of a drug on a carrier. The ability to partially or completely detoxify a drug as a conjugate according to the invention, while it is in circulation, can reduce systemic side effects ofthe drug and permit its use when systemic administration of the unconjugated drug would be unacceptable. Administration of more molecules of the drug, but conjugated to the sFv on a carrier, according to the present invention, permits therapy while mitigating systemic toxicity. Toxins will often be less heavily loaded than drugs, but it will still be advantageous to load at least 5, preferably 10 and in some cases 20 or more molecules of toxin on a carrier and load at least one carrier chain on the sFv for targeted delivery. Uses The polyalkylene oxide conjugated sFv (SCA) polypeptide conjugates of the present invention are expected to have much longer circulating half lifes and reduced immunogenicity in vivo. This may solve a potential limitation relating to very rapid blood clearance of some sFv proteins. It would also reduce or eliminate concerns about repeated administration of a therapeutic sFv which may otherwise provoke an immune response in the patient. The choice of the particular cysteine and/or oligo-lysine mutant combinations may allow one to achieve circulating lives over a considerable range depending on the specific polyalkylene oxide conjugated sFv variant polypeptide. This would allow sFv to be administered for the therapeutic use of choice. A diagnostic or therapeutic agent is a molecule or atom which is conjugated to an antibody and useful for diagnosis or for therapy. The immunoreactivity ofthe antibody is retained. Diagnostic or therapeutic agents include drugs, toxins, chelators, boron compounds and detectable labels. See "Conjugates" section, supra, for further details. The diagnostic or therapeutic agent may be, but is not limited to, at least one selected from a nucleic acid, a compound, a protein, an element, a lipid, an antibody, a saccharide, an isotope, a carbohydrate, an imaging agent, a lipoprotein, a glycoprotein, an enzyme, a detectable probe, or any combination thereof, which may be detectably labeled as for labeling antibodies, as described herein. Such labels include, but are not limited to, enzymatic labels, radioisotope or radioactive compounds or elements, fluorescent compounds or metals, chemiluminescent compounds and bioluminescent compounds. Alternatively, any other known diagnostic or therapeutic agent can be used in a method ofthe present invention. A therapeutic agent used in the present invention may have a therapeutic effect on the target cell, the effect selected from, but not limited to, correcting a defective gene or protein, a drug action, a toxic effect, a growth stimulating effect, a growth inhibiting effect, a metabolic effect, a catabolic affect, an anabolic effect, an antiviral effect, an antibacterial effect, a hormonal effect, a neurohumoral effect, a cell differentiation stimulatory effect, a cell differentiation inhibitory effect, a neuromodulatory effect, an antineoplastic effect, an anti-tumor effect, an insulin stimulating or inhibiting effect, a bone marrow stimulating effect, a pluripotent stem cell stimulating effect, an immune system stimulating effect, and any other known therapeutic effects that may be provided by a therapeutic agent delivered to a cell via a delivery system according to the present invention. The sFv conjugate ofthe present invention may be used for protection, suppression or treatment of infection or disease. By the term "protection" from infection or disease as used herein is intended "prevention," "suppression" or "treatment." "Prevention" involves administration of a glycosylated sFv conjugate prior to the induction ofthe disease. " Suppression" involves administration ofthe composition prior to the clinical appearance ofthe disease. "Treatment" involves administration ofthe protective composition after the appearance of the disease. It will be understood that in human and veterinary medicine, it is not always possible to distinguish between "preventing" and "suppressing" since the ultimate inductive event or events may be unknown, latent, or the patient is not ascertained until well after the occurrence of the event or events. Therefore, it is common to use the term "prophylaxis" as distinct from "treatment" to encompass both "preventing" and "suppressing" as defined herein. The term "protection," as used herein, is meant to include "prophylaxis." Such additional therapeutic agents which can further comprise a therapeutic agent or composition ofthe present invention may be selected from, but are not limited to, known and new compounds and compositions including antibiotics, steroids, cytotoxic agents, vasoactive drugs, antibodies and other therapeutic modalities. Non-limiting examples of such agents include antibiotics used in the treatment of bacterial shock, such as gentamycin, tobramycin, nafcillin, parenteral cephalosporins, etc; adrenal corticosteroids and analogs thereof, such as methyl prednisolone, mitigate the cellular injury caused by endotoxins; vasoactive drugs, such as alpha receptor blocking agent (e.g., phenoxybenzamine), beta receptor agonists (e.g., isoproterenol), and dopamine are agents suitable for treating septic shock. Polyalkylene oxide conjugated sFv ofthe invention may also be used for diagnosis of disease and to monitor therapeutic response. Other uses of polyalkylene oxide conjugated sFv proteins are specific targeting of pro-drug activating enzymes to tumor cells by a bispecific molecule with specificity for tumor cells and enzyme. Polyalkylene oxide conjugated sFv may be used for specific delivery of drug to an in vivo target, such as a tumor, delivery of radioactive metals for tumor radioimmunodiagnosis or radioimmunotherapy (Goldenberg, D.M., Am. J. Med. 94:297 (1993)), nonradioactive metals in applications such as with boron/uranium-neutron capture therapy (Ranadive, G.N., et al, Nucl. Med. Biol. 20:1 (1993); Barth, R.F., et al, Bioconjug Chem. 5:58 (1994)), and nuclear magnetic resonance imaging (Sieving, P.F., etal, Bioconjug. Chem. 1:65 (1990)). This list is illustrative only. The invention also extends to uses for the polyalkylene oxide conjugated sFv proteins in purification and biosensors. Affinity purification is made possible by affixing the polyalkylene oxide conjugated sFv protein to a support, with the antigen-binding sites exposed to and in contact with the ligand molecule to be separated, and thus purified. Biosensors generate a detectable signal upon binding of a specific antigen to an antigen-binding molecule, with subsequent processing of the signal. Polyalkylene oxide conjugated sFv proteins, when used as the antigen-binding molecule in biosensors, may change conformation upon binding, thus generating a signal that may be detected. The invention is also directed to a method of detecting an antigen suspected of being in a sample by contacting the sample with the polyalkylene oxide conjugated sFv that is labeled. A sample may comprise at least one compound, mixture, surface, solution, emulsion, suspension, mixture, cell culture, fermentation culture, cell, tissue, secretion and/or derivative or extract thereof. Such samples can also include, e.g., animal tissues, such as blood, lymph, cerebrospinal fluid (CNS), bone marrow, gastrointestinal contents, and portions, cells or internal and external secretions of skin, heart, lung and respiratory system, liver, spleen, kidney, pancreas, gall bladder, gastrointestinal tract, smooth, skeletal or cardiac muscle, circulatory system, reproductive organs, auditory system, the autonomic and central nervous system, and extracts or cell cultures thereof. Such samples can be measured using methods ofthe present invention in vitro, in vivo and in situ. Such samples can also include environmental samples such as earth, air or water samples, as well as industrial or commercial samples such as compounds, mixtures, surfaces, aqueous chemical solutions, emulsions, suspensions or mixtures. Additionally, samples that can be used in methods ofthe present invention include cell culture and fermentation media used for growth of prokaryotic or eukaryotic cells and or tissues, such as bacteria, yeast, mammalian cells, plant cells and insect cells. Essentially all ofthe uses for which monoclonal or polyclonal antibodies, or fragments thereof, have been envisioned by the prior art, can be addressed by the polyalkylene oxide conjugated sFv proteins ofthe present invention. These uses include detectably-labeled forms ofthe polyalkylene oxide conjugated sFv protein. Types of labels are well-known to those of ordinary skill in the art. They include radiolabeling, chemiluminescent labeling, fluorochromic labeling, and chromophoric labeling. Other uses include imaging the internal structure of an animal (including a human) by administering an effective amount of a labeled form of the polyalkylene oxide conjugated sFv protein and measuring detectable radiation associated with the animal. They also include improved immunoassays, including sandwich immunoassay, competitive immunoassay, and other immunoassays wherein the labeled antibody can be replaced by the PEGylated sFv protein of this invention. See, e.g., Kohler etal, Nature 256:495 (1975); Kohler et al, Eur. J. Immunol. 6:511 (1976); Kohler et al, Eur. J. Immunol. 6:292 (1976); Hammerling et al. , In: Monoclonal Antibodies and T-Cell Hybridomas, pp. 563-681, Elsevier, N (1981); Sambrook et al, Molecular Cloning - A Laboratory Manual, 2nd ed., Cold Spring Harbor Laboratory (1989). Administration Administration of polyalkylene oxide conjugated sFv conjugates ofthe invention for in vivo diagnostic and therapeutic applications will be by analogous methods to sFv where the diagnostic or therapeutic principle is directly linked to the sFv or a loaded earner is linked by random binding to amine or carboxyl groups on amino acid residues ofthe sFv in a non-site-specific manner. Conjugates ofthe present invention (immunoconjugates) can be formulated according to known methods to prepare pharmaceutically useful compositions, such as by admixture with a pharmaceutically acceptable carrier vehicle. Suitable vehicles and their formulation are described, for example, in Remington 's Pharmaceutical Sciences, 18th ed., Osol, A., ed., Mack, Easton PA (1990). In order to form a pharmaceutically acceptable composition suitable for effective administration, such compositions will contain a therapeutically effective amount ofthe immunoconjugate, either alone, or with a suitable amount of canier vehicle. Additional pharmaceutical methods may be employed to control the duration of action. Controlled release preparations may be achieved by the use of polymers to complex or absorb the immunoconjugate of the present invention. The controlled delivery may be exercised by selecting appropriate macromolecules (for example, polyesters, polyamino acids, polyvinyl pynolidone, ethylene- vinylacetate, methylcellulose, carboxymethylcellulose, or protamine sulfate). The rate of drug release may also be controlled by altering the concentration of such macromolecules. Another possible method for controlling the duration of action comprises incorporating the therapeutic agents into particles of a polymeric substance such as polyesters, polyamino acids, hydrogels, poly(lactic acid) or ethylene vinylacetate copolymers. Alternatively, it is possible to entrap the immunoconjugate ofthe invention in microcapsules prepared, for example, by coacervation techniques or by interfacial polymerization, for example, by the use of hydroxymethylcellulose or gelatin-microcapsules or poly(methylmethacrylate) microcapsules, respectively, or in a colloid drug delivery system, for example, liposomes, albumin microspheres, microemulsions, nanoparticles, nanocapsules, or in macroemulsions. Such teachings are disclosed in Remington's Pharmaceutical Sciences, 16th ed., Osol, A., ed., Mack, Easton PA (1990). The immunoconjugate may be provided to a patient by means well known in the art. Such means of introduction include oral means, intranasal means, subcutaneous means, intramuscular means, intravenous means, intra-arterial means, or parenteral means. Intravenous, intraarterial or intrapleural administration is normally used for lung, breast, and leukemic tumors. Intraperitoneal administration is advised for ovarian tumors. Intrathecal administration is advised for brain tumors and leukemia. Subcutaneous administration is advised for Hodgkin's disease, lymphoma and breast carcinoma. Catheter perfusion is useful for metastatic lung, breast or germ cell carcinomas of the liver. Intralesional administration is useful for lung and breast lesions. For therapeutic or diagnostic applications, compositions according to the invention may be administered parenterally in combination with conventional injectable liquid earners such as sterile pyrogen-free water, sterile peroxide-free ethyl oleate, dehydrated alcohol, or propylene glycol. Conventional pharmaceutical adjuvants for injection solution such as stabilizing agent, solubilizing agents and buffers, such as ethanol, complex forming agents such as ethylene diamine tetraacetic acid, tartrate and citrate buffers, and high-molecular weight polymers such as polyethylene oxide for viscosity regulation may be added. Such compositions may be injected intramuscularly, intraperitoneally, or intravenously. Further non-limiting examples of carriers and diluents include albumin and/or other plasma protein components such as low density lipoproteins, high density lipoproteins and the lipids with which these serum proteins are associated. These lipids include phosphatidyl choline, phosphatidyl serine, phosphatidyl ethanolamine and neutral lipids such as triglycerides. Lipid carriers also include, without limitation, tocopherol. At least one polyalkylene oxide conjugated sFv linked to a therapeutic agent according to the invention may be administered by any means that achieve their intended purpose, for example, to treat various pathologies, such as cell inflammatory, allergy, tissue damage or other related pathologies. A typical regimen for preventing, suppressing, or treating various pathologies comprises administration of an effective amount of an sFv conjugate, administered over a period of one or several days, up to and including between one week and about 24 months. It is understood that the dosage ofthe present invention administered in vivo or in vitro will be dependent upon the age, sex, health, and weight of the recipient, kind of concurrent treatment, if any, frequency of treatment, and the nature ofthe effect desired. The ranges of effective doses provided below are not intended to limit the invention and represent prefened dose ranges. However, the most preferred dosage will be tailored to the individual subject, as is understood and determinable by one of skill in the art, without undue experimentation. See, e.g., Berkow et al, eds., Merck Manual, 16th edition, Merck and Co., Rahway, N.J. (1992); Goodman etal, eds., Goodman andGilman's The Pharmacological Basis of Therapeutics, 8th edition, Pergamon Press, Inc., Elmsford, N. Y. ( 1990); Avery's Drug Treatment: Principles and Practice of Clinical Pharmacology and Therapeutics, 3rd edition, ADIS Press, LTD., Williams and Wilkins, Baltimore, MD. (1987), Ebadi, Pharmacology, Little, Brown and Co., Boston (1985), Katzung, Basic and Clinical Phamacology, Appleton and Lange, Norwalk, Conn. (1992), which references and references cited therein, are entirely incorporated herein by reference. The total dose required for each treatment may be administered by multiple doses or in a single dose. Effective amounts of a diagnostic/pharmaceutical compound or composition ofthe present invention are from about 0.001 μg to about 100 mg/kg body weight, administered at intervals of 4-72 hours, for a period of 2 hours to 5 years, or any range or value therein, such as 0.01-1.0, 1.0- 10, 10-50 and 50-100 mg/kg, at intervals of 1-4, 6-12, 12-24 and 24-72 hours, for a period of 0.5, 1.0-2.0, 2.0-4.0 and 4.0-7.0 days, or 1, 1-2, 2-4, 4-52 or more weeks, or 1, 2, 3-10, 10-20, 20-60 or more years, or any range or value therein. Preparations for parenteral administration include sterile aqueous or non-aqueous solutions, suspensions, and emulsions, which may contain auxiliary agents or excipients which are known in the art. Pharmaceutical compositions such as tablets and capsules can also be prepared according to routine methods. See, e.g., Berker, supra, Goodman, supra, Avery, supra and Ebadi, supra, which are entirely incorporated herein by reference, including all references cited therein. Pharmaceutical compositions comprising at least one type of sFv conjugate of the invention, or, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 types of sFv conjugates, ofthe present invention may be contained in an amount effective to achieve its intended purpose. In addition to at least one sFv conjugate, a pharmaceutical composition may contain suitable pharmaceutically acceptable earners, such as excipients, earners and/or auxiliaries which facilitate processing ofthe active compounds into preparations which can be used pharmaceutically. Pharmaceutical compositions may also include suitable solutions for administration intravenously, subcutaneously, dermally, orally, mucosally or rectally, and contain from about 0.01 to 99 percent, preferably from about 20 to 75 percent of active component (i.e., the sFv) together with the excipient. Pharmaceutical compositions for oral administration include tablets and capsules. Compositions which can be administered rectally include suppositories. See, e.g., Berker, supra, Goodman, supra, Avery, supra and Ebadi, supra. Additional lipid and lipoprotein drug delivery systems that may be included herein are described more fully in Annals NY. Acad. Sci. 507:775-88, 98-103, and 252-271, which disclosure is hereby incorporated by reference. The compositions may also be formulated into orally administrable compositions containing one or more physiologically compatible earners or excipients, and may be solid or liquid in form. These compositions may, if desired, contain conventional ingredients such as binding agents, for example, syrups, acacia, gelatin, sorbitol, tragacanth, or polyvinylpynolidone; fillers, such as lactose, mannitol, starch, calcium phosphate, sorbitol, cyclodextran, or methylcellulose; lubricants such as magnesium stearate, high molecular weight polymers such as polyethylene glycols, high molecular weight fatty acids such as stearic acid or silica; disintegrants such as starch; acceptable wetting agents as, for example, sodium lauryl sulfate. The oral compositions may assume any convenient form, such as tablets, capsules, lozenges, aqueous or oily suspensions, emulsions, or dry products suitable for reconstitution with water or other liquid medium prior to use. The liquid oral forms may, of course, contain flavors, sweeteners, preservatives such as methyl or propyl p-hydroxybenzoates; suspending agents such as sorbitol, glucose or other sugar syrup, methyl, hydroxymethyl, or carboxymethyl celluloses or gelatin; emulsifying agents such as lecithin or sorbitan monooleate or thickening agents. Non-aqueous compositions may also be formulated which comprise edible oils as, for example, fish-liver or vegetable oils. These liquid compositions may conveniently be encapsulated in, for example, gelatin capsules in a unit dosage amount. The pharmaceutical compositions according to the present invention may also be administered, if appropriate, either topically as an aerosol or, formulated with conventional bases as a cream or ointment. The pharmaceutical compositions of the present invention can also be administered by incorporating the active ingredient into colloidal earners, such as liposomes. Liposome technology is well known in the art, having been described by Allison et al, Nature 252:252-254 (1974), and Dancy et al, J. Immunol. 720:1109-1113 (1978). Having now generally described this invention, the same will be better understood by reference to certain specific examples, which are included for the purpose of illustration and not intended to be limiting unless otherwise specified. Examples Example 1 Preparation of Methoxypoly(ethylene glycolj-succinimidyl carbonate (SC-PEG) Dissolve 60 g of methoxy poly(ethylene glycol) (MW 5,000) in 200 ml of 3/1 toluene/dichloromethane and treat with atoluene solution of phosgene (30 ml, 57 mmol) overnight. Evaporate the solution to dryness and remove the remainder of the phosgene under vacuum. Redissolve the residue in 150 ml of 2/1 toluene/dichloromethane. Treat the resulting solution with 2.1 g (18 mmol) of solid N-hydroxysuccinimide, followed by 1.7 ml (12 mmol) of triethylamine. Allow the solution to stand for three hours and then filter it and evaporate it to dryness. Dissolve the residue in 600 ml of warm (50° C) ethyl acetate, filter the solution, and cool it to facilitate precipitation ofthe polymer. Collect the product by filtration, then recrystallize from ethyl acetate, and dry under vacuum over P 2 O 5 . Example 2 Preparation ofCC 49/212 SCA In the production of monovalent or multivalent antigen-binding proteins, the same recombinant E. coli production system that was used for prior single- chain antigen-binding protein production was used. See Bird et al, Science 242:423 (1988). This production system produced between 2 and 20% of the total E. coli protein as single-chain antigen-binding protein. For protein recovery, the frozen cell paste from three 10-liter fermentations (600-900 g) was thawed overnight at 4°C and gently resuspended at 4°C in 50 mM Tris-HCl, 1.0 mM EDTA, 100 mM KC1, 0.1 mM PMSF, pH 8.0 (lysis buffer), using 10 liters of lysis buffer for every kilogram of wet cell paste. When thoroughly resuspended, the chilled mixture was passed three times through a Manton-Gaulin cell homogenizer to totally lyse the cells. Because the cell homogenizer raised the temperature of the cell lysate to 25 ± 5°C, the cell lysate was cooled to 5 + 2°C with a Lauda/Brinkman chilling coil after each pass. Complete lysis was verified by visual inspection under a microscope. The cell lysate was centrifuged at 24,300g for 30 minutes at 6°C using a Sorvall RC-5B centrifuge. The pellet containing the insoluble single-chain antigen-binding protein was retained, and the supernatant was discarded. The pellet was washed by gently scraping it from the centrifuge bottles and resuspending it in 5 liters of lysis buffer/kg of wet cell paste. The resulting 3.0- to 4.5-liter suspension was again centrifuged at 24,300g for 30 minutes at 6°C, and the supernatant was discarded. This washing ofthe pellet removes soluble E. coli proteins and can be repeated as many as five times. At any time during this washing procedure the material can be stored as a frozen pellet at -20°C. A substantial time saving in the washing steps can be accomplished by utilizing a Pellicon tangential flow apparatus equipped with 0.22-μm microporous filters, in place of centrifugation. The washed pellet was solubilized at 4°C in freshly prepared 6 M guanidine hydrochloride, 50 mM Tris-HCl, 10 mM CaCl 2 , 50 mM KC1, pH 8.0 (dissociating buffer), using 9 ml/g of pellet. If necessary, a few quick pulses from a Heat Systems Ultrasonics tissue homogenizer can be used to complete the solubilization. The resulting suspension was centrifuged at 24,3 OOg for 45 minutes at 6°C and the pellet was discarded. The optical density of the supernatant was determined at 280 nm and if the OD 280 was above 30, additional dissociating buffer was added to obtain an OD 280 of approximately 25. The supernatant was slowly diluted into cold (4-7°C) refolding buffer (50 mM Tris-HCl, 10 mM CaCl 2 , 50 mM KC1, pH 8.0) until a 1 :10 dilution was reached (final volume 10 - 20 liters). Re-folding occurs over approximately eighteen hours under these conditions. The best results are obtained when the GuHCl extract is slowly added to the refolding buffer over a two hour period, with gentle mixing. The solution was filtered through a 0.2 μm Millipore Millipak 200. This filtration step may be optionally preceded by a centrifugation step. The filtrate was concentrated to 1 to 2 liters using an Amicon spiral cartridge with 10,000 MWCO cartridge, again at 4°C. The concentrated crude antigen-binding protein sample was dialyzed against Buffer G (60 mM MOPS, 0.5 mM Ca acetate, pH 6.0 - 6.4) until the conductivity was lowered to that of Buffer G. The sample was then loaded on a 21.5 x 250-mm polyaspartic acid PolyCAT A column, manufactured by Poly LC of Columbia, Maryland. If more than 60 mg of protein is loaded on this column, the resolution begins to deteriorate; thus, the concentrated crude sample often must be divided into several PolyCAT A runs. Most antigen-binding proteins have an extinction coefficient of about 2.0 ml mg^cm "1 at 280 nm and this can be used to determine protein concentration. The antigen-binding protein sample was eluted from the PolyCAT A column with a 50-min linear gradient from Buffer G to Buffer H (60 mM MOPS, 20 mM Ca Acetate, pH 7.5 - 8.0). Most of the single-chain proteins elute between 20 and 26 minutes when this gradient is used. This conesponds to an eluting solvent composition of approximately 70% Buffer G and 30% Buffer H. Most ofthe bivalent antigen-binding proteins elute later than 45 minutes, which conespond to over 90% Buffer H. Example 3 Modification of CC 49212 Single Chain Antigen Binding Molecule With SC-PEG A sample of CC 49/212 single chain antigen binding molecule (MW=27000) dissolved in KPO 4 /NaCl buffer (pH 7.2) was obtained as described in Example 2. The protein was found to be pure using SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and size exclusion chromatography. The concentration of the protein was 0.79 mg/ml. It was further concentrated to at least 2 mg/ml using an Amicon concentrator with a 10,000 dalton nominal size cut-off, i.e., anything greater than 10K is retained. The modification reaction, i.e., the coupling of the SC-PEG to the CC 49/212, was canied out in 50 mM KPO 4 , 150 mM NaCl buffer, which was the storage buffer the protein was supplied in. The pH was raised from 7.2 to 7.5. SC-PEG (MW 5,000) was added in a 50x molar excess to protein. At specific time intervals, the coupling reaction was terminated by the addition of a 5 Ox molar excess of glycine and the extent and progress of the coupling reaction was checked as a function of time using both size exclusion chromatography using a DuPont Zorbax 250 column and SDS-PAGE. Free SC-PEG remaining in the samples was removed by extensive dialysis on an Amicon Centricon 10. The samples were checked for degree of modification by size exclusion chromatography. After concentrating the samples, the residual amine concentration on the protein was determined by titration with trinitrobenzene sulfonate and the percentage of amine groups that had reacted with the SC-PEG (the "% modification") was calculated from the results. Dansyl derivatives of native single chain antigen binding molecule (CC 49/212) and hemoglobin, PEG SCA and hemoglobin, and N-acetyl lysine were prepared. These samples were then analyzed for amino acid. The results of this experiment are shown in Table 3. Example 4 Competition ELISA The CC49 monoclonal antibody was developed by Dr. Jeffrey Schlom's group, Laboratory of Tumor Immunology and Biology, National Cancer Institute. It binds specifically to the pan-carcinoma tumor antigen TAG-72. See Muraro, R. et al, Cancer Research 48: 4588-4596 (1988). Figure 1 is a graphical representation of three competition ELISA's in which unlabeled PEG modified CC49/212 single-chain Fv (closed squares), CC49/212 single-chain Fv (open squares), CC49 IgG (open circles), and MOPC- 21 IgG (+) competed against a CC49 IgG radiolabeled with 125 I for binding to the TAG-72 antigen on a human breast melanoma extract. MOPC-21 is a control antibody that does not bind to TAG-72 antigen. In this experiment, 50% competition of 125 I-CC49 IgG binding required about 200 nM of CC49 IgG, about 550 nM of CC49/212 sFv, and about 3000 nM of PEG modified CC49/212 sFv. Example 5 Preparation of U-PEG-OH Materials Methoxypolyethylene glycol) (m-PEG) was obtained from Union Carbide. The solvents were obtained from Aldrich Chemical of Milwaukee, Wisconsin. The methoxypoly(ethylene glycol)-N-succinimidyl carbonate (SC-PEG) was prepared as described in U.S. Patent No. 5,122,614, using m-PEG having a molecular weight of about 5,000. Each of the products prepared in Examples 5-10 was confirmed structurally by carbon- 13 NMR. The branched polymer, U-PEG-OH, was prepared by adding 100 mg ( 1.1 mmol) of 1 ,3-diamino-2-propanol to a solution of 10.0 g (2 mmol) of SC-PEG in 50 mL of methylene chloride. The mixture was stined for 18 hours at room temperature then filtered. Excess solvent was removed by distillation in vacuo. The residue was recrystallized from 2-propanol to yield 7.1 g of product (70% yield). Example 6 Preparation of U-PNP-PEG The compound of Example 5 was activated with p-nitrophenyl chloroformate. First, 5.0g (0.5 mmol) of U-PEG-OH was azeotropically dried by refluxing in 75 mL of toluene for 2 hours, resulting in the removal of 25 mL of solvent water. The reaction mixture was cooled to 30 ° C, followed by the addition of 120 mg (0.6 mmol) of p-nitrophenyl chloroformate and 50 mg (0.6 mmol) of pyridine. The resulting mixture was stirred for two hours at 45 °C, followed by stining overnight at room temperature. The reaction mixture was then filtered through CELITE™ , followed by removal ofthe solvent from the filtrate by distillation in vacuo. The residue was recrystallized from 2-propanol to yield 4.2 g (81% yield) ofthe product. Example 7 Preparation of US-PEG In this example, the U-PNP-PEG of Example 6 was reacted with N-hydroxysuccinimide to form the succinimidyl carbonate ester of U-PEG. A solution containing 5.0 g (0.5 mmol) of the U-PNP-PEG, 0.6 g (5 mmol) of N-hydroxysuccinimide and 0.13 g (1 mmol) of diisopropylethylamine in 40 ml of methylene chloride was refluxed for 18 hours. The solvent was then removed by distillation in vacuo, and the residue was recrystallized from 2-propanol to yield 4.2 g ofthe succinimidyl carbonate ester (82% yield). Example 8 Preparation of XU-PEG-OH This branched polymer was prepared by reacting the U-PNP-PEG of Example 6 with 2-(2-aminoethoxy) ethanol (i.e., the amino alcohol was reacted with the p-nitrophenyl carbonate). The recrystallized product yield was 86%. Example 9 Preparation of XU-PNP-PEG The compound of Example 8 was functionalized with p-nitrophenyl carbonate as in Example 6. The recrystallized product yield was 83%. Example 10 Preparation of XUS-PEG In this example, the succinimidyl carbonate derivative of compound prepared in Example 8 was prepared according to the process described in Example 7, by reacting N-hydroxysuccinimide with the p-nitrophenyl carbonate derivative of Example 9. The recovered product yield was 84%. Example 11 Modification ofCC49/218 with SC-PEG or XUS-PEG A sample containing CC49/218 was desalted on a PD-10 column in a buffer consisting of 0.1 M sodium phosphate, pH 8.0. An equimolar amount of SC-PEG or XUS-PEG was added and the reactions were incubated at 4°C, overnight. The reactions were quenched with an excess of glycine. The modified CC49/218 conjugates were GPC purified and then concentrated in a centricon- 10. The yield based on GPC integration was about 50% for SC-PEG modified CC49/218 and about 40% for XUS-PEG modified CC49/218. The GPC profiles were almost identical to those obtained when the reaction was performed at pH9.0, room temperature. SDS-PAGE revealed that the appropriate derivatives had been made. Example 12 Competition ELISA The assay was performed as in Example 4 above using SC-PEG modified CC49/218 and XUS-PEG modified CC49/218 along with the appropriate controls. The results are shown in Figure 4 and in Table 4 below. Thus, the affinity ofthe SC-PEG modified CC49-SCA was within about 8 to 10 fold of the native CC49-SCA and the affinity the XUS-PEG modified CC49-SCA was within about 4 to 5 fold ofthe native CC49-SCA. Samples #049304 and #049303 were PEG modified, whiles samples #04901 and #049302 were unmodified CC49/218 isolated from the reaction mixtures. Example 13 Pharmacokinetics of Plasma Retention ofsFv and PEG-sFv Sixty μg of CC49/218 sFv protein or 60 μg of PEG-modified sFv protein were injected intravenously at time 0 into ICR (CD- 1 ) female mice (Harlan - 25g, 7-8 weeks old). Mice were bled at the time points indicated in Figure 5. The percent retention in plasma was quantitated by ELISA methods. For the PEG- modified conjugate, CC49/218 sFv was conjugated to SC-PEG of molecular mass 20,000 (the protocol is described in U.S. Patent 5,122,614, which disclosure is incorporated herein by reference). The average PEG:sFv molar ratio in the tested PEG-sFv conjugate was approximately 1 :1. Example 14 PEGylated Multimer Single Chain Antibodies Using bifunctional PEG, dimers and trimers of CC49-SCA have been made. CC49-SCA was modified with bifunctional PEG as follows: 2 ml of CC49- SCA in phosphate buffered saline (25 mM sodium phosphate, pH 7.3, 0.15 M NaCl) at a concentration of 1.5 mg/ml was modified as follows. Bifunctional PEG (polyethylene glycol with reactive SC at both terminal ends), 1.887 mg (powder) was dissolved in 0.1 ml of MOPS (3-[N-mo holino]propane)-sulfonic acid) buffered at pH 7.3. This PEG solution was added to CC49-SCA solution within 10 seconds of dissolution. The mixture was then stined at 24° C for 1 hour. At the end ofthe reaction, solid Guanidine HCl was added to the reaction mixture to a final concentration of 6 M in order to break up non covalently associated CC49- SCA. This material was immediately applied to a size exclusion column (2 cm X 60 cm, Superdex-75) previously equilibrated in the buffer composed of 60 mM Guanidine HCl in 50 mM Tris pH 7.3, lmMCaCl 2 , 0.1 mM PMSF (phenyl methyl sulfonyl flouride), and 50 mM KC1. Multimers of different molecular weights were then fractionated from the column. These multimers are CC49-SCA separated by a long stretch of PEG (5000 MW, about 226 carbons in length) and were freshly refolded and thus, are not believed to arise from aggregation. It is less likely that there was diabody or multivalent SCA formed as a result of self association ofthe CC49-SC A. Further evidence was demonstrated by the fact that there was negligible native CC49-SC A in the denaturing SDS-PAGE profile. The SDS-PAGE electrophoresis patterns for dimeric CC49-SCA, trimeric CC49-SCA, PEG-CC49-SCA and native CC49-SCA under reducing conditions are shown in Figure 6. The multimers were assayed for binding affinity using the following assay which was modified method described in B Friquet et al. J. of Immunology Methods, 77:305-319(1985). Briefly, various amounts of a given modified single chain antibody were mixed with various amounts of the antigen mucin in PBS (phosphate buffered saline). The binding reaction was allowed to reach equilibration for at least 24 hours at 4°C. At the end of the incubation, the unbound CC49-SCA fractions were assayed by ELISA, while the bound fractions were washed away. The total amount of free CC49-SCA was determined by the ELISA using the CC49-SCA sample pre-incubated in the absence ofthe antigen mucin. The bound antibody was determined by subtraction ofthe free (unbound) amount from the total amount as determined by ELISA. Since the total amount ofthe CC49-SCA was known, it was also used as its own standard curve. Note that each type of CC49-SCA had its own reference control. In essence, the protocol was measuring the unbound amount of a particular version of PEG- CC49-SC A as a result ofthe binding to the antigen. Although PEG may affect the detection reagent in ELISA, this was well contained in the standard references. Therefore, the amount measured was not due to the difference of various PEG on the various versions of PEG-CC49-SCA. In sum, in this study, increasing concentrations ofthe CC49-SCA protein were allowed to bind to a fixed amount ofthe antigen. The amount that binds to 50% ofthe maximal level is a good indication ofthe affinity. This data indicate that the affinity of PEG-Di-CC49-SCA and PEG-Tri-CC49-SC A are very similar to that of native CC49-SCA. However, the PEG-modified CC49-SCA monomer had much lower affinity. The binding data are shown in Figure 7. Example 15 Pharmacokinetics ofPEG-CC49-SCA The pharmacokinetic study of various forms of PEG-CC49-SCA was performed as in Example 13, above. The data obtained from this study indicate the following: There was a trend toward longer circulation half-lives as the size ofthe PEG increases. As more PEG is attached to the protein, the circulation time increases. However, attachment of a few strands of high molecular weight PEG gives a better increase in circulation half-life than multiple stands of lower molecular weight PEG. The circulation half-life of CC49-SCA-U-PEG, made with the US-PEG prepared in Example 7, was about the same as that of CC49-SCA-PEG- 12000. Therefore, the shape ofthe PEG does not affect the circulation half-life. Whether the linker is an SC-bond, Flan-bond, hydrazine bond, or TPC, there was no significant change in the circulation half-life. Therefore, the chemical bonds of the linkers, if not releasable, do not affect the circulation half-life. In addition, the PEG remains attached to the protein during the observable time. The circulation half-life was shortened by carbohydrate. However, if PEG was attached to the carbohydrate, it increases the circulation by about 10 fold. This was not better, however, than attaching an equivalent number of PEG at other sites on CC49-SCA. The results ofthe study are shown in the table below: NOTES: A. The PK modeling was following a one-compartment, i.v.-bolus model. B. The observed vs. predicted correlations are over 95%. C. The circulatory half-life is the time for the drug concentration in the serum to reduce to one half after equilibration is reached (about 2 min.) D. AUC = area under the curve, is the integral ofthe drug blood level over time from zero to last measurement, and is a measure of quantity of drug absorbed and in the body. E. Mean residence time is the average amount of time a drug remains in the compartment. F. The code for linkers are: SC = Succinimidyl Carbonate NHS = N-hydroxy succinimide Hz = Hydrazide TPC = trichlorophenyl carbonate Flan = Thiazolidine thione ester U = SC in the middle of PEG The Flan-bond PEG was prepared as taught in U.S. Patent 5,405,877. Example 16 Competition Binding Assay A competition binding assay of biotinylated CC49-SCA with various PEGylated CC49-SCA proteins was performed using an ELISA ofthe biotinylated CC49-SCA as detected by horseradish-peroxidase conjugated with streptoavidin (SAV-HRP). In the assay, the biotinylated CC49-SCA and PEG-CC49-SCA sample were mixed at various ratios for competition of binding to the antigen mucin on a surface. The amount of biotinylated-CC49-SCA bound to antigen was then measured by SAV-HRP, which would not detect the PEG-modified CC49- SCA. The reduction of binding of biotinylated CC49-SCA due to competition of PEG-CC49-SCA is a reflection ofthe relative affinity ofthe two forms of CC49- SCA for the antigen. The level of PEG-CC49-SCA that caused reduction of biotin-CC49-SCA to half of its maximum binding level (IC50) was used in the Cheng-Prussoff formula for determination ofthe affinity constant Kd as follows: Assuming the biotin-CC49-SC A level is [s] and its affinity is known as Ks, then the affinity for the PEG-CC49-SCA is Kd = IC50/(1 + [s]/Ks). Note that PEG- CC49-SCA was not directly measured and that PEG had no effect on biotin binding because it was on a different molecule. The estimated Kd was then expressed as a percentage ofthe control (CC49-SCA). The affinity ranking obtained was as follows: CC49 = SC2 > GC = Bio.CC49 = CC12 > C20 = F5 >HZ >PG where SC2 is PEG SC2000-CC49-SCA; GC is glyco-CC49-SCA; Bio.CC49-SCA is the biotinylated CC49-SCA; CC12 is the PEG-SC12,000-CC49-SCA; F5 is PEG-Flan-5000-CC49-SC A; HZ is CC49-SC A highly PEGylated on the carboxyl groups with MW 5000 hydrazine-PEG; PG is PEG-glyco-CC49-SCA and is highly PEGylated on the carbohydrate with MW 5000 hydrazine PEG; and C20 is PEG-SC20000-CC49-SC A. The affinity for all the PEG-modified CC49-SCAs shown in Figure 8, were within about two fold ofthe native CC49-SCA. Taken together with the data in Example 15 (see, the table), the results indicate that when the SCA is modified with a lower number of PEG molecules, the resulting affinity ofthe SCA is better than when the SCA is modified with a higher number of PEG molecules. Although the foregoing refers to particular prefened embodiments, it will be understood that the present invention is not so limited. It will occur to those skilled in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the present invention. SEQUENCE LISTING (1) GENERAL INFORMATION: (i) APPLICANT: ENZON, INC. 20 KINGSBRIDGE ROAD PISCATAWAY, NJ 08854-3963 UNITED STATES OF AMERICA APPLICANTS/INVENTORS: WHITLOW, MARC SHORR, ROBERT G.L. FILPULA, DAVID R. LEE, LIHSYNG S. (ii) TITLE OF INVENTION: POLYALKYLENE OXIDE-MODIFIED SINGLE CHAIN POLYPEPTIDES (iii) NUMBER OF SEQUENCES: 4 (iv) CORRESPONDENCE ADDRESS: (A) ADDRESSEE: STERNE, KESSLER, GOLDSTEIN & FOX P.L.L.C. (B) STREET: 1100 NEW YORK AVENUE, SUITE 600 (C) CITY: WASHINGTON (D) STATE: DC (E) COUNTRY: USA (F) ZIP: 20005 (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 #1.30 (vi) CURRENT APPLICATION DATA: (A) APPLICATION NUMBER: To be assigned (B) FILING DATE: Herewith (C) CLASSIFICATION: (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 60/044,449 (B) FILING DATE: 30-APR-1997 (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 60/050,472 (B) FILING DATE: 23-JUN-1997 (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 60/063,074 (B) FILING DATE: 27-OCT-1997 (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 60/067,341 (B) FILING DATE: 02-DEC-1997 (viii) ATTORNEY/AGENT INFORMATION: (A) NAME: JORGE A. GOLDSTEIN (B) REGISTRATION NUMBER: 29,021 (C) REFERENCE/DOCKET NUMBER: 0977.184PC02 (ix) TELECOMMUNICATION INFORMATION: (A) TELEPHONE: 202-371-2600 (B) TELEFAX: 202-371-2540 (2) INFORMATION FOR SEQ ID NO : 1 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 749 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: both (ii) MOLECULE TYPE: cDNA (ix) FEATURE: (A) NAME/KEY: CDS (B) LOCATION: 1..73. (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 1 : GAC GTC GTG ATG TCA CAG TCT CCA TCC TCC CTA CCT GTG TCA GTT GGC 48 Asp Val Val Met Ser Gin Ser Pro Ser Ser Leu Pro Val Ser Val Gly 1 5 10 15 GAG AAG GTT ACT TTG AGC TGC AAG TCC AGT CAG AGC CTT TTA TAT AGT 96 Glu Lys Val Thr Leu Ser Cys Lys Ser Ser Gin Ser Leu Leu Tyr Ser 20 25 30 GGT AAT CAA AAG AAC TAC TTG GCC TGG TAC CAG CAG AAA CCA GGG CAG 144 Gly Asn Gin Lys Asn Tyr Leu Ala Trp Tyr Gin Gin Lys Pro Gly Gin 35 40 45 TCT CCT AAA CTG CTG ATT TAC TGG GCA TCC GCT AGG GAA TCT GGG GTC 192 Ser Pro Lys Leu Leu lie Tyr Trp Ala Ser Ala Arg Glu Ser Gly Val 50 55 60 CCT GAT CGC TTC ACA GGC AGT GGA TCT GGG ACA GAT TTC ACT CTC TCC 240 Pro Asp Arg Phe Thr Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Ser 65 70 75 80 ATC AGC TGT GTG AAG ACT GAA GAC CTG GCA GTT TAT TAC TGT CAG CAG 288 lie Ser Cys Val Lys Thr Glu Asp Leu Ala Val Tyr Tyr Cys Gin Gin 85 90 95 TAT TAT AGC TAT CCC CTC ACG TTC GGT GCT GGG ACC AAG CTT GTG CTG 336 Tyr Tyr Ser Tyr Pro Leu Thr Phe Gly Ala Gly Thr Lys Leu Val Leu 100 105 110 AAA GGC TCT TGT TCC GGT AGC GGC AAA CCC GGG AGT GGT GAA GGT AGC 384 Lys Gly Ser Cys Ser Gly Ser Gly Lys Pro Gly Ser Gly Glu Gly Ser 115 120 125 ACT AAA GGT CAG GTT CAG CTG CAG CAG TCT GAC GCT GAG TTG GTG AAA 432 Thr Lys Gly Gin Val Gin Leu Gin Gin Ser Asp Ala Glu Leu Val Lys 130 135 140 CCT GGG GCT TCA GTG AAG ATT TCC TGC AAG GCT TCT GGC TAC ACC TTC 480 Pro Gly Ala Ser Val Lys lie Ser Cys Lys Ala Ser Gly Tyr Thr Phe 145 150 155 160 ACT GAC CAT GCA ATT CAC TGG GTG AAA CAG AAC CCT GAA CAG GGC CTG 528 Thr Asp His Ala lie His Trp Val Lys Gin Asn Pro Glu Gin Gly Leu 165 170 175 GAA TGG ATT GGA TAT TTT TCT CCC GGA AAT GAT GAT TTT AAA TAC AAT 576 Glu Trp lie Gly Tyr Phe Ser Pro Gly Asn Asp Asp Phe Lys Tyr Asn 180 185 190 GAG AGG TTC AAG GGC AAG GCC ACA CTG ACT GCA GAC AAA TCC TCC AGC 624 Glu Arg Phe Lys Gly Lys Ala Thr Leu Thr Ala Asp Lys Ser Ser Ser 195 200 205 ACT GCC TAC GTG CAG CTC AAC TGC CTG ACA TCT GAG GAT TCT GCA GTG 672 Thr Ala Tyr Val Gin Leu Asn Cys Leu Thr Ser Glu Asp Ser Ala Val 210 215 220 TAT TTC TGT ACA AGA TCC CTG AAT ATG GCC TAC TGG GGT CAA GGA ACC 720 Tyr Phe Cys Thr Arg Ser Leu Asn Met Ala Tyr Trp Gly Gin Gly Thr 225 230 235 240 TCA GTC ACC GTC TCC TGC TAATAGGATC C 749 Ser Val Thr Val Ser Cys 245 (2) INFORMATION FOR SEQ ID NO : 2 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 246 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 2 : Asp Val Val Met Ser Gin Ser Pro Ser Ser Leu Pro Val Ser Val Gly 1 5 10 15 Glu Lys Val Thr Leu Ser Cys Lys Ser Ser Gin Ser Leu Leu Tyr Ser 20 25 30 Gly Asn Gin Lys Asn Tyr Leu Ala Trp Tyr Gin Gin Lys Pro Gly Gin 35 40 45 Ser Pro Lys Leu Leu lie Tyr Trp Ala Ser Ala Arg Glu Ser Gly Val 50 55 60 Pro Asp Arg Phe Thr Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Ser 65 70 75 80 lie Ser Cys Val Lys Thr Glu Asp Leu Ala Val Tyr Tyr Cys Gin Gin 85 90 95 Tyr Tyr Ser Tyr Pro Leu Thr Phe Gly Ala Gly Thr Lys Leu Val Leu 100 105 110 Lys Gly Ser Cys Ser Gly Ser Gly Lys Pro Gly Ser Gly Glu Gly Ser 115 120 125 Thr Lys Gly Gin Val Gin Leu Gin Gin Ser Asp Ala Glu Leu Val Lys 130 135 140 Pro Gly Ala Ser Val Lys lie Ser Cys Lys Ala Ser Gly Tyr Thr Phe 145 150 155 160 Thr Asp His Ala lie His Trp Val Lys Gin Asn Pro Glu Gin Gly Leu 165 170 175 Glu Trp lie Gly Tyr Phe Ser Pro Gly Asn Asp Asp Phe Lys Tyr Asn 180 185 190 Glu Arg Phe Lys Gly Lys Ala Thr Leu Thr Ala Asp Lys Ser Ser Ser 195 200 205 Thr Ala Tyr Val Gin Leu Asn Cys Leu Thr Ser Glu Asp Ser Ala Val 210 215 220 Tyr Phe Cys Thr Arg Ser Leu Asn Met Ala Tyr Trp Gly Gin Gly Thr 225 230 235 240 Ser Val Thr Val Ser Cys 245 (2) INFORMATION FOR SEQ ID NO : 3 : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 782 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: both (D) TOPOLOGY: both (ii) MOLECULE TYPE: cDNA (ix) FEATURE: (A) NAME/KEY: CDS (B) LOCATION: 1..771 (xi) SEQUENCE DESCRIPTION: SEQ ID NO : 3 : GAC GTC GTG ATG TCA CAG TCT CCA TCC TCC CTA CCT GTG TCA GTT GGC 48 Asp Val Val Met Ser Gin Ser Pro Ser Ser Leu Pro Val Ser Val Gly 250 255 260 GAG AAG GTT ACT TTG AGC TGC AAG TCC AGT CAG AGC CTT TTA TAT AGT 96 Glu Lys Val Thr Leu Ser Cys Lys Ser Ser Gin Ser Leu Leu Tyr Ser 265 270 275 GGT AAT CAA AAG AAC TAC TTG GCC TGG TAC CAG CAG AAA CCA GGG CAG 144 Gly Asn Gin Lys Asn Tyr Leu Ala Trp Tyr Gin Gin Lys Pro Gly Gin 280 285 290 TCT CCT AAA CTG CTG ATT TAC TGG GCA TCC GCT AGG GAA TCT GGG GTC 192 Ser Pro Lys Leu Leu lie Tyr Trp Ala Ser Ala Arg Glu Ser Gly Val 295 300 305 310 CCT GAT CGC TTC ACA GGC AGT GGA TCT GGG ACA GAT TTC ACT CTC TCC 240 Pro Asp Arg Phe Thr Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Ser 315 320 325 ATC AGC AGT GTG AAG ACT GAA GAC CTG GCA GTT TAT TAC TGT CAG CAG 288 He Ser Ser Val Lys Thr Glu Asp Leu Ala Val Tyr Tyr Cys Gin Gin 330 335 340 TAT TAT AGC TAT CCC CTC ACG TTC GGT GCT GGG ACC AAG CTT GTG CTG 336 Tyr Tyr Ser Tyr Pro Leu Thr Phe Gly Ala Gly Thr Lys Leu Val Leu 345 350 355 AAA GGC TCT ACT TCC GGT AGC GGC AAA CCC GGG AGT GGT GAA GGT AGC 384 Lys Gly Ser Thr Ser Gly Ser Gly Lys Pro Gly Ser Gly Glu Gly Ser 360 365 370 ACT AAA GGT CAG GTT CAG CTG CAG CAG TCT GAC GCT GAG TTG GTG AAA 432 Thr Lys Gly Gin Val Gin Leu Gin Gin Ser Asp Ala Glu Leu Val Lys 375 380 385 390 CCT GGG GCT TCA GTG AAG ATT TCC TGC AAG GCT TCT GGC TAC ACC TTC 480 Pro Gly Ala Ser Val Lys He Ser Cys Lys Ala Ser Gly Tyr Thr Phe 395 400 405 ACT GAC CAT GCA ATT CAC TGG GTG AAA CAG AAC CCT GAA CAG GGC CTG 528 Thr Asp His Ala He His Trp Val Lys Gin Asn Pro Glu Gin Gly Leu 410 415 420 GAA TGG ATT GGA TAT TTT TCT CCC GGA AAT GAT GAT TTT AAA TAC AAT 576 Glu Trp He Gly Tyr Phe Ser Pro Gly Asn Asp Asp Phe Lys Tyr Asn 425 430 435 GAG AGG TTC AAG GGC AAG GCC ACA CTG ACT GCA GAC AAA TCC TCC AGC 624 Glu Arg Phe Lys Gly Lys Ala Thr Leu Thr Ala Asp Lys Ser Ser Ser 440 445 450 ACT GCC TAC GTG CAG CTC AAC AGC CTG ACA TCT GAG GAT TCT GCA GTG 672 Thr Ala Tyr Val Gin Leu Asn Ser Leu Thr Ser Glu Asp Ser Ala Val 455 460 465 470 TAT TTC TGT ACA AGA TCC CTG AAT ATG GCC TAC TGG GGT CAA GGA ACC 720 Tyr Phe Cys Thr Arg Ser Leu Asn Met Ala Tyr Trp Gly Gin Gly Thr 475 480 485 TCG GTC ACC GTC TCC AAA AAG AAG AAA AAA AAG AAA AAG GTC ACC GTC 768 Ser Val Thr Val Ser Lys Lys Lys Lys Lys Lys Lys Lys Val Thr Val 490 495 500 TCC TAATAGGATC C 782 Ser (2) INFORMATION FOR SEQ ID NO: 4: (l) SEQUENCE CHARACTERISTICS: (A) LENGTH: 257 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (n) MOLECULE TYPE: protein (xi) SEQUENCE DESCRIPTION: SEQ ID NO: 4: Asp Val Val Met Ser Gin Ser Pro Ser Ser Leu Pro Val Ser Val Gly 1 5 10 15 Glu Lys Val Thr Leu Ser Cys Lys Ser Ser Gin Ser Leu Leu Tyr Ser 20 25 30 Gly Asn Gin Lys Asn Tyr Leu Ala Trp Tyr Gin Gin Lys Pro Gly Gin 35 40 45 Ser Pro Lys Leu Leu He Tyr Trp Ala Ser Ala Arg Glu Ser Gly Val 50 55 60 Pro Asp Arg Phe Thr Gly Ser Gly Ser Gly Thr Asp Phe Thr Leu Ser 65 70 75 80 He Ser Ser Val Lys Thr Glu Asp Leu Ala Val Tyr Tyr Cys Gin Gin 85 90 95 Tyr Tyr Ser Tyr Pro Leu Thr Phe Gly Ala Gly Thr Lys Leu Val Leu 100 105 110 Lys Gly Ser Thr Ser Gly Ser Gly Lys Pro Gly Ser Gly Glu Gly Ser 115 120 125 Thr Lys Gly Gin Val Gin Leu Gin Gin Ser Asp Ala Glu Leu Val Lys 130 135 140 Pro Gly Ala Ser Val Lys He Ser Cys Lys Ala Ser Gly Tyr Thr Phe 145 150 155 160 Thr Asp His Ala He His Trp Val Lys Gin Asn Pro Glu Gin Gly Leu 165 170 175 Glu Trp He Gly Tyr Phe Ser Pro Gly Asn Asp Asp Phe Lys Tyr Asn 180 185 190 Glu Arg Phe Lys Gly Lys Ala Thr Leu Thr Ala Asp Lys Ser Ser Ser 195 200 205 Thr Ala Tyr Val Gin Leu Asn Ser Leu Thr Ser Glu Asp Ser Ala Val 210 215 220 Tyr Phe Cys Thr Arg Ser Leu Asn Met Ala Tyr Trp Gly Gin Gly Thr 225 230 235 240 Ser Val Thr Val Ser Lys Lys Lys Lys Lys Lys Lys Lys Val Thr Val 245 250 255 Ser

Claims: Claims What is claimed is: 1. A single-chain antigen-binding polypeptide-polyalkylene oxide conjugate, comprising a single-chain antigen-binding polypeptide comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein said single-chain antigen-binding polypeptide is conjugated to polyalkylene oxide and wherein said single-chain antigen-binding polypeptide-polyalkylene oxide conjugate has an antigen binding affinity within a range of about one-fold to about ten-fold of the antigen binding affinity of said single-chain antigen-binding polypeptide in its unconjugated form. 2. A single-chain antigen-binding polypeptide-polyalkylene oxide conjugate, comprising a single-chain antigen-binding polypeptide comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein said single-chain antigen-binding polypeptide is conjugated to polyalkylene oxide and wherein said single-chain antigen-binding polypeptide-polyalkylene oxide conjugate has an antigen binding affinity within about ten-fold of the antigen binding affinity of said single-chain antigen-binding polypeptide in its unconjugated form. 3. A single-chain antigen-binding polypeptide-polyalkylene oxide conjugate, comprising a single-chain antigen-binding polypeptide comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein said single-chain antigen-binding polypeptide is conjugated to polyalkylene oxide and wherein said single-chain antigen-binding polypeptide-polyalkylene oxide conjugate has an antigen binding affinity within about five-fold of the antigen binding affinity of said single-chain antigen-binding polypeptide in its unconjugated form. 4. A single-chain antigen-binding polypeptide-polyalkylene oxide conjugate, comprising a single-chain antigen-binding polypeptide comprising: (a) a first polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein said single-chain antigen-binding polypeptide is conjugated to polyalkylene oxide and wherein said single-chain antigen-binding polypeptide-polyalkylene oxide conjugate has an antigen binding affinity within about two-fold of the antigen binding affinity of said single-chain antigen-binding polypeptide in its unconjugated form. 5. A single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking said first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least one Cys residue which is capable of polyalkylene oxide conjugation, wherein said Cys residue is located at a position selected from the group consisting of: (i) the amino acid position 11, 12, 13, 14 or 15 ofthe light chain variable region; (ii) the amino acid position 77, 78 or 79 ofthe light chain variable region; (iii) the amino acid position 11, 12, 13, 14 or 15 ofthe heavy chain variable region; (iv) the amino acid position 82B, 82C or 83 of the heavy chain variable region; (v) any amino acid position ofthe peptide linker; (vi) adjacent to the C-terminus of polypeptide (a) or (b); and (vii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 6. The single-chain antigen-binding polypeptide of claim 5 , wherein said Cys residue capable of polyalkylene oxide conjugation is located at a position selected from the group consisting of: (i') the amino acid position 77 ofthe light chain variable region; (ii') the amino acid position 82B ofthe heavy chain variable region; (iii') the amino acid position 3 ofthe peptide linker; (iv') adjacent to the C-terminus of said polypeptide (a) or (b); and (v') combinations thereof. 7. The single-chain antigen-binding polypeptide of claim 5 , wherein said first polypeptide (a) comprises the antigen binding portion ofthe variable region of an antibody light chain and said second polypeptide (b) comprises the antigen binding portion ofthe variable region of an antibody heavy chain. 8. The single-chain antigen-binding polypeptide of claim 5 , wherein the C- terminus of said second polypeptide (b) is the native C-terminus. 9. The single-chain antigen-binding polypeptide of claim 5 , wherein the C- terminus of said second polypeptide (b) comprises a deletion of one or plurality of amino acid residue(s), such that the remaining N-terminus amino acid residues of the second polypeptide are sufficient for the polyalkylene oxide conjugated single-chain antigen-binding polypeptide to be capable of binding an antigen. 10. The single-chain antigen-binding polypeptide of claim 5 , wherein the C- terminus of said second polypeptide (b) comprises an addition of one or plurality of amino acid residue(s), such that the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 11. The single-chain antigen-binding polypeptide of claim 5 , wherein said wherein said Cys residue capable of polyalkylene oxide conjugation is attached to a polyalkylene oxide moiety. 12. The polyalkylene oxide conjugated single-chain antigen-binding polypeptide of claim 11 , wherein said polyalkylene oxide conjugated single-chain antigen-binding polypeptide is conjugated to one or plurality of peptide, lipid, nucleic acid, drug, toxin, chelator, boron addend or detectable label molecules. 13. The polyalkylene oxide conjugated single-chain antigen-binding polypeptide of claim 11 , wherein said polyalkylene oxide conjugated single-chain antigen-binding polypeptide is conjugated to a canier having one or plurality of peptide, lipid, nucleic acid, drug, toxin, chelator, boron addend or detectable label molecules bound to said carrier. 14. A polynucleotide sequence encoding a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking said first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least one Cys residue which is capable of polyalkylene oxide conjugation, wherein said Cys residue is located at a position selected from the group consisting of: (i) the amino acid position 11, 12, 13, 14 or 15 of said light chain variable region; (ii) the amino acid position 77, 78 or 79 of said light chain variable region; (iii) the amino acid position 11, 12, 13, 14 or 15 of said heavy chain variable region; (iv) the amino acid position 82B, 82C or 83 of said heavy chain variable region; (v) any amino acid position of said peptide linker; (vi) adjacent to the C-terminus of said polypeptide (a) or (b); and (vii) combinations thereof, and wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 15. The polynucleotide sequence of claim 14, wherein said Cys residue capable of polyalkylene oxide conjugation is located at a position selected from the group consisting of: (i') the amino acid position 77 ofthe light chain variable region; (ii') the amino acid position 82B ofthe heavy chain variable region; (iii') the amino acid position 3 ofthe peptide linker; (iv') adjacent to the C-terminus of said polypeptide (a) or (b); and (v') combinations thereof. 16. A replicable cloning or expression vehicle comprising the polynucleotide sequence of claim 14. 17. The vehicle of claim 16 which is a plasmid. 18. A host cell transformed with the polynucleotide of claim 17. 19. The host cell of claim 18 which is a bacterial cell, a yeast cell or other fungal cell, an insect cell or a mammalian cell line. 20. The host cell of claim 19 which is Pichia pastoris. 21. A method of a producing single-chain antigen-binding polypeptide- polyalkylene oxide conjugate, comprising a single-chain antigen-binding polypeptide comprising: (a) providing a first genetic sequence encoding a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) providing a second genetic sequence encoding a second polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; and (c) linking the first and second genetic sequences (a) and (b) with a third genetic sequence encoding a linker into a fourth genetic sequence encoding a single chain polypeptide having an antigen binding site, wherein said single-chain antigen-binding polypeptide is capable of polyalkylene oxide conjugation and wherein said single-chain antigen-binding polypeptide-polyalkylene oxide conjugate retains antigen binding affinity within a range of about one-fold to about ten-fold of the antigen binding affinity of said single-chain antigen-binding polypeptide in its unconjugated form. 22. A method of producing a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) providing a first genetic sequence encoding a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) providing a second genetic sequence encoding a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) linking said first and second genetic sequences (a) and (b) with a third genetic sequence encoding a peptide linker into a fourth genetic sequence encoding a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least one Cys residue which is capable of polyalkylene oxide conjugation, wherein said Cys residue is located at a position selected from the group consisting of: (i) the amino acid position 11, 12, 13, 14 or 15 of said light chain variable region; (ii) the amino acid position 77, 78 or 79 of said light chain variable region; (iii) the amino acid position 11, 12, 13, 14 or 15 of said heavy chain variable region; (iv) the amino acid position 82B, 82C or 83 of said heavy chain variable region; (v) any amino acid position of said peptide linker; (vi) adjacent to the C-terminus of said polypeptide (a) or (b); and (vii) combinations thereof, and wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen; (d) transforming a host cell with said fourth genetic sequence encoding said single-chain antigen-binding polypeptide of step (c); and (e) expressing said single-chain antigen-binding polypeptide of step (c) in said host, thereby producing a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation. 23. The method of claim 22, wherein said Cys residue capable of polyalkylene oxide conjugation is located at a position selected from the group consisting of: (i 1 ) the amino acid position 77 ofthe light chain variable region; (ii') the amino acid position 82B ofthe heavy chain variable region; (iii') the amino acid position 3 ofthe peptide linker; (iv') adjacent to the C-terminus of said polypeptide (a) or (b); and (v') combinations thereof. 24. The method of claim 22, said first genetic sequence encoding a first polypeptide (a) comprises the antigen binding portion ofthe variable region of an antibody light chain and said second genetic sequence encoding a second polypeptide (b) comprises the antigen binding portion ofthe variable region of an antibody heavy chain. 25. The method of claim 22, wherein the C-terminus of said second polypeptide (b) is the native C-terminus. 26. The method of claim 22, wherein the C-terminus of said second polypeptide (b) comprises a deletion of one or plurality of amino acid residue(s), such that the remaining N-terminus amino acid residues ofthe second polypeptide are sufficient for the polyalkylene oxide conjugated single-chain antigen-binding polypeptide to be capable of binding an antigen. 27. The method of claim 22, wherein the C-terminus of said second polypeptide (b) comprises an addition of one or plurality of amino acid residue(s), such that the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 28. A multivalent single-chain antigen-binding polypeptide-polyalkylene oxide conjugate, comprising two or more single-chain antigen binding polypeptides, each single-chain antigen-binding polypeptide comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein said single-chain antigen-binding polypeptide is conjugated to polyalkylene oxide and wherein said single-chain antigen-binding polypeptide-polyalkylene oxide conjugate retains antigen binding affinity within a range of about one-fold to about ten-fold of the antigen binding affinity of said single-chain antigen-binding polypeptide in its unconjugated form. 29. A multivalent single-chain antigen-binding protein, comprising two or more single-chain antigen-binding polypeptides, each single-chain antigen-binding polypeptide comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking said first and second polypeptides wherein one ofthe two single-chain antigen-binding polypeptide has at least one Cys residue which is capable of polyalkylene oxide conjugation, wherein said Cys residue is located at a position selected from the group consisting of: (i) the amino acid position 11, 12, 13, 14 or 15 of said light chain variable region; (ii) the amino acid position 77, 78 or 79 of said light chain variable region; (iii) the amino acid position 11, 12, 13, 14 or 15 of said heavy chain variable region; (iv) the amino acid position 82B, 82C or 83 of said heavy chain variable region; (v) any amino acid position of said peptide linker; (vi) adjacent to the C-terminus of said polypeptide (a) or (b); and (vii) combinations thereof, and wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 30. The multivalent protein of claim 29, wherein said Cys residue capable of polyalkylene oxide conjugation is located at a position selected from the group consisting of: (i') the amino acid position 77 ofthe light chain variable region; (ii') the amino acid position 82B ofthe heavy chain variable region; (iii') the amino acid position 3 ofthe peptide linker; (iv') adjacent to the C-terminus of said polypeptide (a) or (b); and (V) combinations thereof. 31. The multivalent protein of claim 29, wherein said first polypeptide (a) comprises the antigen binding portion ofthe variable region of an antibody light chain and said second polypeptide (b) comprises the antigen binding portion ofthe variable region of an antibody heavy chain. 32. The multivalent protein of claim 29, wherein the C-terminus of said second polypeptide (b) is the native C-terminus. 33. The multivalent protein of claim 29, wherein the C-terminus of said second polypeptide (b) comprises a deletion of one or plurality of amino acid residue(s), such that the remaining N-terminus amino acid residues ofthe second polypeptide are sufficient for the polyalkylene oxide conjugated single-chain antigen-binding polypeptide to be capable of binding an antigen. 34. The multivalent protein of claim 29, wherein the C-terminus of said second polypeptide comprises an addition of one or plurality of amino acid residue(s), such that the polyalkylene oxide conjugated single-chain antigen- binding polypeptide is capable of binding an antigen. 35. The multivalent protein of claim 29, wherein said wherein said Cys residue capable of polyalkylene oxide conjugation is attached to a polyalkylene oxide moiety. 36. The polyalkylene oxide conjugated multivalent protein of claim 35, wherein said polyalkylene oxide conjugated multivalent protein is conjugated to one or plurality of peptide, lipid, nucleic acid, drug, toxin, chelator, boron addend or detectable label molecule(s). 37. A method of detecting an antigen suspected of being in a sample, comprising: (a) contacting said sample with the polyalkylene oxide conjugated polypeptide or protein of claim 1 or 11, wherein said polyalkylene oxide conjugated polypeptide or protein is conjugated to one or plurality of detectable label molecule(s), or conjugated to a canier having one or plurality of detectable label molecule(s) bound to said canier; and (b) detecting whether said polyalkylene oxide conj ugated single-chain antigen-binding polypeptide or protein has bound to said antigen. 38. A method of imaging the internal structure of an animal, comprising administering to said animal an effective amount of the polyalkylene oxide conjugated polypeptide or protein of claim 1 or 11, wherein said polyalkylene oxide conjugated polypeptide or protein is conjugated to one or plurality of detectable label or chelator molecule(s), or conjugated to a carrier having one or plurality of detectable label or chelator molecule(s) bound to said canier, and measuring detectable radiation associated with said animal. 39. The method of claim 38, wherein said animal includes a human. 40. A method for treating a targeted disease, comprising administering an effective amount of a composition comprising the polyalkylene oxide conjugated polypeptide or protein of claim 1 or 11 and a pharmaceutically acceptable canier vehicle, wherein said polyalkylene oxide conjugated polypeptide or protein is conjugated to one or plurality of peptide, lipid, nucleic acid, drug, toxin, boron addend or radioisotope molecule(s), or conjugated to a carrier having one or plurality of peptide, lipid, nucleic acid, drug, toxin, boron addend or radioisotope molecule(s) bound to said carrier. 41. A single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least three consecutive Lys residues which are capable of polyalkylene oxide conjugation and wherein any one of said consecutive Lys residues is located at a position selected from the group consisting of (i) any amino acid position ofthe peptide linker; (ii) adjacent to the C-terminus ofthe second polypeptide (b); and (iii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 42. A polynucleotide sequence encoding a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least three consecutive Lys residues which are capable of polyalkylene oxide conjugation and wherein any one of said consecutive Lys residues is located at a position selected from the group consisting of (i) any amino acid position ofthe peptide linker; (ii) adjacent to the C-terminus ofthe second polypeptide (b); and (iii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 43. A replicable cloning or expression vehicle comprising the polynucleotide sequence of claim 42. 44. The vehicle of claim 43 which is a plasmid. 45. A host cell transformed with the polynucleotide of claim 42. 46. The host cell of claim 39 which is a bacterial cell, a yeast cell or other fungal cell, an insect cell or a mammalian cell line. 47. The host cell of claim 46 which is Pichia pastoris. 48. A method of producing a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion of the variable region of an antibody heavy or light chain; and (c) a peptide linker linking the first and second polypeptides (a) and (b) into a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least three consecutive Lys residues which are capable of polyalkylene oxide conjugation and wherein any one of said consecutive Lys residues is located at a position selected from the group consisting of (i) any amino acid position ofthe peptide linker; (ii) adjacent to the C-terminus ofthe second polypeptide (b); and (iii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 49. The single-chain antigen-binding polypeptide of claim 41 , wherein said wherein said wherein any one of said consecutive Lys residues capable of polyalkylene oxide conjugation is attached to a polyalkylene oxide moiety. 50. The polyalkylene oxide conjugated single-chain antigen-binding polypeptide of claim 49, wherein said polyalkylene oxide conjugated single-chain antigen-binding polypeptide is conjugated to one or plurality of peptide, lipid, nucleic acid, drug, toxin, chelator, boron addend or detectable label molecules. 51. The polyalkylene oxide conjugated single-chain antigen-binding polypeptide of claim 49, wherein said polyalkylene oxide conjugated single-chain antigen-binding polypeptide is conjugated to a canier having one or plurality of peptide, lipid, nucleic acid, drug, toxin, chelator, boron addend or detectable label molecules bound to said canier. 52. A method of producing a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation, comprising: (a) providing a first genetic sequence encoding a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) providing a second genetic sequence encoding a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) linking said first and second genetic sequences (a) and (b) with a third genetic sequence encoding a peptide linker into a fourth genetic sequence encoding a single chain polypeptide having an antigen binding site, wherein the single-chain antigen-binding polypeptide has at least three consecutive Lys residues which are capable of polyalkylene oxide conjugation and wherein any one of said consecutive Lys residues is located at a position selected from the group consisting of (i) any amino acid position ofthe peptide linker; (ii) adjacent to the C-terminus ofthe second polypeptide (b); and (iii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen; (d) transforming a host cell with said fourth genetic sequence encoding said single-chain antigen-binding polypeptide of step (c); and (e) expressing said single-chain antigen-binding polypeptide of step (c) in said host, thereby producing a single-chain antigen-binding polypeptide capable of polyalkylene oxide conjugation. 53. The method of claim 52, said first genetic sequence encoding a first polypeptide (a) comprises the antigen binding portion ofthe variable region of an antibody light chain and said second genetic sequence encoding a second polypeptide (b) comprises the antigen binding portion ofthe variable region of an antibody heavy chain. 54. The method of claim 52, wherein the C-terminus of said second polypeptide (b) is the native C-terminus. 55. The method of claim 52, wherein the C-terminus of said second polypeptide (b) comprises a deletion of one or plurality of amino acid residue(s), such that the remaining N-terminus amino acid residues ofthe second polypeptide are sufficient for the polyalkylene oxide conjugated single-chain antigen-binding polypeptide to be capable of binding an antigen. 56. The method of claim 52, wherein the C-terminus of said second polypeptide (b) comprises an addition of one or plurality of amino acid residue(s), such that the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 57. A multivalent single-chain antigen-binding protein, comprising two or more single-chain antigen-binding polypeptides, each single-chain antigen-binding polypeptide comprising: (a) a first polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the antigen binding portion ofthe variable region of an antibody heavy or light chain; and (c) a peptide linker linking said first and second polypeptides wherein one ofthe two single-chain antigen-binding polypeptides has at least three consecutive Lys residues which are capable of polyalkylene oxide conjugation and wherein any one of said consecutive Lys residues is located at a position selected from the group consisting of (i) any amino acid position ofthe peptide linker; (ii) adjacent to the C-terminus ofthe second polypeptide (b); and (iii) combinations thereof, wherein the polyalkylene oxide conjugated single-chain antigen-binding polypeptide is capable of binding an antigen. 58. The multivalent protein of claim 57, wherein said first polypeptide (a) comprises the antigen binding portion ofthe variable region of an antibody light chain and said second polypeptide (b) comprises the antigen binding portion ofthe variable region of an antibody heavy chain. 59. The multivalent protein of claim 57, wherein the C-terminus of said second polypeptide (b) is the native C-terminus. 60. The multivalent protein of claim 57, wherein the C-terminus of said second polypeptide (b) comprises a deletion of one or plurality of amino acid residue(s), such that the remaining N-terminus amino acid residues ofthe second polypeptide are sufficient for the polyalkylene oxide conjugated single-chain antigen-binding polypeptide to be capable of binding an antigen. 61. The multivalent protein of claim 57, wherein the C-terminus of said second polypeptide comprises an addition of one or plurality of amino acid residue(s), such that the polyalkylene oxide conjugated single-chain antigen- binding polypeptide is capable of binding an antigen. 62. The multivalent protein of claim 57, wherein any one of said consecutive Lys residues capable of polyalkylene oxide conjugation is attached to a polyalkylene oxide moiety. 63. The polyalkylene oxide conjugation multivalent protein of claim 62, wherein said polyalkylene oxide conjugated multivalent protein is conjugated to one or plurality of peptide, lipid, nucleic acid, drug, toxin, chelator, boron addend or detectable label molecule(s).

Inventors: FILPULA DAVID R, LEE LIHSYNG S, SHORR ROBERT G L, WHITLOW MARC, FILPULA, DAVID, R., LEE, LIHSYNG, S., SHORR, ROBERT, G., L., WHITLOW, MARC
Applicants: ENZON INC, ENZON, INC.
Application year: 1998
Main classification: A61K39
IPC codes: A61K39, A61K47, A61P35, C07K14, C07K16, C12N1, C12N5, C12N15, C12P21, C12R1, G01N33