US 5,767,260 AGrant

Antigen-Binding Fusion Proteins

Issue Date:1998-06-16

•8 Claims

•14 Drawing Sheets

Abstract

Compositions of, genetic constructions coding for, and methods for producing single-chain and multivalent immunoeffector antigen-binding fusion proteins are provided by the invention. Antigen-binding fusion proteins having phospholipase A activating protein and/or tumor necrosis factor fragments are also provided by the invention. Genetic sequences coding for single-chain and multivalent immunoeffector antigen-binding fusion proteins are disclosed.

Metadata

Assignee

Enzon Inc.

Inventors

Marc Whitlow
David Filpula
Robert Shorr

Application Information

Application Number:US 5159032

Filing Date:1995-08-16

Priority Date:1994-10-13

Art Unit:186

Classifications

IPC:

C12N 1513C07H 2104C07K 1900

Field of Search:

53653043523.53;23.4387.3240.2;320.1;69.7;252.3

Patent Drawings (14 sheets)

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the production of antigen-binding fusion molecules. More specifically, the invention relates to fusion forms of antigen-binding proteins having an immunoeffector moiety and/or a cytolytic moiety, particularly fusion forms having an immunoeffector or cytolytic moiety derived from tumor necrosis factor and/or phospholipase A activating protein. The invention also relates to multivalent fusion forms of antigen-binding proteins. Compositions of, genetic constructions for, methods of use, and methods for producing these antigen-binding fusion proteins are also disclosed.

2. Description of the Background 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.

Covalent interchain bonding serves to stabilize the various chains of antibody molecules. The prototypical immunoglobulin structure consists of disulfide bonds holding the C.sub.L and C.sub.H 1 domains together and also holding the hinge regions of the two heavy chains together. The so-called hinge region between the C.sub.H 1 and C.sub.H 2 domains contains the cysteine residues that crosslink to form the linkage between the two heavy chains. See, for example, Clark, W. R., The Experimental Foundations of Modern Immunology, 2nd Ed., John Wiley & Sons, New York (1983).

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 (termed V.sub.L) and one constant region (C.sub.L), while the heavy chain comprises one variable region (V.sub.H) and three constant regions (C.sub.H 1, C.sub.H 2 and C.sub.H 3). Pairs of regions associate to form discrete structures. In particular, the light and heavy chain variable regions, V.sub.L and V.sub.H, associate to form an "F.sub.V " area which contains the antigen-binding site.

The variable regions of both heavy and light chains show considerable variability in structure and amino acid composition from one antibody molecule to another, whereas the constant regions show little variability. The term "variable" as used in this specification refers to the diverse nature of the amino acid sequences of the antibody heavy and light chain variable regions. Each antibody recognizes and binds antigen through the binding site defined by the association of the heavy and light chain variable regions into an F.sub.V area. The light-chain variable region V.sub.L and the heavy-chain variable region V.sub.H of a particular antibody molecule have specific amino acid sequences that allow the antigen-binding site to assume a conformation that binds to the antigen epitope recognized by that particular antibody.

Within the variable regions are found regions in which the amino acid sequence is extremely variable from one antibody to another. Three of these so-called "hypervariable" regions or "complementarity-determining regions" (CDR's) are found in each of the light and heavy chains. The three CDR's from a light chain and the three CDR's from a corresponding heavy chain form the antigen-binding site.

Cleavage of the naturally-occurring antibody molecule with the proteolytic enzyme papain generates fragments which retain their antigen-binding site. These fragments, commonly known as Fab's (for Fragment, antigen binding site) are composed of the C.sub.L, V.sub.L, C.sub.H 1 and V.sub.H regions of the antibody. In the Fab the light chain and the fragment of the heavy chain are covalently linked by a disulfide linkage.

Antibodies have been generated to deliver cells, cytotoxins, or drugs to specific sites. An important use has been to deliver host cytotoxic cells, such as natural killer or cytotoxic T cells, to specific cellular targets. (Staerz et al., Nature 314:628 (1985); Songilvilai, et al., Clin. Exp. Immunol. 79:315 (1990)). Another important use has been to deliver cytotoxic proteins to specific cellular targets. (Raso et al., Cancer Res. 41:2073 (1981); Honda et al., Cytotechnology 4:59 (1990)). A further important use has been to deliver anti-cancer non-protein drugs to specific cellular targets (Corvalan et al., Intl. J. Cancer Suppl. 2:22 (1988); Pimm et al., Brit. J. Can. 61:508 (1990)).

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 (herein "SCA") incorporate a linker polypeptide to bridge the individual variable regions, V.sub.L and V.sub.H, into a single polypeptide chain. A computer-assisted method for linker design is described more particularly in U.S. Pat. No. 4,704,692. A description of the theory and production of single-chain antigen-binding proteins is found in U.S. Pat. Nos. 4,946,778 and 5,260,203. The single-chain antigen-binding proteins produced under the process recited in U.S. Pat. Nos. 4,946,778 and 5,260,203 have binding specificity and affinity substantially similar to that of the corresponding Fab fragment.

Phospholipase A activating protein (herein "PLAP") is a protein that activates phospholipase A, a lipolytic enzyme which hydrolizes the 2-acyl fatty acid ester of glycerophospholipids. This hydrolysis releases arachidonic acid which is converted into a number of biologically active compounds called eicosanoids. PLAP has been postulated to be involved in the inflammatory cascade in certain biological settings, and induces eicosanoid release and stimulation of joint inflammation, related to rheumatoid arthritis. It has also been shown that PLAP stimulates human neutrophil aggregation and the release of lysosomal enzymes, superoxide, and eicosanoids (Bomalaski et al., J. Immunol. 142 (11):3957-3962 (1989).

Further, PLAP activity has been shown to reside in several different gene products and is ubiquitous. The gene encoding PLAP has been cloned from a cDNA library (Clark et al., Proc. Natl. Acad. Sci. USA 88:5418-5422 (1991)). Antibodies have also been generated to recombinant PLAP using PLAP-.beta.-galactosidase fusion protein as antigen (Clark et al., Proc. Natl. Acad. Sci. USA 88: 5418-5422 (1991)). PLAP shares antigen and functional characteristics with melittin and was originally discovered and isolated through these similarities (Clark et al. J. Biochem. 262 (9):4402-4406 (1987)).

Tumor necrosis factors are polypeptide cytokines which serve a critical role as mediators of endotoxin-induced vascular collapse and are involved in certain inflammatory reactions. Two forms of tumor necrosis factor are known--TNF-alpha (or cachectin) and TNF-beta (or lymphotoxin) (Eck et al., J. Biol. Chem. 264:17595-17605 (1989)). The human TNF-alpha gene cDNA was cloned and the base sequence was determined (Wang et al., Science 228:149-154 (1985)). The pathogenesis of the inflammatory reaction mediated by TNF may involve eicosanoids. Tumor necrosis factor is primarily produced in monocytes and macrophages following activation by endotoxin as well as other inflammatory and immune stimuli. TNF is known to be an agent responsible for hemorrhagic necrosis of experimental tumors. It is also a likely candidate responsible for the mediation of cachexia, septic shock, and certain other inflammatory reactions. TNF has been shown to induce the manifold effects of bone resorption, eicosanoid synthesis, collagenase production, vasculitis, and hemorrhagic necrosis of transplanted tissues (Van den Boch, H., Biochem. Biophys. Acta. 604:191-246 (1980)).

The vascular endothelial lining is important in regulating the permeability and structure of blood vessels. Further, morphological and biological activities of the vasculature can be modified in response to changes in endothelial cell structure (Bell et al., Proc. Natl. Acad. Sci. USA 76:32-38-3241 (1979); Chau et al., Biochem. Biophys. Res. Commun. 100:1688-1695 (1981); Clark et al., J. Biol. Chem. 261:10713-10718 (1986); Clark et al., Biochem. J. 250:125-132 (1988)). TNF may interact with the endothelial cell lining to cause some of its many effects. TNF has been reported to increase the synthesis of eicosanoids (Aderem et al., J. Exp. Med. 163:139-154 (1986); Burch et al., Proc. Natl. Acad. Sci. USA 83:7201-7205 (1986); Burch et al., Proc. Natl. Acad. Sci. USA 84:6374-6378 (1987); Clark et al., Eur. J. Pharmacol. 116:207-220 (1985); Clark et al., Prostaglandins 31:157-166 (1986)). Certain eicosanoids are known to effect the vasculature. It is therefore likely that TNF mediates certain of its biological effects through increased eicosanoid synthesis following stimulation of endothelial cells. Elaboration of eicosanoids in response to TNF stimulation may affect cells in close proximity to those releasing the eicosanoids or may act on more distant cellular targets. TNF was shown to induce phospholipase A.sub.2 activity and synthesis of a phospholipase A.sub.2 -activating protein in endothelial cells (Clark et al., Biochem. J. 250:125-132 (1988)).

There is some evidence that TNF is effective in the treatment of parasitic disease (Wozencroft et al., Infect. Immun. 43:664 (1984)).

Fusion proteins have traditionally been utilized to merge characteristics inherent in different proteins into the same molecule. This methodology allows for the production of useful multifunctional molecules. These molecules have been used for many purposes.

Fusion proteins consisting of a single-chain antibody fused to interleukin-2 have been reported (Savage, P., The Third Annual IBC International Conference on Antibody Engineering: New Technology and Application Implications, International Business Communications, Southborough, Mass. (1992)).

It has also been reported that fusion antibodies have been constructed using interleukin-2, GM-CSF and TNFs .alpha. and .beta. fused to the carboxyl terminus (herein "C terminus") of a chimeric anti-ganglioside antibody (ch14.18) and expressed in transfected hybridoma cells (Gillies et al., Bioconj. Chem. 4(3):230-235 (1993)). Moreover, this chimeric anti-ganglioside antibody fused to interleukin-2 was shown to stimulate T-cell killing of tumor cells (Gillies et al., Bioconj. Chem. 4(3):230-235 (1993)).

It has also been reported that enhanced tumor uptake of two different monoclonal antibodies can be induced by an IL-2 immunoconjugate (LeBarthon et al., Can. Res. 51: 2694-2698 (1991)).

Single chain polypeptide molecules capable of binding antigen which include a separate functional polypeptide sequence have been described (U.S. Pat. No. 5,132,405). Multimers containing these multifunctional proteins have also been described (PCT WO 88/09344).

Advances in protein design and construction have recently allowed for the production of rationally-designed, intramolecular-bond stabilized proteins. A computer-assisted method for identifying amino acid residues amenable to replacement by cysteine residues to promote the formation of a protein-stabilizing disulfide bond is found in U.S. Pat. No. 4,908,773.

SUMMARY OF THE INVENTION

This invention relates to the discovery that single-chain antigen-binding fusion proteins having an immunoeffector or cytolytic moiety have significant utility beyond that of single-chain antigen-binding proteins. Immunoeffector and cytolytic antigen-binding fusion proteins have more than an antigen-binding site activity or function. An immunoeffector or cytolytic moiety on the fusion antigen-binding protein will impart upon the protein certain or all of the immunoeffector or cytolytic attributes of the fusion partner or partners. Other novel uses of immunoeffector and cytolytic antigen-binding fusion proteins have been demonstrated or are envisioned here.

Accordingly, the invention is directed to single-chain and multivalent immunoeffector and cytolytic antigen-binding fusion proteins, compositions of single-chain and multivalent immunoeffector and cytolytic antigen-binding fusion proteins, methods of making and purifying single-chain and multivalent immunoeffector and cytolytic antigen-binding fusion proteins, and uses for single-chain and multivalent immunoeffector and cytolytic antigen-binding fusion proteins. The invention provides an immunoeffector or cytolytic antigen-binding fusion protein having at least one single-chain antigen-binding protein molecule. Each single-chain antigen-binding molecule has a first polypeptide and a second polypeptide joined by a linker. Each of the polypeptides has the binding portion of the variable region of an antibody heavy or light chain. An immunoeffector polypeptide or a cytolytic polypeptide is fused to at least one of the first or second polypeptides or the peptide linker. It is preferred that the immunoeffector polypeptide or a cytolytic polypeptide is selected from the group consisting of: TNF, an immunoeffector or cytolytic fragment of TNF, PLAP, and an immunoeffector or cytolytic fragment of PLAP.

Also provided is an antigen-binding fusion protein as described above further having an immunoeffector or cytolytic fragment of IL-2 fused to at least one of the first or second polypeptides or the peptide linker.

Further provided is a genetic sequence which codes for the single-chain fusion protein having a first DNA sequence coding for the V.sub.L or V.sub.H of a CC49 monoclonal antibody polypeptide, a second DNA sequence coding for the V.sub.L or V.sub.H of a CC49 monoclonal antibody polypeptide, a DNA sequence coding for a peptide linker linking the first and second polypeptides into the single-chain protein, and a DNA sequence coding for an immunoeffector polypeptide or cytolytic polypeptide fused to a DNA sequence coding for any one of the first or second polypeptides, or the linker peptide.

It is preferred in any of the embodiments of the invention that the first polypeptide has the binding portion of the variable region of an antibody light chain, and the second polypeptide has the binding portion of the variable region of an antibody heavy chain.

It is also preferred in any of the embodiments of the invention that the first polypeptide has the binding portion of the variable region of an antibody light chain, and the second polypeptide has the binding portion of the variable region of an antibody light chain.

It is further preferred in any of the embodiments of the invention that the first polypeptide has the binding portion of the variable region of an antibody heavy chain, and the second polypeptide has the binding portion of the variable region of an antibody heavy chain.

Another embodiment of the invention is a composition having an antigen-binding fusion protein, particularly a protein having two immunoeffector domains, two polypeptides capable of mediating cytolysis, or a combination of two of these polypeptides.

It is preferred that the compositions of the invention contain a pharmaceutically acceptable carrier or diluent.

It is more preferred in the compositions having multivalent fusion proteins that the first polypeptide has the binding portion of the variable region of an antibody light chain, and the second polypeptide has the binding portion of the variable region of an antibody heavy chain.

It is also more preferred in the compositions having multivalent fusion proteins that the first polypeptide has the binding portion of the variable region of an antibody light chain, and the second polypeptide has the binding portion of the variable region of an antibody light chain.

It is further more preferred in the compositions having multivalent fusion proteins that the first polypeptide has the binding portion of the variable region of an antibody heavy chain, and the second polypeptide has the binding portion of the variable region of an antibody heavy chain.

Another aspect of the invention includes a method of killing tumor cells in or suspected of being in an individual, which has the steps of contacting the individual with an immunoeffector or cytolytic antigen-binding fusion protein.

Also provided is a multivalent antigen-binding fusion protein having at least two single-chain immunoeffector or cytolytic antigen-binding fusion proteins. In these molecules, each of the fusion proteins has a first polypeptide with a binding portion of the variable region of an antibody heavy or light chain, a second polypeptide with the binding portion of the variable region of an antibody heavy or light chain, and a peptide linker linking the first and second polypeptides into the single-chain molecule. At least one of the single-chain molecules in this multivalent molecule further has an immunoeffector polypeptide or cytolytic polypeptide fused to at least one peptide of the first or second polypeptides or the peptide linker. It is preferred that the immunoeffector polypeptide or cytolytic polypeptide is selected from the group consisting of: TNF, an immunoeffector or cytolytic fragment of TNF, PLAP, and an immunoeffector or cytolytic fragment of PLAP.

Also provided is a single-chain fusion protein having a first and second polypeptide each of which has the binding portion of the variable region of an antibody light chain, and a peptide linker linking the first and second polypeptides as described above. An immunoeffector polypeptide or cytolytic polypeptide is fused to at least one peptide of the first or second polypeptides or peptide linker. The immunoeffector polypeptide or cytolytic polypeptide is selected from the group consisting of TNF, an immunoeffector or cytolytic fragment of TNF, PLAP, and an immunoeffector or cytolytic fragment of PLAP. A similar molecule is provided differing only by having two binding portions of the variable region of an antibody heavy chain instead of binding portions from the light chain.

A preferred embodiment of the invention is a DNA coding for a single-chain fusion protein having a V.sub.L and V.sub.H of a CC49 monoclonal antibody joined by a peptide linker as described above. A DNA sequence coding for an immunoeffector polypeptide or cytolytic polypeptide is fused to at least one DNA sequence coding for the V.sub.L or V.sub.H peptide or the peptide linker. The imnmunoeffector polypeptide or cytolytic polypeptide is selected from the group consisting of TNF, an immunoeffector or cytolytic fragment of TNF, PLAP, and an immunoeffector or cytolytic fragment of PLAP.

Further provided is an antigen-binding fusion proteins wherein the immunoeffector polypeptide or cytolytic polypeptide has the sequence Glu Ser Pro Leu Ile Ala Lys Val Leu Thr Thr Glu Pro Pro Ile Ile Thr Pro Val Arg Arg (SEQ ID NO:1).

Also provided is an antigen-binding fusion protein wherein the peptide spacer has a sequence selected from the group consisting of: Gly Ser; and Gly Ser Gly Lys Pro Gly Ser Gly Glu Gly (SEQ ID NO:11).

A further embodiment of the invention is an antigen-binding fusion protein wherein the peptide spacer has the sequence Gly Ser His His His His His Ser Gly (SEQ ID NO:2).

Also provided is a multivalent antigen-binding fusion protein wherein at least one of the peptide spacers has a sequence selected from the group consisting of: Gly Ser, Gly Ser His His His His His Ser Gly (SEQ ID NO:2) and Gly Ser Gly Lys Pro Gly Ser Gly Glu Gly (SEQ ID NO:11).

Also provided is a genetic sequence which codes for a single-chain fusion protein. The DNA sequence has a sequence coding for a first polypeptide having the binding portion of the variable region of an antibody light or heavy chain. The DNA sequence also has a sequence coding for a second polypeptide having the binding portion of the variable region of an antibody light or heavy chain. The DNA sequence also has a sequence which codes for a peptide linker linking the first and second polypeptides into the single-chain protein. The fusion portion of the DNA sequence codes for and an immunoeffector polypeptide fused to at least a DNA sequence which codes for one peptide of the first or second polypeptides or peptide linker. It is preferred that the immunoeffector or cytolytic polypeptide is selected from the group consisting of: TNF, an immunoeffector or cytolytic fragment of TNF, PLAP, and an immunoeffector or cytolytic fragment of PLAP.

A preferred genetic sequence of the invention codes for another single-chain fusion protein. This embodiment has a first DNA sequence coding for the V.sub.L or V.sub.H of a CC49 monoclonal antibody linked to a second DNA sequence coding for the V.sub.L or V.sub.H of a CC49 monoclonal antibody and a DNA sequence coding for a peptide linker linking the first and second V.sub.L or V.sub.H into a single-chain protein. The linked DNA molecule also has a DNA sequence coding for an immunoeffector polypeptide fused to at least one DNA coding for the first or second polypeptides or peptide linker. It is preferred that the immunoeffector is selected from the group consisting of: TNF, an immunoeffector or cytolytic fragment of TNF, PLAP, and an immunoeffector or cytolytic fragment of PLAP.

Another aspect of the present invention includes the genetic constructions encoding the combinations of regions V.sub.L -V.sub.L and V.sub.H -V.sub.H for single-chain fusion molecules, and other constructs encoding multivalent immunoeffector antigen-binding fusion proteins.

Also included are replicable cloning or expression vehicles including plasmids, hosts transformed with the aforementioned genetic sequences, and methods of producing proteins with the sequences, transformed hosts, and expression vehicles.

Methods of use are provided, such as a method of using the protein as a carrier to treat pathologies of specific bodily organs of an animal, a therapeutic method of using the protein to treat a medical condition, and an immunotherapeutic method of conjugating a protein with a therapeutically or diagnostically effective agent.

An advantage of using antigen-binding fusion proteins of the present invention instead of fused or conjugated whole antibodies, is the enhanced clearing of the antigen-binding fusion proteins from the blood due to their smaller size as compared to fused or conjugated whole antibodies which may afford lower background in imaging applications. Antigen-binding fusion proteins may penetrate solid tumors better than fusion proteins containing whole antibodies, resulting in better tumor-fighting ability. Also, because they are smaller and lack the constant domains of intact antibodies, the antigen-binding fusion proteins of the present invention may be less immunogenic than fusion proteins containing whole antibodies. The constant domains of whole antibodies also contain binding sites for liver, spleen and certain other cells and their absence should thus reduce accumulation in non-target tissues.

Another advantage of antigen-binding fusion proteins of the present invention is the ease with which they may be produced and engineered, as compared to the myeloma-fusing technique pioneered by Kohler and Milstein that is used to produce whole antibodies combined with the cumbersome techniques of conjugating proteins to whole antibodies.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention as defined in the claims can be better understood with reference to the text and to the following drawings:

FIGS. 1A-C illustrate a schematic of monovalent and multivalent antigen-binding proteins of the invention.

FIG. 1A depicts monovalent antigen binding fusion molecules, bound to antigens, having either an immunoeffector or cytolytic moiety (illustrated as a helix) fused to the V.sub.L domain. Also depicted is a monovalent antigen binding fusion molecule having either an immunoeffector or cytolytic moiety (illustrated as a helix with a sawtooth terminus) fused to the V.sub.H domain.

FIG. 1B illustrates a bivalent antigen-binding fusion protein wherein each monomeric subunit is a fusion protein. The two fusion partners are different in this fusion protein.

FIG. 1C depicts a bivalent antigen-binding fusion molecule wherein only a one of a monomeric subunit is a fusion protein. This fusion protein monomer comprises two different immunoeffector or cytolytic moieties, one on the V.sub.L domain and one on the V.sub.H domain.

FIGS. 2A-B illustrate a schematic diagram of various monovalent and multivalent antigen-binding fusion molecules.

FIG. 2A illustrates a dimeric molecule, each subunit having a different immunoeffector or cytolytic moiety fused in the linker.

FIG. 2B depicts a trimeric molecule. One of the monomeric subunits is not a fusion molecule, and the other two monomeric subunits are fusion proteins.

FIGS. 3A-C illustrate a schematic of divalent and trivalent fusion molecules.

FIG. 3A depicts a homobivalent antigen-binding fusion protein wherein each of the V.sub.L domains is fused to an immunoeffector or cytolytic moiety. The fusion protein is shown bound to antigen.

FIG. 3B depicts a heterobivalent molecule wherein two different immunoeffector or cytolytic moieties are present. One is fused to a V.sub.L domain and the other is fused to a V.sub.H domain.

FIG. 3C depicts a trivalent antigen-binding fusion protein wherein an immunoeffector or cytolytic moiety is fused to one of the variable domains of each single-chain fusion protein. The multivalent molecule is associated by interactions within the protein sequence of the immunoeffector domain. It is contemplated that a trimeric antigen-binding fusion protein comprising TNF, which naturally forms trimers, may associate in this way.

FIGS. 4A-B illustrates the DNA (SEQ ID NO:3) and amino acid (SEQ ID NO:4) sequence of CC49/212 SCA with a PLAP C-terminus.

FIGS. 5A-B illustrates the DNA (SEQ ID NO:5) and amino acid (SEQ ID NO:6) sequence of CC49 V.sub.L -PLAP-CC49 V.sub.H SCA.

FIGS. 6A-B depicts the DNA (SEQ ID NO:7) and amino acid (SEQ ID NO:8) sequence of CC49/212 SCA with PLAP N-terminus.

FIG. 7 depicts a competition radioimmunoassay of CC49 IgG (.sup.125 I labeled). CC49 IgG is competed against PLAP No. 1, PLAP No. 2 and CC49/218 SCA (labeled SFv CC49 218). PLAP No. 1 and PLAP No. 2 represent two different preparations of CC49/212 SCA with PLAP C-terminus.

FIGS. 8A-B depicts the cDNA (SEQ ID NO:9) and amino acid (SEQ ID NO:10) sequence of human TNF-alpha. The arrow indicates the border between the amino terminal amino acid (valine, boxed) of mature TNF and the most preferred sequence (beginning with arg) used in the constructs. The most preferred sequence is from this amino terminal arg to the carboxyl terminal amino acid.

FIGS. 9A-E depicts examples of certain SCA-TNF and SCA-PLAP constructs (SEQ ID NOS: 12-18). Only certain fusion portions of the TNF, PLAP and SCA domains are depicted in the examples in 9A-9E. The V.sub.L domain is positioned in the example constructs as shown in the schematic in 9D.

FIG. 9A depicts an SCA-TNF construct (SEQ ID NOS:12-15) where the two amino terminal amino acid residues are removed from a genetically modified form of TNF and the truncated TNF is fused to CC49 sFv.

FIG. 9B depicts an SCA-TNF construct (SEQ ID NO:16) having the truncated TNF of FIG. 9A and a 10mer spacer.

FIG. 9C depicts an SCA-TNF construct (SEQ ID NO:17) having the truncated TNF of FIG. 9A and a spacer containing (His).sub.5 for metal ion purification of the protein.

FIG. 9D depicts a schematic of an SCA-PLAP construct where PLAP is connected to the SCA using a spacer. Similar constructs are provided by the invention using TNF instead of PLAP.

FIG. 9E depicts a schematic of an SCA-PLAP construct (SEQ ID NO:18) where PLAP is connected to the SCA via a spacer containing (His).sub.5 for metal ion purification of the protein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

I. Fusion Constructs

This invention relates to the discovery that single-chain and multivalent antigen-binding fusion proteins have significant utility beyond that of single-chain antigen-binding proteins. An antigen-binding fusion protein provides the binding capability of the antigen-binding protein combined with the immunoeffector or cytolytic function of the immunoeffector fusion partner or the cytolytic fusion partner.

The terms "antigen-binding fusion," "single-chain fusion," "single-chain antigen-binding fusion," "single-chain immunoeffector fusion," and "single-chain cytolytic fusion" describe fusion proteins that are structurally defined as having the binding portion of a first polypeptide from a variable region of an antibody, associated with the binding portion of a second polypeptide from a variable region of an antibody, the two polypeptides being joined by a peptide linker into a single polypeptide chain, and an immunoeffector or cytolytic polypeptide. The binding portions may associate to form a functional antigen-binding site, as in the case wherein the binding portions are from 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 immunoeffector fusion" or "single-chain antigen-binding cytolytic fusion." It is preferred that the immunoeffector or cytolytic polypeptide is selected from the group consisting of TNF, an immunoeffector or cytolytic fragment of TNF, PLAP, and an immunoeffector or cytolytic fragment of PLAP, and fused to the single-chain protein. It is most preferred in the TNF fusion constructs that a human TNF gene is used to derive the immunoeffector region of the construct (see Wang et al., Science 228:149-154 (1985) for an example of a sequence of a human TNF cDNA).

Alternatively, the binding portions in the fusion molecule may have unnaturally paired CDRs or may both be derived from the same kind of antibody chain, either heavy or light, in which case the resulting single-chain molecule may not display a functional antigen-binding fusion site. Two such fusion molecules may be combined to give a multivalent fusion molecule.

As used herein the term "immunoeffector" refers generally to a peptide, peptide fragment or peptidyl moiety capable of causing or modulating an immune response in an organism. The immunoeffector peptide, peptide fragment or peptidyl moiety useful in the fusion proteins of the invention include, for example, TNF, an immunoeffector fragment of TNF, IL-2, an immunoeffector fragment of IL-2, GM-CSF, an immunoeffector fragment of GM-CSF, PLAP, and an immunoeffector fragment of PLAP. The immune response caused or modulated by the immunoeffector peptide, peptide fragment or peptidyl moiety of the invention includes, for example, the infiltration of immune cells to the site of the peptide, peptide fragment or peptidyl moiety, such as, for example infiltration by T cells, B cells, macrophages and other lymphocytes. The immunoeffector compounds or moieties in the fusion molecules of the invention can also cause or modulate, for example, the activation of lymphocyte cells, the expression of lymphocyte-specific compounds, the elaboration of antibodies, the enhancement of phagocytosis by phagocytes, and the enhancement of tumor cell lysis.

As used herein the term "cytolytic," as used to refer to a peptide, refers generally to a peptide, peptide fragment or peptidyl moiety capable of causing or modulating cytolysis or cell killing. The cytolytic peptide, peptide fragment or peptidyl moiety useful in the fusion proteins of the invention include, for example, TNF, a cytolytic fragment of TNF, IL-2, a cytolytic fragment of IL-2, GM-CSF, a cytolytic fragment of GM-CSF, PLAP, and a cytolytic fragment of PLAP. The cytolysis process caused or modulated by the cytolytic peptide, peptide fragment or peptidyl moiety of the invention encompasses a host of biological effects, including, for example, the infiltration of cytolytic cells and factors to the site of the peptide, peptide fragment or peptidyl moiety, such as, for example T cells, NK cells, tumor infiltrating lymphocytes, macrophages and other lymphocytes. The cytolytic compounds or moieties in the fusion molecules of the invention can also cause or modulate, for example, direct killing of target cells, the activation of lymphocyte and killer cells, the expression of lymphocyte-specific compounds, the enhancement of phagocytosis by phagocytes, and the enhancement of tumor cell lysis.

It is preferred that the single-chain antigen binding proteins of the invention be constructed in one of three forms. The first form comprises a single-chain antigen binding molecule fused at its C terminus to a spacer which is fused to an immunoeffector or cytolytic protein moiety at the C terminus of the spacer, so that the structure will generally be: NH.sub.2 -V.sub.L -linker-V.sub.H -spacer-immunoeffector moiety-COOH or NH.sub.2 -V.sub.L -linker-V.sub.H -spacer-cytolytic moiety-COOH. The second form comprises the immunoeffector or cytolytic moiety fused to the N-terminus of the single-chain antigen binding protein, having the general structures. NH.sub.2 -immunoeffector moiety-spacer-V.sub.L -linker-V.sub.H -COOH or NH.sub.2 -cytolytic moiety-spacer-V.sub.L -linker-V.sub.H -COOH. The third general form will have an immunoeffector or cytolytic moiety within the linker joining the variable and variable light chains of the single-chain binding protein, following the general structure: NH.sub.2 -V.sub.L -linker-immunoeffector moiety-linker-V.sub.1 H, NH.sub.2 -V.sub.L -linker-immunoeffector moiety-V.sub.H -COOH, NH.sub.2 -V.sub.L -immunoeffector moiety-linker-V.sub.H -COOH, NH.sub.2 -V.sub.L -immunoeffector moiety-V.sub.H -COOH, NH.sub.2 -V.sub.L -linder-cytolytic moiety-linker-V.sub.H, NH.sub.2 -V.sub.L -linker-cytolytic moiety-V.sub.H -COOH, NH.sub.2 -V.sub.L -cytolytic moiety-linker-V.sub.H -COOH, or NH.sub.2 -V.sub.L -cytolytic moiety-V.sub.H -COOH.

II. Fusion Construct Linkers and Spacers

Linkers used in the fusion constructs of the invention can be any of those linkers known or used in the art. Skilled artisans will be able to determine the appropriate linker to be used for a particular construct. It is preferred that the linkage utilized in constructing antigen-binding fusion proteins of the invention that the linkers be selected from those disclosed in U.S. patent application Ser. No. 07/989,846.

It is preferred that the linkers utilized in constructing the antigen-binding fusion proteins of the invention are between 0 and 50 amino acids in length.

It also is preferred that the linkers are between 0 and 18 amino acids in length in the single-chain proteins within the multivalent forms, and between 18 and 50 amino acids in length for the single-chain molecules that will remain monomeric forms.

In some cases it may be necessary to separate the antigen-binding part of a fusion protein from the immunoeffector of cytolytic part of the fusion protein by a peptide spacer, in order to preserve both activities of the fusion protein. It is preferred that the spacers are between 0 and 50 amino acids in length.

It is further preferred that a spacer having a (histidine).sub.5 (herein "(His).sub.5 ") stretch be used in the single-chain fusion molecules of the invention. These (His).sub.5 spacer containing molecules will be easily purified by affinity purification using a column having bound metal ions, such as, for example zinc or nickel. This spacer can also be used in multivalent fusion molecules of the invention and can be used to purify multivalent constructs.

It is most preferred that the (His).sub.5 spacer have the sequence Gly Ser His His His His His Ser Gly (SEQ ID NO:2).

It is also more preferred that the (His).sub.5 spacer (shown in bold below) be inserted between a serine residue of CC49 V.sub.H and a glutamate residue of the PLAP moiety, so that the structure will be as follows: . . . (CC49) . . . Val Thr Val Ser Gly Ser His His His His His Ser Gly Glu Ser Pro Leu . . . (PLAP) . . . (SEQ ID NO:2).

It is also preferred in the fusion molecules of the invention that the spacers be between 2 and 10 amino acid residues in length. A preferred 2-mer spacer is Gly Ser and a preferred 10-mer spacer is Gly Ser Gly Lys Pro Gly Ser Gly Glu Gly (SEQ ID NO:11).

III. PLAP Antigen-binding Fusion Constructs

One of the principal problems in cancer therapy is the reduction of necrotic areas in cell tumors. Necrotic areas arise in tumors from the inability of macrophages to remove these dying cells. The inventors have discovered compounds and methods that will facilitate debulking by targeting activated macrophages to necrotic tissues. Tumor necrosis therapy using radiolabeled anti-histone monoclonal antibodies has been used to target dying cells (U.S. Pat. Nos. 5,019,368 and 4,861,581). The PLAP fusion molecules of the invention will have the advantages of single-chain antigen binding molecules described above.

The inventors have further discovered that PLAP is a potent activator of macrophages and will be useful as a tumor debulking agent when fused to single-chain antigen binding proteins. The ability of single-chain proteins to penetrate into tumors will enhance the effectiveness of a macrophage activating protein, such as, for example, PLAP.

Moreover, the PLAP single-chain antibody fusion proteins will be able to bind certain tumors and activate a localized immune response to the tumors.

The immunoeffector or cytolytic fragment of PLAP useful in the methods of the invention can be determined by measuring PLAP activity. The PLAP activity of the fusion proteins of the invention can be determined using any assay known in the art for measuring PLAP activity. It is preferred that the PLAP activity of the fusion proteins produced be measured using the previously described assay (Clark et al., Biochem. J. 250:125-132 (1988); Clark et al., J. Biol. Chem. 262:4402-4406 (1987); Clark et al., Proc. Natl. Acad. Sci. USA 88:5418-5422 (1991)). For example, the fusion proteins can be examined for their ability to stimulate phospholipase A.sub.2 activity in BC3H.sub.1 cell sonicates. Activation of phospholipase A.sub.2 can be plotted as the fold stimulation of the enzyme activity versus fusion protein concentration. From these data, the dose dependence of phospholipase A.sub.2, activity as a function of fusion protein concentration can be calculated. See, for example, Clark et al., J. Biochem. 261:10713-10718 (1986); Bomalaski et al., J. Immunol. 142: 3957-3962 (1989); Bomalaski et al., J. Lab. Clin. Med. 166:184-925 (1990)).

It is preferred that the PLAP fragment in the fusion proteins of the invention have a twenty-one amino acid peptide having the sequence Glu Ser Pro Leu Ile Ala Lys Val Leu Thr Thr Glu Pro Pro Ile Ile Thr Pro Val Arg Arg (SEQ ID NO:1).

Moreover, three basic designs are preferred for PLAP fusion proteins. One general design has a PLAP moiety at the C-terminus of a single-chain antigen binding molecule, one has a PLAP moiety at the N-terminus of the single-chain antigen binding molecule, and one has a PLAP moiety within the linker. It is most preferred that the first and second polypeptides of the single-chain antigen-binding molecule are derived from the CC49 monoclonal antibody (See Muraro et al., Can. Res. 48:4588-4596 (1988) for a description of the antibody).

As with all fusion molecules of the invention any of these PLAP fusion molecules can be used as monomeric subunits of multivalent molecules.

IV. TNF Antigen-Binding Fusion Constructs

At one time, the use of TNF showed promise as an anti-cancer therapeutic agent, but in clinical trials TNF has been shown to have severe toxicity. By targeting the TNF to tumor cells using a single-chain antigen binding molecule fused to an active moiety of TNF, lower doses of the TNF activity could be used, thereby avoiding or reducing toxicity.

It is preferred that fusion molecules having an inumunoeffector or cytolytic moiety at the C-terminus of the antigen-binding molecule be constructed in one of three general ways. The first structure has a ten amino acid residue spacer between the antigen-binding molecule and TNF (see FIG. 9B for example). The second general construct has a spacer containing a five histidine stretch (see FIG. 9C for example). The third general structure has a two amino acid residue spacer (see FIG. 9A for example). Other structures than depicted in FIG. 9 are provided by the invention. It is most preferred that the immunoeffector or cytolytic moiety in these three general structures be derived from TNF.

The crystal structure of TNF reveals that the side chain of the C-terminal Leu 157 is involved in the packing of the TNF trimer. The N-terminus of TNF is conformationally less restricted. Moreover, the first five amino acid residues of all three TNF molecules in the TNF trimer are disordered in the crystal structure. It has been shown that residues can be removed from the N-terminal of TNF and the resulting molecule will still maintain TNF activity. However, removal of residues from the C-terminus of TNF without a concomitant loss of activity has not been shown. Therefore, fusion molecules having the immunoeffector region of TNF are preferably derived from the C-terminal domain of TNF or from molecules having N-terminal deletions.

Expression of TNF in E. coli requires the deletion of the leader sequence (Wang et al., Science 228:149-154 (1985)). Thus it is preferred that the TNF fusion molecules of the invention have no signal sequence. Skilled artisans will be able to exploit the techniques for constructing active TNF fragments taught by Wang et al., Science 228:149-154 (1985) to make certain of the TNF fusion molecules of the invention. Skilled artisans will also be able to use this teaching as a starting point for the creation of other TNF fusion constructs within the scope of the invention.

In view of the observations regarding TNF structure and activity, it is preferred that the TNF fragment used as the fusion partner in the constructs of the invention lack the ultimate N-terminal residue (Val 77 in FIGS. 8A-B). The invention also provides a construct having the TNF sequence beginning with NH.sub.2 -Arg Ser Ser Ser Arg Thr Pro Ser Asp . . . (SEQ ID NO:15) fused to the carboxyl terminus of the single-chain antigen-binding protein (see FIGS. 9A-C (SEQ ID NOS:12-17), for example).

Another preferred construct has the immunoeffector or cytolytic region of TNF, or the TNF sequence beginning with NH.sub.2 -Arg Ser Ser Ser Arg Thr Pro Ser Asp . . . (SEQ ID NO:19) fused to the carboxyl terminus of a CC49 sFv construct, particularly a construct with a 2-mer or 10-mer spacer (see FIGS. 9A-B (SEQ ID NOS:12-16), for example).

Another preferred construction comprises a His.sub.5 sequence in the spacer useful for metal ion affinity purification. The construct comprises a TNF sequence beginning with NH.sub.2 -Arg Ser Ser Ser Arg Thr Pro Ser Asp . . . (SEQ ID NO:19) fused to the carboxyl terminus of the spacer, which is fused to the carboxy terminus of the single-chain antigen-binding protein (see FIG. 9C (SEQ ID NO:17), for example).

As with all fusion molecules of the invention any of these TNF fusion molecules can be used as monomeric subunits of multivalent molecules.

V. Multivalent Constructs

For the purposes of this application, "valent" refers to the numerosity of antigen binding sites. Thus, a bivalent protein refers to a protein with two binding sites. Enhanced binding and immunoeffector activity, bi- and multi-specific binding, and other novel uses of antigen-binding fusion proteins have been demonstrated or are envisioned here. Accordingly, the invention is directed to univalent and multivalent forms of antigen-binding fusion proteins, compositions of multivalent and univalent antigen-binding fusion proteins, methods of making and purifying multivalent and univalent forms of antigen-binding fusion proteins, and new and improved uses for multivalent forms of antigen-binding fusion proteins. The invention provides an antigen-binding fusion protein having at least one single-chain immunoeffector protein molecule, each single-chain immunoeffector molecule having a first polypeptide having the binding portion of the variable region of an antibody heavy or light chain; a second polypeptide having the binding portion of the variable region of an antibody heavy or light chain; a peptide linker linking the first and second polypeptides into a single-chain protein and an immunoeffector polypeptide selected from the group consisting of TNF, an immunoeffector or cytolytic fragment of TNF, PLAP, and an immunoeffector or cytolytic fragment of PLAP, and fused to the antigen-binding protein.

VI. Constructs Having More Than One Immunoeffector Moiety

A. Single-Chain Constructs

Provided by the present invention are single-chain antigen-binding fusion proteins further having more than one immunoeffector polypeptide. It is preferred that these single-chain antigen-binding fusion proteins have two immunoeffector polypeptides, particularly combinations including two immunoeffector regions of PLAP, two immunoeffector regions of TNF, and one immunoeffector region of TNF and one immunoeffector region of PLAP fused onto the same single-chain antigen-binding fusion protein.

B. Multivalent Constructs

The invention provides any assemblage, covalently or non-covalently joined, of two or more single-chain immunoeffector proteins, the assemblage having more than one antigen-binding site. The single-chain proteins composing the assemblage may have antigen-binding activity, or they may lack antigen-binding activity individually but be capable of assembly into active immunoeffector antigen-binding fusion proteins. Moreover, multivalent molecules may have single-chain proteins all of which are fused to an immunoeffector polypeptide or certain of which are not fused to an immunoeffector polypeptide. Different immunoeffector polypeptides may be present on individual single-chain proteins constituting a multivalent molecule. For example, a multivalent molecule may be comprised of a first single-chain protein fused to an immunoeffector portion of TNF, a second single-chain protein fused to an immunoeffector portion of PLAP, and a third non-fusion single-chain protein. The term "multivalent" encompasses bivalent, trivalent, tetravalent, etc. It is envisioned that forms above bivalent may be useful for certain applications. The multivalent antigen-binding protein molecule is more fully described in U.S. patent application Ser. No. 07/989,846.

A preferred form of the immunoeffector antigen-binding fusion protein comprises bivalent proteins, including heterobivalent and homobivalent forms. The term "bivalent" means an assemblage of single-chain proteins associated with each other to form two antigen-binding sites. The term "heterobivalent" indicates antigen-binding fusion proteins that are bispecific molecules capable of binding to two different antigenic determinants. Therefore, heterobivalent proteins have two antigen-binding sites that have different binding specificities. The term "homobivalent" indicates that the two binding sites are for the same antigenic determinant.

Homobivalent and heterobivalent forms may be comprised of a single-chain protein, each of which is fused to an immunoeffector polypeptide, as well as molecules having two single-chain proteins only one of which is fused to an immunoeffector polypeptide. For example, heterobivalent and homobivalent molecules may have a first single-chain protein fused to an immunoeffector portion of TNF and a second single-chain protein fused to an immunoeffector portion of PLAP, molecules having single-chain proteins each of which are fused to an immunoeffector region of TNF or PLAP, and molecules having single-chain proteins only one of which is fused to an immunoeffector polypeptide, particularly an immunoeffector portion of TNF or PLAP.

Without being bound by any particular theory, the inventors speculate on several models which can equally explain the phenomenon of multivalence in antigen-binding fusion proteins. The inventors' models are presented herein for the purpose of illustration only, and are not to be construed as limitations upon the scope of the invention. The invention is useful and operable regardless of the precise mechanism of multivalence.

FIG. 1 depicts the first hypothetical model for the creation of a protein, the "Association" model. FIG. 1A shows two monovalent single-chain antigen-binding fusion proteins, each composed of a V.sub.L, a V.sub.H, and a linker polypeptide covalently bridging the two. Each monovalent single-chain antigen-binding fusion protein is depicted having an identical antigen-binding fusion site containing antigen. FIGS. 1B and 1C show the simple association of the two single-chain antigen-binding fusion proteins to create the bivalent form of the protein. It is hypothesized that simple hydrophobic forces between the monovalent fusion proteins are responsible for their association in this manner. The monovalent units retain their original association between the V.sub.H and V.sub.L regions. Only one of the molecules depicted in FIG. 1C is a fusion molecule. Any number of the single-chain monomeric subunits in a multivalent molecule can be fused to a fusion partner.

An alternative model for the formation of antigen-binding fusion proteins is shown in FIGS. 3A and 3B. This "Rearrangement" model hypothesizes the dissociation of the variable region interface by contact with dissociating agents such as guanidine hydrochloride, urea, or alcohols such as ethanol, either alone or in combination. Combinations and relevant concentration ranges of dissociating agents are recited in the discussion concerning dissociating agents in U.S. patent application Ser. No. 07/989,846. Subsequent re-association of dissociated regions allows variable region recombination differing from the starting single-chain proteins, as depicted in FIGS. 3A and 3B. The homobivalent fusion antigen-binding fusion protein of FIG. 3A is formed from parent single-chain antigen-binding fusion proteins similar to those shown in FIG. 1A. The recombined bivalent protein has V.sub.L and V.sub.H from the parent monovalent single-chain proteins. The homobivalent fusion protein of FIG. 3A is a depicted as a fully functional monospecific bivalent protein capable of actively binding two antigen molecules.

FIG. 3B shows the formation of heterobivalent antigen-binding fusion proteins via the Rearrangement model. FIG. 3B shows a pair of single-chain proteins, one having two V.sub.L and one having two V.sub.H. These single-chain proteins have reduced or no ability to bind antigen because of the mixed nature of their antigen-binding sites, and thus are made specifically to be assembled into proteins through this route. FIG. 3B shows the heterobivalent antigen-binding fusion protein formed whereby the variable regions of the parent proteins are shared between the separate halves of the heterobivalent protein. The Rearrangement model also explains the generation of proteins of a higher order than bivalent, as it can be appreciated that more than a pair of single-chain proteins can be reassembled in this manner.

Either the Rearrangement or that Association model can be used to explain the fusion constructs wherein the multivalent molecules are formed by binding between the fusion partner moieties. A specific example of this general multivalent fusion protein is depicted in FIG. 3C. Skilled artisans will immediately recognize that many such multivalent proteins can be constructed using moieties from proteins that are multimeric as the fusion partner. For example, TNF is active as a trimer. An embodiment of the TNF fusion constructs of the invention provides a trivalent molecule that forms a trimer by bonding between the TNF moieties. This type of structure is schematically represented by FIG. 3C.

The limitations of two-dimensional images of three-dimensional objects must be taken into account when considering the structures in the figures. Thus, the actual spatial arrangement of proteins can be expected to vary somewhat from these figures.

VII. Methods of Use of Antigen-Binding Fusion Proteins

The present invention provides uses for treating physiological conditions, such as cancer, by targeting the activities of TNF and PLAP.

The invention also extends to uses for the antigen-binding fusion proteins in purification and biosensors. Affinity purification is made possible by affixing the antigen-binding fusion protein to a support, with the antigen-binding fusion 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 fusion molecule, with subsequent processing of the signal. Immunoeffector antigen-binding fusion proteins, when used as the antigen-binding fusion molecule in biosensors, may change conformation upon binding, thus generating a signal that may be detected.

Essentially all of the uses for which monoclonal or polyclonal antibodies, or fragments thereof, have been envisioned by the prior art, can be addressed by the proteins of the present invention. These uses include detectably-labelled forms of the protein. Types of labels are well-known to those of ordinary skill in the art. They include radiolabelling, chemiluminescent labeling, fluorochromic labelling, and chromophoric labeling. Other uses include imaging the internal structure of an animal (including a human) by administering an effective amount of a labelled form of the protein and measuring detectable radiation associated with the animal. They also include improved immunoassays, including sandwich immunoassay, competitive immunoassay, and other immunoassays wherein the labelled antibody can be replaced by the antigen-binding fusion protein of this invention. See, for example, Kohler et al., 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, (Second Edition), Cold Spring Harbor Labs (1989).

VIII. Genetic Constructs and Gene Expression

The invention also includes a DNA sequence encoding single-chain antigen-binding fusion proteins that can be expressed in a variety of hosts. The genes can be expressed as protein which can be isolated and folded using any method known in the art. It is preferred that the fusion molecules by made as described in U.S. patent application Ser. No. 07/989,846 or U.S. Pat. No. 5,260,203.

Synthesis of DNA sequences is well know in the art, and possible through at least two routes. First, it is well-known that DNA sequences may be synthesized through the use of automated DNA synthesizers de novo, once the primary sequence information is known. Alternatively, it is possible to obtain a DNA sequence coding for a single-chain antigen-binding fusion protein by removing the stop codons from the end of a gene encoding a single-chain antigen-binding protein, and then inserting a spacer and a gene encoding an immunoeffector protein. Example 1 demonstrates the construction of a DNA sequence coding for a single-chain immunoeffector antigen-binding fusion protein. Other methods of genetically constructing single-chain immunoeffector antigen-binding fusion proteins come within the spirit and scope of the present invention.

The transformed cells will be of particular use in expressing significant quantities of immunoeffector antigen-binding fusion proteins which are useful in the immunological methods of the invention (see Example 2). Moreover, one skilled in the art will realize that the fusion proteins of the invention may be readily adapted to many methods known and employed in the art in order to further analyze the effects of the fusion proteins on tumors and tumor cell, and to study the structure of the fusion proteins. For example, the cells lines of the invention can be used with large-scale fermentation apparatus to achieve high yields of protein useful for many purposes, such as, for example, the formation of crystals for crystallographic studies (see, generally, Van Holde, Physical Biochemistry, Prentice-Hall, NJ (1972)) and the rational design of therapeutic agents.

IX. Methods of Making Antigen-Binding Fusion Proteins

Single-chain antigen-binding fusion proteins of the invention can be made by any process, but preferably according to the process for making single-chain antigen-binding proteins set forth in U.S. Pat. No. 4,946,778. Briefly, that patent pertains to a single polypeptide chain antigen-binding molecule which has binding specificity and affinity substantially similar to the binding specificity and affinity of the aggregate light and heavy chain variable regions of an antibody, to genetic sequences coding therefore, and to recombinant DNA methods of producing such molecules, and uses for such molecules. The single-chain protein produced by the methodology in U.S. Pat. No. 4,946,778 comprises two regions linked by a linker polypeptide. The two regions are termed the V.sub.H and V.sub.L regions, each region having one half of a functional antigen-binding fusion site.

Multivalent antigen-binding fusion proteins of the invention can be made by any process, but preferably according to the process for making multivalent antigen-binding proteins set forth in U.S. patent application Ser. No. 07/989,846.

The use of the term "substantially free" when used to describe a composition of multivalent single-chain antigen-binding fusion protein molecules means the lack of a significant peak corresponding to the single-chain molecule, when the composition is analyzed by cation exchange chromatography (see U.S. patent application Ser. No. 07/989,846 for a description of these techniques).

Having now generally described this invention the same will better be understood by reference to certain specific examples which are included for purposes of illustration and are not intended to limit it unless otherwise specified.

EXAMPLE 1

Genetic Construction of CC49/212 SCA with C-Terminal PLAP Moiety

Gene constructions of CC49/212 SCA with a PLAP C-terminus were achieved by ligating a synthetic DNA segment corresponding to the encoded PLAP peptide at the 3' end of the CC49/212 gene. Six consecutive oligonucleotides ranging in size from 24 to 29 bases were synthesized on an ABI DNA synthesizer. These oligonucleotides were designed to encode the PLAP peptide in two sets of complementary sequences with three oligonucleotides on each strand of the duplex DNA segment. The complete synthetic fragment with the six annealed oligonucleotides will contain one single stranded overhang corresponding to a cleaved BstEII restriction site, and one single stranded overhang corresponding to a cleaved BamHI restriction site. This strategy allows the direct ligation of the segment into an existing CC49/212 gene which bears these restriction sites at the appropriate locations as seen in FIGS. 4A-B. The oligonucleotides were phosphorylated with ATP plus T4 polynucleotide kinase; annealed to form the duplex fragment by heating the solution to 95.degree. C. for 2 min following by slow cooling to 22.degree. C.; and the synthetic segment was treated with T4 DNA ligase plus the purified CC49/212 M13 vector which also had been digested with BstEII plus BamHI. The ligations were transformed into E. coli GX1210 and recombinant plaques were confirmed to have the desired sequence by dideoxy DNA sequencing.

The pGX5410 expression vector contains a bacteriophage OL/PR promoter followed by a signal peptide derived from the E. coli ompA gene. The AatII-BamHI fragment from the confirmed CC49/212/PLAP gene construction in M13 was excised by restriction endonuclease digestion, purified by gel electrophoresis on FMC agarose, and ligated into plasmid pGX5410 which had also been digested with AatII plus BamHI. The ligated vector was transformed into competent E. coli GX6712 and transformants were analyzed for gene expression using the methods of Whitlow and Filpula, Methods, Companion Methods Enzymol. 2:97-105 (1991).

EXAMPLE 2

Transformation of Bacteria With PLAP Fusion Genetic Construct

Gx8962 is a construct having CC49/212 with the twenty-one amino acid of the PLAP fragment attached to the C-terminus of the CC49 at the Bst EII restriction site. Gx8963 is CC49 with the twenty-one amino acid PLAP fragment substituted as the linker between the light chain and heavy chain of CC49. These constructs were created essentially as described in Example 1.

E. coli strains transformed with these expression vectors were grown in LB with fifty micrograms per ml ampicillin at 30.degree. C. to mid-log phase, and induced at 42.degree. C. for one hour.

Cell lysates were prepared using standard techniques and run on 14% Tris-glycine acrylamide gels. BRL high molecular weight standards were utilized on these gels. The gel was loaded so that lysates from cells before induction could be compared with lysates from cells following induction for one hour at 42.degree. C. Expression was demonstrated for constructions Gx8962 and Gx8963.

EXAMPLE 3

Tag-72 Binding Activity of PLAP Fusion SCAs By Competition ELISA

The CC49 monoclonal antibody was developed by Dr. Jeffrey Schlom's group at the U.S. National Cancer Institute. This antibody binds specifically to the pan-carcinoma tumor antigen TAG-72. See Muraro et al., Can. Res. 48:4588-4596 (1988).

To determine the binding properties of the SCA-PLAP fusion proteins, a competition radioimmunoassay (RIA) was set up in which a CC49 IgG labeled with I-125 is competed against unlabeled SCA-PLAP fusions (CC49/212 C-terminus) for binding to TAG-72 on a human breast carcinoma extract. This competition RIA was used to determine if the fusion SCAs bind to the TAG-72 antigen. FIG. 7 illustrates that PLAP No. 1 and PLAP No. 2 efficiently bind the TAG-72 antigen as compared to positive control, CC49 IgG and SCA CC49/218. PLAP No. 1 and PLAP No. 2 are two purified CC49/212 PLAP C-terminus clones.

All publications cited herein are incorporated fully and in their entirety into this disclosure by reference.

From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention and the following claims. As examples, the steps of the preferred embodiment constitute only one form of carrying out the process in which the invention may be embodied.

Claims

What is claimed is:

1. An isolated nucleic acid molecule which codes for an immunoeffector antigen-binding fusion protein comprising: (a) a first polypeptide comprising the binding portion of the variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the binding portion of the variable region of an antibody heavy or light chain; (c) a peptide linker linking said first and second polypeptides (a) and (b) into a single-chain molecule; and, (d) an immunoeffector polypeptide fused to at least one of said polypeptide of (a), (b) or said peptide (c), wherein the immunoeffector is Phospholipase A activating protein.

2. An isolated nucleic acid molecule which codes for a cytolytic antigen-binding fusion protein comprising: (a) a first polypeptide comprising the binding portion of the variable region of an antibody heavy or light chain; (b) a second polypeptide comprising the binding portion of the variable region of an antibody heavy or light chain; and (c) a peptide linker linking said first and second polypeptides (a) and (b) into said single-chain molecule; and, (d) a cytolytic polypeptide fused to at least one of said polypeptide (a), (b) or said peptide (c); wherein the cytolytic polypeptide is Phospholipase A activating protein.

3. An isolated nucleic acid molecule which codes for a single-chain fusion protein comprising: (a) a first polypeptide comprising the V.sub.L or V.sub.H of a CC49 monoclonal antibody; (b) a second polypeptide comprising the V.sub.L or V.sub.H of a CC49 monoclonal antibody; (c) a peptide linker linking a first and second polypeptides (a) and (b) into a single-chain protein; and, (d) an immunoeffector polypeptide fused to at least one polypeptide of (a), (b) or peptide (c), wherein said immunoeffector is Phospholipase A activating protein.

4. A DNA molecule comprising the isolated nucleic acid molecule of any one of claim 1, 2, or 3 and a vector.

5. A host cell transformed with the DNA molecule of claim 4.

6. The isolated nucleic acid molecule according to claim 1, wherein said immunoeffector antigen-binding fusion protein further comprises TNF or an immunoeffector fragment of TNF fused to at least one of said polypeptides (a), (b), said peptide (c), or said immunoeffector polypeptide.

7. The isolated nucleic acid molecule according to claim 2, wherein said cytolytic antigen-binding fusion protein further comprises TNF or an immunoeffector fragment of TNF fused to at least one of said polypeptides (a), (b), said peptide (c), or said cytolytic polypeptide.

8. The isolated nucleic acid molecule according to claim 3, wherein said single-chain fusion protein further comprises TNF or an immunoeffector fragment of TNF fused to at least one of said polypeptides (a), (b), said peptide (c), or said immunoeffector polypeptide.

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