WO1994003629A9

WO1994003629A9 - Monoclonal antibodies specific for 3',6'-isold1 ganglioside

Info

Publication number: WO1994003629A9
Application number: PCT/US1993/007302
Authority: WO
Filing date: 1993-07-29
Publication date: 1994-04-28

Abstract

Monoclonal antibodies which bind to the ganglioside IV3NeuAc, III6NeuAc-LcOse¿4?Cer (3',6'-isoLD1), are disclosed, along with methods of making the same and diagnostic and therapeutic methods of using the same. Particularly preferred are monoclonal antibodies which bind to a 3',6'-isoLD1 epitope selected from the group consisting of NeuAcα2-3Galβ1-3NeuAcα2-6GlcNAc and NeuGcα2-3Galβ1-3NeuGcα2-6GlcNAc.

Description

MONOCLONAL ANTIBODIES SPECIFIC FOR 3 ¹ , 6 ' - ISOLDI GANGLIOSIDE

Field of the Invention

This invention relates to monoclonal antibodies directed to the lactotetraose ganglioside 3' ,6'-isoLDl.

Background ofthe Invention Targeting of quantitatively increased "normal" ganglioside epitopes on tumor cells has been shown to be effective for both localizing [GD2, GM3] and therapeutic [GD3; GD2] applications. See J. Heiner et al.. Cancer Res. 47, 5377-5381 (1987); T. Dohi et al., Cancer Res . 48, 5680- 5685 (1988); A. Houghton et al., Proc. Natl . Acad. Sci . USA 82, 1242-1246 (1985); R. Herberman et al. , in Monoclonal .Antibodies and Cancer Therapy 193-203 (R. Reisfeld and S. Sell eds. 1985); R. Irie and D. Morton, Proc. Natl . Acad. Sci . USA 83, 8694-8698 (1986); A. Yu et al., Proc. Am. Assoc. Cancer Res . 32, 263 (1991) (abstr.).

Despite these promising studies, the capacity for uptake by nontarget normal tissues remains; this is especially crucial within the CNS, a "ganglioside-rich" environment. See P. Fredman et al., J. Neurochem. 50, 912- 919 (1988) . For this reason, the discrimination of CNS tumor-associated gangliosides with negligible expression by components of the normal adult neuraxis as eventual targets for compartmental, intrathecal administration has been actively pursued. We and others have described the expression of the lactotetraose series gangliosides IV³NeuAcLcOse₄Cer (3'-isoLMl) and IV³NeuAc,III⁶NeuAc- LcOse₄Cer (3' ,6'-isoLDl) by human tumors, derived xenografts, and fetal tissues; the presence of the 3',6'- isoLDl epitope on undefined carrier molecules in the serum of human cancer patients has been reported. See P. Fredman et al., supra ; J.-E. Mansson et al., FEBS Lett. 201, 109- 113 (1986); O. Nilsson et al., FEBS Lett. 182, 398-402 (1985); M. Fukuda et al., J. Biol . Chem. 261, 5145-5153 (1986); Y. Fukushi et al.. Biochemistry 25, 2859-2866 (1986); R. Kannagi et al., Cancer Res . 48, 3856-3863 (1988) . We have recently described a monoclonal antibody (MAb) specific for 3'-isoLMl (SL-50) and investigated the distribution of this antigen in human tumors of the CNS and in xenografts and cultured cell lines derived therefrom. See C. Wikstrand et al., J. Neuropathol . Exp. Neurol . 50, 756-769 (1991). The expression of both 3'-isoLMl and 3' ,6'-isoLDl within the human CNS is associated with periods of intense astroglial proliferation occurring in the fetal human forebrain through the first trimester, gradually disappearing after the age of two years. See L. Svennerholm et al., Biochim. Biophyε. Acta 1005, 109-117 (1989) . The ready detection of elevated amounts of these gangliosides in the brain tissue of children succumbing to polyunsaturated fatty acid lipidosis as compared with undetectable levels in age-matched (2-20 years) negative controls (L. Svennerholm et al., J. Neurochem. 49, 1772- 1783 (1987)) has led to the suggestion that 3'-isoLMl and 3 ',6'-isoLDl may be characteristic gangliosides of proli- ferative astroglial cells.

The monoclonal antibody FH9, which binds to 3 ',6'-isoLDl, is described in Y. Fukushi et al., Biochemistry 25 , 2859-2866 (1986). The ganglioside 3 ' ,6' ,8'-isoLTl is described in

L. Svennerholm et al., J. Neurochem . 49, 1772-1783 (1987). The distribution of 3'-isoLMl in tumors of the CNS has been approached through the use of the specific MAb SL-50 (C. Wikstrand et al. , supra) . The reactivity of DMAb-14 for both the monosialyl and disialyl forms precluded its definitive use in immunohistochemistry, thus the distribution of 3• ,6'-isoLDl in human tumors has not heretofor been directly addressed.

Summary ofthe Invention A first aspect of the present invention is a monoclonal antibody which binds to the ganglioside IV³NeuAc,III⁶NeuAc-LcOse₄Cer (3 ' ,6^»-isoLDl) . Preferably the antibody does not bind to the ganglioside IV³NeuAc-LcOse_ACer (3'-isoLMl). More preferably, the antibody also does not bind to the ganglioside IV³NeuAc₂-III⁶NeuAcLcOse₄-Cer (3' ,6' ,8'-isoLTl) . Still more preferably, the antibody has the binding characteristics set forth in Figure 2 and/or Figure 5 herein. Most preferably, the antibody binds to a 3',6'-isoLDl epitope selected from the group consisting of NeuAcα-2-3Gal)31-3NeuAcα2-6GlcNAc and NeuGcα2-3Gal/3l- 3NeuGcα2-6GlcNAc. Antibodies of the invention may be coupled to a detectable group or therapeutic agent, as described in detail below. Accordingly, further aspects of the present invention is the diagnosis and treatment of diseases employing the monoclonal antibodies described herein.

A second aspect of the present invention is a pharmaceutical formulation comprising a monoclonal antibody as given above in a pharmaceutically acceptable carrier.

A third aspect of the present invention is a method for detecting the presence of cancer in a human or animal subject. The method comprises contacting a sample (e.g., a tissue sample, a biological fluid) from a subject with an antibody as disclosed herein under conditions permitting the antibody to form a reaction product, and then detecting the presence or absence of the reaction product. The method is particularly useful for detecting gliomas. The method may be used to monitor the progression of treatment in a patient previously diagnosed as having cancer or may be used to screen patients who have not been previously diagnosed as having cancer. A fourth aspect of the invention is a method of treating cancer in a human or animal subject. The method comprises administering to the subject an antibody as described herein in an amount effective to combat the cancer. Any cancer for which 3' ,6'-isoLDl is a marker (e.g., where this ganglioside is expressed in greater amounts by the cancer cells than by healthy cells) may be treated by this method.

A fifth aspect of the invention is a method of making antibodies as described hereinabove. The method comprises administering an animal xenograft cells, wherein said xenograft cells express the ganglioside 3 ' ,6'-isoLDl, for a time and in an amount effective to produce antibodies which bind to the ganglioside 3' ,6'-isoLDl. The method optionally, but preferably, further includes the step of collecting spleen cells from said animal following said immunizing step, and fusing said spleen cells with a continuous cell line to produce a hybridoma cell line, which hybridoma cell line produces monoclonal antibodies as described above. A sixth aspect of the invention is a monoclonal antibody-producing cell line which produces an antibody as given above. Such cell lines may, for example, be hybridoma cell lines or Eεcherichia coli cell lines.

A seventh aspect of the invention is a method of making a monoclonal antibody as given above, comprising: culturing a cell line as described above in a culture medium under conditions suitable for the production of monoclonal antibodies, and collecting the monoclonal antibody from the culture medium. The foregoing and other objects and aspects of the present invention are explained in greater detail in the drawings herein and the specification set forth below. Brief Description of the Drawings

Figure 1 presents a specificity analysis of antibodies of the present invention with defined gangliosides/glycolipids. Symbols are as follows: open squares — galactose; open diamonds — N-acetylglucosamine; filled squares — glucose; open circles — galactosamine; filled triangle with stem — N-acetylneuraminic acid; filled circle with stem — fucose; "~" — βl-4 linkage.

^**3'-LMl refers to IV³NeuAcnLc0se₄CER, with /31-4Gal-N- Acetylglucosamine linkage (~) , as opposed to 3'isoLMl, or

IC³NeuAcLcOSE₄Cer, with Sl-3 Gal-N-Acetylglucosamine linkage

Figure 2 illustrates the epitope bound by antibodies of the invention. Symbols are as given in connection with Fig. 1 above, with open triangles with stems being used to designate N-glycolylneuraminic acid.

Figure 3 shows the reactivity of DMAb-21 and DMAb-22 for primary CNS tumors; immunohistochemistry of acetone-fixed, frozen sections. All MAbs were tested at 5 μg/ml. (a) TB 116, glioblastoma multiforme, DMAb-22, 520X. Diffuse pattern; intense staining of nearly all neoplastic cells, (b) TB 121, glioblastoma multiforme, DMAb-22, 400X. Intense staining of neoplastic gemistocytic cell bodies and processes. (c) TB 65, gliosarcoma, DMAb-22, 170X. Staining of neoplastic glial element and lack of staining of sarcomatous component. (d) TB 69, giant cell glioblastoma, DMAb-21, 400X. Intense staining of neoplastic giant cells.

Figure 4 shows the reactivity of DMAb-21 and DMAb-22 for non-CNS malignancies; immunohistochemistry of acetone-fixed, frozen sections. All MAbs were used at a concentration of 5 μg/ml. (a) and (b) TB 273, teratoma, 250X: (a) MOPC-104E, negative control primary antibody; (b) DMAb-22. Mesenchymal components stain intensely, as contrasted with the total absence of staining of the epithelial component. (c) and (d) B87-321, leiomyosarcoma, 250X: (c) MOPC-104E negative control primary antibody; (d) DMAb-21. Intense staining of neoplastic cells. (e) B87-66, breast carcinoma, 520X, DMAb-21. Intense staining of a focus of breast carcinoma cells. (f) TB 379, germinoma, 350X, DMAb-21. Intense staining of large neoplastic cellular component and absence of staining of infiltrative lymphocytes.

Figure 5 provides additional information on the binding characteristics of monoclonal antibodies of the present invention. Symbols used are as given above.

Detailed Description of the Invention

Ganglioside designations used herein are according to IUPAC Commision on Biochemical Nomenclature recommendations and Svennerholm, (see IUPAC-IUB Commission on Biochemical Nomenclature, Eur. J. Biochem. 79, 11-21 (1977); L. Svennerholm, J. Neurochem. 10, 613-623 (1963)): GD2, II³(NeuAc)₂GgOse₃Cer; GM3, II³NeuAc-LacCer; GD3, II³(NeuAc)₂LacCer; 3'-isoLMl, IV³NeuAcLc0se₄Cer; 3',6'- isoLDl, IV³NeuAc , III⁶NeuAcLcOse^Cer ; GDlb, II³(NeuAc)₂Gg0se₄Cer; 3'-LMl, IV³NeuAcnLcOse_/,Cer; 3',8'-LDl, IV³(NeuAc)₂nLc0se₄Cer; GM2, II³NeuAcGg0se₃Cer; GM1, II³NeuAcGgOse₄Cer; GDla, II³NeuAc,IV³NeuAcGgOse₄Cer; GM1, II³NeuAcGgOse₄Cer; GTlb, IV³NeuAcII³(NeuAc)₂GgOse₄Cer; Other abbreviations as used herein are as follows: CNS, central nervous system; MAb, monoclonal antibody; HPTLC, high- performance thin-layer chromatography.

It will be appreciated that, while the present invention is described primarily with respect to the diagnosis and treatment of humans subjects below, the invention can also be adapted to the diagnosis and treatment of animal subjects (e.g. , dog, cat) for veterinary purposes, and that the treatment of animal subjects is also an aspect of the present invention.

A. Antibodies and Cell Lines

The term "antibodies" as used herein refers to all types of immunoglobulins, including IgG, IgM, IgA, IgD, and IgE. Of these, IgM and igG are preferred, and IgM are particularly preferred. The antibodies may be of any species of origin, including (for example) mouse, rat, rabbit, horse, or human, or may be chimeric antibodies. See, e. g. , M. Walker et al., Molec. Immunol . 26, 403-11 (1989) . The term "antibody" as used herein includes antibody fragments which retain the capability of binding to a target antigen, for example. Fab, F(ab')₂, and Fv fragments, and the corresponding fragments obtained from antibodies other than IgG. Such fragments can be produced by known techniques.

Antibodies of the invention are made by administering an animal (e.g. , a mouse) xenograft cells, wherein the xenograft cells express the ganglioside 3',6'- isoLDl. Xenograft cells are produced by implanting tumor cells which express the ganglioside 3',6'-isoLDl in a suitable immunocomprised host animal (e.g., a nude mouse). The tumor cells may be, for example, human glioma cells or human embryonal carcinoma (teratoma) cells which express 3',6'-isoLDl. Appropriate tumor cells are routinely found, and the expression of 3',6'-isoLDl by such tumor cells is determined in accordance with standard techniques, such as thin layer chromatography or gas chromatography-mass spectroscopy. A specific example of a suitable tumor cell is the embryonal carcinoma cell line PA1, available from the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Maryland USA as ATCC CRL #1572.

The xenograft host is implanted with tumor cells in accordance with standard techniques. After a sufficient tumor cell mass is obtained in the xenograft host, the xenograft cells are harvested from the host and disaggregated (e.g. , by trypsinization) , suspended in a suitable carrier (e.g., a tissue culture medium which maintains the cells alive) , and administered by intraperitoneal injection for a time and in an amount effective to produce antibodies which bind to the ganglioside 3',6'-isoLDl (i.e., a first injection followed by a prolonged series of separate booster injections) . For example, the cells may be administered in a series of 6 to 7 separate injections, carried out separately over a period of about 200 days, with the cells being administered in an amount of from about .8 x 10⁷ to 1.2 x 10⁷ per injection as a suspension in from about .25 to .75 illiliters of tissue culture medium.

Once an animal producing antibodies has been obtained as described above, monoclonal antibodies used to carry out the present invention may be produced in a hybridoma cell line according to the technique of Kohler and Milstein, Nature 265, 495-97 (1975). In general, the animal producing the antibodies is sacrificed and spleen cells obtained therefrom. The spleen cells are then immortalized by fusing them with a continuous cell line (e.g., myeloma cells or lymphoma cells), typically in the presence of polyethylene glycol, to produce hybridoma cells. The hybridoma cells are then grown in a suitable media and the supernatant screened for monoclonal antibodies having the desired specificity as given herein. Accordingly, a further aspect of the present invention is to provide hybridomas which produce antibodies against an antigen found on 3 ',6'-isoLDl. The antigen can be NeuAcα2- 3Gal/31-3NeuAcα2-6GlcNAcorNeuGc 2-3Gal3l-3NeuGcα2-6GlcNAc, and is yet another aspect of the invention.

The monoclonal antibodies may be recombinant monoclonal antibodies produced according to the methods disclosed in Reading U.S. Patent No. 4,474,893, or Cabilly et al., U.S. Patent No. 4,816,567. The antibodies may also be chemically constructed by specific antibodies made according to the method disclosed in Segel et al., U.S. Patent No. 4,676,980 (Applicants specifically intend that the disclosure of all U.S. patent references cited herein be incorporated herein by reference) . Monoclonal antibodies may be chimeric antibodies produced in accordance with known techniques. The monoclonal antibodies may be complementarity determining region-grafted antibodies (or "CDR-grafted antibodies") produced in accordance with known techniques.

Monoclonal Fab fragments may be produced in Escherichia coli by recombinant techniques known to those skilled in the art. See, e. g. , W. Huse, Science 246, 1275- 81 (1989).

B. Subjects

The method disclosed herein may be employed with subjects suspected of having cancer (e.g., cancer of the colon, breast, stomach, pnacreas, biliary tract, or ovary, or patients afflicted with teratomas or pancreatic adenocarcinomas) , particularly patients suspected of having embryonal carcinomas or gliomas of the central nervous system (CNS) . The method may be employed both to monitor subjects who have been previously diagnosed as having cancer, and to screen subjects who have not been previously diagnosed as having cancer.

Gliomas are described in D. Russell and L. Rubinstein, Pathology of Tumors of the Nervous System , pp. 83-289 (1989) (Williams and Wilkins) , and include (but are not limited to) astrocyto as and glioblastoma multiforme.

Embryonal carcinomas (or "teratomas") , are described in Blaustein * s Pathology of the Female Genital Tract, pp. 679-692 (R. Kurman Ed., 3d ed. 1987) (Springer Verlag, NY) .

In a particular embodiment of the methods described herein, the subject has been previously diagnosed as having cancer, and possibly has already undergone treatment for cancer, and the method is employed to monitor the progression of either that cancer or the treatment thereof. For example, samples may be collected from subjects who have received initial surgical treatment for ovarian cancer and subsequent treatment with antineoplastic agents for that cancer to monitor the progress of the treatment. Samples taken from human subjects for use in the methods disclosed herein may be biological fluids such as serum, blood plasma, or ascites fluid. Serum is presently preferred. In the alternative, the sample taken from the subject can be a tissue sample (e.g., biopsy tissue; scrapings; ovarian tissue removed during surgery; etc.).

C. Immunoassav Formats

Assays carried out in accordance with the present invention may be homogeneous assays or heterogeneous assays. In a homogeneous assay the immunological reaction usually involves the specific antibody as disclosed herein, a labeled analyte, and the sample of interest. The signal arising from the label is modified, directly or indirectly, upon the binding of the antibody to the labeled analyte. Both the immunological reaction and detection of the extent thereof are carried out in a homogeneous solution. Immunochemical labels which may be employed include free radicals, radioisotopes, fluorescent dyes, enzymes, bacteriophages, coenzymes, and so forth.

In a heterogeneous assay approach, the reagents are usually the specimen, the antibody of the invention, and means for producing a detectable signal. Similar specimens as described above may be used. The antibody is generally immobilized on a support, such as a bead, plate or slide, and contacted with the specimen suspected of containing the antigen in a liquid phase. The support is then separated from the liquid phase and either the support phase or the liquid phase is examined for a detectable signal employing means for producing such signal. The signal is related to the presence of the analyte in the specimen. Means for producing a detectable signal include the use of radioactive labels, fluorescent labels, enzyme labels, and so forth. For example, if the antigen to be detected contains a second binding site, an antibody which binds to that site can be conjugated to a detectable group and added to the liquid phase reaction solution before the separation step. The presence of the detectable group on the solid support indicates the presence of the antigen in the test sample. Examples of suitable immunoassays are the radioimmunoassay, immunofluorescence methods, enzyme-linked immunoassays, and the like.

Those skilled in the art will be familiar with numerous specific immunoassay formats and variations thereof which may be useful for carrying out the method disclosed herein. See generally E. Maggio, Enzyme- Immunoass ay , (1980) (CRC Press, Inc., Boca Raton, FL) ; see also U.S. Patent No. 4,727,022 to Skold et al. titled "Methods for Modulating Ligand-Receptor Interactions and their Application," U.S. Patent No. 4,659,678 to Forrest et al. titled "Immunoassay of Antigens," U.S. Patent No. 4,376,110 to David et al., titled "Immunometric Assays Using Monoclonal Antibodies," U.S. Patent No. 4,275,149 to Litman et al. , titled "Macromolecular Environment Control in Specific Receptor Assays," U.S. Patent No. 4,233,402 to Maggio et al., titled "Reagents and Method Employing Channeling," and U.S. Patent No. 4,230,767 to Boguslaski et al., titled "Heterogenous Specific Binding Assay Employing a Coenzyme as Label." Applicants specifically intend that the disclosures of all U.S. Patent references cited herein be incorporated herein by reference. Monoclonal antibodies as described herein may be used in a "two-site" or "sandwich" assay, with a single cell line serving as a source for both the labeled monoclonal antibody and the bound monoclonal antibody. Such assays are described in U.S. Patent No. 4,376,110, the disclosure of which is also incorporated herein by reference.

Antibodies as described herein may be conjugated to a solid support suitable for a diagnostic assay (e.g., beads, plates, slides or wells formed from materials such as latex or polystyrene) in accordance with known techniques, such as precipitation. Antibodies as described herein may likewise be conjugated to detectable groups such as radiolabels (e.g., ³⁵S, ¹²⁵I, ¹³¹I) , enzyme labels (e.g., horseradish peroxidase, alkaline phosphatase) , and fluorescent labels (e.g., fluorescein) in accordance with known techniques.

Diagnostic kits for carrying out the methods disclosed above may be produced in a number of ways. In one embodiment, the diagnostic kit comprises (a) an antibody of the invention conjugated to a solid support and (b) a second antibody of the invention conjugated to a detectable group. The reagents may also include ancillary agents such as buffering agents and protein stabilizing agents, e.g., polysaccharides and the like. The diagnostic kit may further include, where necessary, other members of the signal-producing system of which system the detectable group is a member (e.g. , enzyme substrates) , agents for reducing background interference in a test, control reagents, apparatus for conducting a test, and the like. A second embodiment of a test kit comprises (a) an antibody as described herein, and (b) a specific binding partner for the antibody conjugated to a detectable group. Ancillary agents as described above may likewise be included. The test kit may be packaged in any suitable manner, typically with all elements in a single container along with a sheet of printed instructions for carrying out the test.

D. Therapeutic Applications

Monoclonal antibodies used for therapy (i.e., in a method of combatting cancer) may be monoclonal antibodies per se or monoclonal antibodies coupled to a therapeutic agent. Such antibodies are referred to herein as therapeutic monoclonal antibodies. Any therapeutic agent conventionally coupled to a monoclonal antibody may be employed, including (but not limited to) radioisotopes, cytotoxic agents, and chemotherapeutic agents. See generally Monoclonal .Antibodies and Cancer Therapy (R. Reisfeld and S. Sell Eds. 1985) (Alan R. Liss Inc. NY). Therapeutic agents may be coupled to the antibody by direct means or indirect means (e.g., via a chelator) .

Examples of radioisotopes which may be coupled to a therapeutic monoclonal antibody include, but are not limited to, ¹³¹I, ⁹⁰Y, ²¹¹At, ²¹²Bi, ⁶⁷Cu, ¹⁸⁶Re, ¹⁸⁸Re, and ²¹²Pb. Examples of chemotherapeutic agents which may be coupled to a therapeutic monoclonal antibody include, but are not limited to, methotrexate. Examples of cytotoxic agents which may be coupled to a therapeutic monoclonal antibody include, but are not limited to, ricin (or more particularly the ricin A chain) .

It will be appreciated that monoclonal antibodies per se which are used as therapeutic monoclonal antibodies incorporate those portions of the constant region of an antibody necessary to evoke a therapeutically useful immunological response in the subject being treated.

Therapeutic monoclonal antibodies may be provided in lyophylized form in a sterile aseptic container or may be provided in a pharmaceutical formulation in combination with a pharmaceutically acceptable carrier, such as sterile pyrogen-free water or sterile pyrogen-free physiological saline solution.

Subjects who may be treated with therapeutic monoclonal antibodies of the invention are, in general, subjects harboring tumors which express the ganglioside 3' ,6'-isoLDl. Examples of suitable subjects include those subjects which may be diagnosed as having cancer as set forth above, with patients afflicted with gliomas amd embryonal carcinomas again being particularly preferred. The method of administration of the monoclonal antibodies of the present invention to a subject (e.g. human or animal) will vary with individual circumstances, e.g. the particular disease (e.g. cancer) being treated, as will the dosage and frequency of administration. Generally, the antibody will be mixed, prior to administration, with a non-toxic, pharmaceutically acceptable carrier substance (e.g. normal saline or phosphate-buffered saline) , and will be administered using any medically appropriate procedure, e.g., intravenous or intra-arterial administration, injection into the cerebrospinal fluid). In certain cases, intradermal, intracavity, intrathecal or direct administration to the tumor or to an artery supplying the tumor is advantageous. In addition, either intrathecal administration or injection into the carotid artery are advantageous for therapy of tumors located in the brain. Dosage of the antibody will depend, among other things, on the tumor being treated, the route of administration, the nature of the therapeutic agent employed, and the sensitivity of the tumor to the particular therapeutic agent. For example, the dosage will typically be about 1 to 10 micrograms per Kilogram subject body weight. In another example, where the therapeutic agent is ¹³¹I, the dosage to the patient will typically be between about 10 to 500 mCi. Doses for other radionuclides are typically selected so that the tumoricidal dose will be equivalent to the foregoing range for ¹³¹I. The antibody can be administered to the subject in a series of more than one administration, and regular periodic administration will sometimes be required.

The present invention is explained in greater detail in the following non-limiting Examples.

EXAMPLE 1

Glvcolipjd Preparation

Gangliosides and neutral glycolipids used as standards and references were isolated and characterized by fast atom bombardment-mass spectrometry. NeuAc-GM2 was isolated from Tay-Sachs brain in accordance with known techniques (B. Rosengren et al., J. Neurochem. 49, 834-840 (1987)) ; GM3 and GD3 were purified from metastatic melanoma tissue removed at surgery; and GD2 was prepared by bovine /3-galactosidase treatment of GDlb purified from normal adult human brain. Purified enzyme was kindly provided by Dr. George Jourdian, University of Michigan, Ann Arbor. 3'-isoLMl and GalNAc-3 '-isoLMl were purified from human meconium in accordance with known techniques (P. Fredman et al., J. Biol . Chem. 264, 12122-12125 (1989)), 3'-LM1 and 3',8'-LDl from cauda equina (18), and 3'-isoLMl and 3',6'- isoLDl from human glioma cell line D-54 MG-induced nude mouse and nude rat xenografts (J.-E. Mansson et al., supra) or from brains of patients dying of polyunsaturated fatty acid lipidosis (L. Svennerholm et al., J. Neurochem. 49, 1772-1783 (1987)). All other glycolipids were purified from normal adult human brain. The isolation and char¬ acterization of gangliotetraose series gangliosides has been described (P. Fredman et al., J. Biol . Chem. 264, 12122-12125 (1989); J.-E. Mansson et al. , FEBS Lett . 196, 259-262 (1986)).

Monosialo- and oligosialoganglioside fractions were prepared from cultured cell pellets, normal tissue, or tumor xenografts of known weight and/or cell count as previously described (C. Wikstrand et al., J. Neuropathol . Exp. Neurol . 50, 756-769 (1991); P. Fredman et al., Biochim. Biophys . Acta 618, 42-52 (1980)). Densitometric scanning of resorcinol-visualized ganglioside bands was performed at 620 nm with a CAMAG TLC Scanner II (CAMAG, Muttenz, Switzerland) . Quantitative measurement of total ganglioside sialic acid was performed by the resorcinol assay in accordance with known techniques (L. Svennerholm, Biochim. Biophys . Acta 24, 604-611 (1957)).

EXAMPLE 2 Cell Lines The established permanent human glioma and medulloblastoma-derived cell lines used in this study are known and have been described in the literature. See C. Wikstrand et al., supra ; D. Bigner et al., J. Neuropathol . Exp. Neurol . 40, 201-229 (1981); S. Bigner et al. , Cancer Genet . Cytogenet . 10, 335-349 (1983); S. Bigner et al.. Cancer Genet . Cytogenet . 24, 1633-1637 (1987); J. Mark et al., Hereditas 78, 304-308 (1974); J. Mark et al., Hereditas 87, 243-260 (1977); X. He et al., J. Neuropathol . Exp. Neurol . 48, 48-68 (1989). Neuroblastoma cell lines SK-N-MC, SK-N-SH, LAN-1, and LAN-5 were kindly provided by Dr. Robert Seeger, UCLA. The American Type Culture Collection, Rockville, MD, was the source for cell lines TERA-1, TERA-2, SK-MEL-28, IMR-32, and P3X63/Ag8.653 (653). The cell line N417D (small-cell lung carcinoma) was obtained from the National Cancer Institute; and the embryonal carcinoma cell line PA-1 was the gift of Dr. James Trosko, Michigan State University, East Lansing, MI. The propagation, storage, and testing of these cell lines to ensure the absence of HeLa cell contamination, inter- or intra-cell line contamination, or Mycoplas a infection was carried out in accordance with standard techniques. See C. Wikstrand et al., J. Neuroimmunol . 15, 37-56 (1987).

EXAMPLE 3 Preparation of PA-1 Teratoma Xenograft Homo enate for Immunization of Mice for Hybridoma Production Cultured PA-1 embryonal carcinoma cells were injected into nu/nu (Balb/c) mice for the production of subcutaneous xenografts in accordance with known techniques. See, e. g. , H. Friedman et al., J. Neuropathol . Exp. Neurol . 42: 485-503 (1983). When tumors attained an estimated volume in excess of 1000 mm₃, the animals were sacrificed and immersed in 95% ethanol followed by an immersion in Betadine (Purdue Frederick Co., Norwalk, CT) . Under a laminar flow hood, tumors were separated from overlying skin with sterile scissors and the tumor placed in a Petri dish. The tumor was dissected to obtain viable tissue and to remove membranes, dead cells and fat; tumor tissue was placed in a clean Petri dish, weighted, and minced with two scalpels. Minced tumor material was placed in a trypsinizing flask with 0.25% trypsin (Sigma, St. Louis, MO) in Dulbecco's phosphate-buffered saline (Gibco, Grand Island, NY, D-PBS; Ca₊₊ and Mg₊₊ free, pH 7.1) at a ratio of 5 mis per gram of tissue and allowed to stir at 37° for 15-20 minutes. The supernatant phase containing dissociated cells was filtered through sterile cheesecloth- covered funnels, and cells pelleted at approximately 200xg for 5 minutes. The supernatant was removed and the cell pellet resuspended in 0.83% ammonium chloride (pH 6.0) in water and allowed to stand for 3 minutes, at which point an equal volume of fetal calf serum (Gibco) was added and the cells pelleted again at 200 x g. Supernatant was removed and the cells washed once with 10 mis of D-PBS. Following an additional centrifugation of 200 x g, pellets were resuspended in 10 mis serum-free Zinc Option (ZO) tissue culture medium (Gibco) . Ten mis of Lymphocyte Separation Medium (ficoll; Organon Teknika, Durham, NC) were carefully layered under the cell suspension by trocar and gradient formed by centrifugation at 400 x g for 15 minutes. The medium-ficoll interface, containing viable tumor cells was removed by pipette and added to 10 mis of ZO and centrifuged for 10 minutes at 375 x g. Supernatant was removed, and the cell pellet resuspended in 10 mis ZO and cells counted. Cells were pelleted at 200xg and adjusted to a final concentration of 1 x 10₇ cells per 0.5 ml in ZO and injected intraperitoneally into Balb/c recipient mice.

EXAMPLE 4 Production of Hvbridomas Producinσ

DMAb21 and DMAb22

Female BALB/c mice, 15 weeks of age (Charles

River Breeding Laboratories, Stoneridge, NY) , were used for immunization with PA-1 terato a cells grown in xenograft form in athymic mice; PA-1 cultured and xenograft cells express both 3'-isoLMl and 3',6'-isoLDl. (M. Fukuda et al., supra ; C. Wikstrand et al., supra) . Donors received multiple doses of trypsinized (0.25%) PA-1 murine xenograft cells prepared as described in Example 3 above intraperitoneally in an extended series of injections according to the schedule set forth in Table 1 below. Table 1. Immunization Schedule for Production of DMAb 21 and DMAb 22.

Three days after the final interperitioneal injection, fusion with 653 cells was performed by in accordance with standard procedures. See C. Wikstrand et al., J. Neuroimmunol . 3, 43-62 (1982); C. Wikstrand et al., Cancer Res. 46, 5933-5940 (1986). Initial reactivity screen was performed against mono- and oligosialoganglioside fractions of D-54 MG xenograft cells, of which 3'-isoLMl and 3',6'- isoLDl are the predominant mono- and disialogangliosides, respectively, to optimize selection for the target gan¬ glioside 3' ,6'-isoLDl, with minimal selection of hybrids producing antibodies to other PA-1-associated gangliosides. Two hybrids (DMAb-21 and DMAb-22) were selected for further study on the basis of titer, stability, and apparent speci¬ fic ganglioside binding, determined by comparative immunostain of 3' ,6'-isoLDl-containing extracts as defined by DMAb-14 (C. Wikstrand et al., J. Neuropathol . Exp. Neurol . 50, 756-769 (1991)). Hybrids were cloned in methylcellulose semisolid medium (C. Wikstrand et al., J. Neuroimmunol . 3, 43-62 (1982)) three times and cultured for the production of antibody-containing supernatant or cells for ascites establishment.

Isotype determination was performed on both supernatant and purified ascitic samples by enzyme immunoassay in accordance with known techniques (C. Wikstrand et al., J. Neuropathol . Exp. Neurol . 50, 756-769 (1991)); both DMAb-21 and DMAb-22 are IgM-κ antibodies. MAb-containing ascites fluid was induced by the transfer of 2 x 10⁷ hybridoma cells to pristane (Aldrich Chemical Co., Milwaukee, WI)-primed athymic mice (nu/nu, BALB/c background) maintained in our colony (H. Friedman et al., J. Neuropathol . Exp. Neurol . 42, 485-503 (1983)).

EXAMPLE 5 Antibody Purification

Ascitic fluids were purified by passage over a high pressure liquid chromatography gel filtration column

(Bio-Sil SEC 400, 21.5 x 600 mm) in 0.05 M Na₂S0₄, 0.02

NaH₂P0₄, 0.3 M NaCl buffer (pH 6.8) (C. Wikstrand et al., J.

Neuropathol . Exp. Neurol . 50, 756-769 (1991)). Peak fractions were collected, concentrated 5X by Amicon filtration, and dialyzed versus 0.15 M [Na₂H, NaH₂]P0₄, 0.3

M NaCl buffer (pH 7.2). Antibodies were filtered through a 0.22-μ Millipore filter, protein concentration was determined by Lowry assay, IgM concentration was determined by capture enzyme-linked immunosorbent assay (C. Wikstrand et al., supra) , and purified antibody was stored for use at

4^°C. Antibody purity was checked by 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

EXAMPLE 6 Assays for Antibody Activity Both solid-phase (SP-RIA) and cell-surface radioimmunoassay were performed in accordance with known techniques (C. Wikstrand et al., J. Neuropathol . Exp. Neurol . 50, 756-769 (1991) ; C. Wikstrand and D. Bigner, Cancer Res . 42, 267-275 (1982); F. Vrionis et al. , Cancer Res . 49, 6645-6651 (1989)); MOPC-104E (IgM) and previously defined anti-3'-isoLMl MAb SL-50 and anti-3 '-isoLMl and 3*,6'-isoLDl MAb DMAb- 14, respectively, were used as negative and positive primary control reagents. Antibody binding is expressed as a binding ratio, calculated by dividing experimental cpm by negative control cpm; a binding ratio >3 is considered positive as these values exceed the mean background value by >3 standard deviations (C. Wikstrand and D. Bigner, supra) . For SP-RIA, known picomolar amounts of ganglioside in methanol were plated in polyvinylchloride microtiter plates (Dynatech Laboratories, Inc., Chantilly, VA) and allowed to dry by evaporation. Before immunoassay, blocking of nonspecific binding was performed by a 30-min exposure at room temperature to incubation buffer (50 μM Tris-HCl, 15 mM NaCl, 3% low-fat milk, pH 7.4). Incubation times at 37^°C were performed for 2 h; results were calculated as for cell surface radioimmunoassay.

EXAMPLE7 HPTLC Immunostaininq Gangliosides—either purified to homogeneity or as mono- or oligosialoganglioside fractions extracted from cultured cell pellets, normal human brain, or xenograft tissues—were separated by HPTLC, and reactivity with individual MAbs was determined in accordance with known techniques. See C. Wikstrand et al., J. Neuropathol . Exp. Neurol . 50, 756-769 (1991); P. Fredman et al., Biochim. Biophys . Acta 1045, 239-244 (1990) . Reference gangliosides were visualized with orcinol reagent (0.1% orcinol in distilled H₂0, 3% H₂SO .

EXAMPLE 8

Immunohistochemical Staining of Frozen Tumor Tissue

Immunohistological procedures are well known, have been thoroughly described in the literature, and were carried out in accordance with standard techniques herein. See C. Wikstrand et al., J. Neuropathol . Exp. Neurol . 50, 756-769 (1991); F. Vrionis et al., Cancer Res . 49, 6645- 6651 (1989). Snap-frozen specimens, maintained at -135°C, were cut 5- to 10-μm thick, applied to glass slides, acetone-fixed at -20°C, and air-dried. Rehydrated sections were blocked with 10% normal goat serum, sequentially exposed to appropriate primary reagents, and developed with the Zymed biotinylated antibody-streptavidin- diaminobenzidine system (F. Vrionis et al., supra) . Slides were counterstained with hematoxylin, mounted, and scored for reactivity by a minimum of two observers. The tissues were evaluated microscopically for immunoreactivity in both normal and neoplastic cells. Positivity was evaluated with respect to nuclear, cytoplasmic, and/or membranous localization of bound reagents. Each neoplasm was graded with regard to percent of neoplastic cells positive on a four-tiered scheme: less than 25% cells positive (+/-) , 25-50% cells positive (+) , 50-75% cells positive (++) , and 75-100% (+++) cells positive. Any antigen localization in benign cells within the tissue section was noted.

EXAMPLE 9

Reactivity and Specificity of DMAb-21 and DMAb-22

The two hybrids, DMAb-21 and DMAb-22, were initially selected for further analysis on the basis of positive activity for D-54 MG rat xenograft oligosialoganglioside fractions by SP-RIA and HPTLC immunostain in comparison with DMAb-14 (Figure 1) . As revealed by the titration in SP-RIA of purified MAbs against the total oligosialoganglioside fraction of D-54 MG rat xenograft, no difference in the activity of the three MAbs is apparent. However, separation of the components of the oligosialoganglioside extract by HPTLC in C:M:0.25% KC1 (50:40:10, by volume) reveals apparent restriction of recognition by DMAb-21 and DMAb-22 to the oligosialoganglioside extract as compared with the recognition of both 3'-isoLMl and 3',6'-isoLDl by DMAb-14 (data not shown) . Notable also is the lack of recognition of GM2, GM1, GDla, GDlb, or GTlb. The specificity of the reactivity of these MAbs is further demonstrated by examination of binding of DMAb-22 to purified 3 ' ,6' ,-isoLDl and this antigen in oligosialoganglioside fractions from various tissues (data not shown). Purified 3' ,6'-isoLDl isolated from D-54 MG rat xenografts was readily detected in as little as 1 pmol concentrations; the reactivity of DMAb-22 for 3' ,6'-isoLDl in murine D-54 MG xenografts as compared with the rat xenograft fractions reflected both differences in ceramide composition and preponderance of N- glycolyl versus N-acetyl sialylation in mice as opposed to rats (C. Wikstrand et al., J. Neuropathol . Exp. Neurol . 50, 756-769 (1991)). No other ganglioside was detected in these fractions. Oligosialoganglioside extracts from human cauda equina, human 20-week gestation fetal brain, and brain tissue from a case of polyunsaturated fatty acid lipidosis also contained 3 ' ,6'-isoLDl, but in much lower concentrations than in D-54 MG xenografts (2X, 5X, and 10X concentrations, respectively, of extract required for detection). DMAb-22 does not react with purified 3',8'-LDl from human red blood cells, the oligosialoganglioside fraction of normal adult brain cerebral cortex, or purified fuc-3 '-isoLMl (the CA-50 antigen).

The results of these analyses with purified, fast atom bombardment-mass spectrometry verified ganglio¬ side and glycolipid standards are summarized in Figure 1. The reactivity spectra of DMAb-21 and DMAb-22 are similar to that of DMAb-14 in that gangliosides of the ganglio series (GM2, GD2, GDla, GDlb) , the lactosyl series (GD3) , and the neolactotetraose series (3*-LMl, 3',8'-LDl) are not bound by these MAbs (data not shown) . Unlike DMAb-14, both DMAb-21 and DMAb-22 require sialylation of the subterminal N-acetylglucosamine. Fucosylation of this sugar, as in Fuc-3 '-isoLMl (Figure 1), does not permit binding of DMAb- 21 or DMAb-22. Therefore, the minimum binding epitope of these MAbs is suggested to be NeuAc(or NeuGc)a2-3Gal/31- 3(NeuAc or NeuGc)α2-6GlcNAc, as illustrated in Figure 2. Note that NeuAc is the form synthesized in human cells, while NeuGc is the form synthesized in other species. EXAMPLE 10

Distribution of 3'.6'-isoLDl in Cell Lines and Xenografts of Human Tumors

Oligosialoganglioside fractions were prepared from packed cell pellets or xenograft tissue as described above. Human cell lines examined included 14 glioma, 5 medulloblastoma, 3 teratoma, and 5 lines of various origins: 1 pancreatic carcinoma (HPAF) , 1 small-cell carcinoma of the lung (N417) , 1 melanoma (SK-MEL-28) , 1 rhabdomyosarcoma (TE-671) , and 1 neuroblastoma (LAN-1) (Table 2) . Of these cell lines, 10 gliomas, 5 medulloblastomas, 2 teratomas, and 3 of the miscellaneous lines had corresponding murine xenografts from which oligosialoganglioside fractions were obtained. HPTLC immu- nostain analysis of these ganglioside extracts was performed with DMAb-21 and DMAb-22; complete concordance of reactivity was observed. The results of these assays are summarized in Table 2, which shows reactivity to both DMAb- 21 and DMAb-22. Note from Table 2 that there was no detectable discrepancy between the reactivity of the two MAbs. Up to 2 nmol ganglioside sialic acid were loaded per lane, depending upon the optimal concentration for band development; all extracts testing negative were tested as 4 nmol/lane, representing as much as 4800 (D-54 MG cells) , or 3600 (D-259 MG cells) μg sample protein/lane. For samples demonstrating positivity, the range of sample protein loaded was 950-2600 μg protein/lane.

TABLE 2

HPTLC Immunostain Analysis of Oligosialoganglioside Extracts of Cultured Cell Lines and Xenografts

NA - Not available. Note also from Table 2 that four of 26 cell line extracts examined expressed 3',6'-isoLDl: all 3 teratoma cell lines and the pancreatic carcinoma cell line HPAF. No glioma or medulloblastoma cell line extract expressed 3' ,6'-isoLDl; the glioma cell line extracts of D-259 MG and D-263 MG, which express 3'-isoLMl (12), did not express the disialo derivative. Six of 19 xenograft ganglioside extracts examined expressed detectable 3 ' ,6'-isoLDl: 4/10 glioma xenografts and 2/2 teratoma xenografts. All positive xenografts also expressed 3'-isoLMl (data not shown) .

EXAMPLE 11 Immunohistological Evaluation of Human Neoplasms

Both DMAb-21 and DMAb-22 were screened against the panel of frozen, acetone-fixed tissues listed in Table 3; again, results with the two antibodies were completely concordant; 15/30 of the glial tumor blocks were tested repetitively on consecutive sections with no significant discrepancies noted in the antigen localization patterns. Immunohistochemical staining with both DMAb-21 and DMAb-22 revealed 14/23 gliomas to exhibit localization in the neoplastic cell population (+/- to +++) . Reactivity with the MAbs roughly correlated with glioma cell size; cells with abundant cytoplasm tended to exhibit strong cytoplasmic immunoreactivity and cells with scant cytoplasm tended to be nonreactive (Figure 3A) . A giant cell glioblastoma and a glioblastoma multiforme with large populations of gemistocytes exhibited strong reactivity (+++) (Figure 3, B and D) . Fibrillar glioblastomas multiforme exhibited moderate, diffuse cytoplasmic reactivity (+++) of neoplastic cells. Glioblastomas multiforme composed of predominantly small cells, also known as "anaplastic cells" (F. Giangaspero and P. Burger, Cancer 52, 2320-2333 (1983)) were negative. In heterogeneous tumors, or tumors with mixed small and non- small cell populations, the non-small cell component was prominently stained as compared to the negative small cell component (Figure 3C) . Cytoplasmic reactivity was the predominant reactivity pattern in the glioblastoma multiforme; membranous localization was never observed without cytoplasmic localization, and was never stronger than the cytoplasmic pattern. Nuclear reactivity was evident in three glioblastomas multiforme.

Results of analysis of nonneural neoplasms are also presented in Table 3. Both DMAb-21 and DMAb-22 bound the membranes and cytoplasm of many of the tumor types examined. Membrane reactivity was never identified without concomitant cytoplasmic reactivity. The majority (62%) of epithelial cancers studied were reactive with anti-3',6¹- isoLDl MAbs; notable exceptions being carcinomas of the ovary (0/3 positive) and lung of all types (2/7 positive) . A common feature in carcinomas was the presence of antigen localization also in the benign desmoplastic fibrous connective tissue about the infiltrating neoplasm, a pattern independent of neoplastic cell localization. As demonstrated in Figure 4, teratomas exhibited

MAb localization in the immature mesenchymal elements, a small round cell element, the immature basaloid epithelial cells of a hair shaft component, and faint positivity in a mature neural element (Figure 4, A and B) . Intense staining of neoplastic cells is evident in 3/3 leiomyosarcomas studied (Figure 4, C and D) , while the breast carcinomas revealed punctate intranuclear, possibly nucleolar, antigen localization, a pattern not seen in any other neoplasm (Figure 4E) . No antigen localization occurred in lymphomas; the absence of lymphoid cell staining is apparent in a germinoma tissue section in which the large neoplastic cellular component is prominently stained, and the infiltrative lymphocyte component is totally negative (Figure 4F) . TABLE 3

Summary of DMAb-21 and DMAb-22 Reactivity with Acetone- Fixed, Frozen Sections of Human Tumor Tissues

* Number of cases in which the neoplastic cell component was determined positive. ^b Three cases consisting of one moderately differentiated adenocarcinoma, one large-cell carcinoma, and a squamous cell carcinoma that was weakly positive. EXAMPLE 12 Comparative Analysis of Binding Characteristics

Additional data on the binding characteristics of two monoclonal antibodies of the present invention, DMAb-21 and DMAb-22, is summarized in Figure 5. The binding characteristics of two other antibodies, SL-50 and

FH9, are included for comparison.

The foregoing examples are illustrative of the present invention, and are not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims

THAT WHICH IS CLAIMED IS:

1. A monoclonal antibody which binds to the ganglioside IV³NeuAc,III⁶NeuAc-LcOse₄Cer (3 ' ,6'-isoLDl) , and which does not bind to the ganglioside IV³NeuAc₂- III⁶NeuAcLcOse_A-Cer (3• ,6' ,8'-isoLTl) .

2. A monoclonal antibody according to claim 1 which has the binding characteristics set forth in Figure 2.

3. A monoclonal antibody according to claim 1 which binds to a 3',6'-isoLDl epitope selected from the group consisting of NeuAcα2-3Gal,51-3NeuAcα2-6GlcNAc and NeuGcα2-3Gal/31-3NeuGcα2-6GlcNAc.

4. A monoclonal antibody according to claim 1 coupled to a detectable group.

5. A monoclonal antibody according to claim 1 coupled to a detectable group selected from the group consisting of radiolabels, enzyme labels, fluorescent labels, and ferromagnetic labels.

6. A monoclonal antibody according to claim 1 coupled to a therapeutic agent.

7. A monoclonal antibody according to claim 1 coupled to a therapeutic agent selected from the group consisting of radioisotopes, cytotoxic agents, and chemotherapeutic agents.

8. A monoclonal antibody according to claim 1 coupled to a radioisotope selected from the group consisting of ¹³¹I, ⁹⁰Y, ²¹¹At, ²¹²Bi, ⁶⁷Cu, ¹⁸⁶Re, ¹⁸⁸Re, and ²¹²Pb.

9. A pharmaceutical formulation comprising a monoclonal antibody according to claim 1 in a pharmaceutically acceptable carrier.

10. An antibody according to claim 1 for use in therapy.

11. The use of an antibody according to claim 1 for the preparation of a medicament for treating cancer in a human or animal subject.

12. The use according to claim 11, wherein said cancer is a glioma.

13. The use according to claim 11, wherein said cancer is embryonal carcinoma.

14. The use according to claim 11, wherein said antibody is coupled to a therapeutic agent.

15. A method for detecting the presence of cancer in a human or animal subject, comprising: contacting a sample collected from said subject with an antibody according to claim 1 under conditions permitting the antibody to form a reaction product; and then detecting the presence or absence of the reaction product.

16. A method according to claim 15, which method is selected from the group consisting of radioimmunoassay, im unofluorescence assay, and enzyme immunoassay.

17. A method according to claim 15, wherein said sample is a biological fluid.

18. A method according to claim 15, wherein said sample is a biological fluid selected from the group consisting of serum and blood plasma.

19. A test kit for detecting the presence or absence of cancer in a human or animal subject comprising an antibody according to claim 1.

20. A test kit according to claim 19, wherein said antibody is coupled to a detectable group.

21. A method of making antibodies which bind to the ganglioside 3' ,6'-isoLDl, comprising: administering an animal xenograft cells, wherein said xenograft cells express the ganglioside 3',6'-isoLDl, for a time and in an amount effective to produce antibodies which bind to the ganglioside 3• ,6'-isoLDl.

22. A method according to claim 21, further comprising the step of collecting spleen cells from said animal following said immunizing step and fusing said spleen cells with a continuous cell line to produce a hybridoma cell line, which hybridoma cell line produces monoclonal antibodies which bind to the ganglioside 3' ,6- isoLDl.

23. A monoclonal antibody-producing cell line which produces an antibody which binds to the ganglioside IV³NeuAc,III⁶NeuAc-LcOse_ACer (3 ' ,6'-isoLDl) , and which does not bind to the ganglioside IV³NeuAc₂-III⁶NeuAcLcOse-Cer (3¹ ,6' ,8^«-isoLTl) .

24. A monoclonal antibody-producing cell line according to claim 23, which cell is selected from the group consisting of hybridoma cells and Escherichia coli cells.

25. A method of making a monoclonal antibody which binds to the ganglioside IV³NeuAc,III⁶NeuAc-LcOseCer (3• ,6'-isoLDl) , and which does not bind to the ganglioside IV³NeuAc₂-III⁶NeuAcLcOse₄-Cer (3' ,6' ,8'-isoLTl) , comprising: culturing a cell according to claim 20 in a culture medium under conditions suitable for the production of monoclonal antibodies; and collecting said monoclonal antibody from said culture medium.