COMPOUNDS AND METHODS FOR PREVENTION AND TREATMENT OF HER-2/<i>neu</i> ASSOCIATED MALIGNANCIES

Abstract: Compounds and compositions for eliciting or enhancing immune reactivity to HER-2/<i>neu</i> protein are disclosed. The compounds include antigen-presenting cells, such as dendritic cells, which may be used for the prevention or treatment of malignancies in which the HER-2/<i>neu</i> oncogene is associated.

Description: COMPOUNDS AND METHODS FOR PREVENTION AND TREATMENT OF HER-2lneu ASSOCIATED MALIGNANCIES TECHNICAL FIELD The present invention is generally directed to antigen-presenting cells expressing polypeptides for eliciting or enhancing an immune response to HER-2/røew protein, including for use in the treatment of malignancies in which the ΗER-2/neu oncogene is associated. BACKGROUND OF THE INVENTION Despite enormous investments of financial and human resources, cancer remains one of the major causes of death. For example, cancer is the leading cause of death in women between the ages of 35 and 74. Breast cancer is the most common malignancy in women and the incidence for developing breast cancer is on the rise. One in nine women will be diagnosed with the disease. Standard approaches to cure breast cancer have centered around a combination of surgery, radiation and chemotherapy. These approaches have resulted in some dramatic successes in certain malignancies. However, these approaches have not been successful for all malignancies and breast cancer is most often incurable when attempting to treat beyond a certain stage. Alternative approaches to prevention and therapy are necessary. A common characteristic of malignancies is uncontrolled cell growth. Cancer cells appear to have undergone a process of transformation from the normal phenotype to a malignant phenotype capable of autonomous growth. Amplification and overexpression of somatic cell genes is considered to be a common primary event that results in the transformation of normal cells to malignant cells. The malignant phenotypic characteristics encoded by the oncogenic genes are passed on during cell division to the progeny of the transformed cells. Ongoing research involving oncogenes has identified at least forty oncogenes operative in malignant cells and responsible for, or associated with, transformation. Oncogenes have been classified into different groups based on the putative function or location of their gene products (such as the protein expressed by the oncogene). Oncogenes are believed to be essential for certain aspects of normal cellular physiology. In this regard, the ΗER.-2/neu oncogene is a member of the tyrosine protein kinase family of oncogenes and shares a high degree of homology with the epidermal growth factor receptor. HER-2/πew presumably plays a role in cell growth and/or differentiation. HER-2/røew appears to induce malignancies through quantitative mechanisms that result from increased or deregulated expression of an essentially normal gene product. HER-2/πew (pi 85) is the protein product of the ΗER-2/neu oncogene. The HER-2/neu gene is amplified and the HER-2/neu protein is overexpressed in a variety of cancers including breast, ovarian, colon, lung and prostate cancer. HER- 2/neu is related to malignant transformation. It is found in 50%-60% of ductal in situ carcinoma and 20%-40% of all breast cancers, as well as a substantial fraction of adenocarcinomas arising in the ovaries, prostate, colon and lung. ΗER-2/neu is intimately associated not only with the malignant phenotype, but also with the aggressiveness of the malignancy, being found in one-fourth of all invasive breast cancers. HER-2/neu overexpression is correlated with a poor prognosis in both breast and ovarian cancer. ΗER-2lneu is a transmembrane protein with a relative molecular mass of 185 kd that is approximately 1255 amino acids (aa) in length. It has an extracellular binding domain (ECD) of approximately 645 aa, with 40% homology to epidermal growth factor receptor (EGFR), a highly hydrophobic transmembrane anchor domain (TMD), and a carboxyterminal cytoplasmic domain (CD) of approximately 580 aa with 80% homology to EGFR. Due to the difficulties in the current approaches to therapy of cancers in which the HER-2lneu oncogene is associated, there is a need in the art for improved compounds and compositions. The present invention fulfills this need, and further provides other related advantages. SUMMARY OF THE INVENTION Briefly stated, the present invention provides cells such as antigen- presenting cells for uses that include the immunization of a warm-blooded animal against a malignancy in which the BER-2lneu oncogene is associated. A cell according to this invention may be present in a composition that includes a pharmaceutically acceptable carrier or diluent. Such a cell may be administered on a one-time basis (e.g., when a malignancy is suspected) or on a periodic basis (e.g., for an individual with an elevated risk of acquiring or reacquiring a malignancy). A compound or composition of the present invention may be useful in the treatment of an existing tumor or to prevent tumor occurrence or reoccurrence. In one aspect, the present invention provides isolated antigen-presenting cells that express a polypeptide comprising at least an immunogenic portion of an amino acid sequence encoded by a DNA sequence selected from: (a) nucleotides 2026 through 3765 of SEQ ID NO:l; and (b) DNA sequences that hybridize to a nucleotide sequence complementary to nucleotides 2026 through 3765 of SEQ ID NO:l under moderately stringent conditions, wherein the DNA sequence encodes a polypeptide that produces an immune response to BER-2lneu protein. Certain antigen-presenting cell express at least an immunogenic portion of a polypeptide comprising the amino acid sequence of SEQ ID NO:2 from lysine, amino acid 676, through valine, amino acid 1255, or a variant thereof that produces at least an equivalent immune response. Within further embodiments, pharmaceutical compositions are provided comprising such antigen-presenting cells, in combination with a pharmaceutically acceptable carrier or excipient. Also provided are vaccines, comprising such antigen- presenting cells in combination with a non-specific immune response enhancer. Antigen-presenting cells may be, for example, dendritic cells or macrophages. Methods are further provided, within other aspects, for inhibiting the development of a cancer {e.g., breast cancer) in a patient, comprising administering to a patient an effective amount of an antigen-presenting cell as described above, and thereby inhibiting the development of a cancer in the patient. Such methods may be prophylactic {i.e., used to prevent or delay the onset of a disease) or therapeutic {i.e., used to improve the condition of a patient already afflicted with the disease). These and other aspects of the present invention will become evident upon reference to the following detailed description and attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph depicting the resultsof 51 Cr-release assays demonstrating ICD reactivity in a CD8+ T cell line primed with AdV. Normal donor PBMC were primed with DC-infected with recombinant AdV expressing ICD. The assay was a standard 4 hour 51 Cr-release assay; targets were autologous B-LCL, either uninfected or infected with recombinant cawinia virus expessing ICD oe EGFP, as indicated. Each data point was the average of three measurements. Figure 2 is a graph depicting the results of flow cytometric analysis of surface Her-2/neu on MCF-7 tumor cells. Cells were stained with a mAb to surface Her-2/neu, followed by a secondary rabbit anti-mouse Ig antibody conjugated to PE. Labeled cells were analyzed by flow cytometry. Values for mean fluorescent intensity were as follows: MCF-7 = 32; MCF-7 + RTV-H2N = 165; MCF-7 + Ad-H2N = 683; MCF-7 + RTV-H2N + Ad-H2N = 651. DETAILED DESCRIPTION OF THE INVENTION Prior to setting forth the invention, it may be helpful to an understanding thereof to set forth definitions of certain terms to be used hereinafter. HER-2/neu polypeptide - as used herein, refers to a portion of the HER- 2lneu protein (the protein also known as pi 85 or c-erbB2) having the amino acid sequence of SEQ ID NO:2 from lysine, amino acid 676, through valine, amino acid 1255; and may be naturally derived, synthetically produced, genetically engineered, or a functionally equivalent variant thereof, e.g., where one or more amino acids are replaced by other amino acid(s) or non-amino acid(s) which do not substantially affect elicitation or enhancement of an immune response to HER-2/πew protein (e.g., variant stimulates a response by helper T cells or cytotoxic T cells). Proliferation of T cells - as used herein, includes the multiplication of T cells as well as the stimulation of T cells leading to multiplication, i.e., the initiation of events leading to mitosis and mitosis itself. Methods for detecting proliferation of T cells are discussed below. As noted above, the present invention is directed toward compounds and compositions to elicit or enhance immunity to the protein product expressed by the ER-2/neu oncogene, including for malignancies in a warm-blooded animal wherein an amplified HER-2lneu gene is associated with the malignancies. Association of an amplified HER-2lneu gene with a malignancy does not require that the protein expression product of the gene be present on the tumor. For example, overexpression of the protein expression product may be involved with initiation of a tumor, but the protein expression may subsequently be lost. A use of the present invention is to elicit or enhance an effective autochthonous immune response to convert a ΗER-2/neu positive tumor to HER-2lneu negative. . More specifically, the disclosure of the present invention, in one aspect, shows that a polypeptide based on a particular portion {HER-2lneu polypeptide) of the protein expression product of the HER-2//?ew gene can be recognized by thymus- dependent lymphocytes (hereinafter "T cells") and, therefore, the autochthonous immune T cell response can be utilized prophylactically or to treat malignancies in which such a protein is or has been overexpressed. The disclosure of the present invention also shows, in another aspect, that nucleic acid molecules directing the expression of such a peptide may be used alone or in a viral vector for immunization. In further aspects, antigen-presenting cells expressing immunogenic portions of Her- 2/neu are shown to have therapeutic benefit. In general, CD4+ T cell populations are considered to function as helpers/inducers through the release of lymphokines when stimulated by a specific antigen; however, a subset of CD4 + cells can act as cytotoxic T lymphocytes (CTL). Similarly, CD8 + T cells are considered to function by directly lysing antigenic targets; however, under a variety of circumstances they can secrete lymphokines to provide helper or DTH function. Despite the potential of overlapping function, the phenotypic CD4 and CD 8 markers are linked to the recognition of peptides bound to class II or class I MHC antigens. The recognition of antigen in the context of class II or class I MHC mandates that CD4 + and CD8 + T cells respond to different antigens or the same antigen presented under different circumstances. The binding of immunogenic peptides to class II MHC antigens most commonly occurs for antigens ingested by antigen presenting cells. Therefore, CD4 + T cells generally recognize antigens that have been external to the tumor cells. By contrast, under normal circumstances, binding of peptides to class I MHC occurs only for proteins present in the cytosol and synthesized by the target itself, proteins in the external environment are excluded. An exception to this is the binding of exogenous peptides with a precise class I binding motif which are present outside the cell in high concentration. Thus, CD4 + and CD8 + T cells have broadly different functions and tend to recognize different antigens as a reflection of where the antigens normally reside. As disclosed within the present invention, a polypeptide portion of the protein product expressed by the HER-2/Vzew oncogene is recognized by T cells. Circulating HER-2lneu polypeptide is degraded to peptide fragments. Peptide fragments from the polypeptide bind to major histocompatibility complex (MHC) antigens. By display of a peptide bound to MHC antigen on the cell surface and recognition by host T cells of the combination of peptide plus self MHC antigen, ΗER-2/neu polypeptide (including that expressed on a malignant cell) will be immunogenic to T cells. The exquisite specificity of the T cell receptor enables individual T cells to discriminate between peptides which differ by a single amino acid residue. During the immune response to a peptide fragment from the polypeptide, T cells expressing a T cell receptor with high affinity binding of the peptide-MHC complex will bind to the peptide-MHC complex and thereby become activated and induced to proliferate. In the first encounter with a peptide, small numbers of immune T cells will secrete lymphokines, proliferate and differentiate into effector and memory T cells. The primary immune response will occur in vivo but has been difficult to detect in vitro. Subsequent encounter with the same antigen by the memory T cell will lead to a faster and more intense immune response. The secondary response will occur either in vivo or in vitro. The in vitro response is easily gauged by measuring the degree of proliferation, the degree of cytokine production, or the generation of cytolytic activity of the T cell population re-exposed in the antigen. Substantial proliferation of the T cell population in response to a particular antigen is considered to be indicative of prior exposure or priming to the antigen. Certain compounds of this invention generally comprise Y_ER-2lneu polypeptides or DNA molecules that direct the expression of such peptides, wherein the DNA molecules may be present in a viral vector. As noted above, the polypeptides of the present invention include variants of the polypeptide of SEQ ID NO:2 from amino acid 676 through amino acid 1255, that retain the ability to stimulate an immune response. Such variants include various structural forms of the native polypeptide. Due to the presence of ionizable amino and carboxyl groups, for example, a HΕR-2lneu polypeptide may be in the form of an acidic or basic salt, or may be in neutral form. Individual amino acid residues may also be modified by oxidation or reduction. Variants within the scope of this invention also include polypeptides in which the primary amino acid structure native ΗER-2/neu polypeptide is modified by forming covalent or aggregative conjugates with other peptides or polypeptides, or chemical moieties such as glycosyl groups, lipids, phosphate, acetyl groups and the like. Covalent derivatives may be prepared, for example, by linking particular functional groups to amino acid side chains or at the N- or C-terminus. The present invention also includes HER-2/neu polypeptides with or without glycosylation. Polypeptides expressed in yeast or mammalian expression systems may be similar to or slightly different in molecular weight and glycosylation pattern than the native molecules, depending upon the expression system. For instance, expression of DNA encoding polypeptides in bacteria such as E. coli typically provides non-glycosylated molecules. N-glycosylation sites of eukaryotic proteins are characterized by the amino acid triplet Asn-Aj-Z, where A] is any amino acid except Pro, and Z is Ser or Thr. Variants of HER-2lneu polypeptides having inactivated N- glycosylation sites can be produced by techniques known to those of ordinary skill in the art, such as oligonucleotide synthesis and ligation or site-specific mutagenesis techniques, and are within the scope of this invention. Alternatively, N-linked glycosylation sites can be added to a ΗER-2lneu polypeptide. The polypeptides of this invention also include variants of the SEQ ID NO:2 polypeptide (i.e., variants of a polypeptide having the amino acid sequence of SEQ ID NO:2 from amino acid 676 through amino acid 1255) that have an amino acid sequence different from this sequence because of one or more deletions, insertions, substitutions or other modifications. In one embodiment, such variants are substantially homologous to the native HER-2/new polypeptide and retain the ability to stimulate an immune response. "Substantial homology," as used herein, refers to amino acid sequences that may be encoded by DNA sequences that are capable of hybridizing under moderately stringent conditions to a nucleotide sequence complimentary to a naturally occurring DNA sequence encoding the specified polypeptide portion of SEQ ID NO:2 herein (i.e., nucleotides 2026 through 3765 of SEQ ID NO:l). Suitable moderately stringent conditions include prewashing in a solution of 5 X SSC, 0.5% SDS, 1.0 mM EDTA (pH 8.0); hybridizing at 50°C-65°C, 5 X SSC, overnight; followed by washing twice at 65°C for 20 minutes with each of 2X, 0.5X and 0.2X SSC (containing 0.1% SDS). Such hybridizing DNA sequences are also within the scope of this invention. The effect of any such modifications on the ability of a ΗER-2/neu polypeptide to produce an immune response may be readily determined (e.g., by analyzing the ability of the mutated HER-2/neu polypeptide to induce a T cell response using, for example, the methods described herein). Generally, amino acid substitutions may be made in a variety of ways to provide other embodiments of variants within the present invention. First, for example, amino acid substitutions may be made conservatively; i.e, a substitute amino acid replaces an amino acid that has similar properties, such that one skilled in the art of peptide chemistry would expect the secondary structure and hydropathic nature of the polypeptide to be substantially unchanged. In general, the following groups of amino acids represent conservative changes: (1) ala, pro, gly, glu, asp, gin, asn, ser, thr; (2) cys, ser, tyr, thr; (3) val, ile, leu, met, ala, phe; (4) lys, arg, his; and (5)phe, tyr, trp, his. An example of a non-conservative change is to replace an amino acid of one group with an amino acid from another group. Another way to make amino acid substitutions to produce variants of the present invention is to identify and replace amino acids in T cell motifs with potential to bind to class II MHC molecules (for CD4+ T cell response) or class I MHC molecules (for CD8+ T cell response). Peptide segments (of a HER-2/neu polypeptide) with a motif with theoretical potential to bind to class II MHC molecules may be identified by computer analysis. For example, a protein sequence analysis package, T Sites, that incorporates several computer algorithms designed to distinguish potential sites for T cell recognition can be used (Feller and de la Cruz, Nature 349:720-721, 1991). Two searching algorithms are used: (1) the AMPHI algorithm described by Margalit (Feller and de la Cruz, Nαtwre 349:720-721, 1991; Margalit et al., J Immunol. 138:2213-2229, 1987) identifies epitope motifs according to alpha-helical periodicity and amphipathicity; (2) the Rothbard and Taylor algorithm identifies epitope motifs according to charge and polarity pattern (Rothbard and Taylor, EMBO 7:93-100, 1988). Segments with both motifs are most appropriate for binding to class II MHC molecules. CD8 + T cells recognize peptide bound to class I MHC molecules. Falk et al. have determined that peptides binding to particular MHC molecules share discernible sequence motifs (Falk et al., Nature 351:290-296, 1991). A peptide motif for binding in the groove of HLA-A2.1 has been defined by Edman degradation of peptides stripped from HLA-A2.1 molecules of a cultured cell line (Table 1, from Falk et al., supra). The method identified the typical or average HLA-A2.1 binding peptide as being 9 amino acids in length with dominant anchor residues occurring at positions 2 (L) and 9 (V). Commonly occurring strong binding residues have been identified at positions 2 (M), 4 (E,K), 6 (V), and 8 (K). The identified motif represents the average of many binding peptides. Table 1 The HLA-A2.1 Restricted Motif The derived peptide motif as currently defined is not particularly stringent. Some HLA-A2.1 binding peptides do not contain both dominant anchor residues and the amino acids flanking the dominant anchor residues play major roles in allowing or disallowing binding. Not every peptide with the current described binding motif will bind, and some peptides without the motif will bind. However, the current motif is valid enough to allow identification of some peptides capable of binding. Of note, the current HLA-A2.1 motif places 6 amino acids between the dominant anchor amino acids at residues 2 and 9. Following identification of peptide motifs within a HER-2/neu polypeptide, amino acid substitutions may be made conservatively or non- conservatively. The latter type of substitutions are intended to produce an improved polypeptide that is more potent and/or more broadly cross-reactive (MHC polymorphism). An example of a more potent polypeptide is one that binds with higher affinity to the same MHC molecule as natural polypeptide, without affecting recognition by T cells specific for natural polypeptide. An example of a polypeptide with broader cross-reactivity is one that induces more broadly cross-reactive immune responses (i.e., binds to a greater range of MHC molecules) than natural polypeptide. Similarly, one or more amino acids residing between peptide motifs and having a spacer function (e.g., do not interact with a MHC molecule or T cell receptor) may be substituted conservatively or non-conservatively. It will be evident to those of ordinary skill in the art that polypeptides containing one or more amino acid substitutions may be tested for beneficial or adverse immunological interactions by a variety of assays, including those described herein for the ability to stimulate T cell recognition. Variants within the scope of this invention may also, or alternatively, contain other modifications, including the deletion or addition of amino acids, that have minimal influence on the desired immunological properties of the polypeptide. It will be appreciated by those of ordinary skill in the art that truncated forms or non-native extended forms of a ELER-2/neu polypeptide may be used, provided the desired immunological properties are at least roughly equivalent to that of full length, native HER-2lneu polypeptide. Cysteine residues may be deleted or replaced with other amino acids to prevent formation of incorrect intramolecular disulfide bridges upon renaturation. Other approaches to mutagenesis involve modification of adjacent dibasic amino acid residues to enhance expression in yeast systems in which KEX2 protease activity is present. A ΗER-2lneu polypeptide may generally be obtained using a genomic or cDNA clone encoding the protein. A genomic sequence that encodes full length HER-2/neu is shown in SEQ ID NO:l, and the deduced amino acid sequence is presented in SEQ ID NO:2. Such clones may be isolated by screening an appropriate expression library for clones that express ¥LER-2/neu protein. The library preparation and screen may generally be performed using methods known to those of ordinary skill in the art, such as methods described , in Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratories, Cold Spring Harbor, N.Y., 1989, which is incorporated herein by reference. Briefly, a bacteriophage expression library may be plated and transferred to filters. The filters may then be incubated with a detection reagent. In the context of this invention, a "detection reagent" is any compound capable of binding to HER-2lneu protein, which may then be detected by any of a variety of means known to those of ordinary skill in the art. Typical detection reagents contain a "binding agent," such as Protein A, Protein G, IgG or a lectin, coupled to a reporter group. Preferred reporter groups include enzymes, substrates, cofactors, inhibitors, dyes, radionuclides, luminescent groups, fluorescent groups and biotin. More preferably, the reporter group is horseradish peroxidase, which may be detected by incubation with a substrate such as tetramethylbenzidine or 2,2'-azino-di-3- ethylbenz-thiazoline sulfonic acid. Plaques containing genomic or cDNA sequences that express ΗER-2lneu protein are isolated and purified by techniques known to those of ordinary skill in the art. Appropriate methods may be found, for example, in Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratories, Cold Spring Harbor, N. Y., 1989. Variants of the polypeptide that retain the ability to stimulate an immune response may generally be identified by modifying the sequence in one or more of the aspects described above and assaying the resulting polypeptide for the ability to stimulate an immune response, e.g., a T cell response. For example, such assays may generally be performed by contacting T cells with the modified polypeptide and assaying the response. Naturally occurring variants of the polypeptide may also be isolated by, for example, screening an appropriate cDNA or genomic library with a DNA sequence encoding the polypeptide or a variant thereof. The above-described sequence modifications may be introduced using standard recombinant techniques or by automated synthesis of the modified polypeptide. For example, mutations can be introduced at particular loci by synthesizing oligonucleotides containing a mutant sequence, flanked by restriction sites enabling ligation to fragments of the native sequence. Following ligation, the resulting reconstructed sequence encodes an analogue having the desired amino acid insertion, substitution, or deletion. Alternatively, oligonucleotide-directed site-specific mutagenesis procedures can be employed to provide a gene in which particular codons are altered according to the substitution, deletion, or insertion required. Exemplary methods of making the alterations set forth above are disclosed by Walder et al., Gene 42:133, 1986; Bauer et al., Gene 37:73, 1985; Craik, BioTechniques, January 1985, 12-19; Smith et al., Genetic Engineering: Principles and Methods, Plenum Press, 1981; and U.S. Patent Nos. 4,518,584 and 4,737,462. Mutations in nucleotide sequences constructed for expression of such ΗER-2lneu polypeptides must, of course, preserve the reading frame of the coding sequences and preferably will not create complementary regions that could hybridize to produce secondary mRNA structures, such as loops or hairpins, which would adversely affect translation of the mRNA. Although a mutation site may be predetermined, it is not necessary that the nature of the mutation er se be predetermined. For example, in order to select for optimum characteristics of mutants at a given site, random mutagenesis may be conducted at the target codon and the expressed HER-2/neu polypeptide mutants screened for the desired activity. Not all mutations in a nucleotide sequence which encodes a HER-2/neu polypeptide will be expressed in the final product. For example, nucleotide substitutions may be made to enhance expression, primarily to avoid secondary structure loops in the transcribed mRNA (see, e.g., European Patent Application 75,444A), or to provide codons that are more readily translated by the selected host, such as the well-known E. coli preference codons for E. coli expression. The polypeptides of the present invention, both naturally occurring and modified, are preferably produced by recombinant DNA methods. Such methods include inserting a DNA sequence encoding a ER-2/neu polypeptide into a recombinant expression vector and expressing the DNA sequence in a recombinant microbial, mammalian or insect cell expression system under conditions promoting expression. DNA sequences encoding the polypeptides provided by this invention can be assembled from cDNA fragments and short oligonucleotide linkers, or from a series of oligonucleotides, to provide a synthetic gene which is capable of being inserted in a recombinant expression vector and expressed in a recombinant transcriptional unit. Recombinant expression vectors contain a DNA sequence encoding a HER-2/røew polypeptide operably linked to suitable transcriptional or translational regulatory elements derived from mammalian, microbial, viral or insect genes. Such regulatory elements include a transcriptional promoter, an optional operator sequence to control transcription, a sequence encoding suitable mRNA ribosomal binding sites, and sequences which control the termination of transcription and translation. An origin of replication and a selectable marker to facilitate recognition of transformants may additionally be incorporated. DNA regions are operably linked when they are functionally related to each other. For example, DNA for a signal peptide (secretory leader) is operably linked to DNA for a polypeptide if it is expressed as a precursor which participates in the secretion of the polypeptide; a promoter is operably linked to a coding sequence if it controls the transcription of the sequence; or a ribosome binding site is operably linked to a coding sequence if it is positioned so as to permit translation. Generally, operably linked means contiguous and, in the case of secretory leaders, in reading frame. DNA sequences encoding HER-2lneu polypeptides which are to be expressed in a microorganism will preferably contain no introns that could prematurely terminate transcription of DNA into mRNA. Expression vectors for bacterial use may comprise a selectable marker and bacterial origin of replication derived from commercially available plasmids comprising genetic elements of the well known cloning vector pBR322 (ATCC 37017). Such commercial vectors include, for example, pKK223-3 (Pharmacia Fine Chemicals, Uppsala, Sweden) and pGEMl (Promega Biotec, Madison, WI, USA). These pBR322 "backbone" sections are combined with an appropriate promoter and the structural sequence to be expressed. E. coli is typically transformed using derivatives of pBR322, a plasmid derived from an E. coli species (Bolivar et al., Gene 2:95, 1977). pBR322 contains genes for ampicillin and tetracycline resistance and thus provides simple means for identifying transformed cells. Promoters commonly used in recombinant microbial expression vectors include the β-lactamase (penicillinase) and lactose promoter system (Chang et al., Nature 275:615, 1978; and Goeddel et al., Nature 281:544, 1979), the tryptophan (tip) promoter system (Goeddel et al., Nucl. Acids Res. S.4057, 1980; and European Patent Application 36,776) and the tac promoter (Maniatis, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory, p.412, 1982). A particularly useful bacterial expression system employs the phage λ P promoter and cI857ts thermolabile repressor. Plasmid vectors available from the American Type Culture Collection which incorporate derivatives of the λ P promoter include plasmid pHUB2, resident in E. coli strain JMB9 (ATCC 37092) and pPLc28, resident inE. coli RR1 (ATCC 53082). Suitable promoter sequences in yeast vectors include the promoters for metallothionein, 3-phosphoglycerate kinase (Hitzeman et al., J. Biol. Chem. 255:2073, 1980) or other glycolytic enzymes (Hess et al., J. Adv. Enzyme Reg. 7:149, 1968; and Holland et al., Biochem. 77:4900, 1978), such as enolase, glyceraldehyde-3 -phosphate dehydrogenase, hexokinase, pyruvate decarboxylase, phosphofructokinase, glucose- 6-phosρhate isomerase, 3-phosphoglycerate mutase, pyruvate kinase, triosephosphate isomerase, phosphoglucose isomerase, and glucokinase. Suitable vectors and promoters for use in yeast expression are further described in R. Hitzeman et al., European Patent Application 73,657. Preferred yeast vectors can be assembled using DNA sequences from pBR322 for selection and replication in E. coli (Amp r gene and origin of replication) and yeast DNA sequences including a glucose-repressible ADH2 promoter and α-factor secretion leader. The ADH2 promoter has been described by Russell et al. (J Biol. Chem. 258:2674, 1982) and Beier et al. {Nature 300:724, 1982). The yeast α-factor leader, which directs secretion of heterologous proteins, can be inserted between the promoter and the structural gene to be expressed (see, e.g., Kurjan et al., Cell 30:933, 1982; and Bitter et al., Proc. Natl. Acad. Sci. USA 81:5330, 1984). The leader sequence may be modified to contain, near its 3' end, one or more useful restriction sites to facilitate fusion of the leader sequence to foreign genes. The transcriptional and translational control sequences in expression vectors to be used in transforming vertebrate cells may be provided by viral sources. For example, commonly used promoters and enhancers are derived from polyoma, adenovirus 2, simian virus 40 (SV40), and human cytomegalovirus. DNA sequences derived from the SV40 viral genome, for example, SV40 origin, early and late promoter, enhancer, splice, and polyadenylation sites may be used to provide the other genetic elements required for expression of a heterologous DNA sequence. The early and late promoters are particularly useful because both are obtained easily from the virus as a fragment which also contains the SV40 viral origin of replication (Fiers et al., Nature 273:113, 1978). Smaller or larger SV40 fragments may also be used, provided the approximately 250 bp sequence extending from the Hind III site toward the Bgl II site located in the viral origin of replication is included. Further, viral genomic promoter, control and/or signal sequences may be utilized, provided such control sequences are compatible with the host cell chosen. Exemplary vectors can be constructed as disclosed by Okayama and Berg, Mo/. Cell. Biol. 3:280, 1983. A useful system for stable high level expression of mammalian receptor cDNAs in C127 murine mammary epithelial cells can be constructed substantially as described by Cosman et al. {Mol. Immunol. 23:935, 1986). A preferred eukaryotic vector for expression of HER-2/røez polypeptide DNA is pDC406 (McMahan et al., EMBO J. 10:2821, 1991), and includes regulatory sequences derived from SV40, human immunodeficiency virus (HIV), and Epstein-Barr virus (EBV). Other preferred vectors include pDC409 and pDC410, which are derived from pDC406. pDC410 was derived from pDC406 by substituting the EBV origin of replication with sequences encoding the SV40 large T antigen. pDC409 differs from pDC406 in that a Bgl II restriction site outside of the multiple cloning site has been deleted, making the Bgl II site within the multiple cloning site unique. A useful cell line that allows for episomal replication of expression vectors, such as pDC406 and pDC409, which contain the EBV origin of replication, is CV-1/EBNA (ATCC CRL 10478). The CV-L/EBNA cell line was derived by transfection of the CV-1 cell line with a gene encoding Epstein-Barr virus nuclear antigen-I (EBNA-1) and constitutively express EBNA-1 driven from human CMV immediate-early enhancer/promoter. Transformed host cells are cells which have been transformed or transfected with expression vectors constructed using recombinant DNA techniques and which contain sequences encoding a ΗER-2lneu polypeptide of the present invention. Transformed host cells may express the desired HER-2lneu polypeptide, but host cells transformed for purposes of cloning or amplifying HER-2/neu DNA do not need to express the ELER-2/neu polypeptide. Expressed polypeptides will preferably be secreted into the culture supernatant, depending on the DNA selected, but may also be deposited in the cell membrane. Suitable host cells for expression of recombinant proteins include prokaryotes, yeast or higher eukaryotic cells under the control of appropriate promoters. Prokaryotes include gram negative or gram positive organisms, for example E. coli or Bacilli. Higher eukaryotic cells include established cell lines of insect or mammalian origin as described below. Cell-free translation systems could also be employed to produce ΗER-2/neu polypeptides using RNAs derived from DNA constructs. Appropriate cloning and expression vectors for use with bacterial, fungal, yeast, and mammalian cellular hosts are described, for example, by Pouwels et al., Cloning Vectors: A Laboratory Manual, Elsevier, New York, 1985. Prokaryotic expression hosts may be used for expression of HER-2/neu polypeptides that do not require extensive proteolytic and disulfide processing. Prokaryotic expression vectors generally comprise one or more phenotypic selectable markers, for example a gene encoding proteins conferring antibiotic resistance or supplying an autotrophic requirement, and an origin of replication recognized by the host to ensure amplification within the host. Suitable prokaryotic hosts for transformation include E. coli, Bacillus subtilis, Salmonella typhimurium, and various species within the genera Pseudomonas, Streptomyces, and Staphylococcus, although other hosts may also be employed. Recombinant ΗER-2lneu polypeptides may also be expressed in yeast hosts, preferably from the Saccharomyces species, such as S. cerevisiae. Yeast of other genera, such as Pichia or Kluyveromyces may also be employed. Yeast vectors will generally contain an origin of replication from the 2μ yeast plasmid or an autonomously replicating sequence (ARS), a promoter, DNA encoding the ΗER-2lneu polypeptide, sequences for polyadenylation and transcription termination and a selection gene. Preferably, yeast vectors will include an origin of replication and selectable marker permitting transformation of both yeast and E. coli, e.g., the ampicillin resistance gene of E. coli and the S. cerevisiae trpl gene, which provides a selection marker for a mutant strain of yeast lacking the ability to grow in tryptophan, and a promoter derived from a highly expressed yeast gene to induce transcription of a structural sequence downstream. The presence of the trpl lesion in the yeast host cell genome then provides an effective environment for detecting transformation by growth in the absence of tryptophan. Suitable yeast transformation protocols are known to those of skill in the art. An exemplary technique described by Hind et al. {Proc. Natl. Acad. Sci. USA 75:1929, 1978), involves selecting for Trp + transformants in a selective medium consisting of 0.67% yeast nitrogen base, 0.5% casamino acids, 2% glucose, 10 mg/ml adenine and 20 mg/ml uracil. Host strains transformed by vectors comprising the ADH2 promoter may be grown for expression in a rich medium consisting of 1% yeast extract, 2% peptone, and 1% glucose supplemented with 80 mg/ml adenine and 80 mg/ml uracil. Derepression of the ADH2 promoter occurs upon exhaustion of medium glucose. Crude yeast supernatants are harvested by filtration and held at 4°C prior to further purification. Various mammalian or insect (e.g., Spodoptera or Trichoplusiά) cell culture systems can also be employed to express recombinant polypeptide. Baculovirus systems for production of heterologous polypeptides in insect cells are reviewed, for example, by Luckow and Summers, Bio/Technology 6:47, 1988. Examples of suitable mammalian host cell lines include the COS-7 lines of monkey kidney cells, described by Gluzman {Cell 23:175, 1981), and other cell lines capable of expressing an appropriate vector including, for example, CV-1/EBNA (ATCC CRL 10478), L cells, C127, 3T3, Chinese hamster ovary (CHO), COS, NS-1, HeLa and BHK cell lines. Mammalian expression vectors may comprise nontranscribed elements such as an origin of replication, a suitable promoter and enhancer linked to the gene to be expressed, and other 5' or 3' flanking nontranscribed sequences, and 5' or 3' nontranslated sequences, such as necessary ribosome binding sites, a polyadenylation site, splice donor and acceptor sites, and transcriptional termination sequences. Purified ER-2lneu polypeptides may be prepared by culturing suitable host/vector systems to express the recombinant translation products of the DNAs of the present invention, which are then purified from culture media or cell extracts. For example, supernatants from systems which secrete recombinant polypeptide into culture media may be first concentrated using a commercially available protein concentration filter, such as an Amicon or Millipore Pellicon ultrafiltration unit. Following the concentration step, the concentrate may be applied to a suitable purification matrix. For example, a suitable affinity matrix may comprise a counter structure protein (i.e., a protein to which a HER-2/«ew polypeptide binds in a specific interaction based on structure) or lectin or antibody molecule bound to a suitable support. Alternatively, an anion exchange resin can be employed, for example, a matrix or substrate having pendant diethylaminoethyl (DEAE) groups. The matrices can be acrylamide, agarose, dextran, cellulose or other types commonly employed in protein purification. Alternatively, a cation exchange step can be employed. Suitable cation exchangers include various insoluble matrices comprising sulfopropyl or carboxymethyl groups. Sulfopropyl groups are preferred. Gel filtration chromatography also provides a means of purifying a EiER-2lneu. Affinity chromatography is a preferred method of purifying HER-2lneu polypeptides. For example, monoclonal antibodies against the HER-2//?ew polypeptide may also be useful in affinity chromatography purification, by utilizing methods that are well-known in the art. Finally, one or more reverse-phase high performance liquid chromatography (RP-HPLC) steps employing hydrophobic RP-HPLC media (e.g, silica gel having pendant methyl or other aliphatic groups) may be employed to further purify a HER-2/neu polypeptide composition. Some or all of the foregoing purification steps, in various combinations, can also be employed to provide a homogeneous recombinant polypeptide. Recombinant ΗER-2lneu polypeptide produced in bacterial culture is preferably isolated by initial extraction from cell pellets, followed by one or more concentration, salting-out, aqueous ion exchange or size exclusion chromatography steps. High performance liquid chromatography (HPLC) may be employed for final purification steps. Microbial cells employed in expression of recombinant HER-2/neu polypeptide can be disrupted by any convenient method, including freeze-thaw cycling, sonication, mechanical disruption, or use of cell lysing agents. Fermentation of yeast which express HER-2lneu polypeptide as a secreted protein greatly simplifies purification. Secreted recombinant protein resulting from a large-scale fermentation can be purified by methods analogous to those disclosed by Urdal et al. (J. Chromatog. 296:171, 1984). This reference describes two sequential, reverse-phase HPLC steps for purification of recombinant human GM-CSF on a preparative HPLC column. Preparations of HER-2/neu polypeptides synthesized in recombinant culture may contain non-HER-2/new cell components, including proteins, in amounts and of a character which depend upon the purification steps taken to recover the HER-2/neu polypeptide from the culture. These components ordinarily will be of yeast, prokaryotic or non-human eukaryotic origin. Such preparations are typically free of other proteins which may be normally associated with the HER-2lneu protein as it is found in nature in its species of origin. Automated synthesis provides an alternate method for preparing polypeptides of this invention. For example, any of the commercially available solid- phase techniques may be employed, such as the Merrifield solid phase synthesis method, in which amino acids are sequentially added to a growing amino acid chain. (See Merrifield, J. Am. Chem. Soc. 55:2149-2146, 1963.) Equipment for automated synthesis of polypeptides is commercially available from suppliers such as Applied Biosystems, Inc. of Foster City, CA, and may generally be operated according to the manufacturer's instructions. Within certain aspects of the present invention, use of a HER-2/neu polypeptide (or an antigen-presenting cell that expresses such a peptide) to generate an immune response to the ϊϊER-2lneu protein (including that expressed on a malignancy in which a HER-2/neu oncogene is associated) may be detected. Representative examples of such malignancies include breast, ovarian, colon, lung and prostate cancers. An immune response to the HER-2lneu protein, once generated by a UER-2lneu polypeptide, can be long-lived and can be detected long after immunization, regardless of whether the protein is present or absent in the body at the time of testing. An immune response to the HER-2/neu protein generated by reaction to a HER-2lneu polypeptide can be detected by examining for the presence or absence, or enhancement, of specific activation of CD4 + or CD8 + T cells. More specifically, T cells isolated from an immunized individual by routine techniques (such as by Ficoll Hypaque density gradient centrifugation of peripheral blood lymphocytes) are incubated with HER-2/neu protein. For example, T cells may be incubated in vitro for 2-9 days (typically 4 days) at 37 DC with BER-2lneu protein (typically, 5 Dg/ml of whole protein or graded numbers of cells synthesizing ER-2/neu protein). It may be desirable to incubate another aliquot of a T cell sample in the absence of ΗER-2lneu protein to serve as a control. Specific activation of CD4 + or CD8 + T cells may be detected in a variety of ways. Methods for detecting specific T cell activation include detecting the proliferation of T cells, the production of cytokines (e.g., lymphokines), or the generation of cytolytic activity (i.e., generation of cytotoxic T cells specific for HER- 2lneu protein). For CD4 + T cells, a preferred method for detecting specific T cell activation is the detection of the proliferation of T cells. For CD8 + T cells, a preferred method for detecting specific T cell activation is the detection of the generation of cytolytic activity. Detection of the proliferation of T cells may be accomplished by a variety of known techniques. For example, T cell proliferation can be detected by measuring the rate of DNA synthesis. T cells which have been stimulated to proliferate exhibit an increased rate of DNA synthesis. A typical way to measure the rate of DNA synthesis is, for example, by pulse-labeling cultures of T cells with tritiated thymidine, a nucleoside precursor which is incorporated into newly synthesized DNA. The amount of tritiated thymidine incorporated can be determined using a liquid scintillation spectrophotometer. Other ways to detect T cell proliferation include measuring increases in interleukin-2 (IL-2) production, Ca 2+ flux, or dye uptake, such as 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium. Alternatively, synthesis of lymphokines (such as interferon-gamma) can be measured or the relative number of T cells that can respond to intact pl s UER'2/ u protein may be quantified. By use or expression of a HER-2/neu polypeptide, or antigen-presenting cell as described herein, T cells which recognize the HER-2/neu protein can be proliferated in vivo. For example, immunization with a HER-2/τ.ew peptide or antigen- presenting cell (i.e., as a vaccine) can induce continued expansion in the number of T cells necessary for therapeutic attack against a tumor in which the ΗER-2/neu oncogene is associated. Typically, about 0.01 μg/kg to about 100 mg/kg body weight will be administered by the intradermal, subcutaneous or intravenous route. A preferred dosage is about 1 μg/kg to about 1 mg/kg, with about 5 μg/kg to about 200 μg/kg particularly preferred. It will be evident to those skilled in the art that the number and frequency of administration will be dependent upon the response of the patient. It may be desirable to administer the HER-2/neu polypeptide repetitively. It will be evident to those skilled in this art that more than one ΗER-2lneu polypeptide may be administered, either simultaneously or sequentially. Preferred peptides for immunization are those that include the amino acid sequence of SEQ ID NO:2 beginning at about the lysine residue at amino acid position 676 and extending to about the valine residue at amino acid position 1255. It will be appreciated by those in the art that the present invention contemplates the use of an intact ΗER-2/neu polypeptide as well as division of such a polypeptide into a plurality of peptides. Neither intact pi g5 HER - 2 " e " protein nor a peptide having the amino acid sequence of its entire extracellular domain (i.e., a peptide having an amino acid sequence of SEQ ID NO:2 from amino acid position 1 up to amino acid position 650, plus or minus about one to five positions, and with or without the first 21 amino acid positions) are used alone for immunization. A HER-2/neu polypeptide (or antigen-presenting cell) is preferably formulated for use in the above methods as a pharmaceutical composition or vaccine. Pharmaceutical compositions generally comprise one or more polypeptides or cells in combination with a pharmaceutically acceptable carrier, excipient or diluent. Such carriers will be nontoxic to recipients at the dosages and concentrations employed. The use of a HER-2/neu polypeptide or cell in conjunction with chemotherapeutic agents is also contemplated. Vaccines may comprise one or more such polypeptides or cells and a non-specific immune response enhancer. A non-specific immune response enhancer may be any substance that enhances an immune response to an exogenous antigen. Examples of non-specific immune response enhancers include adjuvants, biodegradable microspheres {e.g., poly lactic galactide) and liposomes (into which the compound is incorporated; see e.g., Fullerton, U.S. Patent No. 4,235,877). Vaccine preparation is generally described in, for example, M.F. Powell and M.J. Newman, eds., "Vaccine Design (the subunit and adjuvant approach)," Plenum Press (NY, 1995). Vaccines may be designed to generate antibody immunity and/or cellular immunity such as that arising from CTL or CD4+ T cells. Pharmaceutical compositions and vaccines within the scope of the present invention may also contain other compounds, which may be biologically active or inactive. For example, one or more immunogenic portions of other tumor antigens may be present, either incorporated into a fusion polypeptide or as a separate compound, within the composition or vaccine. Polypeptides may, but need not, be conjugated to other macromolecules as described, for example, within US Patent Nos. 4,372,945 and 4,474,757. Pharmaceutical compositions and vaccines may generally be used for prophylactic and therapeutic purposes. A pharmaceutical composition or vaccine may contain a polynucleotide encoding one or more of the polypeptides as described above, such that the polypeptide is generated in situ. Such a polynucleotide may comprise DNA, RNA, a modified nucleic acid or a DNA/RNA hybrid. As noted above, a polynucleotide may be present within any of a variety of delivery systems known to those of ordinary skill in the art, including nucleic acid expression systems, bacteria and viral expression systems. Numerous gene delivery techniques are well known in the art, such as those described by Rolland, Crit. Rev. Therap. Drug Carrier Systems 75:143-198, 1998, and references cited therein. Appropriate nucleic acid expression systems contain the necessary DNA sequences for expression in the patient (such as a suitable promoter and terminating signal). Bacterial delivery systems involve the administration of a bacterium (such as Bacillus-Calmette-Guerri ) that expresses an immunogenic portion of the polypeptide on its cell surface or secretes such an epitope. In a preferred embodiment, the DNA may be introduced using a viral expression system {e.g., vaccinia or other pox virus, retrovirus, or adenovirus), which may involve the use of a non-pathogenic (defective), replication competent virus. Suitable systems are disclosed, for example, in Fisher- Hoch et al., Proc. Natl. Acad. Sci. USA 55:317-321, 1989; Flexner et al, Ann. NY. Acad. Sci. 569:86-103, 1989; Flexner et al., Vaccine 5:17-21, 1990; U.S. Patent Nos. 4,603,112, 4,769,330, and 5,017,487; WO 89/01973; U.S. Patent No. 4,777,127; GB 2,200,651; EP 0,345,242; WO 91/02805; Berkner, Biotechniques 6:616-621, 1988; Rosenfeld et al., Science 252:431-434, 1991; Kolls et al., Proc. Natl. Acad. Sci. USA 97:215-219, 1994; Kass-Eisler et al., Proc. Natl. Acad. Sci. USA 90:11498-11502, 1993; Guzman et al., Circulation 55:2838-2848, 1993; and Guzman et al., Cir. Res. 73:1202-1207, 1993. Techniques for incorporating DNA into such expression systems are well known to those of ordinary skill in the art. The DNA may also be "naked," as described, for example, in Ulmer et al., Science 259:1745-1749, 1993 and reviewed by Cohen, Science 259:1691-1692, 1993. The uptake of naked DNA may be increased by coating the DNA onto biodegradable beads, which are efficiently transported into the cells. It will be apparent that a vaccine may comprise both a polynucleotide and a polypeptide component. Such vaccines may provide for an enhanced immune response. While any suitable carrier known to those of ordinary skill in the art may be employed in the pharmaceutical compositions of this invention, the type of carrier will vary depending on the mode of administration. Compositions of the present invention may be formulated for any appropriate manner of administration, including for example, topical, oral, nasal, intravenous, intracranial, intraperitoneal, subcutaneous or intramuscular administration. For parenteral administration, such as subcutaneous injection, the carrier preferably comprises water, saline, alcohol, a fat, a wax or a buffer. For oral administration, any of the above carriers or a solid carrier, such as mannitol, lactose, starch, magnesium stearate, sodium saccharine, talcum, cellulose, glucose, sucrose, and magnesium carbonate, may be employed. Biodegradable microspheres {e.g., polylactate polyglycolate) may also be employed as carriers for the pharmaceutical compositions of this invention. Suitable biodegradable microspheres are disclosed, for example, in U.S. Patent Nos. 4,897,268; 5,075,109; 5,928,647; 5,811,128; 5,820,883; 5,853,763; 5,814,344 and 5,942,252. Such compositions may also comprise buffers {e.g., neutral buffered saline or phosphate buffered saline), carbohydrates {e.g., glucose, mannose, sucrose or dextrans), mannitol, proteins, polypeptides or amino acids such as glycine, antioxidants, bacteriostats, chelating agents such as EDTA or glutathione, adjuvants (e.g., aluminum hydroxide), solutes that render the formulation isotonic, hypotonic or weakly hypertonic with the blood of a recipient, suspending agents, thickening agents and/or preservatives. Alternatively, compositions of the present invention may be formulated as a lyophilizate. Compounds may also be encapsulated within liposomes using well known technology. Any of a variety of non-specific immune response enhancers may be employed in the vaccines of this invention. For example, an adjuvant may be included. Most adjuvants contain a substance designed to protect the antigen from rapid catabolism, such as aluminum hydroxide or mineral oil, and a stimulator of immune responses, such as lipid A, Bortadella pertussis or Mycobacterium tuberculosis derived proteins. Suitable adjuvants are commercially available as, for example, Freund's Incomplete Adjuvant and Complete Adjuvant (Difco Laboratories, Detroit, MI); Merck Adjuvant 65 (Merck and Company, Inc., Rahway, NJ); AS-2 (SmithKline Beecham); aluminum salts such as aluminum hydroxide gel (alum) or aluminum phosphate; salts of calcium, iron or zinc; an insoluble suspension of acylated tyrosine; acylated sugars; cationically or anionically derivatized polysaccharides; polyphosphazenes; biodegradable microspheres; monophosphoryl lipid A and quil A. Cytokines, such as GM-CSF or interleukin-2, -7, or -12, may also be used as adjuvants. Within the vaccines provided herein, the adjuvant composition is preferably designed to induce an immune response predominantly of the Thl type. High levels of Thl -type cytokines {e.g., IFN-γ, TNF-α, IL-2 and IL-12) tend to favor the induction of cell mediated immune responses to an administered antigen. In contrast, high levels of Th2-type cytokines {e.g., IL-4, IL-5, IL-6 and IL-10) tend to favor the induction of humoral immune responses. Following application of a vaccine as provided herein, a patient will support an immune response that includes Thl- and Tintype responses. Within a preferred embodiment, in which a response is predominantly Thl -type, the level of Thl -type cytokines will increase to a greater extent than the level of Th2-type cytokines. The levels of these cytokines may be readily assessed using standard assays. For a review of the families of cytokines, see Mosmann and Coffman, Ann. Rev. Immunol. 7:145-173, 1989. Preferred adjuvants for use in eliciting a predominantly Thl -type response include, for example, a combination of monophosphoryl lipid A, preferably 3- de-O-acylated monophosphoryl lipid A (3D-MPL), together with an aluminum salt. MPL adjuvants are available from Ribi ImmunoChem Research Inc. (Hamilton, MT; see US Patent Nos. 4,436,727; 4,877,611; 4,866,034 and 4,912,094). CpG-containing oligonucleotides (in which the CpG dinucleotide is unmethylated) also induce a predominantly Thl response. Such oligonucleotides are well known and are described, for example, in WO 96/02555 and WP 99/33488. Immunostimulatory DNA sequences are also described, for example, by Sato et al., Science 273:352, 1996. Another preferred adjuvant is a saponin, preferably QS21 (Aquila, United States), which may be used alone or in combination with other adjuvants. For example, an enhanced system involves the combination of a monophosphoryl lipid A and saponin derivative, such as the combination of QS21 and 3D-MPL as described in WO 94/00153, or a less reactogenic composition where the QS21 is quenched with cholesterol, as described in WO 96/33739. Other preferred formulations comprise an oil-in-water emulsion and tocopherol. A particularly potent adjuvant formulation involving QS21, 3D-MPL and tocopherol in an oil-in-water emulsion is described in WO 95/17210. Other preferred adjuvants include Montanide ISA 720 (Seppic, France), SAF (Chiron, California, United States), ISCOMS (CSL), MF-59 (Chiron), the SBAS series of adjuvants {e.g., SBAS-2 or SBAS-4, available from SmithKline Beecham, Rixensart, Belgium), Detox (Ribi ImmunoChem Research Inc., Hamilton, MT), RC-529 (Ribi ImmunoChem Research Inc., Hamilton, MT) and Aminoalkyl glucosaminide 4- phosphates (AGPs). Any vaccine provided herein may be prepared using well known methods that result in a combination of antigen, immune response enhancer and a suitable carrier or excipient. The compositions described herein may be administered as part of a sustained release formulation {i.e., a formulation such as a capsule or sponge that effects a slow release of compound following administration). Such formulations may generally be prepared using well known technology {see, e.g., Coombes et al., Vaccine 7^:1429-1438, 1996) and administered by, for example, oral, rectal or subcutaneous implantation, or by implantation at the desired target site. Sustained- release formulations may contain a polypeptide, polynucleotide or antibody dispersed in a carrier matrix and/or contained within a reservoir surrounded by a rate controlling membrane. Carriers for use within such formulations are biocompatible, and may also be biodegradable; preferably the formulation provides a relatively constant level of active component release. Such carriers include microparticles of poly(lactide-co- glycolide), as well as polyacrylate, latex, starch, cellulose and dextran. Other delayed- release carriers include supramolecular biovectors, which comprise a non-liquid hydrophilic core {e.g., a cross-linked polysaccharide or oligosaccharide) and, optionally, an external layer comprising an amphiphilic compound, such as a phospholipid {see e.g., U.S. Patent No. 5, 151, 254 and PCT applications WO 94/20078, WO/94/23701 and WO 96/06638). The amount of active compound contained within a sustained release formulation depends upon the site of. implantation, the rate and expected duration of release and the nature of the condition to be treated or prevented. Any of a variety of delivery vehicles may be employed within pharmaceutical compositions and vaccines to facilitate production of an antigen-specific immune response that targets tumor cells. Delivery vehicles include antigen presenting cells (APCs), such as dendritic cells, macrophages, B cells, monocytes and other cells that may be engineered to be efficient APCs. Such cells may, but need not, be genetically modified to increase the capacity for presenting the antigen, to improve activation and/or maintenance of the T cell response, to have anti-tumor effects per se and/or to be immunologically compatible with the receiver {i.e., matched HLA haplotype). APCs may generally be isolated from any of a variety of biological fluids and organs, including tumor and peritumoral tissues, and may be autologous, allogeneic, syngeneic or xenogeneic cells. Certain preferred embodiments of the present invention use dendritic cells or progenitors thereof as antigen-presenting cells. Dendritic cells are highly potent APCs (Banchereau and Steinman, Nature 392:245-251, 1998) and have been shown to be effective as a physiological adjuvant for eliciting prophylactic or therapeutic antitumor immunity {see Timmerman and Levy, Ann. Rev. Med. 50:501-529, 1999). In general, dendritic cells may be identified based on their typical shape (stellate in situ, with marked cytoplasmic processes (dendrites) visible in vitro), their ability to take up process and present antigens with high efficiency and their ability to activate naive T cell responses. Dendritic cells may, of course, be engineered to express specific cell- surface receptors or ligands that are not commonly found on dendritic cells in vivo or ex vivo, and such modified dendritic cells are contemplated by the present invention. As an alternative to dendritic cells, secreted vesicles antigen-loaded dendritic cells (called exosomes) may be used within a vaccine {see Zitvogel et al., Nature Med. :594-600, 1998). Dendritic cells and progenitors may be obtained from peripheral blood, bone marrow, tumor-infiltrating cells, peritumoral tissues-infiltrating cells, lymph nodes, spleen, skin, umbilical cord blood or any other suitable tissue or fluid. For example, dendritic cells may be differentiated ex vivo by adding a combination of cytokines such as GM-CSF, IL-4, IL-13 and/or TNFα to cultures of monocytes harvested from peripheral blood. Alternatively, CD34 positive cells harvested from peripheral blood, umbilical cord blood or bone marrow may be differentiated into dendritic cells by adding to the culture medium combinations of GM-CSF, IL-3, TNFα, CD40 ligand, LPS, flt3 ligand and/or other compound(s) that induce maturation and proliferation of dendritic cells. Dendritic cells are conveniently categorized as "immature" and "mature" cells, which allows a simple way to discriminate between two well characterized phenotypes. However, this nomenclature should not be construed to exclude all possible intermediate stages of differentiation. Immature dendritic cells are characterized as APC with a high capacity for antigen uptake and processing, which correlates with the high expression of Fcγ receptor and mannose receptor. The mature phenotype is typically characterized by a lower expression of these markers, but a high expression of cell surface molecules responsible for T cell activation such as class I and class II MHC, adhesion molecules {e.g., CD54 and CD 11) and costimulatory molecules {e.g., CD40, CD80, CD86 and 4-1BB). APCs may generally be transfected with a polynucleotide encoding a Her-2/πew polypeptide such that the polypeptide, or an immunogenic portion thereof, is expressed on the cell surface. Such transfection may take place ex vivo, and a composition or vaccine comprising such transfected cells may then be used for therapeutic purposes, as described herein. Alternatively, a gene delivery vehicle that targets a dendritic or other antigen presenting cell may be administered to a patient, resulting in transfection that occurs in vivo. In vivo and ex vivo transfection of dendritic cells, for example, may generally be performed using any methods known in the art, such as those described in WO 97/24447, or the gene gun approach described by Mahvi et al., Immunology and cell Biology 75:456-460, 1997. Antigen loading of dendritic cells may be achieved by incubating dendritic cells or progenitor cells with the Her- 2/neu polypeptide, DNA (naked or within a plasmid vector) or RNA; or with antigen- expressing recombinant bacterium or viruses {e.g., vaccinia, fowlpox, adenovirus or lentivirus vectors). Prior to loading, the polypeptide may be covalently conjugated to an immunological partner that provides T cell help {e.g., a carrier molecule). Alternatively, a dendritic cell may be pulsed with a non-conjugated immunological partner, separately or in the presence of the polypeptide. Vaccines and pharmaceutical compositions may be presented in unit- dose or multi-dose containers, such as sealed ampoules or vials. Such containers are preferably hermetically sealed to preserve sterility of the formulation until use. In general, formulations may be stored as suspensions, solutions or emulsions in oily or aqueous vehicles. Alternatively, a vaccine or pharmaceutical composition may be stored in a freeze-dried condition requiring only the addition of a sterile liquid carrier immediately prior to use. In addition to direct in vivo procedures, ex vivo procedures may be used in which cells are removed from an animal, modified, and placed into the same or another animal. It will be evident that one can utilize any of the compositions noted above for introduction of HER-2/new nucleic acid molecules into tissue cells in an ex vivo context. Protocols for viral, physical and chemical methods of uptake are well known in the art. Accordingly, the present invention is useful for enhancing or eliciting, in a patient or cell culture, a cellular immune response (e.g., the generation of antigen- specific cytolytic T cells). As used herein, the term "patient" refers to any warmblooded animal, preferably a human. A patient may be afflicted with cancer, such as breast cancer, or may be normal (i.e., free of detectable disease and infection). A "cell culture" is any preparation of T cells or isolated component cells (including, but not limited to, macrophages, monocytes, B cells and dendritic cells). Such cells may be isolated by any of a variety of techniques well known to those of ordinary skill in the art (such as Ficoll-hypaque density centrifugation). The cells may (but need not) have been isolated from a patient afflicted with a ϊϊER-2/neu associated malignancy, and may be reintroduced into a patient after treatment. The following examples are offered by way of illustration and not by way of limitation. EXAMPLES Example 1 Priming of Her-2/neu Specific CD8+ T cells using Dendritic Cells Infected with Recombinant Adenovirus This Example illustrate the use of antigen-presenting cells within a vaccine for Her-2/neu positive tumors. An adenovirus (AdV) vector deleted for EIA and recombinant for the intracellular domain (ICD) of Her-2/neu was constructed and used to infect dendritic cells (DC) obtained from a healthy donor. Priming cultures were initiated that contained AdV-ICD-infected DC as stimulators and autologous PBMC as responders. Prior to the first restimulation, the culture was enriched for CD8+ cells, and the CD8+- enriched population was restimulations with AdV-ICD infected DC. Subsequent restimulations were on autologous fibroblasts transduced with a retrovirus recombinant for the ICD. Following the fourth in vitro stimulation, the resulting T cell line was tested for ICD-specific CTL activity by a standard 4 hour 51 Cr-release assay. As shown in Figure 1, the bulk T cell line contained activity specific for ICD, since the line lysed autologous B-LCL infected with vaccinia-ICD, but did not lyse C-LCL infected with vaccinia-EGFP or uninfected B-LCL targets. Each data point in Figure 1 was the average of three measurements. Following two more rounds of stimulation, the T cell line was tested for its ability to secrete γ-IFN in response to autologous fibroblasts expressing ICD. γ-IFN ELISPOT analysis was performed using the ICD-primed CD8+ T cell line as responders against autologous fibroblasts transduced with either ICD or EGFP. In this analysis, 2 x 10 3 fibroblasts stimulators were plated per well with 2 x 10 4 responding T cells per well, in triplicate. The average Elispot number for the triplicate wells were 344 on the ICD fibroblasts and 22 on the EGFP fibroblasts. Thus, the T cell line demonstrated ICD-specific γ-IFN secretion. To investigate the class I restriction of the CD8+ ICD-specific T cell line, antibody blocking experiments were performed using antibodies specific for various class I molecules. Stimulators were pre-incubated either with monoclonal antibody W6/32 (HLA-A, -B and -C reactive), monoclonal antibody BB123.2 (HLA-B and -C reactive) or monoclonal antibody BB7.2 (HLA-A2 specific). T cell responses were measured using a standard overnight γ-IFN Elispot assay. Responder cells were the ICD-specific CTL line cultured in vitro for seven stimulation cycles and used at 15,000 cells per well. Stimulators were autologous fibroblasts retrovirally transduced with either ICD or EGFP and used at 2,000 cells per well. Stimulators were incubated with the indicated mAb (50μg/mL) for 20 minutes prior to being added to the assay). The assays were performed in triplicate. As shown in Table 2, incubation of stimulator cells with either the W6/32 or BB123.2 antibodies completely blocked recognition of the ICD-transduced fibroblasts, whereas incubation with BB7.2 had no effect on γ-IFN secretion. These results indicate that the ICD-specific activity was restricted by an HLA-B or -C allele. Table 2 HLA-class I Antibody Blocking of ICD-specific γ-IFN Secretion An ICD-specific clone isolated from the bulk line was expanded and further characterized for its ability to recognize full-length Her-2/neu. Additionally, monoclonal antibodies specific for HLA Class I were used to examine the HLA- restriction of the clone. The experiment was a standard, overnight γ-IFN Elispot assay. Responder cells were the ICD-specific T cell clone, 17D5. Stimulators were autologous fibroblasts either untransduced or retrovirally transduced with either EGFP, ICD or full length Her2/neu (H2N). 10,000 17D5 cells and 10,000 stimulators were used per well. Antibodies were used at 25 μg/mL in the assay. The assay was performed in triplicate, and standard deviations were between 0 and +/- 18 for triplicates. As shown in Table 3, the clone specifically recognized autologous fibroblasts transduced with ICD or full length Her-2/neu, but not untransduced fibroblasts or fibroblasts transduced with the irrelevant antigen EGFP. Furthermore, this reactivity was completely blocked by the addition of the pan-HLA Class I monoclonal antibody w6/32 and by a monoclonal antibody specific for HLA-B and -C alleles (BB123.2), but not by an antibody specific for HLA-A2 (BB7.2). These results indicate that this Her2/neu-specific clone was restricted by an HLA-B or -C allele, the same pattern of HLA restriction observed for the bulk cell line from which the clone was derived. Further analyses indicated that the response was restricted by HLA- B4402. These analyses were performed by testing the ability of clone 17D5 to recognize a panel of allogeneic fibroblasts matched at different HLA-B and -C alleles and infected with AdV-ICD or AdV-EGFP. Autologous fibroblasts, either transduced with recombinant retroviruses or infected with recombinant AdV were used as controls. Table 3 γ-IFN Elispot Assay Testing Her-2/neu Reactivity HLA-Restriction of the ICD-specific Clone 17DS The Her-2/neu specific clone was tested for its ability to recognize human tumor cells expressing Her-2/neu. The breast carcinoma cell line MCF-7 naturally expresses low levels of Her-2/neu at the cell surface and is also HLA-b4402. Upon transduction of MCF-7 with a retrovirus recombinant for Her-2/neu, surface levels of Her-2/neu increased about 5 -fold as measured by flow cytometric analysis following staining with a Her-2/neu specific monoclonal antibody. Infection of MCF-7 cells with AdV-Her-2/neu resulted in a 20-fold increase of surface Her-2/neu on the tumor cells. These results are depicted in Figure 2. The T cell clone secreted γ-IFN in response to MCF-7 cells infected with the adenovirus encoding Her-2/neu. The clone did not, however, appear to recognize MCF-7 cells or MCF-7 cells transduced with the retrovirus expressing Her-2/neu. Since the clone does recognize human fibroblasts transduced with either ICD or Her2/neu, and since the transduced fibroblasts express similar levels of protein as the transduced MCF-7 cells, it is unlikely that this result is due solely to levels of expression of the antigen. These results support the use of antigen-presenting cells expressing an immunogenic Her2/neu polypeptide for her2/neu based cancer immunotherapy. All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually incorporated by reference. From the foregoing, it will be evident 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.

Claims: CLAIMS 1. An isolated antigen-presenting cell that expresses at least an immunogenic portion of a polypeptide encoded by a DNA sequence selected from: (a) nucleotides 2026 through 3765 of SEQ ID NO: 1 ; and (b) DNA sequences that hybridize to a nucleotide sequence complementary to nucleotides 2026 through 3765 of SEQ ID NO:l under moderately stringent conditions, wherein the DNA sequence encodes a polypeptide that produces an immune response to ER-2/neu protein. 2. An isolated antigen-presenting cell that expresses at least an immunogenic portion of a polypeptide having the amino acid sequence of SEQ ID NO:2 from lysine, amino acid 676, through valine, amino acid 1255, or a variant thereof that produces at least an equivalent immune response. 3. A pharmaceutical composition comprising an antigen-presenting cell according to claim 1 or claim 2, in combination with a pharmaceutically acceptable carrier or excipient. 4. A pharmaceutical composition according to claim 3, wherein the antigen presenting cell is a dendritic cell or a macrophage. 5. A vaccine comprising an antigen-presenting cell according to claim 1 or claim 2, in combination with a non-specific immune response enhancer. 6. A vaccine according to claim 5, wherein the non-specific immune response enhancer is an adjuvant. 7. A vaccine according to claim 5, wherein the non-specific immune response enhancer induces a predominantly Type I response. 8. A vaccine according to claim 5, wherein the antigen-presenting cell is a dendritic cell. 9. A method for inhibiting the development of a cancer in a patient, comprising administering to a patient an effective amount of an antigen-presenting cell according to claim 1 or claim 2, and thereby inhibiting the development of a cancer in the patient. 10. A method according to claim 9, wherein the antigen-presenting cell is a dendritic cell. 11. A method according to claim 7 or claim 8, wherein the cancer is breast cancer.

Inventors: CHEEVER MARTIN A, HAND-ZIMMERMANN SUSAN, CHEEVER, MARTIN, A., HAND-ZIMMERMANN, SUSAN
Applicants: CHEEVER MARTIN A, CORIXA CORP, HAND ZIMMERMANN SUSAN, CHEEVER, MARTIN, A., CORIXA CORPORATION, HAND-ZIMMERMANN, SUSAN
Application year: 2001
Main classification: C12N5
IPC codes: A61K39, A61K47