HERV-k envelope protein binders and compositions and methods of use thereof

Abstract

Antibodies and other molecules including an antigen binding region of an antibody that immunospecifically binds to a surface unit or a transmembrane unit of a Human endogenous retrovirus-K (HERV-K) Env protein are provided. The antibodies and other molecules typically include six complementarity determining regions (CDRs). In preferred forms the antibodies and other molecules immunospecifically bind to the amino acid sequence SEQ ID NO:223 and / or 224. Chimeric antigen receptors (CAR) formed using the provided antibodies are also provided, as are cell expressing the CAR. Methods of detecting HERV-K Env, and use thereof of various other methods such as diagnostic methods are also provided. Method of treatment for HERV-K Env protein-related diseases and disorders are also provided.

Description

[0001]HERV-K ENVELOPE PROTEIN BINDERS AND COMPOSITIONS AND METHODS OF USE THEREOF CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of and priority to U.S.S.N.63 / 638,067 filed April 24, 2024, each of which is specifically incorporated by reference in its entirety. REFERENCE TO SEQUENCE LISTING The Sequence Listing XLM submitted as a file named “LJI2024-102-02PCT” created on April 21, 2025, and having a size of 202,943 bytes is hereby incorporated by reference pursuant to 37 C.F.R. § 1.834(c)(1). FIELD OF THE INVENTION The field of the invention is generally directed to HERV-K binding proteins, including but not limited to antibodies, and use thereof in HERV-K related research and therapy. BACKGROUND OF THE INVENTION The human genome contains a large number of retroviral elements acquired over the process of evolution, and although historically considered “junk DNA,” identification of roles of these elements in human physiology and pathologies are beginning to emerge (Garcia-Montojo, et al., “Human endogenous retrovirus-K (HML-2): a comprehensive review.”, Crit Rev Microbiol.2018 Nov;44(6):715-738. doi: 10.1080 / 1040841X.2018.1501345. Epub 2018 Oct 14. PMID: 30318978; PMCID: PMC6342650. The most recently acquired, human endogenous retrovirus-K (HERV-K), has multiple copies in the human genome and some of them have complete open reading frames that are transcribed and translated, especially in early embryogenesis. Phylogenetically, HERV-K is considered a supergroup of viruses. One of the subtypes, termed HML-2, seems to be the most active and hence, it is the best studied. Aberrant expression of HML-2 in adult tissues has been associated with certain types of cancer and with neurodegenerative diseases. Despite identification of an increasing number of roles in human development and health, research and therapeutic agent development is lagging in availability and effectiveness. Only two HERV-K monoclonal antibodies are commercially available. These antibodies are derived from mice immunization with protein produced in bacteria, which is not glycosylated and is likely misfolded. Thus, there remains a need for improvement in this area. It is therefore an object of the invention to provide compositions that specifically bind to HERV-K, and methods of use thereof.45728747v11 SUMMARY OF THE INVENTION Antibodies and other molecules including an antigen binding region of an antibody that immunospecifically binds to a surface unit or a transmembrane unit of a Human endogenous retrovirus-K (HERV-K) Env protein are provided. The antibodies and other molecules typically include six complementarity determining regions (CDRs). In preferred forms the antibodies and other molecules immunospecifically bind to the amino acid sequence SEQ ID NO:223 and / or 224. In some forms, the antigen binding region includes six complementarity determining regions (CDRs), wherein the CDRs include at least one CDR of the CDRs of anti-HERV-K Env antibody Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; with all remaining CDRs independently selected from anti-HERV-K Env antibodies Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. In some forms, the CDRs include three heavy chain variable region CDRs independently selected from the heavy chain variable region CDRs of anti-HERV-K Env antibodies Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto in combination with three light chain variable region CDRs independently selected from the light chain variable region CDRs of anti-HERV-K Env antibodies Kenv-1, Kenv-2, Kenv- 3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. In some forms, the CDRs include the three heavy chain variable region CDRs of anti- HERV-K Env antibody Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14,or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto in combination with the three light chain variable region CDRs for anti-HERV-K Env antibody Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14 or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. Thus disclosed are antibodies and other molecules wherein the six CDRs are (A) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-1; (B) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-2;45728747v12 (C) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-3; (D) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-4; (E) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-5; (F) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-6; (G) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-7; (H) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-8; (I) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-9; (J) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-10; (K) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-11; (L) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-12; (M) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-13; or (N) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-14. In some forms, the six CDRs are oriented and in the same orientation as in the anti-HERV- K ENV antibody from which they were selected. In some forms, the Kenv-1-to-14 heavy and light chain variable regions are the variable region sequences according to Tables 2, 3, 7, and / or 8, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. In some forms, the six CDRs have sequences according to the CDRs of Tables 1 and / or 6 or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. Thus provided are antibodies and other molecules including a heavy chain variable region including three CDRs and a light chain variable region including three CDRs, wherein45728747v13 (A) the three heavy chain variable region CDRs include GFTFNTYA (SEQ ID NO:1), IRSKSNYYAT (SEQ ID NO:2), VRDYGAY (SEQ ID NO:3), respectively, and the three light chain variable region CDRs include QDINSF (SE QID NO:4), RAN, LQYYEFLPT (SEQ ID NO:5) respectively; (B) the three heavy chain variable region CDRs include GYSIASGYS (SEQ ID NO:6), IHFSGNT (SEQ ID NO:7), ARGARNGNPYWYLDV (SEQ ID NO:8), respectively, and the three light chain variable region CDRs include QSISDY (SEQ ID NO:9), YAS, QNGRTFPFT (SEQ ID NO:10), respectively; (C) the three heavy chain variable region CDRs include GFSLSTSNMG (SEQ ID NO:11), ILWNDSK (SEQ ID NO:12), ARIARYHYAGSSWYFDV (SEQ ID NO:13), respectively, and the three light chain variable region CDRs include QGISNY (SEQ ID NO:14), YTS, QQYSKLPYT (SEQ ID NO:15), respectively; (D) the three heavy chain variable region CDRs include GYSITSDYA (SEQ ID NO:16), ISYSGST (SEQ ID NO:17), ARSVILGAWFAY (SEQ ID NO:18), respectively, and the three light chain variable region CDRs include SSITY (SEQ ID NO:19), LTS, QQWSSNPLT (SEQ ID NO:20), respectively; (E) the three heavy chain variable region CDRs include GYSITSDYA (SEQ ID NO:16), ISYSGTT (SEQ ID NO:21), ARLGFW (SEQ ID NO:22), respectively, and the three light chain variable region CDRs include ESVDNYGISF (SEQ ID NO:23), AAS, QQSKEIPYT (SEQ ID NO:24), respectively; (F) the three heavy chain variable region CDRs include GYTFTNYG (SEQ ID NO:25), INTYTGEP (SEQ ID NO:26), AKYYDGYYGWYFDV (SEQ ID NO:27), respectively, and the three light chain variable region CDRs include ESVDSYGNSF (SEQ ID NO:28), RAS, QQSYEDPYT (SEQ ID NO:29), respectively; (G) the three heavy chain variable region CDRs include GFSFTVYG (SEQ ID NO:30), IWGDGRT (SEQ ID NO:31), ARRNGYYAMDY (SEQ ID NO:32), respectively, and the three light chain variable region CDRs include ENIYSN (SEQ ID NO:33), AAT, QHFWGTPYT (SEQ ID NO:34), respectively; (H) the three heavy chain variable region CDRs include GFSXSTSNMG (SEQ ID NO:35), ILWNDSK (SEQ ID NO:12), ARIARYHYACISFYFEV (SEQ ID NO:36), respectively, and the three light chain variable region CDRs include QSLVHSNGNTY (SEQ ID NO:37), KVS, SQSTHVPLT (SEQ ID NO:38), respectively; (I) the three heavy chain variable region CDRs include GYTFTNYY (SEQ ID NO:39), INPSNGDT (SEQ ID NO:40), TRFRSPFYYAMDY (SEQ ID NO:41), respectively, and the three45728747v14 light chain variable region CDRs include QSLVHSNGNTY (SEQ ID NO:37), KVS, SQSTHVPLT (SEQ ID NO:38), respectively; (J) the three heavy chain variable region CDRs include GYTFTEYI (SEQ ID NO:42), VNPNNGGP (SEQ ID NO:43), TKGDY (SEQ ID NO:44), respectively, and the three light chain variable region CDRs include QEISGY (SEQ ID NO:45), AAS, LQYASYPFT (SEQ ID NO:46), respectively; (K) the three heavy chain variable region CDRs include GYSFTDYF (SEQ ID NO:47), INPYNGDT (SEQ ID NO:48), ARNGYYRYYFDY (SEQ ID NO:49), respectively, and the three light chain variable region CDRs include SSVNY (SEQ ID NO:50), EIS, QQWNYPLT (SEQ ID NO:51), respectively; (L) the three heavy chain variable region CDRs include GYTFTEYT (SEQ ID NO:52), FIPSNGNT (SEQ ID NO:53), TRRPYYYGSGYWYFDF (SEQ ID NO:54), respectively, and the three light chain variable region CDRs include QDVRTS (SEQ ID NO:55), STS, QQHYSTPYT (SEQ ID NO:56), respectively; (M) the three heavy chain variable region CDRs include GYSIPSDYA (SEQ ID NO:57), ISSSGST (SEQ ID NO:58), ASYDNDNVY (SEQ ID NO:59), respectively, and the three light chain variable region CDRs include QSLLNSRTRKNY (SEQ ID NO:60), WAS, KQSYNLWT (SEQ ID NO:61), respectively. In some forms, the antigen binding region includes the heavy chain variable region of Kenv- 1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv- 12, Kenv-13, Kenv-14, optionally according to Table 4, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; the light chain variable region of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv- 13, Kenv-14, optionally according to Table 9, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; or a combination thereof. In some forms the molecule includes the heavy chain V-D-J regions of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv- 13, Kenv-14, optionally according to Table 5, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; the light chain V-J regions of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, optionally according to Table 10, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto, or a combination thereof. The antibody can be, e.g., an intact antibody and functional antibody fragment or fusion protein. Functional fragment and fusion proteins include, for example, Fab fragments, F(ab')245728747v15 fragments, Fab' fragments, Fv fragments, recombinant IgG (rlgG) fragments, single chain antibody fragments optionally single chain variable fragments (scFv), and single region antibodies optionally selected from sdAb, sdFv, and nanobody fragments. In some forms, the antibody is selected from intrabodies, peptibodies, chimeric antibodies, fully human antibodies, humanized antibodies, and heteroconjugate antibodies, and multispecific antibodies optionally selected bispecific antibodies, diabodies, triabodies, tetrabodies, tandem di-scFv, and tandem tri-scFv. The antibody can be an IgM, IgE, IgA, IgD, or IgG optionally an IgG1, IgG2, IgG3, or IgG4. In some forms, the molecule or antibody is detectably labeled or includes a conjugated toxin, drug, receptor, enzyme, receptor ligand. Fusion proteins include the molecule or antibody and a heterologous amino acid sequence are also provided. A preferred example is a chimeric antigen receptor (CAR) polypeptide including the molecule or antibody, typically as its antigen binding domain. In some forms, the CAR includes an extracellular antigen binding region, a spacer region, a transmembrane region, and intracellular signaling region, and optionally further includes a co-stimulatory region. Nucleic acid encoding the molecules, antibodies, fusion proteins and CARs are also provided. In some forms, the nucleic acid includes an expression control sequence operably linked thereto, optionally wherein the expression control sequence includes a promoter. The nucleic acid can be, for example, an mRNA or a vector. Host cells including and / or expressing molecules, antibodies, fusion proteins, CARs, and nucleic acids encoding the same are also provided. In a particular forms, the host cell is an immune cell, such as a T cell, including a CAR. Pharmaceutical compositions including the CAR immune cells, or the molecules or antibodies, optionally wherein the molecule or antibody includes a drug conjugated thereto and / or has antibody-dependent cell-mediated cytotoxicity (ADCC) activity, or complement-dependent cytotoxicity activity (CDC), and / or is a bispecific immune cell engager are also provided, and can be used in methods of treatment. The method of treatment typically including administering a subject in need thereof an effective amount of pharmaceutical composition. In some forms, the subject has a disease or disorder caused by or characterized by increased presence of HERV-K Env protein or a fragment thereof. In some forms, the subject has a cancer, a neurological disorder, an immunodeficiency, an autoimmune disease, or HIV. Thus, methods of treating cancers, neurological disorders, immunodeficiencies, autoimmune diseases, and HIV with the disclosed compositions are provided. In some forms, the subject has cancer and HERV-K Env protein or fragment thereof is an antigen of the cancer cells.45728747v16 Methods of detecting HERV-K Env protein or fragment thereof are also provided and typically include contacting a biological sample with one or more of the disclosed molecules or antibodies and detecting binding between the molecule(s) and / or antibod(ies) and the HERV-K Env protein or fragment thereof. In some forms, the methods include determining that the sample includes increased HERV- K Env protein or fragment thereof if the level of detected binding is higher in the biological sample than in a control. Binding can be detected by, for example, an immunoassay, immunohistochemistry, Western blotting, surface plasmon resonance, flow cytometry (FACS) analysis, or a biochip. The immunoassay can be, for example, an enzyme immunoassay (EIA), radioimmunoassay (RIA), fluoroimmunoassay (FIA), chemiluminescent immunoassay (CLIA) and counting immunoassay (CIA), homogeneous enzyme-multiplied immunoassays (“EMIT”), apoenzyme reactivation immunoassay (“ARIS”), dipstick immunoassays, or immuno-chromatography assays. The biological sample can be, for example, cells or a cell lysate or a fraction thereof, for a fluid such as blood, saliva, or urine. In some forms, the cells or cell lysate or fraction thereof are derived from a biopsy from a subject. In some forms, the biopsy contains or is suspected of containing tumor cells. In some forms, the biopsy is a tumor biopsy. Methods of diagnosing a subject with a HERV-K Env protein-related disease or disorder are also provided and can include detecting HERV-K Env protein or fragment thereof according to the provided methods of detection. In some forms, the HERV-K Env protein-related disease or disorder is a cancer, a neurological disorder, an immunodeficiency, an autoimmune disease, or HIV. Such methods can further include treating the subject, typically with a therapy effective for treating an HERV-K Env protein-related disease and disorder, such as the treatments mentioned above and elsewhere herein e.g., administration of an antiviral. BRIEF DESCRIPTION OF THE DRAWING Figure 1 is an image of immunofluorescence staining of isolated neutrophils from either SLE, RA, or healthy donors using mAbs from this study. Neutrophils from RA samples were treated with IFNα prior to fixation. Healthy neutrophils isolated with or without IFNα treatment show no staining by any mAb. Figure 2 is a heat map showing ELISA data collected using various Kenv antibodies and soluble env as the antigen (containing both surface unit (SU) and transmembrane unit (TM)). Figure 3A is a pair of images of 2D classes of Kenv-6 cleaved Fabs bound to HERV-K Env antigen obtained via negative-stain electron microscopy. Figure 3B is a 3D ab-initio reconstruction of Kenv-6 Fabs bound to Env. Representative Fabs (“wings”) and an AlphaFold predicted model of45728747v17 HERV-K Env trimer (“center”) are fit into the density obtained. Figures 4A and 4B are side view (Fig.4A) and top down view (Fig.4B) illustrations of a Ab-initio 3D reconstruction of the HERV-K Env TM domain bound to 3 copies of Kenv-4 Fab from cryo-electron microscopy. An AlphaFold predicted post-fusion TM model is docked into the density. DETAILED DESCRIPTION OF THE INVENTION I. Definitions As used herein, the term “binds” in reference to the interaction of a binding protein and an antigen means that the interaction is dependent upon the presence of a particular structure (e.g., an antigenic determinant or epitope) on the antigen. For example, a binding protein recognizes and binds to a specific antigen structure rather than to antigens generally. For example, if a binding protein binds to epitope "A", the presence of a molecule containing epitope “A” (or free, unlabeled “A”), in a reaction containing labeled “A” and the binding protein, will reduce the amount of labeled “A” bound to the binding protein. As used herein, a molecule is said to be able to “immunospecifically bind” a second molecule if such binding exhibits the specificity and affinity of an antibody to its cognate antigen. Antibodies are said to be capable of “immunospecifically binding” to a target region or conformation (“epitope”) of an antigen (and in particular, an antigen of HERV-K such as the env protein) if such binding involves the antigen recognition site of the immunoglobulin molecule. An antibody that immunospecifically binds to a particular antigen may bind to other antigens with lower affinity if the other antigen has some sequence or conformational similarity that is recognized by the antigen recognition site as determined by, e.g., immunoassays, BIACORE® assays, or other assays known in the art, but would not bind to a totally unrelated antigen. Preferably, however, antibodies (and their antigen binding fragments) will not cross-react with other antigens. Antibodies may also bind to other molecules in a way that is not immunospecific, such as to FcR receptors, by virtue of binding domains in other regions / domains of the molecule that do not involve the antigen recognition site, such as the Fc region. The term “substantially,” as used in the context of binding or exhibited effect, is intended to denote that the observed effect is physiologically or therapeutically relevant. Similarly, a molecule is said to have substantially the same immunospecificity and / or characteristic as another molecule, if such immunospecificities and characteristics are greater than 60% identical, greater than 70% identical, greater than 75% identical, greater than 80% identical, greater than 85% identical, greater than 90% identical, greater than 95% identical, or greater than 97% identical).45728747v18 The term “antibody” is used in the broadest sense unless clearly indicated otherwise. Therefore, an "antibody" can be naturally occurring or man-made such as monoclonal antibodies produced by conventional hybridoma technology. Antibodies include monoclonal and polyclonal antibodies as well as fragments and polymers containing the antigen binding domain and / or one or more complementarity determining regions of these antibodies. As used herein, the term "antibody" refers to any form of antibody or antigen binding fragment or recombinant protein, and specifically covers monoclonal antibodies (including full length monoclonal antibodies), polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies), and antibody fragments so long as they specifically bind the target antigen. Any specific antibody can be used in the methods and compositions provided herein. The term “antibody” encompasses an immunoglobulin molecule that possesses a “variable region” antigen recognition site. Thus, the term "antibody" encompasses a molecule having at least one variable region from a light chain immunoglobulin molecule and at least one variable region from a heavy chain molecule that in combination form a specific binding site for the target antigen. The term antibody includes monoclonal antibodies, multi-specific antibodies, human antibodies, humanized antibodies, synthetic antibodies, chimeric antibodies, camelized antibodies (See e.g., Muyldermans et al., 2001, Trends Biochem. Sci.26:230; Nuttall et al., 2000, Cur. Pharm. Biotech.1:253; Reichmann and Muyldermans, 1999, J. Immunol. Meth. 231:25; International Publication Nos. WO 94 / 04678 and WO 94 / 25591; U.S. Patent No. 6,005,079), single-chain Fvs (scFv) (see, e.g., see Pluckthun in The Pharmacology of Monoclonal Antibodies, vol.113, Rosenburg and Moore eds. Springer-Verlag, New York, pp.269-315 (1994)), single chain antibodies, disulfide-linked Fvs (sdFv), intrabodies, and anti-idiotypic (anti-Id) antibodies (including, e.g., anti-Id and anti-anti-Id antibodies to the disclosed antibodies). In particular, such antibodies include immunoglobulin molecules of any type (e.g., IgG, IgE, IgM, IgD, IgA and IgY), class (e.g., IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2) or subclass. The term “variable region” is intended to distinguish such domain of the immunoglobulin from domains that are broadly shared by antibodies (such as an antibody Fc domain). The variable region refers to the portions of the light and / or heavy chains of an antibody as defined herein that specifically binds to an antigen and, for example, includes amino acid sequences of CDRs; i.e., CDRl, CDR2, and CDR3, and framework regions (FRs). For example, the variable region can include three or four FRs (e.g., FR1, FR2, FR3 and optionally FR4) together with three CDRs. VH refers to the variable region of the heavy chain. VL refers to the variable region of the light chain. The variable region includes a “hypervariable region” whose residues are responsible for antigen binding.45728747v19 The hypervariable region includes amino acid residues from a “Complementarity Determining Region” or “CDR” (e.g., typically at approximately residues 24-34 (L1), 50-56 (L2) and 89-97 (L3) in the light chain variable domain and at approximately residues 27-35 (H1), 50-65 (H2) and 95-102 (H3) in the heavy chain variable domain according to Kabat; Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, MD. (1991)) and / or those residues from a “hypervariable loop” (e.g., residues 26-32 (L1), 50-52 (L2) and 91-96 (L3) in the light chain variable domain and 26-32 (H1), 53-55 (H2) and 96-101 (H3) in the heavy chain variable domain according to Chothia; Chothia and Lesk, 1987, J. Mol. Biol.196:901-917). Conventions that include corrections or alternate numbering systems for variable domains include not only Kabat and Chothia, but also IMGT (Lefranc, et al. (2003), Dev Comp Immunol 27: 55- 77), Chothia (Chothia C, Lesk AM (1987), J Mal Biol 196: 901-917; Chothia, et al. (1989), Nature 342: 877-883) and AHo (Honegger A, Plückthun A (2001) J Mol Biol 309: 657-670). For convenience, examples of binding proteins of the present disclosure may also be labelled according to Kabat, Chothia, or IMGT. These examples are expressly indicated as such. “Framework Region” or “FR” residues are those variable domain residues other than the hypervariable region residues as herein defined. As used herein, the term “antigen binding fragment” of an antibody refers to one or more portions of an antibody that contain the antibody’s Complementarity Determining Regions (“CDRs”) and optionally the framework residues that include the antibody’s “variable region” antigen recognition site, and exhibit an ability to immunospecifically bind antigen. Such fragments include Fab, Fab', F(ab')2 and Fv fragments; diabodies; linear antibodies; single-chain antibody molecules and multispecific antibodies formed from antibody fragments, and mutants thereof, naturally occurring variants, and fusion proteins including the antibody’s “variable region” antigen recognition site and a heterologous protein (e.g., a toxin, an antigen recognition site for a different antigen, an enzyme, a receptor or receptor ligand, etc.). For example, the term antigen binding fragment may be used to refer to recombinant single chain Fv fragments (scFv) as well as divalent (di-scFv) and trivalent (tri-scFV) forms thereof. Such fragments can be produced via various methods known in the art. The term “constant region” as used herein, refers to a portion of heavy chain or light chain of an antibody other than the variable region. In a heavy chain, the constant region generally includes a plurality of constant domains and a hinge region, e.g., an IgG constant region includes the following linked components, a constant heavy CH1, a linker, a CH2 and a CH3. In a heavy chain, a45728747v110 constant region includes a Fc. In a light chain, a constant region generally include one constant domain (a CL1). The term “fragment crystalizable” or “Fc” or “Fc region” or “Fc portion” (which can be used interchangeably herein) refers to a region of an antibody including at least one constant domain and which is generally (though not necessarily) glycosylated and which is capable of binding to one or more Fc receptors and / or components of the complement cascade. The heavy chain constant region can be selected from any of the five isotypes: α, δ, ε, γ, or μ. Exemplary heavy chain constant regions are gamma 1 (IgG1), gamma 2 (IgG2) and gamma 3 (IgG3), or hybrids thereof. A “constant domain” is a domain in an antibody the sequence of which is highly similar in antibodies / antibodies of the same type, e.g., IgG or IgM or IgE. A constant region of an antibody generally includes a plurality of constant domains, e.g., the constant region of γ, α or δ heavy chain include two constant domains. The terms “full-length antibody”, “intact antibody” or “whole antibody” are used interchangeably to refer to an antibody in its substantially intact form, as opposed to an antigen binding fragment of an antibody. Specifically, whole antibodies include those with heavy and light chains including an Fc region. The constant domains may be wild-type sequence constant domains (e.g., human wild-type sequence constant domains) or amino acid sequence variants thereof. A “chimeric antibody” is a molecule in which different portions of the antibody are derived from different immunoglobulin molecules such as antibodies having a variable region derived from a non-human antibody and a human immunoglobulin constant region. Methods for producing chimeric antibodies are known in the art. See e.g., Morrison, 1985, Science 229:1202; Oi et al., 1986, BioTechniques 4:214; Gillies et al., 1989, J. Immunol. Methods 125:191-202; and U.S. Patent Nos.6,311,415, 5,807,715, 4,816,567, and 4,816,397. Chimeric antibodies including one or more CDRs from a non-human species and framework regions from a human immunoglobulin molecule can be produced using a variety of techniques known in the art including, for example, CDR-grafting (EP 239,400; International Publication No. WO 91 / 09967; and U.S. Patent Nos.5,225,539, 5,530,101, and 5,585,089), veneering or resurfacing (EP 592,106; EP 519,596; Padlan, 1991, Molecular Immunology 28(4 / 5):489-498; Studnicka et al., 1994, Protein Engineering 7:805; and Roguska et al., 1994, Proc. Natl. Acad. Sci. USA 91:969), and chain shuffling (U.S. Patent No.5,565,332). As used herein, the term “humanized antibody” refers to an immunoglobulin including a human framework region and one or more CDR’s from a non-human (usually a mouse or rat) immunoglobulin. The non-human immunoglobulin providing the CDR's is called the “donor” and the human immunoglobulin providing the framework is called the “acceptor.”45728747v111 As used herein, the term “fragment” refers to a peptide or polypeptide including an amino acid sequence of at least 5 contiguous amino acid residues, at least 10 contiguous amino acid residues, at least 15 contiguous amino acid residues, at least 20 contiguous amino acid residues, at least 25 contiguous amino acid residues, at least 40 contiguous amino acid residues, at least 50 contiguous amino acid residues, at least 60 contiguous amino residues, at least 70 contiguous amino acid residues, at least 80 contiguous amino acid residues, at least 90 contiguous amino acid residues, at least 100 contiguous amino acid residues, at least 125 contiguous amino acid residues, at least 150 contiguous amino acid residues, at least 175 contiguous amino acid residues, at least 200 contiguous amino acid residues, or at least 250 contiguous amino acid residues. As used herein, the term “fusion protein” refers to a polypeptide formed by the joining of two or more polypeptides through a peptide bond formed between the amino terminus of one polypeptide and the carboxyl terminus of another polypeptide or through linking of one polypeptide to another through reactions between amino acid side chains (for example disulfide bonds between cysteine residues on each polypeptide). The fusion protein can be formed by the chemical coupling of the constituent polypeptides or it can be expressed as a single polypeptide from a nucleic acid sequence encoding the single contiguous fusion protein. Fusion proteins can be prepared using conventional techniques in molecular biology to join the two genes in frame into a single nucleic acid sequence, and then expressing the nucleic acid in an appropriate host cell under conditions in which the fusion protein is produced. As used herein, the term “variant” refers to a polypeptide or polynucleotide that differs from a reference polypeptide or polynucleotide, but retains essential properties. A typical variant of a polypeptide differs in amino acid sequence from another, reference polypeptide. Generally, differences are limited so that the sequences of the reference polypeptide and the variant are closely similar overall and, in many regions, identical. A variant and reference polypeptide may differ in amino acid sequence by one or more modifications (e.g., substitutions, additions, and / or deletions). A substituted or inserted amino acid residue may or may not be one encoded by the genetic code. A variant of a polypeptide may be naturally occurring such as an allelic variant, or it may be a variant that is not known to occur naturally. Modifications and changes can be made in the structure of the polypeptides of the in disclosure and still obtain a molecule having similar characteristics as the polypeptide (e.g., a conservative amino acid substitution). For example, certain amino acids can be substituted for other amino acids in a sequence without appreciable loss of activity. Because it is the interactive capacity and nature of a polypeptide that defines that polypeptide’s biological functional activity,45728747v112 certain amino acid sequence substitutions can be made in a polypeptide sequence and nevertheless obtain a polypeptide with like properties. In making such changes, the hydropathic index of amino acids can be considered. The importance of the hydropathic amino acid index in conferring interactive biologic function on a polypeptide is generally understood in the art. It is known that certain amino acids can be substituted for other amino acids having a similar hydropathic index or score and still result in a polypeptide with similar biological activity. Each amino acid has been assigned a hydropathic index on the basis of its hydrophobicity and charge characteristics. Those indices are: isoleucine (+4.5); valine (+4.2); leucine (+3.8); phenylalanine (+2.8); cysteine / cystine (+2.5); methionine (+1.9); alanine (+1.8); glycine (-0.4); threonine (-0.7); serine (-0.8); tryptophan (-0.9); tyrosine (- 1.3); proline (-1.6); histidine (-3.2); glutamate (-3.5); glutamine (-3.5); aspartate (-3.5); asparagine (-3.5); lysine (-3.9); and arginine (-4.5). It is believed that the relative hydropathic character of the amino acid determines the secondary structure of the resultant polypeptide, which in turn defines the interaction of the polypeptide with other molecules, such as enzymes, substrates, receptors, antibodies, antigens, and cofactors. It is known in the art that an amino acid can be substituted by another amino acid having a similar hydropathic index and still obtain a functionally equivalent polypeptide. In such changes, the substitution of amino acids whose hydropathic indices are within ± 2 is preferred, those within ± 1 are particularly preferred, and those within ± 0.5 are even more particularly preferred. Substitution of like amino acids can also be made on the basis of hydrophilicity, particularly where the biological functional equivalent polypeptide or peptide thereby created is intended for use in immunological embodiments. The following hydrophilicity values have been assigned to amino acid residues: arginine (+3.0); lysine (+3.0); aspartate (+3.0 ± 1); glutamate (+3.0 ± 1); serine (+0.3); asparagine (+0.2); glutamine (+0.2); glycine (0); proline (-0.5 ± 1); threonine (-0.4); alanine (-0.5); histidine (-0.5); cysteine (-1.0); methionine (-1.3); valine (-1.5); leucine (-1.8); isoleucine (- 1.8); tyrosine (-2.3); phenylalanine (-2.5); tryptophan (-3.4). It is understood that an amino acid can be substituted for another having a similar hydrophilicity value and still obtain a biologically equivalent, and in particular, an immunologically equivalent polypeptide. In such changes, the substitution of amino acids whose hydrophilicity values are within ± 2 is preferred, those within ± 1 are particularly preferred, and those within ± 0.5 are even more particularly preferred. As outlined above, amino acid substitutions are generally based on the relative similarity of the amino acid side-chain substituents, for example, their hydrophobicity, hydrophilicity, charge, size, and the like. Exemplary substitutions that take various of the foregoing characteristics into consideration are well known to those of skill in the art and include (original residue: exemplary45728747v113 substitution): (Ala: Gly, Ser), (Arg: Lys), (Asn: Gln, His), (Asp: Glu, Cys, Ser), (Gln: Asn), (Glu: Asp), (Gly: Ala), (His: Asn, Gln), (Ile: Leu, Val), (Leu: Ile, Val), (Lys: Arg), (Met: Leu, Tyr), (Ser: Thr), (Thr: Ser), (Tip: Tyr), (Tyr: Trp, Phe), and (Val: Ile, Leu). Embodiments of this disclosure thus contemplate functional or biological equivalents of a polypeptide as set forth above. In particular, embodiments of the polypeptides can include variants having about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, or more sequence identity to the polypeptide of interest. "Percent (%) amino acid sequence identity" with respect to a reference polypeptide sequence is defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the reference polypeptide sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill of those practicing in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN or Megalign (DNASTAR) software. Those skilled in the art can determine appropriate parameters for aligning sequences, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared. As used herein, the term “tumor” or “neoplasm” refers to an abnormal mass of tissue containing neoplastic cells. Neoplasms and tumors may be benign, premalignant, or malignant. As used herein, the term “cancer” or “malignant neoplasm” refers to a cell that displays uncontrolled growth and division, invasion of adjacent tissues, and often metastasizes to other locations of the body. As used herein, the term “antineoplastic” refers to a composition, such as a drug or biologic, that can inhibit or prevent cancer growth, invasion, and / or metastasis. As used herein, the phrase “pharmaceutically acceptable” refers to compositions, polymers and other materials and / or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit / risk ratio. As used herein, the phrase “pharmaceutically acceptable carrier” refers to pharmaceutically acceptable materials, compositions or vehicles, such as a liquid or solid filler, diluent, solvent or encapsulating material involved in carrying or transporting any subject composition, from one organ, or portion of the body, to another organ, or portion of the body. Each carrier must be “acceptable” in the sense of being compatible with the other ingredients of a subject composition and not injurious to the patient.45728747v114 As used herein, the term “individual,” “subject,” and “patient” are used interchangeably to refer to any individual who is the target of administration or treatment. The subject can be a vertebrate, for example, a mammal. Thus, the subject can be a human or veterinary patient. As used herein, the term “treatment” refers to the medical management of a patient with the intent to cure, ameliorate, stabilize, or prevent a disease, pathological condition, or disorder. This term includes active treatment, that is, treatment directed specifically toward the improvement of a disease, pathological condition, or disorder, and also includes causal treatment, that is, treatment directed toward removal of the cause of the associated disease, pathological condition, or disorder. In addition, this term includes palliative treatment, that is, treatment designed for the relief of symptoms rather than the curing of the disease, pathological condition, or disorder; preventative treatment, that is, treatment directed to minimizing or partially or completely inhibiting the development of the associated disease, pathological condition, or disorder; and supportive treatment, that is, treatment employed to supplement another specific therapy directed toward the improvement of the associated disease, pathological condition, or disorder. As used herein, the term “therapeutically effective amount” refers to an amount of the therapeutic agent that, when incorporated into and / or onto particles described herein, produces some desired effect at a reasonable benefit / risk ratio applicable to any medical treatment. The effective amount may vary depending on such factors as the disease or condition being treated, the particular targeted constructs being administered, the size of the subject, or the severity of the disease or condition. One of ordinary skill in the art may empirically determine the effective amount of a particular compound without necessitating undue experimentation. In some embodiments, the term “effective amount” refers to an amount of a therapeutic agent or prophylactic agent to reduce or diminish the symptoms of one or more diseases or disorders of the brain, such as reducing tumor size (e.g., tumor volume). Disclosed are materials, compositions, and components that can be used for, can be used in conjunction with, can be used in preparation for, or are products of the disclosed method and compositions. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds may not be explicitly disclosed, each is specifically contemplated and described herein. For example, if a ligand is disclosed and discussed and a number of modifications that can be made to a number of molecules including the ligand are discussed, each and every combination and permutation of ligand and the modifications that are possible are specifically contemplated unless specifically indicated to the contrary. Thus, if a class of molecules A, B, and C are disclosed as well45728747v115 as a class of molecules D, E, and F and an example of a combination molecule, A-D is disclosed, then even if each is not individually recited, each is individually and collectively contemplated. Thus, in this example, each of the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are specifically contemplated and should be considered disclosed from disclosure of A, B, and C; D, E, and F; and the example combination A-D. Likewise, any subset or combination of these is also specifically contemplated and disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E are specifically contemplated and should be considered disclosed from disclosure of A, B, and C; D, E, and F; and the example combination A-D. Further, each of the materials, compositions, components, etc. contemplated and disclosed as above can also be specifically and independently included or excluded from any group, subgroup, list, set, etc. of such materials. These concepts apply to all aspects of this application including, but not limited to, steps in methods of making and using the disclosed compositions. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific form or combination of forms of the disclosed methods, and that each such combination is specifically contemplated and should be considered disclosed. All methods described herein can be performed in any suitable order unless otherwise indicated or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the forms and does not pose a limitation on the scope of the forms unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Use of the term “about” is intended to describe values either above or below the stated value in a range of approx. + / - 10%; in other forms the values can range in value either above or below the stated value in a range of approx. + / - 5%; in other forms the values can range in value either above or below the stated value in a range of approx. + / - 2%; in other forms the values can range in value either above or below the stated value in a range of approx. + / - 1%. The preceding ranges are intended to be made clear by context, and no further limitation is implied.45728747v116 II. Compositions A. HERV-K Envelope protein (env) Binding Proteins Structural and biochemical studies for the HERV-K Envelope protein (env) have been hampered by a lack of good research reagents for env. To solve this problem, binding proteins that target env protein are provided. Disclosed are antibodies and their antigen binding fragments and other molecules that are capable of immunospecifically binding to human endogenous retrovirus-K (HERV-K) Env protein. As will be evident, these molecules are referred to interchangeably as Kenv-binding polypeptides, Kenv binders, anti-HERV-K Env polypeptides, HERV-K Env-binding polypeptides, HERV-K Env binders, or simply as a binder, etc. Fourteen specific mouse monoclonal antibodies, referred as Kenv-1 through Kenv-14, were created and exemplified in the Example below. Each of 14 different IgG clones were identified and named according the Binder IDs Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, and Kenv-14, respectively. Thus, when used herein, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv- 6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, and Kenv-14, refer to the monoclonal antibodies of the Examples, and the amino acid sequences they are formed therefrom. Annotated sequences for each of these binders is provided in Tables 1-10 and SEQ ID NOS:1-222 provided below. The provided sequences provide the foundation of and for the additional and alternative binders provided herein. As discussed elsewhere herein in more detail, in non-limiting embodiments, such molecules can be, for example, a monoclonal antibody, a human antibody, a chimeric antibody or a humanized antibody, or a fragment thereof, and fusion proteins formed therefrom. The antibodies and antigen binding fragments can be monospecific, bispecific, trispecific or multispecific. Any of the binding polypeptides can be linked to another compound such a drug, label, etc. Additionally provided are chimeric antigen receptors (CARs) including such antibodies and antigen binding fragments, and cells having the CARs. Also provided are uses of such molecules and cells in the diagnosis and treatment of cancer and other diseases. A. Kenv-binding Polypeptides Polypeptides that selectively bind human endogenous retrovirus-K (HERV-K) Env protein are provided. Env is synthesized as a polyprotein that follows the secretory pathway. It has a signal peptide (SP) to direct the protein to the endoplasmic reticulum, where it is cleaved by the signal peptidase. Then Env is cleaved by furin host proteases into a surface unit (SU), and a transmembrane unit (TM). SU and TM are non-covalently associated and will possibly trimerize in45728747v117 the Golgi apparatus, resulting in a trimer of heterodimers. Env anchors into the cell membrane via the TM subunit, then traffics to the plasma membrane and studs the surface of the newly budding virus particles. An exemplary consensus amino acid sequence for Env polypeptide is: MNPSEMQRKAPPRRRRHRNRAPLTHKMNKMVTSEEQMKLPSTKKAEPPTWAQLKKLTQLATKYLEN TKVTQTPESMLLAALMIVSMVVSLPMPAGAAAANYTYWAYVPFPPLIRAVTWMDNPIEVYVNDSVW VPGPIDDRCPAKPEEEGMMINISIGYRYPPICLGRAPGCLMPAVQNWLVEVPTVSPISRFTYHMVS GMSLRPRVNYLQDFSYQRSLKFRPKGKPCPKEIPKESKNTEVLVWEECVANSAVILQNNEFGTIID WAPRGQFYHNCSGQTQSCPSAQVSPAVDSDLTESLDKHKHKKLQSFYPWEWGEKGISTPRPKIISP VSGPEHPELWRLTVASHHIRIWSGNQTLETRDRKPFYTVDLNSSLTVPLQSCVKPPYMLVVGNIVI KPDSQTITCENCRLLTCIDSTFNWQHRILLVRAREGVWIPVSMDRPWEASPSIHILTEVLKGVLNR SKRFIFTLIAVIMGLIAVTATAAVAGVALHSSVQSVNFVNDWQKNSTRLWNSQSSIDQKLANQIND LRQTVIWMGDRLMSLEHRFQLQCDWNTSDFCITPQIYNESEHHWDMVRRHLQGREDNLTLDISKLK EQIFEASKAHLNLVPGTEAIAGVADGLANLNPVTWVKTIGSTTIINLILILVCLFCLLLVCRCTQQ LRRDSDHRERAMMTMAVLSKRKGGNVGKSKRDQIVTVSV (SEQ ID NO:223). The antigen used to prepare the disclosed Kenv binding proteins is AAANYTYWAYVPFPPLIRAVTWMDNPIEVYVNDSVWVPGPIDDRCPAKPEEEGMMINISIGYRYPP ICLGRAPGCLMPAVQNWLVEVPTVSPISRFTYHMVSGMSLRPRVNYLQDFSYQRSLKFRPKGKPCP KEIPKESKNTEVLVWEECVANSAVILQNNEFGTIIDWAPRGQFYHNCSGQTQSCPSAQVSPAVDSD LTESLDKHKHKKLQSFYPWEWGEKGISTPRPKIISPVSGPEHPELWRLTVASHHIRIWSGNQTLET RDRKPFYTVDLNSSLTVPLQSCVKPPYMLVVGNIVIKPDSQTITCENCRLLTCIDSTFNWQHRILL VRAREGVWIPVSMDRPWEASPSIHILTEVLKGVLNRSKRFIFTLIAVIMGLIAVTATAAVAGVALH SSVQSVNFVNDWQKNSTRLWNSQSSIDQKLANQINDLRQTVIWMGDRLMSLEHRFQLQCDWNTSDF CITPQIYNESEHHWDMVRRHLQGREDNLTLDISKLKEQIFEASKAHLNLVPGTEAIAGVADGLANL NPVTWVKTDDDDK (SEQ ID NO:224). In some embodiments, the disclosed Kenv-binding polypeptides bind to the Env protein of SEQ ID NO:223 and / or SEQ ID NO:224, or a homologue, paralogue, or ortholog thereof. In some embodiments, the Kenv-binding polypeptides bind to a variant having at least 60% up to 99% identity to SEQ ID NOS:223 and / or 224. For example in some forms, the variant sequence has at least about 60%, 70%, 75%, 80%, 85%, 90%, or 95% identity to SEQ ID NO:223 and / or 224. Therefore, in some forms, the variant consensus amino acid sequence for the Env polypeptide has an amino acid sequence that has one or more amino acids different to SEQ ID NOS:223 and / or 224, such as one or more substitutions, deletions or additions at any one of the amino acid positions of SEQ ID NOS:223 and / or 224.45728747v118 As introduced above, the term antibody herein refers to natural or synthetic polypeptides that bind a target antigen. The term includes polyclonal and monoclonal antibodies, including intact antibodies and functional (e.g., antigen-binding) antibody fragments, including Fab fragments, F(ab')2 fragments, Fab' fragments, Fv fragments, recombinant IgG (rlgG) fragments, single chain antibody fragments, including single chain variable fragments (scFv), and single domain antibodies (e.g., sdAb, sdFv, nanobody) fragments. The term encompasses genetically engineered and / or otherwise modified forms of immunoglobulins, such as intrabodies, peptibodies, chimeric antibodies, fully human antibodies, humanized antibodies, and heteroconjugate antibodies, multispecific, e.g., bispecific antibodies, diabodies, triabodies, and tetrabodies, tandem di-scFv, tandem tri-scFv. The term also encompasses intact or full-length antibodies, including antibodies of any class or subclass, including IgG and sub classes thereof, IgM, IgE, IgA, and IgD. Thus, although typically discussed in the context of IgG, the target antibody of the Ig-Fc-specific immunoglobulin variable domain can be IgM, IgE, IgA, or IgD. The disclosed binders typically include six complementarity determining regions (CDRs). The binder can include any six CDRs of the heavy and light chain variable regions of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, and Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto, in any combination. In some forms, the binder includes heavy and light chain variable regions. In some forms, the heavy chain variable region CDRs are independently selected from the heavy chain variable region CDRs of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, and Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. In some forms, the light chain variable region CDRs are independently selected from the light chain variable region CDRs of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, and Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. In some forms, the CDRs are presented in the same orientation (i.e., same N-to-C terminus orientation, e.g., CDR1, CDR2, CDR3) as in the Kenv binder from which it originated. Thus, in some forms the heavy chain variable region of the binder includes a CDR1 from the heavy chain variable region CDR1s of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; the heavy chain variable region of the binder includes a CDR2 from the heavy chain variable region CDR2s of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14, or a45728747v119 variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; the heavy chain variable region of the binder includes a CDR3 from the heavy chain variable region CDR3s of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv- 11, Kenv-12, Kenv-13, or Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; the light chain variable region of the binder includes a CDR1 from the light chain variable region CDR1s of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; the light chain variable region of the binder includes a CDR2 from the light chain variable region CDR2s of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; and the light chain variable region of the binder includes a CDR3 from the light chain variable region CDR3s of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. In some forms, the heavy chain variable region of the binder includes the three heavy chain variable region CDRs of a Kenv-1-to-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; and the light chain variable region of the binder includes the three light chain variable region CDRs of the same or different Kenv1-to-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. Thus, in some forms, the heavy chain variable region of the binder includes the three heavy chain variable region CDRs of Kenv-1, Kenv- 2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv- 13, or Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; and the light chain variable region of the binder includes the three light chain variable region CDRs of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. In some embodiments, the heavy chain variable region and light chain variable regions of antibody Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, and Kenv-14, are the heavy chain variable regions of Kenv-1, Kenv- 2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv- 13, or Kenv-14 according to Tables 4 or 5, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto, and the light chain variable regions of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or45728747v120 Kenv-14 according to Tables 9 and 10, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. In some embodiment, the CDRs have the sequence according to Table 1 and / or Table 6, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 1. Exemplary HERV-K Env-binding Polypeptide Sequences The Examples below illustrate the preparation of a series of antibodies that bind to HERV-K Env. Amino acid sequences for CDRs and variable region of the heavy and light chains are provided and can be used to prepare the antibodies of the Examples, as well as the additional and alternative binder embodiments disclosed herein. a. Heavy Chain Sequences Heavy chain CDR sequences, V-region sequences, and full V-D-J sequences are provided below in Tables 1-3, respectively. Additional information and sequence annotations for the heavy chain variable regions can be found in Tables 4 and 5 the Examples below. In addition to the sequences provided in Tables 1-5, variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto also provided. Any of these sequences alone or in any combination can be used to construct the Kenv binders provided herein. Table 1: Heavy Chain Variable Region CDR Sequences SEQ SEQ SEQ 381318 22 2732 36 4144 45728747v121 Kenv-11 GYSFTDYF 47 INPYNGDT 48 ARNGYYRYYFDY 49 1354 59 Table 2: Heavy Chain V-Region SEQ ID Binder ID V-REGION NO: 24680246 45728747v122 QVQLQQPGAELVKPGASVKLSCKASGYTFTNYYMFWVKQR PGQGLEWIGKINPSNGDTYFNEKFKSKATLTVDKSSSTAY 8 9 1 3 5 7 Table 3: Heavy Chain V-D-J Regions Binder SEQ ID 9135 45728747v123 DVQLQESGPGLVKPSQSLSLTCTVTGYSITSDYAWNWIRQFPG NKLEWMGYISYSGTTSYNPSLKSRISITRDTSKNHFFLQLNSV 7 9 1 3 5 6 8 024 b. Light Chain Sequences Light chain CDR sequences, V-region sequences, and full V-D-J sequences are provided below in Tables 6-8, respectively. Additional information and sequence annotations for the light chain variable regions can be found in Tables 9 and 10 the Examples below. In addition to the45728747v124 sequences provided in Tables 6-10, variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto also provided. Any of these sequences alone or in any combination can be used to construct the Kenv binders provided herein. Table 6: Light Chain Variable CDR Sequences SEQ SEQ SEQ Binder ID CDR2- ID ID 50504948 8 6 1561 Table 7: Light Chain V-Region SEQ 35 DIQXKXXPXCXSSXLGDRVTITCSASQGISNYLNWFQQKPDGTV KLLIYYTSSLHSGVPSRFSGSGSGTDYSLTISNLAPEDIATYYC 7 9 1 3 5 7 7 0246 45728747v126 DIVMSQSPSSLAVSAGEKVTMSCKSSQSLLNSRTRKNYLAWYQQ KPGQSPKLLIYWASTRESGVPDRFTGSGSGTDFTLTISSVQAED 8 Table 8: Light Chain V-J Regions SEQ ID 02468024 45728747v127 DVVMTQTPLSLPVSLGDQASISCRSSQSLVHSNGNTYLHWYLQ KPGQSPKVLIYKVSNRFSGVPDRFSGSGSGTDFILKIRRVGAE 4 7 9 1 3 5 2. Chimeric and Humanized Antibodies The disclosure particularly concerns chimeric and humanized antibodies. Constant regions need not be present, but if they are, are typically substantially identical to human immunoglobulin constant regions, i.e., at least about 85-90%, preferably about 95% or more identical. Hence, all parts of a humanized immunoglobulin, except possibly the CDR’s, are substantially identical to corresponding parts of natural human immunoglobulin sequences. A humanized antibody is an antibody having a humanized light chain and a humanized heavy chain immunoglobulin. For example, a humanized antibody would not encompass a typical chimeric antibody, because, e.g., the entire variable region of a chimeric antibody is non-human. One says that the donor antibody has been “humanized,” by the process of “humanization,” because the resultant humanized antibody is expected to bind to the same antigen as the donor antibody that provides the CDR’s. For the most part, humanized antibodies are human immunoglobulins (recipient antibody) in which hypervariable region residues of the recipient are replaced by hypervariable region residues from a non-human species (donor antibody) such as mouse, rat, rabbit or a non-human primate having the desired specificity, affinity, and capacity. In some instances, Framework Region (FR)45728747v128 residues of the human immunoglobulin are replaced by corresponding non-human residues. Furthermore, humanized antibodies can include residues which are not found in the recipient antibody or in the donor antibody. These modifications are made to further refine antibody performance. In general, the humanized antibody will include substantially all of at least one, and typically two, variable domains, in which all or substantially all of the hypervariable regions correspond to those of a non-human immunoglobulin and all or substantially all of the FRs are those of a human immunoglobulin sequence. The humanized antibody optionally also will include at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin that immunospecifically binds to an FcγRIIB polypeptide, that has been altered by the introduction of amino acid residue substitutions, deletions or additions (i.e., mutations). See also, e.g., European Patent Nos. EP 239,400, EP 592,106, and EP 519,596; International Publication Nos. WO 91 / 09967 and WO 93 / 17105; U.S. Patent Nos.5,225,539, 5,530,101, 5,565,332, 5,585,089, 5,766,886, and 6,407,213; and Padlan, 1991, Molecular Immunology 28(4 / 5):489-498; Studnicka et al., 1994, Protein Engineering 7(6):805-814; Roguska et al., 1994, PNAS 91:969-973; Tan et al., 2002, J. Immunol.169:1119-1125; Caldas et al., 2000, Protein Eng. 13:353-360; Morea et al., 2000, Methods 20:267-79; Baca et al., 1997, J. Biol. Chem. 272:10678-10684; Roguska et al., 1996, Protein Eng.9:895-904; Couto et al., 1995, Cancer Res. 55 (23 Supp):5973s-5977s; Couto et al., 1995, Cancer Res.55:1717-22; Sandhu, 1994, Gene 150:409-10; Pedersen et al., 1994, J. Mol. Biol.235:959-973; Jones et al., 1986, Nature 321:522- 525; Reichmann et al., 1988, Nature 332:323-329; and Presta, 1992, Curr. Op. Struct. Biol.2:593- 596). DNA sequences coding for preferred human acceptor framework sequences include but are not limited to FR segments from the human germline VH segment VH1-18 and JH6 and the human germline VL segment VK-A26 and JK4. In a specific embodiment, one or more of the CDRs are inserted within framework regions using routine recombinant DNA techniques. The framework regions can be naturally occurring or consensus framework regions, and preferably human framework regions (see, e.g., Chothia et al., 1998, “Structural Determinants In The Sequences Of Immunoglobulin Variable Domain,” J. Mol. Biol.278: 457-479 for a listing of human framework regions). A humanized or chimeric antibodies can include substantially all of at least one, and typically two, variable domains in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin (i.e., donor antibody) and all or substantially all of the framework regions are those of a human immunoglobulin consensus sequence. Preferably, the antibody also includes at least a portion of an immunoglobulin constant region (Fc), typically that45728747v129 of a human immunoglobulin. The constant domains of the antibodies can be selected with respect to the proposed function of the antibody, in particular the effector function which can be required. In some embodiments, the constant domains of the antibodies are (or include) human IgA, IgD, IgE, IgG or IgM domains. In a specific embodiment, human IgG constant domains, especially of the IgG1 and IgG3 isotypes are used, when the humanized antibodies are intended for therapeutic uses and antibody effector functions such as antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) activity are needed. In alternative embodiments, IgG2 and IgG4 isotypes are used when the antibody is intended for therapeutic purposes and antibody effector function is not required. The disclosure encompasses Fc constant domains including one or more amino acid modifications which alter antibody effector functions such as those disclosed in U.S. Patent Application Publication Nos.2005 / 0037000 and 2005 / 0064514. In some embodiments, the antibody contains both the light chain as well as at least the variable domain of a heavy chain. In other embodiments, the antibody can further include one or more of the CH1, hinge, CH2, CH3, and CH4 regions of the heavy chain. The antibody can be selected from any class of immunoglobulins, including IgM, IgG, IgD, IgA and IgE, and any isotype, including IgG1, IgG2, IgG3 and IgG4. In some embodiments, the constant domain is a complement fixing constant domain where it is desired that the antibody exhibit cytotoxic activity, and the class is typically IgG1. In other embodiments, where such cytotoxic activity is not desirable, the constant domain can be of the IgG2 class. The antibody can include sequences from more than one class or isotype, and selecting particular constant domains to optimize desired effector functions is within the ordinary skill in the art. In some embodiments, the antibody is not a mouse IgG1 or a mouse IgG2a. The framework and CDR regions of a humanized antibody need not correspond precisely to the parental sequences, e.g., the donor CDR or the consensus framework can be mutagenized by substitution, insertion or deletion of at least one residue so that the CDR or framework residue at that site does not correspond to either the consensus or the donor antibody. Such mutations, however, are preferably not extensive. Usually, at least 75% of the humanized antibody residues will correspond to those of the parental framework region (FR) and CDR sequences, more often 90%, and most preferably greater than 95%. Humanized antibodies can be produced using variety of techniques known in the art, including, but not limited to, CDR-grafting (European Patent No. EP 239,400; International Publication No. WO 91 / 09967; and U.S. Patent Nos.5,225,539, 5,530,101, and 5,585,089), veneering or resurfacing (European Patent Nos. EP 592,106 and EP 519,596; Padlan, 1991, Molecular Immunology 28(4 / 5):489-498; Studnicka et al., 1994, Protein45728747v130 Engineering 7(6):805-814; and Roguska et al., 1994, Proc. Natl. Acad. Sci.91:969-973), chain shuffling (U.S. Patent No.5,565,332), and techniques disclosed in, e.g., U.S. Patent Nos.6,407,213, 5,766,886, 5,585,089, International Publication No. WO 9317105, Tan et al., 2002, J. Immunol. 169:1119-25, Caldas et al., 2000, Protein Eng.13:353-60, Morea et al., 2000, Methods 20:267-79, Baca et al., 1997, J. Biol. Chem.272:10678-84, Roguska et al., 1996, Protein Eng.9:895-904, Couto et al., 1995, Cancer Res.55 (23 Supp):5973s-5977s, Couto et al., 1995, Cancer Res. 55:1717-22, Sandhu, 1994, Gene 150:409-10, Pedersen et al., 1994, J. Mol. Biol.235:959-73, Jones et al., 1986, Nature 321:522-525, Riechmann et al., 1988, Nature 332:323, and Presta, 1992, Curr. Op. Struct. Biol.2:593-596. Often, framework residues in the framework regions will be substituted with the corresponding residue from the CDR donor antibody to alter, preferably improve, antigen binding. These framework substitutions are identified by methods well known in the art, e.g., by modeling of the interactions of the CDR and framework residues to identify framework residues important for antigen binding and sequence comparison to identify unusual framework residues at particular positions. (See, e.g., Queen et al., U.S. Patent No.5,585,089; U.S. Publication Nos.2004 / 0049014 and 2003 / 0229208; U.S. Patent Nos.6,350,861; 6,180,370; 5,693,762; 5,693,761; 5,585,089; and 5,530,101 and Riechmann et al., 1988, Nature 332:323). 3. Bispecific and Multispecific Antibodies The antibodies used in the methods of the present disclosure can be monospecific. Antibodies monospecific for HERV-K Env can have a targeting moiety conjugated or otherwise linked thereto. In some embodiments, the targeting moiety is an antibody or antigen binding fragment thereof. Thus, in some embodiments, the anti-HERV-K Env antibody or antigen binding fragment is a bispecific, trispecific or multispecific antibody that includes a second (or third or more) antigen binding fragment that binds to a cell specific antigen. Thus provided are bispecific, trispecific or multispecific antibodies having one or more antigen binding fragments that binds to anti-HERV-K Env and a second (third or more) antigen binding fragment that binds to a cell specific antigen. For example, such antibodies can bind to both HERV-K Env and to an antigen that is important for targeting the antibody to a particular cell type or tissue (for example, to an antigen associated with a cancer antigen of a tumor being treated). In some embodiments, the antibodies are heterodimeric bi- and tri- (or more) specific Ig antibodies and Fc fusion proteins. Exemplary structures include, but are not limited to, IgG, IgM, mono-, di-, tri-, or more scFv-Fcs. For example, bispecific, trispecific, and multispecific formats include, but are not limited to, bispecific and trispecific IgG, IgG-scFv, IgG-dAb, scFv-Fc-scFv, knob-in-hole (KIH)-IgG, ĸλ-body, KIH0Fc-Fab / scFv, tandem scFv, KIH trispecific, bispecific Fc fusion (N- or C-terminal, with or without KIH).45728747v131 In embodiments, multispecific antibody molecules can include more than one antigen- binding site, where different sites are specific for different antigens. In embodiments, multispecific antibody molecules can bind more than one (e.g., two or more) epitopes on the same antigen. In embodiments, multispecific antibody molecules include an antigen-binding site specific for a target cell (e.g., cancer cell) and a different antigen-binding site specific for HERV-K Env. In some embodiments, the multispecific antibody molecule is a bispecific antibody molecule. Bispecific antibody molecules can be classified into five different structural groups: (i) bispecific immunoglobulin G (BsIgG); (ii) IgG appended with an additional antigen-binding moiety; (iii) bispecific antibody fragments; (iv) bispecific fusion proteins; and (v) bispecific antibody conjugates. BsIgG is a format that is monovalent for each antigen. Exemplary BsIgG formats include but are not limited to crossMab, DAF (two-in-one), DAF (four-in-one), DutaMab, DT-IgG, knobs- in-holes common LC, knobs-in-holes assembly, charge pair, Fab-arm exchange, SEEDbody, triomab, LUZ-Y, Fcab, kappa-lamda-body, orthogonal Fab. See Spiess et al. Mol. Immunol. 67(2015):95-106. Exemplary BsIgGs include catumaxomab (Fresenius Biotech, Trion Pharma, Neopharm), which contains an anti-CD3 arm and an anti-EpCAM arm; and ertumaxomab (Neovii Biotech, Fresenius Biotech), which targets CD3 and HER2. In some embodiments, BsIgG includes heavy chains that are engineered for heterodimerization. For example, heavy chains can be engineered for heterodimerization using a "knobs-into-holes" strategy, a SEED platform, a common heavy chain (e.g., in Kk-bodies), and use of heterodimeric Fc regions. See Spiess et al., Mol. Immunol.67(2015):95-106. Strategies that have been used to avoid heavy chain pairing of homodimers in BsIgG include knobs-in-holes, duobody, azymetric, charge pair, HA-TF, SEEDbody, and differential protein A affinity. See Id. BsIgG can be produced by separate expression of the component antibodies in different host cells and subsequent purification / assembly into a BsIgG. BsIgG can also be produced by expression of the component antibodies in a single host cell. BsIgG can be purified using affinity chromatography, e.g., using protein A and sequential pH elution. IgG appended with an additional antigen-binding moiety is another format of bispecific antibody molecules. For example, monospecific IgG can be engineered to have bispecificity by appending an additional antigen-binding unit onto the monospecific IgG, e.g., at the N- or C- terminus of either the heavy or light chain. Exemplary additional antigen-binding units include single domain antibodies (e.g., variable heavy chain or variable light chain), engineered protein scaffolds, and paired antibody variable regions (e.g., single chain variable fragments or variable fragments). See Id. Examples of appended IgG formats include dual variable domain (DVD) IgG45728747v132 (DVD-Ig), IgG(H)-scFv, scFv-(H)IgG, IgG(L)-scFv, scFv-(L)IgG, IgG(L,H)-Fv, IgG(H)-V, V(H)- IgG, IgG(L)-V, V(L)-IgG, KIH IgG-scFab, 2scFv-IgG, IgG-2scFv, scFv4-Ig, zybody, and DVI-IgG (four-in-one). See Spiess et al. Mol. Immunol.67(2015):95-106. An example of an IgG-scFv is MM-141 (Merrimack Pharmaceuticals), which binds IGF-1R and HER3. Examples of DVD-Ig include ABT-981 (AbbVie), which binds IL-1alpha and IL-1beta; and ABT-122 (AbbVie), which binds TNF and IL-17A. Bispecific antibody fragments (BsAb) are a format of bispecific antibody molecules that lack some or all of the antibody constant domains. For example, some BsAb lack an Fc region. In some embodiments, bispecific antibody fragments include heavy and light chain regions that are connected by a peptide linker that permits efficient expression of the BsAb in a single host cell. Exemplary bispecific antibody fragments include but are not limited to nanobody, nanobody-HAS, BiTE, Diabody, DART, TandAb, scDiabody, scDiabody-CH3, Diabody-CH3, triple body, miniantibody, minibody, TriBi minibody, scFv-CH3 KIH, Fab-scFv, scFv-CH-CL-scFv, F(ab')2, F(ab')2-scFv2, scFv-KIH, Fab-scFv-Fc, tetravalent HCAb, scDiabody-Fc, Diabody-Fc, tandem scFv-Fc, and intrabody. See Id. For example, the BiTE format includes tandem scFvs, where the component scFvs bind to CD3 on T cells and a surface antigen on cancer cells. Bispecific fusion proteins include antibody fragments linked to other proteins, e.g., to add additional specificity and / or functionality. An example of a bispecific fusion protein is an immTAC, which includes an anti-CD3 scFv linked to an affinity-matured T-cell receptor that recognizes HLA-presented peptides. In embodiments, the dock-and-lock (DNL) method can be used to generate bispecific antibody molecules with higher valency. Also, fusions to albumin binding proteins or human serum albumin can be extend the serum half-life of antibody fragments. See Id. In embodiments, chemical conjugation, e.g., chemical conjugation of antibodies and / or antibody fragments, can be used to create BsAb molecules. See Id. An exemplary bispecific antibody conjugate includes the CovX-body format, in which a low molecular weight drug is conjugated site-specifically to a single reactive lysine in each Fab arm or an antibody or fragment thereof. In embodiments, the conjugation improves the serum half-life of the low molecular weight drug. An exemplary CovX-body is CVX-241 (NCT01004822), which includes an antibody conjugated to two short peptides inhibiting either VEGF or Ang2. See Id. In some embodiments the multispecific molecule further includes a heavy chain constant region (e.g., an Fc region) chosen from the heavy chain constant regions of IgG1, IgG2, and IgG4, more particularly, the heavy chain constant region of human IgG1, IgG2 or IgG4. In some embodiments, the heavy chain constant region (e.g., an Fc region) is linked to, e.g., covalently45728747v133 linked to, one or both of the HERV-K Env-binding antibody molecule and the second antibody molecule. In some embodiments, the heavy chain constant region (e.g., an Fc region) is altered, e.g., mutated, to increase or decrease one or more of: Fc receptor binding, antibody glycosylation, the number of cysteine residues, effector cell function, or complement function. In some embodiments, an interface of a first and second heavy chain constant regions (e.g., Fc region) is altered, e.g., mutated, to increase or decrease dimerization, e.g., relative to a non-engineered interface. In some embodiments, the dimerization of the heavy chain constant region (e.g., Fc region) is enhanced by providing an Fc interface of a first and a second Fc region with one or more of: a paired cavity- protuberance ("knob-in-a hole"), an electrostatic interaction, or a strand-exchange, such that a greater ratio of heteromultimer:homomultimer forms, e.g., relative to a non-engineered interface. In some embodiments, the heavy chain constant region (e.g., Fc region) includes an amino acid substitution at a position chosen from one or more of 347, 349, 350, 351, 366, 368, 370, 392, 394, 395, 397, 398, 399, 405, 407, or 409, e.g., of the Fc region of human IgG1, numbered based on the Eu numbering system. Unless otherwise specified herein, numbering of amino acid residues in the Fc region or constant region is according to the EU numbering system, also called the EU index, as described in Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md., 1991. In some embodiments, the heavy chain constant region (e.g., Fc region) includes an amino acid substitution chosen from: T366S, L368A, or Y407V (e.g., corresponding to a cavity or hole), or T366W (e.g., corresponding to a protuberance or knob), or a combination thereof, numbered based on the Eu numbering system. In some embodiments, the heavy chain constant region (e.g., an Fc region) includes one or more mutations that increase or decrease one or more of: Fc receptor binding, antibody glycosylation, the number of cysteine residues, effector cell function, or complement function, relative to a naturally-existing heavy chain constant region. In some embodiments, the HERV-K Env-binding molecule includes a first heavy chain constant region (e.g., a first Fc region) and the second antibody molecule includes a second heavy chain constant region (e.g., a second Fc region), wherein the first heavy chain constant region includes one or more mutations that increase heterodimerization of the first heavy chain constant region and the second heavy chain constant region, relative to a naturally-existing heavy chain constant region, and / or wherein the second heavy chain constant region includes one or more mutations that increase heterodimerization of the second heavy chain constant region and the first heavy chain constant region, relative to a naturally-existing heavy chain constant region. In some45728747v134 embodiments, the first and the second heavy chain constant regions (e.g., first and second Fc regions) include one or more of: a paired cavity-protuberance ("knob-in-a hole"), an electrostatic interaction, or a strand-exchange, such that a greater ratio of heteromultimer:homomultimer forms, e.g., relative to naturally-existing heavy chain constant regions. In some embodiments, the first and / or second heavy chain constant region (e.g., a first and / or second Fc region, e.g., a first and / or second IgG1 Fc region) includes an amino acid substitution at a position chosen from one or more of 347, 349, 350, 351, 366, 368, 370, 392, 394, 395, 397, 398, 399, 405, 407, or 409, numbered based on the Eu numbering system. In some embodiments, the first and / or second heavy chain constant region (e.g., a first and / or second Fc region, e.g., a first and / or second IgG1 Fc region) includes an amino acid substitution chosen from: T366S, L368A, Y407V, or Y349C (e.g., corresponding to a cavity or hole), or T366W or S354C (e.g., corresponding to a protuberance or knob), or a combination thereof, numbered based on the Eu numbering system. In some embodiments, the multispecific molecule further includes a linker, e.g., a linker between one or more of: the HERV-K Env-binding molecule and the second antibody molecule, the HERV-K Env-binding antibody molecule and the heavy chain constant region (e.g., the Fc region), or the second antibody molecule and the heavy chain constant region. In some embodiments, the linker is chosen from: a cleavable linker, a non-cleavable linker, a peptide linker, a flexible linker, a rigid linker, a helical linker, or a non-helical linker. In some embodiments, the linker is a peptide linker. In some embodiments, the peptide linker includes Gly and Ser. In some embodiments, the disclosed antibodies that bind to HERV-K Env are bi- or other multispecific molecules that also bind a cancer antigen. 4. Derivatives and Conjugates The disclosure particularly contemplates the production and use of derivatives of any of the above-described antibodies and their antigen-binding fragments. The term derivative encompasses an antibody or antigen-binding fragment thereof that immunospecifically binds to an antigen but which includes, one, two, three, four, five or more amino acid substitutions, additions, deletions or modifications relative to a “parental” (or wild-type) molecule (also referred to as variants). Such amino acid substitutions or additions can introduce naturally occurring (i.e., DNA-encoded) or non- naturally occurring amino acid residues. The term derivative also encompasses, for example, chimeric or humanized variants of any of the disclosed antibodies, as well as variants having altered CH1, hinge, CH2, CH3 or CH4 regions, so as to form, for example antibodies, etc., having variant Fc regions that exhibit enhanced or impaired effector or binding characteristics.45728747v135 The term derivative additionally encompasses non-amino acid modifications, for example, amino acids that may be glycosylated (e.g., have altered mannose, 2-N-acetylglucosamine, galactose, fucose, glucose, sialic acid, 5-N-acetylneuraminic acid, 5-glycolneuraminic acid, etc. content), acetylated, pegylated, phosphorylated, amidated, derivatized by known protecting / blocking groups, proteolytic cleavage, linked to a cellular ligand or other protein, etc. In some embodiments, the altered carbohydrate modifications modulate one or more of the following: solubilization of the antibody, facilitation of subcellular transport and secretion of the antibody, promotion of antibody assembly, conformational integrity, and antibody-mediated effector function. In a specific embodiment the altered carbohydrate modifications enhance antibody mediated effector function relative to the antibody lacking the carbohydrate modification. Carbohydrate modifications that lead to altered antibody mediated effector function are well known in the art (for example, see Shields, R.L. et al. (2002) “Lack Of Fucose On Human IgG N-Linked Oligosaccharide Improves Binding To Human Fcgamma RIII And Antibody-Dependent Cellular Toxicity.,” J. Biol. Chem.277(30): 26733-26740; Davies J. et al. (2001) “Expression Of GnTIII In A Recombinant Anti-CD20 CHO Production Cell Line: Expression Of Antibodies With Altered Glycoforms Leads To An Increase In ADCC Through Higher Affinity For FC Gamma RIII,” Biotechnology & Bioengineering 74(4): 288-294). Methods of altering carbohydrate contents are known to those skilled in the art, see, e.g., Wallick, S.C. et al. (1988) “Glycosylation Of A VH Residue Of A Monoclonal Antibody Against Alpha (1----6) Dextran Increases Its Affinity For Antigen,” J. Exp. Med.168(3): 1099-1109; Tao, M.H. et al. (1989) “Studies Of Aglycosylated Chimeric Mouse-Human IgG. Role Of Carbohydrate In The Structure And Effector Functions Mediated By The Human IgG Constant Region,” J. Immunol.143(8): 2595-2601; Routledge, E.G. et al. (1995) “The Effect Of Aglycosylation On The Immunogenicity Of A Humanized Therapeutic CD3 Monoclonal Antibody,” Transplantation 60(8):847-53; Elliott, S. et al. (2003) “Enhancement Of Therapeutic Protein In Vivo Activities Through Glycoengineering,” Nature Biotechnol.21:414- 21; Shields, R.L. et al. (2002) “Lack Of Fucose On Human IgG N-Linked Oligosaccharide Improves Binding To Human Fcgamma RIII And Antibody-Dependent Cellular Toxicity.,” J. Biol. Chem.277(30): 26733-26740). In some embodiments, a humanized antibody is a derivative. Such a humanized antibody includes amino acid residue substitutions, deletions or additions in one or more non-human CDRs. The humanized antibody derivative can have substantially the same binding, better binding, or worse binding when compared to a non-derivative humanized antibody. In specific embodiments, one, two, three, four, or five amino acid residues of the CDRs have been substituted, deleted or added (i.e., mutated).45728747v136 A derivative antibody or antibody fragment can be modified by chemical modifications using techniques known to those of skill in the art, including, but not limited to, specific chemical cleavage, acetylation, formulation, metabolic synthesis of tunicamycin, etc. In one embodiment, an antibody derivative will possess a similar or identical function as the parental antibody. In another embodiment, an antibody derivative will exhibit an altered activity relative to the parental antibody. For example, a derivative antibody (or fragment thereof) can bind to its epitope more tightly or be more resistant to proteolysis than the parental antibody. Derivatized antibodies can be used to alter the half-lives (e.g., serum half-lives) of parental antibodies in a mammal, preferably a human. Preferably such alteration will result in a half-life of greater than 15 days, preferably greater than 20 days, greater than 25 days, greater than 30 days, greater than 35 days, greater than 40 days, greater than 45 days, greater than 2 months, greater than 3 months, greater than 4 months, or greater than 5 months. The increased half-lives of the humanized antibodies of the present disclosure or fragments thereof in a mammal, preferably a human, results in a higher serum titer of said antibodies or antibody fragments in the mammal, and thus, reduces the frequency of the administration of said antibodies or antibody fragments and / or reduces the concentration of said antibodies or antibody fragments to be administered. Antibodies or fragments thereof having increased in vivo half-lives can be generated by techniques known to those of skill in the art. For example, antibodies or fragments thereof with increased in vivo half- lives can be generated by modifying (e.g., substituting, deleting or adding) amino acid residues identified as involved in the interaction between the Fc domain and the FcRn receptor. The humanized antibodies can be engineered to increase biological half-lives (see, e.g. U.S. Patent No. 6,277,375). For example, humanized antibodies can be engineered in the Fc-hinge domain to have increased in vivo or serum half-lives. Antibodies or fragments thereof with increased in vivo half-lives can be generated by attaching to said antibodies or antibody fragments polymer molecules such as high molecular weight polyethyleneglycol (PEG). PEG can be attached to said antibodies or antibody fragments with or without a multifunctional linker either through site-specific conjugation of the PEG to the N– or C- terminus of said antibodies or antibody fragments or via epsilon-amino groups present on lysine residues. Linear or branched polymer derivatization that results in minimal loss of biological activity will be used. The degree of conjugation will be closely monitored by SDS-PAGE and mass spectrometry to ensure proper conjugation of PEG molecules to the antibodies. Unreacted PEG can be separated from antibody-PEG conjugates by, e.g., size exclusion or ion-exchange chromatography.45728747v137 The antibodies can also be modified by the methods and coupling agents described by Davis et al. (See U.S. Patent No.4,179,337) in order to provide compositions that can be injected into the mammalian circulatory system with substantially no immunogenic response. One embodiment encompasses modification of framework residues of the humanized HERV-K Env antibodies. Framework residues in the framework regions can be substituted with the corresponding residue from the CDR donor antibody to alter, preferably improve, antigen binding. These framework substitutions are identified by methods well known in the art, e.g., by modeling of the interactions of the CDR and framework residues to identify framework residues important for antigen binding and sequence comparison to identify unusual framework residues at particular positions. (See, e.g., U.S. Patent No.5,585,089; and Riechmann, L. et al. (1988) “Reshaping Human Antibodies For Therapy,” Nature 332:323-327). Yet another embodiment encompasses anti-HERV-K Env antibodies (and more preferably, humanized antibodies) and antigen-binding fragments thereof that are recombinantly fused or chemically conjugated (including both covalently and non-covalently conjugations) to a heterologous molecule (i.e., an unrelated molecule). The fusion does not necessarily need to be direct, but can occur through linker sequences. In one embodiment such heterologous molecules are polypeptides having at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90 or at least 100 amino acids. Such heterologous molecules can alternatively be enzymes, hormones, cell surface receptors, drug moieties, such as: toxins (such as abrin, ricin A, pseudomonas exotoxin (i.e., PE- 40), diphtheria toxin, ricin, gelonin, or pokeweed antiviral protein), proteins (such as tumor necrosis factor, interferon (e.g., α-interferon, β-interferon), nerve growth factor, platelet derived growth factor, tissue plasminogen activator, or an apoptotic agent (e.g., tumor necrosis factor-α, tumor necrosis factor-β)), biological response modifiers (such as, for example, a lymphokine (e.g., interleukin-1 (“IL-1”), interleukin-2 (“IL-2”), interleukin-6 (“IL-6”)), granulocyte macrophage colony stimulating factor (“GM-CSF”), granulocyte colony stimulating factor (“G-CSF”), or macrophage colony stimulating factor, (“M-CSF”)), or growth factors (e.g., growth hormone (“GH”))), cytotoxins (e.g., a cytostatic or cytocidal agent, such as paclitaxol, cytochalasin B, gramicidin D, ethidium bromide, emetine, mitomycin, etoposide, tenoposide, vincristine, vinblastine, colchicin, doxorubicin, daunorubicin, dihydroxy anthracin dione, mitoxantrone, mithramycin, actinomycin D, 1-dehydrotestosterone, glucocorticoids, procaine, tetracaine, lidocaine, propranolol, and puromycin and analogs or homologs thereof), antimetabolites (e.g., methotrexate, 6-mercaptopurine, 6-thioguanine, cytarabine, 5-fluorouracil decarbazine), alkylating agents (e.g., mechlorethamine, thioepa chlorambucil, melphalan, BiCNU® (carmustine; BSNU)45728747v138 and lomustine (CCNU), cyclothosphamide, busulfan, dibromomannitol, streptozotocin, mitomycin C, and cisdichlorodiamine platinum (II) (DDP) cisplatin), anthracyclines (e.g., daunorubicin (formerly daunomycin) and doxorubicin), antibiotics (e.g., dactinomycin (formerly actinomycin), bleomycin, mithramycin, and anthramycin (AMC)), or anti-mitotic agents (e.g., vincristine and vinblastine). Techniques for conjugating such therapeutic moieties to antibodies are well known; see, e.g., Arnon et al., “Monoclonal Antibodies For Immunotargeting Of Drugs In Cancer Therapy”, in MONOCLONALANTIBODIESANDCANCERTHERAPY, Reisfeld et al. (eds.), 1985, pp.243-56, Alan R. Liss, Inc.); Hellstrom et al., “Antibodies For Drug Delivery”, in CONTROLLED DRUG DELIVERY (2nd Ed.), Robinson et al. (eds.), 1987, pp.623-53, Marcel Dekker, Inc. ); Thorpe, “Antibody Carriers Of Cytotoxic Agents In Cancer Therapy: A Review”, in MONOCLONAL ANTIBODIES ‘84: BIOLOGICALANDCLINICALAPPLICATIONS, Pinchera et al. (eds.), 1985, pp.475-506); “Analysis, Results, And Future Prospective Of The Therapeutic Use Of Radiolabeled Antibody In Cancer Therapy”, in MONOCLONAL ANTIBODIES FOR CANCER DETECTION AND THERAPY, Baldwin et al. (eds.), 1985, pp.303-16, Academic Press; and Thorpe et al. (1982) “The Preparation And Cytotoxic Properties Of Antibody-Toxin Conjugates,” Immunol. Rev.62:119-158. In one embodiment, the HERV-K Env antibodies or fusion molecules include an Fc portion. The Fc portion of such molecules can be varied by isotype or subclass, can be a chimeric or hybrid, and / or can be modified, for example to improve effector functions, control of half-life, tissue accessibility, augment biophysical characteristics such as stability, and improve efficiency of production (and less costly). Many modifications useful in construction of disclosed fusion proteins and methods for making them are known in the art, see for example Mueller, J.P. et al. (1997) “Humanized Porcine VCAM-Specific Monoclonal Antibodies With Chimeric IgG2 / G4 Constant Regions Block Human Leukocyte Binding To Porcine Endothelial Cells,” Mol. Immun.34(6):441- 452, Swann, P.G. (2008) “Considerations For The Development Of Therapeutic Monoclonal Antibodies,” Curr. Opin. Immun.20:493-499 (2008), and Presta, L.G. (2008) “Molecular Engineering And Design Of Therapeutic Antibodies,” Curr. Opin. Immun.20:460-470. In some embodiments the Fc region is the native IgG1, IgG2, or IgG4 Fc region. In some embodiments the Fc region is a hybrid, for example a chimeric having IgG2 / IgG4 Fc constant regions. Modifications to the Fc region include, but are not limited to, IgG4 modified to prevent binding to Fc gamma receptors and complement, IgG1 modified to improve binding to one or more Fc gamma receptors, IgG1 modified to minimize effector function (amino acid changes), IgG1 with altered / no glycan (typically by changing expression host), and IgG1 with altered pH-dependent binding to FcRn, and IgG4 with serine at amino acid resident #228 in the hinge region changed to proline (S228P) to45728747v139 enhance stability. The Fc region can include the entire hinge region, or less than the entire hinge region. The therapeutic outcome in patients treated with rituximab (a chimeric mouse / human IgG1 monoclonal antibody against CD20) for non-Hodgkin’s lymphoma or Waldenstrom’s macroglobulinemia correlated with the individual’s expression of allelic variants of Fcγ receptors with distinct intrinsic affinities for the Fc domain of human IgG1. In particular, patients with high affinity alleles of the low affinity activating Fc receptor CD16A (FcγRIIIA) showed higher response rates and, in the cases of non-Hodgkin’s lymphoma, improved progression-free survival. In another embodiment, the Fc domain can contain one or more amino acid insertions, deletions or substitutions that reduce binding to the low affinity inhibitory Fc receptor CD32B (FcγRIIB) and retain wild-type levels of binding to or enhance binding to the low affinity activating Fc receptor CD16A (FcγRIIIA). Another embodiment includes IgG2-4 hybrids and IgG4 mutants that have reduce binding to FcR which increase their half-life. Representative IG2-4 hybrids and IgG4 mutants are described in Angal, S. et al. (1993) “A Single Amino Acid Substitution Abolishes The Heterogeneity Of Chimeric Mouse / Human (Igg4) Antibody,” Molec. Immunol.30(1):105-108; Mueller, J.P. et al. (1997) “Humanized Porcine VCAM-Specific Monoclonal Antibodies With Chimeric Igg2 / G4 Constant Regions Block Human Leukocyte Binding To Porcine Endothelial Cells,” Mol. Immun.34(6):441- 452; and U.S. Patent No.6,982,323. In some embodiments the IgG1 and / or IgG2 domain is deleted for example, Angal, s. et al. describe IgG1and IgG2having serine 241 replaced with a proline. Substitutions, additions or deletions in the derivatized antibodies can be in the Fc region of the antibody and can thereby serve to modify the binding affinity of the antibody to one or more FcγR. Methods for modifying antibodies with modified binding to one or more FcγR are known in the art, see, e.g., PCT Publication Nos. WO 04 / 029207, WO 04 / 029092, WO 04 / 028564, WO 99 / 58572, WO 99 / 51642, WO 98 / 23289, WO 89 / 07142, WO 88 / 07089, and U.S. Patent Nos. 5,843,597 and 5,642,821. In one particular embodiment, the modification of the Fc region results in an antibody with an altered antibody-mediated effector function, an altered binding to other Fc receptors (e.g., Fc activation receptors), an altered antibody-dependent cell-mediated cytotoxicity (ADCC) activity, an altered C1q binding activity, an altered complement-dependent cytotoxicity activity (CDC), a phagocytic activity, or any combination thereof. In some embodiments, the disclosure encompasses antibodies whose Fc region will have been modified so that the molecule will exhibit altered Fc receptor (FcR) binding activity, for example to exhibit decreased activity toward activating receptors such as FcγRIIA or FcγRIIIA, or increased activity toward inhibitory receptors such as FcγRIIB. Preferably, such antibodies will45728747v140 exhibit decreased antibody-dependent cell-mediated cytotoxicity (ADCC) or complement dependent cytotoxicity (CDC) activities (relative to a wild-type Fc receptor). Modifications that affect Fc-mediated effector function are well known in the art (see U.S. Patent No.6,194,551, and WO 00 / 42072; Stavenhagen, J.B. et al. (2007) “Fc Optimization Of Therapeutic Antibodies Enhances Their Ability To Kill Tumor Cells In Vitro And Controls Tumor Expansion In Vivo Via Low-Affinity Activating Fcgamma Receptors,” Cancer Res.57(18):8882- 8890; Shields, R.L. et al. (2001) “High Resolution Mapping of the Binding Site on Human IgG1 for FcγRI, FcγRII, FcγRIII, and FcRn and Design of IgG1 Variants with Improved Binding to the FcγR,” J. Biol. Chem.276(9):6591-6604). Exemplary variants of human IgG1 Fc domains with reduced binding to FcγRIIA or FcγRIIIA, but unchanged or enhanced binding to FcγRIIB, include S239A, H268A, S267G, E269A, E293A, E293D, Y296F, R301A, V303A, A327G, K322A, E333A, K334A, K338A, A339A, D376A. In some embodiments, the disclosure encompasses antibodies whose Fc region will have been deleted (for example, a Fab or F(ab)2, etc.). Any of the molecules of the present disclosure can be fused to marker sequences, such as a peptide, to facilitate purification. In preferred embodiments, the marker amino acid sequence is a hexa-histidine peptide, the hemagglutinin “HA” tag, which corresponds to an epitope derived from the influenza hemagglutinin protein (Wilson, I.A. et al. (1984) “The Structure Of An Antigenic Determinant In A Protein,” Cell, 37:767-778) and the “flag” tag (Knappik, A. et al. (1994) “An Improved Affinity Tag Based On The FLAG Peptide For The Detection And Purification Of Recombinant Antibody Fragments,” Biotechniques 17(4):754-761). The present disclosure also encompasses antibodies or their antigen-binding fragments that are conjugated to a diagnostic or therapeutic agent or any other molecule for which serum half-life is desired to be increased. The antibodies can be used diagnostically (in vivo, in situ or in vitro) to, for example, monitor the development or progression of a disease, disorder or infection as part of a clinical testing procedure to, e.g., determine the efficacy of a given treatment regimen. Detection can be facilitated by coupling the antibody to a detectable substance. Examples of detectable substances include various enzymes, prosthetic groups, fluorescent materials, luminescent materials, bioluminescent materials, radioactive materials, positron emitting metals, and nonradioactive paramagnetic metal ions. The detectable substance can be coupled or conjugated either directly to the antibody or indirectly, through an intermediate (such as, for example, a linker known in the art) using techniques known in the art. See, for example, U.S. Patent No.4,741,900 for metal ions which can be conjugated to antibodies for use as diagnostics according to the present disclosure. Such diagnosis and detection can be accomplished by coupling the antibody to45728747v141 detectable substances including, but not limited to, various enzymes, enzymes including, but not limited to, horseradish peroxidase, alkaline phosphatase, beta-galactosidase, or acetylcholinesterase; prosthetic group complexes such as, but not limited to, streptavidin / biotin and avidin / biotin; fluorescent materials such as, but not limited to, umbelliferone, fluorescein, fluorescein isothiocyanate, rhodamine, dichlorotriazinylamine fluorescein, dansyl chloride or phycoerythrin; luminescent material such as, but not limited to, luminol; bioluminescent materials such as, but not limited to, luciferase, luciferin, and aequorin; radioactive material such as, but not limited to, bismuth (213Bi), carbon (14C), chromium (51Cr), cobalt (57Co), fluorine (18F), gadolinium (153Gd,159Gd), gallium (68Ga,67Ga), germanium (68Ge), holmium (166Ho), indium (115In,113In,112In,111In), iodine (131I,125I,123I,121I), lanthanium (140La), lutetium (177Lu), manganese (54Mn), molybdenum (99Mo), palladium (103Pd), phosphorous (32P), praseodymium (142Pr), promethium (149Pm), rhenium (186Re,188Re), rhodium (105Rh), ruthemium (97Ru), samarium (153Sm), scandium (47Sc), selenium (75Se), strontium (85Sr), sulfur (35S), technetium (99Tc), thallium (201Ti), tin (113Sn,117Sn), tritium (3H), xenon (133Xe), ytterbium (169Yb,175Yb), yttrium (90Y), zinc (65Zn); positron emitting metals using various positron emission tomographies, and nonradioactive paramagnetic metal ions. The molecules of the present disclosure can be conjugated to a second antibody to form an antibody heteroconjugate as described by Segal in U.S. Patent No.4,676,980. Such heteroconjugate antibodies may additionally bind to haptens (such as fluorescein, etc.), or to cellular markers, or to cytokines, or chemokines (e.g., CCL21), etc. The molecules of the present disclosed can be attached to solid supports, which are particularly useful for immunoassays or purification of the target antigen or of other molecules that are capable of binding to target antigen that has been immobilized to the support via binding to an antibody or antigen-binding fragment of the present disclosure. Such solid supports include, but are not limited to, glass, cellulose, polyacrylamide, nylon, polystyrene, polyvinyl chloride or polypropylene. 5. Methods of Making Antibodies and Antigen Binding Fragments The disclosed antibodies can be produced by any method known in the art useful for the production of polypeptides, e.g., in vitro synthesis, recombinant DNA production, and the like. Preferably, the antibodies are produced by recombinant DNA technology. The antibodies can be produced using recombinant immunoglobulin expression technology. The recombinant production of immunoglobulin molecules, including humanized antibodies are described in U.S. Patent No. 4,816,397 (Boss et al.), U.S. Patent Nos.6,331,415 and 4,816,567 (both to Cabilly et al.), U.K. patent GB 2,188,638 (Winter et al.), and U.K. patent GB 2,209,757. Techniques for the45728747v142 recombinant expression of immunoglobulins, including humanized immunoglobulins, can also be found, in Goeddel et al., Gene Expression Technology Methods in Enzymology Vol.185 Academic Press (1991), and Borreback, Antibody Engineering, W. H. Freeman (1992). Additional information concerning the generation, design and expression of recombinant antibodies can be found in Mayforth, Designing Antibodies, Academic Press, San Diego (1993). An exemplary process for the production of the recombinant chimeric antibodies can include the following: a) constructing, by conventional molecular biology methods, an expression vector that encodes and expresses an antibody heavy chain in which the CDRs and variable region of a murine anti-HERV-K Env monoclonal antibody are fused to an Fc region derived from a human immunoglobulin, thereby producing a vector for the expression of a chimeric antibody heavy chain; b) constructing, by conventional molecular biology methods, an expression vector that encodes and expresses an antibody light chain of the murine anti-HERV-K Env monoclonal antibody, thereby producing a vector for the expression of chimeric antibody light chain; c) transferring the expression vectors to a host cell by conventional molecular biology methods to produce a transfected host cell for the expression of chimeric antibodies; and d) culturing the transfected cell by conventional cell culture techniques so as to produce chimeric antibodies. An exemplary process for the production of the recombinant humanized antibodies can include the following: a) constructing, by conventional molecular biology methods, an expression vector that encodes and expresses an anti-HERV-K Env heavy chain in which the CDRs and a minimal portion of the variable region framework that are required to retain donor antibody binding specificity are derived from a non-human immunoglobulin, such as a murine anti-HERV-K Env monoclonal antibody, and the remainder of the antibody is derived from a human immunoglobulin, thereby producing a vector for the expression of a humanized antibody heavy chain; b) constructing, by conventional molecular biology methods, an expression vector that encodes and expresses an antibody light chain in which the CDRs and a minimal portion of the variable region framework that are required to retain donor antibody binding specificity are derived from a non- human immunoglobulin, such as a murine anti-HERV-K Env monoclonal antibody, and the remainder of the antibody is derived from a human immunoglobulin, thereby producing a vector for the expression of humanized antibody light chain; c) transferring the expression vectors to a host cell by conventional molecular biology methods to produce a transfected host cell for the expression of humanized antibodies; and d) culturing the transfected cell by conventional cell culture techniques so as to produce humanized antibodies. With respect to either exemplary method, host cells can be co-transfected with such expression vectors, which can contain different selectable markers but, with the exception of the45728747v143 heavy and light chain coding sequences, are preferably identical. This procedure provides for equal expression of heavy and light chain polypeptides. Alternatively, a single vector can be used which encodes both heavy and light chain polypeptides. The coding sequences for the heavy and light chains can include cDNA or genomic DNA or both. The host cell used to express the recombinant antibody can be either a bacterial cell such as Escherichia coli, or more preferably a eukaryotic cell (e.g., a Chinese hamster ovary (CHO) cell or a HEK-293 cell). The choice of expression vector is dependent upon the choice of host cell, and can be selected so as to have the desired expression and regulatory characteristics in the selected host cell. Other cell lines that can be used include, but are not limited to, CHO-K1, NSO, and PER.C6 (Crucell, Leiden, Netherlands). Any of the above-described antibodies can be used to generate anti-idiotype antibodies using techniques well known to those skilled in the art (see, e.g., Greenspan, N.S. et al. (1989) “Idiotypes: Structure And Immunogenicity,” FASEB J.7:437-444; and Nisinoff, A. (1991) “Idiotypes: Concepts And Applications,” J. Immunol.147(8):2429-2438). The binding properties of any of the above antibodies can, if desired, be further improved by screening for variants that exhibit such desired characteristics. For example, such antibodies can be generated using various phage display methods known in the art. In phage display methods, functional antibody domains are displayed on the surface of phage particles which carry the polynucleotide sequences encoding them. In a particular embodiment, such phage can be utilized to display antigen binding domains, such as Fab and Fv or disulfide-bond stabilized Fv, expressed from a repertoire or combinatorial antibody library (e.g., human or murine). Phage expressing an antigen binding domain that binds the antigen of interest can be selected or identified with antigen, e.g., using labeled antigen or antigen bound or captured to a solid surface or bead. Phage used in these methods are typically filamentous phage, including fd and M13. The antigen binding domains are expressed as a recombinantly fused protein to either the phage gene III or gene VIII protein. Examples of phage display methods that can be used to make the immunoglobulins, or fragments thereof, of the present disclosure include those disclosed in Brinkman, U. et al. (1995) “Phage Display Of Disulfide-Stabilized Fv Fragments,” J. Immunol. Methods, 182:41-50, 1995; Ames, R.S. et al. (1995) “Conversion Of Murine Fabs Isolated From A Combinatorial Phage Display Library To Full Length Immunoglobulins,” J. Immunol. Methods, 184:177-186; Kettleborough, C.A. et al. (1994) “Isolation Of Tumor Cell-Specific Single-Chain Fv From Immunized Mice Using Phage-Antibody Libraries And The Re-Construction Of Whole Antibodies From These Antibody Fragments,” Eur. J. Immunol., 24:952-958, 1994; Persic, L. et al. (1997) “An Integrated Vector System For The Eukaryotic Expression Of Antibodies Or Their Fragments After Selection From Phage Display Libraries,” Gene, 187:9-18; Burton, D.R. et al. (1994) “Human45728747v144 Antibodies From Combinatorial Libraries,” Adv. Immunol.57:191-280; PCT Publications WO 92 / 001047; WO 90 / 02809; WO 91 / 10737; WO 92 / 01047; WO 92 / 18619; WO 93 / 11236; WO 95 / 15982; WO 95 / 20401; and U.S. Patents Nos.5,698,426; 5,223,409; 5,403,484; 5,580,717; 5,427,908; 5,750,753; 5,821,047; 5,571,698; 5,427,908; 5,516,637; 5,780,225; 5,658,727; 5,733,743 and 5,969,108. As described in the above references, after phage selection, the antibody coding regions from the phage can be isolated and used to generate whole antibodies, including humanized antibodies, or any other desired fragments, and expressed in any desired host, including mammalian cells, insect cells, plant cells, yeast, and bacteria, e.g., as described in detail below. For example, techniques to recombinantly produce Fab, Fab’ and F(ab’)2 fragments can also be employed using methods known in the art (such as those disclosed in PCT Publication WO 92 / 22324; Mullinax, R.L. et al. (1992) “Expression Of A Heterodimeric Fab Antibody Protein In One Cloning Step,” BioTechniques, 12(6):864-869; and Sawai et al. (1995) “Direct Production Of The Fab Fragment Derived From The Sperm Immobilizing Antibody Using Polymerase Chain Reaction And cDNA Expression Vectors,” Am. J. Reprod. Immunol.34:26-34; and Better, M. et al. (1988) “Escherichia coli Secretion Of An Active Chimeric Antibody Fragment,” Science 240:1041-1043). Examples of techniques which can be used to produce single-chain Fvs and antibodies include those described in U.S. Patent Nos.4,946,778 and 5,258,498; Huston, J.S. et al. (1991) “Protein Engineering Of Single-Chain Fv Analogs And Fusion Proteins,” Methods in Enzymology 203:46-88; Shu, L. et al., “Secretion Of A Single-Gene-Encoded Immunoglobulin From Myeloma Cells,” Proc. Natl. Acad. Sci. (USA) 90:7995-7999; and Skerra. A. et al. (1988) “Assembly Of A Functional Immunoglobulin Fv Fragment In Escherichia coli,” Science 240:1038-1040. Phage display technology can be used to increase the affinity of an antibody for HERV-K Env. This technique would be useful in obtaining high affinity antibodies that could be used in the disclosed methods. This technology, referred to as affinity maturation, employs mutagenesis or CDR walking and re-selection using such receptors or ligands (or their extracellular domains) or an antigenic fragment thereof to identify antibodies that bind with higher affinity to the antigen when compared with the initial or parental antibody (See, e.g., Glaser, S.M. et al. (1992) “Antibody Engineering By Codon-Based Mutagenesis In A Filamentous Phage Vector System,” J. Immunol. 149:3903-3913). Mutagenizing entire codons rather than single nucleotides results in a semi- randomized repertoire of amino acid mutations. Libraries can be constructed including of a pool of variant clones each of which differs by a single amino acid alteration in a single CDR and which contain variants representing each possible amino acid substitution for each CDR residue. Mutants with increased binding affinity for the antigen can be screened by contacting the immobilized45728747v145 mutants with labeled antigen. Any screening method known in the art can be used to identify mutant antibodies with increased avidity to the antigen (e.g., ELISA) (see, e.g., Wu, H. et al. (1998) “Stepwise In Vitro Affinity Maturation Of Vitaxin, An Alphav Beta3-Specific Humanized Mab,” Proc. Natl. Acad. Sci. (USA) 95(11):6037-6042; Yelton, D.E. et al. (1995) “Affinity Maturation Of The BR96 Anti-Carcinoma Antibody By Codon-Based Mutagenesis,” J. Immunol.155:1994-2004). CDR walking which randomizes the light chain can be used (see, Schier et al. (1996) “Isolation Of Picomolar Affinity Anti-C-Erbb-2 Single-Chain Fv By Molecular Evolution Of The Complementarity Determining Regions In The Center Of The Antibody Binding Site,” J. Mol. Biol. 263:551-567). The disclosure thus contemplates the use of random mutagenesis to identify improved CDRs. Phage display technology can alternatively be used to increase (or decrease) CDR affinity. This technology, referred to as affinity maturation, employs mutagenesis or “CDR walking” and re- selection uses the target antigen or an antigenic fragment thereof to identify antibodies having CDRs that bind with higher (or lower) affinity to the antigen when compared with the initial or parental antibody (see, e.g., Glaser, S.M. et al. (1992) “Antibody Engineering By Codon-Based Mutagenesis In A Filamentous Phage Vector System,” J. Immunol.149:3903-3913). Mutagenizing entire codons rather than single nucleotides results in a semi-randomized repertoire of amino acid mutations. Libraries can be constructed including of a pool of variant clones each of which differs by a single amino acid alteration in a single CDR and which contain variants representing each possible amino acid substitution for each CDR residue. Mutants with increased (or decreased) binding affinity for the antigen can be screened by contacting the immobilized mutants with labeled antigen. Any screening method known in the art can be used to identify mutant antibodies with increased (or decreased) avidity to the antigen (e.g., ELISA) (see, Wu, H. et al. (1998) “Stepwise In Vitro Affinity Maturation Of Vitaxin, An Alphav Beta3-Specific Humanized Mab,” Proc. Natl. Acad. Sci. (USA) 95(11):6037-6042; Yelton, D.E. et al. (1995) “Affinity Maturation Of The BR96 Anti- Carcinoma Antibody By Codon-Based Mutagenesis,” J. Immunol.155:1994-2004). CDR walking which randomizes the light chain can be used (see, Schier et al. (1996) “Isolation Of Picomolar Affinity Anti-C-Erbb-2 Single-Chain Fv By Molecular Evolution Of The Complementarity Determining Regions In The Center Of The Antibody Binding Site,” J. Mol. Biol.263:551-567). Methods for accomplishing such affinity maturation are described for example in: Krause, J.C. et al. (2011) “An Insertion Mutation That Distorts Antibody Binding Site Architecture Enhances Function Of A Human Antibody,” MBio.2(1) pii: e00345-10. doi: 10.1128 / mBio.00345- 10; Kuan, C.T. et al. (2010) “Affinity-Matured Anti-Glycoprotein NMB Recombinant Immunotoxins Targeting Malignant Gliomas And Melanomas,” Int. J. Cancer 10.1002 / ijc.25645; Hackel, B.J. et45728747v146 al. (2010) “Stability And CDR Composition Biases Enrich Binder Functionality Landscapes,” J. Mol. Biol.401(1):84-96; Montgomery, D.L. et al. (2009) “Affinity Maturation And Characterization Of A Human Monoclonal Antibody Against HIV-1 gp41,” MAbs 1(5):462-474; Gustchina, E. et al. (2009) “Affinity Maturation By Targeted Diversification Of The CDR-H2 Loop Of A Monoclonal Fab Derived From A Synthetic Naïve Human Antibody Library And Directed Against The Internal Trimeric Coiled-Coil Of Gp41 Yields A Set Of Fabs With Improved HIV-1 Neutralization Potency And Breadth,” Virology 393(1):112-119; Finlay, W.J. et al. (2009) “Affinity Maturation Of A Humanized Rat Antibody For Anti-RAGE Therapy: Comprehensive Mutagenesis Reveals A High Level Of Mutational Plasticity Both Inside And Outside The Complementarity- Determining Regions,” J. Mol. Biol.388(3):541-558; Bostrom, J. et al. (2009) “Improving Antibody Binding Affinity And Specificity For Therapeutic Development,” Methods Mol. Biol.525:353-376; Steidl, S. et al. (2008) “In Vitro Affinity Maturation Of Human GM-CSF Antibodies By Targeted CDR-Diversification,” Mol. Immunol.46(1):135-144; and Barderas, R. et al. (2008) “Affinity maturation of antibodies assisted by in silico modeling,” Proc. Natl. Acad. Sci. (USA) 105(26):9029-9034. B. Anti-HERV-K Chimeric Antigen Receptors (CAR) Chimeric Antigen Receptor (CAR) proteins including the disclosed Kenv-binding proteins as an antigen binding domain, and cells expressing the same are also provided. Typically, CARs also include a transmembrane domain and one or more intracellular / cytoplasmic domains. CARs are engineered receptors that possess both antigen-binding and T-cell-activating functions. Immunotherapy using T cells genetically engineered to express a CAR is rapidly emerging as a promising new treatment for hematological and non- hematological malignancies. Based on the location of the CAR in the membrane of the cell, the CAR can be divided into three main distinct domains, including an extracellular antigen-binding domain, followed by a space region, a transmembrane domain, and the intracellular signaling domain. The antigen-binding domain, most commonly derived from variable regions of immunoglobulins, typically contains VH and VL chains that are joined up by a linker to form the so-called “scFv.” The segment interposing between the antigen-binding domain (e.g., scFv) and the transmembrane domain is a “spacer domain.” The spacer domain can include the constant IgG1 hinge-CH2–CH3 Fc domain. In some cases, the spacer domain and the transmembrane domain are derived from CD8. The intracellular signaling domains mediating T cell activation can include a CD3ζ co-receptor signaling domain derived from C-region of the TCR α and β chains and one or more costimulatory domains. In the disclosed CARs, the antigen binding domain is typically a disclosed anti-HERV-K Env binding protein. In some forms, the antigen-binding domain is derived from an antibody, e.g.,45728747v147 a disclosed Kenv antibody. As introduced above, the term antibody herein refers to natural or synthetic polypeptides that bind a target antigen, and such antibodies can form part or all of the antigen binding domain of the CAR. The term includes polyclonal and monoclonal antibodies, including intact antibodies and functional (e.g., antigen-binding) antibody fragments, including Fab fragments, F(ab')2fragments, Fab' fragments, Fv fragments, recombinant IgG (rlgG) fragments, single chain antibody fragments, including single chain variable fragments (scFv), and single domain antibodies (e.g., sdAb, sdFv, nanobody) fragments. The term encompasses genetically engineered and / or otherwise modified forms of immunoglobulins, such as intrabodies, peptibodies, chimeric antibodies, fully human antibodies, humanized antibodies, and heteroconjugate antibodies, multispecific, e.g., bispecific, antibodies, diabodies, triabodies, and tetrabodies, tandem di-scFv, tandem tri-scFv. The term also encompasses intact or full-length antibodies, including antibodies of any class or subclass, including IgG and sub-classes thereof, IgM, IgE, IgA, and IgD. The antigen-binding domain of a CAR can contain complementary determining regions (CDR) of an antibody, variable regions of an antibody, and / or antigen binding fragments thereof. For example, the antigen-binding domain for an HERV-K Env CAR can be derived from a disclosed Kenv antibody as described above. In some forms, the antigen-binding domain can include an F(ab')2, Fab', Fab, Fv or scFv. In some forms, the CAR includes one or more spacer domain(s) (also referred to as hinge domain) that is located between the extracellular antigen-binding domain and the transmembrane domain. A spacer domain is an amino acid segment that is generally found between two domains of a protein and may allow for flexibility of the protein and movement of one or both of the domains relative to one another. Any amino acid sequence that provides such flexibility and movement of the extracellular antigen-binding domain relative to the transmembrane domain can be used. The spacer domain can be a spacer or hinge domain of a naturally occurring protein. In some forms, the hinge domain is derived from CD8a, such as, a portion of the hinge domain of CD8a, e.g., a fragment containing at least 5 (e.g., 5, 10, 15, 20, 25, 30, 35, or 40) consecutive amino acids of the hinge domain of CD8a. Hinge domains of antibodies, such as an IgG, IgA, IgM, IgE, or IgD antibodies can also be used. In some forms, the hinge domain is the hinge domain that joins the constant CH1 and CH2 domains of an antibody. Non-naturally occurring peptides may also be used as spacer domains. For example, the spacer domain can be a peptide linker, such as a (GxS)n linker, wherein x and n, independently can be an integer of 3 or more, including 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or more. In some forms, the CAR includes a transmembrane domain that can be directly or indirectly fused to the antigen-binding domain. The transmembrane domain may be derived either from a45728747v148 natural or a synthetic source. In some forms, the transmembrane domain of the CAR includes a transmembrane domain of an alpha, beta or zeta chain of a T-cell receptor, CD8, CD4, CD28, CD137, CD80, CD86, CD152 (CTLA-4) or PD1, or a portion thereof. Transmembrane domains can also contain at least a portion of a synthetic, non-naturally occurring protein segment. In some forms, the transmembrane domain is a synthetic, non-naturally occurring alpha helix or beta sheet. In some forms, the protein segment is at least about 15 amino acids, e.g., at least 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or more amino acids. Examples of synthetic transmembrane domains are known in the art, for example in U.S. Patent No.7,052,906 and PCT Publication No. WO 2000 / 032776. The intracellular signaling domain is responsible for activation of at least one of the normal effector functions of the immune effector cell expressing the CAR. The term effector function refers to a specialized function of a cell. Effector function of a T cell, for example, may be cytolytic activity or helper activity including the secretion of cytokines. In some forms, an intracellular signaling domain includes the zeta chain of the T cell receptor or any of its homologs (e.g., eta, delta, gamma or epsilon), MBl chain, B29, Fc RIII, Fc RI and combinations of signaling molecules such as CD3ζ and CD28, 4-1BB, OX40 and combination thereof, as well as other similar molecules and fragments. Intracellular signaling portions of other members of the families of activating proteins can be used, such as FcγRIII and FcεRI. Many immune effector cells require co-stimulation, in addition to stimulation of an antigen- specific signal, to promote cell proliferation, differentiation and survival, as well as to activate effector functions of the cell. Therefore, in some forms, the CAR includes at least one co-stimulatory signaling domain. The term co-stimulatory signaling domain, refers to at least a portion of a protein that mediates signal transduction within a cell to induce an immune response such as an effector function. The co-stimulatory signaling domain can be a cytoplasmic signaling domain from a co-stimulatory protein, which transduces a signal and modulates responses mediated by immune cells, such as T cells, NK cells, macrophages, neutrophils, or eosinophils. In some forms, the co-stimulatory signaling domain is derived from a co-stimulatory molecule selected from CD27, CD28, CD137, 0X40, CD30, CD40, CD3, LFA-1, ICOS, CD2, CD7, LIGHT, NKG2C, B7-H3, ligands of CD83 and combinations thereof. CARs can be used in order to generate immuno-responsive cells, such as T cells, specific for selected targets, such as malignant cells, with a wide variety of receptor chimera constructs having been described (see U.S. Patent Nos.5,843,728; 5,851,828; 5,912,170; 6,004,811; 6,284,240; 6,392,013; 6,410,014; 6,753,162; 8,211,422; and PCT Publication WO 9215322, each of which is specifically incorporated by reference herein in its entirety). Alternative CAR constructs can be45728747v149 characterized as belonging to successive generations. First-generation CARs typically include a single-chain variable fragment of an antibody specific for an antigen, for example including a VL linked to a VH of a specific antibody, linked by a flexible linker, for example by a CD8α hinge domain and a CD8α transmembrane domain, to the transmembrane and intracellular signaling domains of either CD3ζ or FcRγ (scFv-CD3ζ or scFv- FcRγ; see U.S. Patent No.7,741,465; U.S. Patent No.5,912,172; U.S. Patent No.5,906,936, each of which is specifically incorporated by reference herein in its entirety). Second-generation CARs incorporate the intracellular domains of one or more costimulatory molecules, such as CD28, OX40 (CD134), or 4-1BB (CD137) within the endodomain (for example scFv-CD28 / OX40 / 4-1BB-CD3ζ; see U.S. Patent Nos.8,911,993; 8,916,381; 8,975,071; 9,101,584; 9,102,760; 9,102,761, each of which is specifically incorporated by reference herein in its entirety). Third-generation CARs include a combination of costimulatory endodomains, such a CD3ζ-chain, CD97, GDI la-CD18, CD2, ICOS, CD27, CD154, CDS, OX40, 4-1BB, or CD28 signaling domains (for example scFv-CD28-4-1BB-CD3ζ or scFv-CD28-OX40- CD3ζ; see U.S. Patent No.8,906,682; U.S. Patent No.8,399,645; U.S. Pat. No.5,686,281; PCT Publication No. WO2014134165; PCT Publication No. WO2012079000, each of which is specifically incorporated by reference herein in its entirety). Alternatively, co-stimulation can be orchestrated by expressing CARs in antigen-specific T cells, chosen so as to be activated and expanded following engagement of their native αβTCR, for example by antigen on professional antigen-presenting cells, with attendant co-stimulation. Any of the first, second, or third generation CARs described above can be used in accordance with the disclosed compositions and methods. In some forms, the CAR cells targets and / or is used for the treatment of cancer, or other disease or disorder disclosed herein. C. Nucleic Acids Isolated nucleic acids and vectors encoding or expressing Kenv binding molecules and Kenv-CAR fusion proteins are also provided. As used herein, “isolated nucleic acid” refers to a nucleic acid that is separated from other nucleic acid molecules that are present in a mammalian genome, including nucleic acids that normally flank one or both sides of the nucleic acid in a mammalian genome. An isolated nucleic acid can be, for example, a DNA molecule, provided one of the nucleic acid sequences normally found immediately flanking that DNA molecule in a naturally-occurring genome is removed or absent. Thus, an isolated nucleic acid includes, without limitation, a DNA molecule that exists as a separate molecule independent of other sequences (e.g., a chemically synthesized nucleic acid, or a cDNA or genomic DNA fragment produced by PCR or restriction endonuclease treatment), as well as recombinant DNA that is incorporated into a vector, an45728747v150 autonomously replicating plasmid, a virus (e.g., a retrovirus, lentivirus, adenovirus, or herpes virus), or into the genomic DNA of a prokaryote or eukaryote. In addition, an isolated nucleic acid can include an engineered nucleic acid such as a recombinant DNA molecule that is part of a hybrid or fusion nucleic acid. A nucleic acid existing among hundreds to millions of other nucleic acids within, for example, a cDNA library or a genomic library, or a gel slice containing a genomic DNA restriction digest, is not to be considered an isolated nucleic acid. Nucleic acid encoding the disclosed polypeptide sequences are expressly provided. Nucleic acids can be single strand or double stranded, and can be in sense or antisense orientation, or can be complementary to a reference sequence. Nucleic acids can be DNA, RNA, or nucleic acid analogs. Nucleic acid analogs can be modified at the base moiety, sugar moiety, or phosphate backbone. Such modification can improve, for example, stability, hybridization, or solubility of the nucleic acid. Modifications at the base moiety can include deoxyuridine for deoxythymidine, and 5-methyl-2’-deoxycytidine or 5-bromo- 2’-deoxycytidine for deoxycytidine. Modifications of the sugar moiety can include modification of the 2’ hydroxyl of the ribose sugar to form 2’-O-methyl or 2’-O-allyl sugars. The deoxyribose phosphate backbone can be modified to produce morpholino nucleic acids, in which each base moiety is linked to a six membered, morpholino ring, or peptide nucleic acids, in which the deoxyphosphate backbone is replaced by a pseudopeptide backbone and the four bases are retained. See, for example, Summerton and Weller (1997) Antisense Nucleic Acid Drug Dev.7:187-195; and Hyrup et al. (1996) Bioorgan. Med. Chem.4:5-23. In addition, the deoxyphosphate backbone can be replaced with, for example, a phosphorothioate or phosphorodithioate backbone, a phosphoroamidite, or an alkyl phosphotriester backbone. Nucleic acids, such as those described above, can be inserted into vectors for expression in cells. As used herein, a “vector” is a replicon, such as a plasmid, phage, or cosmid, into which another DNA segment may be inserted so as to bring about the replication of the inserted segment. Vectors can be expression vectors. An “expression vector” is a vector that includes one or more expression control sequences, and an “expression control sequence” is a DNA sequence that controls and regulates the transcription and / or translation of another DNA sequence. Nucleic acids in vectors can be operably linked to one or more expression control sequences. As used herein, “operably linked” means incorporated into a genetic construct so that expression control sequences effectively control expression of a coding sequence of interest. Examples of expression control sequences include promoters, enhancers, and transcription terminating regions. A promoter is an expression control sequence composed of a region of a DNA molecule, typically within 100 nucleotides upstream of the point at which transcription starts45728747v151 (generally near the initiation site for RNA polymerase II). To bring a coding sequence under the control of a promoter, it is necessary to position the translation initiation site of the translational reading frame of the polypeptide between one and about fifty nucleotides downstream of the promoter. Enhancers provide expression specificity in terms of time, location, and level. Unlike promoters, enhancers can function when located at various distances from the transcription site. An enhancer also can be located downstream from the transcription initiation site. A coding sequence is “operably linked” and “under the control” of expression control sequences in a cell when RNA polymerase is able to transcribe the coding sequence into mRNA, which then can be translated into the protein encoded by the coding sequence. Suitable expression vectors include, without limitation, plasmids and viral vectors derived from, for example, bacteriophage, baculoviruses, tobacco mosaic virus, herpes viruses, cytomegalo virus, retroviruses, vaccinia viruses, adenoviruses, and adeno-associated viruses. Numerous vectors and expression systems are commercially available from such corporations as Novagen (Madison, WI), Clontech (Palo Alto, CA), Stratagene (La Jolla, CA), and Invitrogen Life Technologies (Carlsbad, CA). An expression vector can include a tag sequence. Tag sequences, are typically expressed as a fusion with the encoded polypeptide. Such tags can be inserted anywhere within the polypeptide including at either the carboxyl or amino terminus. Examples of useful tags include, but are not limited to, green fluorescent protein (GFP), glutathione S-transferase (GST), polyhistidine, c-myc, hemagglutinin, Flag™ tag (Kodak, New Haven, CT), maltose E binding protein and protein A. In one embodiment, the variant PD-L2 fusion protein is present in a vector containing nucleic acids that encode one or more domains of an Ig heavy chain constant region, preferably having an amino acid sequence corresponding to the hinge, CH2and CH3regions of a human immunoglobulin Cγ1 chain. Vectors containing nucleic acids to be expressed can be transferred into host cells. The term “host cell” is intended to include prokaryotic and eukaryotic cells into which a recombinant expression vector can be introduced. As used herein, “transformed” and “transfected” encompass the introduction of a nucleic acid molecule (e.g., a vector) into a cell by one of a number of techniques. Although not limited to a particular technique, a number of these techniques are well established within the art. Prokaryotic cells can be transformed with nucleic acids by, for example, electroporation or calcium chloride mediated transformation. Nucleic acids can be transfected into mammalian cells by techniques including, for example, calcium phosphate co-precipitation, DEAE- dextran-mediated transfection, lipofection, electroporation, or microinjection. Host cells (e.g., a45728747v152 prokaryotic cell or a eukaryotic cell such as a CHO cell) can be used to, for example, produce the PD-1 antagonist polypeptides described herein. D. Host Cells In some embodiments, polypeptides, nucleic acids, or vectors provided herein are present within a host cells. The term “host cell” is intended to include prokaryotic and eukaryotic cells into which a nucleic acid such as a recombinant expression vector can be introduced. As used herein, “transformed” and “transfected” encompass the introduction of a nucleic acid molecule (e.g., an mRNA, or a vector, etc.) into a cell by one of a number of techniques. Although not limited to a particular technique, a number of these techniques are well established within the art. Prokaryotic cells can be transformed with nucleic acids by, for example, electroporation or calcium chloride mediated transformation. Nucleic acids can be transfected into mammalian cells by techniques including, for example, calcium phosphate co-precipitation, DEAE-dextran-mediated transfection, lipofection, electroporation, or microinjection. Host cells (e.g., a prokaryotic cell or a eukaryotic cell) can be used to produce polypeptides described herein. In some forms, the cell is from an established cell line, or a primary cell. The term “primary cell,” refers to cells and cell cultures derived from a subject and allowed to grow in vitro for a limited number of passages, i.e. splitting, of the culture. In some embodiments, particularly CAR embodiments, the cells are obtained from a human subject. Therefore, human cells expressing and / or including the disclosed polypeptides are provided. In preferred embodiments, the human cells include or express a Kenv-CAR. For example, in some forms, the cells are autologous cells, i.e., cells obtained from a subject prior to introduction of the Kenv-CAR, and / or nucleic acids, or vectors encoding the same, and re-introduction to the same subject following modification. In other forms, the cells are heterologous cells, i.e., cells obtained from a different subject than the intended recipient. In some forms, the cells are frozen prior to or after introduction of the Kenv-CAR. Methods and compositions for freezing and thawing viable eukaryotic cells are known in the art. In some forms, the cells are autologous immune cells, such as T cells or progenitor cells / stem cells. In some forms, cells are obtained from a healthy subject. In other forms, cells are obtained from a subject identified as having or at risk of having a disease or disorder, such as cancer or other disease or condition such as those mentioned elsewhere herein. In some embodiments, the introduction of the polypeptides to the cells occurs through genetic modification of the cells. In some embodiments, genetic modification of the cell includes introduction of nucleic acids, or vectors encoding the polypeptides to the cell for expression of the45728747v153 polypeptides within the cell. Therefore, genetically modified (transgenic) cells including the disclosed proteins, e.g., Kenv-CAR fusion proteins, are described. In some forms, the cells are human immune cells, such as T cells, Natural Killers (NK) cells, macrophages, dendritic cells etc. Therefore, human immune cells that include or express the disclosed polypeptides including the Kenv-CAR polypeptides are described. In some forms, prior to expansion and genetic modification, immune cells such as T cells are obtained from a diseased or healthy subject. The cells can be obtained from a number of samples, including peripheral blood mononuclear cells, bone marrow, lymph node tissue, cord blood, thymus tissue, tissue from a site of infection, ascites, pleural effusion, spleen tissue, and tumors. In some forms, the immune cells are obtained from a unit of blood collected from a subject using any number of techniques known to the skilled artisan, such as FICOLL™ separation. In one preferred form, cells from the circulating blood of an individual are obtained by apheresis. The apheresis product typically contains lymphocytes, including T cells, monocytes, granulocytes, B cells, other nucleated white blood cells, red blood cells, and platelets. The cells collected by apheresis can be washed to remove the plasma fraction and to place the cells in an appropriate buffer or media for subsequent processing steps. In some forms, the cells are washed with phosphate buffered saline (PBS). In some forms, the wash solution lacks calcium and can lack magnesium or can lack many if not all divalent cations. After washing, the cells can be resuspended in a variety of biocompatible buffers, such as, for example, Ca2+-free, Mg2+-free PBS, PLASMALYTE A, or other saline solution with or without buffer. Alternatively, the undesirable components of the apheresis sample are removed and the cells directly resuspended in culture media. In some forms, T cells are isolated from peripheral blood lymphocytes by lysing the red blood cells and depleting the monocytes, for example, by centrifugation through a PERCOLL™ gradient or by counterflow centrifugal elutriation. In specific forms, a specific subpopulation of T cells, such as CD3+, CD28+, CD4+, CD8+, CD45RA+, and CD45RO+ T cells, is further isolated by positive or negative selection techniques. For example, in some forms, T cells are isolated by incubation with anti-CD3 / anti-CD28 (i.e., 3×28)-conjugated beads, such as DYNABEADS® M-450 CD3 / CD28 T, for a time period sufficient for positive selection of the desired T cells. E. Pharmaceutical Compositions The compositions can be formulated with appropriate pharmaceutically acceptable carriers into pharmaceutical compositions for administration to an individual in need thereof. The formulations can be administered enterally (e.g., oral) or parenterally (e.g., by injection or infusion). The compositions can be formulated for parenteral administration. “Parenteral administration”, as used herein, means administration by any method other than through the45728747v154 digestive tract or non-invasive topical or regional routes. For example, parenteral administration may include administration to a patient intravenously, intradermally, intraarterially, intraperitoneally, intralesionally, intracranially, intraarticularly, intraprostatically, intrapleurally, intratracheally, intravitreally, intratumorally, intramuscularly, subcutaneously, subconjunctivally, intravesicularly, intrapericardially, intraumbilically, or transmucosal (nasal, vaginal, pulmonary, or rectal), e.g., by injection, and by infusion. In some embodiments, the compositions are administered systemically by, for example, injection or infusion. In some embodiments, the compositions are administered locally by injection or infusion. Parenteral formulations can be prepared as aqueous compositions using techniques known in the art. Typically, such compositions can be prepared as injectable formulations, for example, solutions or suspensions; solid forms suitable for using to prepare solutions or suspensions upon the addition of a reconstitution medium prior to injection; emulsions, such as water-in-oil (w / o) emulsions, oil-in-water (o / w) emulsions, and microemulsions thereof, liposomes, or emulsomes. The carrier can be a solvent or dispersion medium containing, for example, water, ethanol, one or more polyols (e.g., glycerol, propylene glycol, and liquid polyethylene glycol), oils, such as vegetable oils (e.g., peanut oil, corn oil, sesame oil, etc.), and combinations thereof. The proper fluidity can be maintained, for example, by the use of a coating, such as lecithin, by the maintenance of the required nanocarrier size in the case of dispersion and / or by the use of surfactants. In many cases, isotonic agents, for example, sugars or sodium chloride, are included. Solutions and dispersions of the active compounds as the free acid or base or pharmacologically acceptable salts thereof can be prepared in water or another solvent or dispersing medium suitably mixed with one or more pharmaceutically acceptable excipients including, but not limited to, surfactants, dispersants, emulsifiers, pH modifying agents, viscosity modifying agents, and combination thereof. Suitable surfactants may be anionic, cationic, amphoteric or nonionic surface active agents. Suitable anionic surfactants include, but are not limited to, those containing carboxylate, sulfonate and sulfate ions. Examples of anionic surfactants include sodium, potassium, ammonium of long chain alkyl sulfonates and alkyl aryl sulfonates such as sodium dodecylbenzene sulfonate; dialkyl sodium sulfosuccinates, such as sodium dodecylbenzene sulfonate; dialkyl sodium sulfosuccinates, such as sodium bis-(2-ethylthioxyl)-sulfosuccinate; and alkyl sulfates such as sodium lauryl sulfate. Cationic surfactants include, but are not limited to, quaternary ammonium compounds such as benzalkonium chloride, benzethonium chloride, cetrimonium bromide, stearyl dimethylbenzyl ammonium chloride, polyoxyethylene and coconut amine. Examples of nonionic surfactants include45728747v155 ethylene glycol monostearate, propylene glycol myristate, glyceryl monostearate, glyceryl stearate, polyglyceryl-4-oleate, sorbitan acylate, sucrose acylate, PEG-150 laurate, PEG-400 monolaurate, polyoxyethylene monolaurate, polysorbates, polyoxyethylene octylphenylether, PEG-1000 cetyl ether, polyoxyethylene tridecyl ether, polypropylene glycol butyl ether, Poloxamer®401, stearoyl monoisopropanolamide, and polyoxyethylene hydrogenated tallow amide. Examples of amphoteric surfactants include sodium N-dodecyl-beta-alanine, sodium N-lauryl-β-iminodipropionate, myristoamphoacetate, lauryl betaine and lauryl sulfobetaine. The formulation can contain a preservative to prevent the growth of microorganisms. Suitable preservatives include, but are not limited to, parabens, chlorobutanol, phenol, sorbic acid, and thimerosal. The formulation may also contain an antioxidant to prevent degradation of the active agent(s). The formulation is typically buffered to a pH of 3-8 for parenteral administration upon reconstitution. Suitable buffers include, but are not limited to, phosphate buffers, acetate buffers, and citrate buffers. Water soluble polymers are often used in formulations for parenteral administration. Suitable water-soluble polymers include, but are not limited to, polyvinylpyrrolidone, dextran, carboxymethylcellulose, and polyethylene glycol. Sterile injectable solutions can be prepared by incorporating the active compounds in the required amount in the appropriate solvent or dispersion medium with one or more of the excipients listed above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the various sterilized active ingredients into a sterile vehicle which contains the basic dispersion medium and the required other ingredients from those listed above. In the case of sterile powders for the preparation of sterile injectable solutions, exemplary methods of preparation include vacuum-drying and freeze-drying techniques which yield a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof. Enteral formulations are prepared using pharmaceutically acceptable carriers. As generally used herein “carrier” includes, but is not limited to, diluents, preservatives, binders, lubricants, disintegrators, swelling agents, fillers, stabilizers, and combinations thereof. Polymers used in the dosage form include hydrophobic or hydrophilic polymers and pH dependent or independent polymers. Hydrophobic and hydrophilic polymers include, but are not limited to, hydroxypropyl methylcellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, carboxy methylcellulose, polyethylene glycol, ethylcellulose, microcrystalline cellulose, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl acetate, and ion exchange resins.45728747v156 Carrier also includes all components of the coating composition, which may include plasticizers, pigments, colorants, stabilizing agents, and glidants. Formulations can be prepared using one or more pharmaceutically acceptable excipients, including diluents, preservatives, binders, lubricants, disintegrators, swelling agents, fillers, stabilizers, and combinations thereof. Controlled release dosage formulations can be prepared as described in standard references such as “Pharmaceutical dosage form tablets”, eds. Liberman et. al. (New York, Marcel Dekker, Inc., 1989), “Remington – The science and practice of pharmacy”, 20th ed., Lippincott Williams & Wilkins, Baltimore, MD, 2000, and “Pharmaceutical dosage forms and drug delivery systems”, 6th Edition, Ansel et al., (Media, PA: Williams and Wilkins, 1995). These references provide information on excipients, materials, equipment and process for preparing tablets and capsules and delayed release dosage forms of tablets, capsules, and granules. These references provide information on carriers, materials, equipment and process for preparing tablets and capsules and delayed release dosage forms of tablets, capsules, and granules. Stabilizers are used to inhibit or retard drug decomposition reactions which include, by way of example, oxidative reactions. Suitable stabilizers include, but are not limited to, antioxidants, butylated hydroxytoluene (BHT); ascorbic acid, its salts and esters; Vitamin E, tocopherol and its salts; sulfites such as sodium metabisulphite; cysteine and its derivatives; citric acid; propyl gallate, and butylated hydroxyanisole (BHA). In some embodiments, the compositions are formulated for mucosal administration, such as through nasal, pulmonary, or buccal delivery. Mucosal formulations may include one or more agents for enhancing delivery through the nasal mucosa. Agents for enhancing mucosal delivery are known in the art, see for example U.S. Patent Application No.20090252672 to Eddington, and U.S. Patent Application No.20090047234 to Touitou. Acceptable agents include, but are not limited to, chelators of calcium (EDTA), inhibitors of nasal enzymes (boro-leucin, aprotinin), inhibitors of muco-ciliar clearance (preservatives), solubilizers of nasal membrane (cyclodextrin, fatty acids, surfactants) and formation of micelles (surfactants such as bile acids, Laureth 9 and taurodehydrofusidate (STDHF)). Compositions may include one or more absorption enhancers, including surfactants, fatty acids, and chitosan derivatives, which can enhance delivery by modulation of the tight junctions (TJ) (B. J. Aungst, et al., J. Pharm. Sci.89(4):429-442 (2000)). In general, the optimal absorption enhancer should possess the following qualities: its effect should be reversible, it should provide a rapid permeation enhancing effect on the cellular membrane of the mucosa, and it should be non-cytotoxic at the effective concentration level and without deleterious and / or irreversible effects on the cellular membrane or cytoskeleton of the TJ.45728747v157 Any of the disclosed compositions including, but not limited to the provided Kenv binder polypeptides and CAR fusion proteins formed therefrom and / or nucleic acids encoding the same, can be delivered to target cells using a delivery vehicle. The delivery vehicles can be, for example, polymeric particles, inorganic particles, silica particles, liposomes, micelles, multilamellar vesicles, etc. Delivery vehicles may be microparticles or nanoparticles. Nanoparticles are often utilized for intertissue application, penetration of cells, and certain routes of administration. The nanoparticles may have any desired size for the intended use. The nanoparticles may have any diameter from 10 nm up to about 1,000 nm. The nanoparticle can have a diameter from 10 nm to 900 nm, from 10 nm to 800 nm, from 10 nm to 700 nm, from 10 nm to 600 nm, from 10 nm to 500 nm, from 20 nm from 500 nm, from 30 nm to 500 nm, from 40 nm to 500 nm, from 50 nm to 500 nm, from 50 nm to 400 nm, from 50 nm to 350 nm, from 50 nm to 300 nm, or from 50 nm to 200 nm. In some embodiments the nanoparticles can have a diameter less than 400 nm, less than 300 nm, or less than 200 nm. The range can be between 50 nm and 300 nm. Thus, in some embodiments, the delivery vehicles are nanoscale compositions, for example, 10 nm up to, but not including, about 1 micron. However, it will be appreciated that in some embodiments, and for some uses, the particles can be smaller, or larger (e.g., microparticles, etc.). Although many of the compositions disclosed herein are referred to as nanoparticle or nanocarrier compositions, it will be appreciated that in some embodiments and for some uses the carrier can be somewhat larger than nanoparticles. Such compositions can be referred to as microparticulate compositions. For example, a nanocarriers according to the present disclosure may be a microparticle. Microparticles can a diameter between, for example, 0.1 and 100 µm in size. As provided are pharmaceutical packs and kits including one or more containers filled with antibody or fusion protein or nucleic acid. Additionally, one or more other prophylactic or therapeutic agents useful for the treatment of a disease can also be included in the pharmaceutical pack or kit. One embodiment provides a pharmaceutical pack or kit including one or more containers filled with one or more of the ingredients of the pharmaceutical compositions. Optionally associated with such container(s) can be a notice in the form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals or biological products, which notice reflects approval by the agency of manufacture, use or sale for human administration. Also provided are kits that can be used in the below methods. In one embodiment, a kit includes one or more antibodies or fusion proteins or nucleic acids. In another embodiment, a kit further includes one or more other prophylactic or therapeutic agents useful for the treatment of45728747v158 cancer, in one or more containers. In certain embodiments, the other prophylactic or therapeutic agent is a chemotherapeutic. In other embodiments, the prophylactic or therapeutic agent is a biological or hormonal therapeutic. III. Methods of Use A. Methods of Detecting HERV-K Env The disclosed Kenv binders can be used to detect HERV-K, and more particularly HERV-K Env protein, in various research, diagnostic, and prognostic applications. Typically the binders are used to detect HERV-K Env protein or fragment thereof, e.g., an fragment thereof in a biological sample. Detection of Env protein or fragment can indicate the presence of HERV-K. Likewise, the disclosed binders can used to isolate or purify HERV-K Env, e.g., by immunoprecipitation, etc. Exemplary biological sources for detection of HERV-K Env protein and fragments thereof is tissue including biopsy material e.g., from a tumor, or cells thereof, and primary or immortalized cultured cells. Other samples include, but are not limited to saliva, urine, serum, and blood which may or may not include blood cells such as white blood cells such as immune cells, or plasma cells. A sample may be obtained and processed using well-known and routine clinical methods. In some aspects, the biological sample includes a plurality of cells. The cells can be intact and / or permeabilized. In certain aspects, the biological sample includes fresh or frozen tissue. In specific aspects, the biological sample includes formalin fixed, paraffin embedded tissue. In some embodiments, the cells are permeabilized. Thus, in some embodiments, a cell lysate or homogenate is subjected to HERV-K Env protein or fragment detection. HERV-K Env protein or fragment thereof is typically detected using one or more of the antibodies or other antigen binding molecules provided herein. The HERV-K Env protein or fragment thereof can be detected by any suitable method utilizing the provided antibodies. In preferred embodiments, the HERV-K Env protein or fragment thereof is detected and / or measured by an immunoassay. Immunoassays utilize biospecific capture reagents, such as antibodies, to capture or locate the HERV-K Env protein or fragment. The steps of various useful immunodetection methods have been described in the scientific literature. In general, the immunobinding methods include obtaining a sample, and contacting the sample with an antibody specific for the protein to be detected, as the case may be, under conditions effective to allow the formation of immunocomplexes. In general, the detection of immunocomplex formation is well known in the art and may be achieved through the application of numerous approaches. These methods are generally based upon the detection of a label or marker, such as any of those radioactive, fluorescent, biological and enzymatic tags. Of course, one may find additional45728747v159 advantages through the use of a secondary binding ligand such as a second antibody and / or a biotin / avidin ligand binding arrangement, as is known in the art. The antibody employed in the detection may itself be linked to a detectable label (also referred to as a detectable substance or reporter), wherein one would then simply detect this label, thereby allowing the amount of the primary immune complexes in the composition to be determined. Alternatively, the first antibody that becomes bound within the primary immune complexes may be detected by means of a second binding ligand that has binding affinity for the antibody. In these cases, the second binding ligand may be linked to a detectable label. The second binding ligand is itself often an antibody, which may thus be termed a “secondary” antibody. The primary immune complexes are contacted with the labeled, secondary binding ligand, or antibody, under effective conditions and for a period of time sufficient to allow the formation of secondary immune complexes. The secondary immune complexes are then generally washed to remove any non-specifically bound labeled secondary antibodies or ligands, and the remaining label in the secondary immune complexes is then detected. Traditional immunoassays including, for example, sandwich immunoassays including ELISA or fluorescence-based immunoassays, as well as other enzyme immunoassays can be used for detecting the HERV-K Env protein or fragment thereof. In other embodiments, the detection of the HERV-K Env protein or fragment thereof is carried out on slides of test material (e.g., immunohistochemistry), immunoblotting (e.g., Western blotting), surface plasmon resonance (e.g. Biacore), or by flow cytometry (FACS) analysis). Other specific examples include, but are not limited to, enzyme immunoassay (EIA), radioimmunoassay (RIA), fluoroimmunoassay (FIA), chemiluminescent immunoassay (CLIA) and counting immunoassay (CIA), homogeneous enzyme-multiplied immunoassays (“EMIT”), apoenzyme reactivation immunoassay (“ARIS”), dipstick immunoassays, and immuno- chromatography assays. Most assays now use nonradioactive labels. Enzyme immunoassays (enzyme-linked immunosorbent assays, or ELISA; immunometric assays) can use enzymes as labels, such as, for example, horseradish peroxidase or alkaline phosphatase. Chemiluminescent immunoassays (CIA) can use luminol. Fluorimetric immunoassays (FIA) use fluorescent compounds (e.g., fluorescein) as labels. The assays can be homogenous or heterogeneous assays, competitive and non-competitive assays. There are four main kinds of ELISA: sandwich, competitive, direct, and indirect assays. These methods differ in how the antibody or antigen is attached to the solid plate, and how the signal is detected. For example, in a sandwich ELISA, for example, an antibody is immobilized on a plate. The sample containing the target antigen is added, which binds to the antibody and so is45728747v160 immobilized on the plate. Next, a second type of antibody is added, which also binds to the target antigen on the plate, forming a ‘sandwich’ with the target antigen in the middle. The second antibody is linked to an enzyme, called a reporter enzyme, which allows the binding reaction to be measured by creating a color signal. To create this signal, first any unbound antibody is washed away, and a colorimetric substrate is added. The enzyme catalyzes a reaction of the substrate, creating a color change. A stronger color signal indicates more target antigen is present. An example of this is a home pregnancy test. In some embodiments, the first or second antibody is one of the disclosed antibodies, and the other antibody is one that detects HERV-K Env protein or fragment thereof, but may or may not detect its phosphorylated state, and thus may target a different antigen of the protein (e.g., a non-phosphorylated antigen). In some embodiments, the assay is in the form of a sandwich assay, which is a noncompetitive immunoassay, wherein the molecule to be detected and / or quantified is bound to a first antibody and to a second antibody. The first antibody may be bound to a solid phase, e.g., a bead, a surface of a well or other container, a chip or a strip, and the second antibody is an antibody which is labeled, e.g. with a dye, with a radioisotope, or a reactive or catalytically active moiety. The amount of labeled antibody bound to the analyte is then measured by an appropriate method. The general composition and procedures involved with “sandwich assays” are well-established and known to the skilled person. Immunohistochemistry (IHC) is a process of localizing antigens (e.g., proteins) in tissue utilizing antigen-specific antibodies. The antigen-binding antibody can be conjugated or fused to a tag that allows its detection, e.g., via visualization. In some embodiments, the tag is an enzyme that can catalyze a color-producing reaction, such as alkaline phosphatase or horseradish peroxidase. The enzyme can be fused to the antibody or non-covalently bound, e.g., using a biotin-avidin system. Alternatively, the antibody can be tagged with a fluorophore, such as fluorescein, rhodamine, DyLight Fluor or Alexa Fluor. The antigen-binding antibody can be directly tagged or it can itself be recognized by a detection antibody that carries the tag. Quantitative immunochemical techniques can also be used. For example, the Quantitative Tissue Biomarker Platform from HistoRx and / or measuring immunofluorescence level(s) can be used to quantify levels of HERV-K Env protein or a fragment thereof. Western blotting can be used and can be quantitative or qualitative. A typical Western blotting procedure includes the steps of immunoprecipitating a target protein from a lysate of cells expressing the protein, performing an SDS-PAGE with said protein, transferring the protein to a nitrocellulose membrane, incubating the nitrocellulose membrane with said antibody, detecting said45728747v161 antibody with a secondary antibody conjugated to a fluorescent or chromogenic compound (e.g. peroxidases such as horseradish peroxidase (HRP), alkaline phosphatase (AP), IRDye near-infrared (NIR) fluorescent dyes), and quantifying the respective signal of said compound (e.g. fluorescence, luminescence, chromogenic enzyme substrate). The ratio of two signals generated by Western blotting employing the same antibody but two different samples can be calculated, thereby determining how much more / less (fold-change) of the HERV-K Env protein or fragment thereof is present in one sample compared to another. In some embodiments, the methods provided herein involve determining the presence, absence, and / or concentration of HERV-K Env protein or a fragment thereof in a cell, and / or the number of cell positive for HERV-K Env protein or fragment thereof in sample by fluorescence activated cell sorting (FACS) using a flow cytometry device (e.g., Beckman Coulter Z2 Coulter Counter, Beckman Coulter Inc.). In some embodiments, a FACs-based method include the step of preparing the output composition for detection by flow cytometry before the HERV-K Env protein or fragment thereof can be detected. For example, the output composition can be incubated with a fluorescently labeled Kenv binder, and then the sample can be analyzed using a flow cytometer. In some embodiments, the cells are permeabilized to facilitate antibody access to intracellular HERV- K Env protein or fragment thereof. In flow cytometry, cells bound by fluorescently labeled affinity reagents are carried in a fluidic stream, are separated based on size and / or fluorescent signal and are subsequently analyzed and counted using a FACS software program (e.g., FlowJo software). The number or approximate number of cells can be determined by detection of the fluorescent signal, which optionally can be determined or processed by the FACS software program to provide the total or approximate number of particles in the output composition. In some embodiments, a sample is analyzed by means of a biochip. Biochips generally include solid substrates and have a generally planar surface, to which a capture reagent (also called an adsorbent or affinity reagent) is attached. Frequently, the surface of a biochip includes a plurality of addressable locations, each of which has the capture reagent bound there. Protein biochips are biochips adapted for the capture of polypeptides. Many protein biochips are described in the art. These include; for example, protein biochips produced by Ciphergen Biosystems, Inc. (Fremont, Calif.), Packard BioScience Company (Meriden Conn.), Zyomyx (Hayward, Calif.), Phylos (Lexington, Mass.) and Biacore (Uppsala, Sweden). Photonic biosensors can be used in label-free assays. For example, photonic biosensors combine photonic sensing with bio recognition technology to create label-free testing on-chip. Instead of moving electrons around on silicon chips, light is moved around on silicon chips via waveguides. This technology has allowed the development of miniature lab-on-a-chip label-free45728747v162 immunoassay (LFIA) devices. These devices are functionalized with capture antibodies and have a resonance condition of light. This resonance wavelength will be shifted by a reaction between the capture antibody and the target antigen due to the change in refractive index. Measuring the shift in resonance wavelength provides a readout of a binding event. Label-free assays therefore enable the detection of antigen-antibody binding without the use of an additional label, resulting in increased assay sensitivity and decreased working time. B. Methods of Diagnosis The HERV-K Env and fragments thereof can be used in diagnostic tests to assess cancer and / or other HERV-K Env-related disease and disorder status in a subject, e.g., to distinguish between normal cells and diseased cells, and disease status. For example, disease status includes, without limitation, the presence or absence of disease (e.g., cancer v. non-cancer), characterization of cells including cancer cells (e.g., level of aberrant HERV-K activity), the risk of developing disease, the stage of the disease (e.g., non-invasive or early-stage cancer v. invasive or metastatic cancer), the progress of disease (e.g., progress of disease or remission of disease over time) and the effectiveness or response to treatment of disease. Based on this status, further procedures may be indicated, including additional diagnostic tests or therapeutic procedures or regimens. Representative cancers and therapies are discussed in more detail below. The HERV-K Env can be present and / or expressed in cancer including but not limited to those mentioned elsewhere herein, and therefore, detection thereof is useful in aiding in the determination of cancer and / or other HERV-K Env-related diseases and disorders. An exemplary method involves, first, measuring HERV-K Env protein or a fragment thereof in a subject sample using the methods described herein, and, second, comparing the measurement with a diagnostic amount or cut-off that distinguishes a positive cancer and / or other HERV-K Env-related disease and disorder status from a negative cancer and / or other HERV-K Env-related disease and disorder status. The diagnostic amount represents a measured amount of HERV-K Env protein or an fragment thereof above which a subject is classified as having a particular status. For example, because the HERV-K Env protein or a fragment thereof is up-regulated compared to normal during cancer and / or other HERV-K Env-related diseases and disorders, then a measured amount above the diagnostic cutoff provides a diagnosis or status of the cancer and / or other HERV-K Env-related diseases and disorders. As is well understood in the art, by adjusting the particular diagnostic cut- off used in an assay, one can increase sensitivity or specificity of the diagnostic assay depending on the preference of the diagnostician. The particular diagnostic cut-off can be determined, for example, by measuring the amount of the HERV-K Env protein or fragment thereof in a statistically45728747v163 significant number of samples from subjects with the different cancer statuses and drawing the cut- off to suit the diagnostician's desired levels of specificity and sensitivity. C. Determining Risk of Developing Disease Methods for determining the risk of developing disease in a subject are also provided. HERV-K Env protein or fragment thereof amounts or patterns can be characteristic of various risk states, e.g., high, medium, or low. The risk of developing a disease is determined by measuring the HERV-K Env protein or fragment thereof and then either submitting them to a classification algorithm or comparing them with a reference amount and / or pattern of HERV-K Env protein or an fragment thereof that is associated with the particular risk level. D. Determining Stage of Disease Another embodiment provides methods for determining the stage of disease in a subject. Each stage of the disease can have a characteristic amount of HERV-K Env protein or fragment thereof. The stage of a disease is determined by measuring the HERV-K Env protein or a fragment thereof and then either submitting them to a classification algorithm or comparing them with a reference amount and / or pattern of the HERV-K Env protein or fragment thereof that is associated with the particular stage. E. Determining Course (Progression / Remission) of Disease Still another embodiment provides methods for determining the course of disease in a subject. Disease course refers to changes in disease status over time, including disease progression (worsening) and disease regression (improvement). Over time, the amounts or relative amounts (e.g., the pattern) of the HERV-K Env protein or fragment thereof changes. This method involves measuring HERV-K Env protein or a fragment thereof in a subject at least two different time points, e.g., a first time and a second time, and comparing the change in amounts, if any. The course of disease is determined based on these comparisons. Similarly, this method is useful for determining the response to treatment. If a treatment is effective, then the HERV-K Env protein or a fragment thereof will trend toward normal, while if treatment is ineffective, the HERV-K Env protein or a fragment thereof will trend toward disease indications. F. Subject Management In certain embodiments of the method including the detection and / or analysis of HERV-K Env protein or a fragment thereof further includes managing subject treatment based on the status. Such management includes the actions of the physician or clinician subsequent to determining cancer and / or other HERV-K Env-related disease and disorder status. For example, if a physician makes a diagnosis of cancer and / or other HERV-K Env-related disease and disorder, then a certain regime of treatment, such as prescription or administration of chemotherapy, radiation,45728747v164 immunotherapy, including, but not limited to administration of the compositions discussed in more detail below, might follow. Alternatively, a diagnosis of non-cancer or benign tumor might be followed with further testing to determine a specific disease that the patient might be suffering from. Also, if the diagnostic test gives an inconclusive result on cancer and / or other HERV-K Env- related disease and disorder, further tests may be required. One embodiment provides a method for selecting a subject for treatment for cancer and / or other HERV-K Env-related disease and disorder by detecting the presence or quantity of HERV-K Env protein or an fragment thereof in a sample from a subject suspected of having cancer and / or other HERV-K Env-related disease and disorder, comparing the levels of HERV-K Env protein or a fragment thereof in the sample to a predetermined standard, wherein the patient is selected for treatment for cancer and / or other HERV-K Env-related disease and disorder if HERV-K Env protein or an fragment thereof, or a certain level thereof, is detected in the sample. Such treatments can be those known to be effective and / or preferred for treating subjects with aberrant HERV-K Env protein or an fragment thereof expression. Exemplary treatments are discussed below. In some embodiments, the methods additionally or alternatively include identifying the subject as not having a HERV-K Env-related disease and disorder, when the test is negative. Thus, although the subject may have a cancer or another diseases or disorder, the subject can be identified as negative for aberrant HERV-K Env-related cancer and other diseases and disorder. Such embodiments may lead to selection of alternative treatments and may avoid treatments known to be effective or preferred for treating subjects with aberrant HERV-K Env-positive conditions, and / or may include treatments that are known not to be effective and / or preferred for treating subjects with aberrant HERV-K Env-positive conditions. Additional embodiments relate to the communication of assay results or diagnoses or both to technicians, physicians or patients, for example. In certain embodiments, computers will be used to communicate assay results or diagnoses or both to interested parties, e.g.: physicians and their patients. In some embodiments, the assays will be performed or the assay results analyzed in a country or jurisdiction which differs from the country or jurisdiction to which the results or diagnoses are communicated. In a preferred embodiment a diagnosis based on the presence or absence in a test subject of HERV-K Env protein or a fragment thereof is communicated to the subject as soon as possible after the diagnosis is obtained. The diagnosis may be communicated to the subject by the subject's treating physician. Alternatively, the diagnosis may be sent to a test subject by email or communicated to the subject by phone. A computer may be used to communicate the diagnosis by email or phone. In certain embodiments, the message containing results of a diagnostic test may be45728747v165 generated and delivered automatically to the subject using a combination of computer hardware and software which will be familiar to artisans skilled in telecommunications. In certain embodiments all or some of the method steps, including the assaying of samples, diagnosing of diseases, and communicating of assay results or diagnoses, may be carried out in diverse (e.g., foreign) jurisdictions. G. Screening Assays The Kenv binders can be used to screen for compounds that modulate the expression of the HERV-K Env protein or fragments thereof in vitro or in vivo, which compounds in turn may be useful in treating or preventing cancer and / or other HERV-K Env-related diseases and disorders in patients. Compounds suitable for therapeutic testing may be screened initially by identifying compounds which reduce the presence of HERV-K or a fragment thereof in the cancer and / or other HERV-K Env-related disease and disordered cells. Test compounds capable of modulating the presence and / or expression of HERV-K or a fragment thereof in cancer cells or other HERV-K Env-related disease and disorder may be administered to patients who are suffering from or are at risk of developing cancer having the HERV-K or a fragment thereof. For example, the administration of a test compound that decreases the presence or activity of HERV-K or a fragment thereof may decrease the risk of cancer and / or other HERV-K Env-related disease and disorder in a patient if the increased presence or activity of the HERV-K or a fragment thereof is responsible or indicative, at least in part, for the onset of the cancer and / or other HERV-K Env-related disease and disorder. At the clinical level, screening a test compound includes obtaining samples from test subjects before and after the subjects have been exposed to a test compound. The levels in the samples of HERV-K or a fragment thereof can be measured and analyzed to determine whether the levels of the HERV-K or a fragment thereof changes after exposure to a test compound. The samples can be analyzed by any appropriate means known to one of skill in the art including e.g., by the means described herein. In a further embodiment, the changes in the level of expression of HERV-K or a fragment thereof can be measured using in vitro methods and materials. For example, human tissue cultured cells which express, or are capable of expressing, HERV-K or a fragment thereof may be contacted with test compounds. Subjects who have been treated with test compounds can be routinely examined for any physiological effects which may result from the treatment. In particular, the test compounds are evaluated for their ability to decrease disease likelihood in a subject. Alternatively, if the test compounds are administered to subjects who have previously been diagnosed with cancer and / or other HERV-K Env-related disease and disorder, test compounds will be screened for their ability to slow or stop the progression of the disease.45728747v166 H. Assessing the Effectiveness of Treatment or Risk for Developing Cancer and / or other HERV-K Env-related Diseases and Disorders Methods for determining the course of cancer and / or other HERV-K Env-related diseases and disorders in a subject are also provided. Disease course refers to changes in disease status over time, including disease progression (worsening) and disease regression (improvement). Over time, the amounts or relative amounts (e.g., the pattern) of HERV-K Env protein or an fragment thereof changes. Accordingly, this method involves measuring HERV-K Env protein or an fragment thereof in a subject at least two different time points, e.g., a first time and a second time, and comparing the change in amounts, if any. The course of disease is determined based on these comparisons. Similarly, this method is useful for determining the response to treatment. If a treatment is effective, then the HERV-K Env protein or fragment thereof will trend toward normal, while if treatment is ineffective, the HERV-K Env protein or fragment thereof will trend toward disease indications. In yet another example, the binders can be used in studies to determine if the subject is at risk for developing cancer and / or other HERV-K Env-related disease and disorder. IV. Diseases to be Detected and / or Treated HERV-K, and particularly HML-2, has been implicated in a number of human pathologies. See, e.g., Garcia-Montojo, et al., “Human endogenous retrovirus-K (HML-2): a comprehensive review,” Crit Rev Microbiol.2018 Nov;44(6):715-738. doi: 10.1080 / 1040841X.2018.1501345. Epub 2018 Oct 14. PMID: 30318978; PMCID: PMC6342650, which is specifically incorporated by reference herein in its entirety. Any of the disclosed compositions and methods can be used to detect, diagnose, prognose, and / or treat any HERV-K related disease or disorder. In some embodiments, the disease or disorder is a cancer, neurological diseases, or autoimmune disease. A. Cancer For example, in some embodiments, the disease or disorder is cancer. In a mature animal, a balance usually is maintained between cell renewal and cell death in most organs and tissues. The various types of mature cells in the body have a given life span; as these cells die, new cells are generated by the proliferation and differentiation of various types of stem cells. Under normal circumstances, the production of new cells is so regulated that the numbers of any particular type of cell remain constant. Occasionally, though, cells arise that are no longer responsive to normal growth-control mechanisms. These cells give rise to clones of cells that can expand to a considerable size, producing a tumor or neoplasm. A tumor that is not capable of indefinite growth and does not invade the healthy surrounding tissue extensively is benign. A tumor that continues to grow and becomes progressively invasive is malignant. The term cancer refers specifically to a45728747v167 malignant tumor. In addition to uncontrolled growth, malignant tumors exhibit metastasis. In this process, small clusters of cancerous cells dislodge from a tumor, invade the blood or lymphatic vessels, and are carried to other tissues, where they continue to proliferate. In this way a primary tumor at one site can give rise to a secondary tumor at another site. The compositions and methods described herein are useful for detecting, diagnosing, prognosing, and treating subjects having benign or malignant tumors. In some embodiments, treatment delays or inhibits the growth of a tumor in a subject, reduces the growth or size of the tumor, inhibits or reduces metastasis of the tumor, and / or inhibits or reduces symptoms associated with tumor development or growth. Malignant tumors which may be treated are classified herein according to the embryonic origin of the tissue from which the tumor is derived. Carcinomas are tumors arising from endodermal or ectodermal tissues such as skin or the epithelial lining of internal organs and glands. The compositions are particularly effective in treating carcinomas. Sarcomas, which arise less frequently, are derived from mesodermal connective tissues such as bone, fat, and cartilage. The leukemias and lymphomas are malignant tumors of hematopoietic cells of the bone marrow. Leukemias proliferate as single cells, whereas lymphomas tend to grow as tumor masses. Malignant tumors may show up at numerous organs or tissues of the body to establish a cancer. The types of cancer that can be treated with the provided compositions and methods include, but are not limited to, cancers such as vascular cancer such as multiple myeloma, lymphoma, adenocarcinomas and sarcomas, of bone, bladder, brain, breast, cervical, colon, colo-rectal, esophageal, head and neck, kidney, liver, hepatocellular, lung, nasopharangeal, pancreatic, prostate, skin (e.g., melanoma), stomach, and uterine. In particular embodiments, the cancer is a seminoma, a teratocarcinoma, a urothelial cancer, an endometrial cancer, or a germ cell Tumor. In some embodiments, the compositions are used to treat multiple cancer types concurrently. The compositions can also be used to treat metastases or tumors at multiple locations. HML-2 has been implicated in cancer development, as its expression has been associated with many cancer types such as teratocarcinoma, germ cell tumors, ovarian, breast, prostate, and skin cancer such as melanoma. Thus, in some embodiments, the disease or disorder teratocarcinoma, germ cell tumors, ovarian, breast, prostate, or a skin cancer such as melanoma. HML-2 Env has also been implicated as a potential oncogenic stimulus. Using an MCF10A cell line, HML-2 Env (K108L) expression from a lentiviral construct endowed the cells with the ability to transition from epithelial cells to mesenchymal cells; the cells displayed an increase in cellular migration and invasion. Additionally, a recent study showed that downregulation of Env prompted a decrease in cell proliferation and a concomitant reduction of RAS, p-ERK, and p-AKT45728747v168 expression. Thus, in some embodiments, detection of HERV-K Env is an indication of oncogenic potential, and thus the severity, of a cancer. B. Immunosuppression and Autoimmunity In some embodiments, the disease or condition is immunosuppression. Immunosuppressive properties are characteristic of many retroviruses and HML-2 has retained this feature. HML-2 particles released from a human teratocarcinoma cell line, a recombinant Env transmembrane (TM) protein, and a peptide corresponding to a highly-conserved region of the TM were all able to inhibit human immune cell proliferation, change the expression of numerous cytokines, such as increasing IL-10, and affect gene expression. Similarly, Rec has been shown to interact with β-catenin, which induces immune tolerance to tumors, and contributes to carcinogenesis. Additionally, sequence variations and insertional polymorphisms of HERV-K have been associated with diabetes and other autoimmune diseases and inflammatory conditions such as rheumatoid arthritis. Thus, in some embodiments, the disease or disorder is diabetes or another autoimmune diseases or disorder such as rheumatoid arthritis. C. Neurological Diseases and Disorders The disease or disorder can be a neurological disease or disorder. The evidence for the role of HML-2 in the pathophysiology of sporadic amyotrophic lateral sclerosis (ALS) is strong. Several groups have identified the presence of RT activity in the blood and cerebrospinal fluid of patients with ALS. HML-2 gene products, gag, pol and env can be detected in the brains of ALS patients, and RT and Env proteins are expressed in cortical neurons. This expression was specific for ALS, since it could not be found in patients with Parkinson’s or Alzheimer’s disease. Forced expression of HML-2 in neurons, lead to neuronal injury and cell death in transgenic mice in which HML-2 Env (consensus) was expressed under a neuronal promoter developed progressive motor dysfunction, with specific loss of neurons in the motor cortex and the anterior horn of the spinal cord. Additional evidence comes from rare cases of HIV-infected patients who also develop ALS. HIV infection has been associated with increasing levels of HML-2. When HIV-ALS patients were treated with antiretroviral drugs early in the course of the neurological manifestations, ALS symptoms could be reversed or slowed in a subset of patients. The activation of HML-2 found in the blood of some of these patients decreased following treatment with antiretroviral drugs. Besides ALS, activation of HML-2 and polymorphisms of HERV-K18 and K115 have been associated with schizophrenia. Thus, in some embodiments, the disease or disorder is a neurological disease or disorder selected from Multiple Sclerosis (MS), Amyotrophic Lateral Sclerosis (ALS), Autistic Spectrum45728747v169 disorder (ASD), Alzheimer’s Disease (AD), Hearing loss, Presbycusis, Increased cerumen production, Loss of visual acuity, Visual impairment, Loss of vestibular function, Sarcopenia, Chronic inflammation, Declining hormone levels, Impaired muscle, Mitochondrial function, Impaired muscle stem cell function, Muscle weakness, Immunosenescence, Decrease in urologic function, Cardiovascular disease, Chronic ischemic heart disease, Congestive heart failure, Arrhythmia, Atherosclerosis, Peripheral vascular disease, Hypertension, Rheumatoid arthritis, Juvenile rheumatoid arthritis, Osteoarthritis Osteoporosis, Short-term memory loss, Dementia, Progerias, Hutchinson–Gilford progeria syndrome (HGPS), Werner syndrome (WS), Cockayne, syndrome (CS), Bloom syndrome (BS), Ataxia-telangiectasia (A-T), Xeroderma pigmentosum (XP), Rothmund–Thomson syndrome (RTS), Centromere instability, Telomere instability, Facial anomalies syndrome (ICF), Myelodysplasia syndrome (MDS), Chronic lymphocytic leukemia (CLL), Acute myeloid leukemia (AML), Psoriatic arthritis, Diabetes mellitus, Multiple sclerosis, Encephalomyelitis, Myasthenia gravis, Systemic lupus erythematosus (SLE), Autoimmune thyroiditis, Atopic dermatitis, Eczematous dermatitis, Psoriasis, Sjogren’s Syndrome, Crohn’s disease, Aphthous ulcer, Iritis, Conjunctivitis, Keratoconjunctivitis, Ulcerative colitis, Inflammatory bowel disease (IBD), Cutaneous lupus, Erythematosus, Scleroderma, Vaginitis, Proctitis, Erythema nodosum leprosum, Autoimmune uveitis,, Allergic encephalomyelitis, Acute necrotizing, Hemorrhagic encephalopathy, Idiopathic bilateral progressive, Sensorineural hearing loss, Plastic anemia, Pure red cell anemia, Idiopathic thrombocytopenia, Polychondritis, Wegener’s granulomatosis, Chronic Active hepatitis, Stevens-Johnson syndrome, Idiopathic sprue, Lichen planus, Graves’ disease, Sarcoidosis, Primary biliary cirrhosis, Uveitis posterior, Interstitial lung fibrosis, Hashimoto’s thyroiditis, Autoimmune polyglandular syndrome, Insulin-dependent diabetes, Mellitus, Insulin-resistant diabetes mellitus, Immune-mediated infertility, Autoimmune Addison’s disease, Pemphigus vulgaris, Pemphigus foliaceus, Dermatitis herpetiformis, Autoimmune alopecia, Vitiligo, Autoimmune hemolytic anemia, Autoimmune thrombocytopenic purpura, Pernicious anemia, Guillain-Barre syndrome, Stiff-man syndrome, Acute rheumatic fever, Sympathetic ophthalmia, Goodpasture’s Syndrome, Systemic necrotizing vasculitis, Antiphospholipid syndrome or an allergy, Behcet’s disease, Severe combined immunodeficiency (SCID), Recombinase activating gene (RAG 1 / 2) deficiency, Adenosine deaminase (ADA) deficiency, Interleukin receptor common g chain (c) deficiency, Janus-associated kinase 3 (JAK3) deficiency and reticular dysgenesis, Primary T cell immunodeficiency, DiGeorge syndrome, Nude syndrome, T cell receptor deficiency, MHC class II deficiency, TAP-2 deficiency (MHC class I deficiency), ZAP70 tyrosine kinase deficiency and purine nucleotide phosphorylase (PNP) deficiency, antibody deficiencies, X-linked agammaglobulinemia (Bruton’s tyrosine kinase45728747v170 deficiency), Autosomal recessive agammaglobulinemia, Mu heavy chain deficiency, Surrogate light chain (g5 / 14.1) deficiency, Hyper-IgM syndrome: X-linked (CD40 ligand deficiency) or non-X- linked, Ig heavy chain gene deletion, IgA deficiency, Deficiency of IgG subclasses (with or without IgA deficiency), Common variable immunodeficiency (CVID), Antibody deficiency with normal immunoglobulins, Transient hypogammaglobulinemia of infancy, Interferon g receptor (IFNGR1, IFNGR2) deficiency, Interleukin 12 or interleukin 12 receptor deficiency, Immunodeficiency with thymoma, Wiskott-Aldrich syndrome (WAS protein deficiency), Ataxia telangiectasia (ATM deficiency), X-linkedlymphoproliferative syndrome (SH2D1 A / SAP deficiency), and Hyper IgE syndrome. D. HIV It is well established that HIV infection can increase HML-2 mRNA levels in PBMCs and the activation of certain HML-2 loci can be cell-type specific. Regarding the influence of HML-2 on HIV pathogenesis, it is not clear whether expression of HML-2 helps control HIV or if it contributes to its pathogenicity. HML-2 specific antibodies have been found in the blood of HIV- infected individuals at higher titers than uninfected. “Elite controller” individuals, who control HIV replication in the absence of treatment had higher titers of antibodies to HML-2 compared to their antiretroviral-treated counterparts, indicating that immune responses against HML-2 may correlate with HIV suppression. However, other groups could not find differences in HML-2 antibody levels between HIV patients and uninfected controls. Similarly, several groups have reported T cell responses to HML-2 in HIV-infected patients that are associated with better virologic control and higher T cell counts. Collectively, these findings point to a conclusion that HML-2 transcripts induced by HIV infection may be translated into viral proteins that can generate a humoral and / or cytotoxic T cell response. The presence of HML-2 proteins produced in response to HIV infection also introduces the possibility that these proteins modulate HIV replication. Given that HML-2 Env appears to bind to the surface of many different cell types, HIV virions “pseudotyped” with HML-2 Env could exhibit altered cellular tropism. Thus, in some embodiments, the disease or disorder to be detected, diagnosed, prognosed, and / or treated is HIV. V. Methods of Treatment Methods of treatment are also provided and can be used alone or in combination with other methods disclosed herein such as the disclosed methods of detection, diagnosis, prognosis, and treatment monitoring. The methods typically include administering a subject in need thereof an effective amount of a disclosed composition, e.g., a Kenv binder or CAR T cell formed therefrom,45728747v171 to treat the subject. This is particularly true where disease or condition is characterized by increased expression or presence of HERV-K and / or HERV-K Env protein (e.g., Env antigen). Additionally, or alternatively, particularly where increased live HERV-K virus has been detected, antivirals can be employed. HML-2 is consistently over-expressed in certain cancer types. Therefore, cell-mediated immune responses can be directed against HERV-K antigens to eliminate cancer cells. The recent success of immune-mediated therapies, particularly the engineering of a chimeric antigen receptor on the surface of T cells, makes this a promising approach (“Genetic Engineering of T Cells to Target HERV-K, an Ancient Retrovirus on Melanoma. Clin Cancer Res 21(14):3241–3251 (2015); Zhou et al., “Chimeric antigen receptor T cells targeting HERV-K inhibit breast cancer and its metastasis through downregulation of Ras,” Oncoimmunology, 4(11):e1047582 (2015)), each of which are specifically incorporate by reference herein in their entries. Similarly, HERV-K antigens can be targeted by antibody-conjugates, such as antibody drug conjugates. In cases where viral assembly occurs, the use of antiretroviral drugs to inhibit productive viral replication can also be considered for use alone or in combination with an immunotherapeutic approach. Studies show that some of the reverse transcriptase and integrase inhibitors developed against HIV are also effective against HML-2, although with lower efficacy An exemplary method involves treating a subject (e.g., a human) having a disease, disorder, or condition by administering to the subject an effective amount of a pharmaceutical composition including genetically-modified cells including a Kenv binder, optionally in a bispecific format and / or conjugated to an active agent such as drug (e.g., chemotherapeutic drug). In some embodiments, the methods administer cells (e.g., T cells) engineered to express recombinant Kenv-CAR to a subject (e.g., a human) having a disease, disorder, or condition in an amount effective to treat the disease, disorder, or condition. For example, in some embodiments, the methods treat a disease or disorder associated with an elevated expression or specific expression of HERV-K Env protein or an antigenic fragment thereof by administering to the subject an effective amount of a pharmaceutical composition including cells modified to express recombinant Kenv-CAR. For example, in some forms, the methods treat a subject having a disease, disorder, or condition by administering to the subject an effective amount of a pharmaceutical composition having a genetically modified cell, where the cell is modified by introducing to the cell: (i) a nucleic acid (e.g., vector or mRNA) encoding a Kenv-CAR; and (ii) causing the Kenv-CAR to be expressed by the cell. The cell can have been isolated from the subject having the disease, disorder, or condition, or from a healthy donor, prior to genetic modification.45728747v172 In some embodiments, the methods administer cells a Kenv binder optionally to a subject (e.g., a human) having a disease, disorder, or condition in an amount effective to treat the disease, disorder, or condition. In some embodiments, the molecule or antibody includes a drug conjugated thereto and / or has antibody-dependent cell-mediated cytotoxicity (ADCC) activity, or complement- dependent cytotoxicity activity (CDC), and / or is a bispecific engager optionally a T cell engager. A. Effective Amounts In some forms the methods administer the composition in an effective amount. The effective amount or therapeutically effective amount of a pharmaceutical compositions including modified cells, such as therapeutic T cells, or Kenv-binder such as an antibody-drug conjugate or bispecific antibody, can be a dosage sufficient to treat, inhibit, or alleviate one or more symptoms of a disease or disorder, such as a cancer, neurological disorder, autoimmune disease, or other condition mentioned herein, or to otherwise provide a desired pharmacologic and / or physiologic effect, for example, reducing, inhibiting, or reversing one or more of the underlying pathophysiological mechanisms underlying a disease or disorder, such as cancer. In some forms, when administration of the composition elicits an anti-cancer response, the amount administered can be expressed as the amount effective to achieve a desired anti-cancer effect in the recipient. For example, in some forms, the amount of the composition, is effective to inhibit the viability or proliferation of cancer cells in the recipient. In some forms, the amount of the pharmaceutical composition is effective to reduce the tumor burden in the recipient, or reduce the total number of cancer cells, and combinations thereof. In other forms, the amount of the composition is effective to reduce one or more symptoms or signs of cancer in a cancer patient, or signs of the other condition such as neurological disorder or an autoimmune disease in a patient having the condition. The effective amount of the composition can vary from subject to subject, depending on the species, age, weight and general condition of the subject, the severity of the disorder being treated, and its mode of administration. Thus, it is not possible to specify an exact amount for every pharmaceutical composition. However, an appropriate amount can be determined by one of ordinary skill in the art using only routine experimentation given the teachings herein. For example, effective dosages and schedules for administering the pharmaceutical compositions can be determined empirically, and making such determinations is within the skill in the art. In some forms, the dosage ranges for the administration of the compositions are those large enough to effect reduction in cancer cell proliferation or viability, or to reduce tumor burden for example. The dosage should not be so large as to cause adverse side effects, such as unwanted cross- reactions, anaphylactic reactions, and the like. Generally, the dosage will vary with the age,45728747v173 condition, and sex of the patient, route of administration, whether other drugs are included in the regimen, and the type, stage, and location of the disease to be treated. The dosage can be adjusted by the individual physician in the event of any counter-indications. It will also be appreciated that the effective dosage of the composition can increase or decrease over the course of a particular treatment. Changes in dosage can result and become apparent from the results of diagnostic assays. Dosage can vary, and can be administered in one or more dose administrations daily, for one or several days. Guidance can be found in the literature for appropriate dosages for given classes of pharmaceutical products. Optimal dosing schedules can be calculated from measurements of drug accumulation in the body of the subject or patient. Persons of ordinary skill can easily determine optimum dosages, dosing methodologies and repetition rates. Optimum dosages can vary depending on the relative potency of individual pharmaceutical compositions, and can generally be estimated based on EC50s found to be effective in in vitro and in vivo animal models. In a non-limiting example, a composition containing CAR cells described herein can be administered at a dosage of 104to 109cells / kg body weight, preferably 105to 107cells / kg body weight, including all integer values within those ranges. In some forms, patients can be treated by infusing a disclosed pharmaceutical composition containing CAR expressing cells (e.g., T cells) in the range of about 104to 1012or more cells per square meter of body surface (cells / m). In particular embodiments, for antibodies and other proteins, the dosage administered to a patient is typically 0.0001 mg / kg to 100 mg / kg of the patient’s body weight. Preferably, the dosage administered to a patient is between 0.0001 mg / kg and 20 mg / kg, 0.0001 mg / kg and 10 mg / kg, 0.0001 mg / kg and 5 mg / kg, 0.0001 and 2 mg / kg, 0.0001 and 1 mg / kg, 0.0001 mg / kg and 0.75 mg / kg, 0.0001 mg / kg and 0.5 mg / kg, 0.0001 mg / kg to 0.25 mg / kg, 0.0001 to 0.15 mg / kg, 0.0001 to 0.10 mg / kg, 0.001 to 0.5 mg / kg, 0.01 to 0.25 mg / kg or 0.01 to 0.10 mg / kg of the patient’s body weight. Generally, human antibodies have a longer half-life within the human body than antibodies from other species due to the immune response to the foreign polypeptides. Thus, lower dosages of human antibodies and less frequent administration is often possible. Further, the dosage and frequency of administration of antibodies or fragments thereof, or fusion proteins may be reduced by enhancing uptake and tissue penetration of the antibodies or fusion proteins by modifications such as, for example, lipidation. The administration can be repeated as often and as many times as the patient can tolerate until the desired response is achieved. Compositions can also be administered once or multiple times at these dosages. The cells can be administered by using infusion techniques that are commonly known in immunotherapy (see, e.g., Rosenberg et al., New Eng. J. of Med.319:1676, 1988).45728747v174 The optimal dosage and treatment regime for a particular patient can readily be determined by one skilled in the art of medicine by monitoring the patient for signs of disease and adjusting the treatment accordingly. In some forms, the unit dosage is in a unit dosage form for intravenous injection. In some forms, the unit dosage is in a unit dosage form for oral administration. In some forms, the unit dosage is in a unit dosage form for inhalation. In some forms, the unit dosage is in a unit dosage form for intra-tumoral injection. Treatment can be continued for an amount of time sufficient to achieve one or more desired therapeutic goals, for example, a reduction of the amount of cancer cells relative to the start of treatment, or complete absence of cancer cells in the recipient. Treatment can be continued for a desired period of time, and the progression of treatment can be monitored using any means known for monitoring the progression of anti-cancer treatment in a patient. In some forms, administration is carried out every day of treatment, or every week, or every fraction of a week. In some forms, treatment regimens are carried out over the course of up to two, three, four or five days, weeks, or months, or for up to 6 months, or for more than 6 months, for example, up to one year, two years, three years, or up to five years. The efficacy of administration of a particular dose of the pharmaceutical compositions according to the methods described herein can be determined by evaluating the aspects of the medical history, signs, symptoms, and objective laboratory tests that are known to be useful in evaluating the status of a subject in need for the treatment of cancer or other diseases and / or conditions. These signs, symptoms, and objective laboratory tests will vary, depending upon the particular disease or condition being treated or prevented, as will be known to any clinician who treats such patients or a researcher conducting experimentation in this field. For example, if, based on a comparison with an appropriate control group and / or knowledge of the normal progression of the disease in the general population or the particular individual: (1) a subject’s physical condition is shown to be improved (e.g., a tumor has partially or fully regressed), (2) the progression of the disease or condition is shown to be stabilized, or slowed, or reversed, or (3) the need for other medications for treating the disease or condition is lessened or obviated, then a particular treatment regimen will be considered efficacious. In some forms, efficacy is assessed as a measure of the reduction in tumor volume and / or tumor mass at a specific time point (e.g., 1-5 days, weeks, or months) following treatment. B. Modes of Administration In some embodiments the methods administer the composition in combination with a pharmaceutically acceptable carrier. The compositions described herein can be conveniently formulated into pharmaceutical compositions composed of one or more of the compounds in45728747v175 association with a pharmaceutically acceptable carrier. See, e.g., Remington's Pharmaceutical Sciences, latest edition, by E.W. Martin Mack Pub. Co., Easton, PA, which discloses typical carriers and conventional methods of preparing pharmaceutical compositions that can be used in conjunction with the preparation of formulations of the therapeutics described herein and which is incorporated by reference herein. These most typically would be standard carriers for administration of compositions to humans. In one aspect, for humans and non-humans, these include solutions such as sterile water, saline, and buffered solutions at physiological pH. Other therapeutics can be administered according to standard procedures used by those skilled in the art. The pharmaceutical compositions can include, but are not limited to, carriers, thickeners, diluents, buffers, preservatives, surface active agents and the like in addition to the therapeutic(s) of choice. Pharmaceutical compositions can be administered to the subject in a number of ways depending on whether local or systemic treatment is desired, and on the area to be treated. Thus, for example, a pharmaceutical composition including modified cells, such as therapeutic T cells, can be administered as an intravenous infusion, or directly injected into a specific site, for example, into or surrounding a tumor. Moreover, a pharmaceutical composition can be administered to a subject as an ophthalmic solution and / or ointment to the surface of the eye, vaginally, rectally, intranasally, orally, by inhalation, or parenterally, for example, by intradermal, subcutaneous, intramuscular, intraperitoneal, intrarectal, intraarterial, intralymphatic, intravenous, intrathecal and intratracheal routes. In some forms, the compositions are administered directly into a tumor or tissue, e.g., stereotactically. Parenteral administration, if used, is generally characterized by injection. Injectables can be prepared in conventional forms, either as liquid solutions or suspensions, solid forms suitable for solution or suspension in liquid prior to injection, or as emulsions. A more recently revised approach for parenteral administration involves use of a slow release or sustained release system such that a constant dosage is maintained. See, e.g., U.S. Patent No.3,610,795, which is incorporated by reference herein. Suitable parenteral administration routes include intravascular administration (e.g., intravenous bolus injection, intravenous infusion, intra-arterial bolus injection, intra-arterial infusion and catheter instillation into the vasculature); peri- and intra-tissue injection (e.g., intraocular injection, intra-retinal injection, or sub-retinal injection); subcutaneous injection or deposition including subcutaneous infusion (such as by osmotic pumps); direct application by a catheter or other placement device (e.g., an implant including a porous, non-porous, or gelatinous material).45728747v176 Preparations for parenteral administration include sterile aqueous or non-aqueous solutions, suspensions, and emulsions which can also contain buffers, diluents and other suitable additives. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, vegetable oils such as olive oil, and injectable organic esters such as ethyl oleate. Aqueous carriers include water, alcoholic / aqueous solutions, emulsions or suspensions, including saline and buffered media. Parenteral vehicles include sodium chloride solution, Ringer's dextrose, dextrose and sodium chloride, lactated Ringer's, or fixed oils. Intravenous vehicles include fluid and nutrient replenishers, electrolyte replenishers (such as those based on Ringer's dextrose), and the like. Preservatives and other additives can also be present such as, for example, antimicrobials, anti- oxidants, chelating agents, and inert gases and the like. Administration of the pharmaceutical compositions can be localized (i.e., to a particular region, physiological system, tissue, organ, or cell type) or systemic. It is to be understood that the disclosed method and compositions are not limited to specific synthetic methods, specific analytical techniques, or to particular reagents unless otherwise specified, and, as such, can vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. C. Combination Therapy In some embodiments the compositions are administered in combination with other therapeutic agents or treatment modalities. Any of the disclosed pharmaceutical compositions can be used alone, or in combination with other therapeutic agents or treatment modalities, for example, chemotherapy or stem-cell transplantation. As used herein, “combination” or “combined” refer to either concomitant, simultaneous, or sequential administration of the therapeutics. In some forms, the pharmaceutical compositions and other therapeutic agents are administered separately through the same route of administration. In other forms, the pharmaceutical compositions and other therapeutic agents are administered separately through different routes of administration. The combinations can be administered either concomitantly (e.g., as an admixture), separately but simultaneously (e.g., via separate intravenous lines into the same subject; one agent is given orally while the other agent is given by infusion or injection, etc.,), or sequentially (e.g., one agent is given first followed by the second). Examples of preferred additional therapeutic agents include other conventional therapies known in the art for treating the desired disease, disorder or condition. In some forms, the therapeutic agent is one or more other targeted therapies (e.g., a targeted cancer therapy) and / or immune-checkpoint blockage agents (e.g., anti-CTLA-4, anti-PD1, and / or anti-PDL1 agents such as antibodies).45728747v177 The compositions and methods described herein may be used as a first therapy, second therapy, third therapy, or combination therapy with other types of therapies known in the art, such as chemotherapy, surgery, radiation, gene therapy, immunotherapy, bone marrow transplantation, stem cell transplantation, targeted therapy, cryotherapy, ultrasound therapy, photodynamic therapy, radio-frequency ablation or the like, in an adjuvant setting or a neoadjuvant setting. The disclosed pharmaceutical compositions and / or other therapeutic agents, procedures or modalities can be administered during periods of active disease, or during a period of remission or less active disease. The pharmaceutical compositions can be administered before the additional treatment, concurrently with the treatment, post-treatment, or during remission of the disease or disorder. When administered in combination, the disclosed pharmaceutical compositions and the additional therapeutic agents (e.g., second or third agent), or all, can be administered in an amount or dose that is higher, lower or the same than the amount or dosage of each agent used individually, e.g., as a monotherapy. In certain forms, the administered amount or dosage of the disclosed pharmaceutical composition, the additional therapeutic agent (e.g., second or third agent), or all, is lower (e.g., at least 20%, at least 30%, at least 40%, or at least 50%) than the amount or dosage of each agent used individually, e.g., as a monotherapy (e.g., required to achieve the same therapeutic effect). In some embodiments, the methods administer one or more additional anti-cancer agents to a subject. In the context of cancer, targeted therapies are therapeutic agents that block the growth and spread of cancer by interfering with specific molecules ("molecular targets") that are involved in the growth, progression, and spread of cancer. Many different targeted therapies have been approved for use in cancer treatment. These therapies include hormone therapies, signal transduction inhibitors, gene expression modulators, apoptosis inducers, angiogenesis inhibitors, immunotherapies, and toxin delivery molecules. Numerous antineoplastic drugs can be used in combination with the disclosed pharmaceutical compositions. In some forms, the additional therapeutic agent is a chemotherapeutic or antineoplastic drug. The majority of chemotherapeutic drugs can be divided into alkylating agents, antimetabolites, anthracyclines, plant alkaloids, topoisomerase inhibitors, monoclonal antibodies, and other anti-tumor agents. be attached to solid supports, which are particularly useful for immunoassays or purification of the target antigen or of other molecules that are capable of binding to target antigen that has been immobilized to the support via binding to an antibody or antigen-binding fragment of the present invention. Such solid supports include, but are not limited to, glass, cellulose, polyacrylamide, nylon, polystyrene, polyvinyl chloride or polypropylene.45728747v178 Non-limiting examples of antineoplastic drugs that damage DNA or inhibit DNA repair include carboplatin, carmustine, chlorambucil, cisplatin, cyclophosphamide, dacarbazine, daunorubicin, doxorubicin, epirubicin, idarubicin, ifosfamide, lomustine, mechlorethamine, mitoxantrone, oxaliplatin, procarbazine, temozolomide, and valrubicin. In some embodiments, the antineoplastic drug is a histone deacetylase inhibitor, which suppresses DNA repair at the transcriptional level and disrupt chromatin structure. In some embodiments, the antineoplastic drug is a proteasome inhibitor, which suppresses DNA repair by disruption of ubiquitin metabolism in the cell. Ubiquitin is a signaling molecule that regulates DNA repair. In some embodiments, the antineoplastic drug is a kinase inhibitor, which suppresses DNA repair by altering DNA damage response signaling pathways. Additional antineoplastic drugs include, but are not limited to, alkylating agents (such as cisplatin, carboplatin, oxaliplatin, mechlorethamine, cyclophosphamide, chlorambucil, dacarbazine, lomustine, carmustine, procarbazine, chlorambucil and ifosfamide), antimetabolites (such as fluorouracil, gemcitabine, methotrexate, cytosine arabinoside, fludarabine, and floxuridine), some antimitotics, and vinca alkaloids such as vincristine, vinblastine, vinorelbine, and vindesine), anthracyclines (including doxorubicin, daunorubicin, valrubicin, idarubicin, and epirubicin, as well as actinomycins such as actinomycin D), cytotoxic antibiotics (including mitomycin, plicamycin, and bleomycin), and topoisomerase inhibitors (including camptothecins such as irinotecan and topotecan and derivatives of epipodophyllotoxins such as amsacrine, etoposide, etoposide phosphate, and teniposide) and cytoskeletal targeting drugs such as paclitaxel. In some embodiments the active agent is a radiosensitizer. Examples of known radiosensitizers include cisplatin, gemcitabine, 5-fluorouracil, pentoxifylline, vinorelbine, PARP inhibitors, histone deacetylase inhibitors, and proteasome inhibitors. The disclosed invention can be further understood by the following numbered paragraphs: 1. A molecule or antibody comprising an antigen binding region of an antibody comprising six complementarity determining regions (CDRs), that immunospecifically binds to a surface unit or a transmembrane unit of a Human endogenous retrovirus-K (HERV-K) Env protein, and optionally wherein the antibody immunospecifically binds to the amino acid sequence of SEQ ID NOS: 223 and / or 224. 2. A molecule or antibody comprising an antigen binding region of an antibody that immunospecifically binds to HERV-K Env protein, the antigen binding region comprising six complementarity determining regions (CDRs), wherein the CDRs include at least one CDR of the CDRs of anti-HERV-K Env antibody Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or a variant thereof with at least45728747v179 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; with all remaining CDRs independently selected from anti-HERV-K Env antibodies Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 3. The molecule or antibody of paragraphs 1 or 2, wherein the CDRs include three heavy chain variable region CDRs independently selected from the heavy chain variable region CDRs of anti-HERV-K Env antibodies Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto in combination with three light chain variable region CDRs independently selected from the light chain variable region CDRs of anti- HERV-K Env antibodies Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 4. The molecule or antibody of any one of paragraphs 1-3, wherein the CDRs include the three heavy chain variable region CDRs of anti-HERV-K Env antibody Kenv-1, Kenv-2, Kenv- 3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14,or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto in combination with the three light chain variable region CDRs for anti-HERV-K Env antibody Kenv- 1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv- 12, Kenv-13, Kenv-14 or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 5. The molecule or antibody of any one of paragraphs 1-4, wherein the six CDRs are (A) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-1; (B) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-2; (C) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-3; (D) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-4; (E) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-5; (F) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-6;45728747v180 (G) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-7; (H) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-8; (I) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-9; (J) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-10; (K) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-11; (L) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-12; (M) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-13; or (N) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-14. 6. The molecule or antibody of any one of paragraphs 1-5, wherein the six CDRs are oriented and in the same orientation as in the anti-HERV-K ENV antibody from which they were selected. 7. The molecule or antibody of any one of paragraphs 1-6, wherein the heavy chain variable region and light chain variable regions of antibody Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, and Kenv-14, are the heavy chain variable regions of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14 according to Tables 2 or 3 or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto., and the light chain variable regions of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14 according to Tables 7 and 8 or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 8. The molecule or antibody of any one of paragraphs 1-7, wherein the six CDRs is are the CDRs according to:45728747v181 Table 1: Heavy Chain Variable Region CDR Sequences SEQ SEQ SEQ Binder ID ID ID 38131822273236414449135459 Table 6: Light Chain Variable CDR Sequences SEQ SEQ SEQ 5050494 8 Kenv-9 QSLVHSNGNTY 37 KVS - SQSTHVPLT 38 Kenv-10 QEISGY 45 AAS - LQYASYPFT 46 1561 thereto. 9. A molecule or antibody comprising a heavy chain variable region comprising three CDRs and a light chain variable region comprising three CDRs, wherein (A) the three heavy chain variable region CDRs comprise GFTFNTYA (SEQ ID NO:1), IRSKSNYYAT (SEQ ID NO:2), VRDYGAY (SEQ ID NO:3), respectively, and the three light chain variable region CDRs comprise QDINSF (SE QID NO:4), RAN, LQYYEFLPT (SEQ ID NO:5) respectively; (B) the three heavy chain variable region CDRs comprise GYSIASGYS (SEQ ID NO:6), IHFSGNT (SEQ ID NO:7), ARGARNGNPYWYLDV (SEQ ID NO:8), respectively, and the three light chain variable region CDRs comprise QSISDY (SEQ ID NO:9), YAS, QNGRTFPFT (SEQ ID NO:10), respectively; (C) the three heavy chain variable region CDRs comprise GFSLSTSNMG (SEQ ID NO:11), ILWNDSK (SEQ ID NO:12), ARIARYHYAGSSWYFDV (SEQ ID NO:13), respectively, and the three light chain variable region CDRs comprise QGISNY (SEQ ID NO:14), YTS, QQYSKLPYT (SEQ ID NO:15), respectively; (D) the three heavy chain variable region CDRs comprise GYSITSDYA (SEQ ID NO:16), ISYSGST (SEQ ID NO:17), ARSVILGAWFAY (SEQ ID NO:18), respectively, and the three light chain variable region CDRs comprise SSITY (SEQ ID NO:19), LTS, QQWSSNPLT (SEQ ID NO:20), respectively; (E) the three heavy chain variable region CDRs comprise GYSITSDYA (SEQ ID NO:16), ISYSGTT (SEQ ID NO:21), ARLGFW (SEQ ID NO:22), respectively, and the three light chain variable region CDRs comprise ESVDNYGISF (SEQ ID NO:23), AAS, QQSKEIPYT (SEQ ID NO:24), respectively; (F) the three heavy chain variable region CDRs comprise GYTFTNYG (SEQ ID NO:25), INTYTGEP (SEQ ID NO:26), AKYYDGYYGWYFDV (SEQ ID NO:27), respectively, and the three light chain variable region CDRs comprise ESVDSYGNSF (SEQ ID NO:28), RAS, QQSYEDPYT (SEQ ID NO:29), respectively;45728747v183 (G) the three heavy chain variable region CDRs comprise GFSFTVYG (SEQ ID NO:30), IWGDGRT (SEQ ID NO:31), ARRNGYYAMDY (SEQ ID NO:32), respectively, and the three light chain variable region CDRs comprise ENIYSN (SEQ ID NO:33), AAT, QHFWGTPYT (SEQ ID NO:34), respectively; (H) the three heavy chain variable region CDRs comprise GFSXSTSNMG (SEQ ID NO:35), ILWNDSK (SEQ ID NO:12), ARIARYHYACISFYFEV (SEQ ID NO:36), respectively, and the three light chain variable region CDRs comprise QSLVHSNGNTY (SEQ ID NO:37), KVS, SQSTHVPLT (SEQ ID NO:38), respectively; (I) the three heavy chain variable region CDRs comprise GYTFTNYY 39, INPSNGDT 40, TRFRSPFYYAMDY 41, respectively, and the three light chain variable region CDRs comprise QSLVHSNGNTY 37, KVS, SQSTHVPLT 38, respectively; (J) the three heavy chain variable region CDRs comprise GYTFTEYI (SEQ ID NO:42), VNPNNGGP (SEQ ID NO:43), TKGDY (SEQ ID NO:44), respectively, and the three light chain variable region CDRs comprise QEISGY (SEQ ID NO:45), AAS, LQYASYPFT (SEQ ID NO:46), respectively; (K) the three heavy chain variable region CDRs comprise GYSFTDYF (SEQ ID NO:47), INPYNGDT (SEQ ID NO:48), ARNGYYRYYFDY (SEQ ID NO:49), respectively, and the three light chain variable region CDRs comprise SSVNY (SEQ ID NO:50), EIS, QQWNYPLT (SEQ ID NO:51), respectively; (L) the three heavy chain variable region CDRs comprise GYTFTEYT (SEQ ID NO:52), FIPSNGNT (SEQ ID NO:53), TRRPYYYGSGYWYFDF (SEQ ID NO:54), respectively, and the three light chain variable region CDRs comprise QDVRTS (SEQ ID NO:55), STS, QQHYSTPYT (SEQ ID NO:56), respectively; (M) the three heavy chain variable region CDRs comprise GYSIPSDYA (SEQ ID NO:57), ISSSGST (SEQ ID NO:58), ASYDNDNVY (SEQ ID NO:59), respectively, and the three light chain variable region CDRs comprise QSLLNSRTRKNY (SEQ ID NO:60), WAS, KQSYNLWT (SEQ ID NO:61), respectively. 10. The molecule or antibody of any one of paragraphs 1-9, wherein the antigen binding region comprises the heavy chain variable region of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 11. The molecule or antibody of any one of paragraphs 1-10, wherein the antigen binding region comprises the light chain variable region of Kenv-1, Kenv-2, Kenv-3, Kenv-4,45728747v184 Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 12. The molecule or antibody of any one of paragraphs 1-11, wherein the antigen binding region comprises the heavy chain variable region and light chain variable region of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 13. The molecule or antibody of any one of paragraphs 1-12, wherein the antigen binding region comprises the heavy chain variable region and / or light chain variable region according to Table 4 and / or Table 9, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 14. The molecule or antibody of any one of paragraphs 1-13, wherein the molecule or antibody comprises the heavy chain V-D-J regions of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 15. The molecule or antibody of any one of paragraphs 1-14, wherein the molecule or antibody comprises the light chain V-J regions of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv- 6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 16. The molecule or antibody of any one of paragraphs 1-15, wherein the antigen binding region comprises the heavy chain V-D-J regions and light chain V-J regions of Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto. 17. The molecule or antibody of any one of paragraphs 15-16, wherein the antigen binding region comprises the heavy chain variable V-D-J and / or light chain variable V-J according to Table 5 and / or Table 10, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto, optionally wherein the molecule or antibody is antibody Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-6, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14. 18. The molecule or antibody of any one of paragraphs 1-17, wherein the molecule or antibody is an antibody. 19. The molecule or antibody of paragraph 18, wherein the antibody is an intact antibody and functional antibody fragment or fusion protein.45728747v185 20. The molecule or antibody of paragraph 19, wherein the functional fragment or fusion protein is selected from Fab fragments, F(ab')2 fragments, Fab' fragments, Fv fragments, recombinant IgG (rlgG) fragments, single chain antibody fragments optionally single chain variable fragments (scFv), and single region antibodies optionally selected from sdAb, sdFv, and nanobody fragments. 21. The molecule or antibody of any one of paragraphs 18-20, wherein the antibody is selected from intrabodies, peptibodies, chimeric antibodies, fully human antibodies, humanized antibodies, and heteroconjugate antibodies, and multispecific antibodies optionally selected bispecific antibodies, diabodies, triabodies, tetrabodies, tandem di-scFv, and tandem tri-scFv. 22. The molecule or antibody of any one of paragraphs 18-21 wherein the antibody is an IgM, IgE, IgA, IgD, or IgG optionally an IgG1, IgG2, IgG3, or IgG4. 23. The molecule or antibody of any one of paragraphs 1-22, wherein the molecule or antibody is detectably labeled or comprises a conjugated toxin, drug, receptor, enzyme, receptor ligand. 24. A fusion protein comprising the molecule or antibody of any one of paragraphs 1-23 and heterologous amino acid sequence. 25. A chimeric antigen receptor (CAR) polypeptide comprising the molecule or antibody of any one of paragraphs 1-23. 26. The chimeric antigen receptor of paragraph 25 comprising an extracellular antigen binding region, a spacer region, a transmembrane region, and intracellular signaling region. 27. The chimeric antigen receptor of paragraph 26 comprising a co-stimulatory domain. 28. A nucleic acid or acids encoding the molecule or antibody of any one of paragraphs 1-23, fusion protein of paragraph 24, or CAR of any one of paragraphs 25-27. 29. The nucleic acid or acids of paragraph 28 comprising an expression control sequence operably linked thereto, optionally wherein the expression control sequence comprises a promoter. 30. A vector comprising the nucleic acid or acids of paragraphs 28 or 29. 31. A host cell comprising the molecule or antibody of any one of paragraphs 1-23, fusion protein of paragraphs 24, CAR of any one of paragraphs 25-27, nucleic acid or acids(s) of paragraphs 28-29, or vector of paragraphs 30. 32. A CAR immune cell comprising the CAR of any one of paragraphs 25-27, optionally wherein the immune cell is a T cell. 33. A pharmaceutical composition comprising the CAR immune cells of paragraph 32, or the molecule or antibody of any one of paragraphs 1-23 optionally wherein the molecule or antibody comprises a drug conjugated thereto and / or has antibody-dependent cell-mediated45728747v186 cytotoxicity (ADCC) activity, or complement-dependent cytotoxicity activity (CDC), and / or is a bispecific immune cell engager. 34. A method of treating a subject in need thereof comprising administering the subject an effective amount of pharmaceutical composition of paragraph 33. 35. The method of paragraph 34, wherein the subject has a disease or disorder caused by or characterized by increased presence of HERV-K Env protein or a fragment thereof. 36. The method of paragraphs 34 or 35, wherein the subject has a cancer, a neurological disorder, an immunodeficiency, an autoimmune disease, or HIV. 37. The method of paragraph 36, wherein the subject has cancer and HERV-K Env protein or fragment thereof is an antigen of the cancer cells. 38. A method of detecting HERV-K Env protein or fragment thereof comprising contacting a biological sample with one or more molecules or antibodies of any one of paragraphs 1-23, and detecting binding between the molecule(s) or antibod(ies) and the HERV-K Env protein or fragment thereof. 39. The method of paragraph 38 further comprising determining that the sample includes increased HERV-K Env protein or fragment thereof if the level of detected binding is higher in the biological sample than in a control. 40. The method of paragraphs 38 or 39, wherein binding is detected by an immunoassay, immunohistochemistry, Western blotting, surface plasmon resonance, flow cytometry (FACS) analysis, or a biochip. 41. The method of paragraph 40, wherein the immunoassay is selected from an enzyme immunoassay (EIA), radioimmunoassay (RIA), fluoroimmunoassay (FIA), chemiluminescent immunoassay (CLIA) and counting immunoassay (CIA), homogeneous enzyme-multiplied immunoassays (“EMIT”), apoenzyme reactivation immunoassay (“ARIS”), dipstick immunoassays, or immuno-chromatography assays. 42. The method of any one of paragraphs 38-41, wherein the biological sample is cells or a cell lysate or a fraction thereof or a fluid optionally blood, saliva, or urine. 43. The method of paragraph 42, wherein the cells or cell lysate or fraction thereof are derived from a biopsy from a subject. 44. The method of paragraph 43, wherein the biopsy contains or is suspected of containing tumor cells. 45. The method of paragraphs 44, wherein the biopsy is a tumor biopsy.45728747v187 46. A method of diagnosing a subject with a HERV-K Env protein-related disease or disorder comprising detecting HERV-K Env protein or fragment thereof according to the method of any one of paragraphs 38-45. 47. The method of paragraph 46, wherein the HERV-K Env protein-related disease or disorder is a cancer, a neurological disorder, an immunodeficiency, an autoimmune disease, or HIV. 48. The method of any one of paragraphs 38-47 further comprising treating the subject. 49. The method of paragraph 48, wherein the treatment comprises a therapy effective for treating a HERV-K Env protein-related diseases and disorders. 50. The method of paragraphs 48 or 49, wherein the treatment comprises administering the subject an effective amount of the pharmaceutical composition of paragraph 33 and / or an antiviral. 51. The method of any one of paragraphs 34-50, wherein the subject has disease or disorder selected from Breast cancer, Cervical cancer, Colon cancer, Head and neck cancer, Hepatocellular cancer, Kidney cancer, Lung cancer, Lymphoma, Melanoma, Ovarian cancer, Pancreatic cancer, Prostate cancer, Sarcoma, Seminoma, Teratocarcinoma, Urothelial cancer, Endometrial cancer, Germ Cell Tumors, Multiple Sclerosis (MS), Rheumatoid arthritis (RA), Amyotrophic Lateral Sclerosis (ALS), Autistic Spectrum disorder (ASD), Alzheimer’s Disease (AD), Hearing loss, Presbycusis, Increased cerumen production, Loss of visual acuity, Visual impairment, Loss of vestibular function, Sarcopenia, Chronic inflammation, Declining hormone levels, Impaired muscle, Mitochondrial function, Impaired muscle stem cell function, Muscle weakness, Immunosenescence, Decrease in urologic function, Cardiovascular disease, Chronic ischemic heart disease, Congestive heart failure, Arrhythmia, Atherosclerosis, Peripheral vascular disease, Hypertension, Rheumatoid arthritis, Juvenile rheumatoid arthritis, Osteoarthritis Osteoporosis, Short-term memory loss, Dementia, Progerias, Hutchinson–Gilford progeria syndrome (HGPS), Werner syndrome (WS), Cockayne, syndrome (CS), Bloom syndrome (BS), Ataxia-telangiectasia (A-T), Xeroderma pigmentosum (XP), Rothmund–Thomson syndrome (RTS), Centromere instability, Telomere instability, Facial anomalies syndrome (ICF), Myelodysplasia syndrome (MDS), Chronic lymphocytic leukemia (CLL), Acute myeloid leukemia (AML), Psoriatic arthritis, Diabetes mellitus, Multiple sclerosis, Encephalomyelitis, Myasthenia gravis, Systemic lupus erythematosus (SLE), Autoimmune thyroiditis, Atopic dermatitis, Eczematous dermatitis, Psoriasis, Sjogren’s Syndrome, Crohn’s disease, Aphthous ulcer, Iritis, Conjunctivitis, Keratoconjunctivitis, Ulcerative colitis, Inflammatory bowel disease (IBD), Cutaneous lupus, Erythematosus, Scleroderma, Vaginitis, Proctitis, Erythema nodosum leprosum, Autoimmune uveitis,, Allergic encephalomyelitis, Acute necrotizing, Hemorrhagic encephalopathy, Idiopathic45728747v188 bilateral progressive, Sensorineural hearing loss, Plastic anemia, Pure red cell anemia, Idiopathic thrombocytopenia, Polychondritis, Wegener’s granulomatosis, Chronic Active hepatitis, Stevens- Johnson syndrome, Idiopathic sprue, Lichen planus, Graves’ disease, Sarcoidosis, Primary biliary cirrhosis, Uveitis posterior, Interstitial lung fibrosis, Hashimoto’s thyroiditis, Autoimmune polyglandular syndrome, Insulin-dependent diabetes, Mellitus, Insulin-resistant diabetes mellitus, Immune-mediated infertility, Autoimmune Addison’s disease, Pemphigus vulgaris, Pemphigus foliaceus, Dermatitis herpetiformis, Autoimmune alopecia, Vitiligo, Autoimmune hemolytic anemia, Autoimmune thrombocytopenic purpura, Pernicious anemia, Guillain-Barre syndrome, Stiff-man syndrome, Acute rheumatic fever, Sympathetic ophthalmia, Goodpasture’s Syndrome, Systemic necrotizing vasculitis, Antiphospholipid syndrome or an allergy, Behcet’s disease, Severe combined immunodeficiency (SCID), Recombinase activating gene (RAG 1 / 2) deficiency, Adenosine deaminase (ADA) deficiency, Interleukin receptor common g chain (c) deficiency, Janus-associated kinase 3 (JAK3) deficiency and reticular dysgenesis, Primary T cell immunodeficiency, DiGeorge syndrome, Nude syndrome, T cell receptor deficiency, MHC class II deficiency, TAP-2 deficiency (MHC class I deficiency), ZAP70 tyrosine kinase deficiency and purine nucleotide phosphorylase (PNP) deficiency, antibody deficiencies, X-linked agammaglobulinemia (Bruton’s tyrosine kinase deficiency), Autosomal recessive agammaglobulinemia, Mu heavy chain deficiency, Surrogate light chain (g5 / 14.1) deficiency, Hyper-IgM syndrome: X-linked (CD40 ligand deficiency) or non-X-linked, Ig heavy chain gene deletion, IgA deficiency, Deficiency of IgG subclasses (with or without IgA deficiency), Common variable immunodeficiency (CVID), Antibody deficiency with normal immunoglobulins, Transient hypogammaglobulinemia of infancy, Interferon g receptor (IFNGR1, IFNGR2) deficiency, Interleukin 12 or interleukin 12 receptor deficiency, Immunodeficiency with thymoma, Wiskott- Aldrich syndrome (WAS protein deficiency), Ataxia telangiectasia (ATM deficiency), X- linkedlymphoproliferative syndrome (SH2D1 A / SAP deficiency), or Hyper IgE syndrome. Examples Example 1: Development of HERV-K Envelope binding proteins Materials and Methods To generate HERV-K Envelope protein mAbs, mice were immunized and boosted with soluble env (SEQ ID NO:224) produced in Drosophila melanogaster insect cells. Plasma B-cells were isolated using the Berkeley Lights Beacon Platform. B-cells were assayed for antibody production and reactivity to env antigen on chip.45728747v189 cDNA synthesis was performed on reactive cells and then exported. Antibody variable sequences were then amplified using multiple rounds of nested PCRs and cloned into IgG backbones. These were then expressed and screened for reactivity using ELISAs. Results The mAbs described here, named Kenv-1 through Kenv-14, were identified as positively reactive against antigen. Sequences were further confirmed and the 14 individual mAbs were expressed in larger scale then purified. Annotated sequences of the variable regions of both heavy and light chains of each antibody are provided in the Tables 1-3 and 6-8 above, and in Tables 4-5 and 9-10 below. Table 4: Heavy Chain Construction Overview Binder ID V GENE and allele J GENE and allele D GENE and allele F F F F F F F F F F 1 F F F 45728747v190 Table 5: Heavy Chain Framework Sequences SE SEQ SEQ Q SEQ : 1929 394855 63 45728747v191 QVQLK ESGPG DYNSALKSRL 71797191 993911 45728747v192 DVQLQ ESGPG SYNPSLKSRI 17 Binder ID V-GENE and allele J-GENE and allele Table 10: Light Chain Framework Sequences SEQ SEQ SEQ SEQ J- SEQ SEQ : 25 45728747v193 ITCK SLEY AS EDMG 352553 45728747v194 NQGS GVPA 2525 2553 45728747v195 NRFS GVPD 5335 5325 45728747v196 YRYT GVPD 2525 The lack of research reagents for studying HERV-K Env and its subunits hindered the initial study of the protein. The commercially available monoclonal antibodies (mAbs) HERM 1811-5 and HERM 1821-5 (Austral Biologicals) were elicited by immunization with E. coli-produced glycoproteins. They recognize linear epitopes and therefore cannot discern properly folded from misfolded protein and were not suitable for structural studies of the HERV-K Env. In this study, BALB / c mice were immunized with the wild-type Env ectodomain (EnvEcto) produced in Drosophila S2 insect cells. Using the Bruker Beacon antibody discovery platform, followed by biochemical characterization, a subset of ten monoclonal antibodies from the panel that would together cover the range of conformational (pre- and post-fusion) and subunit (SU and TM) specificities were selected (Tables 11 and 12). Antibodies on ELISA coated with either purified wild-type (WT) unstabilized EnvEcto, which contains both SU and TMEcto in a mixture of pre- and post-fusion conformations, or with post-fusion TMEcto alone. Six of the mAbs were bound to both WT EnvEcto and post-fusion TMEcto while the remaining four were only bound to WT EnvEcto. To determine whether these mAbs recognize linear or conformational epitopes, we denatured WT EnvEctoor post-fusion TMEctoat 95°C with DTT for 10 minutes and screened the mAbs using ELISA again. Six mAbs bound to either denatured EnvEcto or post-fusion TMEcto, revealing that they likely bind to linearized epitopes. Six mAbs bound to either denatured EnvEctoor post-fusion45728747v197 TMEcto, revealing that they likely bind to linearized epitopes. Kenv-6 only binds WT Env, and fails to bind denatured or postfusion EnvEcto, indicating it is pre-fusion specific and recognizes a conformational epitope. In contrast, while Kenv-4 binds more strongly to post- fusion TMEcto. Western blot analysis using WT EnvEcto was performed with each mAb to further confirm subunit and conformational specificities. Two mAbs, Kenv-2 and Kenv-3, did not bind to fully denatured protein but did recognize Env in western blots. Binding characterization is shown in Tables 11 and 12 below, and in Figures 1. ELISA Data using soluble env as the antigen is shown in Figure 2. Representative negative-stain electron microscopy (Kenv-6) and 3D ab-initio reconstructions (Kenv-6 and Kenv-4), are shown in Figures 3A-3B. Table 11: Antibody Subunit Specificity and Epitope Confirmation 45728747v198 Table 12: Anti-Env mAbs. Antibodies were screened for surface protein (SU) or transmembrane protein subunit (TM) binding using ELISA. Epitope type was determined using ELISAs in combination with western blots. * = presumed linear based on western blotting results. seven are TM specific (Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-7, Kenv-12). Two antibodies, Kenv-6 and Kenv-4, bind to conformational epitopes on the properly folded SU and post-fusion TM, respectively (Table 12). With these monoclonal antibodies, each Env subunit could be reliably detected when engineering Env to stabilize the pre-fusion conformation. Further, the two conformational mAbs facilitated the structure determination of Env in pre- and post-fusion states. Experiments were also designed to test if these mAbs would recognize HERV-K Env expressed in human patient samples as well as recombinant protein. Five of these antibodies, Kenv- 1, Kenv-2, Kenv-3, Kenv-6, and Kenv-7 were found to stain isolated neutrophils from both SLE and RA patients (Figure 1), which have been previously reported to express Envs from two HERV- K loci: HERV-K102 and K108. In contrast, these mAbs did not have any level of detectable antibody binding to neutrophils from healthy patients. References 1. J. Paces, A. Pavlícek, V. Paces, HERVd: database of human endogenous retroviruses. Nucleic Acids Res.30, 205–206 (2002). 2. B. Xue, L. A. Sechi, D. J. 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Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.45728747v1108

Claims

We claim:

1. A molecule or antibody comprising an antigen binding region of an antibody comprising six complementarity determining regions (CDRs), that immunospecifically binds to a surface unit or a transmembrane unit of a Human endogenous retrovirus-K (HERV-K) Env protein, and optionally wherein the antibody immunospecifically binds to the amino acid sequence of SEQ ID NOS: 223 and / or 224.

2. The molecule or antibody, wherein the CDRs include at least one CDR of the CDRs of anti-HERV-K Env antibody Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv- 8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto; with all remaining CDRs independently selected from anti-HERV-K Env antibodies Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

3. The molecule or antibody of claim 1, wherein the CDRs include three heavy chain variable region CDRs independently selected from the heavy chain variable region CDRs of anti- HERV-K Env antibodies Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto in combination with three light chain variable region CDRs independently selected from the light chain variable region CDRs of anti-HERV-K Env antibodies Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, and variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

4. The molecule or antibody of claim 1, wherein the CDRs include the three heavy chain variable region CDRs of anti-HERV-K Env antibody Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto in combination with the three light chain variable region CDRs for anti-HERV-K Env antibody Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv- 13, Kenv-14 or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

5. The molecule or antibody of claim 1, wherein the six CDRs are (F) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-6;45728747v1109(A) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-1; (B) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-2; (C) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-3; (D) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-4; (E) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-5; (G) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-7; (H) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-8; (I) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-9; (J) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-10; (K) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-11; (L) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-12; (M) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-13; or (N) the three heavy chain variable region CDRs and the three light chain variable region CDRs of anti-HERV-K ENV antibody Kenv-14.

6. The molecule or antibody of claim 5, wherein the six CDRs are oriented and in the same orientation as in the anti-HERV-K ENV antibody from which they were selected.

7. The molecule or antibody of claim 6, wherein the heavy chain variable region and light chain variable regions of antibody Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv- 7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, and Kenv-14, are the heavy chain variable regions of Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14 according to Tables 2 or 3 or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto, and the light chain variable45728747v1110regions of Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14 according to Tables 7 and 8 or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

8. The molecule or antibody of claim 7, wherein the six CDRs is are the CDRs according to: Heavy Chain Variable Region CDR Sequences SEQ SEQ SEQ Binder ID ID ID 2738131822323641444913545945728747v1111Light Chain Variable CDR Sequences SEQ SEQ SEQ Binder ID CDR2- ID ID 95050448861 5 61or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

9. The molecule or antibody of claim 8, wherein (F) the three heavy chain variable region CDRs comprise GYTFTNYG (SEQ ID NO:25), INTYTGEP (SEQ ID NO:26), AKYYDGYYGWYFDV (SEQ ID NO:27), respectively, and the three light chain variable region CDRs comprise ESVDSYGNSF (SEQ ID NO:28), RAS, QQSYEDPYT (SEQ ID NO:29), respectively; (A) the three heavy chain variable region CDRs comprise GFTFNTYA (SEQ ID NO:1), IRSKSNYYAT (SEQ ID NO:2), VRDYGAY (SEQ ID NO:3), respectively, and the three light chain variable region CDRs comprise QDINSF (SE QID NO:4), RAN, LQYYEFLPT (SEQ ID NO:5) respectively; (B) the three heavy chain variable region CDRs comprise GYSIASGYS (SEQ ID NO:6), IHFSGNT (SEQ ID NO:7), ARGARNGNPYWYLDV (SEQ ID NO:8), respectively, and the three light chain variable region CDRs comprise QSISDY (SEQ ID NO:9), YAS, QNGRTFPFT (SEQ ID NO:10), respectively;45728747v1112(C) the three heavy chain variable region CDRs comprise GFSLSTSNMG (SEQ ID NO:11), ILWNDSK (SEQ ID NO:12), ARIARYHYAGSSWYFDV (SEQ ID NO:13), respectively, and the three light chain variable region CDRs comprise QGISNY (SEQ ID NO:14), YTS, QQYSKLPYT (SEQ ID NO:15), respectively; (D) the three heavy chain variable region CDRs comprise GYSITSDYA (SEQ ID NO:16), ISYSGST (SEQ ID NO:17), ARSVILGAWFAY (SEQ ID NO:18), respectively, and the three light chain variable region CDRs comprise SSITY (SEQ ID NO:19), LTS, QQWSSNPLT (SEQ ID NO:20), respectively; (E) the three heavy chain variable region CDRs comprise GYSITSDYA (SEQ ID NO:16), ISYSGTT (SEQ ID NO:21), ARLGFW (SEQ ID NO:22), respectively, and the three light chain variable region CDRs comprise ESVDNYGISF (SEQ ID NO:23), AAS, QQSKEIPYT (SEQ ID NO:24), respectively; (G) the three heavy chain variable region CDRs comprise GFSFTVYG (SEQ ID NO:30), IWGDGRT (SEQ ID NO:31), ARRNGYYAMDY (SEQ ID NO:32), respectively, and the three light chain variable region CDRs comprise ENIYSN (SEQ ID NO:33), AAT, QHFWGTPYT (SEQ ID NO:34), respectively; (H) the three heavy chain variable region CDRs comprise GFSXSTSNMG (SEQ ID NO:35), ILWNDSK (SEQ ID NO:12), ARIARYHYACISFYFEV (SEQ ID NO:36), respectively, and the three light chain variable region CDRs comprise QSLVHSNGNTY (SEQ ID NO:37), KVS, SQSTHVPLT (SEQ ID NO:38), respectively; (I) the three heavy chain variable region CDRs comprise GYTFTNYY 39, INPSNGDT 40, TRFRSPFYYAMDY 41, respectively, and the three light chain variable region CDRs comprise QSLVHSNGNTY 37, KVS, SQSTHVPLT 38, respectively; (J) the three heavy chain variable region CDRs comprise GYTFTEYI (SEQ ID NO:42), VNPNNGGP (SEQ ID NO:43), TKGDY (SEQ ID NO:44), respectively, and the three light chain variable region CDRs comprise QEISGY (SEQ ID NO:45), AAS, LQYASYPFT (SEQ ID NO:46), respectively; (K) the three heavy chain variable region CDRs comprise GYSFTDYF (SEQ ID NO:47), INPYNGDT (SEQ ID NO:48), ARNGYYRYYFDY (SEQ ID NO:49), respectively, and the three light chain variable region CDRs comprise SSVNY (SEQ ID NO:50), EIS, QQWNYPLT (SEQ ID NO:51), respectively; (L) the three heavy chain variable region CDRs comprise GYTFTEYT (SEQ ID NO:52), FIPSNGNT (SEQ ID NO:53), TRRPYYYGSGYWYFDF (SEQ ID NO:54), respectively, and the45728747v1113three light chain variable region CDRs comprise QDVRTS (SEQ ID NO:55), STS, QQHYSTPYT (SEQ ID NO:56), respectively; (M) the three heavy chain variable region CDRs comprise GYSIPSDYA (SEQ ID NO:57), ISSSGST (SEQ ID NO:58), ASYDNDNVY (SEQ ID NO:59), respectively, and the three light chain variable region CDRs comprise QSLLNSRTRKNY (SEQ ID NO:60), WAS, KQSYNLWT (SEQ ID NO:61), respectively.

10. The molecule or antibody of claim 9, wherein the antigen binding region comprises the heavy chain variable region of Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

11. The molecule or antibody of claim 10, wherein the antigen binding region comprises the light chain variable region of Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or a variant thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

12. The molecule or antibody of claim 11, wherein the antigen binding region comprises the heavy chain variable region and light chain variable region of Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

13. The molecule or antibody of claim 12, wherein the antigen binding region comprises the heavy chain variable region and / or light chain variable region according to Table 4 and / or Table 9, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

14. The molecule or antibody of claim 13, wherein the molecule or antibody comprises the heavy chain V-D-J regions of Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

15. The molecule or antibody of claim 14, wherein the molecule or antibody comprises the light chain V-J regions of Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.

16. The molecule or antibody of claim 15, wherein the antigen binding region comprises the heavy chain V-D-J regions and light chain V-J regions of Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, Kenv-14, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto.45728747v111417. The molecule or antibody of claim 15, wherein the antigen binding region comprises the heavy chain variable V-D-J and / or light chain variable V-J according to Table 5 and / or Table 10, or variants thereof with at least 60, 70, 75, 80, 85, 90, or 95% sequence identity thereto, optionally wherein the molecule or antibody is antibody Kenv-6, Kenv-1, Kenv-2, Kenv-3, Kenv-4, Kenv-5, Kenv-7, Kenv-8, Kenv-9, Kenv-10, Kenv-11, Kenv-12, Kenv-13, or Kenv-14.

18. The molecule or antibody of any one of claims 1-17, wherein the molecule or antibody is an antibody.

19. The molecule or antibody of claim 18, wherein the antibody is an intact antibody and functional antibody fragment or fusion protein.

20. The molecule or antibody of claim 19, wherein the functional fragment or fusion protein is selected from Fab fragments, F(ab')2 fragments, Fab' fragments, Fv fragments, recombinant IgG (rlgG) fragments, single chain antibody fragments optionally single chain variable fragments (scFv), and single region antibodies optionally selected from sdAb, sdFv, and nanobody fragments.

21. The molecule or antibody of claim 18, wherein the antibody is selected from intrabodies, peptibodies, chimeric antibodies, fully human antibodies, humanized antibodies, and heteroconjugate antibodies, and multispecific antibodies optionally selected bispecific antibodies, diabodies, triabodies, tetrabodies, tandem di-scFv, and tandem tri-scFv.

22. The molecule or antibody of claim 18 wherein the antibody is an IgM, IgE, IgA, IgD, or IgG optionally an IgG1, IgG2, IgG3, or IgG4.

23. The molecule or antibody of claim 18, wherein the molecule or antibody is detectably labeled or comprises a conjugated toxin, drug, receptor, enzyme, receptor ligand.

24. A fusion protein comprising the molecule or antibody of any one of claims 1-17 and heterologous amino acid sequence.

25. A chimeric antigen receptor (CAR) polypeptide comprising the molecule or antibody of any one of claims 1-17.

26. The chimeric antigen receptor of claim 25 comprising an extracellular antigen binding region, a spacer region, a transmembrane region, and intracellular signaling region.

27. The chimeric antigen receptor of claim 26 comprising a co-stimulatory domain.

28. A nucleic acid or acids encoding the molecule or antibody of any one of claims 1-17.

29. The nucleic acid or acids of claim 28 comprising an expression control sequence operably linked thereto, optionally wherein the expression control sequence comprises a promoter.

30. A vector comprising the nucleic acid or acids of claim 29.

31. A host cell comprising the nucleic acid sequence of claim 29.45728747v111532. A CAR immune cell comprising the CAR of claim 25.

33. A pharmaceutical composition comprising the molecule or antibody of any one of claims 1-17 optionally wherein the molecule or antibody comprises a drug conjugated thereto and / or has antibody-dependent cell-mediated cytotoxicity (ADCC) activity, or complement- dependent cytotoxicity activity (CDC), and / or is a bispecific immune cell engager.

34. A method of treating a subject in need thereof comprising administering the subject an effective amount of pharmaceutical composition of claim 33.

35. The method of claim 34, wherein the subject has a disease or disorder caused by or characterized by increased presence of HERV-K Env protein or a fragment thereof.

36. The method of claim 34, wherein the subject has a cancer, a neurological disorder, an immunodeficiency, an autoimmune disease, or HIV.

37. The method of claim 36, wherein the subject has cancer and HERV-K Env protein or fragment thereof is an antigen of the cancer cells.

38. A method of detecting HERV-K Env protein or fragment thereof comprising contacting a biological sample with one or more molecules or antibodies of any one of claims 1-17, and detecting binding between the molecule(s) or antibod(ies) and the HERV-K Env protein or fragment thereof.

39. The method of claim 38 further comprising determining that the sample includes increased HERV-K Env protein or fragment thereof if the level of detected binding is higher in the biological sample than in a control.

40. The method of claim 38, wherein binding is detected by an immunoassay, immunohistochemistry, Western blotting, surface plasmon resonance, flow cytometry (FACS) analysis, or a biochip.

41. The method of claim 40, wherein the immunoassay is selected from an enzyme immunoassay (EIA), radioimmunoassay (RIA), fluoroimmunoassay (FIA), chemiluminescent immunoassay (CLIA) and counting immunoassay (CIA), homogeneous enzyme-multiplied immunoassays (“EMIT”), apoenzyme reactivation immunoassay (“ARIS”), dipstick immunoassays, or immuno-chromatography assays.

42. The method of claim 38, wherein the biological sample is cells or a cell lysate or a fraction thereof or a fluid optionally blood, saliva, or urine.

43. The method of claim 42, wherein the cells or cell lysate or fraction thereof are derived from a biopsy from a subject.

44. The method of claim 43, wherein the biopsy contains or is suspected of containing tumor cells.45728747v111645. The method of claims 44, wherein the biopsy is a tumor biopsy.

46. A method of diagnosing a subject with a HERV-K Env protein-related disease or disorder comprising detecting HERV-K Env protein or fragment thereof according to the method of claim 38.

47. The method of claim 46, wherein the HERV-K Env protein-related disease or disorder is a cancer, a neurological disorder, an immunodeficiency, an autoimmune disease, or HIV.

48. The method of claim 46 further comprising treating the subject.

49. The method of claim 48, wherein the treatment comprises a therapy effective for treating a HERV-K Env protein-related diseases and disorders.

50. The method of claim 49, wherein the treatment comprises administering the subject an antiviral.

51. The method of claim 49, wherein the subject has disease or disorder selected from Breast cancer, Cervical cancer, Colon cancer, Head and neck cancer, Hepatocellular cancer, Kidney cancer, Lung cancer, Lymphoma, Melanoma, Ovarian cancer, Pancreatic cancer, Prostate cancer, Sarcoma, Seminoma, Teratocarcinoma, Urothelial cancer, Endometrial cancer, Germ Cell Tumors, Multiple Sclerosis (MS), Rheumatoid arthritis (RA), Amyotrophic Lateral Sclerosis (ALS), Autistic Spectrum disorder (ASD), Alzheimer’s Disease (AD), Hearing loss, Presbycusis, Increased cerumen production, Loss of visual acuity, Visual impairment, Loss of vestibular function, Sarcopenia, Chronic inflammation, Declining hormone levels, Impaired muscle, Mitochondrial function, Impaired muscle stem cell function, Muscle weakness, Immunosenescence, Decrease in urologic function, Cardiovascular disease, Chronic ischemic heart disease, Congestive heart failure, Arrhythmia, Atherosclerosis, Peripheral vascular disease, Hypertension, Rheumatoid arthritis, Juvenile rheumatoid arthritis, Osteoarthritis Osteoporosis, Short-term memory loss, Dementia, Progerias, Hutchinson–Gilford progeria syndrome (HGPS), Werner syndrome (WS), Cockayne, syndrome (CS), Bloom syndrome (BS), Ataxia-telangiectasia (A-T), Xeroderma pigmentosum (XP), Rothmund–Thomson syndrome (RTS), Centromere instability, Telomere instability, Facial anomalies syndrome (ICF), Myelodysplasia syndrome (MDS), Chronic lymphocytic leukemia (CLL), Acute myeloid leukemia (AML), Psoriatic arthritis, Diabetes mellitus, Multiple sclerosis, Encephalomyelitis, Myasthenia gravis, Systemic lupus erythematosus (SLE), Autoimmune thyroiditis, Atopic dermatitis, Eczematous dermatitis, Psoriasis, Sjogren’s Syndrome, Crohn’s disease, Aphthous ulcer, Iritis, Conjunctivitis, Keratoconjunctivitis, Ulcerative colitis, Inflammatory bowel disease (IBD), Cutaneous lupus, Erythematosus, Scleroderma, Vaginitis, Proctitis, Erythema nodosum leprosum, Autoimmune uveitis,, Allergic encephalomyelitis, Acute necrotizing, Hemorrhagic encephalopathy, Idiopathic bilateral progressive, Sensorineural hearing loss, Plastic45728747v1117anemia, Pure red cell anemia, Idiopathic thrombocytopenia, Polychondritis, Wegener’s granulomatosis, Chronic Active hepatitis, Stevens-Johnson syndrome, Idiopathic sprue, Lichen planus, Graves’ disease, Sarcoidosis, Primary biliary cirrhosis, Uveitis posterior, Interstitial lung fibrosis, Hashimoto’s thyroiditis, Autoimmune polyglandular syndrome, Insulin-dependent diabetes, Mellitus, Insulin-resistant diabetes mellitus, Immune-mediated infertility, Autoimmune Addison’s disease, Pemphigus vulgaris, Pemphigus foliaceus, Dermatitis herpetiformis, Autoimmune alopecia, Vitiligo, Autoimmune hemolytic anemia, Autoimmune thrombocytopenic purpura, Pernicious anemia, Guillain-Barre syndrome, Stiff-man syndrome, Acute rheumatic fever, Sympathetic ophthalmia, Goodpasture’s Syndrome, Systemic necrotizing vasculitis, Antiphospholipid syndrome or an allergy, Behcet’s disease, Severe combined immunodeficiency (SCID), Recombinase activating gene (RAG 1 / 2) deficiency, Adenosine deaminase (ADA) deficiency, Interleukin receptor common g chain (c) deficiency, Janus-associated kinase 3 (JAK3) deficiency and reticular dysgenesis, Primary T cell immunodeficiency, DiGeorge syndrome, Nude syndrome, T cell receptor deficiency, MHC class II deficiency, TAP-2 deficiency (MHC class I deficiency), ZAP70 tyrosine kinase deficiency and purine nucleotide phosphorylase (PNP) deficiency, antibody deficiencies, X-linked agammaglobulinemia (Bruton’s tyrosine kinase deficiency), Autosomal recessive agammaglobulinemia, Mu heavy chain deficiency, Surrogate light chain (g5 / 14.1) deficiency, Hyper-IgM syndrome: X-linked (CD40 ligand deficiency) or non-X- linked, Ig heavy chain gene deletion, IgA deficiency, Deficiency of IgG subclasses (with or without IgA deficiency), Common variable immunodeficiency (CVID), Antibody deficiency with normal immunoglobulins, Transient hypogammaglobulinemia of infancy, Interferon g receptor (IFNGR1, IFNGR2) deficiency, Interleukin 12 or interleukin 12 receptor deficiency, Immunodeficiency with thymoma, Wiskott-Aldrich syndrome (WAS protein deficiency), Ataxia telangiectasia (ATM deficiency), X-linkedlymphoproliferative syndrome (SH2D1 A / SAP deficiency), or Hyper IgE syndrome.45728747v1118

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