Antigen-coupled immunoreagents

Abstract

To provide an immunological reagent to which an antigen is coupled.SOLUTION: There is provided a high performance immunological reagent which is used for various immunoassay and other pertinent arts. The immunological reagent includes a primary antibody and a cross-link antigen, the cross-link antigen is recognized with high affinity by a secondary antibody which can be detected. There are also provided a composition including a panel of an immunological reagent which is specific to a plurality of different target antigen, and a composition including a pair of the primary immunological reagent and a secondary antibody which is complementary thereto and can be detected. The paired primary immunological reagent and the secondary antibody are useful for various immunoassay, especially, a highly multiplied assay. Similar to provision of multiplicity of the immunological reagent which can simultaneously detect multiplicity of the target antigen in a single assay, a structure of the cross-link antigen is varied in parallel with variation of the secondary antibody which can be detected. There are also provided a kit including the immunological reagent, a method of immunoassay using the immunological reagent of the disclosure, and a preparation method of the immunological reagent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 113,141, filed February 6, 2015, and U.S. Provisional Patent Application No. 62 / 247,415, filed October 28, 2015, the disclosures of which are incorporated herein by reference in their entireties. [Background technology]

[0002] The use of immunological assays, particularly immunohistochemical (IHC) staining, is crucial in the analysis of pathological conditions, such as the analysis of abnormal cells, including cancerous tumor cells. In IHC, immunoglobulins or antibodies that recognize specific antigens that may be present in diseased tissue are applied to thin sections of that tissue obtained by biopsy. The binding of the antibody to its cognate antigen is then detected by imaging the distribution of a chromogenic enzyme product, typically produced by an enzyme such as peroxidase, that colocalizes with the immunoglobulin within the tissue section. Examining the distribution of the enzyme product in comparison with the distribution of the histological stain allows for evaluation of the distribution of the antigen in the tissue section. In other immunological assays, antibody binding to the antigen can be detected by other means, including optical, electrical, or chemical signals. Specific antigens can characterize specific cellular events, such as infection, injury, cell proliferation, inflammation, or drug response. Immunological assays are also widely used in basic research to understand the distribution and localization of antigens, such as proteins that are differentially expressed in different parts of cells or biological tissues, that serve as biomarkers, and to identify and quantify these antigens in biochemical assays.Therefore, immunological assays are useful for, for example, blots, sandwich assays, immunosorbent assays, immunocytochemical assays, and other related methods.All of these methods can benefit from the improvement of immunochemical reagents.

[0003] Current methods of tissue analysis in clinical pathology are essentially limited to the determination of a single antigen performed on a single microscope slide. Importantly, there is a one-to-one correspondence between an antibody and its antigen, allowing for immediate determination of the antigen by antibody binding or lack thereof. If each antibody is linked to peroxidase or other enzymes, the presence of the antigen can be determined by the amount and distribution of the enzyme product on each tissue section as a proxy. However, there are often more than one antigen that must be evaluated to complete a particular analysis. For example, in breast cancer, to optimally match treatment to each patient, the minimum antigen profile of a biopsy specimen includes assessment of the presence and abundance of at least three antigens in the malignant cells of the tumor: Her2 / neu receptor (HER2), estrogen receptor (ER), and progesterone receptor (PR). Therefore, performing an analysis requires assays for each of the three distinct immunoglobulins, each of which is typically a monospecific monoclonal antibody capable of detecting only one of the three antigens. Therefore, to examine the degree of binding of the three different immunoglobulins to malignant cells using a conventional assay, three different IHC tests must be performed on three different tissue sections derived from the same block of tumor material. Additionally, with conventional enzyme-based assays, such as those currently typically used for routine tissue analysis, each slide must be evaluated by a pathologist using a qualitative scoring system to determine the presence or absence and level of expression of a given antigen. The results from the three tests must then be combined to determine a profile that provides prognostic information and aids in treatment selection. The efficiency, accuracy, and reliability of such assays are of great importance in the field.

[0004] Because of the need for a high level of reproducibility across laboratories, immunohistochemical analysis typically relies on standard methods, such as enzymatic detection, and a small number of well-studied antigens recognized by well-characterized antibodies (Moriya et al. (2006) Med. Mol. Morphol. 39:8-13; Payne et al. (2008) Histopathology 52:82-90; Yeh and Mies (2008) Arch. Pathol. Lab. Med. 132:349-57). Although direct detection of peroxidase associated with the primary antibody is sometimes used, indirect detection with a peroxidase-linked secondary antibody or through a primary antibody tagged with a high-affinity small molecule / binding protein pair, such as biotin and avidin, can be used to amplify the signal and, therefore, improve the sensitivity of the assay. However, in each of these cases, the strength of the signal is typically judged subjectively, thus limiting the diagnostic and prognostic value of the assay.

[0005] Approximately 1.6 million breast biopsies are performed annually in the United States, typically on women who develop a breast lump. A biopsy involves sampling tissue from the lump via fine-needle aspiration or core needle through the skin or open surgery. The resulting tissue is then examined to detect the presence of malignant cells. The majority of such biopsies are deemed benign based on examination of the tissue using histology techniques. In 2010, histological analysis determined that 260,000 biopsies were malignant. Of these, approximately 200,000 women had invasive breast cancer, while others had ductal carcinoma in situ (DCIS), in which cancer cells have not invaded surrounding tissue. Advances in early detection and curative treatment of primary tumors have dramatically improved breast cancer survival statistics. However, many tumors still elude early detection or, despite effective primary treatment, continue to develop distant metastases, the leading cause of breast cancer mortality. Much of the current effort in the molecular analysis of breast cancer is directed toward identifying new biomarkers and defining mechanistic determinants of prognosis and prediction. Any such novel disease markers would be beneficial if they could be easily incorporated into routine immunohistochemical staining of tissue biopsies.

[0006] As mentioned above, due to the limitations of detection using enzyme conjugates, each target antigen is often evaluated on a separate histological section, and internal control is not easily performed. As a result, quantitation, assessment of colocalization, and subcellular resolution are problematic. A well-established alternative to enzyme conjugates for detection in immunohistochemistry uses fluorescently labeled probes. The major advantage of this approach lies in its potential for multiplexing. Briefly, either the antibody itself or, more typically, a secondary antibody or other indirect detection reagent, is labeled with a fluorescent group, protein, or other material with known spectroscopic properties. Irradiation of the sample with light at the excitation wavelength of the fluorescent label allows the presence of a fluorescent signal at a specific emission wavelength and its localization at a site within the tissue section to be observed. Thus, the fluorescent signal serves the same purpose as a chromogenic enzyme product in providing information about the amount and distribution of the antigen.

[0007] The covalent modification of immunoglobulins with chemically reactive fluorescent reagents to form fluorescent antibodies, and the use of fluorescent antibodies in the detection of antigens, is now well established and was demonstrated in 1941 by Coons' modification of certain immunoglobulins with fluorescein isothiocyanate. Coons et al. (1941) Proc Soc Exp Biol. 47:200-2. The simultaneous detection of two antigens with antibodies labeled with distinct fluorescent colors, fluorescein and rhodamine, followed shortly thereafter. Modern chemistry offers a wide range of chemically reactive fluorophores with excitation and emission spectra spanning the ultraviolet to the infrared. In turn, modern coating methods have produced interference filters that, by selecting specific excitation and emission bands, can easily distinguish four or more different fluorophores across the visible light spectrum with signal-to-noise ratios much higher than 10.

[0008] Fluorescence-based immunoassays have become increasingly important in staining pathological sections and cytometry, at least in part due to their ability to distinguish between multiple antigens through the use of multiple, differentially labeled fluorescent antibodies. In these approaches, different antibodies can be distinguished, for example, by measuring fluorescence emitted at different wavelengths. Other spectroscopic properties of different fluorophores may also be used to distinguish between bound antibodies. While it is recognized that fluorescence-based assays may be used to detect more than three antigens on a single tissue, current methods using fluorescently labeled primary antibodies do not provide sufficient sensitivity. In particular, only three to five fluorophores can be conjugated to a single antibody due to fluorescence quenching or reduced immunoreactivity upon incorporation of more than five fluorophores into the antibody. Furthermore, monoclonal antibodies bind to a single epitope on any target antigen, thus further limiting any potential amplification of signal through binding of multiple antibodies to multiple sites on the antigen.

[0009] In contrast, fluorescently labeled polyclonal secondary antibodies can generate stronger signals than fluorescently labeled primary antibodies because multiple secondary antibodies can bind to distinct epitopes displayed on each primary antibody molecule. However, this approach is typically limited to detecting only one or two targets because the majority of primary antibodies are produced in only two species, mouse and rabbit.

[0010] One approach to enable multiplexing using antibodies from a single species has been the use of hapten-modified antibodies and fluorescently labeled anti-hapten antibodies. However, using conventional reagents, this method produces signals that are significantly less intense than those produced by fluorescently labeled secondary antibodies, likely due to the relatively low affinity of commercially available antibodies for small molecule haptens.

[0011] Thus, to further advance immunohistochemistry, there remains a need for a technology capable of generating a panel of reagents that can meet some or all of the following criteria: 1) the ability to simultaneously analyze multiple antigens within a single tissue sample and within the context of tissue morphology with greater sensitivity and specificity than currently available; 2) the ability to analyze the spatial distribution of multiple antigens in relation to each other; 3) the ability to individually quantify each antigen and determine the ratio of one antigen to another with greater sensitivity and specificity; 4) the ability to identify targets of interest (cell types) based on their staining patterns; 5) the ability to numerically quantify targets of interest; and 6) the ability to be incorporated into automated staining and image analysis paradigms that allow for the complete automation of the analysis of multiple antigens on a single tissue. Additionally, there remains a need for easy-to-use kits that allow for rapid, standardized detection and quantification of multiple antigens for diagnostic or research purposes. The present disclosure is directed to addressing these needs, as well as other currently unaddressed problems in immunological assays.

[0012] For example, Haertig and Fritschy (2009) Encyclopedia of Life Sciences (ELS), John Wiley & Sons (DOI: 10.1002 / 9780470015902.a0002626.pub2) disclose labeling of tissue sections with biotin-haptenized primary antibodies, digoxigenin-haptenized primary antibodies, and fluoresceinated lectins. The labeled samples were then stained using fluorescently labeled streptavidin, anti-digoxigenin, and anti-fluorescein. However, the level of multiplexing possible using these haptens is limited, and the low affinity of available antibodies for the haptens further limits the sensitivity of these assays.

[0013] Frisch et al. (2011) Methods Mol. Biol. 717:233-244 (DOI: 10.1007 / 978-1-61779-024-9_13) disclose a multicolor immunofluorescence technique using primary antigens from a single host source. Similar to Haertig and Fritschy, the primary antibody was haptenized with biotin and digoxigenin, and the secondary stain contained fluorescently labeled streptavidin and anti-digoxigenin. Samples were additionally labeled with a conventional fluorescently labeled cross-species secondary / primary antibody pair prior to treatment with the haptenized primary antibody to provide triple staining. While the technique minimizes cross-reactivity between unrelated primary and secondary antibodies and allows for limited simultaneous multiplexing, the approach suffers from limited sensitivity and cannot be easily scaled to higher levels of multiplexing.

[0014] Gerdes et al. (2013) PNAS 110:11982-7 (DOI: 10.1073 / pnas.1300136110) describe the use of MultiOmyx™ (GE Healthcare) hyperplexing technology to detect 61 protein biomarkers in formalin-fixed, paraffin-embedded (FFPE) cancer tissue. The assay uses pairs of fluorescently labeled antibodies in each round of staining, followed by peroxide bleaching of the dyes before each subsequent round. (See also www.multiomyx.com.) However, the technology is significantly limited by its ability to detect only highly expressed targets with fluorescently labeled primary antibodies and the need to use indirect detection to image low-expressing targets with fluorescently labeled secondary antibodies. The technique also requires optimization of antibody pairings for each round. The method is also extremely labor-intensive, with 31 rounds of staining, imaging, and bleaching. It is further recognized that multiple peroxide incubations can adversely affect the sensitivity of detection of each target in subsequent rounds of staining and imaging.

[0015] Hollman-Hewgley et al. (2014) Am. J. Path. Surg. 38:1193-1202 similarly describe the use of MultiOmyx™ (GE Healthcare) hypermultiplexing technology to detect 10 protein biomarkers in FFPE Hodgkin's lymphoma tissue.

[0016] Stack et al. (2014) Methods 70:46-58 (DOI: 10.1016 / j.ymeth.2014..08.016) describe a different iterative multiplexing approach that requires a separate single-plex IHC assay for each marker. There is initial labeling, followed by a series of steps to image a single biomarker by peroxidase / tyramide detection, followed by antibody removal using a microwave antigen retrieval step. This procedure is repeated 5-6 times as needed, depending on the number of biomarkers being interrogated. The procedure requires 2 days to complete. Despite the above attempts, there is a continuing need for the development of improved immunological assay reagents, methods, and kits with greater sensitivity, greater specificity, and greater ability to detect multiple antigens in a single assay. [Prior art documents] [Non-patent literature]

[0017] [Non-Patent Document 1] Coons et al. (1941) Proc Soc Exp Biol. 47:200-2 [Non-patent document 2] Haertig and Fritschy (2009) Encyclopedia of Life Sciences (ELS), John Wiley & Sons (DOI: 10.1002 / 9780470015902.a0002626.pub2) [Non-patent document 3] Frisch et al. (2011) Methods Mol. Biol. 717:233-244 (DOI:10.1007 / 978-1-61779-024-9_13) [Non-patent document 4] Gerdes et al. (2013) PNAS 110:11982-7 (DOI: 10.1073 / pnas.1300136110) [Non-patent document 5] Hollman-Hewgley et al. (2014) Am. J. Path. Surg. 38:1193-1202 [Non-patent document 6] Stack et al. (2014) Methods 70:46-58 (DOI:10.1016 / j.ymeth.2014..08.016) Summary of the Invention [Means for solving the problem]

[0018] The present disclosure, in one aspect, addresses these and other needs by providing an immunoreagent composition that has utility in a variety of immunological assays. Specifically, according to this aspect of the invention, the immunoreagent composition comprises: a primary antibody coupled to a bridging antigen; and Detectable secondary antibodies wherein the detectable second antibody is high affinity and specific for the cross-linked antigen.

[0019] In some embodiments, the cross-linked antigen is a peptide or small molecule hapten.

[0020] In some embodiments, the cross-linked antigen comprises multiple antigenic determinants. In a specific embodiment, each antigenic determinant in the multiple antigenic determinants is the same. In another specific embodiment, the multiple antigenic determinants comprise a linear repeat structure. More specifically, the linear repeat structure is a linear repeat peptide structure.

[0021] In another specific embodiment, the plurality of antigenic determinants comprises at least three antigenic determinants, or the cross-linked antigen comprises a branched structure.

[0022] In some embodiments, the cross-linked antigen is a peptide comprising a non-naturally occurring residue. Specifically, the non-naturally occurring residue may be a non-naturally occurring stereoisomer or a β-amino acid.

[0023] In some embodiments, the primary antibody and the cross-linking antigen are coupled by a chemical coupling reaction via a conjugation moiety. In specific embodiments, the primary antibody and the cross-linking antigen are coupled by a high-efficiency conjugation moiety. In some of these embodiments, the high-efficiency conjugation moiety is a Schiff base, such as a hydrazone or oxime. In some embodiments, the high-efficiency conjugation moiety is formed by a click reaction. In some embodiments, the conjugation moiety comprises a cleavable linker.

[0024] In certain embodiments, the primary antibody is specific for a cell marker, such as 4-1BB, AFP, ALK1, amyloid A, amyloid P, androgen receptor, annexin A1, ASMA, BCA225, BCL-1, BCL-2, BCL-6, BerEP4, beta-catenin, beta-HCG, BG-8, BOB-1, CA19-9, CA125, calcitonin, caldesmon, calponin-1, calretinin, CAM5.2, CD1a, CD2, CD3, CD4, CD5, CD7, CD8, CD10, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD30, CD31, CD33, CD34, CD38, CD42b, CD43, or CD45. LCA, CD45RO, CD56, CD57, CD61, CD68, CD79a, CD99, CD117, CD138, CD163, CDX2, CEA, chromogranin A, CMV, c-kit, c-MET, c-MYC, type IV collagen, complement 3c (C3c), COX-2, CXCR5, CK1, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK20, CK903, CKAE1, CK AE1 / AE3, D2-40, desmin, DOG-1, E-cadherin, EGFR, EMA, ER, ERCC1, factor VIII-related antigen, activated factor XIII, fascin, FoxP1, FoxP3, galectin-3, GATA-3, GCDFP-15, GCET1, GFAP, glycophorin A, glypican 3, granzyme B, HBME-1, Helicobacter pylori, hemoglobin A, Hep Par1, HER2, HHV-8, HMB-45, HSVl / ll, ICOS, IFN gamma, IgA, IgD, IgG, IgM, IL17, IL4, inhibin, iNOS, kappa Ig light chain, Ki67, LAG-3, lambda Ig light chain, lysozyme, mammaglobin A, MART-1 / MelanA, mast cell tryptase, MLH1, MOC-31, MPO, MSA, MSH2, MSH6, MUC1, MUC2, MUM1, MyoD1, myogenin, myoglobin, napsin A, nestin, NSE, Oct-2, OX40, OX40L, p16, p21, p27, p40, p53, p63, p504s, PAX-5, PAX-8, PD-1, PD-L1, PHH3, PIN-4, PLAP, PMS2, Pneumocystis jiroveci (carinii), PR, PSA, PSAP, RCC, S-100, SMA, SMM, smoothelin, SOX10, SOX11, surfactant apoprotein A, synaptophysin, TAG72, TdT, thrombomodulin, thyroglobulin, TIA-1, TIM3, TRAcP, TTF-1, tyrosinase, uroplakin, VEGFR-2, villin, vimentin, and WT-1. In another embodiment, the primary antibody is specific for immunoglobulins from a different species.

[0025] In embodiments, the detectable secondary antibody comprises a detectable label. In some embodiments, the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten. In specific embodiments, the detectable label is a fluorophore. In other specific embodiments, the enzyme is a peroxidase, such as horseradish peroxidase or soybean peroxidase, alkaline phosphatase, or glucose oxidase.

[0026] According to some embodiments, the detectable secondary antibody is specific for the cross-linked antigen and has a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, or at most 0.003 nM or even lower.

[0027] Some composition embodiments comprise multiple bridging antigen-coupled primary antibodies and multiple detectable secondary antibodies, including compositions comprising 3, 5, 10, or even more reagent pairs.

[0028] In another aspect, the present disclosure provides an immunoreagent comprising a primary antibody coupled to a cross-linked antigen.

[0029] In specific embodiments, the immunoreagent comprises one or more of the immunoreagent features of the immunoreagent composition described above.

[0030] According to another aspect, the present disclosure provides a multiplexed immunoreagent composition comprising any two or more of the above-described immunoreagents. In specific embodiments, the composition comprises at least three, at least five, at least ten, or even more immunoreagents.

[0031] In another aspect, the present disclosure provides a method for producing a pharmaceutical composition comprising: providing a first sample containing a first target antigen; reacting the first target antigen with a first immunoreagent, wherein the first immunoreagent is any of the above-described immunoreagents specific for the first target antigen; reacting the first immunoreagent with a first detectable secondary antibody, the first detectable secondary antibody being high affinity and specific for the cross-linked antigen of the first immunoreagent; and detecting the first detectable secondary antibody associated with the bridging antigen of the first immunoreagent. The present invention provides a method for an immunological assay, comprising:

[0032] In embodiments, the first target antigen is a cell marker, such as ER, HER2, PR, Ki67, EGFR, CK1, CK5, CK6, CK7, CK14, CK17, cytokeratin AE1 / AE3, nestin, vimentin, ASMA, Ber-EP4, p16, p40, p53, p63, c-kit, a CD marker, or any of the above markers. In another embodiment, the first target antigen is an immunoglobulin from a different species.

[0033] In specific embodiments, the first detectable secondary antibody comprises a detectable label. More specifically, the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten. In some embodiments, the detectable label is a fluorophore, and in some embodiments, the enzyme is peroxidase, alkaline phosphatase, or glucose oxidase. In specific embodiments, the peroxidase is horseradish peroxidase or soybean peroxidase.

[0034] In some embodiments, the first target antigen is in a tissue section. In these embodiments, the detecting step can be a fluorescent detection step or an enzymatic detection step.

[0035] In some embodiments, the first target antigen may be present in or on a cell. In these embodiments, the first target antigen may be present on the surface of the cell, in the cytoplasm of the cell, or in the nucleus of the cell.

[0036] In some embodiments, the detecting step is a fluorescent detection step, and in specific embodiments, the method may further comprise sorting cells that bind the first detectable secondary antibody.

[0037] In some embodiments, the method comprises: reacting a second target antigen in the first sample with a second immunoreagent, wherein the second immunoreagent is any of the above-described immunoreagents specific for the second antigen; reacting the second immunoreagent with a second detectable secondary antibody, the second detectable secondary antibody being high affinity and specific for the cross-linked antigen of the second immunoreagent; and detecting the second detectable secondary antibody associated with the bridging antigen of the second immunoreagent. Further includes:

[0038] More specific method embodiments further include detecting at least three target antigens in the sample, at least five target antigens in the sample, or even at least ten target antigens in the sample.

[0039] Some method embodiments include reacting a second target antigen in a second sample with a second immunoreagent, wherein the second immunoreagent is any of the immunoreagents described above that is specific for the second target antigen; reacting the second immunoreagent with a second detectable secondary antibody, the second detectable secondary antibody being high affinity and specific for the cross-linked antigen of the second immunoreagent; and detecting the second detectable secondary antibody associated with the bridging antigen of the second immunoreagent. wherein the first sample and the second sample are serial sections of a tissue sample.

[0040] Another method embodiment includes providing a sample comprising a first target antigen; reacting the first target antigen with a first immunoreagent, wherein the first immunoreagent is any of the above-described immunoreagents specific for the first target antigen; reacting the first immunoreagent with a first reactive secondary antibody, wherein the first reactive secondary antibody binds with high affinity to a bridging antigen of the first immunoreagent; and reacting the first reactive secondary antibody with a first detectable reagent, wherein the first detectable reagent is bound to the sample in proximity to the first target antigen; Includes.

[0041] In some embodiments, these methods further comprise dissociating the first reactive secondary antibody from the sample.

[0042] In some embodiments, these methods include reacting a second target antigen in the sample with a second immunoreagent, wherein the second immunoreagent is any of the immunoreagents described above that is specific for the second target antigen; reacting the second immunoreagent with a second reactive secondary antibody, wherein the second reactive secondary antibody binds with high affinity to the bridging antigen of the second immunoreagent; and reacting the second reactive secondary antibody with a second detectable reagent, wherein the second detectable reagent is bound to the sample in proximity to the second target antigen; still further includes:

[0043] In some embodiments, the methods include detecting the first detectable reagent and the second detectable reagent in the sample.

[0044] Other methods for immunological assays include providing a sample containing a first target antigen; reacting the first target antigen with a first primary antibody, wherein the first primary antibody is specific for the first target antigen; reacting the first primary antibody with a first immunoreagent, wherein the first immunoreagent is any of the above-described immunoreagents specific for the first primary antibody; reacting the first immunoreagent with a first detectable secondary antibody, the first detectable secondary antibody being high affinity and specific for the cross-linked antigen of the first immunoreagent; and detecting the first detectable secondary antibody associated with the bridging antigen of the first immunoreagent. Includes.

[0045] According to another aspect, the present disclosure provides a kit for immunological assays. In embodiments, the kit includes any of the above-described immunoreagents, a detectable secondary antibody that is high-affinity and specific for the bridging antigen of the immunoreagent, and instructions for using the kit. In specific embodiments, the kit includes at least three, at least five, or even at least ten of any of the above-described immunoreagents; at least three, at least five, or even at least ten detectable secondary antibodies that are high-affinity and specific for the bridging antigen of the immunoreagent; and instructions for using the kit. In an embodiment of the present invention, for example, the following items are provided: (Item 1) a primary antibody coupled to a bridging antigen; and Detectable secondary antibodies wherein said detectable secondary antibody is high affinity and specific for said cross-linked antigen. (Item 2) 2. The immunoreagent composition of claim 1, wherein the cross-linked antigen is a peptide. (Item 3) 2. The immunoreagent composition of claim 1, wherein the cross-linked antigen comprises multiple antigenic determinants. (Item 4) 4. The immunoreagent composition according to item 3, wherein each antigenic determinant in the plurality of antigenic determinants is the same. (Item 5) 4. The immunoreagent composition of claim 3, wherein the plurality of antigenic determinants comprises a linear repeat structure. (Item 6) 6. The immunoreagent composition according to item 5, wherein the linear repeat structure is a linear repeat peptide structure. (Item 7) 4. The immunoreagent composition according to item 3, wherein the plurality of antigenic determinants comprises at least three antigenic determinants. (Item 8) 4. The immunoreagent composition of claim 3, wherein the cross-linked antigen comprises a branched structure. (Item 9) Item 10. The immunoreagent composition of item 1, wherein the cross-linked antigen is a peptide containing a non-naturally occurring residue. 10. The immunoreagent composition of claim 9, wherein the non-natural residue is a non-natural stereoisomer. (Item 11) 10. The immunoreagent composition of claim 9, wherein the non-natural residue is a β-amino acid. (Item 12) 2. The immunoreagent composition of claim 1, wherein the primary antibody and the bridging antigen are coupled via a conjugation moiety through a chemical coupling reaction. (Item 13) 13. The immunoreagent composition of claim 12, wherein the primary antibody and the bridging antigen are coupled via a high-efficiency conjugation moiety. (Item 14) 14. The immunoreagent composition of claim 13, wherein the high-efficiency conjugation moiety is a Schiff base. (Item 15) 15. The immunoreagent composition of claim 14, wherein the Schiff base is a hydrazone or an oxime. (Item 16) 14. The immunoreagent composition according to item 13, wherein the high-efficiency conjugation moiety is formed by a click reaction. (Item 17) 13. The immunoreagent composition of claim 12, wherein the conjugation moiety comprises a cleavable linker. (Item 18) 2. The immunoreagent composition of claim 1, wherein the primary antibody is specific to a cell marker. (Item 19) The cell markers include 4-1BB, AFP, ALK1, amyloid A, amyloid P, androgen receptor, annexin A1, ASMA, BCA225, BCL-1, BCL-2, BCL-6, BerEP4, beta-catenin, beta-HCG, BG-8, BOB-1, CA19-9, CA125, calcitonin, caldesmon, calponin-1, calretinin, CAM5.2, CD1a, CD2, CD3, CD4, CD5, CD7, CD8, CD10, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD30, CD31, CD33, CD34, CD38, CD42b, CD43, and CD45. LCA, CD45RO, CD56, CD57, CD61, CD68, CD79a, CD99, CD117, CD138, CD163, CDX2, CEA, chromogranin A, CMV, c-kit, c-MET, c-MYC, type IV collagen, complement 3c (C3c), COX-2, CXCR5, CK1, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK20, CK903, CKAE1, CK AE1 / AE3, D2-40, desmin, DOG-1, E-cadherin, EGFR, EMA, ER, ERCC1, factor VIII-related antigen, activated factor XIII, fascin, FoxP1, FoxP3, galectin-3, GATA-3, GCDFP-15, GCET1, GFAP, glycophorin A, glypican 3, granzyme B, HBME-1, Helicobacter pylori, hemoglobin A, Hep Par1, HER2, HHV-8, HMB-45, HSV l / ll, ICOS, IFN gamma, IgA, IgD, IgG, IgM, IL17, IL4, inhibin, iNOS, kappa Ig light chain, Ki67, LAG-3, lambda Ig light chain, lysozyme, mammaglobin A, MART-1 / MelanA, mast cell tryptase, MLH1, MOC-31, MPO, MSA, MSH2, MSH6, MUC1, MUC2, MUM1, MyoD1, myogenin, myoglobin, napsin A, nestin, NSE, Oct-2, OX40, OX40L, p16, p21, p27, p40, p53, p63, p504s, PAX-5, PAX-8, PD-1, PD-L1, PHH3, PIN-4, PLAP, PMS2, Pneumocystisjiroveci (carinii), PR, PSA, PSAP, RCC, S-100, SMA, SMM, smoothelin, SOX10, SOX11, surfactant apoprotein A, synaptophysin, TAG72, TdT, thrombomodulin, thyroglobulin, TIA-1, TIM3, TRAcP, TTF-1, tyrosinase, uroplakin, VEGFR-2, villin, vimentin, and WT-1. (Item 20) 2. The immunoreagent composition of claim 1, wherein the primary antibodies are specific for immunoglobulins from different species. (Item 21) 2. The immunoreagent composition of claim 1, wherein the detectable secondary antibody comprises a detectable label. (Item 22) 22. The immunoreagent composition of claim 21, wherein the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten. (Item 23) 23. The immunoreagent composition of claim 22, wherein the detectable label is a fluorophore. (Item 24) 23. The immunoreagent composition of claim 22, wherein the enzyme is peroxidase, alkaline phosphatase, or glucose oxidase. (Item 25) 25. The immunoreagent composition of claim 24, wherein the peroxidase is horseradish peroxidase or soybean peroxidase. (Item 26) 2. The immunoreagent composition of claim 1, wherein the cross-linked antigen comprises a detectable label. (Item 27) 27. The immunoreagent composition of claim 26, wherein the detectable label of the cross-linked antigen is a fluorophore. (Item 28) 29. The immunoreagent composition of claim 26, wherein the detectable secondary antibody comprises a detectable label. 29. The immunoreagent composition of claim 28, wherein the detectable label of the cross-linked antigen and the detectable label of the secondary antibody are both detectable by fluorescence of the same wavelength. (Item 30) 2. The immunoreagent composition of claim 1, wherein the detectable secondary antibody is specific for the cross-linked antigen and has a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, or at most 0.003 nM. (Item 31) A multiplexed immunoreagent composition comprising a plurality of the immunoreagent compositions according to any one of items 1 to 30. (Item 32) 32. The multiplexed immunoreagent composition of item 31, comprising at least three immunoreagent compositions. (Item 33) 32. The multiplexed immunoreagent composition of item 31, comprising at least five immunoreagent compositions. (Item 34) 35. The multiplexed immunoreagent composition of claim 31, comprising at least 10 immunoreagent compositions. An immunoreagent containing a primary antibody coupled to a bridging antigen. (Item 36) 36. The immunoreagent according to item 35, wherein the cross-linked antigen is a peptide. (Item 37) 36. The immunoreagent of item 35, wherein the cross-linked antigen comprises multiple antigenic determinants. (Item 38) 38. The immunoreagent according to Item 37, wherein each antigenic determinant in the plurality of antigenic determinants is the same. (Item 39) 38. The immunoreagent of item 37, wherein the plurality of antigenic determinants comprises a linear repeat structure. (Item 40) 40. The immunoreagent according to item 39, wherein the linear repeat structure is a linear repeat peptide structure. (Item 41) 38. The immunoreagent according to item 37, wherein the plurality of antigenic determinants comprises at least three antigenic determinants. (Item 42) 38. The immunoreagent of item 37, wherein the cross-linked antigen comprises a branched structure. (Item 43) 36. The immunoreagent of item 35, wherein the cross-linked antigen is a peptide containing non-naturally occurring residues. (Item 44) 44. The immunoreagent of item 43, wherein the non-natural residue is a non-natural stereoisomer. (Item 45) 44. The immunoreagent of item 43, wherein the non-natural residue is a β-amino acid. (Item 46) 36. The immunoreagent of item 35, wherein the primary antibody and the bridging antigen are coupled via a conjugation moiety by a chemical coupling reaction. (Item 47) 47. The immunoreagent of item 46, wherein the primary antibody and the bridging antigen are coupled via a high-efficiency conjugation moiety. (Item 48) Item 49. The immunoreagent according to Item 47, wherein the high-efficiency conjugation moiety is a Schiff base. 49. The immunoreagent according to item 48, wherein the Schiff base is a hydrazone or an oxime. (Item 50) 48. The immunoreagent according to item 47, wherein the high-efficiency conjugation moiety is formed by a click reaction. (Item 51) 47. The immunoreagent of item 46, wherein the conjugation moiety comprises a cleavable linker. (Item 52) 36. The immunoreagent according to item 35, wherein the primary antibody is specific for a cell marker. (Item 53) The cell markers include 4-1BB, AFP, ALK1, amyloid A, amyloid P, androgen receptor, annexin A1, ASMA, BCA225, BCL-1, BCL-2, BCL-6, BerEP4, beta-catenin, beta-HCG, BG-8, BOB-1, CA19-9, CA125, calcitonin, caldesmon, calponin-1, calretinin, CAM5.2, CD1a, CD2, CD3, CD4, CD5, CD7, CD8, CD10, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD30, CD31, CD33, CD34, CD38, CD42b, CD43, and CD45. LCA, CD45RO, CD56, CD57, CD61, CD68, CD79a, CD99, CD117, CD138, CD163, CDX2, CEA, chromogranin A, CMV, c-kit, c-MET, c-MYC, type IV collagen, complement 3c (C3c), COX-2, CXCR5, CK1, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK20, CK903, CKAE1, CK AE1 / AE3, D2-40, desmin, DOG-1, E-cadherin, EGFR, EMA, ER, ERCC1, factor VIII-related antigen, activated factor XIII, fascin, FoxP1, FoxP3, galectin-3, GATA-3, GCDFP-15, GCET1, GFAP, glycophorin A, glypican 3, granzyme B, HBME-1, Helicobacter pylori, hemoglobin A, Hep Par1, HER2, HHV-8, HMB-45, HSV l / ll, ICOS, IFN gamma, IgA, IgD, IgG, IgM, IL17, IL4, inhibin, iNOS, kappa Ig light chain, Ki67, LAG-3, lambda Ig light chain, lysozyme, mammaglobin A, MART-1 / MelanA, mast cell tryptase, MLH1, MOC-31, MPO, MSA, MSH2, MSH6, MUC1, MUC2, MUM1, MyoD1, myogenin, myoglobin, napsin A, nestin, NSE, Oct-2, OX40, OX40L, p16, p21, p27, p40, p53, p63, p504s, PAX-5, PAX-8, PD-1, PD-L1, PHH3, PIN-4, PLAP, PMS2, Pneumocystis53. The immunoreagent according to Item 52, wherein the immunoreagent is selected from the group consisting of A. jiroveci (carinii), PR, PSA, PSAP, RCC, S-100, SMA, SMM, smoothelin, SOX10, SOX11, surfactant apoprotein A, synaptophysin, TAG72, TdT, thrombomodulin, thyroglobulin, TIA-1, TIM3, TRAcP, TTF-1, tyrosinase, uroplakin, VEGFR-2, villin, vimentin, and WT-1. (Item 54) 36. The immunoreagent according to item 35, wherein the primary antibody is specific for an immunoglobulin from a different species. (Item 55) 36. The immunoreagent of item 35, wherein the detectable secondary antibody comprises a detectable label. (Item 56) 56. The immunoreagent of item 55, wherein the detectable label is a fluorophore. (Item 57) A multiplexed immunoreagent composition comprising a plurality of the immunoreagents according to any one of items 35 to 56. (Item 58) 58. The multiplexed immunoreagent composition of item 57, comprising at least three immunoreagents. (Item 59) 58. The multiplexed immunoreagent composition of item 57, comprising at least five immunoreagents. (Item 60) 58. The multiplexed immunoreagent composition of item 57, comprising at least 10 immunoreagents. (Item 61) providing a first sample containing a first target antigen; reacting the first target antigen with a first immunoreagent, wherein the first immunoreagent is the immunoreagent according to any one of Items 35 to 56, which is specific for the first target antigen; reacting the first immunoreagent with a first detectable secondary antibody, the first detectable secondary antibody being high affinity and specific for the cross-linked antigen of the first immunoreagent; and detecting the first detectable secondary antibody associated with the bridging antigen of the first immunoreagent. 1. A method for immunological assays comprising: (Item 62) 62. The immunoreagent composition of claim 61, wherein the first target antigen is a cell marker. (Item 63) The cell markers include 4-1BB, AFP, ALK1, amyloid A, amyloid P, androgen receptor, annexin A1, ASMA, BCA225, BCL-1, BCL-2, BCL-6, BerEP4, beta-catenin, beta-HCG, BG-8, BOB-1, CA19-9, CA125, calcitonin, caldesmon, calponin-1, calretinin, CAM5.2, CD1a, CD2, CD3, CD4, CD5, CD7, CD8, CD10, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD30, CD31, CD33, CD34, CD38, CD42b, CD43, and CD45. LCA, CD45RO, CD56, CD57, CD61, CD68, CD79a, CD99, CD117, CD138, CD163, CDX2, CEA, chromogranin A, CMV, c-kit, c-MET, c-MYC, type IV collagen, complement 3c (C3c), COX-2, CXCR5, CK1, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK20, CK903, CKAE1, CK AE1 / AE3, D2-40, desmin, DOG-1, E-cadherin, EGFR, EMA, ER, ERCC1, factor VIII-related antigen, activated factor XIII, fascin, FoxP1, FoxP3, galectin-3, GATA-3, GCDFP-15, GCET1, GFAP, glycophorin A, glypican 3, granzyme B, HBME-1, Helicobacter pylori, hemoglobin A, Hep Par1, HER2, HHV-8, HMB-45, HSV l / ll, ICOS, IFN gamma, IgA, IgD, IgG, IgM, IL17, IL4, inhibin, iNOS, kappa Ig light chain, Ki67, LAG-3, lambda Ig light chain, lysozyme, mammaglobin A, MART-1 / MelanA, mast cell tryptase, MLH1, MOC-31, MPO, MSA, MSH2, MSH6, MUC1, MUC2, MUM1, MyoD1, myogenin, myoglobin, napsin A, nestin, NSE, Oct-2, OX40, OX40L, p16, p21, p27, p40, p53, p63, p504s, PAX-5, PAX-8, PD-1, PD-L1, PHH3, PIN-4, PLAP, PMS2, Pneumocystisjiroveci (carinii), PR, PSA, PSAP, RCC, S-100, SMA, SMM, smoothelin, SOX10, SOX11, surfactant apoprotein A, synaptophysin, TAG72, TdT, thrombomodulin, thyroglobulin, TIA-1, TIM3, TRAcP, TTF-1, tyrosinase, uroplakin, VEGFR-2, villin, vimentin, and WT-1. (Item 64) 62. The method of claim 61, wherein the first target antigen is an immunoglobulin from a different species. (Item 65) 62. The method of claim 61, wherein the first detectable secondary antibody comprises a detectable label. (Item 66) 66. The method of claim 65, wherein the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten. (Item 67) 67. The method of claim 66, wherein the detectable label is a fluorophore. (Item 68) 67. The method of claim 66, wherein the enzyme is peroxidase, alkaline phosphatase, or glucose oxidase. (Item 69) 69. The method of claim 68, wherein the peroxidase is horseradish peroxidase or soybean peroxidase. (Item 70) 62. The method of claim 61, wherein the first detectable secondary antibody is specific for the bridging antigen of the first immunoreagent and has a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, or at most 0.003 nM. (Item 71) 62. The method of claim 61, wherein the first target antigen is in a tissue section. (Item 72) 72. The method of claim 71, wherein the detecting step is a fluorescent detection step. (Item 73) 72. The method of claim 71, wherein the detecting step is an enzymatic detecting step. (Item 74) 62. The method of claim 61, wherein the first target antigen is in or on a cell. (Item 75) 75. The method of claim 74, wherein the first target antigen is on the surface of the cell. (Item 76) 75. The method of claim 74, wherein the first target antigen is in the cytoplasm of the cell. (Item 77) 75. The method of claim 74, wherein the first target antigen is in the nucleus of the cell. (Item 78) 75. The method of claim 74, wherein the detecting step is a fluorescent detection step. (Item 79) 80. The method of claim 78, further comprising sorting cells that bind to the first detectable secondary antibody. (Item 80) reacting a second target antigen in the first sample with a second immunoreagent, wherein the second immunoreagent is the immunoreagent according to any one of Items 35 to 56, which is specific to the second target antigen; reacting the second immunoreagent with a second detectable secondary antibody, the second detectable secondary antibody being high affinity and specific for the cross-linked antigen of the second immunoreagent; and detecting the second detectable secondary antibody associated with the bridging antigen of the second immunoreagent. Item 62. The method of item 61, further comprising: (Item 81) 81. The method of claim 80, further comprising detecting at least three target antigens in the sample. (Item 82) 81. The method of claim 80, further comprising detecting at least five target antigens in the sample. (Item 83) 81. The method of claim 80, further comprising detecting at least 10 target antigens in the sample. (Item 84) reacting a second target antigen in a second sample with a second immunoreagent, wherein the second immunoreagent is the immunoreagent according to any one of Items 35 to 56, which is specific to the second target antigen; reacting the second immunoreagent with a second detectable secondary antibody, the second detectable secondary antibody being high affinity and specific for the cross-linked antigen of the second immunoreagent; and detecting the second detectable secondary antibody associated with the bridging antigen of the second immunoreagent. Item 62. The method of item 61, further comprising: wherein the first sample and the second sample are serial sections of a tissue sample. (Item 85) 85. The method of claim 84, wherein multiple target antigens are detected in the first sample and multiple target antigens are detected in the second sample. (Item 86) 86. The method of claim 85, wherein at least three target antigens are detected in the first sample and at least three target antigens are detected in the second sample. (Item 87) 85. The method of item 84, wherein at least three target antigens are detected in at least three samples, and the at least three samples are serial sections of tissue samples. (Item 88) 88. The method of claim 87, wherein multiple target antigens are detected in each of the at least three samples. (Item 89) 89. The method of claim 88, wherein at least three target antigens are detected in each of the at least three samples. (Item 90) providing a sample containing a first target antigen; reacting the first target antigen with a first immunoreagent, wherein the first immunoreagent is the immunoreagent according to any one of Items 35 to 56, which is specific for the first target antigen; reacting the first immunoreagent with a first reactive secondary antibody, wherein the first reactive secondary antibody binds with high affinity to a bridging antigen of the first immunoreagent; and reacting the first reactive secondary antibody with a first detectable reagent, wherein the first detectable reagent is bound to the sample in proximity to the first target antigen; 1. A method for immunological assays comprising: (Item 91) 91. The method of claim 90, wherein the first reactive secondary antibody comprises an enzymatic activity. (Item 92) 92. The method of claim 91, wherein the enzymatic activity is peroxidase activity. (Item 93) 93. The method of claim 92, wherein the peroxidase activity is horseradish peroxidase activity. (Item 94) 91. The method of claim 90, wherein the first detectable reagent comprises a tyramide. (Item 95) 91. The method of claim 90, wherein the first detectable reagent comprises a fluorophore or chromophore. (Item 96) 91. The method of claim 90, further comprising dissociating the first reactive secondary antibody from the sample. (Item 97) 97. The method of claim 96, wherein the first reactive secondary antibody is dissociated from the sample by selective treatment. (Item 98) 98. The method of claim 97, wherein the selective treatment comprises treatment with a soluble cross-linked antigen. (Item 99) 98. The method of claim 97, wherein the selective treatment comprises cleavage of a cleavable linker. (Item 100) 97. The method of claim 96, wherein the first reactive secondary antibody is dissociated from the sample by heat treatment. (Item 101) reacting a second target antigen in the sample with a second immunoreagent, wherein the second immunoreagent is the immunoreagent according to any one of Items 35 to 56, which is specific to the second target antigen; reacting the second immunoreagent with a second reactive secondary antibody, wherein the second reactive secondary antibody binds with high affinity to the bridging antigen of the second immunoreagent; and reacting the second reactive secondary antibody with a second detectable reagent, wherein the second detectable reagent is bound to the sample in proximity to the second target antigen; Item 97. The method of item 96, further comprising: (Item 102) 102. The method of claim 101, wherein the second reactive secondary antibody comprises an enzymatic activity. (Item 103) 103. The method of claim 102, wherein the enzymatic activity is peroxidase activity. (Item 104) 104. The method of claim 103, wherein the peroxidase activity is horseradish peroxidase activity. (Item 105) 102. The method of claim 101, wherein the second detectable reagent comprises a tyramide. (Item 106) 102. The method of claim 101, wherein the second detectable reagent comprises a fluorophore or chromophore. (Item 107) 102. The method of claim 101, wherein the first reactive secondary antibody is dissociated from the sample by selective treatment. (Item 108) 108. The method of claim 107, wherein the selective treatment comprises treatment with a soluble cross-linked antigen. (Item 109) 108. The method of claim 107, wherein the selective treatment comprises cleavage of a cleavable linker. (Item 110) 102. The method of claim 101, wherein the first reactive secondary antibody is dissociated from the sample by heat treatment. (Item 111) 102. The method of claim 101, further comprising detecting the first detectable reagent and the second detectable reagent in the sample. (Item 112) providing a sample containing a first target antigen; reacting the first target antigen with a first primary antibody, wherein the first primary antibody is specific for the first target antigen; reacting the first primary antibody with a first immunoreagent, wherein the first immunoreagent is the immunoreagent according to any one of Items 35 to 56, which is specific to the first primary antibody; reacting the first immunoreagent with a first detectable secondary antibody, the first detectable secondary antibody being high affinity and specific for the cross-linked antigen of the first immunoreagent; and detecting the first detectable secondary antibody associated with the bridging antigen of the first immunoreagent. 1. A method for immunological assays comprising: (Item 113) The immunoreagent according to any one of Items 35 to 56. a high affinity, specific, detectable secondary antibody against the cross-linked antigen; and Instructions for using the kit A kit for an immunological assay comprising: (Item 114) 114. The kit of claim 113, wherein the detectable secondary antibody comprises a detectable label. (Item 115) 115. The kit of claim 114, wherein the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten. (Item 116) 116. The kit of claim 115, wherein the detectable label is a fluorophore. (Item 117) 117. The kit of claim 116, wherein the enzyme is peroxidase, alkaline phosphatase, or glucose oxidase. (Item 118) 118. The kit of item 117, wherein the peroxidase is horseradish peroxidase or soybean peroxidase. (Item 119) 114. The kit of claim 113, wherein the detectable secondary antibody is specific for the cross-linked antigen and has a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, or at most 0.003 nM. (Item 120) Item 113. The kit according to item 113, at least three immunoreagents according to any one of items 35 to 56; at least three detectable secondary antibodies that are high affinity and specific for the cross-linked antigen; and Instructions for using the kit Includes a kit. (Item 121) Item 113. The kit according to item 113, at least five immunoreagents according to any one of items 35 to 56; at least five detectable secondary antibodies that are high affinity and specific for the cross-linked antigen; and Instructions for using the kit Includes a kit. (Item 122) Item 113. The kit according to item 113, at least 10 immunoreagents according to any one of items 35 to 56; at least 10 detectable secondary antibodies that are high affinity and specific for the cross-linked antigen; and Instructions for using the kit Includes a kit. [Brief explanation of the drawings]

[0046] [Figure 1]1A-1C show schematic diagrams of an exemplary immunohistochemistry assay using a primary antibody coupled to a bridging antigen and a fluorescent secondary antibody specific for the bridging antigen: (A) the target antigen, represented as two gray stars on the surface of a tissue or other sample of interest; (B) the primary antibody coupled to a bridging antigen bound to the target antigen; and (C) the fluorescent secondary antibody bound to the primary antibody coupled to the bridging antigen, where the fluorophore on the secondary antibody is represented as two black stars.

[0047] [Figure 2] Figures 2A-2B show immunohistochemical staining of MCF7 cells with conventional cross-species secondary antibodies and with low-affinity commercially available antibodies specific for FLAG-tagged primary antibodies. Cells were labeled with either unlabeled human anti-HER2 / neu receptor primary antibodies (A) or FLAG-tagged human anti-HER2 / neu receptor primary antibodies (B). Cells were then stained with commercially available anti-human Dy488 secondary antibodies (A) or commercially available anti-FLAG-Dy490 secondary antibodies (B).

[0048] [Figure 3] Figures 3A-3B show immunohistochemical staining of triple-positive breast cancer cells with a cross-species secondary antibody or with a high-affinity antibody specific for a cross-linked antigen. Cells were labeled with either an unlabeled rabbit anti-HER2 / neu receptor primary antibody (A) or a peptide-conjugated rabbit anti-HER2 / neu receptor primary antibody (B). Cells were then stained with a standard fluorescent anti-rabbit secondary antibody (A) or a fluorescent high-affinity anti-peptide antibody (B).

[0049] [Figure 4] Figures 4A-4D show a comparison of four peptide-coupled primary antibody / fluorophore-conjugated anti-peptide secondary antibody pairs. For each pair, an anti-Ki67 primary antibody was conjugated to a peptide of interest. A fluorophore-conjugated secondary antibody specific for the peptide of interest was applied to visualize the Ki67 positive signal: (A) PEP2, (B) PEP3, (C) PEP4, and (D) PEP5.

[0050] [Figure 5] Figures 5A-5B show a comparison of the staining intensity of estrogen receptors with the PEP1 and PEP5 pairs. Anti-ER primary antibodies were coupled to either PEP1 (A) or PEP5 (B) and stained with the corresponding fluorophore-labeled high-affinity anti-peptide antibodies.

[0051] [Figure 6] Figures 6A-6D show multiplexed staining of breast cancer tissue with three different pairs of peptide-coupled primary antibodies and high-affinity fluorescent anti-peptide secondary antibodies: PEP7-coupled anti-ER primary antibody / Dy550-labeled anti-PEP7 secondary antibody, PEP5-coupled anti-HER2 primary antibody / Dy490-labeled anti-PEP5 secondary antibody, and PEP1-coupled anti-Ki67 primary antibody / Dy755-labeled anti-PEP1 secondary antibody. (A) Dy550 emission, (B) Dy490 emission, (C) Dy755 emission, and (D) an overlay of the three images.

[0052] [Figure 7] Figure 7 shows a schematic diagram of an exemplary three-step amplified staining protocol using an antigen-coupled cross-species secondary antibody: Step A: label the sample with an unmodified antibody from a first species; Step B: label the bound antibody with a cross-species antibody coupled to a bridging antigen; and Step C: stain the bridging antigen with a fluorescent antibody specific for the bridging antigen.

[0053] [Figure 8] 8A-8B show the results of staining for HER2 (A) and ER (B) in triple-positive breast cancer tissue using a three-step staining procedure with peptide-coupled cross-species antibodies.

[0054] [Figure 9]Figures 9A-9D show multiplexed staining of melanoma tissue sections with three different pairs of peptide-coupled primary antibodies and fluorescent high-affinity anti-peptide secondary antibodies. (A) Emission from the anti-CD4 pair, (B) Emission from the anti-CD20 pair, (C) Emission from the anti-CD68 pair, and (D) Overlay of the emissions from the anti-CD4, anti-CD20, and anti-CD68 pairs. Insets in Figures 9A, 9B, and 9C are zoomed-in views of each section.

[0055] [Figure 10] Figures 10A-10D show multiplexed staining of triple-negative breast cancer tissue sections with three different pairs of peptide-coupled primary antibodies and fluorescent high-affinity anti-peptide secondary antibodies: (A) emission from the anti-CK5 pair, (B) emission from the anti-CK6 pair, (C) emission from the anti-Ki-67 pair, and (D) overlay of emission from the anti-CK5, anti-CK6, and anti-Ki-67 pairs.

[0056] [Figure 11] 11A-11E show multiplexed staining of squamous cell cervical cancer tissue sections with four different pairs of peptide-coupled primary antibodies and fluorescent high-affinity anti-peptide secondary antibodies: (A) emission from the anti-CK5 pair, (B) emission from the anti-EGFR pair, (C) emission from the anti-p40 pair, (D) emission from the anti-Ki-67 pair, and (E) overlay of emission from the anti-CK5 pair, anti-EGFR pair, anti-p40 pair, and anti-Ki-67 pair.

[0057] [Figure 12] 12A-12D show staining of kidney cancer core biopsy sections with pairs of peptide-coupled primary antibodies and fluorescent high-affinity anti-peptide secondary antibodies: (A) Emission from the anti-IgA pair, in which the secondary antibody is labeled with Dy491; (B) Emission from the anti-C3c pair, in which the secondary antibody is labeled with Dy550; (C) Emission from the anti-COL4A5 pair, in which the secondary antibody is labeled with Dy650; and (D) Emission from the anti-IgG pair, in which the secondary antibody is labeled with Dy755.

[0058] [Figure 13] 13A-13E show quadruple staining of triple-positive breast cancer markers in a single tissue section: (A) HER2, (B) ER, (C) PR, (D) Ki-67, and (E) an overlay of the four images.

[0059] [Figure 14] Figures 14A-14E show quadruple staining of triple-positive breast cancer markers in a single tissue section, detecting (A) CD3, (B) CD4, (C) CD8, and (D) CD20. In (E), an overlay of the four images is shown.

[0060] [Figure 15] FIG. 15 shows an overlay of sequential tissue staining results from a triple-positive breast cancer panel (FIG. 14) and a quadruple staining with a quadruple immunomarker panel (FIG. 15), showing HER2, ER, PR, Ki-67, CD3, CD4, and CD8.

[0061] [Figure 16] 16A-16E show quadruple staining of triple-negative breast cancer tissue detecting (A) CK5, (B) vimentin, (C) EGFR, (D) Ki-67, and (E) an overlay of the four images.

[0062] [Figure 17] Figures 17A-17E show quadruple staining of triple-negative breast cancer tissue to detect (A) CD8, (B) CD4, (C) CD20, (D) CD3, and (E) an overlay of the four images.

[0063] [Figure 18]Figure 18 shows an overlay of sequential tissue staining results from a triple-negative breast cancer panel (Figure 16) and quadruple staining with a quadruple immunomarker panel (Figure 17), showing EGFR, vimentin, CK5, Ki-67, CD3, CD4, and CD8. (CD20 is not shown due to software limitations.)

[0064] [Figure 19] FIG. 19 shows an overlay of quadruple staining of triple-negative breast cancer tissue detecting CK5, vimentin, EGFR, and Ki-67.

[0065] [Figure 20] Figure 20A shows an overlay of quadruple staining of triple-negative breast cancer tissue detecting CD4, CD8, CD68, and FoxP3. Figure 20B shows exemplary single-cell images showing the marker phenotypes (and putative cell types) and total counts of each phenotype within a representative field of view from the section in Figure 20A.

[0066] [Figure 21] Figure 21 shows an overlay of triple-staining of triple-negative breast cancer tissue detecting CD3, PD-1, and PD-L1. Representative single-cell images and their phenotypes are also shown. (TIL = tumor-infiltrating lymphocytes).

[0067] [Figure 22] FIG. 22 shows an overlay of three consecutive tissues multiplex stained with a triple-negative breast cancer panel (FIG. 19), a quadruple immunomarker panel (FIG. 20A), and a triple immunomarker panel (FIG. 21).

[0068] [Figure 23] Figure 23 shows a schematic diagram of an exemplary sequential tyramide dye amplification protocol for two targets on the same tissue sample. The first detectable secondary antibody is selectively removed from the sample in step D by treatment with an excess of a soluble form of the cross-linking antigen.

[0069] [Figure 24] Figures 24A-24C show the results of a sequential tyramide staining amplification protocol. Using a tyramide signal amplification protocol with peptide-mediated stripping of an anti-peptide secondary antibody-HRP conjugate, two targets are identified in a single tissue section. Sequential staining of HER2 and ER with (1) rabbit anti-HER1-PEP5 / anti-PEP5-HRP / tyramide-Dy490 (Figure 24A), (2) stripping of anti-PEP5-HRP with excess PEP5, and (3) staining of ER with rabbit anti-ER-PEP-2 / anti-PEP2-HRP / tyramide-Dy550 (Figure 24B). Figure 24C presents an overlay of the images in Figures 24A and 24B.

[0070] [Figure 25] FIG. 25 shows a schematic diagram of staining with a primary antibody containing a tandem repeat peptide cross-linked antigen to increase the number of antigenic determinants for reaction with a detectable anti-peptide secondary antibody.

[0071] [Figure 26] Figures 26A-26B show staining of triple-positive breast cancer tissue with a secondary antibody (A) and a tandem repeat-conjugated primary antibody (B). In this case, triple-positive breast cancer tissue (ILS30380) was stained with rabbit anti-HER2 / Dy490-anti-rabbit IgG (A) and tandem repeat 3X-peptide (PEP6')-conjugated anti-HER2 / Dy650-anti-PEP6.

[0072] [Figure 27] FIG. 27 shows a schematic diagram of staining with an immunoreagent comprising a primary antibody coupled to a fluorophore-labeled cross-linking antigen.

[0073] [Figure 28] Figures 28A-28D show staining results on triple-positive breast cancer tissue comparing rabbit anti-HER2 / anti-rabbit-FITC with HER2-PEP7-FITC modified with three increasing levels of fluorescent label.

[0074] [Figure 29] Figures 29A-29B show sequential staining of triple-positive breast cancer tissue, with a heating step to remove the immunoreagents after the initial staining. Figure 29A shows the initial quadruple staining using a cocktail of immunoreagents targeting the immunomarkers CD8 (red in the original image), CD4 (blue in the original image), CD20 (green in the original image), and CD3 (magenta in the original image). After imaging, the immunoreagents were removed by microwave heating. Figure 29B shows the same section subsequently stained and imaged using a cocktail of immunoreagents targeting the breast cancer markers HER2 (red in the original image), ER (blue in the original image), PR (green in the original image), and Ki-67 (magenta in the original image). The breast cancer panel signal was normalized to the signal generated by the immunomarker panel signal. DETAILED DESCRIPTION OF THE INVENTION

[0075] Antigen-coupled immunoreagents In one aspect, the present disclosure provides a high-performance immunoreagent comprising a primary antibody and a bridging antigen, wherein the primary antibody and the bridging antigen are coupled and the bridging antigen is recognizable by a high-affinity, detectable secondary antibody.

[0076] As is well known in the art, antibodies are glycoproteins belonging to the immunoglobulin superfamily. Antibodies typically contain two large heavy chains and two small light chains, although a variety of alternative or modified antibody structures may be suitably employed in the immunoreagents and compositions of the present disclosure. For example, antibodies may be natural antibodies, artificial antibodies, genetically engineered antibodies, monovalent antibodies, polyvalent antibodies, monoclonal antibodies, polyclonal antibodies, camelid antibodies, monobodies, single-chain variable fragments (scFv), and / or fragments or derivatives thereof, including Fab fragments and F(ab')2 fragments. In certain applications, antibodies may be monospecific, multispecific, humanized, single-chain, chimeric, camelid single-domain, shark single-domain, synthetic, recombinant, hybrid, mutant, CDR-grafted antibodies, and / or fragments or derivatives thereof. In certain embodiments, antibodies may be derived from any suitable mammalian species. For example, antibodies may be derived from humans, rats, mice, goats, guinea pigs, donkeys, rabbits, horses, llamas, or camels. In other embodiments, antibodies may be derived from birds, such as chickens or ducks. The origin of an antibody is defined by its genomic sequence, regardless of the method of production. The antibodies of the present immunoreagents may be of various isotypes, e.g., IgG, IgM, IgA, IgD, IgE, or subclasses, e.g., IgG1, IgG2, IgG3, IgG4. Antibodies may be produced recombinantly or by other means and may include antibody fragments, e.g., Fab, F(ab)2, Fv, scFv, VhH, and / or V-NAR, that are still capable of binding antigen.

[0077] Polyclonal antibodies suitable for use in the present immunoreagents can be produced through a variety of methods. For example, for this purpose, various animals can be immunized by injecting them with the antigen of interest, such as the target biomolecule or another molecule that shares an epitope with the target biomolecule. Such antigenic molecules can be naturally occurring, obtained by recombinant DNA or synthetic methods, or fragments thereof, and the desired polyclonal antibodies can be obtained or purified from the resulting serum. Alternatively, intact cells that display the target biomolecule or the appropriate epitope of the target molecule can be used. Various adjuvants can also be used to increase the immune response to antigen administration, depending on the animal selected for immunization. Examples of these adjuvants include Freund's adjuvant, mineral gels such as aluminum hydroxide, surfactants such as polyanions, peptides, oil emulsions, hemocyanin, dinitrophenol, or lysolecithin.

[0078] Monoclonal antibodies suitable for use in the present immunoreagents are typically obtained from hybridoma cells, which are prepared by fusing spleen cells and myeloma cells from an animal immunized with the desired antigen. Cells expressing the desired antibody are then identified by their ability to bind to the desired antigen. Stable hybridoma clones that produce significant amounts of the desired antibody can then be cultured to produce useful quantities of the antibody. These techniques are well known in the art.

[0079] The immunoreagent can be used in immunological assays to identify and bind to a target antigen of interest, with the specificity of the target binding being determined by the specificity of the antibody used to prepare the immunoreagent. In particular, the primary antibody of the immunoreagent can be directed to a target antigen that displays a protein or other antigenic molecule of interest either intracellularly or on the surface of a cell. In some cases, the target antigen can be found within an intracellular organelle, such as the nucleus or mitochondria of a cell. Alternatively, the target antigen can be displayed on a surface of interest, such as an immunoblot or other type of two-dimensional medium. In some cases, the target antigen can be in an impure, partially purified, or purified form. Generally, the target antigen can be present on or within any suitable surface, or even free in solution, as long as it is effective to specifically interact with the immunoreagent.

[0080] Furthermore, the target antigen of interest can be any protein or other molecule of interest. In some embodiments, the target antigen can be a cellular marker that provides information about the disease state of cells or tissues in an animal. For example, the target antigen can be estrogen receptor (ER), HER2 / neu receptor (HER2), progesterone receptor (PR), Ki67, EGFR, cytokeratin 1 (CK1), cytokeratin 5 (CK5), cytokeratin 6 (CK6), cytokeratin 7 (CK7), cytokeratin 14 (CK14), cytokeratin 17 (CK17), cytokeratin AE1 / AE3, nestin, vimentin, ASMA, Ber-EP4, p16, p40, p53, p63, c-kit, various CD markers, including those listed below, or any other target antigen that can be specifically recognized by the primary antibody of the immunoreagent. In some embodiments, multiple cellular markers can be targeted. For example, in some embodiments, the target antigen can be ER and PR. In other embodiments, the target antigens may be HER2, ER, and PR, or HER2, ER, and Ki67. In still other embodiments, the target antigens may be HER2, ER, PR, and Ki67. In still other embodiments, the target antigens may be Ki67, EGFR, and CK5. In yet other embodiments, the target antigens may be Ki67, EGFR, CK5, and CK6.

[0081] Other specific target antigens include 4-1BB, AFP, ALK1, amyloid A, amyloid P, androgen receptor, annexin A1, ASMA, BCA225, BCL-1, BCL-2, BCL-6, BerEP4, beta-catenin, beta-HCG, BG-8, BOB-1, CA19-9, CA125, calcitonin, caldesmon, calponin-1, calretinin, CAM5.2, CD1a, CD2, CD3, CD4, CD5, CD7, CD8, CD10, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD30, CD31, CD33, CD34, CD38, CD42b, CD43, and CD45. LCA, CD45RO, CD56, CD57, CD61, CD68, CD79a, CD99, CD117, CD138, CD163, CDX2, CEA, chromogranin A, CMV, c-kit, c-MET, c-MYC, type IV collagen, complement 3c (C3c), COX-2, CXCR5, CK1, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK20, CK903, CKAE1, CK AE1 / AE3, D2-40, desmin, DOG-1, E-cadherin, EGFR, EMA, ER, ERCC1, factor VIII-related antigen, activated factor XIII, fascin, FoxP1, FoxP3, galectin-3, GATA-3, GCDFP-15, GCET1, GFAP, glycophorin A, glypican 3, granzyme B, HBME-1, Helicobacter pylori, hemoglobin A, Hep Par1, HER-2, HHV-8, HMB-45, HSV l / ll, ICOS, IFN gamma, IgA, IgD, IgG, IgM, IL17, IL4, inhibin, iNOS, kappa Ig light chain, Ki-67, LAG-3, lambda Ig light chain, lysozyme, mammaglobin A, MART-1 / MelanA, mast cell tryptase, MLH1, MOC-31, MPO, MSA, MSH2, MSH6, MUC1, MUC2, MUM1, MyoD1, myogenin, myoglobin, napsin A, nestin, NSE, Oct-2, OX40, OX40L, p16, p21, p27, p40, p53, p63, p504s, PAX-5, PAX-8, PD-1, PD-L1, PHH3, PIN-4, PLAP, PMS2, Pneumocystisjiroveci (carinii), PgR, PSA, PSAP, RCC, S-100, SMA, SMM, smoothelin, SOX10, SOX11, surfactant apoprotein A, synaptophysin, TAG72, TdT, thrombomodulin, thyroglobulin, TIA-1, TIM3, TRAcP, TTF-1, tyrosinase, uroplakin, VEGFR-2, villin, vimentin, and WT-1.

[0082] In some embodiments, the primary antibody of the immunoreagent may be a cross-species reactive antibody directed against one or more sequences in immunoglobulin molecules that do not differ significantly between different immunoglobulins within the same species. Such sequences are typically found within the so-called "constant regions" of immunoglobulin sequences. Recognition of these sequences is possible because the antibodies used in the immunoreagent are generated by immunization of a particular animal species, e.g., goat, with immunoglobulins isolated from a different animal species, e.g., mouse or rabbit. Antibodies raised in goats against mouse immunoglobulins are therefore referred to as "goat anti-mouse" antibodies, and antibodies raised in goats against rabbit immunoglobulins are therefore referred to as "goat anti-rabbit" antibodies. Polyclonal antibodies directed against cross-species immunoglobulins may be useful for signal amplification in immunological assays due to their ability to recognize multiple epitopes in the cross-species primary antibody, as illustrated in the Examples section.

[0083] The bridging antigen of the present immunoreagents is selected to be recognizable by a secondary antibody, ideally with high affinity. Thus, the structure of the bridging antigen is limited only by molecules that can elicit an immune response in a suitable animal or that can be used to raise suitable secondary antibodies by other means.

[0084] In some embodiments, the bridging antigen is a separate molecular entity from the primary antibody and is bound to the primary antibody through a chemical coupling reaction. In these embodiments, the bridging antigen is designed to contain at least one group that can chemically couple the bridging antigen to the primary antibody of the immunoreagent. The group may also be useful for chemically coupling the bridging antigen to a carrier protein or other suitable molecule in preparing the immunogen used to raise the secondary antibody. As described in more detail below, the coupling group may, in specific embodiments, be selected so that the bridging antigen is conjugated to the primary antibody or carrier protein with high specificity and efficiency. In addition, coupling of the bridging antigen to the primary antibody should not significantly affect the ability of the bridging antigen to be recognized by a detectable secondary antibody. It is also desirable that the bridging antigen and coupling group themselves do not have interfering absorbance or fluorescence to avoid any background signal. Furthermore, the bridging antigen and coupling group should be available in high purity and, ideally, at low cost.

[0085] In some embodiments, the cross-linked antigen of the present disclosure is a synthetic cross-linked antigen. In some embodiments, the cross-linked antigen is a natural product. In specific embodiments, the cross-linked antigen is a peptide.

[0086] Peptides, either synthetic or isolated from natural sources, have been widely used to generate specific, high-affinity antibodies by a variety of means, as is well known and understood by those skilled in the art. The range of structural variations possible for peptides is almost limitless, making them ideally suited for use as cross-linked antigens in the present immunoreagents. Furthermore, synthetic peptides can be designed to contain reactive groups to facilitate their coupling to primary antibodies, for example, during solid-phase peptide synthesis or after synthesis, by including amino acid residues or other linking moieties at the C- or N-terminus or internally, along with desirable reactive properties within the peptide sequence. Peptide cross-linked antigens, both natural and artificial, can be of any size and contain any suitable amino acids or other residues. They can be linear or cyclic. In these embodiments, peptide cross-linked antigens are limited only by their ability to conjugate to the antibody of interest and to be recognizable by a detectable secondary antibody.

[0087] In some embodiments, the cross-linked antigen is a peptide containing a non-natural residue. For example, the cross-linked antigen may contain a non-natural stereoisomer, such as a D-amino acid. In some embodiments, the non-natural residue may be a non-natural amino acid, such as a β-amino acid. In some embodiments, the residues of the cross-linked antigen may be coupled using a non-peptide bond, as understood by those skilled in the art.

[0088] In some embodiments, the bridging antigen is a peptide antigen that has been engineered to be expressed as part of the protein sequence of the primary antibody itself. Examples of antigens that can be engineered into the primary sequence of an antibody and therefore serve as bridging antigens include, but are not limited to, Myc tag, FLAG tag, HA tag, S tag, Streptag, His tag, or V5 tag.

[0089] Other suitable cross-linked antigens usefully included in the present immunoreagents include non-peptide small molecule antigens. As is true for peptide cross-linked antigens, such antigens are limited only by their ability to be coupled to a primary antibody and to be recognized by a detectable secondary antibody. Exemplary non-peptide small molecule antigens, sometimes referred to herein as "haptens," include, but are not limited to, nitrophenyl, dinitrophenyl, trinitrophenyl, digoxigenin, biotin, 5-bromodeoxyuridine, 3-nitrotyrosine, small molecule drugs, and any other similar chemical tags.

[0090] To increase the number of binding sites per immunoreagent, it may be advantageous in some cases for a single cross-linked antigen to contain multiple antigenic determinants or epitopes. The multiplicity of antigenic determinants in the cross-linked antigen may increase the number of secondary antibodies that can bind to the immunoreagent and, therefore, the sensitivity of the assay using the immunoreagent. In some embodiments, the multiple antigenic determinants may include multiple copies of the same antigenic determinant, while in some embodiments, the multiple antigenic determinants may include different antigenic determinants. In some embodiments, the multiple antigenic determinants may include a linear repeat structure. More specifically, the linear repeat structure may be a linear repeat peptide structure. In some embodiments, the multiple antigenic determinants may include at least two antigenic determinants, at least three antigenic determinants, at least four antigenic determinants, at least six antigenic determinants, or even more antigenic determinants.

[0091] In some embodiments, the cross-linked antigen may comprise a branched structure, such as a dendrimer structure or other polymeric construct, as will be appreciated by those skilled in the art.

[0092] It is further understood that a cross-linked antigen comprising multiple antigenic determinants may include one or more polyethylene glycol linkers or the like between the antigenic determinants, for example, between peptide antigenic determinants.

[0093] In some embodiments, the peptide antigenic determinants comprise at least 4, at least 6, at least 8, at least 10, at least 15, at least 20, or even more amino acid residues per antigenic determinant.

[0094] When the primary antibody and cross-linking antigen are prepared from separate molecular entities, it should be understood that coupling of the primary antibody to the cross-linking antigen can be achieved in a variety of ways, depending on the desired result. When control of the location and degree of coupling of the cross-linking antigen to the primary antibody is not important, nonspecific chemical cross-linkers can be used to achieve coupling. However, it is generally desirable for the cross-linking antigen to be coupled to the primary antibody in a controlled, specific manner, and the choice of coupling method and coupling agent can affect the location, degree, and efficiency of coupling. For example, because reactive thiol groups are relatively rare on the surface of antibody proteins, the use of thiol-reactive conjugation reagents typically results in a relatively lower level of protein modification. Because reactive amino groups are much more common on the surface of antibodies, the use of amine-reactive conjugating reagents typically results in a relatively higher level of protein modification with the cross-linking antigen. In addition, the degree of modification of the antibody with the conjugating reagent can be titrated to some extent, for example, by using a limited amount of conjugating reagent relative to the number of reactive groups on the antibody.

[0095] In some immunoreagent embodiments, the primary antibody and the cross-linked antigen are coupled by a chemical coupling reaction via a conjugation moiety. In specific embodiments, the primary antibody and the cross-linked antigen are coupled by a high-efficiency conjugation moiety. Because immunoreagents are preferably synthesized using starting materials with relatively low molar concentrations, and because these starting materials, such as primary antibodies, are expensive and available in relatively small chemical amounts, it is highly desirable that the formation of the conjugation moiety be as efficient and specific as possible, and that its formation be complete or nearly complete with a low molar concentration of reactants. Specifically, it is desirable that the conjugation moiety be capable of coupling the primary antibody and the cross-linked antigen with a fast reaction rate and / or a high association constant, and therefore that the association reaction be as efficient as possible in terms of its completion.

[0096] The highly efficient conjugation moieties of the present immunoreagents are typically formed by separate modification of each component of the immunoreagent with a complementary conjugation reagent, as described in more detail below. The complementary conjugation reagent additionally contains an additional reactive moiety, e.g., a thiol-reactive moiety or an amino-reactive moiety, that enables the conjugation reagent to bind to the associated immunoreagent component, e.g., the antibody, and to the bridging antigen. After the antibody and bridging antigen are modified with their respective complementary conjugation reagents, typically at multiple positions on the antibody but at a single position on the bridging antigen, the complementary conjugating features on the modified components associate with each other in a highly efficient and specific manner to form the conjugation moieties.

[0097] Depending on the circumstances, the high-efficiency conjugation moiety of the present immunoreagents can be a covalent or non-covalent conjugation moiety. In specific embodiments, the high-efficiency conjugation moiety is a covalent conjugation moiety, such as a hydrazone, oxime, or another suitable Schiff base moiety. Non-limiting examples of such conjugation moieties can be found, for example, in U.S. Pat. No. 7,102,024, which is incorporated by reference herein in its entirety for all purposes. These conjugation moieties can be formed by the reaction of a primary amino group on a conjugate reagent bound to one component of the immunoreagent (e.g., a primary antibody) with a complementary carbonyl group on a conjugate reagent bound to another component of the immunoreagent (e.g., a cross-linked antigen).

[0098] For example, hydrazone conjugation moieties can be formed by the reaction of a hydrazino group or a protected hydrazino group with a carbonyl moiety. Exemplary hydrazino groups include aliphatic, aromatic, or heteroaromatic hydrazine groups, semicarbazide groups, carbazide groups, hydrazide groups, thiosemicarbazide groups, thiocarbazide groups, carbonic acid dihydrazine groups, or hydrazine carboxylate groups. See U.S. Patent No. 7,102,024. Oxime conjugation moieties can be formed by the reaction of an oxyamino group or a protected oxyamino group with a carbonyl moiety. Exemplary oxyamino groups are described below. Hydrazino and oxyamino groups can be protected by forming salts of the hydrazino or oxyamino group (including, but not limited to, mineral acid salts such as hydrochloride and sulfate, and salts of organic acids such as acetate, lactate, malate, tartrate, citrate, ascorbate, succinate, butyrate, valerate, and fumarate), or by any amino or hydrazino protecting group known to those skilled in the art (see, for example, Greene et al. (1999) Protective Groups in Organic Synthesis (3rd Edition) (J. Wiley Sons, Inc.)). The carbonyl moiety used to generate the Schiff base conjugation moiety is any carbonyl-containing group capable of forming a hydrazone or oxime bond with one or more of the above hydrazino or oxyamino moieties. Preferred carbonyl moieties include aldehydes and ketones, particularly aromatic aldehydes and ketones. In a preferred embodiment of the present disclosure, highly efficient conjugation moieties are formed by the reaction of an oxyamino-containing component with an aromatic aldehyde-containing component in the presence of an aniline catalyst (Dirksen et al. (2006) Angew. Chem. 45:7581-7584 (DOI: 10.1002 / anie.200602877)).

[0099] Alternatively, the highly efficient conjugation moieties of the present immunoreagents can be formed by a "click" reaction, e.g., the copper-catalyzed reaction of an azide-substituted component with an alkyne-substituted component to form a triazole conjugation moiety. See Kolb et al. (2001) Angew. Chem. Int. Ed. Engl. 40:2004; Evans (2007) Aus. J. Chem. 60:384. Copper-free variants of this reaction, e.g., strain-promoted azide-alkyne click reaction, can also be used to form highly efficient conjugation moieties. See, e.g., Baskin et al. (2007) Proc. Natl. Acad. Sci. USA 104:16793-97. Other click reaction variants include the reaction of tetrazine-substituted components with either isonitrile-substituted components (Stoeckmann et al. (2011) Org. Biomol. Chem. 9:7303) or strained alkene-substituted components (Karver et al. (2011) Bioconjugate Chem. 22:2263).

[0100] The basic features of the click reaction are well understood by those skilled in the art. See Kolb et al. (2001) Angew. Chem. Int. Ed. Engl. 40:2004. Useful click reactions generally include, but are not limited to, [3 + 2] cycloadditions, such as Huisgen 1,3-dipolar cycloadditions and, in particular, Cu(I)-catalyzed stepwise variants, thiol-ene click reactions, Diels-Alder reactions and inverse electron demand Diels-Alder reactions, [4 + 1] cycloadditions between isonitriles (isocyanides) and tetrazines, nucleophilic substitutions, carbonyl chemistry-like formation of ureas, and some addition reactions to carbon-carbon double bonds, especially to small strained rings such as epoxy and aziridine compounds. Any of the above reactions can be used, but are not limited to, to generate covalent, highly efficient conjugation moieties in the present immunoreagents.

[0101] In some embodiments, the conjugation moiety of the immunoreagent comprises a cleavable linker. Exemplary cleavable linkers usefully included in the high-efficiency conjugation moiety are known in the art. See, for example, Leriche et al. (2012) Bioorg. Med. Chem. 20:571-582 (doi:10.1016 / j.bmc.2011.07.048). Inclusion of a cleavable linker in the high-efficiency conjugation moiety allows for selective cleavage of the cross-linked antigen from the primary antibody in the immunoreagent. Such selective cleavage can be advantageous in some immunoassay methods, for example, in the release of the cross-linked antigen and its associated secondary antibody.

[0102] In other embodiments, the high-efficiency conjugation moiety is a non-covalent conjugation moiety. Non-limiting examples of non-covalent conjugation moieties include oligonucleotide hybridization pairs or protein-ligand binding pairs. In specific embodiments, the protein-ligand binding pair is an avidin-biotin pair, a streptavidin-biotin pair, or another protein-biotin binding pair (generally, see Avidin-Biotin Technology, Meth. Enzymol. (1990) Vol. 184, Academic Press; Avidin-Biotin Examples of suitable conjugates include antibody-hapten binding pairs (see, generally, Molecular Probes® Handbook, Chapter 4 (2010)), antibody-hapten binding pairs (see, generally, Molecular Probes® Handbook, Chapter 4 (2010)), S-peptide tag-S-protein binding pairs (Kim and Raines (1993) Protein Sci. 2:348-56), or any other high-affinity peptide-peptide or peptide-protein binding pairs. Such high-affinity noncovalent conjugation moieties are well known in the art. Reactive versions of each conjugate pair, such as thiol-reactive or amino-reactive versions, are also well known in the art. These conjugation reagents can be used to modify each antibody and cross-link antigen, optionally at multiple positions on the antibody. The modified antibody and cross-linked antigen can then be mixed to allow complementary forms, such as oligonucleotide hybridization pairs or protein-ligand binding pairs, to associate with each other and form non-covalent, high-efficiency conjugation moieties. The above-described covalent and non-covalent linking groups are capable of high-efficiency association reactions and are therefore well suited for use in making the present immunoreagents.

[0103] In some embodiments, a high-efficiency conjugation moiety is at least 50%, 80%, 90%, 93%, 95%, 97%, 98%, 99%, or even more efficient in coupling an antibody to a cross-linked antigen. In more specific embodiments, a high-efficiency conjugation moiety is at least 50%, 80%, 90%, 93%, 95%, 97%, 98%, 99%, or even more efficient at a protein concentration of 0.5 mg / mL or less. In some embodiments, efficiency is achieved at protein concentrations of 0.5 mg / mL or less, 0.2 mg / mL or less, 0.1 mg / mL or less, 0.05 mg / mL or less, 0.02 mg / mL or less, 0.01 mg / mL or less, or even lower. Because cross-linked antigens are typically used in greater amounts than antibodies in the preparation of the present immunoreagents, the efficiency of the ligation reaction is typically judged by the extent of conversion of the antibody component of the ligation reaction to immunoreagent product. For example, a highly efficient conjugation moiety that is at least 50% efficient in coupling antibodies to cross-linked antigens is one that results in at least 50% of the starting antibodies being converted in the association reaction into an immunoreagent with the desired number of cross-linked antigens per antibody.

[0104] In another aspect, the present disclosure provides an immunoreagent composition, also referred to as an immunoreagent panel, comprising a plurality of the above-described immunoreagents. In embodiments, the composition comprises at least 3, 5, 10, 20, 30, 50, 100, or even more immunoreagents. In some embodiments, the primary antibodies of the included immunoreagents are specific for cellular markers. In specific embodiments, the cellular markers are at least ER and PR. In other specific embodiments, the cellular markers are at least HER2, ER, and PR, or at least HER2, ER, and Ki67. In yet other specific embodiments, the cellular markers are at least HER2, ER, PR, and Ki67. In yet still other specific embodiments, the cellular markers are at least Ki67, EGFR, and CK5. In yet other specific embodiments, the cellular markers are at least Ki67, EGFR, CK5, and CK6, or at least CK5, CK6, and Ki-67. In yet other specific embodiments, the cell markers are at least CK5, EGFR, p40, and Ki-67, or at least IgA, complement 3c (C3c), collagen type IV alpha chain 5 (COL4A5), and IgG. In some embodiments, the cross-linking antigen of the included immunoreagent is a peptide.

[0105] In some embodiments, the immunoreagent compositions of the present disclosure are specific for cellular markers on immune cells, e.g., CD3, CD4, CD8, CD20, CD68, and / or FoxP3, in any combination, and any of the cellular markers listed above. In some embodiments, the immunoreagent compositions are specific for markers associated with checkpoint pathways, such as, for example, CTLA-4, CD152, PD-1, PD-L1, etc. Detectable secondary antibodies

[0106] As mentioned above, the bridging antigen of the present immunoreagents is recognizable by a detectable secondary antibody. To increase sensitivity and reduce background in immunoassays using the present immunoreagents, it is generally desirable to maximize the affinity and / or specificity of each detectable secondary antibody for its corresponding bridging antigen. As will be understood by those skilled in the art, the affinity of an antibody for an antigen is typically measured using an equilibrium parameter, the dissociation constant or "K D " For a given concentration of antibody, the dissociation constant roughly corresponds to the concentration of antigen where half the antibody is bound to the antigen and half the antibody is unbound. Thus, a lower dissociation constant corresponds to a higher affinity of the antibody for the antigen.

[0107] Dissociation constant also relates to the ratio of the kinetic rate constants for dissociation and association of antibody and antigen.Therefore, dissociation constant can be estimated either by equilibrium binding measurement or by reaction rate measurement.Such approaches are well known in the art.For example, antibody-antigen binding parameters are routinely determined from the kinetic analysis of sensorgrams obtained using Biacore surface plasmon resonance-based equipment (GE Healthcare, Little Chalfont, Buckinghamshire, UK), Octet biolayer interferometry system (Pall ForteBio Corp., Menlo Park, CA), etc.See, for example, US Patent Application Publication No. 2013 / 0331297, which describes the determination of the dissociation constants for a series of antibody clones and their corresponding peptide antigen binding partners.

[0108] Typical antibodies are used in concentrations ranging from micromolar to high nanomolar (i.e., 10 -6 M~10 -8 High affinity antibodies generally have equilibrium dissociation constants ranging from lower nanomolar to high picomolar concentrations (i.e., 10 -8 M~10 -10M). Ultra-high affinity antibodies generally have equilibrium dissociation constants in the picomolar range (i.e., 10 -10 M~10 -12 Antibodies to peptides or other large molecules typically have higher affinity (lower K M ) for their antigens than antibodies to small molecule haptens, which may exhibit dissociation constants in the micromolar range or even higher. D )

[0109] The secondary antibodies of the present immunoreagents can be optimized to increase their affinity for the antigen-coupled primary antibody. For example, U.S. Patent Application Publication No. 2013 / 0331297 discloses methods for identifying high-affinity antibody clones that can be appropriately modified to generate detectable secondary antibodies for use in the present immunoreagents. In these methods, short DNA fragments encoding synthetic peptides are fused to the heavy chains of a gene pool encoding the desired antibody library, and yeast cells are transformed to generate a yeast-display antibody library. The yeast cells are screened using a high-speed fluorescence-activated cell sorter (FACS) to isolate high-affinity antibody clones with high specificity. Compared to other yeast display systems, such as Aga2, this system has the added advantage that transformed yeast cells secrete sufficient amounts of antibody into the culture medium, allowing the specificity and affinity of the expressed antibody to be determined by directly assaying the culture medium of individual yeast clones, without requiring additional steps of cloning and antibody purification to identify candidate clones with the desired specificity and affinity.

[0110] The yeast display library system described above uses an antibody library generated from immunized rabbits to produce rabbit monoclonal antibodies with high specificity and affinity. It thus takes advantage of the superior ability of the rabbit immune system to generate antibodies against small haptens or peptides, along with the efficiency of yeast display to isolate antibody clones with excellent affinity and specificity. Using this approach, a panel of rabbit monoclonal antibodies against small molecules, peptides, and proteins has been generated with antibody affinities ranging from <0.01 to 0.8 nM. These affinities surpass those of most rodent-derived monoclonal antibodies generated using conventional hybridoma technology. The approach also overcomes the inherent problems of low fusion efficiency and poor stability encountered with rabbit hybridoma technology.

[0111] While the yeast display library system described above is one approach for optimizing the binding affinity of secondary antibodies used in the present immunoreagent compositions, it will be understood that any suitable approach can be used to optimize affinity, including, but not limited to, In some cases, a suitable high-affinity antibody may be available without optimization.

[0112] Thus, in some embodiments, the detectable secondary antibody is specific for the cross-linked antigen and has a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, at most 0.003 nM, or lower. In more specific embodiments, the detectable secondary antibody is specific for the cross-linked antigen and has a dissociation constant of at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, at most 0.003 nM, or lower. In even more specific embodiments, the detectable secondary antibody is specific for the cross-linked antigen and has a dissociation constant of at most 100 pM, at most 30 pM, at most 10 pM, at most 3 pM, or lower.

[0113] The secondary antibody of the present immunoreagent is a detectable secondary antibody, and therefore, in embodiments, it comprises a detectable label. As will be understood by those skilled in the art, the detectable label of the detectable secondary antibody should be capable of suitable binding to the antibody, and the binding should be carried out without significantly impairing the antibody's interaction with the cross-linked antigen.

[0114] In some embodiments, the detectable label may be directly detectable, such that it may be detected without the need for any additional components. For example, the directly detectable label can be a fluorescent dye, a biofluorescent protein, such as phycoerythrin, allophycocyanin, peridinin chlorophyll protein complex ("PerCP"), green fluorescent protein ("GFP"), or a derivative thereof (e.g., red fluorescent protein, cyan fluorescent protein, or blue fluorescent protein), luciferase (e.g., firefly luciferase, Renilla luciferase, genetically modified luciferase, or click beetle luciferase), or coral-derived cyan and red fluorescent proteins (as well as variants of coral-derived red fluorescent proteins, e.g., yellow, orange, and far-red variants), a luminescent species, including a chemiluminescent species, an electrochemiluminescent species, or a bioluminescent species, a phosphorescent species, a radioactive material, a nanoparticle, a SERS nanoparticle, a quantum dot or other fluorescent crystalline nanoparticle, a diffractive particle, a Raman particle, a metal particle, including a chelated metal, a magnetic particle, a microsphere, an RFID tag, a microbarcode particle, or a combination of these labels.

[0115] In other embodiments, the detectable label may be indirectly detectable, requiring the use of one or more additional components for detection. For example, an indirectly detectable label may be an enzyme that produces a color change in an appropriate substrate, or another molecule that can be specifically recognized by or react with another labeled substance. Non-limiting examples of suitable indirectly detectable labels include enzymes such as peroxidase, alkaline phosphatase, glucose oxidase, etc. In a specific embodiment, the peroxidase is horseradish peroxidase or soybean peroxidase. Other examples of indirectly detectable labels include haptens, such as small molecules or peptides. Non-limiting exemplary haptens include nitrophenyl, dinitrophenyl, digoxigenin, biotin, Myc tag, FLAG tag, HA tag, S tag, Streptag, His tag, V5 tag, ReAsh tag, FlAsh tag, biotinylated tag, Sfp tag, or another chemical or peptide tag.

[0116] In specific embodiments, the detectable label is a fluorescent dye.Non-limiting examples of suitable fluorescent dyes can be found in the catalogs of Life Technologies / Molecular Probes (Eugene, OR) and Thermo Scientific Pierce Protein Research Products (Rockford, IL), the entire contents of which are incorporated herein by reference.Exemplary dyes include fluorescein, rhodamine, and other xanthene dye derivatives, cyanine dyes and their derivatives, naphthalene dyes and their derivatives, coumarin dyes and their derivatives, oxadiazole dyes and their derivatives, anthracene dyes and their derivatives, pyrene dyes and their derivatives, and BODIPY dyes and their derivatives.Preferred fluorescent dyes include the DyLight fluorophore family available from Thermo Scientific Pierce Protein Research Products.

[0117] In some embodiments, the detectable label may not be directly attached to the secondary antibody, but may be attached to a polymer or other suitable carrier intermediate that allows for a larger number of detectable labels to be attached to the secondary antibody than would normally be attached.

[0118] In a specific embodiment, the detectable label is an oligonucleotide barcode tag, for example, the barcode tag disclosed in PCT International Patent Publication No. WO2012 / 071428A2 (the disclosure of which is incorporated herein by reference in its entirety). Such detectable labels are particularly advantageous in immunoassays involving targeted sample isolation and / or sorting, such as flow cytometry-based multiplexed immunodetection assays. These labels are also useful in immunoassays where the level of target antigen in the sample is low and the highest possible sensitivity of detection is required.

[0119] In some embodiments, detectable secondary antibodies of the present disclosure may comprise multiple detectable labels, in which the multiple detectable labels associated with a given secondary antibody may be multiple copies of the same label or a combination of different labels that produce an appropriate detectable signal.

[0120] In some immunoreagent embodiments, it may be advantageous to attach one or more detectable labels to the bridging antigen of the primary antibody to increase the signal output from the reagent. The detectable label usefully attached to the bridging antigen can be any of the detectable labels described above. Ideally, such detectable labels should overlap in detectability with the detectable label of the secondary antibody so that the signal from the primary and secondary antibody pair is additive. Furthermore, the attachment of the detectable label to the bridging antigen should ideally not significantly affect the binding of the secondary antibody to the bridging antigen on the primary antibody. Similarly, the binding of the secondary antibody to the bridging antigen should ideally not significantly affect the detectability of the detectable label.

[0121] In a preferred embodiment, the detectable label of the cross-linked antigen is a fluorophore. In a more preferred embodiment, the detectable label of the cross-linked antigen and the detectable label of the secondary antigen are both fluorophores. In another preferred embodiment, the detectable label of the cross-linked antigen and the detectable label of the secondary antibody are both detectable by fluorescence of the same wavelength. In yet another preferred embodiment, the detectable label of the cross-linked antigen and the detectable label of the secondary antibody are the same.

[0122] It is understood that the terms "primary antibody" and "secondary antibody" may be used in a slightly different manner in the context of this disclosure than they are sometimes applied in the field of immunological assays. Thus, the primary antibody should be broadly construed as targeting any molecule of interest, including other antibodies, and the secondary antibody should be broadly construed as targeting a bridging antigen when the bridging antigen is coupled to the primary antibody. In other contexts, an antibody that targets another antibody (e.g., from another species) may be considered a secondary antibody, but that antibody may be a primary antibody for purposes of this specification. Thus, the terms "primary antibody" and "secondary antibody" in this disclosure should be considered limiting only when the terms are used in the claims to distinguish one antibody from another. Immunoreagent Composition Pair

[0123] According to another aspect, the present disclosure provides immunoreagent compositions comprising a primary antibody coupled to a bridging antigen and a detectable secondary antibody specific for the bridging antigen. In these compositions, the detectable secondary antibody and the antigen-conjugated primary antibody are paired due to the high affinity of the secondary antibody for the bridging antigen. A paired composition is understood to be formed whenever the separate components of the composition are mixed together in aqueous solution, e.g., whenever the reagents are used together in an immunological assay.

[0124] Immunoreagents comprising a primary antibody and a coupled bridging antigen are described in detail above, as are suitable detectable secondary antibodies for use in this immunoreagent pair. As will be appreciated by those skilled in the art, compositions comprising these components find utility in performing immunological assays, including IHC, cytometry, flow cytometry, e.g., fluorescence activated cell sorting, microscopic imaging, pretargeted imaging, and other types of in vivo tumor and tissue imaging, high content screening (HCS), immunocytochemistry (ICC), immunomagnetic cellular depletion, immunomagnetic cell capture, sandwich assays, general affinity assays, enzyme immunoassays (EIAs), enzyme-linked immunoassays (ELISAs), ELISpot, mass cytometry (CyTOF), arrays including microsphere arrays, multiplexed microsphere arrays, microarrays, antibody arrays, cell arrays, liquid phase capture, lateral flow assays, chemiluminescence detection, infrared detection, blotting methods including Western blots, Southwestern blots, dot blots, tissue blots, etc., or combinations thereof. Multiplexed immunoreagent pairs

[0125] As mentioned above, current immunological assays are very limited in their ability to detect multiple antigens in a single sample due to the limited functionality of conventional secondary antibodies. As understood by those skilled in the art, antibodies directed against cross-species immunoglobulins are often used to label primary antibodies in the sample of interest in such immunological assays. The use of such cross-species secondary antibodies to detect primary antibodies in immunological assays provides some flexibility in the assay, since a single detectable cross-species secondary antibody can be used to stain a wide variety of unlabeled primary antibodies, as long as the primary antibodies are obtained from the same species. The use of cross-species secondary antibodies can also, in some situations, increase the sensitivity of the assay by amplifying the detectable signal: particularly if the secondary antibody is polyclonal and can bind to multiple epitopes, a single primary antibody may bind to multiple secondary antibodies, and the secondary antibody may be polymerized and / or carry multiple detectable labels. Such signal amplification can thereby increase the sensitivity of the assay for a given primary antibody. The use of a single detectable secondary antibody for multiple primary antibodies is also relatively convenient and inexpensive, as each primary antibody does not need to be individually labeled with a detection agent.

[0126] While the use of cross-species secondary antibodies offers several advantages in performing immunological assays, such use can be disadvantageous when primary antibodies for all target antigens of interest are not obtained from the same species. Additionally, the use of cross-species secondary antibodies also severely limits the multiplexing capabilities of conventional immunological assays, since only one primary antibody can be detected at a time in such assays. While it is possible to sequentially label the same tissue section or other sample of interest by sequential treatment with a first primary antibody, staining with a secondary antibody, bleaching or washing the sample to remove the detection agent, and repeating treatment with a second primary antibody, it is also possible to separately stain sequential tissue sections with a single-plexed reagent to evaluate multiple cell markers, such procedures are cumbersome, unreliable, and severely limited in the scale of possible multiplexing. The limitations of current multiplexing capabilities were recently reviewed by Stack et al. (2014) Methods 70:46-58 (DOI: 10.1016 / j.ymeth.2014.08.016).

[0127] The immunoreagents of the present disclosure overcome the above limitations by eliminating the need for cross-species secondary antibodies in multiplexed immunoassays. Instead, multiple pairs of immunoreagent compositions, each pair having a different bridging antigen and a corresponding different secondary antibody, can be used simultaneously in a single immunoassay to achieve high levels of multiplexing with high sensitivity, high specificity, and low background. The bridging antigen effectively acts in place of cross-species recognition of the primary antibody by the detectable secondary antibody. It should be understood that the choice of bridging antigen is limited only by the requirement that it be capable of coupling with the primary antibody of interest and be recognizable by the secondary antibody, ideally with high affinity. Because there are virtually unlimited bridging antigen structures that meet these criteria, the level of multiplexing possible using the present immunoreagents is similarly virtually unlimited. The only other limitation is that different detectable secondary antibodies must be detectably distinguishable from each other and from any other background signal in the sample in order to identify the target antigen in the assay. However, with the wide variety of detectable labels currently available for use in immunoassays, this requirement is not a significant limitation. Examples of fluorescent dyes useful for achieving high levels of multiplexing in fluorescence-based assays are described in Stack et al. (2014) Methods 70:46-58 (DOI: 10.1016 / j.ymeth.2014.08.016).

[0128] Thus, in embodiments, the present disclosure provides immunoreagent compositions comprising multiple primary antibodies coupled to multiple bridging antigens and multiple detectable secondary antibodies, where each bridging antigen in these compositions is coupled to a different primary antibody, and at least one detectable secondary antibody binds with high affinity to each bridging antigen. The multiple antigen-coupled primary antibodies and detectable secondary antibodies in these compositions can be any of the immunoreagent composition pairs described in the previous section.

[0129] In specific embodiments, the composition comprises at least three immunoreagent composition pairs. In more specific embodiments, the composition comprises at least five immunoreagent composition pairs. In even more specific embodiments, the composition comprises at least 10 immunoreagent composition pairs. In even more specific embodiments, the composition comprises at least 20, 30, 50, 100, or even more immunoreagent composition pairs. Immunoreagent Panel

[0130] The above-described immunoreagents can be combined into predefined groups to create diagnostic panels used to monitor the expression of specific combinations of cellular markers in specific tissues of interest, particularly diseased tissues of interest such as tumor tissues. Such panels are useful in diagnostic assays to identify such diseased tissues and are also useful as companion diagnostics, where the panel is used to monitor the levels of cellular markers in the diseased tissue over time during the course of a particular treatment regimen. Such companion diagnostics can provide a timely and reliable assessment of the effectiveness of a treatment regimen and further enable optimization of treatment dosage and frequency for a particular patient. As noted above, monitoring of target tissues using current IHC techniques is limited to one or two primary antibodies per tissue section or requires separate or sequential staining of tissue sections with different antibodies. In contrast, as described above, the immunoreagent panels disclosed herein allow for a high level of multiplexing, such that staining of a tissue or other sample of interest can be performed simultaneously with multiple primary antibodies in a single tissue section or other sample.

[0131] Thus, according to this aspect, the present invention provides an immunoreagent composition comprising at least three immunoreagents of the present disclosure. In specific embodiments, the immunoreagent composition comprises at least five, at least 10, at least 15, at least 20, at least 30, or even more immunoreagents of the present disclosure, as described in detail above.

[0132] Of particular interest is the use of this immunoreagent panel for profiling tissue samples from patients who are treated with immunotherapy regimens, for example, in the treatment of autoimmune diseases and cancer.Recent advances in blocking checkpoint pathways have been shown to be particularly effective, for example, by using antibodies (e.g., ipilimumab) that target cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4, CD152) or antibodies (e.g., pembrolizumab, nivolumab, pidilizumab, etc.) that target programmed death receptors or their ligands (PD-1 or PD-L1).See, for example, Adams et al. (2015) Nature Rev. Drug Discov. 14:603-22; Mahoney et al. (2015) Nature Rev. Drug Discov. 14:561-84; Shin et al. (2015) Curr. Opin. Immunol. 33:23-35.

[0133] Other recently approved anti-cancer drugs target other cell surface proteins or gene products that are upregulated or amplified in tumors and other diseases (see, e.g., rituximab against CD20 in lymphoma cells, trastuzumab against HER2 / neu in breast cancer cells, cetuximab against EGFR in various tumor cells, bevacizumab against VEGF in various cancer cells and in the eye, and denosumab against osteoclasts in bone). Thus, profiling of tissue samples from patients treated with these drugs is also of great current interest in clinical medicine.

[0134] Similarly, tissue samples obtained from patients either before or during treatment with anti-cancer drugs can also benefit from molecular profiling. For example, patients treated with imatinib, lenalidomide, pemetrexed, bortezomib, leuprorelin, abiraterone acetate, ibrutinib, capecitabine, erlotinib, everolimus, sirolimus, nilotinib, sunitinib, sorafenib, etc. can be advantageously monitored by profiling of tissues, particularly diseased tissues, using the present immunoreagent panels.

[0135] Also reported is the method and system for the molecular profiling of tissue, including the analysis of immune modulators, and the use of these profiles for evaluating and monitoring disease treatment.See, for example, United States Patent No. 8,700,335B2; United States Patent No. 8,768,629B2; United States Patent No. 8,831,890B2; United States Patent No. 8,880,350B2; United States Patent No. 8,914,239B2; United States Patent No. 9,053,224B2; United States Patent No. 9,058,418B2; United States Patent No. 9,064,045B2; United States Patent No. 9,092,392B2; PCT International Patent Publication No. WO2015 / 116868.This approach is advantageously carried out by using the appropriate panel of the present immune reagent.

[0136] Exemplary panels target combinations of tumor cell, immune cell, and various disease-associated marker antigens, including the following markers: 4-1BB, AFP, ALK1, amyloid A, amyloid P, androgen receptor, annexin A1, ASMA, BCA225, BCL-1, BCL-2, BCL-6, BerEP4, beta-catenin, beta-HCG, BG-8, BOB-1, CA19-9, CA125, calcitonin, caldesmon, calponin-1, calretinin, CAM5.2, CD1a, CD2, CD3, CD4, CD5, CD7, CD8, CD10, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD30, CD31, CD33, CD34, CD38, CD42b, CD43, CD45. LCA, CD45RO, CD56, CD57, CD61, CD68, CD79a, CD99, CD117, CD138, CD163, CDX2, CEA, chromogranin A, CMV, c-kit, c-MET, c-MYC, type IV collagen, complement 3c (C3c), COX-2, CXCR5, CK1, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK20, CK903, CKAE1, CK AE1 / AE3, D2-40, desmin, DOG-1, E-cadherin, EGFR, EMA, ER, ERCC1, factor VIII-related antigen, activated factor XIII, fascin, FoxP1, FoxP3, galectin-3, GATA-3, GCDFP-15, GCET1, GFAP, glycophorin A, glypican 3, granzyme B, HBME-1, Helicobacter pylori, hemoglobin A, Hep Par1, HER-2, HHV-8, HMB-45, HSV l / ll, ICOS, IFN gamma, IgA, IgD, IgG, IgM, IL17, IL4, inhibin, iNOS, kappa Ig light chain, Ki-67, LAG-3, lambda Ig light chain, lysozyme, mammaglobin A, MART-1 / MelanA, mast cell tryptase, MLH1, MOC-31, MPO, MSA, MSH2, MSH6, MUC1, MUC2, MUM1, MyoD1, myogenin, myoglobin, napsin A, nestin, NSE, Oct-2, OX40, OX40L, p16, p21, p27, p40, p53, p63, p504s, PAX-5, PAX-8, PD-1, PD-L1, PHH3, PIN-4, PLAP, PMS2, Pneumocystis jiroveci (carinii), PgR, PSA, PSAP, RCC, S-100, SMA, SMM, smoothelin, SOX10, SOX11, surfactant apoprotein A, synaptophysin, TAG72, TdT, thrombomodulin, thyroglobulin, TIA-1, TIM3, TRAcP, TTF-1, tyrosinase, uroplakin, VEGFR-2, villin, vimentin, and WT-1.

[0137] Preferably, the panel targets one or more of the following markers: CD4, CD8, CD20, CD68, PD-1, PD-L1, FoxP3, SOX10, Granzyme B, CD3, CD163, IL17, IL4, IFN gamma, CXCR5, FoxP1, LAG-3, TIM3, CD34, OX40, OX40L, ICOS, and 4-1BB.

[0138] The panel is provided either in the form of a kit or as a group of different immunoreagents provided separately for use in the methods for immunological assays described in detail below. In particular, the panel is used in a multiplexing method in which a sample is reacted with multiple immunoreagents for simultaneous detection. The immunoreagent may be any of the immunoreagents described above, in particular an immunoreagent comprising a primary antibody specific for any of the target antigens defined above and a bridging antigen, wherein the primary antibody and the bridging antigen are coupled and the bridging antigen is recognized with high affinity by a detectable secondary antibody.

[0139] In specific embodiments, the panel targets the following exemplary combinations of cellular markers: CD4, CD8, CD68, and PD-L1; CD4, CD8, FoxP3, and CD68 (for any solid tumor); CD8, CD68, PD-L1, plus tumor-associated markers (for head and neck tumors and pancreatic tumors); SOX10, CD8, PD-1, and PD-L1 (for melanoma); CD4, CD8, CD20, and cytokeratin (for breast cancer TILs); CD8, CD34, FoxP3, and PD-L1 (for melanoma immunology); CD8, CD34, PD-L1, and FoxP1 (for cancer immunology); CD3, PD1, LAG-3, and TIM3 (for T-cell exhaustion); CD4 and FoxP3 (for Tregs); CD4 and IL17 (for Th17); CD8 and granzyme B (for activated CD8); CD4 and CXCR5 (for TFh); CD4 and IL4 (for Th2); CD4 and IFNg (for Th1); CD4, CD8, CD3, and CD20 (for general lymphocytes); CD4, CD8, CD68, and CD20 (for lymphocytes and macrophages); CD4, FoxP3, CD8, and CD20 (for Tregs and lymphocytes); CD4, FoxP3, CD8, and Granzyme B (for Treg and Act CTLs); CD68 (for macrophages); CD68 and CD163 (for M2 macrophages); CD20 (for B cells); and OX40, OX40L, ICOS, and 41BB (for other molecules of interest). Immunological Assay Methods

[0140] In another aspect, the present disclosure provides methods of immunological assays comprising reacting an immunoreagent with a target antigen, reacting a detectable secondary antibody with the immunoreagent, wherein the detectable secondary antibody binds with high affinity to the bridging antigen of the immunoreagent, and detecting the bound detectable secondary antibody. The immunoreagent and detectable secondary antibody in these methods may usefully be any of the immunoreagents and detectable secondary antibodies described above, in any suitable combination.

[0141] In embodiments, the detection method is immunohistochemical method.As described above, immunohistochemical staining is a widely used technique that is frequently applied to the diagnosis of abnormal cells such as tumor cells.Specific molecular markers show the characteristics of specific tumor cells, such as breast cancer cells.IHC is also frequently used to understand the distribution and localization of biomarkers and differentially expressed proteins in different parts of biological tissues.

[0142] In specific embodiments, the target antigen is present in a tissue section. Detection of antigens in tissue sections is well understood by those skilled in the art of clinical pathology. Exemplary methods for detecting antigens in tissue sections include, for example, immunohistochemical staining. Methods, 6th edition (Dako / Agilent Technologies). It is understood that the solid tissue sample, typically after the fixation step, can be cut into thin slices to expose one or more target antigens of interest on the surface of the sample. Analysis of serial tissue sections, i.e., sections that were adjacent or nearly adjacent to each other in the original tissue sample, allows for the reconstruction of a three-dimensional model of the original tissue sample or increased capacity for multiplexing target antigens, as described in more detail below. In a preferred embodiment, the first target antigen is a target antigen in a tissue section of a tumor sample.

[0143] In other specific embodiments, the antigen detected by the method is within or on a cell. Such detection is well understood by those skilled in the art, for example, in the field of cytometry. In some embodiments, the antigen may be present on the surface of a cell. In other embodiments, the antigen may be present in the cytoplasm of a cell. In yet other embodiments, the antigen may be present in the nucleus of a cell. In some embodiments, the antigen may be present at more than one location within a cell.

[0144] The tissue to be analyzed according to the above method can be any suitable tissue sample. For example, in some embodiments, the tissue can be connective tissue, muscle tissue, nerve tissue, or epithelial tissue. Similarly, the tissue to be analyzed can be obtained from any organ of interest. Non-limiting examples of suitable tissues include breast, colon, ovary, skin, pancreas, prostate, liver, kidney, heart, lymphatic system, stomach, brain, lung, and blood.

[0145] In some embodiments, the detecting step is a fluorescent detection step. Suitable fluorescent detection labels are described in detail above.

[0146] In some embodiments, the method of detection further comprises sorting cells that are bound to the detectable secondary antibody. Cell sorting is a well-understood technique within the field of flow cytometry. Exemplary flow cytometry detection methods are described, for example, in Practical Flow Cytometry, 4th ed., Shapiro, Wiley-Liss, 2003; Handbook of Flow Cytometry Methods, edited by Robinson, Wiley-Liss, 1993; and Flow Cytometry in Clinical Diagnosis, 4th ed., Carey et al., eds., ASCP. Press, 2007. The use of hydrazone-linked antibody-oligonucleotide conjugates in quantitative multiplexed immunoassays, particularly quantitative flow cytometry assays, is described in PCT International Publication No. WO 2013 / 188756 and Flor et al. (2013) Chembiochem. 15:267-75.

[0147] In some embodiments, the immunological assay method includes reacting an additional immunoreagent with an additional target antigen in a multiplexed assay, where the additional immunoreagent is any of the immunoreagents defined above specific for the additional target antigen; reacting the additional immunoreagent with an additional detectable secondary antibody, where the additional detectable secondary antibody binds with high affinity to the bridging antigen of the additional immunoreagent; and detecting the bound detectable additional secondary antibody. The order of reaction of the additional immunoreagent and secondary antibody in a multiplexed method can be varied in any suitable manner to achieve the desired results, as will be understood by those skilled in the art. In some embodiments, all of the different immunoreagents can be added simultaneously to a target sample containing multiple target antigens. In other embodiments, the different immunoreagents can be added sequentially in any order. Similarly, the secondary antibodies can be added either simultaneously or sequentially in any order. In a multiplexed assay, the method can detect 2, 3, 5, 10, 20, 30, 50, 100, or even more different target antigens in a single assay. As described in detail above, the ability of the present immunoreagents to be used in such higher level multiplexed immunoassays is a major advantage of the present immunoreagents. In particular, and as illustrated in the Examples, these immunoreagents enable immunoassays with excellent sensitivity, selectivity, and extremely low levels of background signal.

[0148] In some embodiments, the immunoassay method includes analyzing adjacent or nearly adjacent sections of a fixed tissue sample to increase the level of detectable antigen multiplexing possible for a given tissue sample or to reconstruct a three-dimensional image of the sample. For example, in some embodiments, the method further includes reacting a second immunoreagent with a second target antigen on the second sample. In some of these methods, the first and second samples can be consecutive sections of the tissue sample (i.e., sections that are adjacent or nearly adjacent to each other in the sample), and the second immunoreagent is any of the immunoreagents described above that is specific for the second antigen. The method further includes reacting a second detectable secondary antibody with the second immunoreagent, where the second detectable secondary antibody has high affinity and specificity for the bridging antigen of the second immunoreagent, and detecting the second detectable secondary antibody associated with the bridging antigen of the second immunoreagent.

[0149] It is understood that immunoassays of serial sections of a given tissue sample offer a significant increase in the multiplexing of antigen detection, even considering the limitations of current hardware and software. For example, while the immunoreagents and methods described herein, in principle, allow for unlimited multiplexing due to the unlimited variation of bridging antigens and secondary antibodies, such assays are still limited by the number of fluorescent dyes that can be simultaneously distinguished on a single tissue section with currently available detection devices. However, serial sections of the same tissue sample can be stained with different panels of primary antibodies to identify different sets of target antigens by reusing the same panel of detectable labels, e.g., fluorescent labels, on different sections. The detectable labels can be bound to the same set of secondary antibodies used to label the first sample section, in which case the second panel of primary antibodies is labeled with the same set of bridging antigens used with the first panel of antibodies. Alternatively, and optionally, the detectable label may be attached to a different set of secondary antibodies than was used to label the first sample section, in which case the second panel of primary antibodies is labeled with a different set of bridging antigens than was used with the first panel of antibodies.

[0150] It is also understood that the immunoassay of the serial section of a given tissue sample allows the analysis of target tissue antigen in three dimensions, and thus provides further information about the overall structure of sample tissue, for example, by tomography technology.In some embodiments, the first sample and the second sample can be separated in space within the first tissue, instead of being serial sections of the sample, and therefore provide further information about the relative spatial arrangement of target antigen in three dimensions.Those skilled in the art will understand the use of serial section images in reconstructing three-dimensional tissue structure.

[0151] In some embodiments, multiple target antigens are detected in each sample.In specific embodiments, at least 2 target antigens, at least 3 target antigens, at least 5 target antigens, at least 10 target antigens, at least 15 target antigens, at least 25 target antigens, or even more target antigens are detected in each sample.In some embodiments, one or more target antigens are detected in at least 3 samples, at least 4 samples, at least 5 samples, at least 10 samples, at least 15 samples, at least 25 samples, or even more samples.

[0152] In another aspect, the present disclosure provides a method of immunoassay in which multiple target antigens in a sample are labeled by first treating with a primary antibody containing a bridging antigen, followed by subsequent sequential treatment with a reactive secondary antibody specific to the bridging antigen. Specifically, a sample containing a first target antigen and a second target antigen is reacted with a first immunoreagent specific to the first target antigen and a second immunoreagent specific to the second target antigen, where the first immunoreagent and the second immunoreagent are any of the immunoreagents described above. The first immunoreagent is reacted with a first reactive secondary antibody, where the first reactive secondary antibody binds with high affinity to the bridging antigen of the first immunoreagent. The location of the first antigen in the sample is then highlighted by reacting the first reactive secondary antibody with a first detectable reagent, thereby binding the first detectable reagent to the sample in the vicinity of the first antigen. The first reactive secondary antibody is then selectively dissociated from the sample, and the second immunoreagent is reacted with the second reactive secondary antibody, where the second reactive secondary antibody binds with high affinity to the bridging antigen of the second immunoreagent.Then, the location of the second antigen in the sample is highlighted by reacting the second reactive secondary antibody with a second detectable reagent, whereby the second detectable reagent is bound to the sample near the second antigen.Then, the first detectable reagent and the second detectable reagent are detected, and the locations of the first target antigen and the second target antigen in the sample are identified accordingly.

[0153] In specific embodiments of these methods, the first reactive secondary antibody and the second reactive secondary antibody each comprise an enzymatic activity, more specifically, a peroxidase activity such as horseradish peroxidase activity. In other specific embodiments, either the first detectable reagent or the second detectable reagent comprises a tyramide, or each of the first detectable reagent and the second detectable reagent comprises a tyramide. In yet other specific embodiments, either the first detectable reagent or the second detectable reagent comprises a fluorophore or chromophore, or each of the first detectable reagent and the second detectable reagent comprises a fluorophore or chromophore.

[0154] In a preferred embodiment, the first reactive secondary antibody is dissociated from the sample by selective treatment. Specifically, the selective treatment can dissociate the first reactive secondary antibody from the sample without dissociating the primary antibody from the sample. More specifically, the selective treatment can include treatment with a soluble cross-linking antigen. As understood by those skilled in the art, such treatment can include the use of a relatively high concentration of soluble cross-linking antigen, for example, at least 1 μM, at least 10 μM, at least 100 μM, at least 1 mM, at least 10 mM, or even higher concentrations of soluble cross-linking antigen.

[0155] It is also understood that in the above methods, the steps of dissociating the reactive secondary antibody from the sample, reacting the additional immunoreagent with the additional target antigen on the sample, reacting the additional reactive secondary antibody with the additional immunoreagent, and reacting the additional reactive secondary antibody with the additional detectable reagent, such that the additional detectable reagent is bound to the sample near the additional target antigen, can be repeated as many times as needed to detect the location of as many target antigens on the sample as desired. In some embodiments, the steps are repeated to detect the location of at least 3 target antigens, at least 4 target antigens, at least 5 target antigens, at least 10 target antigens, or even more target antigens on the sample.

[0156] It should also be understood that the order of steps used in these assay methods may depend on the specific reaction conditions used, and that in some cases, additional reaction steps may also be necessary to complete the assay. For example, if a non-selective method (e.g., heat, denaturation, etc.) is used to dissociate reactive secondary antibodies from the sample, it may be necessary to include additional reaction steps in the assay. Specifically, if the dissociation conditions also remove the primary antibody from the sample, a further reaction with an additional immunoreagent may be included in the step before reaction with the additional reactive secondary antibody and additional detectable reagent. In other words, a reaction of a new immunoreagent with a new target antigen is included in the step for each target antigen. However, in a preferred embodiment, if the reactive secondary antibodies selectively dissociate, all of the desired immunoreagents for reaction with all of the desired target antigens can be added in the first reaction step, and only the reactive secondary antibodies are added in subsequent cycles. The use of selective treatment to dissociate reactive secondary antibodies from the sample minimizes damage to the sample from harsh treatment, thereby improving the results from the assay.

[0157] The immunoreagents of the present disclosure can be usefully employed in a variety of immunochemical detection methods, including, but not limited to, microscopic imaging, pretargeted imaging, and other types of in vivo tumor and tissue imaging, high-content screening (HCS), immunocytochemistry (ICC), immunomagnetic cell depletion, immunomagnetic cell capture, sandwich assays, general affinity assays, enzyme immunoassays (EIAs), enzyme-linked immunoassays (ELISAs), ELISpot, mass cytometry (CyTOF), arrays including microsphere arrays, multiplexed microsphere arrays, microarrays, antibody arrays, and cell arrays, liquid-phase capture, lateral flow assays, chemiluminescent detection, infrared detection, blotting methods including Western blots, Southwestern blots, dot blots, tissue blots, etc., or combinations thereof. Each of these assays can benefit from the high level of multiplexing achieved using the present immunoreagents.

[0158] The target antigen recognized by the antibody of the present immunoreagent can be, for example, any polypeptide antigen, such as a cellular protein of interest or another antibody, or a small molecule antigen, e.g., a hapten. Other antigens can also be usefully targeted by the present immunoreagent, as will be understood by those of skill in the art. For example, targets of the present immunoreagents include proteins, microorganisms, viruses, bacteria, drugs, hormones, toxins, biomolecules, lipids, carbohydrates, nucleic acids, synthetic molecules, modified proteins, and the like.

[0159] The above methods are used, without limitation, in research and clinical practice. They can be used for diagnostic purposes, including predictive screening, and in other types of prognostic assays, for example, in a diagnostic laboratory setting or as point-of-care rapid tests. The multiplexed antibody technology is also well suited for use in high-throughput screening. Method of preparation

[0160] In another aspect, the present disclosure provides novel methods for preparing antigen-coupled immunoreagents, such as those described above. In some embodiments, the methods include coupling a primary antibody to a cross-linked antigen using a chemical coupling reaction. In specific embodiments, the primary antibody and the cross-linked antigen are coupled by a high-efficiency conjugation moiety. In some embodiments, the methods include modifying the antibody with a first conjugation reagent, modifying the cross-linked antigen with a second conjugation reagent, and reacting the modified antibody with the modified cross-linked antigen to produce the antigen-coupled immunoreagent. In specific embodiments, the first conjugation reagent and the second conjugation reagent associate with each other with high efficiency.

[0161] High efficiency means that the efficiency of conversion of antibody to antigen-coupled antibody is at least 50%, 70%, 90%, 95%, or 99% complete under the conditions of the conjugation reaction, hi some embodiments, these efficiencies are achieved at protein concentrations of 0.5 mg / mL or less, 0.2 mg / mL or less, 0.1 mg / mL or less, 0.05 mg / mL or less, 0.02 mg / mL or less, 0.01 mg / mL or less, or even lower.

[0162] The antibody and cross-linked antigen usefully used in the preparation method include any of the above-mentioned antibodies and cross-linked antigens.The first and second conjugation reagents are selected according to the desired result.In particular, high-efficiency conjugation reagents that can specifically and selectively react with amino groups or thiol groups are particularly useful in the modification of peptides and proteins, such as antibodies and peptide cross-linked antigens.In addition, the first and second conjugation reagents are selected for their ability to associate with each other with high efficiency, and therefore, their ability to generate high-efficiency conjugation moieties in the part of the immunoreagent that is coupled with the above-mentioned antigen.

[0163] As described above, the resulting conjugation moiety can be a covalent or non-covalent moiety, and the first and second conjugation reagents used to prepare the modified antibody and modified cross-linked antigen are selected accordingly. For example, in the case of a non-covalent conjugation moiety, the first conjugation reagent preferably contains a selectively reactive group for binding the reagent to a specific reactive residue of the antibody and the first component of the conjugation pair. Similarly, the second conjugation reagent preferably contains a selectively reactive group for binding the reagent to a specific reactive residue of the cross-linked antigen and the second component of the conjugation pair. The first and second components of the conjugation pair can non-covalently associate with each other with high efficiency, thereby producing an antigen-coupled immunoreagent.

[0164] As mentioned above, examples of non-covalent conjugation moieties include oligonucleotide hybridization pairs and protein-ligand binding pairs.For example, in the case of oligonucleotide hybridization pairs, antibody is reacted with the first conjugation reagent that comprises one member of hybridization pair, and bridging antigen is reacted with the second conjugation reagent that comprises the second member of hybridization pair.Therefore, modified antibody and modified bridging antigen can be mixed with each other, and the association of the two members of hybridization pair produces high-efficiency conjugation moieties.

[0165] Similarly, when a protein-ligand binding pair is used to generate the non-covalent conjugation portion of an antigen-coupled immunoreagent, the antibody is reacted with a first conjugation reagent containing one or the other of the protein-ligand pair, and the cross-linked antigen is reacted with a second conjugation reagent containing the complementary member of the protein-ligand pair. The thus-modified antibody and cross-linked antigen are then mixed with each other to generate a highly efficient conjugation portion.

[0166] As described in detail above, examples of highly efficient covalent conjugation moieties include hydrazones, oximes, other Schiff bases, and the products of various click reactions. Exemplary hydrazino, oxyamino, and carbonyl conjugate reagents used to form highly efficient conjugation moieties are illustrated in U.S. Patent No. 7,102,024 and can be adapted for use in the present reaction method. As described therein, the hydrazine moiety can be an aliphatic, aromatic, or heteroaromatic hydrazine, semicarbazide, carbazide, hydrazide, thiosemicarbazide, thiocarbazide, dihydrazine carbonate, or hydrazine carboxylate. The carbonyl moiety can be any carbonyl-containing group capable of forming a hydrazine or oxime bond with one or more of the above hydrazine or oxyamino moieties. Preferred carbonyl moieties include aldehydes and ketones. Activated versions of some of these reagents used as conjugation reagents in the present methods are commercially available, for example, from Solulink, Inc. (San Diego, CA) and Jena Bioscience GmbH (Jena, Germany). In some embodiments, the reagents can be incorporated into the cross-linked antigen during synthesis of the antigen, for example, during synthesis of the peptide cross-linked antigen by solid phase synthesis.

[0167] The incorporation of hydrazine-, oxyamino-, and carbonyl-based monomers into oligonucleotides, which are used for immobilization and other conjugation reactions, is described in U.S. Patent No. 6,686,461; U.S. Patent No. 7,173,125; and U.S. Patent No. 7,999,098.The hydrazine-based and carbonyl-based bifunctional cross-linking reagents used for the conjugation and immobilization of biomolecules are described in U.S. Patent No. 6,800,728.The use of highly efficient bisaryl-hydrazone linkers for forming oligonucleotide conjugates in various detection assays and other applications is described in PCT International Publication No. WO2012 / 071428.Each of the above-mentioned references is incorporated herein by reference in its entirety.

[0168] In some embodiments, the immunoreagents of the present disclosure are prepared using novel conjugate reagents and conditions. For example, thiol-reactive maleimidooxyamino (MOA) conjugate reagents useful for preparing antigen-coupled immunoreagents can be prepared as shown in Scheme 1: [ka] Amino-reactive oxyamino conjugate reagents (AOA) can be prepared as shown in Scheme 2: [ka]

[0169] Alternative thiol-reactive and amino-reactive conjugate reagents can be prepared using variations of the above reaction schemes, as would be understood by one skilled in the art of synthetic chemistry, and such alternative reagents should be considered within the scope of the preparative methods disclosed herein.

[0170] Antibodies and cross-linked antigens modified using one or other of the above oxyamino-containing reagents can be usefully reacted with complementary antibodies or cross-linked antigens that are themselves modified with a carbonyl-containing reagent, e.g., an aromatic aldehyde such as a formylbenzoate group. Alternative examples of such conjugation reactions are shown in Schemes 3 and 4 (where the R and R groups independently represent the antibody or cross-linked antigen). [ka]

[0171] It should be understood that the relative orientation of different members of the groups forming the conjugation moiety on the antibody and the cross-linked antigen is generally not considered important, as long as the groups can react with each other to form a highly efficient conjugation moiety. In other words, in the examples of Schemes 3 and 4, the R1 group can be the antibody and the R2 group can be the cross-linked antigen, or the R1 group can be the cross-linked antigen and the R2 group can be the antibody. The same generally applies to all of the above conjugate pairs, whether covalent or non-covalent. The peptides shown in Table 1 of the Examples are conjugated to a primary antibody using the reaction shown in Scheme 4, where the AOA group is attached at the amino terminus of the peptide, the "R1" group corresponds to the peptide, and the "R2" group is the antibody.

[0172] The conjugation methods described above offer several advantages over conventional cross-linking methods, such as those using bifunctional cross-linking reagents. In particular, the reaction is specific, efficient, and stable. Specificity means that side reactions, such as homoconjugation reactions, do not occur or occur at extremely low levels. Efficiency means that the reaction proceeds to completion or near completion even at low protein concentrations, thus yielding products in or near stoichiometric amounts. The stability of the conjugated moieties formed means that the resulting immunoreagents can be used for a wide variety of purposes without concern that the conjugated product will dissociate during use. In some cases, the conjugation methods described above offer the additional advantage that a chromophore is formed as the reaction occurs in part of the reaction, allowing the progress of the conjugation reaction to be monitored spectroscopically.

[0173] The synthesis and stability of hydrazone-linked adriamycin / monoclonal antibody conjugates are described in Kaneko et al. (1991) Bioconj. Chem. 2:133-41. The synthesis and protein modification properties of a series of aromatic hydrazides, hydrazines, and thiosemicarbazides are described in U.S. Patent Nos. 5,206,370; 5,420,285; and 5,753,520. The preparation of conjugatively extended hydrazine compounds and fluorescent hydrazine compounds is described in U.S. Patent No. 8,541,555. diagnostic kits

[0174] In another aspect, the present disclosure provides kits for use in immunochemical assays for diagnostic or research purposes. The diagnostic kits include one or more immunoreagents of the present disclosure along with instructions for use in immunoassays. In some embodiments, the kits further include a secondary antibody, e.g., a secondary antibody with high affinity and specificity for the bridging antigen of the immunoreagent. Furthermore, the immunoreagents included in the kits typically include antibodies directed against cellular markers, thereby understanding that the kits can be used in immunoassays for detecting cellular markers within tissue samples, in cell suspensions, on other surfaces, or in other media. However, in some situations, it may be useful to provide immunoreagents that include antibodies directed against cross-species immunoglobulins, such as anti-mouse antibodies, anti-rabbit antibodies, etc. In these kits, the immunoreagents can be used in immunoassays for detecting primary antibodies of the target species.

[0175] In further embodiments, the kit may include additional components, such as buffers of various compositions to enable use of the kit for staining cells or tissues, cellular counterstains to enable visualization of sample morphology, etc. Kits may be provided in a variety of formats and may include some or all of the above-listed components, or may include additional components not listed herein. Alternative Binders

[0176] In another embodiment of the present disclosure, the primary antibody component of the immunoreagent can be replaced with another agent capable of binding to the target antigen with high affinity. For example, aptamers are single-stranded DNA or RNA oligomers that can form various tertiary structures and bind to targets such as metal ions, small molecules, proteins, viruses, and cells. See Ma et al. (2015) Chem. Soc. Rev. (DOI: 10.1039 / C4CS00357H). Aptamers with high affinity and specificity for a given target molecule can be selected from random libraries using a procedure known as Sytematic Evolution of Ligands by Exponential Enrichment (SELEX), as understood by those skilled in the art. Once identified and characterized, suitable aptamers can be further modified, for example, by adding labels or other desired modifications. For example, see Wang et al. (2011) Curr. Med. Chem. for a review of aptamer-based fluorescent biosensors. See Vol. 18: pp. 4175-4184.

[0177] The immunoreagents of the present disclosure may advantageously employ aptamers, or other similar high affinity and high selectivity binding agents, by coupling these agents to a cross-linked antigen, as described above for immunoreagents prepared from more conventional antibodies. Thus, for purposes of this disclosure, it will be understood that aptamers, as well as other related high affinity and high selectivity binding agents, as understood by those of skill in the art, should be considered to fall within the scope of the term "antibody" as used and claimed herein due to the aptamer's ability to specifically recognize and bind to a particular target molecule on a sample.

[0178] Thus, in some embodiments, the immunoreagents of the present disclosure comprise: Aptamers and cross-linked antigen wherein the aptamer and the cross-linked antigen are coupled; The cross-linked antigen is recognized with high affinity by a detectable secondary antibody. In specific embodiments, the immunoreagent comprises one or more of the features of the immunoreagents described above, including conventional antibodies. Other Aspects

[0179] In other aspects, the present disclosure provides the features described in the following numbered paragraphs: 1. A primary antibody coupled to a bridging antigen; and Detectable secondary antibodies wherein said detectable secondary antibody is high affinity and specific for said cross-linked antigen. 2. The immunoreagent composition of paragraph 1, wherein the cross-linked antigen is a peptide or a small molecule hapten. 3. The immunoreagent composition described in paragraph 1, wherein the primary antibody and the bridging antigen are coupled by a chemical coupling reaction. 4. The immunoreagent composition of paragraph 1, wherein the primary antibody and the bridging antigen are coupled by a high-efficiency conjugation moiety. 5. The immunoreagent composition of paragraph 4, wherein the high efficiency conjugation moiety is a Schiff base. 6. The immunoreagent composition of paragraph 5, wherein the Schiff base is a hydrazone or oxime. 7. The immunoreagent composition of paragraph 4, wherein the high efficiency conjugation moiety is formed by a click reaction. 8. The immunoreagent composition of paragraph 1, wherein the primary antibody is specific for a cell marker. 9. The immunoreagent composition of paragraph 8, wherein the cell marker is selected from the group consisting of ER, HER2, PR, Ki67, EGFR, CK1, CK5, CK6, CK7, CK14, CK17, cytokeratin AE1 / AE3, nestin, vimentin, ASMA, Ber-EP4, p16, p40, p53, p63, c-kit and CD markers. 10. The immunoreagent composition of paragraph 1, wherein the primary antibody is specific for an immunoglobulin from a different species. 11. The immunoreagent composition of paragraph 1, wherein the detectable secondary antibody comprises a detectable label. 12. The immunoreagent composition of paragraph 11, wherein the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten. 13. The immunoreagent composition of paragraph 12, wherein the detectable label is a fluorophore. 14. The immunoreagent composition of paragraph 12, wherein the enzyme is peroxidase, alkaline phosphatase, or glucose oxidase. 15. The immunoreagent composition of paragraph 14, wherein the peroxidase is horseradish peroxidase or soybean peroxidase. 16. The immunoreagent composition of paragraph 1, wherein the detectable secondary antibody is specific for the cross-linked antigen and has a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, or at most 0.003 nM. 17. Multiple primary antibodies coupled to multiple bridging antigens, and Multiple detectable secondary antibodies wherein each bridging antigen is coupled to a different primary antibody, and at least one detectable secondary antibody is high affinity and specific for at least one of the bridging antigens. 18. The immunoreagent composition of paragraph 17, wherein each cross-linked antigen is a peptide or a small molecule hapten. 19. The immunoreagent composition of paragraph 17, wherein the plurality of primary antibodies and the plurality of cross-linking antigens are coupled by a chemical coupling reaction. 20. The immunoreagent composition of paragraph 17, wherein the plurality of primary antibodies and the plurality of cross-linking antigens are coupled by a high-efficiency conjugation moiety. 21. The immunoreagent composition of paragraph 20, wherein the high efficiency conjugation moiety is a Schiff base. 22. The immunoreagent composition of paragraph 21, wherein the Schiff base is a hydrazone or oxime. 23. The immunoreagent composition of paragraph 20, wherein the high efficiency conjugation moiety is formed by a click reaction. 24. The immunoreagent composition of paragraph 17, wherein the multiple primary antibodies are specific for multiple cell markers. 25. The immunoreagent composition of paragraph 24, wherein the cell marker is selected from the group consisting of ER, HER2, PR, Ki67, EGFR, CK1, CK5, CK6, CK7, CK14, CK17, cytokeratin AE1 / AE3, nestin, vimentin, ASMA, Ber-EP4, p16, p40, p53, p63, c-kit and CD markers. 26. The immunoreagent composition of paragraph 17, wherein the multiple primary antibodies are specific for multiple immunoglobulins from different species. 27. The immunoreagent composition of paragraph 17, wherein the plurality of detectable secondary antibodies comprises a detectable label. 28. The immunoreagent composition of paragraph 27, wherein the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten. 29. The immunoreagent composition of paragraph 28, wherein the detectable label is a fluorophore. 30. The immunoreagent composition of paragraph 28, wherein the enzyme is peroxidase, alkaline phosphatase, or glucose oxidase. 31. The immunoreagent composition according to paragraph 30, wherein the peroxidase is horseradish peroxidase or soybean peroxidase. 32. The immunoreagent composition of paragraph 17, wherein the at least one detectable secondary antibody is specific for the at least one cross-linked antigen and has a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, or at most 0.003 nM. 33. The immunoreagent composition of paragraph 17, wherein each detectable secondary antibody is high affinity and specific for each cross-linked antigen. 34. The immunoreagent composition of paragraph 17, comprising at least three different cross-linking antigens. 35. The immunoreagent composition of paragraph 34, comprising at least five different cross-linking antigens. 36. The immunoreagent composition of paragraph 35, comprising at least 10 different cross-linked antigens. 37. Primary antibodies, and cross-linked antigen an immunoreagent comprising a primary antibody and a bridging antigen coupled together, An immunoreagent in which the cross-linked antigen is recognized with high affinity by a detectable secondary antibody. 38. The immunoreagent of paragraph 37, wherein the cross-linked antigen is a peptide. 39. The immunoreagent according to paragraph 37, wherein the primary antibody and the bridging antigen are coupled by a chemical coupling reaction. 40. The immunoreagent of paragraph 37, wherein the primary antibody and the bridging antigen are coupled by a high-efficiency conjugation moiety. 41. The immunoreagent of paragraph 40, wherein the high efficiency conjugation moiety is a Schiff base. 42. The immunoreagent of paragraph 41, wherein the Schiff base is a hydrazone or oxime. 43. The immunoreagent of paragraph 40, wherein the high efficiency conjugation moiety is formed by a Click reaction. 44. The immunoreagent according to paragraph 37, wherein the primary antibody is specific for a cell marker. 45. The immunoreagent according to paragraph 44, wherein the cell marker is selected from the group consisting of ER, HER2, PR, Ki67, EGFR, CK1, CK5, CK6, CK7, CK14, CK17, cytokeratin AE1 / AE3, nestin, vimentin, ASMA, Ber-EP4, p16, p40, p53, p63, c-kit and CD markers. 46. ​​The immunoreagent according to paragraph 37, wherein the primary antibodies are specific for immunoglobulins from different species. 47. The immunoreagent of paragraph 37, wherein the cross-linked antigen is recognized by the detectable secondary antibody with a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, or at most 0.003 nM. 48. An immunoreagent composition comprising at least three immunoreagents according to any one of paragraphs 37 to 47. 49. An immunoreagent composition according to paragraph 48, comprising at least 5 immunoreagents according to any one of paragraphs 37 to 47. 50. An immunoreagent composition according to paragraph 48, comprising at least 10 immunoreagents according to any one of paragraphs 37 to 47. 51. The immunoreagent composition of paragraph 48, wherein the primary antibody is specific for multiple cell markers. 52. The immunoreagent composition of paragraph 51, wherein the cell marker is selected from the group consisting of ER, HER2, PR, Ki67, EGFR, CK1, CK5, CK6, CK7, CK14, CK17, cytokeratin AE1 / AE3, nestin, vimentin, ASMA, Ber-EP4, p16, p40, p53, p63, c-kit and CD markers. 53. The immunoreagent composition of paragraph 48, wherein the cross-linked antigen is a peptide. 54. Providing a sample containing a first target antigen; reacting a first immunoreagent with the first target antigen, wherein the first immunoreagent is the immunoreagent of any one of paragraphs 37 to 47, which is specific for the first target antigen; reacting a first detectable secondary antibody with the first immunoreagent, the first detectable secondary antibody being high affinity and specific for the cross-linked antigen of the first immunoreagent; and detecting the first detectable secondary antibody associated with the bridging antigen of the first immunoreagent. 1. A method for immunological assays comprising: 55. The method of paragraph 54, wherein the first target antigen is a cell marker. 56. The method of paragraph 55, wherein the cell marker is selected from the group consisting of ER, HER2, PR, Ki67, EGFR, CK1, CK5, CK6, CK7, CK14, CK17, cytokeratin AE1 / AE3, nestin, vimentin, ASMA, Ber-EP4, p16, p40, p53, p63, c-kit and CD markers. 57. The method of paragraph 54, wherein the first target antigen is an immunoglobulin from a different species. 58. The method of paragraph 54, wherein the first detectable secondary antibody comprises a detectable label. 59. The method of paragraph 58, wherein the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten. 60. The method of paragraph 59, wherein the detectable label is a fluorophore. 61. The method of paragraph 59, wherein the enzyme is peroxidase, alkaline phosphatase, or glucose oxidase. 62. The method of paragraph 61, wherein the peroxidase is horseradish peroxidase or soybean peroxidase. 63. The method of paragraph 54, wherein the first detectable secondary antibody is specific for the bridging antigen of the first immunoreagent and has a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, or at most 0.003 nM. 64. The method of paragraph 54, wherein the first target antigen is in a tissue section. 65. The method of paragraph 64, wherein the detecting step is a fluorescence detection step. 66. The method of paragraph 64, wherein the detecting step is an enzymatic detection step. 67. The method of paragraph 54, wherein the first target antigen is in or on a cell. 68. The method of paragraph 67, wherein the first target antigen is on the surface of the cell. 69. The method of paragraph 67, wherein the first target antigen is in the cytoplasm of the cell. 70. The method of paragraph 67, wherein the first target antigen is in the nucleus of the cell. 71. The method of paragraph 67, wherein the detecting step is a fluorescence detection step. 72. The method of claim 71, further comprising sorting cells that bind to the first detectable secondary antibody. 73. Reacting a second immunoreagent with a second target antigen in the sample, wherein the second immunoreagent is an immunoreagent according to any one of paragraphs 37 to 47 that is specific for the second antigen; reacting the second immunoreagent with a second detectable secondary antibody, the second detectable secondary antibody being high affinity and specific for the cross-linked antigen of the second immunoreagent; and detecting the second detectable secondary antibody associated with the bridging antigen of the second immunoreagent. 55. The method of paragraph 54, further comprising: 74. The method of paragraph 73, further comprising detecting at least three target antigens in the sample. 75. The method of paragraph 74, further comprising detecting at least five target antigens in the sample. 76. The method of paragraph 75, further comprising detecting at least 10 target antigens in the sample. 77. Providing a sample containing a first target antigen; reacting a first primary antibody with the first target antigen, wherein the first primary antibody is specific to the first target antigen; reacting a first immunoreagent with the first primary antibody, wherein the first immunoreagent is the immunoreagent of any one of paragraphs 37 to 47, which is specific for the first primary antibody; reacting a first detectable secondary antibody with the first immunoreagent, the first detectable secondary antibody being high affinity and specific for the cross-linked antigen of the first immunoreagent; and detecting the first detectable secondary antibody associated with the bridging antigen of the first immunoreagent. 1. A method for immunological assays comprising: 78. An immunoreagent according to any one of paragraphs 37 to 47. a high affinity, specific, detectable secondary antibody against the cross-linked antigen; and Instructions for using the kit A kit for an immunological assay comprising: 79. The kit of paragraph 78, wherein the detectable secondary antibody comprises a detectable label. 80. The kit of paragraph 79, wherein the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten. 81. The kit of paragraph 80, wherein the detectable label is a fluorophore. 82. The kit of paragraph 81, wherein the enzyme is peroxidase, alkaline phosphatase, or glucose oxidase. 83. The kit according to paragraph 82, wherein the peroxidase is horseradish peroxidase or soybean peroxidase. 84. The kit of paragraph 78, wherein the detectable secondary antibody is specific for the cross-linked antigen and has a dissociation constant of at most 100 nM, at most 30 nM, at most 10 nM, at most 3 nM, at most 1 nM, at most 0.3 nM, at most 0.1 nM, at most 0.03 nM, at most 0.01 nM, or at most 0.003 nM. 85. The kit according to paragraph 78, comprising: at least three immunoreagents according to any one of paragraphs 37 to 47; at least three detectable secondary antibodies that are high affinity and specific for the cross-linked antigen; and Instructions for using the kit Includes a kit. 86. The kit according to paragraph 78, at least five immunoreagents according to any one of paragraphs 37 to 47; at least five detectable secondary antibodies that are high affinity and specific for the cross-linked antigen; and Instructions for using the kit Includes a kit. 87. The kit according to paragraph 78, comprising: at least 10 immunoreagents according to any one of paragraphs 37 to 47; at least 10 detectable secondary antibodies that are high affinity and specific for the cross-linked antigen; and Instructions for using the kit Includes a kit.

[0180] It will be readily apparent to those skilled in the relevant art that other suitable modifications and adaptations of the methods and applications described herein can be made without departing from the scope of the invention or any embodiment thereof. Having thus described the invention in detail, the same will be more clearly understood by reference to the following examples. The examples are included herein for illustrative purposes only and are not intended to limit the invention. [Example]

[0181] Multiplex labeling of tissue sections with peptide-conjugated primary antibodies and fluorescent anti-peptide secondary antibodies material and method Modification buffer (100 mM phosphate, 150 mM NaCl, pH 7.4–7.6), conjugation buffer (100 mM phosphate, 150 mM NaCl, pH 6.0), aniline buffer (100 mM phosphate, 150 mM NaCl, 100 mM aniline, pH 6.0), PBS (10 mM phosphate, 150 mM NaCl, pH 7.0), Zeba desalting columns from ThermoPierce (Rockford, IL).

[0182] Amino-reactive fluorescent dyes Dy488-OSu, Dy550-OSu, and Dy650-OSu were purchased from Dyomics, Inc., Jena, Germany. antibody

[0183] Goat anti-mouse and goat anti-rabbit antibodies were purchased from ImmunoReagents, Inc. (Raleigh, NC). Rabbit monoclonal anti-estrogen receptor (ER), anti-progesterone receptor (PR), and anti-HER2 / neu receptor (HER2) antibodies were purchased from Epitomics, Inc. (Fremont, CA). Mouse anti-Ki67 was purchased from BD Biosciences, San Diego, CA. Rabbit monoclonal anti-peptide antibodies against PEP1, PEP2, PEP3, PEP4, and PEP5 were obtained from AvantGen, Inc. (San Diego, CA). Fluorescent staining and imaging

[0184] The following protocol was used for the immunofluorescence staining experiments described below. Slides were imaged on a Vala Sciences IC200Hist Imager (Vala Sciences, San Diego, CA). Images were processed using open-source ImageJ software and quantified using CyteSeer software (Vala Sciences, San Diego, CA).

[0185] Unless otherwise indicated, all breast cancer tissues were purchased from Key Biomedical, Ojai, CA. Manual Staining Protocol: 1. Slides were dewaxed as follows: Xylene 5 minutes Xylene 5 minutes 100% ethanol for 2 minutes 100% ethanol for 2 minutes 95% ethanol for 2 minutes 2. Wash twice with tap water for 2 minutes each time. 3. Wash once with distilled water for 2 minutes. 4. Antigen retrieval was achieved by steaming in 10 mM citric acid, pH 6.0, for 15 minutes. 5. The slides were allowed to cool in the pressure cooker for 10 minutes before releasing the pressure. 6. The pressure was released and the slide was transferred to hot distilled water for 2 minutes. 7. The slides were washed under running tap water for 5 minutes. 8. The slides were rinsed in wash buffer for 5 minutes. 9. A circle was drawn around the tissue using a hydrophobic pen. 10. Slides were blocked with normal serum (3% goat or rabbit serum, sometimes other serum depending on the stain) for 20 minutes. 11. After removing the previous solution, 150uL-200uL of cross-linking antigen-labeled primary antibody (which can be diluted using antibody diluent) was added directly onto the slide and incubated at room temperature for 1 hour. 12. The slides were washed three times with wash buffer for 5 minutes each. 13. The desired concentration of fluorescently labeled anti-crosslinking antigen antibody was added to the slide and incubated at room temperature for 1 hour. 14. The slides were washed three times with wash buffer for 5 minutes each. 15. The slides were rinsed with distilled water and excess water was removed with a paper towel. 16. One to three drops of Fluoroshield (Immunobiosciences, Inc., cat# AR-6501-01) containing DAPI were added to each slide, and after 3 to 5 minutes, a coverslip was applied in the dark at room temperature. Triple staining protocol modification: Alternative Step 11. A cocktail of peptide-conjugated primary antibodies at optimized concentrations was added to the slide and incubated at room temperature for 1 hour. In a specific example, a cocktail of anti-ER-PEP7 (10 μg / mL), anti-HER2-PEP5 (5 μg / mL), and anti-Ki67-PEP1 (5 μg / mL) was added to triple-positive breast cancer tissue and incubated at room temperature for 1 hour. Alternative Step 13: Prepare a cocktail of fluorophore-labeled anti-crosslinking antigen antibodies at the desired concentration, add to the slide, and incubate at room temperature for 1 hour. In a specific example, a cocktail of anti-PEP7-Dy550, anti-PEP5-Dy490, and anti-PEP1-Dy755 (all at 5 μg / mL) was added and incubated at room temperature for 1 hour. The results are presented in Figure 6. Pentafluorophenyl Boc-aminooxyacetate Synthesis

[0186] To a solution of Boc-aminooxyacetic acid (5.0 g, 26.2 mmol; EMD Chemicals) in DMF (30 mL) was added pentafluorophenol (4.57 g, 24.8 mmol; Oakwood Chemicals) and EDC (5.51 g, 2.88 mmol; Oakwood Chemicals). The reaction mixture was stirred at room temperature for 16 hours. The DMF was removed on a rotary evaporator, and the residue was partitioned between ethyl acetate and saturated sodium bicarbonate. The bicarbonate solution was back-extracted with ethyl acetate, and the combined organic extracts were washed with brine, dried over anhydrous magnesium sulfate, filtered, and concentrated to give 3.2 g of a white solid (single spot by TLC (100% ethyl acetate)). Incorporation of AOA conjugation reagents into peptides

[0187] The AOA linker was incorporated at the N-terminus of the peptides using standard solid-phase peptide synthesis with pentafluorophenyl Boc-aminooxyacetate, except that after FMOC deprotection of the final amino acid, the resin was washed repeatedly with acetonitrile and treated with a solution of pentafluorophenyl Boc-aminooxyacetate in DMF without base, i.e., diisopropylethylamine. All AOA peptides were purified by reverse-phase HPLC, and all peptides were shown to have the expected mass. Antibody-Peptide Conjugation Protocol

[0188] A solution of pentafluorophenyl Boc-aminooxyacetate (7.5 molar equivalents) in DMF was added to the deprotected N-terminus of each peptide during solid-phase peptide synthesis and incubated for 2 hours. No base was added to the linker solution. After incubation and washing, the peptide was cleaved from the resin in the presence of TFA (95%) / water (2.5%) / triisopropylsilane (2.5%), lyophilized, and purified by reverse-phase HPLC.

[0189] The following protocol was used to conjugate AOA-modified PEP5 to an anti-HER2 primary antibody. A similar protocol was used to conjugate other peptides to their respective antibodies. To a solution of anti-HER2 in modification buffer (80 uL; 80 μg at 1.0 mg / mL; 0.5 nmol), a solution of sulfo-4-formylbenzamide (0.45 uL of a 2.0 mg / mL solution in DMSO; 12.8 nmol; 24 molar equivalents; Cell_IDx, Inc., San Diego, CA) was added. The reaction was incubated for 2 hours at room temperature and desalted into conjugation buffer using a 0.5 mL Zeba column pre-equilibrated with conjugation buffer. Antibody recovery was assumed to be 90% (72 μg) based on the previous Zeba column recovery. AOA-modified PEP5 (0.43 μL of a 5 mg / mL solution in DMSO; 1.2 nmol: 5 molar equivalents; InnoPep, Inc., San Diego, CA) was added to HER2-4FB, followed by 7 μL of aniline buffer and incubation at room temperature for 2 hours. Free peptide and aniline were removed using a Spin-X UF 30K molecular weight cutoff concentrator (Corning, UK) by adding three separate additions of 10 mM phosphate, 150 mM NaCl, pH 7.0 buffer at least 5 times the sample volume in the concentrator to ensure complete removal and buffer exchange. The concentration of the antibody-peptide product was determined spectrophotometrically using an antibody extinction coefficient of 1.4.

[0190] Table 1 shows the peptide names and amino acid sequences of the peptides covalently conjugated to the primary antibodies in this example. The "AOA" group (aminooxyacetamide) was used to conjugate the peptides to the 4FB-modified primary antibodies. The dissociation constants (K) between the peptides and their corresponding antibodies were calculated. D ) are also shown in Table 1. These values ​​were obtained using a ForteBio instrument (www.fortebio.com). [Table 1] Modification of anti-peptide secondary antibodies with fluorophores

[0191] High-affinity anti-peptide secondary antibodies were modified with fluorophores as follows: To a solution of anti-peptide antibody in modification buffer (0.030 mg; 12 μL of a 2.5 mg / mL solution) was added Dy488-NHS ester (0.5 μL of a 5.0 mg / mL solution in anhydrous DMSO; 12 molar equivalents). The reaction mixture was incubated at room temperature for 2 hours and desalted twice using a 0.5 mL 40 K MWCO Zeba column pre-equilibrated with PBS.

[0192] Table 2 presents the cross-linking antigen-coupled primary antibodies and their target antigens, as well as the complementary fluorescently labeled high-affinity secondary antibody pairs prepared in this example, and the results of their staining on triple-positive breast cancer tissue. [Table 2] result

[0193] Schematic diagrams of staining a target antigen with an exemplary immunoreagent of the present disclosure are shown in Figures 1A-1C. In these figures, the target antigen is represented as two gray-outlined stars on the surface of a sample of interest (A), and the target antigen is labeled with a primary antibody specific for that target antigen (B). As shown in this figure, the primary antibody is coupled to two bridging antigens (represented by straight lines in the figure), although it should be understood that higher levels of coupling of bridging antigens to the primary antibody can be achieved, if desired. The sample is then stained (C) using a detectable secondary antibody with high specificity and affinity for the bridging antigen, where the detectable label is depicted as a dark-outlined star.

[0194] Figures 2A and 2B illustrate the weak staining of peptide-labeled primary antibodies using a commercially available low-affinity mouse monoclonal anti-peptide antibody. Specifically, MCF7 cells were subjected to immunocytochemical staining using either a Herceptin antibody (A) or a FLAG-tagged Herceptin antibody (B) prepared by modifying the Herceptin antibody with sulfo-S-4FB followed by the addition of HyNic-Peg2-Flag-tag (Solulink, Inc., San Diego, CA) in the presence of an aniline catalyst. The cells were then stained with either a standard fluorescent goat anti-human secondary antibody (A) or a fluorescent anti-FLAG secondary antibody (B) prepared as described above for fluorophore-labeling of anti-peptide antibodies. Cells stained with the commercially available low-affinity anti-FLAG antibody show significantly lower signals than conventional staining with a labeled cross-species secondary antibody.

[0195] The use of high-affinity anti-peptide antibodies to stain peptide-coupled primary antibodies is illustrated in Figures 3A and 3B. In this experiment, tissue sections from HER2-positive breast tissue (Key Biomedical, Inc., Ojai, CA) were labeled with either an unlabeled rabbit anti-HER2 / neu receptor primary antibody (A) or a peptide-coupled rabbit anti-HER2 / neu receptor primary antibody (B). The samples were then stained with either a Dy488-labeled goat anti-rabbit secondary antibody (A) or a Dy490-labeled rabbit anti-PEP5 antibody with high affinity for the PEP5 sequence (B). The results show comparable staining for the conventional secondary antibody approach (A) and secondary staining with a high-affinity antibody specific for the cross-linked antigen (B).

[0196] As shown in Figures 4A-4D, a correlation between the intensity of staining and the affinity of the antibody used to recognize the cross-linked antigen was demonstrated. Sections of Ki67-positive tissue were first labeled with anti-Ki67 primary antibodies coupled to various peptides. The sections were then stained with fluorophore-conjugated secondary antibodies specific to the various coupled peptides but with different affinities. The results showed that the peptide-antibody pair with the highest affinity (PEP5 / anti-PEP5; K D = 40 pM) (D) showed the brightest fluorescence intensity, while the peptide-antibody pairs with intermediate affinities (PEP3 / anti-PEP3 and PEP4 / anti-PEP4; K D = 90 pM) (B) and (C) show intermediate fluorescence and are the peptide-antibody pairs with the lowest affinity (PEP2 / anti-PEP2; K D = 160 pM) (A) had a slightly lower fluorescence intensity.

[0197] In another comparison of two different peptide / anti-peptide antibody pairs, Figures 5A and 5B show labeling of ER-positive tissue sections with anti-ER primary antibodies coupled to either PEP1 (A) or PEP5 (B). Samples were subsequently stained with high-affinity anti-PEP1 (A) or high-affinity anti-PEP5 (B) antibodies (each labeled with Dy650).

[0198] Simultaneous labeling of a single ER-positive, HER2-positive, and Ki-67-positive breast cancer tissue sample with a mixture of three peptide-antibody pairs has also been demonstrated. The sample was treated with a mixture of PEP7-coupled rabbit monoclonal anti-ER primary antibody, PEP5-coupled rabbit monoclonal anti-HER2 / neu receptor primary antibody, and PEP1-coupled rabbit monoclonal anti-Ki67 primary antibody. The labeled sections were then stained with a mixture of high-affinity Dy550-labeled anti-PEP7, Dy490-labeled anti-PEP5, and Dy755-labeled anti-PEP1. Figures 6A-6C show images of the stained tissue section showing emission from (A) the Dy550 channel, (B) the Dy490 channel, and (C) the Dy755 channel. Figure 6D shows an overlay of images from the three separate channels. The high sensitivity and specificity of simultaneous labeling of three important diagnostic tumor antigens demonstrates the powerful multiplexing capabilities of this immunoreagent.

[0199] The immunoreagents of the present disclosure can also be used in an amplified three-step staining procedure in which the antigen-coupled primary antibody is a cross-species reactive antibody. As shown diagrammatically in Figure 7, the target antigen (gray star) in a tissue sample of interest is labeled in step A with an unmodified first primary antibody from a first species. The bound antibody is then labeled in step B with an antigen-coupled second primary antibody from a second species that is specific for the constant region of the first antibody. In the diagram of Figure 7, the coupled bridging antigen is shown as two gray lines covalently associated with the second primary antibody. The antigen-coupled second primary antibody is then stained with a detectable secondary antibody with high affinity for the coupled antigen, as shown in step C.

[0200] Experimental confirmation of the amplified three-step staining procedure is provided in Figures 8A and 8B. In this experiment, triple positive (ER + , HER2 + , and PR +) Breast cancer tissue sections were separately labeled with either rabbit anti-HER2 antibody (A) or rabbit ER antibody (B). Next, the sections were labeled with PEP1-coupled anti-rabbit antibody (A). Finally, the sections were stained with Dy650-labeled high-affinity anti-PEP6 antibody. Bright staining demonstrates the validity of the technique. Immunoreagent Panels for Tissue Profiling

[0201] Simultaneous staining of triple-positive breast cancer tissue sections using a panel of anti-ER, anti-HER2, and anti-Ki-67 immunoreagent pairs is described above and shown in Figures 6A-6D. The following example provides further support for the use of defined panels of immunoreagents in multiplexed staining of diseased tissues. Thus, such a panel includes multiple immunoreagents, where the immunoreagents include a primary antibody and a bridging antigen, where the primary antibody and the bridging antigen are coupled and the bridging antigen is recognized with high affinity by a detectable secondary antibody.

[0202] For example, Figures 9A-9D demonstrate the use of this panel of immunoreagents for labeling melanoma tissue sections. Specifically, CD4, CD20, and CD68 targets on malignant melanoma tissue slides (ILS34116; purchased from ILSBio (www.ilsbio.com)) were simultaneously detected using a panel of peptide-coupled primary antibodies and fluorescent high-affinity anti-peptide secondary antibodies. The primary and secondary antibodies are listed in Table 3. The staining and imaging protocols are as described above. [Table 3]

[0203] Slides were incubated with a cocktail of primary antibodies conjugated to specific peptide antigens, with 5 μg / mL of each antibody. Figure 9A shows the fluorescence of anti-CD4 immunoreagent-stained T cells. Figure 9B shows the fluorescence of anti-CD20 immunoreagent-stained B cells. Figure 9C shows the fluorescence of anti-CD68 immunoreagent-stained macrophages. Figure 9D shows the combined fluorescence from all three immunoreagents. The insets in each panel represent zoomed-in areas of the slide.

[0204] Figures 10A-10D show simultaneous staining of triple-negative breast cancer tissue sections labeled with a panel of immunoreagents targeting cytokeratin 5 (CK5), cytokeratin 6 (CK6), and Ki-67. The immunoreagents were prepared from the primary antibodies and cross-linked peptide antigens listed in Table 4. The primary antibodies were detected using fluorescently labeled high-affinity anti-peptide secondary antibodies. The staining and imaging protocols were as described above. [Table 4]

[0205] Figure 10A shows the fluorescence from the anti-CK5 immunoreagent pair, Figure 10B shows the fluorescence from the anti-CK6 immunoreagent pair, Figure 10C shows the fluorescence from the anti-Ki67 immunoreagent pair, and Figure 10D shows an overlay of the fluorescence from all three labels.

[0206] Figures 11A-11E show quadruple labeling of cervical squamous cell carcinoma tissue sections. Specific fluorescence for CK5 is shown in Figure 11A, EGFR in Figure 11B, p40 in Figure 11C, and Ki-67 in Figure 11D, with an overlay of fluorescence from all four labels shown in Figure 11E. Immunoreagents were prepared from the primary antibodies and cross-linking antigens listed in Table 5. The staining and imaging protocols were as described above. [Table 5]

[0207] Figures 12A-12D show simultaneous labeling of IgA (A), C3c (B), COL4A5 (C), and IgG (D) in glomerulonephritis cores. Immunoreagents were prepared from the primary antibodies and cross-linking antigens listed in Table 6. Fluorescence from each immunoreagent pair is shown separately. Staining and imaging protocols were as described above. [Table 6] Multiplex staining of serial tissue sections with a panel of immunofluorescent reagents

[0208] In any normal or diseased tissue, there are many types of cells, including immune cells, that interact with each other within the tissue. Therefore, there is a need to identify, quantify, and determine the density and relative location of cells within a tissue of interest. Such characterization of cells within tissues is particularly important in cancer tissues, as it has recently been discovered that tumors produce signals on their surface that block immune cells from attacking and eliminating the tumor. Checkpoint inhibitors, such as pembrolizumab (Keytruda) and nivolumab (Opdivo), inhibit this blocking, thereby allowing T cells and other lymphocytes to eliminate the tumor. Therefore, such treatments can result in long-term cures in a certain percentage of patients with various tumors, including melanoma, non-small cell lung cancer (NSCLC), breast cancer, and bladder cancer. Tumeh et al. (2014) Nature 515:568-571 (DOI: 10.1038 / nature13954). However, there are currently no available diagnostic tests that can determine in advance whether checkpoint inhibitors will be effective. Therefore, identifying the many different cells present in the stroma and determining the correlation between tumor-infiltrating lymphocyte (TIL) infiltration and treatment outcome will have a significant impact in identifying factors that can lead to targeted therapy.

[0209] To further expand the number of immune cell types and other important cell types that can be identified in diseased tissues, it is demonstrated herein that the use of the described immunoreagents directed at markers on immune cells allows multiple cellular biomarkers to be simultaneously detected. Furthermore, it is demonstrated herein that using multiple panels of serial tissue samples and immunoreagents, the signals from each serial tissue can be overlaid to simultaneously detect, for example, eight and eleven target markers. In one example (described below), four triple-positive breast cancer markers (ER, PR, HER2, and Ki-67) were overlaid with four immune cell markers (CD3, CD4, CD8, and CD20), resulting in an image with a total of eight target markers. In a second example (also shown below), four triple-negative breast cancer markers (EGFR, CK5, vimentin, and Ki-67) were overlaid with the same panel of immune cell markers (CD3, CD4, CD8, and CD20), resulting in another eight-fold image.

[0210] In yet another example (also described below), three panels of immunoreagents were used to detect multiple markers on three consecutive tissues. In this example, three consecutive triple-negative breast cancer tissue specimens were labeled with immunoreagents targeting the four triple-negative cancer markers (CK5, EGFR, vimentin, and Ki-67) mentioned above, a set of four immune markers (CD4, CD8, CD68, and FoxP3) on a second consecutive tissue, and a second set of three immune markers (CD3, PD-1, and PD-L) on a third consecutive tissue, resulting in eleven-plex images. These images demonstrate the ability to visualize multiple immune markers in tumor tissue sections.

[0211] Specifically, Figures 13A-13E show simultaneous labeling of ER, PR, HER2, and Ki-67 on triple-positive breast cancer tissue (ILS32707; ILS Bio, Chestertown, MD). Immunoreagents were prepared from the primary antibodies and cross-linking antigens listed in Table 7. Fluorescence from each immunoreagent pair is shown separately. Staining and imaging protocols were as described above. [Table 7]

[0212] Figures 14A-14E show simultaneous labeling of CD3, CD4, CD8, and CD20 on consecutive tissues for the tissue data presented in Figure 13 for triple-positive breast cancer tissue (ILS32707; ILS Bio, Chestertown, MD). Immunoreagents were prepared from the primary antibodies and cross-linking antigens listed in Table 8. Fluorescence from each immunoreagent pair is shown separately. Staining and imaging protocols were as described above. [Table 8]

[0213] Figure 15 shows an overlay of sequential tissue staining results from quadruple staining with the triple-positive breast cancer panel (Figure 13) and the quadruple immunomarker panel (Figure 14). HER2 (red in original image), ER (blue in original image), PR (green in original image), Ki-67 (magenta in original image), CD3 (cyan in original image), CD4 (thallium in original image), and CD8 (orange in original image). Note that CD20 is not shown due to limitations in the imaging software.

[0214] Figures 16A-16E show simultaneous labeling of EGFR, CK5, vimentin, and Ki-67 on triple-negative breast cancer tissue (ILS36851; ILS Bio, Chestertown, MD). Immunoreagents were prepared from the primary antibodies and cross-linking antigens listed in Table 9. Fluorescence from each immunoreagent pair is shown separately. Staining and imaging protocols were as described above. [Table 9]

[0215] Figures 17A-17E show simultaneous labeling of CD3, CD4, CD8, and CD20 on consecutive tissues for the tissue data presented in Figure 14 for triple-negative breast cancer tissue (ILS36851; ILS Bio, Chestertown, MD). Immunoreagents were prepared from the primary antibodies and cross-linking antigens listed in Table 8. Fluorescence from each immunoreagent pair is shown separately. Staining and imaging protocols were as described above.

[0216] Figure 18 shows an overlay of sequential tissue staining results from quadruple staining with the triple-negative breast cancer panel (Figure 16) and the quadruple immunomarker panel (Figure 17). EGFR (red in original image), vimentin (blue in original image), CK5 (green in original image), Ki-67 (magenta in original image), CD3 (cyan in original image), CD4 (thallium in original image), and CD8 (orange in original image). Note that CD20 is not shown due to limitations in the imaging software.

[0217] Figure 19 shows simultaneous labeling of EGFR, CK5, vimentin, and Ki-67 on triple-negative breast cancer tissue (ILS36851; ILSBio, Chestertown, MD). Immunoreagents were prepared from the primary antibodies and cross-linking antigens listed in Table 9. Fluorescence from each immunoreagent pair is shown separately. Staining and imaging protocols are as described above. CK5 (yellow in original image), vimentin (silver in original image), EGFR (turquoise in original image), and Ki-67 (rainbow in original image).

[0218] Figure 20A shows simultaneous labeling of CD4, CD8, CD68, and FoxP3 on serial tissues for the tissue data presented in Figure 19 for triple-negative breast cancer tissue (ILS36851; ILSBio, Chestertown, MD). Immunoreagents were prepared from the primary antibodies and cross-linking antigens listed in Table 10. Fluorescence from each immunoreagent pair is shown separately. Staining and imaging protocols are as described above. CD4 (thallium in original), CD8 (orange in original), CD68 (magenta in original), and FoxP3 (red in original). [Table 10]

[0219] Figure 20B shows separate exemplary close-up cell images taken from the field of view of Figure 20A. The marker phenotype (as well as the putative cell type) for each cell image is shown. Quantification of the cell number for each cell type in the initial section is also shown. Phenotype counts were determined using CyteSeer software (Vala Sciences, San Diego, CA).

[0220] Figure 21 shows simultaneous labeling of CD3, PD-1, and PD-L1 on serial tissues for the tissue data presented in Figure 20 for triple-negative breast cancer tissue (ILS36851; ILSBio, Chestertown, MD). Immunoreagents were prepared from the primary antibodies and cross-linking antigens listed in Table 11. Fluorescence from each immunoreagent pair is shown separately. Staining and imaging protocols are as described above. CD3 (red in original image), PD-1 (green in original image), and PD-L1 (cyan in original image). Exemplary close-up cell images are also shown, along with their marker phenotypes and putative cell types. [Table 11]

[0221] Figure 22 shows an overlay of three consecutive tissue staining results using a quadruple triple-negative breast cancer panel (Figure 19), a quadruple immune marker panel (Figure 20), and a triple immune marker panel (Figure 21): CK5 (yellow in original image), EGFR (cyan in original image), vimentin (Thai in original image), Ki-67 (rainbow in original image), FoxP3 (red in original image), CD68 (magenta in original image), CD4 (thallium in original image), CD8 (orange in original image), CD3 (blue in original image), PD-1 (green in original image), and PD-L1 (cyan in original image). Selective removal of immunoreagents using soluble peptides

[0222] The ability to stain and remove both Western blot and immunohistochemical assays for identifying more than one marker on a sample surface typically requires harsh conditions. For example, in immunofluorescence assays for detecting more than three markers, such as those described in the Opal tyramide signal amplification (TSA)-based assay from PerkinElmer (www.perkinelmer.com), 15 minutes of microwave treatment of the tissue in a mildly acidic buffer is required to remove the primary / secondary antibody-HRP conjugate. A second reported method uses sodium azide / sodium peroxidase treatment to inactivate HRP. Ortiz de Montellano et al. (1988) Biochemistry 27:5470-5476 (DOI: 10.1021 / bi00415a013). Others have developed methods for removing primary antibodies from tissue that require relatively high temperatures and the use of denaturing detergents. Pirici et al. (2009) J. Histochem. Cytochem. 57:567-575 (DOI: 10.1369 / jhc.2009.953240).

[0223] As described and demonstrated herein, the immunoreagent can be selectively removed from a tissue sample by treating the sample with an excess of a soluble form of the cross-linking antigen under mild conditions. In particular, Figure 23 schematically illustrates an exemplary version of the procedure, in which two target antigens are labeled with two specific immunoreagents with different cross-linking antigens in step A. In step B, the sample is reacted with a first reactive secondary antibody that is high-affinity and specific for the cross-linking antigen of the first immunoreagent. In this example, the reactive secondary antibody carries horseradish peroxidase as a reactive group. In step C, the sample is treated with a fluorescently labeled tyramide reagent, thereby modifying sample proteins, including the first immunoreagent, that are close to the first target antigen.

[0224] The first reactive secondary antibody is then selectively dissociated from the sample by treatment with a soluble form of the bridging antigen, as shown in step D. Because the soluble bridging antigen is an effective competitor for the binding site of the secondary antibody and can be provided at a relatively high effective concentration, this step can be performed under mild conditions, thus minimizing damage to the sample. Steps E and F of the procedure are the same as steps B and C, except that the second reactive secondary antibody used in step E is specific for the bridging antigen of the second immunoreagent, and the fluorescently labeled tyramide reagent in step F carries a detectably different fluorophore than the tyramide reagent used in step C. After the reaction in step F, the sample can be imaged to detect the locations of the first and second detectable reagents and, accordingly, the first and second target antigens.

[0225] It is understood that the above process can be easily modified to detect as many target antigens as desired simply by treating the sample with additional immunoreagents of the present invention, which immunoreagents are specific for the additional antigens. The additional immunoreagents are sequentially labeled with appropriate reactive secondary antibodies, fluorescently labeled tyramide reagents, and soluble bridging antigens, as will be understood by those skilled in the art, by repeating steps B, C, and D of Figure 23 as many times as necessary.

[0226] In the method for selectively dissociating a reactive secondary antibody from a sample described and demonstrated above, the primary antibody and associated bridging antigen remain bound to the sample throughout the process, thus limiting further rounds of labeling to reactive secondary antibodies specific for different bridging antigens. In a variation of the above technique, the bridging antigen can be coupled to the primary antibody using a cleavable linker, thereby allowing selective dissociation of the reactive secondary antibody by cleavage of the linker, either alone or in combination with the addition of an excess of soluble bridging antigen. Cleavable linkers are known in the art, for example, cleavable by enzymes, nucleophilic / basic reagents, reducing agents, light irradiation, electrophilic / acidic reagents, organometallic and metallic reagents, and oxidizing reagents (see, e.g., Leriche et al. (2012) Bioorg. Med. Chem. 20:571-582 (doi:10.1016 / j.bmc.2011.07.048)). Due to the cleavage of the bridging antigen from the primary antibody during each labeling cycle, subsequently added primary antibodies can be labeled using the same bridging antigen. The use of a primary antibody labeled with the same bridging antigen in each cycle simplifies the process because the same reactive secondary antibody (e.g., HRP-labeled secondary antibody) can also be used in each cycle. As was true in the above method, differences in labeling of different target antigens are achieved by using different detectable reagents (e.g., tyramide reagents labeled with different fluorophores).

[0227] Figures 24A-C illustrate staining of HER2 and ER on a single triple-positive breast cancer tissue using the described method (further details are provided below). Figure 24A shows staining of HER2 using a PEP5-labeled primary antibody, an HRP-labeled anti-PEP5 secondary antibody, and tyramide-Dy490 fluorescent reagent. The anti-PEP5 secondary antibody was removed using an excess amount of PEP5 peptide. Figure 24B shows subsequent staining of ER on the same tissue section using a PEP7-labeled primary antibody, an HRP-labeled anti-PEP7 secondary antibody, and tyramide-Dy550 fluorescent reagent. Figure 24C shows an overlay of the two images (HER2, red in the original; ER, blue in the original).

[0228] Advantages of this method include: (1) all primary antibodies can be added simultaneously, unlike prior art methods, where stringent stripping conditions do not allow simultaneous addition of primary antibodies; (2) fluorescent labels are not exposed to heat or harsh chemicals and therefore do not damage their signal output; and (3) imaging needs to be performed only once, at the end of the staining step. experiment

[0229] The selective clearing method used to obtain the images in Figures 24A-24C was performed on triple-positive breast cancer tissue as follows: 1) 1-hour incubation with a cocktail of anti-HER2-PEP5 and anti-ER-PEP7 2) The tissue was washed three times with PBS. 3) Incubation with anti-PEP5 antibody-HRP conjugate for 30 minutes 4) Washed three times with washing buffer (PBS / 2% Tween 20) 5) Treated with tyramide-Dy-490 for 10 minutes 6) Washed three times with washing buffer 7) The tissue was incubated with a 150 μM solution of PEP5 peptide in PBS, followed by washing for 10 minutes. 8) Washed three times with washing buffer 9) Incubation with anti-PEP7 antibody-HRP conjugate for 30 minutes 10) Washed three times with washing buffer 11) Incubated with tyramide-Dy550 12) Fluoroshield containing DAPI (SigmaAldrich, St. Louis, MO) was added. 13) Covered with a cover glass 14) Images Cross-linked antigens with multiple antigenic determinants

[0230] It is recognized that incorporating consecutive affinity peptide repeats, i.e., tandem repeats, into proteins results in significantly higher signals in the binding of fluorescently labeled anti-peptide antibodies. For example, it has been shown that incorporating repetitive GCN4 peptide epitopes within a protein sequence can significantly increase the detectability of labeled proteins using fluorescent anti-GCN4 antibody derivatives. Tanenbaum et al. (2014) Cell 159:635-646.

[0231] As described herein, a ligatable 3X tandem repeat peptide has been synthesized by solid-phase techniques and used to demonstrate improved detectability with anti-peptide antibodies. The tandem repeat peptide, having the sequence AOA-(SGLQEQRNHLQ)3-NH2 (PEP6'; SEQ ID NO: 8), is a truncated version of the PEP6 sequence referenced above. The AOA-3X-PEP6' peptide was conjugated to rabbit anti-PR, and the staining intensity of this conjugate was compared to standard two-step staining with a fluorescently labeled secondary antibody. This protocol is represented diagrammatically in Figure 25, where the primary antibody shown is modified with two of the 3X tandem repeat peptides, thus providing multiple binding sites for detectable anti-peptide secondary antibodies.

[0232] Figure 26A illustrates conventional staining of triple-positive breast cancer tissue (ILS30380) using a rabbit anti-human PR primary antibody with a Dy650-labeled anti-rabbit secondary antibody. Figure 26B illustrates staining of the same tissue sample using a rabbit anti-human PR primary antibody coupled to a 3X tandem repeat PEP6' peptide with a Dy650-labeled anti-PEP6 secondary antibody. These results demonstrate that staining intensity of the tandem repeat conjugate was 15% stronger than that of conventional fluorescently labeled secondary antibodies. Cross-linked antigen containing a fluorescent label

[0233] The strength of signal generation from a fluorescently labeled antibody depends on the number of fluorophores at the binding site. However, the number of fluorophores on an antibody is limited to approximately 4–6 fluorophores because increasing the number of labels above that level can result in fluorescence quenching due to Förster resonance energy transfer (FRET). It is recognized that directly labeled monoclonal antibodies produce very weak signals due to the limited number of fluorophores on a single fluorescently labeled monoclonal antibody. However, it is also understood that fluorescently labeled secondary antibodies generate significantly stronger signals when multiple (i.e., 2–4) secondary antibodies can bind to each primary antibody bound to the target.

[0234] For example, as illustrated schematically in Figure 27, in an attempt to increase the signal of the immunoreagents of the present invention, a ligatable cross-linked antigen was synthesized that contained a fluorescent label conjugated to the distal end of the peptide cross-linked antigen. The fluorophore-labeled cross-linked antigen was conjugated to a primary antibody, and the labeled antibody was incubated with tissue containing the antigen targeted by the labeled primary antibody (Figure 27, Step A, the fluorescent label is designated "Z"). A fluorescently labeled anti-peptide secondary antibody was then added to the sample (Figure 27, Step B), after which the so-labeled sample was imaged.

[0235] Using triple-positive breast cancer tissue and an anti-HER2 antibody as the primary antibody, it was demonstrated that a fluorescently labeled primary antibody in conjunction with a fluorescently labeled secondary antibody provided a stronger signal than that obtained in assays where the primary antibody did not contain a fluorophore (Figures 28A-28D). experiment

[0236] The conjugable fluorescent peptide AOA-ETSGLQEQRNHLQGK(FITC)-NH2 (PEP6-FITC) was synthesized by solid-phase peptide synthesis at Innopep (www.innopep.com). The peptide was conjugated to HER2 using the above procedure with the following inputs: 5 mg / mL HER2, sulfo-S4FB (25 equivalents), and 10, 20, and 30 equivalents of peptide. After conjugation, the number of peptides was determined by the A490 / A280 ratio after subtraction of the A280 contribution of FITC. Five, six, and seven peptides were determined to be incorporated into HER2, respectively. Tissues were stained using the above procedure.

[0237] Figures 28A-28D show staining results in triple-positive breast cancer tissue (ILS25092) comparing rabbit anti-HER2 / anti-rabbit-FITC with HER2-PEP6-FITC modified at three increasing levels of degree of labeling (DOL): 5X, 6X, and 7X, demonstrating that FITC-anti-PEP6 after the highest level of PEP6-FITC modification of HER2 gives a stronger signal than the FITC-anti-rabbit secondary antibody. Quantitative results are presented in Table 12. [Table 12] Thermal removal of immunoreagents

[0238] As an alternative to selective removal of immunoreagents using soluble cross-linked antigen peptides or cleavable conjugation moieties (see above), samples stained with the immunoreagents of the present invention have also been dissociated from tissue samples using heat treatment. Specifically, after initial quadruple staining and imaging with a cocktail of immunoreagents, CD3, CD4, CD8, and CD20, the slides were incubated overnight in wash buffer, and the coverslips were removed without harming the tissue. The slides were then placed in citrate buffer, pH 6, and microwaved at 100% power (4 x 45 seconds) to bring the temperature to a boil. The slides were microwaved at 20% power for an additional 15 minutes, then allowed to cool to room temperature for 20 minutes. The slides were washed in distilled water for 2 minutes, followed by 2 minutes in wash buffer. The tissues were stained with the immunoreagents HER2, ER, PR, and Ki-67 and imaged.

[0239] Figures 29A and 29B show the results of a heat-clearing experiment, with the same tissue section shown in each image. The tissue section was triple-positive breast cancer tissue (ILS32707) stained with a cocktail of immunoreagents specific for CD8, CD4, CD20, and CD3 (Figure 29A). After microwave-clearing, the same tissue section was stained with a panel of immunoreagents for the breast cancer markers HER2, ER, PR, and Ki-67 (Figure 29B). Signals were normalized to the first round of antibody incubation for each slide.

[0240] All patents, patent publications, and other published references mentioned herein are hereby incorporated by reference in their entirety, as if each was individually and specifically incorporated by reference herein.

[0241] While specific examples have been provided, the above description is illustrative and not limiting. Any one or more of the features of the above embodiments may be combined in any manner with one or more features of any other embodiment of the present invention. Moreover, many variations of the present invention will be apparent to those skilled in the art upon review of the specification. Therefore, the scope of the present invention should be determined by reference to the appended claims, along with their full scope of equivalents.

Claims

1. 1. A method for an immunological assay, comprising: providing a multiplexed immunoreagent composition comprising a first immunoreagent, a second immunoreagent, and a third immunoreagent; providing a first sample comprising a first target antigen, a second target antigen, and a third target antigen; contacting the first sample with the multiplexed immunoreagent composition such that the first target antigen reacts with the first immunoreagent, the second target antigen reacts with the second immunoreagent, and the third target antigen reacts with the third immunoreagent, wherein the first immunoreagent comprises a first primary antibody coupled to a first bridging antigen, the first primary antibody being specific for the first target antigen, the second immunoreagent comprises a second primary antibody coupled to a second bridging antigen, the second primary antibody being specific for the second target antigen, and the third immunoreagent comprises a third primary antibody coupled to a third bridging antigen, the third primary antibody being specific for the third target antigen, and the first, second, and third bridging antigens are peptides; reacting the first immunoreagent with a first detectable secondary antibody, the second immunoreagent with a second detectable secondary antibody, and the third immunoreagent with a third detectable secondary antibody, wherein the first, second, and third detectable secondary antibodies are specific for the first, second, and third cross-linked antigens and each have a dissociation constant of at most 10 nM; and detecting the first detectable secondary antibody associated with the first immunoreagent, the second detectable secondary antibody associated with the second immunoreagent, and the third detectable secondary antibody associated with the third immunoreagent. Including, the first, the second and the third primary antibodies are different from each other, the first, the second and the third bridging antigens are different from each other, and the first, the second and the third detectable secondary antibodies are different from each other; method.

2. 10. The method of claim 1, wherein the first target antigen, the second target antigen, or the third target antigen is a cell marker.

3. The cell markers include 4-1BB, AFP, ALK1, amyloid A, amyloid P, androgen receptor, annexin A1, ASMA, BCA225, BCL-1, BCL-2, BCL-6, BerEP4, beta-catenin, beta-HCG, BG-8, BOB-1, CA19-9, CA125, calcitonin, caldesmon, calponin-1, calretinin, CAM5.2, CD1a, CD2, CD3, CD4, CD5, CD7, CD8, CD10, CD15, CD19, CD20, CD21, CD22, CD23, CD25, CD30, CD31, CD33, CD34, CD38, CD42b, CD43, and CD45. LCA, CD45RO, CD56, CD57, CD61, CD68, CD79a, CD99, CD117, CD138, CD163, CDX2, CEA, chromogranin A, CMV, c-kit, c-MET, c-MYC, type IV collagen, complement 3c (C3c), COX-2, CXCR5, CK1, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK20, CK90, CK1, CK1E, CK3, CK4, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK20, CK3, CK4, CK5, CK6, CK7, CK8, CK90, CK1E, CK1E, CK1E, CK1F, CK1F, CK1F, CK1F, CK1F, CK1F, CK1F, CK1F, CK1F, CK2F, CK3F, CK4, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK20 ...90, CK1F, CK1F, CK1F, CK1F, CK1F, CK2F, CK3F, CK4, CK5, CK6, CK7, CK8, CK14, CK18, CK17, CK19, CK AE1 / AE3, D2-40, desmin, DOG-1, E-cadherin, EGFR, EMA, ER, ERCC1, factor VIII-related antigen, activated factor XIII, fascin, FoxP1, FoxP3, galectin-3, GATA-3, GCDFP-15, GCET1, GFAP, glycophorin A, glypican 3, granzyme B, HBME-1, Helicobacter pylori, hemoglobin A, Hep Par1, HER2, HHV-8, HMB-45, HSV I / II, ICOS, IFN gamma, IgA, IgD, IgG, IgM, IL17, IL4, inhibin, iNOS, kappa Ig light chain, Ki67, LAG-3, lambda Ig light chain, lysozyme, mammaglobin A, MART-1 / Melan-A, mast cell tryptase, MLH1, MOC-31, MPO, MSA, MSH2, MSH6, M UC1, MUC2, MUM1, MyoD1, myogenin, myoglobin, napsin A, nestin, NSE, Oct-2, OX40, OX40L, p16, p21, p27, p40, p53, p63, p504s, PAX-5, PAX-8, PD-1, PD-L1, PHH3, PIN-4, PLAP, PMS2, Pneumocystisjiroveci (carinii), PR, PSA, PSAP, RCC, S-100, SMA, SMM, smoothelin, SOX10, SOX11, surfactant apoprotein A, synaptophysin, TAG72, TdT, thrombomodulin, thyroglobulin, TIA-1, TIM3, TRAcP, TTF-1, tyrosinase, uroplakin, VEGFR-2, villin, vimentin, and WT-1.

4. 10. The method of claim 1, wherein the first detectable secondary antibody, the second detectable secondary antibody, or the third detectable secondary antibody comprises a detectable label.

5. 5. The method of claim 4, wherein the detectable label is a fluorophore, an enzyme, an upconversion nanoparticle, a quantum dot, or a detectable hapten.

6. The method of claim 5 , wherein the detectable label is a fluorophore.

7. 7. The method of claim 6, wherein the enzyme is peroxidase, alkaline phosphatase, or glucose oxidase.

8. 8. The method of claim 7, wherein the peroxidase is horseradish peroxidase or soybean peroxidase.

9. 10. The method of claim 1, wherein the first target antigen, the second target antigen, or the third target antigen is in a tissue section.

10. 10. The method of claim 9, wherein the detecting step is a fluorescent detecting step.

11. 10. The method of claim 9, wherein the detecting step is an enzymatic detecting step.

12. 10. The method of claim 1, wherein the first target antigen, the second target antigen, or the third target antigen is in or on a cell.

13. 13. The method of claim 12, wherein the first target antigen, the second target antigen, or the third target antigen is on the surface of the cell.

14. The method of claim 12, wherein the detecting step is a fluorescent detection step.

15. 15. The method of claim 14, further comprising sorting cells that bind to the first detectable secondary antibody, the second detectable secondary antibody, or the third detectable secondary antibody.

16. the first sample further comprises a fourth target antigen and a fifth target antigen; The method comprises: reacting the fourth target antigen with a fourth immunoreagent and the fifth target antigen with a fifth immunoreagent, wherein the fourth immunoreagent comprises a fourth primary antibody coupled to a fourth bridging antigen, the fourth primary antibody being specific for the fourth target antigen, and the fifth immunoreagent comprises a fifth primary antibody coupled to a fifth bridging antigen, the fifth primary antibody being specific for the fifth target antigen; reacting the fourth immunoreagent with a fourth detectable secondary antibody and the fifth immunoreagent with a fifth detectable secondary antibody, wherein the fourth detectable secondary antibody is specific with high affinity for the fourth bridging antigen and the fifth detectable secondary antibody is specific with high affinity for the fifth bridging antigen; and detecting the fourth detectable secondary antibody associated with the fourth immunoreagent and the fifth detectable secondary antibody associated with the fifth immunoreagent. The method of claim 1 further comprising:

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