Patent Description:
However, conventional immunohistochemistry methods are limited in that they are only able to assess the spatial distribution of one, two or three (rarely more) epitopes in a tissue section. This constraint limits the application of immunohistochemistry in clinical diagnostics, in which field it is very desirable to analyze a much larger number of epitopes. Newer methods for epitope detection in a sample have been described and involve, for example, labeling a capture agent with DNA and subsequently detecting this DNA by primer extension, e.g., as in <CIT> and <CIT>. <CIT> discloses a hybrid IF/FISH method for analysing a sample using sequential staining and imaging steps.

The present method is automatable and allows for a highly multiplexed analysis. As such, the method is believed to meet some of the deficiencies of conventional immunohistochemistry methods.

The invention is defined according to the scope of the appended claims. The invention relates to a composition according to claim <NUM>. Disclosed herein, but not part of the description, is a method for analyzing a sample. In some embodiments, the method makes use of a plurality of capture agents that are each linked to a different oligonucleotide and a corresponding plurality of labeled nucleic acid probes, wherein each of the labeled nucleic acid probes specifically hybridizes with only one of the oligonucleotides. The sample is labeled with the capture agents en masse, and sub-sets of the capture agents are detected using iterative hybridization/label removal or inactivation cycles using corresponding subsets of the labeled nucleic acid probes. The capture agents are not stripped from the sample between hybridization/de-hybridization cycles. Depending on how the method is implemented, the method can be used to detect more than <NUM> epitopes in a sample without needing to strip the capture agents from the sample.

Unless defined otherwise herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described.

Numeric ranges are inclusive of the numbers defining the range. Unless otherwise indicated, nucleic acids are written left to right in <NUM>' to <NUM>' orientation; amino acid sequences are written left to right in amino to carboxy orientation, respectively.

The headings provided herein are not limitations of the various aspects or embodiments of the invention. Accordingly, the terms defined immediately below are more fully defined by reference to the specification as a whole.

<NPL>), and <NPL>) provide one of skill with the general meaning of many of the terms used herein. Still, certain terms are defined below for the sake of clarity and ease of reference.

As used herein, the term "biological feature of interest" refers to any part of a cell that can be indicated by binding to a capture agent. Exemplary biological features of interest include cell walls, nuclei, cytoplasm, membrane, keratin, muscle fibers, collagen, bone, proteins, nucleic acid (e.g., mRNA or genomic DNA, etc),, fat, etc. A biological feature of interest can also be indicated by immunohistological methods, e.g., a capture agent that is linked to an oligonucleotide. In these embodiments, the capture agent binds to a site, e.g., a protein epitope, in the sample. Exemplary epitopes include, but are not limited to, carcinoembryonic antigen (for identification of adenocarcinomas), cytokeratins (for identification of carcinomas but may also be expressed in some sarcomas) CD15 and CD30 (for Hodgkin's disease), alpha fetoprotein (for yolk sac tumors and hepatocellular carcinoma), CD117 (for gastrointestinal stromal tumors), CD10 (for renal cell carcinoma and acute lymphoblastic leukemia), prostate specific antigen (for prostate cancer), estrogens and progesterone (for tumour identification), CD20 (for identification of B-cell lymphomas), CD3 (for identification of T-cell lymphomas).

As used herein, the term "multiplexing" refers to using more than one label for the simultaneous or sequential detection and measurement of biologically active material.

As used herein, the terms "antibody" and "immunoglobulin" are used interchangeably herein and are well understood by those in the field. Those terms refer to a protein consisting of one or more polypeptides that specifically binds an antigen. One form of antibody constitutes the basic structural unit of an antibody. This form is a tetramer and consists of two identical pairs of antibody chains, each pair having one light and one heavy chain. In each pair, the light and heavy chain variable regions are together responsible for binding to an antigen, and the constant regions are responsible for the antibody effector functions.

The recognized immunoglobulin polypeptides include the kappa and lambda light chains and the alpha, gamma (IgG<NUM>, IgG<NUM>, IgG<NUM>, IgG<NUM>), delta, epsilon and mu heavy chains or equivalents in other species. Full-length immunoglobulin "light chains" (of about <NUM> kDa or about <NUM> amino acids) comprise a variable region of about <NUM> amino acids at the NH<NUM>-terminus and a kappa or lambda constant region at the COOH-terminus. Full-length immunoglobulin "heavy chains" (of about <NUM> kDa or about <NUM> amino acids), similarly comprise a variable region (of about <NUM> amino acids) and one of the aforementioned heavy chain constant regions, e.g., gamma (of about <NUM> amino acids).

The terms "antibodies" and "immunoglobulin" include antibodies or immunoglobulins of any isotype, fragments of antibodies which retain specific binding to antigen, including, but not limited to, Fab, Fv, scFv, and Fd fragments, chimeric antibodies, humanized antibodies, minibodies, single-chain antibodies, and fusion proteins comprising an antigen-binding portion of an antibody and a non-antibody protein. Also encompassed by the term are Fab', Fv, F(ab')<NUM>, and or other antibody fragments that retain specific binding to antigen, and monoclonal antibodies. Antibodies may exist in a variety of other forms including, for example, Fv, Fab, and (Fab')<NUM>, as well as bi-functional (i.e. bi-specific) hybrid antibodies (e.g., <NPL>)) and in single chains (e. , <NPL>) and <NPL>)). (See, generally, <NPL>), and <NPL>)).

The term "specific binding" refers to the ability of a binding reagent to preferentially bind to a particular analyte that is present in a homogeneous mixture of different analytes. In certain embodiments, a specific binding interaction will discriminate between desirable and undesirable analytes in a sample, in some embodiments more than about <NUM> to <NUM>-fold or more (e.g., more than about <NUM>- or <NUM>,<NUM>-fold).

In certain embodiments, the affinity between a binding reagent and analyte when they are specifically bound in a capture agent/analyte complex is characterized by a KD (dissociation constant) of less than <NUM>-<NUM> M, less than <NUM>-<NUM> M, less than <NUM>-<NUM> M, less than <NUM>-<NUM> M, less than <NUM>-<NUM> M, less than <NUM>-<NUM> M, or less than about <NUM>-<NUM> M or less.

A "plurality" contains at least <NUM> members. In certain cases, a plurality may have at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>,<NUM>, at least <NUM>,<NUM>, at least <NUM><NUM>, at least <NUM><NUM>, at least <NUM><NUM> or at least <NUM><NUM> or more members.

As used herein, the term "labeling" refers to attaching a capture agent to specific sites in a sample (e.g., sites containing an epitope for the antibody being used, for example) such that the presence and/or abundance of the sites can be determined by evaluating the presence and/or abundance of the capture agent. The term "labeling" refers to a method for producing a labeled sample in which any necessary steps are performed in any convenient order, as long as the required labeled sample is produced. For example, in some embodiments and as will be exemplified below, the capture agent may be linked to an oligonucleotide prior to binding of the antibody to the sample, in which case a sample can be labeled using relatively few steps.

As used herein, the term "planar sample" refers to a substantially planar, i.e., two dimensional, material (e.g. glass, metal, ceramics, organic polymer surface or gel) that contains cells or any combination of biomolecules derived from cells, such as proteins, nucleic acids, lipids, oligo/polysachharides, biomolecule complexes, cellular organelles, cellular debris or excretions (exosomes, microvesicles). A planar cellular sample can be made by, e.g., growing cells on a planar surface, depositing cells on a planar surface, e.g., by centrifugation, by cutting a three dimensional object that contains cells into sections and mounting the sections onto a planar surface, i.e., producing a tissue section, absorbing the cellular components onto the surface that is functionalized with affinity agents (e.g. antibodies, haptens, nucleic acid probes), introducing the biomolecules into a polymer gel or transferring them onto a polymer surface electrophoretically or by other means. The cells or biomolecules may be fixed using any number of reagents including formalin, methanol, paraformaldehyde, methanol:acetic acid, glutaraldehyde, bifunctional crosslinkers such as bis(succinimidyl)suberate, bis(succinimidyl)polyethyleneglycole etc. This definition is intended to cover cellular samples (e.g., tissue sections, etc.), electrophoresis gels and blots thereof, Western blots, dot-blots, ELISAs, antibody microarrays, nucleic acid microarrays, etc..

As used herein, the term "tissue section" refers to a piece of tissue that has been obtained from a subject, fixed, sectioned, and mounted on a planar surface, e.g., a microscope slide.

As used herein, the term "formalin-fixed paraffin embedded (FFPE) tissue section" refers to a piece of tissue, e.g., a biopsy that has been obtained from a subject, fixed in formaldehyde (e.g., <NUM>%-<NUM>% formaldehyde in phosphate buffered saline) or Bouin solution, embedded in wax, cut into thin sections, and then mounted on a microscope slide.

As used herein, the term "non-planar sample" refers to a sample that is not substantially flat, e.g., a whole or part organ mount (e.g., of a lymph node, brain, liver, etc.), that has been made transparent by means of a refractive index matching technique such as Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging-compatible Tissue-hydrogel (CLARITY). See, e.g., <NPL>. Clearing agents such as Benzyl-Alcohol/Benzyl Benzoate (BABB) or Benzyl-ether may be used to render a specimen transparent.

As used herein, the term "spatially-addressable measurements" refers to a set of values that are each associated with a specific position on a surface. Spatially-addressable measurements can be mapped to a position in a sample and can be used to reconstruct an image, e.g., a two- or three-dimensional image of the sample.

A "diagnostic marker" is a specific biochemical in the body which has a particular molecular feature that makes it useful for detecting a disease, measuring the progress of disease or the effects of treatment, or for measuring a process of interest.

A "pathoindicative" cell is a cell which, when present in a tissue, indicates that the animal in which the tissue is located (or from which the tissue was obtained) is afflicted with a disease or disorder. By way of example, the presence of one or more breast cells in a lung tissue of an animal is an indication that the animal is afflicted with metastatic breast cancer.

The term "complementary site" is used to refer to an epitope for an antibody or aptamer. Specifically, if the capture agent is an antibody or aptamer, then the complementary site for the capture agent is the epitope in the sample to which the antibody binds.

The term "epitope" as used herein is defined as a small chemical group on the antigen molecule that is bound to by an antibody or aptamer. An antigen can have one or more epitopes. In many cases, an epitope is roughly five amino acids or sugars in size. One skilled in the art understands that generally the overall three-dimensional structure or the specific linear sequence of the molecule can be the main criterion of antigenic specificity.

A "subject" of diagnosis or treatment is a plant or animal, including a human. Non-human animals subject to diagnosis or treatment include, for example, livestock and pets.

As used herein, the term "incubating" refers to maintaining a sample and capture agent under conditions (which conditions include a period of time, a temperature, an appropriate binding buffer and a wash) that are suitable for specific binding of the capture agent to molecules (e.g., epitopes or complementary nucleic acid) in the sample.

As used herein, the term "capture agent" refers to an agent that can specifically bind to complementary sites in a sample. Exemplary capture agents include antibodies and aptamers. If antibodies or aptamers are used, in many cases they may bind to protein epitopes.

As used herein, the term "capture agent that is linked to a oligonucleotide" refers to a capture agent, e.g., an antibody or aptamer, that is non-covalently (e.g., via a streptavidin/biotin interaction) or covalently (e.g., via a click reaction or the like) linked to a single-stranded oligonucleotide in a way that the capture agent can still bind to its binding site. The nucleic acid and the capture agent may be linked via a number of different methods, including those that use maleimide or halogen-containing group, which are cysteine-reactive. The capture agent and the oligonucleotide may be linked proximal to or at the <NUM>' end of the oligonucleotide, proximal to or at the <NUM>' end of the oligonucleotide, or anywhere in-between.

As used herein, the term "removing", in the context of removing the labels and/or the probes that are associated with, i.e., hybridized to, a sample, refers to any method for physically separating the labels and/or probes from a sample. The labels and/or the probes can be removed from the sample by denaturation or by cleaving a linkage in the probe or a linker that attaches the label to the probe, for example, where the removal method used leaves the unhybridized oligonucleotides that are attached to the other antibodies intact and free to hybridize to the labeled probes used in the next cycle.

As used herein, the term "inactivating", in the context of inactivating a label, refers to chemically modifying a label so that it no longer produces a detectable signal. Photobleaching is one way to inactivate a label, although other ways are known.

The terms "nucleic acid" and "polynucleotide" are used interchangeably herein to describe a polymer of any length, e.g., greater than about <NUM> bases, greater than about <NUM> bases, greater than about <NUM> bases, greater than about <NUM> bases, greater than <NUM> bases, up to about <NUM>,<NUM> or more bases composed of nucleotides, e.g., deoxyribonucleotides, ribonucleotides or a combination thereof, and may be produced enzymatically or synthetically (e.g., PNA as described in <CIT> and the references cited therein) and which can hybridize with naturally occurring nucleic acids in a sequence specific manner analogous to that of two naturally occurring nucleic acids, e.g., can participate in Watson-Crick base pairing interactions. Naturally-occurring nucleotides include guanine, cytosine, adenine, thymine, uracil (G, C, A, T and U respectively). DNA and RNA have a deoxyribose and ribose sugar backbone, respectively, whereas PNA's backbone is composed of repeating N-(<NUM>-aminoethyl)-glycine units linked by peptide bonds. In PNA various purine and pyrimidine bases are linked to the backbone by methylene carbonyl bonds. A locked nucleic acid (LNA), often referred to as an inaccessible RNA, is a modified RNA nucleotide. The ribose moiety of an LNA nucleotide is modified with an extra bridge connecting the <NUM>' oxygen and <NUM>' carbon. The bridge "locks" the ribose in the <NUM>'-endo (North) conformation, which is often found in the A-form duplexes. LNA nucleotides can be mixed with DNA or RNA residues in the oligonucleotide whenever desired. The term "unstructured nucleic acid", or "UNA", is a nucleic acid containing non-natural nucleotides that bind to each other with reduced stability. For example, an unstructured nucleic acid may contain a G' residue and a C' residue, where these residues correspond to non-naturally occurring forms, i.e., analogs, of G and C that base pair with each other with reduced stability, but retain an ability to base pair with naturally occurring C and G residues, respectively. Unstructured nucleic acid is described in <CIT>.

As used herein, the term "oligonucleotide" refers to a multimer of at least <NUM>, e.g., at least <NUM> or at least <NUM> nucleotides. In some embodiments, an oligonucleotide may be in the range of <NUM>-<NUM> nucleotides in length, or more. Any oligonucleotide used herein may be composed of G, A, T and C, or bases that are capable of base pairing reliably with a complementary nucleotide. <NUM>-deaza-adenine, <NUM>-deaza-guanine, adenine, guanine, cytosine, thymine, uracil, <NUM>-deaza-<NUM>-thio-guanosine, <NUM>-thio-<NUM>-deaza-guanosine, <NUM>-thio- adenine, <NUM>-thio-<NUM>-deaza-adenine, isoguanine, <NUM>-deaza-guanine, <NUM>,<NUM>-dihydrouridine, <NUM>,<NUM>- dihydrothymine, xanthine, <NUM>-deaza-xanthine, hypoxanthine, <NUM>-deaza-xanthine, <NUM>,<NUM> diamino-<NUM>- deaza purine, <NUM>-methyl-cytosine, <NUM>-propynyl-uridine, <NUM>-propynyl-cytidine, <NUM>-thio-thymine or <NUM>-thio-uridine are examples of such bases, although many others are known. As noted above, an oligonucleotide may be an LNA, a PNA, a UNA, or an morpholino oligomer, for example. The oligonucleotides used herein may contain natural or non-natural nucleotides or linkages.

As used herein, the term "reading" in the context of reading a fluorescent signal, refers to obtaining an image by scanning or by microscopy, where the image shows the pattern of fluorescence as well as the intensity of fluorescence in a field of view.

As used herein, the term "signal generated by", in the context of reading a fluorescent signal generated by addition of the fluorescent nucleotide, refers to a signal that is emitted directly from the fluorescent nucleotide, a signal that is emitted indirectly via energy transfer to another fluorescent nucleotide (i.e., by FRET). For example, in some embodiments, the method may be implemented using a molecular inversion probe with a donor fluor at one end and an acceptor fluor at the other for fluorescence energy transfer. When the probe is free in solution the two fluors are far apart. When they are hybridized to the oligo on the antibody, the two fluors are immediately adjacent to each other.

Other definitions of terms may appear throughout the specification.

A method for analyzing a sample, e.g., a planar sample, is disclosed, but not part of the invention. The method comprises obtaining: i. a plurality of capture agents that are each linked to a different oligonucleotide and ii. a corresponding plurality of labeled nucleic acid probes (where the term "corresponding" is intended to mean that the number of labeled nucleic acid probes is the same as the number of capture agents used), where each of the labeled nucleic acid probes is complementary to and specifically hybridizes with only one of the oligonucleotides. For example, if there are <NUM> capture agents then they are each linked to different oligonucleotides and there are <NUM> labeled nucleic acid probes, where each labeled nucleic acid probe is complementary to and specifically hybridizes with only one of the oligonucleotides. The number of capture agents and labeled nucleic acid probes used in the method may vary. In some embodiments, the method may be performed using: i. at least <NUM> or at least <NUM> and up to <NUM> or <NUM> or more capture agents, each linked to a different oligonucleotide, and ii. a corresponding number of labeled nucleic acid probes.

The method comprises labeling the sample with the plurality of capture agents. This step involves contacting the sample (e.g., an FFPE section mounted on a planar surface such as a microscope slide) with all of the capture agents, en masse under conditions by which the capture agents bind to complementary sites in (e.g., protein epitopes) in the sample. Methods for binding antibodies and aptamers to sites in the sample are well known. In some embodiments, the capture agents may be cross-linked to the sample, thereby preventing the capture agent from disassociating during subsequent steps. This crosslinking step may be done using any amine-to-amine crosslinker (e.g. formaldehyde, disuccinimiyllutarate or another reagent of similar action) although a variety of other chemistries can be used to cross-link the capture agent to the sample if desired.

After the sample has been bound to the capture agents, the method involves specifically hybridizing a first sub-set of the labeled nucleic acid probes with the sample, wherein the probes in the first sub-set are distinguishably labeled, to produce labeled probe/oligonucleotide duplexes. By "sub-set" is meant at least two, e.g., two, three or four and the term "distinguishably labeled" means that the labels can be separately detected, even if they are at the same location. As such, in some embodiments, the method may involve specifically hybridizing two, three or four of the labeled nucleic acid probes with the sample, thereby producing labeled probe/oligonucleotide duplexes that are linked to antibodies that are bound to sites in the sample. The label may be a pro-fluorophore, a secondary activatible fluorophore, a fluorescent protein, a visible stain, a polychromatic barcode, a mass tag (e.g., an isotope or a polymer of a defined size), a structural tags for label-free detection, a radio sensitive tag (activated by THz camera) a radioactive tag or an absorbance tag that only absorbs light at a specific frequency for example. In some embodiments, an oligonucleotide may deliver an enzyme that delivers a fluorophore or there may be an enzymatic amplification of signal. In some embodiments, the signal detected may be generated by fluorescence resonance energy transfer (FRET) and in other embodiments the detection may be done by raman spectroscopy, infrared detection, or magnetic/electrical detection. In some embodiments, the detecting step may involve a secondary nucleic acid amplification step, including, but not limited, to hybridization chain reaction, branched DNA (bDNA) amplification, etc..

Suitable distinguishable fluorescent label pairs useful in the subject methods include Cy-<NUM> and Cy-<NUM> (Amersham Inc. , Piscataway, NJ), Quasar <NUM> and Quasar <NUM> (Biosearch Technology, Novato CA), Alexafluor555 and Alexafluor647 (Molecular Probes, Eugene, OR), BODIPY V-<NUM> and BODIPY V1005 (Molecular Probes, Eugene, OR), POPO-<NUM> and TOTO-<NUM> (Molecular Probes, Eugene, OR), and POPRO3 and TOPRO3 (Molecular Probes, Eugene, OR). Further suitable distinguishable detectable labels may be found in <NPL>), <NPL>) and <NPL>) and others. In some embodiments three or four distinguishable dyes may be used. Specific fluorescent dyes of interest include: xanthene dyes, e.g., fluorescein and rhodamine dyes, such as fluorescein isothiocyanate (FITC), <NUM>-carboxyfluorescein (commonly known by the abbreviations FAM and F), <NUM>-carboxy-<NUM>',<NUM>',<NUM>',<NUM>,<NUM>-hexachlorofluorescein (HEX), <NUM>-carboxy-<NUM>', <NUM>'-dichloro-<NUM>', <NUM>'-dimethoxyfluorescein (JOE or J), N,N,N',N'-tetramethyl-<NUM>-carboxyrhodamine (TAMRA or T), <NUM>-carboxy-X-rhodamine (ROX or R), <NUM>-carboxyrhodamine-<NUM> (R6G<NUM> or G<NUM>), <NUM>-carboxyrhodamine-<NUM> (R6G<NUM> or G<NUM>), and rhodamine <NUM>; cyanine dyes, e.g., Cy3, Cy5 and Cy7 dyes; coumarins, e.g., umbelliferone; benzimide dyes, e.g. Hoechst <NUM>; phenanthridine dyes, e.g., Texas Red; ethidium dyes; acridine dyes; carbazole dyes; phenoxazine dyes; porphyrin dyes; polymethine dyes, e.g., BODIPY dyes and quinoline dyes. Specific fluorophores of interest that are commonly used in subject applications include: Pyrene, Coumarin, Diethylaminocoumarin, FAM, Fluorescein Chlorotriazinyl, Fluorescein, R110, Eosin, JOE, R6G, Tetramethylrhodamine, TAMRA, Lissamine, Napthofluorescein, Texas Red, Cy3, and Cy5, etc. As noted above, within each sub-set of probes, the fluorophores may be chosen so that they are distinguishable, i.e., independently detectable, from one another, meaning that the labels can be independently detected and measured, even when the labels are mixed. In other words, the amounts of label present (e.g., the amount of fluorescence) for each of the labels are separately determinable, even when the labels are co-located (e.g., in the same tube or in the same area of the section).

After the sample has been washed to remove labeled nucleic acid probes that have not hybridized, the method comprises reading the sample to obtain an image showing the binding pattern for each of the sub-set of probes hybridized in the prior step. This step may be done using any convenient reading method and, in some embodiments, e.g., hybridization of the different probes can be separately read using a fluorescence microscope equipped with an appropriate filter for each fluorophore, or by using dual or triple band-pass filter sets to observe multiple fluorophores (see, e.g., <CIT>).

After reading the sample, the method comprises inactivating or removing the labels that are associated with (i.e., hybridized to) the sample, leaving the plurality of capture agents and their associated oligonucleotides (i.e., the unhybridized oligonucleotides) still bound to the sample. The labels that are associated with the sample are removed or inactivated by denaturation (in which case the label and the probe in its entirety may be released and can be washed away). In this removal method, the unhybridized oligonucleotides that are attached to the other antibodies are intact and free to hybridize to the set of labeled probes used in the next cycle.

The removing step is done by inactivating or removing the hybridized probes from the sample by denaturation, leaving the other capture agents (i.e., the capture agents that are not hybridized to a probe) and their associated oligonucleotides still bound to the sample.

After reading the sample, the method comprises m (e) removing the probes hybridized in step (c) from the sample by denaturation (i.e., by un-annealing the labeled probes from the oligonucleotides and washing them away), leaving the capture agents of (b) and their associated oligonucleotides still bound to the sample. This step is done using a suitable chemical denaturant, e.g., formamide, DMSO, urea, or a chaotropic agent (e.g., guanidinium chloride or the like), optionally using a toehold release strategy (see, e.g., <NPL>), or using heat, base, a topoisomerase or a single-strand binding agent (e.g., SSBP) or through hybridization of an oligonucleotide with a greater affinity (e.g. PNA). In some cases, the probes may by removed by incubating the sample in <NUM>% to <NUM>% formamide (e.g., <NUM>% to <NUM>% formamide) for a period of at least <NUM> minute (e.g., <NUM> to <NUM> mins), followed by a wash. This denaturation step may be repeated, if necessary, so that all of the hybridized probes have been removed. As would be apparent, this step is not implemented enzymatically, i.e., does not use a nuclease such as a DNAse or a restriction enzyme, and does not result in cleavage of any covalent bonds, e.g., in any of the probes or oligonucleotides or removal of any of the capture agents from the sample. In this step, the strands of the probe/oligonucleotide duplexes are separated from one another (i.e., denatured), and the separated probes, which are now free in solution, are washed away, leaving the capture agents and their associated oligonucleotides intact and in place.

After removal of the probes, the sample may be hybridized with a different sub-set of the labeled probes (e.g., a second sub-set of two to four of the labeled probes, where the probes are distinguishably labeled), and the sample may be re-read to produce an image showing the binding pattern for each of the most recently hybridized sub-set of probes. After the sample has been read, the probes may be removed from the sample by denaturation, and the hybridization and reading steps may be repeated with a different sub-set of distinguishably labeled probes. In other words, the method may comprise repeating the hybridization, label removal or inactivation and reading steps multiple times with a different sub-set of two to four of the labeled nucleic acid probes, where the probes in each sub-set are distinguishably labeled and each repeat is followed by removal of the probes by denaturation (except for the final repeat) to produce a plurality of images of the sample, where each image corresponds to a sub-set of labeled nucleic acid probes. The hybridization/reading/label removal or inactivation steps can be repeated until all of the probes have been analyzed.

As would be apparent, the DNA sequences used may be selected in order to minimize background staining, either from non-specific adsorption or through binding to endogenous genomic sequences (RNA or DNA). Likewise, the hybridization and washing buffers may be designed to minimize background staining either from non-specific adsorption or through binding to endogenous genomic sequences (RNA or DNA) or through binding to other reporter sequences.

In some embodiments, after labeling the sample with the capture agents, the method comprises: specifically hybridizing a first sub-set of the labeled nucleic acid probes with the sample, wherein the probes in the first sub-set are distinguishably labeled, to produce labeled probe/oligonucleotide duplexes; reading the sample to obtain an image showing the binding pattern for each of the probes hybridized in the prior step; removing the probes hybridized in the prior step from the sample, by chemical denaturation as described elsewhere herein, leaving the plurality of capture agents and their associated oligonucleotides still bound to the sample; specifically hybridizing a second sub-set of the labeled nucleic acid probes with the sample, wherein the probes in the second sub-set are distinguishably labeled, to produce labeled probe/oligonucleotide duplexes; reading the sample to obtain an image showing the binding pattern for each of the probes in the second sub-set of probes; removing the probes in the probes in the second sub-set that are hybridized to the sample, by chemical denaturation, leaving the plurality of capture agents and their associated oligonucleotides still bound to the sample. The hybridization/reading/label removal or inactivation cycle can then be repeated for a third, fourth and fifth or more sub-set of probes until all of the probes have been hybridized and read, with the exception that in the final cycle the probes do not need to be removed from the sample. In some cases, the hybridization/reading steps may be repeated <NUM> to <NUM> or more times, with a chemical denaturation step after each reading except for the last repeat.

In some embodiments, the labeled nucleic acid probes are <NUM> to <NUM> nucleotides in length, e.g., <NUM> to <NUM> nucleotides or <NUM> to <NUM> nucleotides in length although, in some embodiments, the probe may be as short as <NUM> nucleotides in length to as long as a <NUM> nucleotides in length (e.g., <NUM> nucleotides in length to <NUM> nucleotides in length). In some embodiments, a probe may have a calculated Tm in the range of <NUM> to <NUM> (e.g., <NUM>-<NUM> or <NUM>-<NUM>) such that the duplexes of the hybridization step have a Tm in the same range. In these embodiments, the Tm may be calculated using the IDT oligoanalyzer program (available at IDT's website and described in <NPL>) using default settings of <NUM> Na+, <NUM> oligonucleotide. The sequence of the probes can be any sequence although, in some embodiments, each labeled nucleic acid probe may have a sequence selected from SEQ ID NOS: <NUM>-<NUM>, or a complement thereof. In some embodiments, the probes are Tm-matched, where the term "Tm-matched" refers to sequences that have melting temperatures that are within a defined range, e.g., less than <NUM>, less than <NUM> or less than <NUM> of a defined temperature. As would be apparent, the probes may be labeled at the <NUM>' end, the <NUM>' end or anywhere in between. In some embodiments, the probes may be specifically cleavable, e.g., may contain a cleavable linker (e.g., a photo- or chemically-cleavable linker). Likewise, the oligonucleotides may be at least <NUM> nucleotides in length, e.g., at least <NUM>, at least <NUM> or at least <NUM> such as <NUM>-<NUM> nucleotides in length.

In some embodiments, the sequences of the oligonucleotides to which the capture agents are linked are the same length and are perfectly complementary to the labeled probes. In these embodiments, the oligonucleotides may be linked to the capture agents by a linker that spaces the oligonucleotide from the capture agents. In other embodiments, the sequences of the oligonucleotides to which the capture agents are linked are: i. longer than the sequences of the labeled nucleic acid probes and otherwise identical to one other except for a sub-sequence that is complementary to a single labeled nucleic acid probe. In these embodiments, the extra sequence acts as a linker to space the oligonucleotides from the capture agents. In certain embodiment, the oligonucleotides that are linked to the capture agents are from <NUM> to 40nt in length. Oligonucleotides may be linked to capture agents using any convenient method (see, e.g., <NPL> and <NPL>). A variety of labeling methods are available. For example, the unique oligonucleotides may be linked to the capture agents directly using any suitable chemical moiety on the capture agent (e.g., a cysteine residue or via an engineered site). In other embodiments, a common oligonucleotide may be conjugated directly to all of the capture agent using any suitable chemistry, and the unique oligonucleotides may be linked to the common oligonucleotides enzymatically, e.g., by ligation. In other embodiments, the unique oligonucleotides may be linked to the capture agents directly or indirectly via a non-covalent interaction, e.g., via a biotin/streptavidin or an equivalent thereof, via an aptamer or secondary antibody, or via a protein-protein interaction such as a leucine-zipper tag interaction or the like. In alternative embodiments, the oligonucleotides and probes of the present method can be substituted for other entities that can bind to one another in a specific manner, e.g., leucine zipper pairs or antigen/antibody pairs.

Each reading step produces an image of the sample showing the pattern of binding of a sub-set of probes. In some embodiments, the method may further comprise analyzing, comparing or overlaying, at least two of the images. In some embodiments, the method may further comprise overlaying all of the images to produce an image showing the pattern of binding of all of the capture agents to the sample. The image analysis module used may transform the signals from each fluorophore to produce a plurality of false color images. The image analysis module may overlay the plurality of false color images (e.g., superimpose the false colors at each pixel) to obtain a multiplexed false color image. Multiple images (e.g., unweighted or weighted) may be transformed into a single false color, e.g., so as to represent a biological feature of interest characterized by the binding of specific capture agent. False colors may be assigned to specific capture agents or combinations of capture agents, based on manual input from the user. In certain aspects, the image may comprise false colors relating only to the intensities of labels associated with a feature of interest, such as in the nuclear compartment. The image analysis module may further be configured to adjust (e.g., normalize) the intensity and/or contrast of signal intensities or false colors, to perform a convolution operation (such as blurring or sharpening of the intensities or false colors), or perform any other suitable operations to enhance the image. The image analysis module may perform any of the above operations to align pixels obtained from successive images and/or to blur or smooth intensities or false colors across pixels obtained from successive images.

In some embodiments, images of the sample may be taken at different focal planes, in the z direction. These optical sections can be used to reconstruct a three dimensional image of the sample. Optical sections may be taken using confocal microscopy, although other methods are known. The image analysis method may be implemented on a computer. A general-purpose computer can be configured to a functional arrangement for the methods and programs disclosed herein. The hardware architecture of such a computer is well known by a person skilled in the art, and can comprise hardware components including one or more processors (CPU), a random-access memory (RAM), a read-only memory (ROM), an internal or external data storage medium (e.g., hard disk drive). A computer system can also comprise one or more graphic boards for processing and outputting graphical information to display means. The above components can be suitably interconnected via a bus inside the computer. The computer can further comprise suitable interfaces for communicating with general-purpose external components such as a monitor, keyboard, mouse, network, etc. The computer can be capable of parallel processing or can be part of a network configured for parallel or distributive computing to increase the processing power for the present methods and programs. The program code read out from the storage medium can be written into a memory provided in an expanded board inserted in the computer, or an expanded unit connected to the computer, and a CPU or the like provided in the expanded board or expanded unit can actually perform a part or all of the operations according to the instructions of the program code, so as to accomplish the functions described below. The method can be performed using a cloud computing system. In these embodiments, the data files and the programming can be exported to a cloud computer, which runs the program, and returns an output to the user.

In addition to the labeling methods described above, the sample may be stained using a cytological stain, either before or after performing the method described above. In these embodiments, the stain may be, for example, phalloidin, gadodiamide, acridine orange, bismarck brown, barmine, Coomassie blue, bresyl violet, brystal violet, DAPI, hematoxylin, eosin, ethidium bromide, acid fuchsine, haematoxylin, hoechst stains, iodine, malachite green, methyl green, methylene blue, neutral red, Nile blue, Nile red, osmium tetroxide (formal name: osmium tetraoxide), rhodamine, safranin, phosphotungstic acid, osmium tetroxide, ruthenium tetroxide, ammonium molybdate, cadmium iodide, carbohydrazide, ferric chloride, hexamine, indium trichloride, lanthanum nitrate, lead acetate, lead citrate, lead(II) nitrate, periodic acid, phosphomolybdic acid, potassium ferricyanide, potassium ferrocyanide, ruthenium red, silver nitrate, silver proteinate, sodium chloroaurate, thallium nitrate, thiosemicarbazide, uranyl acetate, uranyl nitrate, vanadyl sulfate, or any derivative thereof. The stain may be specific for any feature of interest, such as a protein or class of proteins, phospholipids, DNA (e.g., dsDNA, ssDNA), RNA, an organelle (e.g., cell membrane, mitochondria, endoplasmic recticulum, golgi body, nuclear envelope, and so forth), or a compartment of the cell (e.g., cytosol, nuclear fraction, and so forth). The stain may enhance contrast or imaging of intracellular or extracellular structures. In some embodiments, the sample may be stained with haematoxylin and eosin (H&E).

The methods and compositions described herein find general use in a wide variety of applications for analysis of any sample (e.g., in the analysis of tissue sections, sheets of cells, spun-down cells, blots of electrophoresis gels, Western blots, dot-blots, ELISAs, antibody microarrays, nucleic acid microarrays, whole tissues or parts thereof, etc.). The method may be used to analyze any tissue, including tissue that has been clarified, e.g., through lipid elimination, for example. The sample may be prepared using expansion microscopy methods (see, e.g., <NPL>), which involves creating polymer replicas of a biological system created through selective co-polymerization of organic polymer and cell components. The method can be used to analyze spreads of cells, exosomes, extracellular structures, biomolecules deposited on a solid support or in a gel (Elisa, western blot, dot blot), whole organism, individual organs, tissues, cells, extracellular components, organelles, cellular components, chromatin and epigenetic markers, biomolecules and biomolecular complexes, for example. The capture agents may bind to any type of molecule, including proteins, lipids, polysaccharides, proteoglycans, metabolites, or artificial small molecules or the like. The method may have many biomedical applications in high throughput screening and drug discovery and the like. Further, the method has a variety of clinical applications, including, but not limited to, diagnostics, prognostics, disease stratification, personalized medicine, clinical trials and drug accompanying tests.

In particular embodiments, the sample may be a section of a tissue biopsy obtained from a patient. Biopsies of interest include both tumor and non-neoplastic biopsies of skin (melanomas, carcinomas, etc.), soft tissue, bone, breast, colon, liver, kidney, adrenal, gastrointestinal, pancreatic, gall bladder, salivary gland, cervical, ovary, uterus, testis, prostate, lung, thymus, thyroid, parathyroid, pituitary (adenomas, etc.), brain, spinal cord, ocular, nerve, and skeletal muscle, etc..

In certain embodiments, capture agents specifically bind to biomarkers, including cancer biomarkers, that may be proteinaceous. Exemplary cancer biomarkers, include, but are not limited to carcinoembryonic antigen (for identification of adenocarcinomas), cytokeratins (for identification of carcinomas but may also be expressed in some sarcomas), CD15 and CD30 (for Hodgkin's disease), alpha fetoprotein (for yolk sac tumors and hepatocellular carcinoma), CD117 (for gastrointestinal stromal tumors), CD10 (for renal cell carcinoma and acute lymphoblastic leukemia), prostate specific antigen (for prostate cancer), estrogens and progesterone (for tumour identification), CD20 (for identification of B-cell lymphomas) and CD3 (for identification of T-cell lymphomas).

The above-described method can be used to analyze cells from a subject to determine, for example, whether the cell is normal or not or to determine whether the cells are responding to a treatment. In one embodiment, the method may be employed to determine the degree of dysplasia in cancer cells. In these embodiments, the cells may be a sample from a multicellular organism. A biological sample may be isolated from an individual, e.g., from a soft tissue. In particular cases, the method may be used to distinguish different types of cancer cells in FFPE samples.

The method described above finds particular utility in examining samples using a plurality of antibodies, each antibody recognizing a different marker. Examples of cancers, and biomarkers that can be used to identify those cancers, are shown below. In these embodiments, one does not need to examine all of the markers listed below in order to make a diagnosis.

In some embodiments, the method may involve obtaining an image as described above (an electronic form of which may have been forwarded from a remote location), and the image may be analyzed by a doctor or other medical professional to determine whether a patient has abnormal cells (e.g., cancerous cells) or which type of abnormal cells are present. The image may be used as a diagnostic to determine whether the subject has a disease or condition, e.g., a cancer. In certain embodiments, the method may be used to determine the stage of a cancer, to identify metastasized cells, or to monitor a patient's response to a treatment, for example.

The compositions and methods described herein can be used to diagnose a patient with a disease. In some cases, the presence or absence of a biomarker in the patient's sample can indicate that the patient has a particular disease (e.g., cancer). In some cases, a patient can be diagnosed with a disease by comparing a sample from the patient with a sample from a healthy control. In this example, a level of a biomarker, relative to the control, can be measured. A difference in the level of a biomarker in the patient's sample relative to the control can be indicative of disease. In some cases, one or more biomarkers are analyzed in order to diagnose a patient with a disease. The compositions and methods of the disclosure are particularly suitedfor identifying the presence or absence of, or determining expression levels, of a plurality of biomarkers in a sample.

In some cases, the compositions and methods herein can be used to determine a treatment plan for a patient. The presence or absence of a biomarker may indicate that a patient is responsive to or refractory to a particular therapy. For example, a presence or absence of one or more biomarkers may indicate that a disease is refractory to a specific therapy, and an alternative therapy can be administered. In some cases, a patient is currently receiving the therapy and the presence or absence of one or more biomarkers may indicate that the therapy is no longer effective.

In any embodiment, data can be forwarded to a "remote location", where "remote location," means a location other than the location at which the image is examined. For example, a remote location could be another location (e.g., office, lab, etc.) in the same city, another location in a different city, another location in a different state, another location in a different country, etc. As such, when one item is indicated as being "remote" from another, what is meant is that the two items can be in the same room but separated, or at least in different rooms or different buildings, and can be at least one mile, ten miles, or at least one hundred miles apart. "Communicating" information refers to transmitting the data representing that information as electrical signals over a suitable communication channel (e.g., a private or public network). "Forwarding" an item refers to any means of getting that item from one location to the next, whether by physically transporting that item or otherwise (where that is possible) and includes, at least in the case of data, physically transporting a medium carrying the data or communicating the data. Examples of communicating media include radio or infra-red transmission channels as well as a network connection to another computer or networked device, and the internet or including email transmissions and information recorded on websites and the like. In certain embodiments, the image may be analyzed by an MD or other qualified medical professional, and a report based on the results of the analysis of the image may be forwarded to the patient from which the sample was obtained.

In some cases, the method may be employed in a variety of diagnostic, drug discovery, and research applications that include, but are not limited to, diagnosis or monitoring of a disease or condition (where the image identifies a marker for the disease or condition), discovery of drug targets (where the a marker in the image may be targeted for drug therapy), drug screening (where the effects of a drug are monitored by a marker shown in the image), determining drug susceptibility (where drug susceptibility is associated with a marker) and basic research (where is it desirable to measure the differences between cells in a sample).

In certain embodiments, two different samples may be compared using the above methods. The different samples may be composed of an "experimental" sample, i.e., a sample of interest, and a "control" sample to which the experimental sample may be compared. In many embodiments, the different samples are pairs of cell types or fractions thereof, one cell type being a cell type of interest, e.g., an abnormal cell, and the other a control, e.g., normal, cell. If two fractions of cells are compared, the fractions are usually the same fraction from each of the two cells. In certain embodiments, however, two fractions of the same cell may be compared. Exemplary cell type pairs include, for example, cells isolated from a tissue biopsy (e.g., from a tissue having a disease such as colon, breast, prostate, lung, skin cancer, or infected with a pathogen, etc.) and normal cells from the same tissue, usually from the same patient; cells grown in tissue culture that are immortal (e.g., cells with a proliferative mutation or an immortalizing transgene), infected with a pathogen, or treated (e.g., with environmental or chemical agents such as peptides, hormones, altered temperature, growth condition, physical stress, cellular transformation, etc.), and a normal cell (e.g., a cell that is otherwise identical to the experimental cell except that it is not immortal, infected, or treated, etc.); a cell isolated from a mammal with a cancer, a disease, a geriatric mammal, or a mammal exposed to a condition, and a cell from a mammal of the same species, preferably from the same family, that is healthy or young; and differentiated cells and non-differentiated cells from the same mammal (e.g., one cell being the progenitor of the other in a mammal, for example). In one embodiment, cells of different types, e.g., neuronal and non-neuronal cells, or cells of different status (e.g., before and after a stimulus on the cells) may be employed. In another embodiment, the experimental material contains cells that are susceptible to infection by a pathogen such as a virus, e.g., human immunodeficiency virus (HIV), etc., and the control material contains cells that are resistant to infection by the pathogen. In another embodiment, the sample pair is represented by undifferentiated cells, e.g., stem cells, and differentiated cells.

The images produced by the method may be viewed side-by-side or, in some embodiments, the images may be superimposed or combined. In some cases, the images may be in color, where the colors used in the images may correspond to the labels used.

Cells from any organism, e.g., from bacteria, yeast, plants and animals, such as fish, birds, reptiles, amphibians and mammals may be used in the subject methods. In certain embodiments, mammalian cells, i.e., cells from mice, rabbits, primates, or humans, or cultured derivatives thereof, may be used.

In order to further illustrate the present invention, the following specific examples are given with the understanding that they are being offered to illustrate the present invention and should not be construed in any way as limiting its scope.

Each antibody is conjugated to a unique oligonucleotide, which hybridizes to a shorter complementary oligonucleotide conjugated to a dye molecule. All antibodies are combined, and a target tissue (or cell spread) is stained using this cocktail. The tissue is attached to a flow cell and iterative cycles of oligonucleotide annealing and removal are performed using an auto-sampler to deliver the library of dye-oligonucleotides in sets of three for standard four color microscopes. After each hybridization step, the tissue or cell spread is imaged on a fluorescent microscope. The dye-oligonucleotides are removed using formamide solution in between each cycle. Fluorescent images from each cycle are overlaid and single-cell resolution information is extracted across all cycles and fluorescent channels.

A library of sequence orthogonal oligonucleotide probe sets were designed according to the following criteria: <NUM>) Each probe set contains an oligonucleotide sequence (oligo a) that is between <NUM>-40nt that is conjugated to an antibody and a complementary oligonucleotide, shorter in length (<NUM>-20nt) that is conjugated to a fluorescent dye (oligo b). <NUM>) Each oligo b has a melting temperature (Tm) between <NUM>-<NUM>. If the Tm is below <NUM>, oligo b does not hybridize to oligo a for the duration of imaging. If the Tm is above <NUM>, the dye-oligonucleotide (b) cannot be removed during the formamide incubation step.

The probe set library was screened for sequence overlap. The following sequences were found to have no sequence similarity.

Hybridized dye-labeled oligonucleotides are removed using an <NUM>% formamide solution with <NUM> Tris pH=<NUM>, <NUM> MgCl<NUM>, <NUM> NaCl and <NUM>% (v/v) TritonX. In order to completely remove the dye-labeled oligonucleotides during each cycle, three <NUM>-second incubations of the formamide solution on top of the sample followed by <NUM> washing steps with <NUM> Tris pH=<NUM>, <NUM> MgCl<NUM>, <NUM> NaCl and <NUM>% (v/v) TritonX are performed.

Each cycle involves the following steps:.

This process is fully automated using a pump system controlled by a custom built electronic board/python program in combination with a <NUM>-well plate compatible auto-sampler.

The basis of this technology is the ability to anneal and remove dye-labeled oligonucleotides to/from a DNA-conjugated antibody. To prove the feasibility of this, a human fresh-frozen lymph node tissue was stained with a DNA-conjugated CD3 antibody (clone UCHT1). A directly dye-labeled (Alexa647) antibody against CD19 was used as a counterstain. Iterative cycles of annealing/de-hybridization were performed. The same region of tissue was visualized on a Keyence microscope after both the hybridization/formamide steps. During each cycle, a complementary FAM-labeled oligonucleotide against the CD3 conjugated sequence (14nt, Tm=<NUM> ) was allowed to hybridize for five minutes at room temperature (~<NUM>). Formamide solution (<NUM>%) was added to the tissue and incubated for five minutes to remove the dye-labeled oligonucleotide (<FIG>&<NUM>).

The utility in this technology is improved with decreased time per cycle. To determine the minimal hybridization time, a fresh-frozen human lymph node tissue was stained with a DNA-conjugated CD3 antibody and an Alexa647 conjugated CD19 antibody. The complementary FITC-labeled oligonucleotide was added to the tissue (<NUM>) for different incubation times and the cell staining intensity was measured. Each hybridization incubation was followed by a formamide incubation (<NUM>%) to remove all hybridized oligonucleotide. The same tissue region was imaged for all tested incubation times for direct fluorescence intensity comparison. Within two minutes of hybridization, the fluorescence intensity was maximized (<FIG>).

Each cycle involves both a hybridization step and removal step using formamide. The minimum amount of time to remove all hybridized dye-labeled oligonucleotides was determined. The same tissue that was used to test the hybridization kinetics was used to test the formamide removal kinetics. The complementary dye-labeled oligonucleotide (<NUM>) was hybridized for five minutes. Formamide solution (<NUM>%) was incubated for different time periods after which the solution was washed away to halt the removal (<FIG>). Between each time point tested, additional dye-labeled oligonucleotide was added. After one minute, the dye-labeled oligonucleotide was completely removed.

Preliminary studies measuring the feasibility of repeated cycles of hybridization/removal were performed with a 14nt complementary dye-labeled oligonucleotide with a Tm=<NUM>. To determine the minimum length/Tm to achieve sufficient antibody staining for the duration of imaging (up to two hours) and the maximum length that can be removed with formamide solution, dye-labeled oligonucleotides of varying lengths were tested for both hybridization propensity/removal (<FIG> and <FIG>). It was found that dye-labeled oligonucleotides with Tms below <NUM> with a length of 10nt did not hybridize efficiently to the tissue stained with a CD3 DNA-conjugated antibody under the conditions used (<FIG>). The oligonucleotide with the next closest characteristics, 12nt in length and a Tm=<NUM>, hybridized as efficiently as all other longer dye-labeled oligonucleotides tested. Each of the hybridized dye-labeled oligonucleotides was incubated with formamide solutions for two minute intervals (<FIG>). The longest dye-labeled oligonucleotide tested was 30nt with a Tm=<NUM>. This probe was efficiently removed in an <NUM>% formamide solution. Based on these findings, optimal dye-labeled oligonucleotides for this assay should have a Tm of at least <NUM>.

Each oligonucleotide pair consists of an oligonucleotide conjugated to an antibody and a complementary sequence with a dye modification. The oligonueclodtide bound to antibody is longer in length than the dye-labeled oligonucleotide to allow a tether sequence so that the hybridization does not need to take place right next to the antibody. A library of <NUM> oligonucleotide pairs was designed and synthesized. To screen for cross-hybridization, each maleimide oligonucleotide was conjugated to a mouse CD45 antibody. Aliquots of mouse spleen cells were stained with a single oligonucleotide labeled CD45 antibody. After sufficient washes, the cells were combined and placed on a coverslip. Iterative cycles of hybridization of sets of three dye-labeled oligonucleotides were performed. Removal of dye-labeled oligonucleotides was performed in between each hybridization using formamide. Fluorescence intensities across cells corresponding to each dye-labeled oligonucleotide was measured and compared with fluorescence intensities corresponding to all other dye-labeled oligonucleotides. The fluorescence intensity values are plotted in <FIG>. A representative trace of the fluorescence intensity profile for each cell population is given in <FIG>. Some of the oligonucleotide pairs show cross-hybridization activity (T9 and T10, ee.g.). Based on the fluorescence intensity data given in <FIG>, a minimum set of oligonucleotide pairs were removed from the library of <NUM> to create a sequence-orthogonal library set. The resultant library of <NUM> oligonucleotide pairs is shown in <FIG>.

Additional oligonucleotide pairs were designed and screened similar to the first set of probes. Currently, there are <NUM> sequence orthogonal probe sets.

Each cycle involves delivery of three types of solution to the sample well: <NUM>) oligonucleotide mix, <NUM>) wash solution and <NUM>) formamide solution. For ease of use and reproducibility purposes, the fluidics was fully automated. An autosampler was programmed in line with a series of pumps controlling each solution. At each cycle, the corresponding set of three oligonucleotides is withdrawn from a designated well within a <NUM>-well plate. The solution is pumped to the sample and incubated. The entire set of commands to complete a single cycle is fully automated and controlled by a python program. To demonstrate the use of the autosampler, pairs of dye-labeled oligonucleotides were added to the first eight positions in the <NUM>-well plate. Each odd cycle well contains dye-oligonucleotides T11-cy5 and T18-cy3, while each even cycle contains T24-Cy5 and T26-Cy3. Populations of mouse spleen cells stained with CD45 antibodies conjugated to different oligonucleotides were imaged using this platform. Images of stained cells from each cycle are shown in <FIG> as well as representative cell traces across five cells from each population. As shown, the fluorescence intensity is equivalent across all odd and even cycles, indicating the autosampler delivers the dye-labeled oligonucleotide solution to the sample without any carryover.

Human tissues were stained with a cocktail of antibodies conjugated to one of the maleimide oligonucleotides. Iterative cycles of hybridization/removal were performed with imaging occurring after each hybridization step. A human tonsil (<FIG>) and human lymph node (<FIG>) were imaged using this platform. Expected staining occurred in nearly every cycle.

Claim 1:
A composition comprising:
(a) a sample comprising fixed cells;
(b) a plurality of capture agents that are each linked to a different oligonucleotide;
(c) a corresponding plurality of labeled nucleic acid probes, wherein each of the labeled nucleic acid probes specifically hybridizes with only one of the oligonucleotides of (b); and
(d) a chemical denaturant;
wherein the sample is labeled with the plurality of capture agents.