Catalyzed reporter deposition, a novel method of signal amplification. II. Application to membrane immunoassays

Rapid and sensitive detection of Escherichia coli O157:H7 in milk and ground beef using magnetic bead-based immunoassay coupled with tyramide signal amplification

Escherichia coli O157:H7 is a major foodborne pathogen that has posed serious problems for food safety and public health. Recent outbreaks and recalls associated with various foods contaminated by E. coli O157:H7 clearly indicate its deleterious effect on food safety. A rapid and sensitive detection assay is needed for this harmful organism to prevent foodborne illnesses and control outbreaks in a timely manner. We developed a magnetic bead-based immunoassay for detection of E. coli O157:H7 (the most well-known Shiga toxigenic E. coli strain) with a 96-well microplate as an assay platform. Immunomagnetic separation (IMS) and tyramide signal amplification were coupled to the assay to increase its sensitivity and specificity. This immunoassay was able to detect E. coli O157:H7 in pure culture with a detection limit of 50 CFU/ml in less than 3 h without an enrichment step. The detection limit was decreased 10-fold to 5 CFU/ml with addition of a 3-h enrichment step. When this assay was tested with other nontarget foodborne pathogens and common enteric bacteria, no cross-reactivity was found. When tested with artificially contaminated ground beef and milk samples, the assay sensitivity decreased two- to fivefold, with detection limits of 250 and 100 CFU/ml, respectively, probably because of the food matrix effect. The assay results also were compared with those of a sandwich-type enzyme-linked immunosorbent assay (ELISA) and an ELISA coupled with IMS; the developed assay was 25 times and 4 times more sensitive than the standard ELISA and the IMS-ELISA, respectively. Tyramide signal amplification combined with IMS can improve sensitivity and specificity for detection of E. coli O157:H7. The developed assay could be easily adapted for other foodborne pathogens and will contribute to improved food safety and public health.

Integrated tyramide and polymerization-assisted signal amplification for a highly-sensitive immunoassay

A novel strategy for ultrasensitive detection of model protein based on the integration of tyramide signal amplification (TSA) and polymerization-assisted signal amplification was proposed. The surface-initiated atom transfer radical polymerization (SI-ATRP) of glycidyl methacrylate (GMA) was triggered by the initiator-coupled protein immobilized on the electrode surface through sandwiched immunoreactions. Growth of long chain polymeric materials provided numerous epoxy groups for subsequent coupling of horseradish peroxidase (HRP), which in turn significantly increased the loading of quantum dots (QDs) labeled tyramide in the presence of hydrogen peroxide. As a result, electrochemiluminescence (ECL) and square-wave voltammetric (SWV) measurements showed 9.4- and 10.5-fold increase in detection signal in comparison with the unamplified method, respectively. To demonstrate the feasibility of this approach, human immunoglobulin G antigen (IgG) as a model target protein was employed and the detection limits were 0.73 and 0.09 pg mL(-1) for ECL and SWV, respectively. The results showed that sensitivity of the presented immunoassay significantly increased by one-order of magnitude and offered great application promises in providing a sensitive, specific, and potent method for biological detection.

CARD-FISH for environmental microorganisms: technical advancement and future applications

Fluorescence in situ hybridization (FISH) has become a standard technique in environmental microbiology. More than 20 years have passed since this technique was first described, and it is currently used for the detection of ribosomal RNA, messenger RNA, and functional genes encoded on chromosomes. This review focuses on the advancement and applications of FISH combined with catalyzed reporter deposition (CARD, also known as tyramide signal amplification or TSA), in the detection of environmental microorganisms. Significant methodological improvements have been made in CARD-FISH technology, including its combination with other techniques and instruments.

Evaluation of tyramide solutions for an improved detection and enumeration of single microbial cells in soil by CARD-FISH

Several tyramide solutions were evaluated for the application of fluorescence in situ hybridization with catalyzed reporter deposition (CARD-FISH) in soil. Fluorescently labeled tyramide solutions were synthesized and compared to commercially available tyramides for the detection and quantification of single microbial cells. Among the tyramide solutions tested, a succinimidyl ester of fluorescein diluted with dimethylformamide containing iodophenolboronic acid (SFX-DMF-IPBA) gave the best results, yielding highly reproducible cell numbers and detection rates of archaea and bacteria along with negligible non-specific signals. The addition of organic and inorganic compounds to the amplification reagents had a positive impact on the detection of prokaryotic cells. The applicability of SFX-DMF-IPBA for CARD-FISH in soil was further evaluated in soils of different texture. Cell numbers and detection rates of bacteria and archaea remained on a high level independent of the clay or organic matter content. Based on the results obtained in this study, the choice of the tyramide solution used for CARD-FISH has a significant influence on the detection and quantification of single microbial cells in soil. Therefore, we suggest the application of the presented tyramide signal amplification procedure including the tyramide solution SFX-DMF-IPBA for comprehensive CARD-FISH studies investigating the abundance and spatial distribution of soil microorganisms.

Experimental infection of suckling mice by subcutaneous inoculation with Oropouche virus

Oropouche virus, of the family Bunyaviridae, genus Orthobunyavirus, serogroup Simbu, is an important causative agent of arboviral febrile illness in Brazil. An estimated 500,000 cases of Oropouche fever have occurred in Brazil in the last 30 years, with recorded cases also in Panama, Peru, Suriname and Trinidad. We have developed an experimental model of Oropouche virus infection in neonatal BALB/c mouse by subcutaneous inoculation. The vast majority of infected animals developed disease on the 5th day post infection, characterized mainly by lethargy and paralysis, progressing to death within 10 days. Viral replication was documented in brain cells by in situ hybridization, immunohistochemistry and virus titration. Multi-step immunohistochemistry indicated neurons as the main target cells of OROV infection. Histopathology revealed glial reaction and astrocyte activation in the brain and spinal cord, with neuronal apoptosis. Spleen hyperplasia and mild meningitis were also found, without viable virus detected in liver and spleen. This is the first report of an experimental mouse model of OROV infection, with severe involvement of the central nervous system, and should become useful in pathogenesis studies, as well as in preclinical testing of therapeutic interventions for this emerging pathogen.

Sensitive CSF ELISAs for the detection of MBL, MASP-2 and functional MBL/MASP-2

Mannose binding lectin (MBL) mediated complement pathway is an important constituent of innate immune response in several infections including neuroinflammatory and neurodegenerative diseases. Although there are Enzyme-Linked Immunosorbent Assays (ELISAs) for estimating MBL, MBL-associated serine protease-2 (MASP-2) and functional MBL-MASP-2 (fMBL) proteins for the plasma, serum and cell supernatants there are no established methods for their estimation in the cerebrospinal fluid (CSF). We developed sensitive ELISAs for the detection of MBL, fMBL and MASP-2 in the CSF. First, we adapted standard ELISAs for the detection of these proteins in the CSF. Second, we used a biotinyl-tyramide based horseradish peroxidase (HRP) signal amplification for the sensitive detection of these proteins in the CSF. In summary, using modified ELISA and biotinyl-tyramide based HRP signal amplification, we successfully detected MBL, fMBL and MASP-2 proteins in the CSF samples with high sensitivity and reproducibility.

Development of a near-infrared fluorescence ELISA method using tyramide signal amplification

In this study, we applied tyramide signal amplification (TSA) to fluorescence enzyme-linked immunosorbent assay (ELISA) employing horseradish peroxidase (HRP) as the detection enzyme. When used with a human epidermal growth factor ELISA kit, the TSA method led to a >100-fold increase in fluorescence signal intensity in comparison to an unamplified method. It also showed wider dynamic range and better sensitivity compared to a conventional method using tetramethylbenzidine as the HRP substrate.

Histomorphometric and immunohistochemical analysis of human maxillary sinus-floor augmentation using porous β-tricalcium phosphate for dental implant treatment

OBJECTIVES

This study utilized the constitution and expression of Runx2/Cbfa1 to conduct 6-month-post-operation histomorphometrical and histochemical analysis of osteocalcin in bone regeneration following sinus-floor augmentation procedures using β-tricalcium phosphate (β-TCP) and autogenous cortical bone.

MATERIAL AND METHODS

Thirteen sinuses of nine patients were treated with sinus-floor augmentation using 50% β-TCP and 50% autogenous cancellous bone harvested from the ramus of the mandible. Biopsies of augmented sinuses were taken at 6 months for histomorphometric and immunohistochemical measurements.

RESULTS

Runx2/Cbfa1- and osteocalcin-positive cells were found around TCP particles and on the bone surface. Approximately 60% of cells found around TCP particles stained positive for Runx2/Cbfa1. Fewer cells stained positive for osteocalcin. These positive cells decreased apically with increasing vertical distance from the maxillary bone surface. Histomorphometric analysis showed that the augmented site close to residual bone and periosteum contained approximately 42% bony tissue and 42% soft connective tissue, and the remaining 16% consisted of TCP particles. On the other hand, the augmented bone far from residual bone and periosteum contained 35% bony tissue and 50% soft connective tissue.

CONCLUSIONS

Our data suggest that TCP particles attract osteoprogenitor cells that migrate into the interconnecting micropores of the bone-substitute material by 6 months. The augmented site close to residual bone contained a higher proportion of bony tissue and a lower proportion of soft connective tissue than did the augmented site far from residual bone.

Reverse-phase protein microarrays

Cancer is the consequence of intra- and extracellular signaling network deregulation that derives from alteration of genetic and proteomic cellular homeostasis. Mapping the individual molecular circuitry of a patient's tumor cells is the starting point for rational personalized therapy.While genes and RNA encode information about cellular status, proteins are considered the engine of the cellular machine, as they are the effective elements that drive cellular functions, such as proliferation, migration, differentiation, and apoptosis. Consequently, investigations of the cellular protein network are considered a fundamental tool to understand cellular functions. In the last decades, increasing interest has been focused on the improvement of new technologies for proteomic analysis. In this context, reverse-phase protein microarrays (RPMAs) have been developed to study and analyze posttranslational modifications that are responsible for principal cell functions and activities. This innovative technology allows the investigation of protein activation as a consequence of protein-protein interaction or biochemical reactions, such as phosphorylation, glycosylation, ubiquitination, protein cleavage, and conformational alterations.Intracellular balance is carefully conserved by constant rearrangements of proteins through the activity of a series of kinases and phosphatases. Therefore, knowledge of the key cellular signaling cascades reveal information regarding the cellular processes driving a tumor's growth (such as cellular survival, proliferation, invasion, and cell death) and response to treatment.Alteration to cellular homeostasis, driven by elaborate intra- and extracellular interactions, has become one of the most studied fields in the era of personalized medicine and targeted therapy. RPMA technology is a valid tool that can be applied to protein analysis of several diseases for the potential to generate protein interaction and activation maps that lead to the identification of critical nodes for individualized or combinatorial target therapy.

Mannose binding lectin mediated complement pathway in multiple sclerosis

Role of mannose binding lectin (MBL) complement activation pathway, an arm of innate immunity in multiple sclerosis (MS) was evaluated by analyzing the expression of MBL, MBL-associated serine protease-2 (MASP-2), and functional MBL/MASP-2 mediated C4 cleavage (fMBL) in 87 plasma and cerebrospinal fluid (CSF) samples from MS patients and non-MS controls. Median fMBL and MASP-2 plasma levels were higher in MS vs. non-MS cases. These associations remained in an analysis of subtypes of MS disease. These findings suggest a potential activation of MBL complement pathway in MS that may possibly alter the risk or progression of MS disease.

Novel immunohistochemical techniques using discrete signal amplification systems for human cutaneous peripheral nerve fiber imaging

Confocal imaging uses immunohistochemical binding of specific antibodies to visualize tissues, but technical obstacles limit more widespread use of this technique in the imaging of peripheral nerve tissue. These obstacles include same-species antibody cross-reactivity and weak fluorescent signals of individual and co-localized antigens. The aims of this study were to develop new immunohistochemical techniques for imaging of peripheral nerve fibers. Three-millimeter punch skin biopsies of healthy individuals were fixed, frozen, and cut into 50-µm sections. Tissues were stained with a variety of antibody combinations with two signal amplification systems, streptavidin-biotin-fluorochrome (sABC) and tyramide-horseradish peroxidase-fluorochrome (TSA), used simultaneously to augment immunohistochemical signals. The combination of the TSA and sABC amplification systems provided the first successful co-localization of sympathetic adrenergic and sympathetic cholinergic nerve fibers in cutaneous human sweat glands and vasomotor and pilomotor systems. Primary antibodies from the same species were amplified individually without cross-reactivity or elevated background interference. The confocal fluorescent signal-to-noise ratio increased, and image clarity improved. These modifications to signal amplification systems have the potential for widespread use in the study of human neural tissues.

Reverse phase protein microarrays: fluorometric and colorimetric detection

The Reverse Phase Protein Microarray (RPMA) is an array platform used to quantitate proteins and their posttranslationally modified forms. RPMAs are applicable for profiling key cellular signaling pathways and protein networks, allowing direct comparison of the activation state of proteins from multiple samples within the same array. The RPMA format consists of proteins immobilized directly on a nitrocellulose substratum. The analyte is subsequently probed with a primary antibody and a series of reagents for signal amplification and detection. Due to the diversity, low concentration, and large dynamic range of protein analytes, RPMAs require stringent signal amplification methods, high quality image acquisition, and software capable of precisely analyzing spot intensities on an array. Microarray detection strategies can be either fluorescent or colorimetric. The choice of a detection system depends on (a) the expected analyte concentration, (b) type of microarray imaging system, and (c) type of sample. The focus of this chapter is to describe RPMA detection and imaging using fluorescent and colorimetric (diaminobenzidine (DAB)) methods.

Reverse phase protein microarrays advance to use in clinical trials

Individualizing cancer therapy for molecular targeted inhibitors requires a new class of molecular profiling technology that can map the functional state of the cancer cell signal pathways containing the drug targets. Reverse phase protein microarrays (RPMA) are a technology platform designed for quantitative, multiplexed analysis of specific phosphorylated, cleaved, or total (phosphorylated and non-phosphorylated) forms of cellular proteins from a limited amount of sample. This class of microarray can be used to interrogate tissue samples, cells, serum, or body fluids. RPMA were previously a research tool; now this technology has graduated to use in research clinical trials with clinical grade sensitivity and precision. In this review we describe the application of RPMA for multiplexed signal pathway analysis in therapeutic monitoring, biomarker discovery, and evaluation of pharmaceutical targets, and conclude with a summary of the technical aspects of RPMA construction and analysis.

Human papilloma virus detection by in situ hybridisation signal amplification based on biotinylated tyramine deposition

Aim-To describe a method for amplifying human papilloma virus (HPV) in situ hybridisation (ISH) signals.Methods-Three human cervical cell lines, namely CaSKi, HeLa and SiHa, containing different copy numbers of integrated HPV DNA were studied. Following ISH, catalysed reporter deposition (CARD), based on the deposition of biotinylated tyramine at the location of the DNA probe, was used to amplify the ISH signal.Results-Using CARD-ISH, one to three HPV type 16 copies were detected in situ both in cell suspensions and paraffin wax sections of SiHa cells. CARD-ISH can also be used to detect oncogenic HPV DNA sequences, such as HPV types 16 and 18, in routinely processed formalin fixed, paraffin wax embedded cervical specimens.Conclusions-CARD-ISH is a fast and highly sensitive ISH method for the routine detection of low copy number HPV DNA sequences in cervical cell lines and routinely processed tissue sections. Application of this technology also enables the routine detection and cellular localisation of other viral DNA sequences present at copy numbers below the detection limit of conventional ISH methods.

Immunochemical detection of tissue from the central nervous system via myelin proteolipid protein: adaptation for food inspection and development of recombinant bivalent Fab mini-antibodies

Bovine spongiform encephalopathy (BSE) is transmitted by the ingestion of central nervous system (CNS) tissue of infected animals. Food inspection must, therefore, test for the presence of CNS tissue in meat and meat products. A Western blot assay for the specific CNS tissue marker myelin proteolipid protein (PLP) was optimized with considerably reduced analysis time, solvent consumption, and detection limit (0.001% CNS tissue in minced beef). Further, a PLP-specific recombinant bivalent fragment antigen binding mini-antibody (anti-PLP Fab) was obtained from a commercial phage display library. Western blot analysis with the anti-PLP Fab selectively detected CNS tissue in minced beef with a detection limit of 0.025%. Model experiments for meat processing revealed that assay sensitivity decreased with increasing temperature and prolonged heating time. A market survey with 687 sausage samples was performed using PLP-Western blot and enzyme-linked immunosorbent assay (ELISA) for glial fibrillary acidic protein (GFAP). Five samples were tested clearly positive by both assay systems, whereas in an additional six samples, CNS tissue was detected only by GFAP ELISA and in two samples only by PLP-Western blot.

In situ detection of antibiotic-resistance elements in single Bacillus cereus spores

Rapid detection of Bacillus spores is a challenging task in food and defense industries. In situ labeling of spores would be advantageous for detection by automated systems based on single-cell analysis. Determination of antibiotic-resistance genes in bacterial spores using in situ labeling has never been developed. Most of the in situ detection schemes employ techniques such as fluorescence in situ hybridization (FISH) that target the naturally amplified ribosomal RNA (rRNA). However, the majority of antibiotic-resistance genes has a plasmidic or chromosomal origin and is present in low copy numbers in the cell. The main challenge in the development of low-target in situ detection in spores is the permeabilization procedure and the signal amplification required for detection. This study presents permeabilization and in situ signal amplification protocols, using Bacillus cereus spores as a model, in order to detect antibiotic-resistance genes. The permeabilization protocol was designed based on the different layers of the Bacillus spore. Catalyzed reporter deposition (CARD)-FISH and in situ polymerase chain reaction (PCR) were used as signal amplification techniques. B. cereus was transformed with the high copy number pC194 and low copy number pMTL500Eres plasmids in order to induce resistance to chloramphenicol and erythromycin, respectively. In addition, a rifampicin-resistant B. cereus strain, conferred by a single-nucleotide polymorphism (SNP) in the chromosome, was used. Using CARD-FISH, only the high copy number plasmid pC194 was detected. On the other hand, in situ PCR gave positive results in all tested instances. This study demonstrated that it was feasible to detect antibiotic-resistance genes in Bacillus spores using in situ techniques. In addition, in situ PCR has been shown to be more sensitive and more applicable than CARD-FISH in detecting low copy targets.

Reverse-phase protein microarrays for theranostics and patient tailored therapy

Analysis of the genome provides important information about the somatic genetic changes existing in the tissue; however, it is the proteins that do the work of the cell. Diseases such as cancer are caused by derangements in cellular protein molecular networks and cell signaling pathways. These pathways contain a large and growing collection drug targets, governing cellular survival, proliferation, invasion, and cell death. The clinical utility of reverse-phase protein microarrays (RPPA), a new technology invented in our laboratory, lies in its ability to generate a functional map of known cell signaling networks or pathways for an individual patient obtained directly from a biopsy specimen. Coupled with laser capture microdissection (LCM), the RPPA platform, the entire cellular proteome is immobilized on a substratum with subsequent immunodetection of the total levels and phosphorylated, or activated, state of cell signaling proteins. The results of which pathways are "in use" can then be correlated with biological and clinical information and serve as both a diagnostic and a therapeutic guide, thus providing a "theranostic" endpoint.

Tyramide signal amplification (TSA) systems for the enhancement of ISH signals in cytogenetics

This unit provides a series of techniques that dramatically improve the sensitivity of direct and indirect in situ detection. TSA is a peroxidase-based signal amplification system which is compatible with all in situ hybridization as well as immunocytochemical detection systems. The assay is performed on a glass slide and combines the use of fluorescent probes in either direct or indirect format using either an enzyme-labeled streptavidin or antibody. Protocols are provided for brightfield and fluorescent detection of single DNA targets, DNA or RNA in cultured cells, multitarget detection for DNA/RNA and DNA and RNA. In addition a protocol is included for the TSA plus system, a DNP-based detection system using horseradish peroxidase and alkaline phosphatase.

Reverse phase protein microarrays for monitoring biological responses

Cancer has a genomic and proteomic basis. Genomic information provides information about the somatic genetic changes existing in the tumor that provides a survival advantage driving neoplastic progression. On the other hand, proteomics aids in the identification of dysregulated cellular proteins, including known or novel drug targets, governing cellular survival, proliferation, invasion, and cell death. The clinical utility of reverse phase protein microarrays lies in their ability to generate a map of known cell signaling networks or pathways for an individual patient. This protein network map aids in identifying critical nodes or pathways that may serve as drug targets for individualized or combinatorial therapy. Reverse phase protein microarrays are one of the tools available for profiling the protein molecular pathways in a given cellular sample. This type of microarray can uniquely quantify phosphorylation states of proteins. An entire cellular proteome is immobilized on a substratum with subsequent immunodetection of total and activated forms of cell signaling proteins. The pattern of signal intensity generated by the protein spots can be correlated with biological and clinical information as diagnostic and prognostic indicators.

A simplified, sensitive immunohistochemical detection system employing signal amplification based on fluorescyl-tyramide/antifluorescein antibody reaction: its application to pathologic testing and research

The catalyzed signal amplification (CSA) technique, based on the peroxidase-mediated deposition of haptenized tyramide and also known as tyramide signal amplification and catalyzed reportor deposition systems, is widely accepted as a signal amplification method for immunohistochemistry and in situ hybridization. In this study, we examined the applicability of a new simplified CSA system employing fluorescyl-tyramide (FT) to pathologic testing and research with formalin-fixed, paraffin-embedded tissues. By using the FT, instead of biotinyl-tyramide (BT) that is commonly employed in the CSA system with chromogen, nonspecific staining caused by endogenous biotin was completely avoided. The FT-CSA system loaded on the automated immunostaining equipment also allowed for more reproducible detection in short times. When applied to cyclin D1 immunostaining that is important in differentiation among small B-cell lymphomas, the system was useful in demonstrating its protein expression in mantle cell lymphomas considered negative or equivocally positive for cyclin D1 in a conventional immunodetection. In immunohistochemistry for phosphorylated proteins and murine hematologic markers that often require higher sensitivity than conventional methods, the FT-CSA system provided desirable staining results with intense signal amplification. Our results indicate that the simplified CSA system employing the FT can be useful in enlarging the target range for routine immunohistochemistry due to its high applicability.

Free-radical crosslinking of specific proteins alters the function of the egg extracellular matrix at fertilization

All animal embryos begin development by modifying the egg extracellular matrix. This protein-rich matrix protects against polyspermy, microbes and mechanical stress via enzyme-dependent transformations that alter the organization of its constituents. Using the sea urchin fertilization envelope,a well-defined extracellular structure formed within minutes of fertilization,we examine the mechanisms whereby limited permeability is established within this matrix. We find that the fertilization envelope acquires a barrier filtration of 40,000 daltons within minutes of insemination via a peroxidase-dependent mechanism, with dynamics that parallel requisite production of hydrogen peroxide by the zygote. To identify the molecular targets of this free-radical modification, we developed an in vivo technique to label and isolate the modified matrix components for mass spectrometry. This method revealed that four of the six major extracellular matrix components are selectively crosslinked, discriminating even sibling proteins from the same gene. Thus, specific free-radical chemistry is essential for establishing the embryonic microenvironment of early development.

Reverse phase protein microarrays for theranostics and patient-tailored therapy

Although the genome provides information about the somatic genetic changes existing in the tissue and underpins pathology, it is the proteins that do the work of the cell and are functionally responsible for almost all disease processes. Moreover, many diseases such as cancer are a manifestation of deranged cellular protein molecular networks and cell-signaling pathways. These pathways contain a large and growing collection of drug targets, governing cellular survival, proliferation, invasion, and cell death. Thus, the promise of proteomics resides in the study of molecules that extend beyond correlation to causality. The clinical utility of reverse phase protein microarrays, a new technology invented in our laboratory, lies in its ability to generate a functional map of known cell-signaling networks or pathways for an individual patient obtained directly from a biopsy specimen. This patient-specific circuit diagram provides key information that identifies critical nodes or pathways that may serve as drug targets for individualized or combinatorial therapy through the quantification of phosphorylation states of proteins. Using this technique, the entire cellular proteome is immobilized on a substratum with subsequent immunodetection of the phosphorylated, or activated, state of cell-signaling proteins. The results of which pathways are "in use" can then be correlated with biological and clinical information and serve as both a diagnostic and a therapeutic guide: thus providing a "theranostic" endpoint.

Visual detection of labeled oligonucleotides using visible-light-polymerization-based amplification

DNA biochip technology holds potential for highly parallel, rapid, and sensitive genetic diagnostic screening of target pathogens and disease biomarkers. A primary limitation involves a simultaneous, sequence-specific identification of low copy number target polynucleotides using a clinically appropriate detection methodology that implements only inexpensive detection instrumentation. Here, a rapid (20 min), nonenzymatic method of signal amplification utilizing surface-initiated photopolymerization is presented in glass microarray format. Visible light photoinitiators covalently coupled to streptavidin were used to bind biotin-labeled capture sequences. Amplification was achieved through subsequent contact with a monomer solution and the appropriate light exposure to generate 20-240-nm-thick hydrogel layers exclusively from spots containing the biotin-labeled DNA. An amplification factor of 10(6) to 10(7) was observed as well as a detectable response generated from as low as approximately 10(4) labeled oligonucleotides using minimal instrumentation, such as an optical microscope or CCD camera.

Reverse-phase protein microarrays: application to biomarker discovery and translational medicine

Mapping of protein signaling networks within tumors can identify new targets for therapy and provide a means to stratify patients for individualized therapy. Kinases are important drug targets, as such kinase network information could become the basis for development of therapeutic strategies for improving treatment outcome. An urgent clinical goal is to identify functionally important molecular networks associated with subpopulations of patients that may not respond to conventional combination chemotherapy. Reverse-phase protein microarrays are a technology platform designed for quantitative, multiplexed analysis of specific phosphorylated, cleaved, or total (phosphorylated and nonphosphorylated) forms of cellular proteins from a limited amount of sample. This class of microarray can be used to interrogate cellular samples, serum or body fluids. This review focuses on the application of reverse-phase protein microarrays for translational research and therapeutic drug target discovery.

Biomarker discovery using protein microarray technology platforms: antibody-antigen complex profiling

Protein microarrays represent an important new tool in proteomic systems biology. This review focuses on the contributions of protein microarrays to the discovery of novel disease biomarkers through antibody-based assays. Of particular interest is the use of protein microarrays for immune response profiling, through which a disease-specific antibody repertoire may be defined. The antigens and antibodies revealed by these studies are useful for clinical assay development, with enormous potential to aid in diagnosis, prognosis, disease staging and treatment selection. The discovery and characterization of novel biomarkers specifically tailored to disease type and stage are expected to enable personalized medicine by facilitating preventative medicine, predictive diagnostics and individualized curative therapies.

Filtration-based tyramide amplification technique—a new simple approach for rapid detection of aflatoxin B1

The catalyzed reporter deposition (CARD) method of signal amplification, also called "tyramide signal amplification", has been used in immunoassays not only to increase sensitivity but also to reduce assay time. The current approach to tyramide amplification in immunoassays involves slow incubation with agitation. In this paper we describe new filtration-based tyramide amplification and substrate visualization techniques. Compared with the standard method, this new approach greatly enhances spot intensities in membrane immunoassay and reduces biotinylated tyramide (B-T) and substrate consumption approximately fiftyfold, without loss of specificity. An improved test device and a cost-effective method for preparation of membranes for Super-CARD amplification have also been developed. The techniques have been used for rapid detection of aflatoxin B(1) (AFB(1)) in a variety of foodstuffs with a detection limit of 12.5 microg kg(-1). The assay procedure involves sequential addition of standards or sample, AFB(1)-horseradish peroxidase (HRP) conjugate, B-T, avidin-HRP, and substrate solution over anti-AFB(1) antibody-spotted zones of the membrane surface. The method saves time, improves reproducibility, eliminates many washing steps and avoids manipulation of the membranes between the different steps, while maintaining the sensitivity of the standard method. Average recoveries from different non-infected food samples spiked with AFB(1) at concentrations from 25 to 100 mg kg(-1) were between 95 and 105%. AFB(1) results obtained on different days for Aspergillus parasiticus infection of corn and groundnut samples correlated well with estimates obtained by HPLC.

Investigation of several parameters influencing signal generation in flow-through membrane-based enzyme immunoassay

Rapid-response analytical tests that can be performed at the point of sampling are based on a visual detection system. The influence of different factors on the signal generation in a membrane-based enzyme immunoassay was investigated. The research was applied to a flow-through immunoassay for the detection of ochratoxin A (OTA). This assay format is a very convenient, simple and fast qualitative screening tool. Conjugates of OTA with horseradish peroxidase (HRP) and alkaline phosphatase (AP) were used as enzyme tracers. A new conjugate OTA-AP has been synthesized in our laboratory and its performance in the assay was compared with that of OTA-HRP. Different substrate systems for HRP and AP were compared. Several reagents, including polymers and surfactants, were tested for their possible effect on signal generation with the use of OTA-HRP conjugate. Polymers such as poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) 6000 exerted a favourable effect on signal amplification, whereas surfactants negatively affected assay performance. The highest signal amplification (30-70% compared to the standard assay procedure) was achieved using 0.5% PVA in tetramethylbenzidine (TMB) Colorburst substrate solution and phosphate-buffered saline (PBS) for the washing step. It allowed more reliable visual estimation of the results from OTA-HRP assay. Exclusion of the detergent (Tween 20) from the washing solution exerted a favourable effect on assay performance using both enzyme tracers. The assay using OTA-HRP was more susceptible to matrix interferences than the assay with OTA-AP. Signal development in the matrix was better for the OTA-AP assay and visual estimation of the results was easier to perform in this case. For the analysis of spiked wheat samples, OTA-AP conjugate gave a more sensitive, stable and reproducible assay with a cut-off level of 4 microg kg(-1) for OTA. The application of the new OTA-AP conjugate resulted in improved assay performance for the food samples.

Tyramide signal amplification: an enhanced method for immunohistochemistry on methyl-methacrylate-embedded bone marrow trephine sections

The detection of cellular antigens in bone marrow sections depends on the method of embedding, the nature of antigen and antibody, antigen retrieval techniques and the sensitivity of the immunohistochemical method. This study evaluated a fluorescyl-tyramide-enhanced immunostaining method on methyl-methacrylate-embedded bone marrow trephine biopsies. Compared with the standard immunostaining technique, fluorescyl-tyramide-enhanced immunostaining showed a superior signal intensity on methyl- methacrylate-embedded bone marrow trephines. Thus, the fluorescyl-tyramide-based immunostaining method, while retaining specificity, is highly sensitive and provides optimal staining results for a broad panel of antibodies commonly used for the routine diagnosis and classification of hematological disorders.

Formation of phospho-SAPK/JNK granules in the hippocampus is an early event in Alzheimer disease

The mitogen-activated protein (MAP) kinase SAPK/JNK phosphorylates tau protein at many of its proline-directed serine/threonine residues in vitro and is a likely candidate kinase to phosphorylate the pathologically relevant S422 site on tau. Since phosphorylation of tau, particularly at S422, is a relatively early marker of AD and seems to precede tangle formation, it appears likely that an early form of activated SAPK/JNK might be detected by immunohistochemical means around the time that tau begins to aggregate into tangles. We report here that an antibody to phospho-SAPK/JNK (p-SAPK/JNK) reacts with several types of lesions including granular bodies in limbic areas; NFTs in limbic cortex and temporal neocortex; occasional neuritic plaques in temporal neocortex; and select axons in the hippocampus, entorhinal cortex, and inferior temporal cortex. In order to characterize the appearance of granular p-SAPK/JNK and determine if it appears early in disease, we employed an immunohistochemical study of postmortem limbic tissue from 20 cases ranging from Braak stages I-VI. By co-staining with anti-tau antibodies specific to different molecular events that occur during tangle evolution, we were able to identify the appearance of p-SAPK/JNK in early Braak stages with an increased elevation during the limbic stages of AD and during the early stages of the formation of individual hippocampal tangles.

Profiling cancer stem cells using protein array technology

Since cancer cells and somatic stem cells share the biological characteristics of self-renewal and proliferation, it has been suggested that the principles of stem cell biology can be applied to improve our understanding of cancer biology. Recent studies have shown that the majority of cancers appear to originate from a small subset of cells that have the ability of self-renewal and to proliferate, namely 'cancer stem cells'. The isolation of cancer stem cells has been demonstrated using cell surface markers in haematopoietic and non-haematopoietic malignancies. Advances in protein array technologies have enabled the use of minuscule amounts of biological materials to profile these cells at the molecular level. Using a combination of protein arrays and cancer stem cell isolation techniques, a higher resolution molecular profiling can be performed, which might improve therapies targeting the cancer stem cells.

Proteomics in cancer research: Methods and application of array-based protein profiling technologies

With the human genome sequence now determined, the field of molecular medicine is moving beyond genomics to proteomics, the large-scale analysis of proteins. It is now possible to examine the expression of more than 1000 proteins using mass spectrometry technology coupled with various separation methods. Microarray technology is a new and efficient approach, for extracting relevant biomedical data and has a wide range of applications. It provides a versatile tool to study protein-protein, protein-nucleic acid, protein-lipid, enzyme-substrate and protein-drug interactions. This review paper will explore the key themes in proteomics and their application in clinical cancer research.

Immunophenotyping of lymphoproliferative disorders: state of the art

Immunophenotyping was introduced into diagnostic pathology over 30 years ago to assist in the diagnosis and classification of lymphoproliferative disorders. Today the role of immunophenotyping has been expanded beyond this to include the detection of markers of prognosis, determination of disease phenotypes associated with specific chromosomal abnormalities, detection of targets for immunotherapy and to monitor residual disease. Immunoperoxidase detection methods remain the most popular in histopathology, whilst flow cytometry is most commonly applied for haematological samples. The range of monoclonal antibodies available, including those which work in routinely performed tissue specimens, continues to increase. This is in part a result of gene expression studies identifying precise genetic signatures for certain lymphoproliferative disorders and the generation of new protein markers to gene products of upregulated genes. This review summarises the current status and applications of immunophenotyping in the assessment of many of the lymphoid malignancies.

High-Resolution Immunophenotyping of Subcellular Compartments in Tissue Microarrays by Enzyme Metallography

Ultrasensitive bright field in situ hybridization assays using enzyme metallography (EnzMet) have been developed and validated, but little is known regarding the applicability of EnzMet for immunophenotypic detection of protein via IHC. Superior resolution via discrete metallographic deposits offers the potential for enhancing high-resolution immunophenotyping. Using high-complexity tissue microarrays (TMAs), 88 common solid tumors were evaluated by automated EnzMet (Nanoprobes and Ventana). Targets were chosen to assess the ability of EnzMet to specifically localize encoded antigens in the nucleus (estrogen receptor), cytoplasm (cytokeratins), and cytoplasmic membrane (HER2) in TMAs. Results were compared with conventional IHC diaminobenzidine (DAB) immunostaining. There was full concordance between the EnzMet and conventional IHC results. Furthermore, the EnzMet reaction products did not appreciably diffuse, were dense and sharply defined, and provided excellent high-resolution differentiation of cellular compartments in paraffin sections for the nuclear, cytoplasmic, and cell membrane-localized antigens evaluated. The higher density of elemental silver deposited during enzyme metallography permitted evaluation of core immunophenotypes at a relatively low magnification, allowing more tissue to be screened in an efficient manner. This preliminary study shows the utility of using enzyme metallography for high-resolution immunophenotyping in TMAs.

A new simplified catalyzed signal amplification system for minimizing non-specific staining in tissues with supersensitive immunohistochemistry

We investigated non-specific staining in a catalyzed reporter deposition (CARD) reaction and improved its blocking methods in supersensitive immunohistochemistry, based on our simplified catalyzed signal amplification (CSA) system (Hasui et al. 2002). In the CARD reaction using biotinyl tyramide, non-specific staining could be reduced by pretreatment with a casein solution or 3% bovine serum albumin (BSA)-phosphate buffer saline (PBS) with 0.1% Tween 20. In the CARD reaction using FITC-labeled tyramide, non-specific staining could be blocked by pretreatment with 0.3% BSA-PBS with 0.1% Tween 20 or 3% polyethylene glycol-PBS with 01% Tween 20. Thus, our new simplified CSA system features: 1) destruction of the endogenous peroxidase activity; 2) blocking of the nonspecific reaction of the primary antibody; 3) a primary antibody reaction; 4) blocking of the non-specific reaction of the polymer reagent by casein treatment; 5) a polymer reaction; 6) blocking of the non-specific reaction of CARD reaction by casein treatment; 7) a CARD reaction; and 8) detection of deposited tyramide. This new system proved useful for detecting an extremely low amount of antigen in the endogenous biotin-rich tissues such as the gastrointestinal tract and liver. By this method, the Ki67 antigen in the G1 phase cell cycle could be detected and a metabolic disorder of the Ki67 antigen was implicated in a carcinoid tumor in the stomach. We believe that this new simplified CSA system represents a new standard of supersensitive immunohistochemistry for use in light-microscopic investigation.

Protein microarray detection strategies: focus on direct detection technologies

Protein microarrays are being utilized for functional proteomic analysis, providing information not obtainable by gene arrays. Microarray technology is applicable for studying protein-protein, protein-ligand, kinase activity and posttranslational modifications of proteins. A precise and sensitive protein microarray, the direct detection or reverse-phase microarray, has been applied to ongoing clinical trials at the National Cancer Institute for studying phosphorylation events in EGF-receptor-mediated cell signaling pathways. The variety of microarray applications allows for multiple, creative microarray designs and detection strategies. Herein, we discuss detection strategies and challenges for protein microarray technology, focusing on direct detection of protein microarrays.

Adenovirus-mediated overexpression of tissue inhibitor of metalloproteinases-1 in the liver: efficient protection against T-cell lymphoma and colon carcinoma metastasis

BACKGROUND

Matrix metalloproteinases (MMPs) are critical for metastasis of tumor cells. Tissue inhibitor of metalloproteinases-1 (TIMP-1), a natural MMP inhibitor, was shown to reduce metastasis in different models. Here, we investigated whether increased TIMP-1 levels in the liver achieved by adenoviral gene transfer will effectively inhibit liver metastasis of two independent tumor cell lines.

METHOD

TIMP-1 was transferred with adenoviral vectors into the livers of DBA/2 and Balb/c mice, which were subsequently challenged by hematogenous experimental metastases of the T-cell lymphoma cell line L-CI.5s or the colorectal carcinoma cell line CT-26, respectively.

RESULTS

MMP-9 expression in the liver was induced upon metastasis in both tumor types. Adenoviral gene transfer led to high transduction efficacy as indicated by lacZ expression in 60% of hepatocytes. TIMP-1, a key inhibitor of MMP-9, was expressed at 10(5)-fold higher levels by adenoviral gene transfer as compared with levels achieved in TIMP-1 transgenic mice, previously shown to be inefficient to reduce T-cell lymphoma metastasis. High local and systemic (serum) levels of TIMP-1 led to substantial (94%) reduction of T-cell lymphoma and colorectal carcinoma (73%) experimental liver metastasis.

CONCLUSIONS

Adenoviral gene transfer led to systemic and local TIMP-1 levels sufficient to inhibit metastasis of a highly aggressive T-cell lymphoma, pointing at the requirement of threshold levels for effective anti-metastatic efficacy. This approach was also efficient in a colon carcinoma solid tumor model. We propose that viral gene transfer of TIMP-1 can provide a suitable defense strategy to prevent metastatic spread to the liver.

Use of proteomic analysis to monitor responses to biological therapies

Proteomics has the potential to revolutionise diagnosis and disease management. Serum protein pattern profiling by surface-enhanced laser desorption/ionisation time of flight (SELDI-TOF) mass spectrometry is emerging as a novel approach to discover protein patterns capable of distinguishing disease and disease-free states with high sensitivity and specificity. This method has shown great promise for early diagnosis of ovarian cancer and is being applied to a range of pathological states. Protein microarray technology is being evaluated as a new means to track biological responses to therapy. Through the measurement of key protein phosphorylation sites at different stages of disease progression or before and after treatment, protein signal pathways can be mapped and thus become the starting point for individualised therapy. Laser capture microdissection (LCM) coupled with immunostaining of protein microarrays allows isolation of pure cell populations and relative quantitation of phosphorylated and non-phosphorylated forms of the cell's key signalling proteins. This technology is currently in use at the National Institutes of Health in Phase II clinical trials of metastatic breast and ovarian cancer. Cell survival and apoptotic protein pathways are monitored as biological markers of disease progression in these clinical trials. Proteomic technologies, such as serum protein pattern profiling, combined with protein microarray technologies, constitute a new paradigm for detecting disease and monitoring disease response to therapy. Ultimately, proteomics and genomics will become integrated into cancer patient management through the design and tracking of individualised therapy.

Comparison of contrast, sensitivity and efficiency of signal amplified and nonamplified immunohistochemical reactions suitable for videomicroscopy-based quantification and neuroimaging

In recent years, many different technical modifications of immunohistochemical methods have been developed. The selection of a suitable technique for quantitative purposes such as mapping studies can be quite difficult. Various features of a certain method must be considered such as the sensitivity, costs, duration and practicability with respect to serial sectioned specimens. Background and foreground difference or contrast and the influence of artifacts are major problems of quantitative immunohistochemistry. It is not known which of the different modifications of immunohistochemical signal amplifications and non-amplifications gives optimal results in respect to image analytical-based quantification. However, for image analysis, it is important to analyze sections which offer a sufficient contrast between foreground and background. The sensitivity of a system is crucial when quantitative immunohistochemistry should be applied to scarce material with longer postmortem and storage times which occur often by processing human brains. In addition, the enzyme-substrate reactions have an obvious influence on this criterion; therefore, different substrates were also tested. The contrast may be as well effected by the quality and specificity of the primary antibody, the type of tissue and naturally by preparative (fixation, postmortem delay, storage) and individual factors (age, circadian effects, diseases, sex). Because all of these factors may yield to different results by combining them with different neuronal structures, we used three different antigen expressions for a specific analysis: fibrillary, granulary and perikaryal antigen distributions in brains from Wistar rats. Principally, the sensitivity of the modifications of immunohistochemical amplifications is revealed more strongly than without enhancement steps; however, the contrast between foreground and background structures does not necessary increase by applying a certain amplification technique. The lowest contrast (15%) was detected after applying the labelled streptavidin-biotin technique. All other methods offer comparable contrasts in between 30% and 40%. The catalyzed signal amplification reaction has been found to give optimal results (40% contrast) for image analysis. However, from the technical point of view and variability of protein expression, storage and postmortem delay, it was necessary to adapt the commercial CSA Kit from Dako (K1500). The modified technique, called C2 method, offers better results with respect to sensitivity, total costs, duration and contrast (60%) and variability of contrast.

Expression of leptin receptor (Ob-R) isoforms and signal transducers and activators of transcription (STATs) mRNAs in the mouse taste buds

Leptin is a hormone that regulates food intake, energy expenditure and body weight. Our previous studies have demonstrated that the taste organ is a new peripheral target for leptin in mice. Leptin selectively inhibits the responses of taste nerves and receptor cells to sweet substances without affecting responses to sour, salty, and bitter substances. Still, there is no convincing evidence for the existence of leptin receptors (Ob-Rs) in taste receptor cells, especially the functional isoform Ob-Rb. We investigated the expression of 5 different Ob-R isoforms (a-e) and 6 STAT (signal transducers and activators of transcription) members in mouse taste cells. STATs are considered to be involved in the leptin signaling via Ob-Rb. Semiquantitative RT-PCR analysis showed that Ob-Rb was expressed in the taste buds of the fungiform and circumvallate papillae, but not so clearly in the surrounding epithelial tissue. The expression pattern among the three different tissues was similar to that of the taste cell specific G-protein, alpha-gustducin. The other Ob-R isoforms were widely detected in either the taste papillae or the epithelial tissue. Among 6 STAT members, STAT3 showed the highest relative abundance of mRNA in the taste buds. Consistently, in situ hybridization analysis showed that while Ob-Rb and STAT3 signals were detected in some taste bud cells, the signals were not clearly observed in the epithelial tissue cells. In conclusion, the present study provides evidence of the existence of the leptin receptor, Ob-Rb, and STAT3 in the mouse taste bud cells. This finding further confirms the involvement of leptin in the control of taste sensitivities to sweet substances in mice.