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Optimizing the integration of immunoreagents and fluorescent probes for multiplexed high content screening assays.

Immunoreagents formed the basis of early fixed end point high content screening (HCS) assays and their use in HCS applications in drug discovery will continue to increase. One important application of immunoreagents is their incorporation into multiplexed HCS assays in which multiple physiological features are simultaneously measured and related in the same cells. However, creating multiplexed HCS assays that incorporate multiple immunoreagents presents issues such as reagent compatibility, spectral signal overlap, and reproducibility that must be addressed. Here, an example multiplexed fixed end point HCS assay is used to guide potential assay developers on how to optimize complex, yet cellular information rich, multiplexed HCS assays although avoiding some common pitfalls.

Antibodies↗

Multiplex pyrosequencing for DNA variation analysis.

Pyrosequencing technique has been widely used to perform both single-nucleotide polymorphism detection and quantitative DNA methylation analysis. Simplex Pyrosequencing is sufficient to interrogate more than one polymorphic site if these gene variants are within the reach of the sequencing reaction. For polymorphisms far apart from each other or located on different genes, multiple simplex analyses are required. To reduce the number of simplex reactions, multiplex Pyrosequencing becomes a useful alternative method. The multiplex reaction is performed in the presence of single or multiple templates with several sequencing primers. Factors such as primer selection for the PCR and Pyrosequencing reaction, generation of optimal nucleotide dispensation order, use of internal and external controls, preparation of instrumentation, and Pyrogram interpretation are essential to the success of the multiplexing. In this chapter, the mouse 45S rRNA gene is used to present two general multiplex Pyrosequencing protocols for determining DNA methylation and allele frequency in the spacer promoter region of this gene.

Animals↗

Immunobead multiplex RT-PCR detection of carcinoembryonic genes expressing cells in the blood of colorectal cancer patients.

Circulating cell detection using reverse transcriptase-polymerase chain reaction (RT-PCR) techniques has been studied as a new prognostic factor in colorectal cancer patients. With the view of enhancing detection sensitivity, we developed a new multiplex RT-PCR assay for circulating cell detection based on the expression of carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5; formerly CEA) and CEACAM7 (formerly CGM2). Between November 2002 and December 2003, 45 stage III-IV, 39 stage I-II colorectal cancer patients, 32 non-colorectal cancer patients and 41 healthy individuals were included. Positive selection using HEA-125 immunobeads was applied to blood samples before mRNA extraction, cDNA synthesis and a multiplex CEACAM5/CEACAM7 RT-PCR assay. For both CEACAM5 and CEACAM7, the limit of detection was found to be as low as 1 expressing cell in 10(6) nucleated blood cells. The multiplex RT-PCR assay was negative for the 41 healthy individuals and the 32 non-colorectal cancer patients. The test was positive in 53/84 (63%) of the colorectal cancer patients for CEACAM5 and/or CEACAM7, whereas 32/84 (38%) were positive for both markers. Colorectal cancer patients were positive for one of the two markers in 80% of cases (36/45) for stage III-IV patients (CEACAM5 73%, CEACAM7 51%) and in 44% of cases (17/39) for stage I-II patients. This multiplex RT-PCR assay with two markers proved to be more sensitive than use of a single marker in detecting circulating tumour cells. The discrepant expression of CEACAM5 and CEACAM7 may label circulating tumour cells that have different levels of differentiation and subsequent aggressive behaviour.

Aged↗

Multiplexed molecular detection using encoded microparticles and nanoparticles.

Signal-encoded microparticles and nanoparticles have been used to label many reactions simultaneously for target identification in assays, and thus are an indispensable part of multiplex technologies. With the increasing demand for multiplexed molecular detection, encoded particles have evolved from pattern encoding to signal-intensity encoding, and also from signal-molecule encapsulation to signal-molecule tagging. The fabrication and utilization of such nano- and microparticles should advance multiplexed analysis. This short review focuses on how these encoded particles work and briefly touches on their applications in multiplexed molecular detection.

Biological Assay↗

Rapid detection of virulence-associated genes in avian pathogenic Escherichia coli by multiplex polymerase chain reaction.

Based on recently published prevalence data of virulence-associated factors in avian pathogenic Escherichia coli (APEC) and their roles in the pathogenesis of colibacillosis, we developed a multiplex polymerase chain reaction (PCR) as a molecular tool supplementing current diagnostic schemes that mainly rely on serological examination of strains isolated from diseased birds. Multiple isolates of E. coli from clinical cases of colibacillosis known to possess different combinations of eight genes were used as sources of template DNA to develop the multiplex PCR protocol, targeting genes for P-fimbriae (papC), aerobactin (iucD), iron-repressible protein (irp2), temperature-sensitive hemagglutinin (tsh), vacuolating autotransporter toxin (vat), enteroaggregative toxin (astA), increased serum survival protein (iss), and colicin V plasmid operon genes (cva/cvi). In order to verify the usefulness of this diagnostic tool, E. coli strains isolated from fecal samples of clinically healthy chickens were also included in this study, as were uropathogenic (UPEC), necrotoxigenic, and diarrhegenic E. coli strains. The application of the multiplex PCR protocol to 14 E. coli strains isolated from septicemic poultry showed that these strains harbored four to eight of the genes mentioned above. In contrast, those isolates that have been shown to be nonpathogenic for 5-wk-old chickens possessed either none or, at most, three of these genes. We found only one enterohemorrhagic (EHEC), one enteropathogenic (EPEC), and two enterotoxic (ETEC) E. coli strains positive for irp2, and another two ETEC strains positive for astA. As expected, UPEC isolates yielded different combinations of the genes iss, papC, iucD, irp2, and a sequence similar to vat. However, neither the colicin V operon genes cva/cvi nor tsh were amplified in UPEC isolates. The multiplex PCR results were compared with those obtained by DNA-DNA-hybridization analyses to validate the specificity of oligonucleotide primers, and the protocol was concluded to be a useful, sensitive, and rapid assay system to detect avian pathogenic E. coli and differentiate them from nonpathogenic strains and those belonging to other pathotypes.

Animals↗

Multiplex automated primer extension analysis: simultaneous genotyping of several polymorphisms.

Accurate and fast genotyping of single nucleotide polymorphisms (SNPs) is of significant scientific importance for linkage and association studies. We report here an automated fluorescent method we call multiplex automated primer extension analysis (MAPA) that can accurately genotype multiple known SNPs simultaneously. This is achieved by substantially improving a commercially available protocol (SNaPshot). This protocol relies on the extension of a primer that ends one nucleotide 5'of a given SNP with fluorescent dideoxy-NTPs (minisequencing), followed by analysis on an ABI PRisMS 377 Semi-Automated DNA Sequencer Our modification works by multiplexing the initial reaction that produces the DNA template for primer extension and/or multiplexing several primers (corresponding to several SNPs) in the same primer extension reaction. Then, we run each multiplexed reaction on a single gel lane. We demonstrate that MAPA can be used to genotype up to four SNPs simultaneously, even in compound heterozygote samples, with complete accuracy (based on concordance with sequencing results). We also show that primer design, unlike the DNA template purification method, can significantly affect genotyping accuracy, and we suggest useful guidelines for quick optimization.

DNA Primers↗

Simultaneous detection of mastitis pathogens, Staphylococcus aureus, Streptococcus uberis, and Streptococcus agalactiae by multiplex real-time polymerase chain reaction.

The objective of this study was to develop a multiplex real-time polymerase chain reaction (PCR) method for simultaneous detection of Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus uberis directly from milk. A genetic marker specific for Staph. aureus was used for primers and dual-labeled probe design. The target for Strep. agalactiae primers and dual-labeled probe was selected from the cfb gene encoding the Christie-Atkins-Munch-Petersen factor. The plasminogen activator gene was the target for primers and dual-labeled probe design for Strep. uberis. Quarter milk samples (n = 192) were analyzed by the multiplex real-time PCR assay and conventional microbiological methods. An additional 57 quarter milk samples were analyzed in a separate real-time PCR assay for Strep. agalactiae only. Using an overnight enrichment step, the real-time PCR technique correctly identified 96.4% of all quarter milk samples; 91.7% of Staph. aureus, 98.2% of Strep. agalactiae, and 100% of Strep. uberis. Results of conventional microbiological methods were used to determine the sensitivity and specificity of the multiplex real-time PCR procedure. The sensitivity of the procedure to correctly identify Staph. aureus, Strep. agalactiae, and Strep. uberis directly from milk was 95.5%, and the specificity was 99.6%. Results of this study indicate that the multiplex real-time PCR procedure has the potential to be a valuable diagnostic technique for simultaneous identification of Staph. aureus, Strep. agalactiae, and Strep. uberis directly from quarter milk samples.

Animals↗

Detection of enteroviruses and hepatitis A virus in water by consensus primer multiplex RT-PCR.

AIM: To develop a rapid detection method of enteroviruses and Hepatitis A virus (HAV). METHODS: A one-step, single-tube consensus primers multiplex RT-PCR was developed to simultaneously detect Poliovirus, Coxsackie virus, Echovirus and HAV. A general upstream primer and a HAV primer and four different sets of primers (5 primers) specific for Poliovirus, Coxsacki evirus, Echovirus and HAV cDNA were mixed in the PCR mixture to reverse transcript and amplify the target DNA. Four distinct amplified DNA segments representing Poliovirus, Coxsackie virus, Echovirus and HAV were identified by gel electrophoresis as 589-,671-, 1084-, and 1128bp sequences, respectively. Semi-nested PCR was used to confirm the amplified products for each enterovirus and HAV. RESULTS: All four kinds of viral genome RNA were detected, and producing four bands which could be differentiated by the band size on the gel. To confirm the specificity of the multiplex PCR products, semi-nested PCR was performed. For all the four strains tested gave positive results. The detection sensitivity of multiplex PCR was similar to that of monoplex RT-PCR which was 24 PFU for Poliovrus,21 PFU for Coxsackie virus,60 PFU for Echovirus and 105 TCID(50) for HAV. The minimum amount of enteric viral RNA detected by semi-nested PCR was equivalent to 2.4 PFU for Poliovrus, 2.1 PFU for Coxsackie virus, 6.0 PFU for Echovirus and 10.5 TCID(50) for HAV. CONCLUSION: The consensus primers multiplex RT-PCR has more advantages over monoplex RT-PCR for enteric viruses detection, namely, the rapid turnaround time and cost effectiveness.

Base Sequence↗

Evaluation of an enzyme-linked immunosorbent assay, direct immunofluorescent filter technique, and multiplex polymerase chain reaction for detection of Escherichia coli O157:H7 seeded in beef carcass wash water.

In commercial beef processing, carcasses are customarily washed with water to remove physical and microbial contamination. Assaying the water that is shed from the carcasses after washing is a convenient method to determine whether the carcass is contaminated with Escherichia coli O157:H7 or other bacterial pathogens. E. coli O157:H7 was inoculated into carcass wash water at various levels and the bacteria were then concentrated by filtration. After collection of bacteria in the filter units, the nylon membranes were cut out and placed in tubes containing growth medium, and the tubes were mixed vigorously to dislodge the bacteria from the membranes. Prior to enrichment, samples were removed for testing by a multiplex polymerase chain reaction (PCR) and a direct immunofluorescent filter technique (DIFT). The remaining samples were subjected to 4-h enrichment culturing at 37 degrees C, after which aliquots were removed for testing by multiplex PCR, DIFT, and an enzyme-linked immunosorbent assay (ELISA). Following 4-h enrichment culturing, E. coli O157:H7 was detected in wash water samples initially inoculated with ca. 100, 0.1, and 1 CFU/ml by ELISA, DIFT, and multiplex PCR, respectively. Testing of the wash water using the ELISA and the DIFT can be accomplished in less than 8 h. On the basis of these results, assaying carcass wash water by ELISA, DIFT, or multiplex PCR can be useful for detection of E. coli O157:H7 beef carcass contamination and can potentially be employed to identify carcasses for further processing to inactivate the organism.

Animals↗

Detection of aflatoxin-producing molds in Korean fermented foods and grains by multiplex PCR.

An assay based on multiplex PCR was applied for the detection of potential aflatoxin-producing molds in Korean fermented foods and grains. Three genes, avfA, omtA, and ver-1, coding for key enzymes in aflatoxin biosynthesis, were used as aflatoxin-detecting target genes in multiplex PCR. DNA extracted from Aspergillus flavus, Aspergillus parasiticus, Aspergillus oryzae, Aspergillus niger, Aspergillus terreus, Penicillium expansum, and Fusarium verticillioides was used as PCR template to test specificity of the multiplex PCR assay. Positive results were achieved only with DNA that was extracted from the aflatoxigenic molds A. flavus and A. parasiticus in all three primer pairs. This result was supported by aflatoxin detection with direct competitive enzyme-linked immunosorbent assay (DC-ELISA). The PCR assay required just a few hours, enabling rapid and simultaneous detection of many samples at a low cost. A total of 22 Meju samples, 24 Doenjang samples, and 10 barley samples commercially obtained in Korea were analyzed. The DC-ELISA assay for aflatoxin detection gave negative results for all samples, whereas the PCR-based method gave positive results for 1 of 22 Meju samples and 2 of 10 barley samples. After incubation of the positive samples with malt extract agar, DC-ELISA also gave positive results for aflatoxin detection. All Doenjang samples were negative by multiplex PCR and DC-ELISA assay, suggesting that aflatoxin contamination and the presence of aflatoxin-producing molds in Doenjang are probably low.

Aflatoxins↗

Risk free simultaneous prenatal identification of fetal Rhesus D status and sex by multiplex real-time PCR using cell free fetal DNA in maternal plasma.

QUESTIONS UNDER STUDY: Pregnancies with a Rhesus constellation still present a considerable obstetric problem. In addition, pregnancies with male Rhesus D fetuses are more severely affected by haemolytic disease of the newborn, requiring more transfusions in utero and having a three fold higher mortality than female Rhesus D fetuses. Furthermore, almost 150 X-linked genetic deficiencies have now been characterised, increasing the need for prenatal sex determination in pregnancies at risk for such a disorder. In order examine these two important fetal loci in a risk free manner, we have developed a novel multiplex real-time PCR assay for the analysis of extracellular fetal DNA in maternal plasma. METHODS: Cell free DNA was isolated from 34 maternal plasma samples and examined by a multiplex real-time PCR assay for the Rhesus D gene and the SRY locus on the Y chromosome. RESULTS: Our study showed that we were able to genotype 12/13 Rhesus D males correctly. All 5 Rhesus d males were correctly identified. In addition a 100% concordance was found in the 16 samples obtained from pregnancies with female Rhesus D or Rhesus d fetuses. CONCLUSIONS: By developing a novel multiplex real-time PCR assay we present the first report describing the determination of multiple fetal loci from cell free DNA in maternal plasma by these means. As this assay is suitable for automation, our data, therefore, suggest that such assays provide a good basis for the clinical examination of multiple fetal loci, in particular Rhesus D status or fetal sex, and can be performed effectively using real-time multiplex PCR assays.

DNA↗

[Simultaneous detection and differentiation of O1 classical E1 Tor, O139 and nonO1 nonO139 strains of Vibrio cholerae by using multiplex PCR].

OBJECTIVE: To explore the rapid and sensitive procedures for detection and differentiation of O1 classical(CVC), El Tor(EVC), O139 and nonO1 nonO139 strains of Vibrio cholerae. METHODS: Four pairs of primers were designed from toxin sub-unit A(ctxA) gene, O139 special gene, Haemolytic subunit A gene and Toxin coregulated pilus subunit A gene. Multiplex PCR was established to simultaneously detect those four genes. CVC, EVC, O139 and nonO1 nonO139 strains can be detected and differentiated by the size and numbers of Multiplex PCR bands via electrophoresis. Two pairs of inside primers were designed from ctx A and O139 special gene, and a nested PCR was established. RESULTS: 60 EVC, 2 CVC, 15 O139 and 30 nonO1 nonO139 strains isolated from patients were detected with multiplex PCR and nested PCR, and the results were correct. 10 EVC and 15 O139 strains isolated from environment samples were detected, and the results meant that EVC were toxic and O139 were non-toxic. The sensitivity of multiplex PCR reached 100 cfu, and that of nested PCR reached 1-10 cfu. CONCLUSION: This method is rapid, specific, and sensitive, and possess great value for practical application.

DNA, Bacterial↗

Multiplex-polymerase chain reaction assay for the detection of prognostically significant translocations in acute lymphoblastic leukemia.

BACKGROUND AND OBJECTIVES: The presence of specific chromosomal translocations in acute lymphoblastic leukemias (ALL) plays an important role in determining the prognosis of the patients. Our aim is to develop a highly sensitive and specific method to screen simultaneously for the four most frequent translocations in ALL: t(9;22), t(1;19), t(4;11), t(12;21). DESIGN AND METHODS: Our approach uses a multiplex-polymerase chain reaction (PCR) method, which involves two rounds of PCR using fluorescence-labeled nested primers. The chimeric transcripts resulting from these translocations can be identified by agarose gel electrophoresis or by fluorescence analysis. To validate this method we carried out the analysis in 42 pediatric ALL samples previously studied by cytogenetic and fluorescent in situ hybridization (FISH) techniques. RESULTS: In all samples with a known translocation detected by cytogenetic or FISH techniques, the same translocation was identified by the multiplex-PCR assay. Moreover, with this method we detected rearrangements in five patients in clinical remission and in two patients at diagnosis for whom karyotypes were normal and rearrangements had not been detected. The application of this multiplex-PCR assay was also useful in cases without cytogenetic results. INTERPRETATION AND CONCLUSIONS: These results show that the multiplex-PCR method allows reliable, sensitive and rapid detection of the prognostically significant translocations in ALL. We believe that this assay combined with cytogenetic analysis should be the strategy of choice for the initial diagnostic phase of acute lymphoblastic leukemia, and that it could be used not only at diagnosis but also to follow-up these alterations in remission samples without previous controls.

Child↗

Modification of the multiplex PCR for unambiguous differentiation of the El Tor & classical biotypes of Vibrio cholerae O1.

BACKGROUND & OBJECTIVES: Biotyping of Vibrio cholerae O1 using multiplex PCR (ctxA-tcpA) exploits the nucleotide sequence differences of the major subunit protein of the toxin co-regulated pilus (TCP) gene (tcpA) to differentiate between the classical and El Tor biotypes. However, the presence of classical biotype specific tcpA amplicon with the El Tor strains often complicates the interpretation. The effect of PCR variables on the amplification of biotype specific tcpA in the multiplex PCR has been investigated. METHODS: Reference strains of toxigenic V. cholerae O1 belonging to classical and El Tor biotypes were selected to optimize the PCR variables for the unambiguous biotype determination by multiplex PCR. RESULTS: In the multiplex PCR assay, a reduction in the reaction volume from 100 microliters to 25 microliters and the annealing temperature of 64 degrees C, the El Tor strain produced ctxA amplicon (302 bp) along with tcpA amplicons of 618 bp and 472 bp which are specific for classical and El Tor tcpA respectively. The simplex PCR with biotype specific tcpA primer pairs showed the amplification of either 472 bp or 618 bp tcpA amplicon with El Tor template. With the classical biotype strain, the specific primer pair yielded tcpA amplicon of the expected size. Lowering of PCR annealing temperature from 64 to 60 degrees C resulted in the elimination of the amplification of the nonspecific tcpA amplicon with El Tor strain. INTERPRETATION & CONCLUSION: A comparison of the theoretical melting temperature (Tm) values of the reacting primers, and their alignment to the biotype specific tcpA revealed the basis of unambiguous biotyping of V. cholerae O1 at a PCR annealing temperature of 60 degrees C.

Bacterial Outer Membrane Proteins↗

Constructing universal multiplex PCR systems for comparative genotyping.

Analysis of length polymorphisms at STR loci in the human genome has become a standard approach for comparative genotyping in many areas including disease research and diagnostics, parentage assessment, investigations of human diversity, and forensic science. The simultaneous analysis of multiple STR loci through multiplex PCR and multicolor fluorescence detection offers sample conservation, high throughput, and automated genetic analysis. Careful design and optimization of tetranucleotide STR multiplexes has led to reliable, standardized systems that powerfully differentiate and distinguish individual human DNA profiles. The development of these multiplex systems involved a rigorous experimental strategy that included careful selection of PCR primer sequences (for yield, specificity, and multiplex compatability), along with optimization of PCR component concentrations, thermal cycling parameters, and fluorescence detection conditions. This developmental approach rendered well-characterized DNA typing systems that are high performing (sensitive, specific, and balanced), optimized to universal parameters (same reaction conditions), resilient to fluctuations in reaction conditions, and simple to implement and use routinely.

DNA↗

[Application of multiplex PCR in genotyping of hepatitis B virus prevailing in Guangdong Province of China].

OBJECTIVE: To establish a convenient method for the genotyping of hepatitis B virus (HBV) using multiplex PCR. METHOD: Based on the alignment of 114 complete nucleotide sequences of HBV DNA belonging to different genotypes, acquired from the GenBank, genotype-specific sequences were identified according to which 6 pairs of primers were designed corresponding to each genotype. Subsequent genotyping of HBV was performed using these primers that were added, either alone or in conjunction with others, into a multiplex PCR reaction tube, and HBV genotype was determined according to the length of amplified DNA. RESULT: The genotyping result of multiplex PCR was consistent with that produced by PCR- restriction fragment length polymorphism as established by Lindh. We found in this study that among the HBV carriers in the vicinities Guangzhou of City, about 45% belonged to B genotype, 38.75% to C genotype and 16.75% to D genotype. CONCLUSION: This multiplex PCR method is simple, convenient and more differential.

China↗

Multiplex PCR for detection of stx genes of Escherichia coli.

BACKGROUND & OBJECTIVE: Shiga toxin producing Escherichia coli (STEC), which includes both enterohaemorrhagic Esch. coli (EHEC, 0157: 7H) and non-EHEC (non-0157) produces two major Shiga toxins (Stx1 & Stx2). Detection of Stx or stx genes is the only approach to detect all the different types of STEC. A multiplex PCR is used for the detection of stx genes from EHEC and non-EHEC strains isolated from patients of enteritis. METHODS: Ten EHEC and 35 non-EHEC strains obtained from patients with diarrhoea and enteritis were studied. A single and multiplex PCR (mPCR) were used for detection of stx genes using specific primers. In single PCR, the stx 1 and stx 2 genes were amplified separately while in mPCR, the two genes were amplified together in a single reaction. The PCR products were detected by electrophoresis. RESULTS: All the EHEC strains were found to harbour one or both stx genes as detected by single and multiplex PCR. Of the non-EHEC strains tested, 14.28 per cent were positive for stx genes. Multiplex PCR gave similar results and showed 100 per cent agreement with that of single PCR. INTERPRETATION & CONCLUSION: The results indicated that stx genes are common in the EHEC strains but they are less prevalent among non-EHEC strains. Because of simplicity, rapidity and specificity, mPCR assay represents a good alternative to traditional methods for the detection of stx genes of STEC.

Escherichia coli↗

[Studies on detection of Plasmodium falciparum and Plasmodium vivax in blood samples by multiplex polymerase chain reaction].

AIM: To establish a sensitive and specific PCR-based method to detect Plasmodium falciparum and P. vivax in blood samples in a single amplification reaction. METHODS: Malaria parasite DNA in blood was amplified by the multiplex polymerase chain reaction using two sets of primers derived from the P. f. moderately-repetitive DNA sequence and COIII gene of P.v. RESULTS: A 206-bp product for P. f. and a 370-bp product for P.v. were amplified by multiplex PCR, being able to detect parasitemia level as low as 5 x 10(-7) for P. f. and 1.02 x 10(-6) for P. v. and having no cross-reaction with human leucocyte DNA. A total of 783 blood samples on the filter paper collected from patients attending to malaria clinics in malaria endemic areas were detected. The positive rate of multiplex PCR was 85.8%, the misdiagnosis rate was 0, and the under-diagnosis rate was 0.1%, while these three rates of microscopic examination were 84.9%, 3.1% and 1.0%, respectively. The concordance between the two methods was 95.8%. CONCLUSION: The multiplex PCR method made the malaria detection more sensitive and specific than the microscopic examination and should be suitable for the diagnosis of malaria in mixed endemic areas, large-scale epidemiological studies, follow-up of drug treatment and donor blood screening.

Animals↗