Design and validation of an immuno-PCR assay for IFN-α2b quantification in human plasma

Aim: Nowadays, IFN-α is considered a promising therapeutic target for systemic lupus erythematosus. An immuno-PCR (iPCR) was developed to quantify low amounts of IFN-α in human plasma followed by a deep analysis of the methodologic robustness throughout quality by design approach. Results: An accurate, sensitive, selective and versatile iPCR was validated. The critical iPCR procedural steps were identified, applying a Plackett-Burman design. Also, this assay demonstrated an outstanding LOD of 0.3 pg/ml. A significant aspect relies on its high versatility to detect and quantify other cytokines in human plasma as the appropriate biotinylated antibody is employed. Conclusion: This reliable iPCR assay can be clinically used as an alternative method for quantitating and detecting low IFN-α2b concentrations in human plasma samples.Fil: Rodríguez, María Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Cultivos Celulares; ArgentinaFil: Attallah, Carolina Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Cultivos Celulares; ArgentinaFil: Lozano, Victoria. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Cultivos Celulares; ArgentinaFil: Etcheverrigaray, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Cultivos Celulares; ArgentinaFil: Oggero Eberhardt, Marcos Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Laboratorio de Cultivos Celulares; Argentin

Comparison of Fluorometric Detection Methods for Quantitative Polymerase Chain Reaction (PCR)

In this study, we compared the sensitivity of two different detection methods for quantitative polymerase chain reaction (PCR). Various amounts of a 75 mer single-stranded deoxyribonucleic acid (DNA) fragment, which can be used as a DNA label for the immuno-PCR (iPCR) assays, were amplified by PCR. The amount of amplified DNA fragments was determined by the fluorescence (FL) of SYBR(R) Green dye that specifically interacts with double-stranded DNA fragments. In the first selected detection method, real-time PCR, FL measurements were carried out at each thermal cycle, as the DNA was being amplified by PCR. This was achieved using the Applied Biosystems (ABI) Prism 7000 Sequence Detection System and its standard protocol. In the second detection method, referred to as end-point detection, after the PCR amplification was completed, off-line FL measurements were subsequently carried out using a conventional plate reader. In order to achieve the lowest limit of detection (LOD) from the off-line measurement, we have optimized a wide variety of parameters. Our data have indicated the LOD of real-time PCR method was approximately three orders of magnitude lower than the end-point measurement method, with a linear range spanning six orders of magnitude; 10 fmol to 10 zmol of PCR template. The lower LOD of the real-time PCR method could be partly due to the ability to maximize the number of thermal cycles that could be carried out in PCR, without increasing the nonspecific amplification of any contaminating DNA. The results of this study can be applied to the development of ultra-sensitive iPCR assays for various disease markers

Detection of insulin Receptor, Epidermal Growth Factor Receptor, and Interleukin-6 on Individual Mouse Embryos by Immuno-Polymerase Chain Reaction

Three series of experiments were conducted to: 1) optimize the conditions for the production of pUC19 plasmid and of biotinylated pUC19 fragments; 2) optimize the conditions for the production of protein A-streptavidin chimera (chimeric protein); and 3) detect soluble antigens [bovine serum albumin (BSA) and interleukin-6 (IL-6)] and membrane-bound antigens [insulin receptor and epidermal growth factor receptor (EGFr)] of mouse embryos by immuno-polymerase chain reaction (I-PCR). The first experimental series, which included bacterial culture, chimeric protein purification, and chimeric protein functional experiments, was performed to investigate the effects of IPTG (isopropyl-β-D-thiogalactopyranoside) induction time and temperature, bacterial culture medium, and protein purification procedure on chimeric protein yield. The yield of chimeric protein was affected by IPTG induction time, but not by induction temperature. The yield of chimeric protein from TB broth culture was five to ten times higher than from either M9 or LB medium culture. Eliminating a centrifugation step just before the biotin affinity chromatography increased the yield of chimeric protein three times more than when the centrifugation step was included. Data demonstrated that our chimeric protein was fully functional. The second series, including culturing and biotinylation experiments, was conducted to investigate the effects of culture conditions [Lennox L broth (LB broth) versus Terrific broth (TB broth) and 15 versus 28 hours] on pUC19 plasmid yield from pUC19 plasmid-transformed Escherichia coli (E. coli), and the effect of incubation conditions on the efficiency of pUC19 biotinylation. Culture medium but not culture time affected pUC19 plasmid yield. pUC19 biotinylation at 37°C for 30 min seemed to be superior compared to 15 min either on ice or at room temperature. Data demonstrated that biotinylated pUC19 fragments were hlly hnctional. The third series, including BSA, IL-6, insulin receptor, and EGFr assays, was performed using I-PCR and enzyme-linked immunosorbent assay (ELISA) assays to determine the absolute sensitivity of I-PCR technique and to compare the relative sensitivity between I-PCR and ELISA for detecting these antigens. The sensitivity limits of I-PCR were 5.8 BSA and 5.8 x l03 IL-6 molecules immobilized on the surface of a microtiter plate, which were six and seven orders of magnitude more sensitive than ELISA, respectively. By using I-PCR technique, we were able to detect insulin receptors on two mouse embryos and EGFr on only one mouse embryo at the morula stage. Data from these studies should be valuable for the future development of a non-invasive, I-PCR-based assay of individual embryo viability

Development of a real-time immuno-PCR assay for the quantification of environmental contaminants

This thesis outlines the development of two universal real-time immuno-PCR (RT-iPCR) assays for application in agriculture. The first RT-iPCR was developed for the sensitive quantification of 17β-estradiol in water. Using a universal iPCR method and polyclonal antibodies, 17β-estradiol was accurately quantified at concentrations ranging from 1 pg mL-1 to 10 μg mL-1, with a limit of detection of 0.7 pg mL-1. The RT-iPCR assay provided an 800-fold increase in sensitivity as well as an expanded working range compared to the corresponding enzyme-linked immunosorbent assay. Antibodies were swapped with antibodies specific to P. brassicae for the quantification of clubroot resting spores using the same RT-iPCR assay. P. brassicae resting spores were quantified in the range of 50 to 10 000 spores, with a detection limit of 29 spores. Both RT-iPCR showed equal or improved sensitivity compared to other published analytical methods, with expanded linear working ranges and high-throughput capabilities.Agriculture and Agri-Foods Canad

Detection of Ricin Contamination in Ground Beef by Electrochemiluminescence Immunosorbent Assay

Ricin is a highly toxic protein present in the seeds of Ricinus communis (castor), grown principally as a source of high quality industrial lubricant and as an ornamental. Because ricin has been used for intentional poisoning in the past and could be used to contaminate food, there is a need for analytical methodology to detect ricin in food matrices. A monoclonal antibody-based method was developed for detecting and quantifying ricin in ground beef, a complex, fatty matrix. The limit of detection was 0.5 ng/g for the electrochemiluminescence (ECL) method and 1.5 ng/g for enzyme-linked immunosorbent assay (ELISA). The detection of nanogram per gram quantities of ricin spiked into retail samples of ground beef provides approximately 10,000-fold greater sensitivity than required to detect a toxic dose of ricin (>1 mg) in a 100 g sample

Ultrasensitive Quantification of Crustacean Tropomyosin by Immuno-PCR

Tropomyosin is the major and predominant allergen among shellfish. This study developed an ultrasensitive immuno-PCR method for the quantification of crustacean tropomyosin in foods. The method couples sandwich ELISA with the real-time PCR (rtPCR) amplification of marker DNAs. Monoclonal anti-TPM antibody was the capture antibody, polyclonal rabbit anti-shrimp tropomyosin antibody was the detection antibody, while natural shrimp tropomyosin served as the standard. A double-stranded amino-DNA was covalently conjugated to a secondary anti-rabbit antibody and subsequently amplified and quantified via rtPCR. The quantification sensitivity of immuno-PCR was 20-fold higher than analogous ELISA, with LOQ 19.8 pg/mL. The developed immuno-PCR method is highly specific for the detection of crustacean tropomyosin and is highly precise in a broad concentration range. Tropomyosin recovery in the spiked vegetable soup was 87.7–115.6%. Crustacean tropomyosin was also quantified in commercial food products. The reported immuno- PCR assay is the most sensitive method for the quantification of crustacean tropomyosin and is the first immuno-PCR-based assay for the quantification of food allergen and food protein in general. The described method could be easily adapted for the specific and ultrasensitive immuno-PCR-based detection of traces of any food allergen that is currently being quantified with ELISA, which is of critical importance for people with food allergies

Immuno-pcr Detection Of Lyme Borreliosis

Lyme borreliosis, more commonly referred to as Lyme disease, is the fastest growing zoonotic disease in North America with approximately 30,000 confirmed cases and 300,000 estimated infections per year. In nature, the causative agent of Lyme disease, the bacterium Borrelia burgdorferi, cycles between Ixodes sp. ticks and small mammals. Humans become infected with Lyme disease after being bitten by an infected tick. The primary indicator of a Borrelia burgdorferi infection is a bull’s eye rash typically followed by flu-like symptoms with treatment consisting of a 2-4 week course of antibiotics. If not treated, later stages of the disease can result in arthritis, cardiovascular and neurological symptoms. Diagnosis of Lyme disease is challenging and currently requires a complex laboratory diagnostic using indirect detection of host-generated antibodies by a two-tiered approach consisting of an enzyme linked immunosorbent assay (ELISA) followed by IgM and IgG immunoblots. Although two-tier testing has provided an adequate approach for Lyme disease diagnosis, it has weaknesses including subjective analysis, complex protocols and lack of reagent standardization. Immuno-PCR (iPCR) is a method that combines ELISA-based detection specificity with the sensitivity of PCR signal amplification and has demonstrated increased sensitivity for many applications such as detection of disease biomarkers but has yet to be applied for diagnosis of Lyme disease. Herein, using iPCR and recombinant B. burgdorferi antigens, an assay for both the direct and the indirect detection of Lyme disease was developed iv and demonstrated improved sensitivity for detection of B. burgdorferi antibodies using a murine model. Moreover, we present evidence using human Lyme disease patient serum samples that iPCR using both multiple antigens and a unique single hybrid antigen is capable of achieving increased sensitivity and specificity compared to existing methodology. These data represent the first demonstration of iPCR for Lyme disease diagnosis and support the replacement of two-tier testing with a more simplified and objective approach

Ultrasensitive Quantification of Crustacean Tropomyosin by Immuno-PCR

Tropomyosin is the major and predominant allergen among shellfish. This study developed an ultrasensitive immuno-PCR method for the quantification of crustacean tropomyosin in foods. The method couples sandwich ELISA with the real-time PCR (rtPCR) amplification of marker DNAs. Monoclonal anti-TPM antibody was the capture antibody, polyclonal rabbit anti-shrimp tropomyosin antibody was the detection antibody, while natural shrimp tropomyosin served as the standard. A double-stranded amino-DNA was covalently conjugated to a secondary anti-rabbit antibody and subsequently amplified and quantified via rtPCR. The quantification sensitivity of immuno-PCR was 20-fold higher than analogous ELISA, with LOQ 19.8 pg/mL. The developed immuno-PCR method is highly specific for the detection of crustacean tropomyosin and is highly precise in a broad concentration range. Tropomyosin recovery in the spiked vegetable soup was 87.7–115.6%. Crustacean tropomyosin was also quantified in commercial food products. The reported immuno-PCR assay is the most sensitive method for the quantification of crustacean tropomyosin and is the first immuno-PCR-based assay for the quantification of food allergen and food protein in general. The described method could be easily adapted for the specific and ultrasensitive immuno-PCR-based detection of traces of any food allergen that is currently being quantified with ELISA, which is of critical importance for people with food allergies

Multiplex sorting of foodborne pathogens by on-chip free-flow magnetophoresis

This study reports multiplex sorting of Salmonella typhimurium and Escherichia coli 0157, from broth cultures and from pathogen-spiked skinned chicken breast enrichment broths by employing microfluidic free-flow magnetophoresis. Magnetic beads of different sizes and magnetite content, namely Dynabeads anti-salmonella and Hyglos-Streptavidin beads together with the corresponding pathogen-specific biotinylated recombinant phages, were utilised as affinity solid phases for the capture and concentration of viable S. typhimurium and E. coli 0157. Following optimisation, the protocol was used to demonstrate continuous magnetophoretic sorting of the two pathogen-bound magnetic bead populations from mixed cultures and from pathogen-spiked chicken pre-enrichment broths under the influence of a Halbach magnet array. For example, in the la tter case, a pure population of S. typhimurium-bound Dynabeads (72% recovery) was sorted from a 100 μL mixture containing E. coli 0157-bound Hyglos beads (67% recovery) within 1.2 min in the presence of 0.1% Tween 20. This proof-of-principle study demonstrates how more than one pathogen type can be simultaneously isolated/enriched from a single food pre-enrichment broth (e.g. Universal food enrichment broth)