Antibody Dilution Research Articles

Indirect enzyme-linked immunosorbent assay method based on Streptococcus agalactiae rSip-Pgk-FbsA fusion protein for detection of bovine mastitis.

The aim of this study was to establish a rapid and accurate method for the detection of the Streptococcus agalactiae antibody (SA-Ab) to determine the presence of the bovine mastitis (BM)-causative pathogen. The multi-subunit fusion protein rSip-Pgk-FbsA was prokaryotically expressed and purified. The triple activities of the membrane surface-associated proteins Sip, phosphoglycerate kinase (Pgk), and fibronectin (FbsA) were used as the diagnostic antigens to establish an indirect enzyme-linked immunosorbent assay (ELISA) method for the detection of SA-Ab in BM. The optimal antigen coating concentration was 2 μg/mL, the optimal serum dilution was 1:160, and the optimal dilution of the enzyme-labeled secondary antibody was 1:6000. The sensitivity, specificity, and repeatability tests showed that the method established in this study had no cross-reaction with antibodies to Streptococcus pyogenes, Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis in the sera. The results of the sensitivity test showed that a positive result could be obtained even if the serum dilution reached 1:12,800, indicating the high sensitivity and good repeatability of the method. The positive coincidence rate of this method was 98.6%, which is higher than that of previous tests established with the Sip or Pgk mono-antigen fusion protein, respectively, demonstrating the relatively higher sensitivity of this newly established method. The detection rate for 389 clinical samples was 46.53%. The indirect ELISA method established in this study could provide a more accurate and reliable serological method for the rapid detection of S. agalactiae in cases of BM.

Development of a Novel Anti-Adhesive Vaccine Against Pseudomonasaeruginosa Targeting the C-terminal Disulfide Loop of the Pilin Protein.

Type IV pili (T4P) are major virulence factors of Pseudomonas aeruginosa (P. aeruginosa) that are associated with primary adhesion, biofilm formation and twitching motility. This study focuses on the introduction of a novel biologically active subunit vaccine derived from the disulfide loop (DSL) of P. aeruginosa pilin. We investigated the expression of the novel PilA in-frame with pET26b vector, which contains three domains, that each domain contains three tandem repeats. The flexible (GGGGS) and (GGGGS)3 linkers were linked between the three tandem repeats and each pilA domain, respectively. The recombinant construct (pET26b/pilA) was transformed and expressed in Escherichia coli BL21 (DE3). The reactivity of specific antiserum against PilA was assessed by ELISA method. The biological activities of this candidate vaccine were evaluated by western blotting, opsonophagocytosis and twitching inhibition assays. The pET26b/pilA plasmid was confirmed by enzymatic digestion. The purified PilA protein was confirmed by immunoblot analysis. The checkerboard titration showed that the optimal dilution of the antibody to react with antigen was 1:8. The results of opsonophagocytosis assay revealed that the antibodies raised against PilA promoted phagocytosis of the PAO1 and 6266E strains to some extent (17.5% and 16.3%, respectively), so the twitching inhibition test confirmed this result. Taken together, these are the preliminary results based on a first chimerical structure failure to induce antibodies that promote the opsonization and eradication of the pathogen. Therefore, the biological activity of the PilA protein showed that it should be introduced with other proteins or target antigens against P. aeruginosa in the future studies.

Immunohistochemical Expression of Human Epididymis 4 (He4) in Ovarian Serous Carcinoma in Hospital Serdang from the Year 2006- 2013

Ovarian cancer is the fifth most common cause of cancer death in women worldwide and is the fourth leading cause of cancer related deaths in Malaysia. Ovarian cancer are classified based on histological types, because it is an important surrogate for genetic, prognostic, and predictive information about response to treatment. The malignant epithelial tumor, that is ovarian carcinoma (OC) is the most common group and the four most common subtypes of OC are serous, endometrioid, clear cell and mucinous. Among the OC, ovarian serous carcinoma (OSC) is the most common subtypes. Most of the women with OC presented with locally advanced disease or distant metastasized at the time of diagnosis. The two-tier grading system (also known as MDACC [M.D Anderson Cancer Center] grading system) has been accepted worldwide. Human epididymis 4 (HE4) is a new protein which is frequently overexpressed in ovarian neoplastic tissue. Previous studies have shown that there is significant difference of HE4 expression in low grade serous carcinoma (LGSC) and high grade serous carcinoma (HGSC). The aim of this study is to further evaluate the HE4 tissue expression in 2 different grades of OSC in Hospital Serdang. This is a retrospective, cross-sectional study, of 71 cases histopathologically diagnosed as OSC comprising of 48 cases of HGSC and 23 cases of LGSC. Cases were collected from Hospital Serdang, from 1st January 2006 to 31st December 2013. All cases were examined for HE4 expression by immunohistochemistry using anti-HE4 (Polyclonal rabbit antibody dilution 1:40, Abcam).

Simultaneous Monitoring of Drug Responses on Distinct Hematopoietic Cell Populations Allow Assessment of Direct and Indirect Cytotoxic Effects of Targeted Therapies

IntroductionOff-target cytotoxicity resulting in severe side effects and compromising patient survival often hampers the development of new cancer therapeutics. Understanding the complete drug response landscape of different cell populations is crucial to identify drugs that selectively eradicate the malignant cell population, but spare healthy cells. Here, we developed a high content, no wash, multi-parametric flow cytometry based assay that enables testing of blood cancer patient samples and simultaneously monitors the effects of several drugs on 11 hematopoietic cell types. The assay can be used to i) dissect malignant from healthy cell responses and predict off-target effects; ii) assess drug effects on immune cell subsets; iii) identify drugs that can potentially be repositioned to new blood cancer indications.MethodsMononuclear cells were prepared from bone marrow aspirates of 7 multiple myeloma (MM) and 3 acute myeloid leukemia (AML) patients plus the peripheral blood from a healthy donor, which were collected following informed consent and in compliance with the Declaration of Helsinki. Optimal cell density, antibody dilutions, incubation time, and wash versus no wash assay conditions for the selected antibody panels were determined. Cells were incubated at a density of 2 million cells/ml in either 96- or 384-well plates for 3 days. The antibodies were tested in two panels to study the effects of 6 drugs in 5 dilutions (1-10000 nM) (clofarabine, bortezomib, dexamethasone, navitoclax, venetoclax and omipalisib) on 11 cell populations, namely hematopoietic stem cells (HSCs) (CD34+CD38-), common progenitor cells (CPCs) (CD34+CD38+), monocytes (CD14+), B cells (CD45+CD19+), cytotoxic T cells (CD45+CD3+CD8+), T helper cells (CD45+CD3+CD4+), NK-T cells (CD45+CD3+CD56+), NK cells (CD45+CD56+CD3-), clonal plasma cells (CD138+CD38+), other plasma cells (CD138+CD38-) and granulocytes (CD45+, SSC++). Annexin-V and 7AAD were used to distinguish live cell populations from apoptotic and dead cells. After 1 h incubation with antibodies, the plates were read with the iQue Screener PLUS instrument (Intellicyt). Counts for each population were used to generate four parameter nonlinear regression fitted dose response curves with GraphPad Prism 7. Three samples were tested in duplicate to assess reproducibility.ResultsTo decrease the complexity of the assay, we tested all antibodies under wash and no wash conditions, and found that results from both conditions were comparable. To minimize the amount of sample needed as well as maximize the number of drugs tested and cell populations that can be detected, we set up the assay in both 96- and 384-well plates. The assay was highly reproducible when samples were tested in replicate and was scalable to a 384-well format without compromising sensitivity to detect rare populations such as plasma cells. Due to the differentiation of immature cells to specialized cell types, the drug responses of specific populations tended to drift. HSCs (CD34+CD38-) were shown to be refractory to the tested drugs compared to CPCs characterized as (CD34+CD38+) and other cell types. Interestingly, the proteasome inhibitor bortezomib was cytotoxic to all cell populations except for CD138+CD38- plasma cells. Clofarabine, a nucleoside analog used to treat ALL, effectively targeted CPC, NK and B cells, while HSCs and plasma cells were resistant. The glucocorticoid and immunosuppressive drug dexamethasone specifically targeted B and NK cells compared to T cell populations (CD8+, CD4+), while NK-T cells were modestly sensitive. The cell population response patterns were similar in samples derived from MM, AML and healthy individuals, highlighting that the drug responses are highly cell type specific.SummaryUsing a high content, multi-parametric assay, we could rapidly assess the effect of several drugs on specific cell populations in individual patient samples. Our results demonstrate that many drugs preferentially affect different hematological cell lineages. Although heterogeneity was observed between individual patients, the pattern of cytotoxic response exhibited by specific cell types was consistent among samples derived from MM, AML and healthy donors. The assay will be useful to identify drugs with maximal on-target and minimal off-target specificity, and can potentially be used to guide treatment decision and predict patient response DisclosuresHeckman:Celgene: Research Funding; Pfizer: Research Funding.

Development of a novel rapid micro-neutralization ELISA for the detection of neutralizing antibodies against Chandipura virus

BackgroundChandipura virus (CHPV) is a leading cause of acute encephalitis with high mortality in paediatric population in India. A micro-neutralization ELISA (MN-ELISA) assay was developed for the detection of neutralizing antibodies (Nab) against CHPV. This novel method gives read-out in the form of ELISA optical density (OD) values and has a shorter turn-around time (TAT) as compared to the conventional cytopathic effect (CPE)-based neutralization assay (MN-CPE). The assay was developed using an Indian strain of CHPV. During the development of the assay different parameters such as cell count, dilution of primary and secondary antibodies and time point for the test termination were optimized. The new and conventional assays were run in parallel where known positive and negative human serum samples were used as test controls. The conventional MN-CPE was terminated at 48h post-infection (p.i.) and stained with Amido black, while in the new assay, MN-ELISA was terminated at pre-determined 18h p.i. and the infected cells were fixed with acetone, followed by in-situ ELISA. Results of both the assays were compared.The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the new test was 100% when compared with the conventional MN-CPE method as a ‘gold standard’. The MN-ELISA showed two-fold higher antibody titer in one sample and one sample was additionally positive than MN-CPE ELISA. ConclusionThe MN-ELISA is rapid, more sensitive and read-out of results is by measurement of OD, which could be more accurate than manual observation of reduction in CPE. This novel test could be used as an alternative to the conventional MN-CPE based assay in sero-surveillance and in future vaccine studies.

Development of an immunoFET biosensor for the detection of biotinylated PCR product.

ImmunoFET (IMFET) biosensor is a simple platform for the detection of biotinylated products of polymerase chain reaction (PCR). Construction of the IMFET biosensor started with adsorption of 1.5 mg/mL of protein A (PA) onto the insulated gate surface of ISFET for 90 min. Next, the immobilized 1/500 dilution of anti-biotin antibody was adsorbed onto the PA layer for 60 min. The IMFET biosensor was subsequently ready for detection of the biotinylated amplicon. The IMFET biosensor showed highly specific binding to the biotinylated PCR product of the phaE gene of Haloquadratum walsbyi DSM 16854. The phaE gene is a biomarker of polyhydroxyalkanoate (PHA) producers that contain PHA synthase class III. The lowest amount of DNA template of H. walsbyi DSM 16854 that the IMFET biosensor could detect was 125 fg. The IMFET biosensor has a lower amount of detection compared with a DNA lateral flow biosensor from our previous study. The degree of linearity of the biosensor signal was influenced by the concentration of the biotinylated amplicon. The IMFET biosensor also has a short response time (approximately 30 times) to detect the phaE amplicon compared to an agarose gel electrophoresis. The IMFET biosensor is a promising tool for the detection of the biotinylated PCR product, and it can be integrated into a micro total analysis system (μTAS).

Development and optimization of a double antibody sandwich ELISA for the detection of goose T cell surface CD8α molecule

CD8, a glycoprotein on the surface of T cells, is involved in the defense against viral infection and plays significant roles in antigen presentation and in the antiviral immune response. CD8 is composed of two chains. Of these, the CD8α chain was chosen for the detection because it involved in both the CD8αα homodimer and the CD8αβ heterodimer. Here, we established a double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) for specific detection of goose CD8α (goCD8α). The results showed that the optimal coated antibody and antigen dilutions were 1:50 (the antibody titer was 1:12 800) and 1:32 (0.3 ng mL−1), respectively, while the optimal capture antibody and horseradish peroxidase (HRP)-labelled goat anti-rabbit IgG dilutions were 1:50 (the antibody titer was 1:51 200) and 1:4 000 (the antibody titer was 1:5 000), respectively. The optimal blocking buffer was 5% bovine serum albumin (BSA). The best incubating condition was overnight at 4°C, the best blocking time was 120 min and the best anti-capture antibody working time was 150 min. In addition, the minimum dose detectable by DAS-ELISA was 5×10−3 ng mL−1. Most importantly, goCD8α expression levels in goose spleen mononuclear cells (MNCs) post-Goose parvoviruse (GPV) infection were found to be significantly up-regulated using the DAS-ELISA method, which was consistent with previous results obtained using real-time quantitative PCR. In conclusion, the DAS-ELISA method reported here is a novel, specific technique for the clinical detection of goCD8α.

Databases for technical aspects of immunohistochemistry.

With the aims of sharing information about the technical aspects of immunohistochemistry (IHC) and making it possible to make a suitable choice of antibody for histopathological examination, this technical report describes the results of a questionnaire administered during the period of 2014 to 2015 to members of the Conference on Experimental Animal Histopathology. It also describes the immunological properties of primary antibodies (clone, supplier, catalog number, species reactivity, etc.) and the IHC staining conditions (fixing solution, fixing time, embedding, antigen retrieval method, antibody dilution, incubation time, incubation temperature, positive control tissue, secondary antibody information, etc.) for a total number of 733 primary antibodies (425 kinds of primary antibody).

Determination of male-specific gene expression of White Lamphun cattle semen treated by monoclonal antibodies

In the present study, male-specific monoclonal antibodies, P1C2B8 and P1C2C9, were used for sperm sexing via agglutination and cytotoxic reactions in White Lamphun cattle semen no. 862, no. 863 and no. KL. Live sperm percentage was used to find out an optimum dilution of antibody in agglutination and cytotoxic reactions and multiplex real time polymerase chain reaction was used to determine male-specific gene expression in each optimum dilution. In agglutination treatment, the results showed that all cattle had the same optimum antibody dilution while in cytotoxicity treatment, each cattle had different optimum antibody dilution. The results from multiplex real time polymerase chain reaction also showed that in both agglutination and cytotoxicity treatments, male- specific gene expression in semen samples was lower in cattle no. 862, no. 863 and no. KL when compared to control treatment. From these results, it was implied that antibodies P1C2B8 and P1C2C9 could alter the sperm sex ratio by reducing Y sperm in White Lamphun cattle semen.

Development of a Homologous Fluorescence Polarization Immunoassay for Diisobutyl Phthalate in Romaine Lettuce

In this work, three fluorescein-labeled DiBP derivatives (tracers) with different chemical structures and spacer bridges were synthesized and purified by thin-layer chromatography (TLC). Compared with the heterologous tracer, the homologous tracer exhibited more affinity to the antibody. What is more, the tracer concentration and the antibody dilution were further evaluated to improve the sensitivity of fluorescence polarization immunoassay (FPIA). On the basis of sensitive antibody and tracer, a rapid and specific FPIA has been established for the detection of DiBP contamination in the romaine lettuce, which has rarely been reported before. Under the optimal conditions, the developed FPIA showed a good detection range from 8.82 to 2152.84 ng/mL, with a detection limit of 1.77 ng/mL. In addition, the cross-reactivity to several compounds structurally related to DiBP was less than 7.37 %. Therefore, DiBP contamination in spiked romaine lettuce samples was detected by FPIA, with the recovery from 88.28 to 119.11 %. Moreover, when compared with high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA), the results analyzed by the developed FPIA shows a strong reliability and a high correlation value of 0.978 and 0.980, respectively. Thus, this data, combined with rapidity and simplicity of the assay, demonstrates that the established FPIA is a suitable method for high throughput screening of DiBP contamination in the romaine lettuce.

Repeated immunostaining of the same tissue section using alkaline phosphatase as a reporter

One can determine the best dilution of a primary antibody for immunohistochemistry that uses horseradish peroxidase conjugated to a secondary antibody by testing increasing concentrations sequentially on the same tissue section. When the same tissue section is incubated repeatedly with increasing concentrations of primary antibodies to epithelial membrane antigen, smooth muscle α-actin, or vimentin using alkaline phosphatase conjugated to a secondary antibody as the reporter, the best staining was obtained with a less concentrated primary antibody than was optimal for a single staining test. The best concentration of primary antibody for single run staining using an alkaline phosphatase reporting system is usually four times the best concentration for staining with multiple runs. The optimal concentration can be determined by denaturing the residual alkaline phosphatase and extracting residual stain by incubating the section in 4:1 diglyme:phosphate buffered saline for 20 min at 80o C between tests of primary antibody concentrations. I tested the method for four chromogens from one supplier and one chromogen from a different supplier.

Adjunctive use of interferon γ inducer for treatment of patients with schizophrenia

The present paper is devoted to evaluation of clinical and immunomodulatory effect of ultra-high dilutions of antibodies to human interferon γ, included in the complex therapy of patients with schizophrenia. Materials and methods The study was carried out at the Mental Health Research Institute, Tomsk, Russian Federation. This double-blind, placebo-controlled randomised in parallel-group study enrolled 40 patients. As a part of complex therapy, patients from the main group (n=20) received anaferon, a drug containing ultra-high dilutions of affinity-purified antibodies to human interferon γ as the active pharmaceutical ingredient; patients from the comparative group (n=20) received placebo. Duration of the therapy was 30±5 days. Assessment of severity of symptoms and changes in them were made using clinical scales: Positive and Negative Syndrome Scale, Clinical Global Impression, Abnormal Involuntary Movements Scale. Spontaneous and phytohemagglutinin-induced production of interferon γ by immunocompetent cells in supernatants of 48 h whole blood culture of patients was measured by enzyme-linked immunosorbent assay (ELISA) method. The reduction of interferon-producing potential by immunocompetent cells in comparison with reference normal value was shown in total group of patients (n=40) before combined therapy. During the treatment, increase of spontaneous interferon γ production and favourable changes in psychopathological symptoms as compared with placebo were shown in subjects receiving anaferon. It was found that favourable changes in clinical symptoms assessed using clinical scales with a high degree of confidence correlated with high level of spontaneous interferon γ production. Anaferon as a part of complex therapy of patients with schizophrenia contributes to enhancement of its efficacy acting via mechanism of psychoimmunomodulation.

Target antigens for Hs-14 monoclonal antibody and their various expression in normozoospermic and asthenozoospermic men.

BackgroundPoor semen quality is one of the main causes of infertility. We have generated a set of monoclonal antibodies to human sperm and used them to investigate sperm quality. Some of these antibodies found differences in the expression of proteins between normal sperm and pathological sperm displaying severe defects. One of them was the Hs-14 antibody.The aim of this paper was to determine the target protein of the Hs-14 monoclonal antibody and to investigate the expression of the Hs-14-reacting protein on the sperm of asthenozoospermic men with sperm motility defect and of healthy normozoospermic men.MethodsIndirect immunofluorescence, one-dimensional and two-dimensional polyacrylamide gel electrophoresis, immunoblotting and mass spectrometry.ResultsThe Hs-14 antibody binds fibronectin, β-tubulin and valosin-containing protein - new name for this protein is transitional endoplasmic reticulum ATPase (TERA). Since the Hs-14 reaction with TERA remained the strongest at the highest antibody dilution, and Hs-14 consistently labelled the same spot or band as the monospecific anti-TERA antibody on immunoblots, we assume that TERA is an Hs-14-specific protein. Binding of fibronectin and β-tubulin might represent nonspecific cross-reactivity or Hs-14 reaction with similar epitopes of these proteins.A significant difference (P < 0.001) in immunofluorescence staining with Hs-14 was found between the normozoospermic and asthenozoospermic men.ConclusionThe Hs-14 antibody enables discrimination between sterile or subfertile asthenozoospermic and fertile normozoospermic men. Decreased levels of TERA in men can be used as a biomarker of reduced fertility.Electronic supplementary materialThe online version of this article (doi:10.1186/s12610-015-0025-0) contains supplementary material, which is available to authorized users.

A single simple procedure for dewaxing, hydration and heat-induced epitope retrieval (HIER) for immunohistochemistry in formalin fixed paraffin-embedded tissue.

Heat-induced epitope retrieval (HIER) is widely used for immunohistochemistry on formalin-fixed paraffin-embedded tissue and includes temperatures well above the melting point of paraffin. We therefore tested whether traditional xylene-based removal of paraffin is required on sections from paraffin-embedded tissue, when HIER is performed by vigorous boiling in 10 mM Tris/0.5 mM EGTA-buffer (pH=9). Immunohistochemical results using HIER with or without prior dewaxing in xylene were evaluated using 7 primary antibodies targeting proteins located in the cytosol, intracellular vesicles and plasma membrane. No effect of omitting prior dewaxing was observed on staining pattern. Semiquantitative analysis did not show HIER to influence the intensity of labelling consistently. Consequently, quantification of immune labelling intensity using fluorescent secondary antibodies was performed at 5 dilutions of primary antibody with and without prior dewaxing in xylene. No effect of omitting prior dewaxing on signal intensity was detectable indicating similar immunoreactivity in dewaxed and non-dewaxed sections. The intensity of staining the nucleus with the DNA-stain ToPro3 was similarly unaffected by omission of dewaxing in xylene.In conclusion, the HIER procedure described and tested can be used as a single procedure enabling dewaxing, hydration and epitope retrieval for immunohistochemistry in formalin-fixed paraffin-embedded tissue.

NMDA receptors are expressed in human ovarian cancer tissues and human ovarian cancer cell lines.

We have earlier demonstrated that breast cancer and small-cell lung cancer express functional NMDA receptors that can be targeted to promote cancer cell death. Human ovarian cancer tissues and human ovarian cancer cell lines (SKOV3, A2008, and A2780) have now been shown to also express NMDA-receptor subunit 1 (GluN1) and subunit 2B (GluN2B). Seventeen ovarian cancers in two arrays were screened by immunohistochemistry using polyclonal antibodies that recognize an extracellular moiety on GluN1 and on GluN2B. These specimens comprised malignant tissue with pathology diagnoses of serous papillary cystadenocarcinoma, endometrioid adenocarcinoma, and clear-cell carcinoma. Additionally, archival tissues defined as ovarian adenocarcinoma from ten patients treated at this institute were also evaluated. All of the cancerous tissues demonstrated positive staining patterns with the NMDA-receptor antibodies, while no staining was found for tumor-adjacent normal tissues or sections of normal ovarian tissue. Human ovarian adenocarcinoma cell lines (A2008, A2780, SKOV3) were demonstrated to express GluN1 by Western blotting, but displayed different levels of expression. Through immunocytochemistry utilizing GluN1 antibodies and imaging using a confocal microscope, we were able to demonstrate that GluN1 protein is expressed on the surface of these cells. In addition to these findings, GluN2B protein was demonstrated to be expressed using polyclonal antibodies against this protein. Treatment of all ovarian cell lines with antibodies against GluN1 was found to result in decreased cell viability (P<0.001), with decreases to 10%–25% that of untreated cells. Treatment of control HEK293 cells with various dilutions of GluN1 antibodies had no effect on cell viability. The GluN1 antagonist MK-801 (dizocilpine maleate) and the GluN2B antagonist ifenprodil, like antibodies, dramatically decreased the viability of A2780 ovarian tumor cells (P<0.01). Treatment of A2780 tumor xenografts with ifenprodil (2.5 mg/kg body weight/day) significantly reduced tumor growth in nu/nu mice. Our findings suggest that both GluN1 and GluN2B proteins as membrane components could be readily available targets for the treatment of most ovarian cancers.

Development of an indirect ELISA method based on the VP3 protein of duck hepatitis A virus type 1 (DHAV-1) for dual detection of DHAV-1 and DHAV-3 antibodies

An indirect enzyme-linked immunosorbent assay (I-ELISA) based on the recombinant VP3 protein of duck hepatitis A virus type 1 (DHAV-1) was developed and evaluated in this study. The optimal antigen, serum and enzyme-labeled antibody dilutions were 1:160 (0.94μg), 1:160 and 1:2000, respectively. The optimal blocking buffer was 1% gelatin. The cutoff value was determined to be 0.332, and the analytical sensitivity was 1:1280 (OD450–630=0.37). The results of the specificity evaluation showed that no cross-reactivity existed between DHAV-1 antiserum and other common duck-sensitive pathogens, except for duck hepatitis A virus type 3 (DHAV-3), suggesting that this could be a common approach for the simultaneous detection of DHAV-1 and DHAV-3 antibodies. The coefficients of variation (CVs) for all of the tested samples were lower than 10%. The concordance between the I-ELISA based on the VP3 subunit of DHAV-1 and that based on the whole DHAV-1 particle was 96%. These results indicate that the VP3-based I-ELISA method has high sensitivity, specificity, and repeatability and is as effective as the DHAV-1-based I-ELISA method for sero-surveillance. Thus, it may be a convenient and novel method for DHAV antibody detection and epidemiological surveillance of DHAV prevalence.

Proficiency testing in immunohistochemistry—experiences from Nordic Immunohistochemical Quality Control (NordiQC)

Despite extensive use of immunohistochemistry (IHC) for decades, lack of standardization remains a major problem, even aggravated in the era of targeted therapy. Nordic Immunohistochemical Quality Control (NordiQC) is an international academic proficiency testing (PT) program established in 2003 primarily aimed at assessing the analytical phases of the laboratory IHC quality. About 700 laboratories from 80 countries are currently participating. More than 30,000 IHC slides have been evaluated during 2003–2015. Overall, about 20 % of the staining results in the breast cancer IHC module and about 30 % in the general module have been assessed as insufficient for diagnostic use. The most common causes for insufficient results are less successful antibodies (poor and less robust antibodies, poorly calibrated ready-to-use (RTU) products, and stainer platform-dependent antibodies; 17 %), insufficiently calibrated antibody dilutions (20 %), insufficient or erroneous epitope retrieval (27 %), less sensitive visualization systems (19 %), and other (heat- and proteolysis-induced impaired morphology, endogenous biotin reaction, drying out phenomena, stainer platform-dependant protocol issues; 17 %). Approximately, 90 % of the insufficient results are characterized by either a too weak or false negative staining, whereas in the remaining 10 %, a poor signal-to-noise ratio or false positive staining is seen. Individually tailored recommendations for protocol optimization and identification of best tissue controls to ensure appropriate calibration of the IHC assay have for many markers improved IHC staining as well as inter-laboratory consistency of the IHC results. RTUs will not always provide an optimal result and data sheets frequently misguide the laboratories hampering the improvement in IHC quality. The overall data generated by NordiQC during 12 years indicates that continuous PT is valuable and necessary. Detailed description of the results of the NordiQC programme is available on www.nordiqc.org and summarized in this paper.

Development of a multi-epitope antigen of S protein-based ELISA for antibodies detection against infectious bronchitis virus.

An indirect enzyme-linked immunosorbent assay (ELISA) method based on a novel multi-epitope antigen of S protein (SE) was developed for antibodies detection against infectious bronchitis virus (IBV). The multi-epitope antigen SE protein was designed by arranging three S gene fragments (166-247 aa, S1 gene; 501-515 aa, S1 gene; 8-30 aa, S2 gene) in tandem. It was identified to be approximately 32 kDa as a His-tagged fusion protein and can bind IBV positive serum by western blot analysis. The conditions of the SE-ELISA method were optimized. The optimal concentration of the coating antigen SE was 3.689 μg/mL and the dilution of the primary antibodies was identified as 1:1000 using a checkerboard titration. The cut-off OD450 value was established at 0.332. The relative sensitivity and specificity between the SE-ELISA and IDEXX ELISA kit were 92.38 and 89.83%, respectively, with an accuracy of 91.46%. This assay is sensitive and specific for detection of antibodies against IBV.

Abstract 3209: The expression of SLC7A11 transporter in lung and pancreatic cancer tissues at different stages of development

Abstract Purpose: The purpose is to investigate the expression of the SLC7A11 transporter in human biopsy samples from patients with lung or pancreatic cancer at different stages of development. The SLC7A11 is a membrane antiporter highly specific for cystine. It is a major transporter for the uptake of cystine in exchange of intracellular glutamate. It plays a role in the growth and progression of cancers because they need extracellular cystine for growth. The expression of SLC7A11 was compared between normal and malignant tissues. Methods: Lung and pancreatic tissue array slides were purchased from US Biomax, Inc. Pancreatic samples were categorized into adenocarcinoma, normal and adjacent to cancer tissues. Lung cancer samples were categorized into: adenocarcinoma or squamous cell carcinoma, and normal tissue. The slides were hydrated with a series of washes using xylene and graded alcohols. The tissue arrays underwent blocking of endogenous peroxidase and albumin. The tissue arrays were processed with a primary antibody (1:500) dilution of a rabbit polyclonal antibody against SLC7A11, and a secondary antibody (1:3000) dilution of goat anti-rabbit conjugated to horseradish peroxidase (HRP). The slides were counterstained with hematoxylin and images were taken with the EVOS® FL Cell Imaging System. The software ImageJ was used to determine proportion of stained cells. The staining intensity was determined by comparing the samples to their negative control supplied on the tissue arrays. The immune-reactive score (IRS) was calculated as SI x PP and it ranged from 0 to 12. An IRS within 0-3 indicated no, or low expression, 4-7 medium expression and 8-12 high expression. The distribution of the IRS score frequency in the different stages was compared to that of the normal tissues and compared using the chi square test for trend. Results: The SLC7A11 is significantly overexpressed on all cancer tissues compared to normal tissues or adjacent to cancer tissues. Pancreatic and lung adenocarcinomas as well as lung squamous cells carcinomas have significantly different distributions of IRS score staining for SLC7A11 compared to normal tissues. However, there is no significant difference between the different cancer stages and the distributions of the IRS staining for SLC7A11. Conclusion: The results indicate that expression of the SLC7A11 transporter is significantly overexpressed in cancer compared to the normal tissues, but there is no significant difference between the expression levels of SLC7A11 at different stages of lung or pancreatic cancer. Citation Format: Jonathan A. Moreno, Maria P. Lambros. The expression of SLC7A11 transporter in lung and pancreatic cancer tissues at different stages of development. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3209. doi:10.1158/1538-7445.AM2015-3209

Determination of Furaltadone Metabolite in Fish by Chemiluminescence Enzyme Immunoassay

Abstract An indirect competitive chemiluminescence enzyme immunoassay (icCLEIA) detection for the furaltadone metabolite 5-morpholinomethyl-3-amino-2-oxazolidone (AMOZ) was established. The effects of the coating antigen concentration, antibody dilution, immunoreaction time, reaction buffer and its ion concentration on the performance of the assay were studied and optimized. The results showed that the optimized assay conditions were as follows: the coating antigen concentration was 10 ng mL−1, the polyclonal antibody was diluted 60000 times, immunoreaction time was 50 min and the buffer solution was 0.01 M phosphate buffer solution (PBS, pH 7.4). Under the optimized conditions, the linear detection range of the developed icCLEIA was 0.026–3.52 μg L−1, the half inhibitory concentration (IC50) was 0.29 μg L−1 and the limit of detection (IC10) was 0.012 μg L−1. The average recoveries of AMOZ of spiked fish ranged from 101.0% to 115.5%. In conclusion, the icCLEIA is applicable for detection of trace AMOZ in fish samples.