Combining culture and microbead-based immunoassay for the early and generic detection of bacteria in platelet concentrates.

BACKGROUND: Despite current preventive strategies, bacterial contamination of platelets is the highest residual infectious risk in transfusion. Bacteria can grow from an initial concentration of 0.03-0.3 colony-forming units (CFUs)/mL up to 108 to 109 CFUs/mL over the product shelf life. The aim of this study was to develop a cost-effective approach for an early, rapid, sensitive, and generic detection of bacteria in platelet concentrates. STUDY DESIGN AND METHODS: A large panel of bacteria involved in transfusion reactions, including clinical isolates and reference strains, was established. Sampling was performed 24 hours after platelet spiking. After an optimized culture step for increasing bacterial growth, a microbead-based immunoassay allowed the generic detection of bacteria. Antibody production and immunoassay development took place exclusively with bacteria spiked in fresh platelet concentrates to improve the specificity of the test. RESULTS: Antibodies for the generic detection of either gram-negative or gram-positive bacteria were selected for the microbead-based immunoassay. Our approach, combining the improved culture step with the immunoassay, allowed sensitive detection of 1 to 10 CFUs/mL for gram-negative and 1 to 102 CFUs/mL for gram-positive species. CONCLUSION: In this study, a new approach combining bacterial culture with immunoassay was developed for the generic and sensitive detection of bacteria in platelet concentrates. This efficient and easily automatable approach allows tested platelets to be used on Day 2 after collection and could represent an alternative strategy for reducing the risk of transfusion-transmitted bacterial infections. This strategy could be adapted for the detection of bacteria in other cellular products.

Highly labeled methylene blue-ds DNA silica nanoparticles for signal enhancement of immunoassays: application to the sensitive detection of bacteria in human platelet concentrates.

A nanoparticle-based electrochemical sandwich immunoassay was developed for bacteria detection in platelet concentrates. For the assay, magnetic beads were functionalized with antibodies to allow the specific capture of bacteria from the complex matrix, and innovative methylene blue-DNA/nanoparticle assemblies provided the electrochemical response for amplified detection. This nanoparticular system was designed as a temperature-sensitive nano-tool for electrochemical detection. First, oligonucleotide-functionalized nanoparticles were obtained by direct synthesis of the DNA strands on the nanoparticle surface using an automated oligonucleotide synthesizer. Densely packed DNA coverage was thus obtained. Then, DNA duplexes were constructed on the NP surface with a complementary strand bearing a 3 methylene blue tag. This strategy ultimately produced highly functionalized nanoparticles with electrochemical markers. These assemblies enabled amplification of the electrochemical signal, resulting in a very good sensitivity. A proof-of-concept was carried out for E. coli detection in human platelet concentrates. Bacterial contamination of this complex biological matrix is the highest residual infectious risk in blood transfusion. The development of a rapid assay that could reach 10-102 CFU mL-1 sensitivity is a great challenge. The nanoparticle-based electrochemical sandwich immunoassay carried out on a boron doped diamond electrode proved to be sensitive for E. coli detection in human platelets. Two antibody pairs were used to develop either a generic assay against certain Gram negative strains or a specific assay for E. coli. The methylene blue-DNA/nanoparticles amplify sensitivity ×1000 compared with the assay run without NPs for electrochemical detection. A limit of detection of 10 CFU mL-1 in a biological matrix was achieved for E. coli using the highly specific antibody pair.

Circulating osteoglycin and NGAL/MMP9 complex concentrations predict 1-year major adverse cardiovascular events after coronary angiography.

OBJECTIVE: Previous proteomics experiments have demonstrated that several proteins are differentially expressed in vulnerable human carotid plaques compared with stable plaques. This study aims to investigate the prognostic value of 13 such circulating biomarkers in patients with coronary artery disease. APPROACH AND RESULTS: Between 2008 and 2011, 768 patients who underwent coronary angiography for acute coronary syndrome or stable angina pectoris were included in a prospective biomarker study. Plasma concentrations of 13 biomarkers were measured in 88 patients who experienced a major adverse cardiovascular event (MACE) within 1 year and 176 control patients without MACE who were matched on age, sex, and number of diseased coronary vessels. MACE comprised all-cause mortality, acute coronary syndrome, unplanned coronary revascularization, and stroke. After adjustment for established cardiovascular risk factors, osteoglycin (OGN; odds ratio per SD increase in ln-transformed OGN, 1.53; 95% confidence interval, 1.11-2.11; P=0.010) and neutrophil gelatinase-associated lipocalin/matrix metalloproteinase 9 (NGAL/MMP9; odds ratio per SD increase in ln-transformed NGAL/MMP9, 1.37; 95% confidence interval, 1.01-1.85; P=0.042) complex were independently associated with MACE during follow-up. These associations were independent of C-reactive protein levels. Adding OGN or NGAL/MMP9 to a model containing conventional risk factors did not significantly improve discriminatory power (OGN: area under receiver operating characteristic curve, 0.75 versus 0.67; NGAL/MMP9: 0.73 versus 0.67) but did significantly improve risk reclassification (OGN: net reclassification index=0.29; 95% confidence interval, 0.05-0.53; P<0.019; NGAL/MMP9: net reclassification index=0.44; 95% confidence interval, 0.20-0.69; P<0.001). CONCLUSIONS: Circulating OGN and NGAL/MMP9 complex are promising biomarkers that are expressed in vulnerable atherosclerotic plaques and may have incremental value for prediction of MACE within 1 year after coronary angiography.

Carotid atherosclerotic plaques: proteomics study after a low-abundance protein enrichment step.

Atherosclerosis is one of the most important causes of cardiovascular and cerebrovascular events. Although phenotypic differentiation between stable and unstable plaques is currently possible, proteomic analysis of the atherosclerotic plaque could offer a global view of the atherosclerosis pathology. With the objective to highlight the detection of low-abundance proteins, we reduced the dynamic range of proteins by combinatorial peptide ligand library treatment of human carotid artery atherosclerotic plaques. After enrichment step, abundance of major proteins was decreased, revealing different protein profiles as assessed by both SDS-polyacrylamide gel electrophoresis and two-dimensional electrophoresis comparative analyses. Identification of proteins that were contained in a spot allowed finding large differences between noncomplicated and complicated plaques from carotid atherosclerotic lesions. Novel low-abundance proteins were detected correlating very well with biological alterations related to atherosclerosis (heat shock protein 27 (HSP27) isoforms, aldehyde dehydrogenase, moesin, Protein kinase C delta-binding protein, and inter-α trypsin inhibitor family heavy chain-related protein (ITIH4)). At the same time, the differential expression of known proteins of interest such as hemoglobin ß-chain and heat shock protein 27 between noncomplicated and hemorrhagic complicated plaques was maintained after enrichment step. The detection of different isoforms of a low-abundance protein such as heat shock protein 27 species was actually improved after enrichment of tissue protein extracts. All of these findings clearly support further investigations in view to confirm the role of these proteins as possible biomarkers.

Combined measurement of PEDF, haptoglobin and tau in cerebrospinal fluid improves the diagnostic discrimination between alzheimer's disease and other dementias.

Using proteomic approach in cerebrospinal fluid (CSF) we identified pigment epithelium-derived factor (PEDF) and Haptoglobin (Hp) as putative markers that could discriminate between AD and other dementias. ELISA assays were developed to measure the levels of PEDF and Hp in CSF from patients with AD (AD, n=27), non-AD (NAD, n=30) and in non-demented patients (ND, n=27). The combined assessment of PEDF, Hp and Tau levels, using Iterative Marginal Optimization, improved the differential diagnosis of AD, especially in patients with moderate to severe dementia (p<0.002). This pilot study highlights the probable different contribution of oxidative mechanisms in dementia.

Study on Aß34 biology and detection in transgenic mice brains.

The ß-amyloid precursor protein undergoes cleavages by ß- and γ-secretasses yielding amyloid-ß peptides (Aß) that accumulate in Alzheimer's disease. Subsequently, Aß peptides are targets of additional truncations or endoproteolytic cleavages explaining the diversity of Aß-related fragments recovered in cell media or pathologic human fluids. Here, we focused on Aß1-34 (Aß34) that has been detected both in vitro and in vivo and that derives from the hydrolysis of Aß by ß-secretase. We have obtained and fully characterized by immunologic and biochemical approaches, a polyclonal antibody that specifically recognizes the C-terminus of Aßx-34. We present immunohistochemical evidence for the presence of Aßx-34 in the brain of 3xTg mice and Alzheimer's disease-affected human brains. Finally, we demonstrate a neprilysin-mediated degradation process of Aß34 and the ability of synthetic Aß34 to protect HEK cells overexpressing either wild type or Swedish-mutated ß-amyloid precursor protein from apoptosis.

Local carotid atherosclerotic plaque proteins for the identification of circulating biomarkers in coronary patients.

OBJECTIVE: To identify circulating biomarkers that originate from atherosclerotic vulnerable plaques and that could predict future cardiovascular events. METHODS: After a protein enrichment step (combinatorial peptide ligand library approach), we performed a two-dimensional electrophoresis comparative analysis on human carotid plaque protein extracts (fibrotic and hemorrhagic atherosclerotic plaques). In silico analysis of the biological processes was applied on proteomic data. Luminex xMAP assays were used to quantify inflammatory components in carotid plaques. The systemic quantification of proteins originating from vulnerable plaques in blood samples from patients with stable and unstable coronary disease was evaluated. RESULTS: A total of 118 proteins are differentially expressed in fibrotic and hemorrhagic plaques, and allowed the identification of three biological processes related to atherosclerosis (platelet degranulation, vascular autophagy and negative regulation of fibrinolysis). The multiplex assays revealed an increasing expression of VEGF, IL-6, IL-8, IP-10 and RANTES in hemorrhagic as compared to fibrotic plaques (p<0.05). Measurement of protein expressions in plasmas from patients with stable and unstable coronary disease identified a combination of biomarkers, including proteins of the smooth muscle cell integrity (Calponin-1), oxidative stress (DJ-1) and inflammation (IL-8), that allows the accurate classification of patients at risk (p=0.0006). CONCLUSION: Using tissue protein enrichment technology, we validated proteins that are differentially expressed in hemorrhagic plaques as potential circulating biomarkers of coronary patients. Combinations of such circulating biomarkers could be used to stratify coronary patients.

Depletion of proBNP1-108 in patients with heart failure prevents cross-reactivity with natriuretic peptides.

BACKGROUND: After synthesis by cardiomyocytes, precursor proBNP1-108 is cleaved into NT-proBNP and BNP. Recently, cross-reactivity between these assays was discussed. The aim of this study was to characterize the cross-reactivities, through a new biochemical innovative approach consisting in the total depletion of the circulating proBNP1-108 in patients with heart failure (HF). METHODS: This prospective study included 180 patients with chronic HF. BNP and NT-proBNP were dosed with commercial kits. ProBNP1-108 was determined using an ELISA research assay specific to the precursor. ProBNP1-108 depletion was performed by immunocapture with a specific antibody targeting exclusively the ProBNP1-108 hinge region. ProBNP1-108, BNP and NT-proBNP levels were determined before and after depletion using this process in HF patients. RESULTS: Mean age was 74.34 +/-12.5 y, and 69% of patients were males. NYHA classes II and III were the most frequent (32% and 45% respectively). Before depletion, ProBNP1-108, NT-proBNP and BNP levels were 316.8+/-265.9 pg/ml; 6,054.0+/-11,539 pg/ml and 684.3+/-82.1 pg/ml respectively, and were closely correlated with NHYA classes. After immuno-depletion, proBNP1-108 was decreased in mean by 96% (p<0.0001), BNP by 53% (p<0.0001) and NT-proBNP by 5%. The relationship between BNP or NT-proBNP and NHYA classes remained unchanged. CONCLUSION: Current BNP and NT-proBNP assays measured as well proBNP molecule. This cross reactivity percentage has been controversial. Thanks to the removal of circulating proBNP1-108 with our immunodepletion process, we are now able to assess the remaining "true" BNP and NT-proBNP molecules and further evaluate their clinical relevance.

N-truncated Aß peptides in complex fluids unraveled by new specific immunoassays.

Previous studies have highlighted the potential physiopathological and diagnostic role of N- and C-terminally truncated amyloid-ß (Aß) peptides in Alzheimer's disease. However, our knowledge about their production remains incomplete, in part due to the lack of very specific and sensitive tools for their detection. We thus developed specific monoclonal antibodies that target either Aß11-x or Aß17-x species, which result from the combined cleavages by ß/γ- or α/γ-secretases, respectively. The presence of Aß peptides truncated at residue 11 and 17 peptides was qualitatively and quantitatively assessed, using surface enhanced laser desorption ionization-time of flight mass spectrometry and xMAP (Multi-Analyte Profiling) immunoassays, in the supernatant of HEK293 cells that overexpress wild type or mutant Aß protein precursor or in which α- and ß-secretase activities had been modulated. Our results show a differential secretion of Aß11-40 and Aß17-40 species by these HEK293 cell lines. Finally, Aß11-40 concentration in human cerebrospinal fluid (measured with the new xMAP immunoassays) from a first pilot study was higher in cerebrospinal fluid samples from patients with Alzheimer's disease than in samples from patients with other types of dementia.

Solid-phase hexapeptide ligand libraries open up new perspectives in the discovery of biomarkers in human plasma.

BACKGROUND: Pre-treatment of plasma with hexapeptide ligand libraries prior to proteomic analysis is well documented. However, the maintenance of biomarker abundance throughout the different pre-analytical steps is required for a potential application of differential proteomics in clinical studies. METHODS: We combined the use of an amino-terminal hexapeptide ligand library and its carboxyl-terminal version with a sequential elution strategy of the proteins/peptides bound to the beads, followed by either mass spectrometry or 2D electrophoresis analyses. RESULTS: We show the maintenance of C-reactive protein abundance (a marker of inflammation) throughout the process (including hexapeptide bead treatment and proteomic analysis) in patients presenting high and low levels of this protein. In parallel, we assessed the contribution of this workflow to increasing the number of potential biomarkers detected and its suitability for a clinical study on approximately a hundred samples, as well as the reproducibility of the process. CONCLUSIONS: Pre-treatment with hexapeptide ligand libraries opens up new perspectives in the discovery of biomarkers in human plasma by improving the detection of new species while maintaining their original differential abundance. This approach is also suitable for an application in a clinical proteomic study of at least 100 samples.

Pro-B-type natriuretic peptide levels in acute decompensated heart failure.

OBJECTIVES: The present study sought to evaluate the clinical utility of pro-B-type natriuretic peptides (proBNP) in patients admitted with acute decompensated heart failure. BACKGROUND: Plasma natriuretic peptides (BNP(1-)(32), N-terminal [NT]-proBNP(1-76)) have been demonstrated to assist in the diagnosis of patients with heart failure. However, the precursor to these polypeptides (proBNP(1-108)) circulates in plasma and may interfere with the measurement of currently used biomarkers. METHODS: Plasma natriuretic peptides were assessed in 164 individuals (99% men) hospitalized with decompensated heart failure. The B-type natriuretic peptide (BNP), NT-proBNP, and proBNP levels at hospital admission and discharge were compared with the incidence of cardiac death and all-cause mortality within 90 days post-discharge. RESULTS: Pro-B-type natriuretic peptides demonstrated a high degree of correlation with both BNP (R = 0.924, p < 0.001) and NT-proBNP (R = 0.802, p < 0.001) at admission. Further characterization of proBNP demonstrated little variation with changes in age, body mass index, creatinine, or systolic dysfunction. All 3 plasma natriuretic peptides were significantly elevated at admission in patients suffering a cardiac death or all-cause mortality (p < 0.05). Receiver-operating characteristic curves demonstrated that admission and discharge NT-proBNP (area under the curve [AUC] 0.788 and AUC 0.834) had superior prognostic power for all-cause mortality when compared with BNP (AUC 0.644, p < 0.01 and AUC 0.709, p < 0.01) and proBNP (AUC 0.653, p < 0.01 and AUC 0.666, p < 0.01) at the same time points. CONCLUSIONS: Admission values of all natriuretic peptides can be used to predict cardiac death and all-cause mortality. A preliminary comparison suggests that discharge values of NT-proBNP have the greatest diagnostic yield for predicting these end points. Further studies should explore the synergistic prognostic potential of all natriuretic peptides.