Development of a sandwich ELISA for the specific quantitation of hemagglutinin (HA)-tagged proteins during their inducible expression in Escherichia coli

Heavy single-chain antibodies (VHH or nanobodies) are popular in the medical and analytical fields due to its small size, high solubility, stability, and other advantageous features. However, the usage of VHHs is limited by the low yield of its production and purification. In order to determine the optimal purification strategy for VHH to improve the yield, a method to monitor purification at the intermediate steps is needed. In this study, a simple, sensitive, low-cost sandwich enzyme-linked immunosorbent assay (ELISA) was developed to quantitate VHHs throughout the purification steps. Under optimized conditions, the assay has a sensitivity of 0.149 OD·mL/ng and a limit of detection (LOD) of 0.029 ng/mL. The average recoveries of the assay against the spiked samples were 101.9-106.0% and 100.7-108.0%. The method was applied to a variety of real samples for the detection of different VHHs in bacterial cell media. High amount of VHHs (up to 41.3 mg/mL), which are comparable to the average yield of VHH in standard production protocols, were detected in the media. This study raises attention to the problem of protein losses in cell culture supernatants and provides a method for the continuous detection of the protein abundance to optimize the expression and purification protocols especially for nanobodies.

Fast and Reproducible ELISA Laser Platform for Ultrasensitive Protein Quantification

Optofluidic lasers are currently of high interest for sensitive intracavity biochemical analysis. In comparison with conventional methods such as fluorescence and colorimetric detection, optofluidic lasers provide a method for amplifying small concentration differences in the gain medium, thus achieving high sensitivity. Here, we report the development of an on-chip ELISA (enzyme-linked immunosorbent assay) laser platform that is able to complete an assay in a short amount of time with small sample/reagent volumes, large dynamic range, and high sensitivity. The arrayed microscale reaction wells in the ELISA lasers can be microfabricated directly on dielectric mirrors, thus significantly improving the quality of the reaction wells and detection reproducibility. The details of the fabrication and characterization of those reaction wells on the mirror are described and the ELISA laser assay protocols are developed. Finally, we applied the ELISA laser to detecting IL-6, showing that a detection limit of about 0.1 pg/mL can be achieved in 1.5 h with 15 μL of sample/reagents per well. This work pushes the ELISA laser a step closer to solving problems in real-world biochemical analysis.

Markers of Immune Activation and Inflammation, and Non-Hodgkin Lymphoma: A Meta-Analysis of Prospective Studies

Background

Chronic inflammation and immune activation are reported to play a key role in the etiology of non-Hodgkin lymphoma (NHL). We conducted a meta-analysis on the associations between prediagnosis circulating levels of immune stimulatory markers, interleukin 6 (IL-6), IL-10, tumor necrosis factor α (TNF-α), CXCL13, soluble CD23 (sCD23), sCD27, sCD30, and the risk of NHL.

Methods

Relevant studies were identified from PubMed, EMBASE, and Web of Science up to January 1, 2017. We calculated summary odds ratio (OR) estimates for the association between one natural log increase in concentration of each biomarker and NHL using random-effects models for NHL as a composite outcome and for several histological subtypes of NHL.

Results

Seventeen nested case control studies were included. Elevated levels of several biomarkers were more strongly associated with increased odds of NHL: TNF-α, OR = 1.18 (95% confidence interval [CI] = 1.04 to 1.34); CXCL13, OR = 1.47 (95% CI = 1.03 to 2.08); sCD23, OR = 1.57 (95% CI = 1.21 to 2.05); sCD27, OR = 2.18 (95% CI = 1.20 to 3.98); sCD30, OR = 1.65 (95% CI = 1.22 to 2.22). In stratified analyses, IL-6, TNF-α, sCD27, and sCD30 were more strongly associated with NHL in HIV-infected individuals compared to HIV-uninfected individuals. Between-study heterogeneity was observed across multiple biomarkers for overall NHL and by subtypes.

Conclusion

This meta-analysis provides evidence that elevated circulating levels of TNF-α, CXCL13, sCD23, sCD27, and sCD30 are consistently associated with an increased risk of NHL, suggesting the potential utility of these biomarkers in population risk stratification and prediction.

The effect of exercise on resting concentrations of peripheral brain-derived neurotrophic factor (BDNF) in major depressive disorder: A meta-analysis

Exercise interventions have been shown to successfully improve depression in patients with major depressive disorder (MDD), but like other forms of antidepressant treatment, exercise is not effective in all patients and its mechanisms of action have not been fully elucidated. Brain-derived neurotrophic factor (BDNF), a key mediator of neurogenesis and neuronal survival, has been shown to be decreased in individuals with MDD. One potential mechanism by which exercise alleviates depression is through an increase in BDNF. In order to evaluate this hypothesis, we conducted a meta-analysis of studies that assessed the effects of a chronic (multi-week) exercise intervention on BDNF concentrations in MDD patients. MEDLINE, Embase, PsycINFO, SPORTDiscus, Rehabilitation & Sports Medicine Source, and CINAHL databases were searched for original, peer-reviewed reports of peripheral blood BDNF concentrations before and after a chronic exercise intervention in MDD patients. Standardized mean differences (SMDs) were generated from random effects models. Potential sources of heterogeneity were explored in meta-regression analyses. In six studies that met inclusion criteria, resting blood concentrations of BDNF were not significantly higher after a chronic exercise intervention (SMD = 0.43, 95% CI: -0.06-0.92, p = 0.09) in MDD patients. This meta-analysis did not find evidence that a chronic aerobic exercise intervention increases resting concentrations of BDNF in the blood of MDD patients; however, there is a lack of studies in this area making it difficult to reach a definitive conclusion. Future studies on this topic with larger sample sizes and longer durations are needed to draw more robust conclusions.

Metabolic/inflammatory/vascular comorbidity in psychiatric disorders; soluble epoxide hydrolase (sEH) as a possible new target

The common and severe psychiatric disorders, including major depressive disorder (MDD) and bipolar disorder (BD), are associated with inflammation, oxidative stress and changes in peripheral and brain lipid metabolism. Those pathways are implicated in the premature development of vascular and metabolic comorbidities, which account for considerable morbidity and mortality, including increased dementia risk. During endoplasmic reticulum stress, the soluble epoxide hydrolase (sEH) enzyme converts anti-inflammatory fatty acid epoxides generated by cytochrome p450 enzymes into their corresponding and generally less anti-inflammatory, or even pro-inflammatory, diols, slowing the resolution of inflammation. The sEH enzyme and its oxylipin products are elevated post-mortem in MDD, BD and schizophrenia. Preliminary clinical data suggest that oxylipins increase with symptoms in seasonal MDD and anorexia nervosa, requiring confirmation in larger studies and other cohorts. In rats, a soluble sEH inhibitor mitigated the development of depressive-like behaviors. We discuss sEH inhibitors under development for cardiovascular diseases, post-ischemic brain injury, neuropathic pain and diabetes, suggesting new possibilities to address the mood and cognitive symptoms of psychiatric disorders, and their most common comorbidities.

Peripheral inflammatory markers in Alzheimer's disease: a systematic review and meta-analysis of 175 studies

OBJECTIVES

Increasing evidence suggests that inflammation is involved in Alzheimer's disease (AD) pathology. This study quantitatively summarised the data on peripheral inflammatory markers in patients with AD compared with healthy controls (HC).

METHODS

Original reports containing measurements of peripheral inflammatory markers in AD patients and HC were included for meta-analysis. Standardised mean differences were calculated using a random effects model. Meta-regression and exploration of heterogeneity was performed using publication year, age, gender, Mini-Mental State Examination (MMSE) scores, plasma versus serum measurements and immunoassay type.

RESULTS

A total of 175 studies were combined to review 51 analytes in 13 344 AD and 12 912 HC patients. Elevated peripheral interleukin (IL)-1β, IL-2, IL-6, IL-18, interferon-γ, homocysteine, high-sensitivity C reactive protein, C-X-C motif chemokine-10, epidermal growth factor, vascular cell adhesion molecule-1, tumour necrosis factor (TNF)-α converting enzyme, soluble TNF receptors 1 and 2, α1-antichymotrypsin and decreased IL-1 receptor antagonist and leptin were found in patients with AD compared with HC. IL-6 levels were inversely correlated with mean MMSE scores.

CONCLUSIONS

These findings suggest that AD is accompanied by a peripheral inflammatory response and that IL-6 may be a useful biological marker to correlate with the severity of cognitive impairment. Further studies are needed to determine the clinical utility of these markers.

The effect of acute exercise on blood concentrations of brain-derived neurotrophic factor in healthy adults: a meta-analysis

It has been hypothesized that one mechanism through which physical activity provides benefits to cognition and mood is via increasing brain-derived neurotrophic factor (BDNF) concentrations. Some studies have reported immediate benefits to mood and various cognitive domains after a single session of exercise. This meta-analysis sought to determine the effect of a single exercise session on concentrations of BDNF in peripheral blood, in order to evaluate the potential role of BDNF in mediating the beneficial effects of exercise on brain health. MEDLINE, Embase, PsycINFO, SPORTDiscus, Rehabilitation & Sports Medicine Source, and CINAHL databases were searched for original, peer-reviewed reports of peripheral blood BDNF concentrations before and after acute exercise interventions. Risk of bias within studies was assessed using standardized criteria. Standardized mean differences (SMDs) were generated from random effects models. Risk of publication bias was assessed using a funnel plot and Egger's test. Potential sources of heterogeneity were explored in subgroup analyses. In 55 studies that met inclusion criteria, concentrations of peripheral blood BDNF were higher after exercise (SMD = 0.59, 95% CI: 0.46-0.72, P < 0.001). In meta-regression analysis, greater duration of exercise was associated with greater increases in BDNF. Subgroup analyses revealed an effect in males but not in females, and a greater BDNF increase in plasma than serum. Acute exercise increased BDNF concentrations in the peripheral blood of healthy adults. This effect was influenced by exercise duration and may be different across genders.

Altered soluble epoxide hydrolase-derived oxylipins in patients with seasonal major depression: An exploratory study

Many cytochrome p450-derived lipids promote resolution of inflammation, in contrast to their soluble epoxide hydrolase(sEH)-derived oxylipin breakdown products. Here we compare plasma oxylipins and precursor fatty acids between seasons in participants with major depressive disorder with seasonal pattern (MDD-s). Euthymic participants with a history of MDD-s recruited in summer-fall were followed-up in winter. At both visits, a structured clinical interview (DSM-5 criteria) and the Beck Depression Inventory II (BDI-II) were administered. Unesterified and total oxylipin pools were assayed by liquid chromatography tandem mass-spectrometry (LC-MS/MS). Precursor fatty acids were measured by gas chromatography. In nine unmedicated participants euthymic at baseline who met depression criteria in winter, BDI-II scores increased from 4.9±4.4 to 19.9±7.7. Four sEH-derived oxylipins increased in winter compared to summer-fall with moderate to large effect sizes. An auto-oxidation product (unesterified epoxyketooctadecadienoic acid) and lipoxygenase-derived 13-hydroxyoctadecadienoic acid also increased in winter. The cytochrome p450-derived 20-COOH-leukotriene B4 (unesterified) and total 14(15)-epoxyeicosatetraenoic acid, and the sEH-derived 14,15-dihydroxyeicostrienoic acid (unesterified), decreased in winter. We conclude that winter depression was associated with changes in cytochrome p450- and sEH-derived oxylipins, suggesting that seasonal shifts in omega-6 and omega-3 fatty acid metabolism mediated by sEH may underlie inflammatory states in symptomatic MDD-s.

Meta-analysis of Plasma Interleukine-6 Levels in Patients with Depressive Disorder

Growing body of evidence suggests that inflammatory processes play an important role in the pathophysiology and the clinical course of depressive disorder, as well as several others major psychiatric and somatic conditions. Interleukin (IL-6), one of the proinflammatory cytokines, has been extensively examined in a number of studies among depressed patients. To assess quantitatively the relationship between depression and IL-6, a systematic review of relevant literature published to October 2009 was performed and relevant data were meta-analysed using random-effects model. A positive association was found (standardized difference in means=1.055, p>0,001), although a significant heterogeneity among studies (Q(15)=141, p<0,001) points to relevance of further subgroup analyses.

The Effect of Exercise Training on Resting Concentrations of Peripheral Brain-Derived Neurotrophic Factor (BDNF): A Meta-Analysis

Background

The mechanisms through which physical activity supports healthy brain function remain to be elucidated. One hypothesis suggests that increased brain-derived neurotrophic factor (BDNF) mediates some cognitive and mood benefits. This meta-analysis sought to determine the effect of exercise training on resting concentrations of BDNF in peripheral blood.

Methods

MEDLINE, Embase, PsycINFO, SPORTDiscus, Rehabilitation & Sports Medicine Source, and CINAHL databases were searched for original, peer-reviewed reports of peripheral blood BDNF concentrations before and after exercise interventions ≥ 2 weeks. Risk of bias was assessed using standardized criteria. Standardized mean differences (SMDs) were generated from random effects models. Risk of publication bias was assessed using funnel plots and Egger’s test. Potential sources of heterogeneity were explored in subgroup analyses.

Results

In 29 studies that met inclusion criteria, resting concentrations of peripheral blood BDNF were higher after intervention (SMD = 0.39, 95% CI: 0.17–0.60, p < 0.001). Subgroup analyses suggested a significant effect in aerobic (SMD = 0.66, 95% CI: 0.33–0.99, p < 0.001) but not resistance training (SMD = 0.07, 95% CI: -0.15–0.30, p = 0.52) interventions. No significant difference in effect was observed between males and females, nor in serum vs plasma.

Conclusion

Aerobic but not resistance training interventions increased resting BDNF concentrations in peripheral blood.

Reduction of dilution error in ELISAs using an internal standard

Background: Dilution bias is a major cause of immunoassay variability due to the lack of an internal standard to determine the true versus the expected dilution value. Methodology: We used an internal control to measure dilution bias in an ELISA. Acridine-orange was added at the first dilution step and monitored throughout dilutions. Assay results were corrected using the fluorescent signal ratio between samples and reference. Acridine dilution correlated with analyte-specific assay measurements (R2 = 0.987). Correction of assay results with the measured dilution factor improved both accuracy and precision resulting in a reduction of >50% %CV reduction. Conclusion: Dilution correction can significantly improve accuracy and precision of immunoassays. Additional control strategies may further mitigate other sources of variability.

State-of-the art comparability of corrected emission spectra. 1. Spectral correction with physical transfer standards and spectral fluorescence standards by expert laboratories

The development of fluorescence applications in the life and material sciences has proceeded largely without sufficient concern for the measurement uncertainties related to the characterization of fluorescence instruments. In this first part of a two-part series on the state-of-the-art comparability of corrected emission spectra, four National Metrology Institutes active in high-precision steady-state fluorometry performed a first comparison of fluorescence measurement capabilities by evaluating physical transfer standard (PTS)-based and reference material (RM)-based calibration methods. To identify achievable comparability and sources of error in instrument calibration, the emission spectra of three test dyes in the wavelength region from 300 to 770 nm were corrected and compared using both calibration methods. The results, obtained for typical spectrofluorometric (0°/90° transmitting) and colorimetric (45°/0° front-face) measurement geometries, demonstrated a comparability of corrected emission spectra within a relative standard uncertainty of 4.2% for PTS- and 2.4% for RM-based spectral correction when measurements and calibrations were performed under identical conditions. Moreover, the emission spectra of RMs F001 to F005, certified by BAM, Federal Institute for Materials Research and Testing, were confirmed. These RMs were subsequently used for the assessment of the comparability of RM-based corrected emission spectra of field laboratories using common commercial spectrofluorometers and routine measurement conditions in part 2 of this series (subsequent paper in this issue).

Exercise intervention and inflammatory markers in coronary artery disease: a meta-analysis

BACKGROUND

Inflammatory activity plays a role in the development and progression of coronary artery disease (CAD), and exercise confers survival benefit. We performed a meta-analysis of changes in inflammatory biomarkers over the course of exercise interventions in patients with CAD.

METHODS

We searched MEDLINE, Embase, the Cochrane Collaboration, AMED, and CINAHL for studies reporting peripheral inflammatory biomarker concentrations before and after exercise interventions of ≥ 2 weeks in patients with CAD. Data were summarized using standard mean differences (SMD) and 95% CIs.

RESULTS

Twenty-three studies were included. Concentrations of C-reactive protein (CRP; SMD -0.345, 95% CI -0.444 to -0.246, n = 1,466, P < .001), interleukin 6 (SMD -0.546, 95% CI -0.739 to -0.353, n = 280, P < .001), fibrinogen (SMD -0.638, 95% CI -0.953 to -0.323, n = 247, P < .001), and vascular cell adhesion molecule 1 (SMD -0.413, 95% CI -0.778 to -0.048, n = 187, P = .027) were lower postintervention. Higher total cholesterol (B = -0.328, 95% CI -0.612 to -0.043, P = .026) and higher total/high-density lipoprotein cholesterol ratios (B = -0.250, 95% CI -0.425 to -0.076, P = .008) at baseline were associated with greater reductions in CRP. In controlled studies, follow-up concentrations of CRP (SMD -0.500, 95% CI -0.844 to -0.157, n(exercise/control) = 485/284, P = .004), and fibrinogen (SMD -0.544, 95% CI -1.058 to -0.030, n(exercise/control) = 148/100, P = .038) were lower in subjects who exercised compared with controls.

CONCLUSION

Exercise training is associated with reduced inflammatory activity in patients with CAD. C-reactive protein and fibrinogen have provided the strongest evidence. Higher baseline CRP and adverse baseline lipid profiles predicted greater reductions in CRP.

A meta-analysis of cytokines in Alzheimer's disease

BACKGROUND

Studies suggest that inflammation is involved in the neurodegenerative cascade leading to Alzheimer's disease (AD) pathology and symptoms. This study sought to quantitatively summarize the clinical cytokine data.

METHODS

Original English language peer-reviewed studies measuring cytokine concentrations in AD and healthy control subjects were included. Mean (± standard deviation) cytokine concentrations for AD and control subjects were extracted.

RESULTS

Forty studies measuring peripheral blood cytokine concentrations and 14 measuring cerebrospinal fluid (CSF) cytokine concentrations were included. In peripheral blood, there were significantly higher concentrations (weighted mean difference [95% confidence interval]) of interleukin (IL)-6 (2.86 [1.68, 4.04] pg/mL, p < .00001, N[AD/control subjects] = 985/680, 14 studies), tumor necrosis factor (TNF)-α (3.25 [.76, 5.74] pg/mL, p = .01, N = 680/447, 14 studies), IL-1β (.55 [.32, .78] pg/mL, p < .00001, N = 574/370, 10 studies), transforming growth factor (TGF)-β (67.23 [28.62, 105.83] pg/mL, p = .0006, N = 190/158, 5 studies), IL-12 (7.60 [5.58, 9.62] pg/mL, p < .00001, N = 148/106, 5 studies), and IL-18 (15.82 [1.98, 29.66] pg/mL, p = .03, N = 131/94, 4 studies) but not of IL-4, IL-8, IL-10, interferon-γ, or C-reactive protein in AD subjects compared with control subjects. There were significantly higher concentrations of TGF-β (7.81 [2.27, 13.35] pg/mL, p =.006, N = 113/114, 5 studies) but not IL-6, TNF-α, and IL-1β in the CSF of AD subjects compared with control subjects.

CONCLUSIONS

These results strengthen the clinical evidence that AD is accompanied by an inflammatory response, particularly higher peripheral concentrations of IL-6, TNF-α, IL-1β, TGF-β, IL-12 and IL-18 and higher CSF concentrations of TGF-β.

Mapping the placement of oligonucleotide molecules using scanning probe microscopy

The successful development of novel bio-inspired devices requires the ability to place specific biomolecules on a substrate with nanometre precision, in such a way so that their bioactivity is retained. A method is required that can verify this bio-modification. Scanning probe microscopy (SPM) can image and probe a surface in a liquid environment with nanometre resolution. Using short chain complementary oligonucleotides as the bioactive molecules we have modified continuous and patterned gold substrates and SPM probes. We demonstrated that the attached oligonucleotides retained their biological activity after surface attachment with a hybridization interaction force that varies between 50 and 400pN as measured by SPM force measurements. Finally, the position of the attached oligonucleotides was determined with nanometre resolution. Thus we have demonstrated the capabilities of SPM in the application of the development of substrates and templates suitable for forming the basis of novel and innovative devices.

A meta-analysis of cytokines in major depression

BACKGROUND

Major depression occurs in 4.4% to 20% of the general population. Studies suggest that major depression is accompanied by immune dysregulation and activation of the inflammatory response system (IRS). Our objective was to quantitatively summarize the data on concentrations of specific cytokines in patients diagnosed with a major depressive episode and controls.

METHODS

We performed a meta-analysis of studies measuring cytokine concentration in patients with major depression, with a database search of the English literature (to August 2009) and a manual search of references.

RESULTS

Twenty-four studies involving unstimulated measurements of cytokines in patients meeting DSM criteria for major depression were included in the meta-analysis; 13 for tumor necrosis factor (TNF)-alpha, 9 for interleukin (IL)-1beta, 16 for IL-6, 5 for IL-4, 5 for IL-2, 4 for IL-8, 6 for IL-10, and 4 for interferon (IFN)-gamma. There were significantly higher concentrations of TNF-alpha (p < .00001), weighted mean difference (WMD) (95% confidence interval) 3.97 pg/mL (2.24 to 5.71), in depressed subjects compared with control subjects (438 depressed/350 nondepressed). Also, IL-6 concentrations were significantly higher (p < .00001) in depressed subjects compared with control subjects (492 depressed/400 nondepressed) with an overall WMD of 1.78 pg/mL (1.23 to 2.33). There were no significant differences among depressed and nondepressed subjects for the other cytokines studied.

CONCLUSIONS

This meta-analysis reports significantly higher concentrations of the proinflammatory cytokines TNF-alpha and IL-6 in depressed subjects compared with control subjects. While both positive and negative results have been reported in individual studies, this meta-analytic result strengthens evidence that depression is accompanied by activation of the IRS.