Fluorescent nanoparticles as labels for immunometric assay of C-reactive protein using two-photon excitation assay technology

We describe the use of fluorophore-doped nanoparticles as reporters in a recently developed ArcDia TPX bioaffinity assay technique. The ArcDia TPX technique is based on the use of polymer microspheres as solid-phase reaction carrier, fluorescent bioaffinity reagents, and detection of two-photon excited fluorescence. This new assay technique enables multiplexed, separation-free bioaffinity assays from microvolumes with high sensitivity. As a model analyte we chose C-reactive protein (CRP). The assay of CRP was optimized for assessment of CRP baseline levels using a nanoparticulate fluorescent reporter, 75 nm in diameter, and the assay performance was compared to that of CRP assay based on a molecular reporter of the same fluorophore core. The results show that using fluorescent nanoparticles as the reporter provides two orders of magnitude better sensitivity (87 fM) than using the molecular label, while no difference between precision profiles of the different assay types was found. The new assay method was applied for assessment of baseline levels of CRP in sera of apparently healthy individuals.     

一种定量检测人血清高敏C反应蛋白的化学发光免疫方法

旨在建立一种可定量检测人血清高敏CRP的化学发光检测方法 (High-sensitivity C-reactive protein quantifiable chemiluminescent immunoassay,hs-CRP CLIA)。首先利用亲和层析和离子交换层析技术从肝硬化病人腹水中纯化出高纯度的天然CRP作为免疫原制备了22株CRP单克隆抗体 (单抗),其中13株单抗在磷酸胆碱配体捕获ELISA中呈阳性,然后利用方正滴定法筛选出单抗10C5和10C11建立了hs-CRP CLIA。试剂盒评估结果显示：该方法对血清中干扰物质IgG、血红蛋白、甘油三酯等无非特异性反应;该方法检测灵敏度高,在0.04~20.38 mg/L范围内定量检测人血清CRP标准品呈良好线性关系 (R2＞0.993);该方法准确性高、可重复性好,平均回收率为99％,批内差为4.2％~5.8％,批间差为9.0％~11.5％;该方法与进口商品化高敏CRP ELISA试剂盒平行比较检测90份血清标本,结果显示两者有良好的可比性 (r=0.968)。综上,建立的hs-CRP CLIA是一种准确、可靠、可定量的高灵敏C反应蛋白检测方法,该方法的临床应用,有利于改善我国心脏病风险评估及肠炎性疾病预后判断。     

C-反应蛋白对脂肪细胞脂联素表达的影响

通过体外培养脂肪细胞,研究C-反应蛋白（CRP）对大鼠脂肪细胞脂联素蛋白分泌及mRNA基因表达的影响。取大鼠附睾脂肪垫培养脂肪细胞。用0、10、50ug／mL的CRP刺激脂肪细胞6h,提取细胞RNA,用实时荧光定量RT-PCR技术检测脂联素mRNA表达的变化;收集细胞培养液,运用Western blot技术检测脂联素蛋白分泌的变化。结果显示0、10、50ug／mL的CRP对大鼠脂肪细胞脂联素mRNA表达的影响无差异（P〉0．05）。50、10ug／mL的CRP均可减少大鼠脂肪细胞培养液中脂联素蛋白的分泌量（P〈0．05）。CRP可呈剂量依赖性的降低脂肪细胞脂联素蛋白分泌的水平。而各组CRP未能影响脂肪细胞脂联素mRNA的表达。CRP对脂肪细胞脂联素基因表达和蛋白分泌的研究可以揭示转录后的控制决定了CRP对脂联素的影响。     

One-step kinetics-based immunoassay for the highly sensitive detection of C-reactive protein in less than 30 min

This article reveals a rapid sandwich enzyme-linked immunosorbent assay (ELISA) for the highly sensitive detection of human C-reactive protein (CRP) in less than 30 min. It employs a one-step kinetics-based highly simplified and cost-effective sandwich ELISA procedure with minimal process steps. The procedure involves the formation of a sandwich immune complex on capture anti-human CRP antibody-bound Dynabeads in 15 min, followed by two magnet-assisted washings and one enzymatic reaction. The developed sandwich ELISA detects CRP in the dynamic range of 0.3 to 81 ng ml⁻¹ with a limit of detection of 0.4 ng ml⁻¹ and an analytical sensitivity of 0.7 ng ml⁻¹. It detects CRP spiked in diluted human whole blood and serum with high analytical precision, as confirmed by conventional sandwich ELISA. Moreover, the results of the developed ELISA for the determination of CRP in the ethylenediaminetetraacetic acid plasma samples of patients are in good agreement with those obtained by the conventional ELISA. The developed immunoassay has immense potential for the development of rapid and cost-effective in vitro diagnostic kits.     

Study of the spontaneous dissociation of rabbit C-reactive protein

C-Reactive protein (CRP) is composed of five identical noncovalently linked monomers and characterized as an important acute-phase protein. The CRP subunit obtained by denaturing treatments, which is termed modified CRP, has also been widely studied. In the current work, we found that there exists some degree of natural dissociation of CRP in stock solution. This dissociation is critically dependent on the absence of Ca²⁺. Low pH could enhance the dissociation of CRP, while ionic strength has little effect. Anilinonaphthalenesulfonate (ANS) fluorescence detections indicate that the exposure of hydrophobic surface increases during the dissociation. Acidic pH conditions also induce an increase in ANS fluorescence. This suggests that hydrophobic interactions between CRP subunits may contribute to the study of its pentameric structure. Surface plasmon resonance experiments indicate that monomeric CRP does not specifically bind to phosphatidylcholine-containing membrane as native CRP does. Electron microscopy shows that monomeric CRP binds to negatively charged lipid through electrostatic forces, and such lipid may induce the dissociation of CRP due to the acidic pH in the diffuse double layer near the membrane.     

动态监测C-反应蛋白及降钙素原在创伤后脓毒血症中的价值

目的 探讨C-反应蛋白及降钙素原在创伤后脓毒血症中的动态变化及对预后的评估价值。方法 选择诸暨市中心医院创伤后脓毒血症患者78例作为研究对象,比较脓毒血症组与对照组之间血清CRP及PCT水平的差异。根据脓毒血症的不同程度将入选的创伤后脓毒血症病例分为单纯脓毒血症、脓毒血症合并器官功能衰竭及感染性休克组,比较三组患者血清CRP水平、血清PCT水平及APACHE-II评分的差异。根据不同的随访结果将脓毒血症患者分为好转、无效及病死组,比较三组入选当日、入选后第3、5天血清CRP及PCT水平的变化。结果 入选当日,脓毒血症组患者血清CRP及PCT水平均明显高于对照组,差异具有统计学意义（t=68.472、40.243,P0.05）,其余两组间比较差异均有统计学意义（P0.05）;血清PCT水平入选当日、入选后第3天、第5天呈逐渐下降趋势,组间比较差异均有统计学意义（P0.05）,而血清PCT水平呈递增趋势,组间比较差异均有统计学意义（P0.05）。结论 血清CRP及PCT水平均能反应创伤后脓毒血症的感染状态,但在评估病情及预后方面,血清PCT更具有优势。     

Development of a bead-based aptamer/antibody detection system for C-reactive protein

A multiplexing bead-based platform provides an approach for the development of assays targeting specific analytes for biomonitoring and biosensing applications. Multi-Analyte Profiling (xMAP) assays typically employ a sandwich-type format using antibodies for the capture and detection of analytes of interest, and the system permits the simultaneous quantitation of multiple targets. In this study, an aptamer/antibody assay for the detection of C-reactive protein (CRP) was developed. CRP is an acute phase marker of inflammation whose elevated basal levels are correlated with an increased risk for a number of pathologies. For this assay, an RNA aptamer that binds CRP was conjugated to beads to act as the capture agent. Biotinylated anti-CRP antibody coupled to fluorescently labeled streptavidin was used for quantification of CRP. The detection limit of the CRP assay was 0.4 mg/L in diluted serum. The assay was then used to detect spiked CRP samples in the range of 0.4 to 10 mg/L in diluted serum with acceptable recoveries (extrapolated values of 70–130%), including that of a certified reference material (129% recovery). The successful incorporation of the CRP aptamer into this platform demonstrates that the exploration of other aptamer–target systems could increase the number of analytes measurable using xMAP-type assays.     

Quantitative measurements of C-reactive protein using silicon nanowire arrays

A silicon nanowire-based sensor for biological application showed highly desirable electrical responses to either pH changes or receptor-ligand interactions such as protein disease markers, viruses, and DNA hybridization. Furthermore, because the silicon nanowire can display results in real-time, it may possess superior characteristics for biosensing than those demonstrated in previously studied methods. However, despite its promising potential and advantages, certain process-related limitations of the device, due to its size and material characteristics, need to be addressed. In this article, we suggest possible solutions. We fabricated silicon nanowire using a top-down and low cost micromachining method, and evaluate the sensing of molecules after transfer and surface modifications. Our newly designed method can be used to attach highly ordered nanowires to various substrates, to form a nanowire array device, which needs to follow a series of repetitive steps in conventional fabrication technology based on a vapor-liquid-solid (VLS) method. For evaluation, we demonstrated that our newly fabricated silicon nanowire arrays could detect pH changes as well as streptavidin-biotin binding events. As well as the initial proof-of-principle studies, C-reactive protein binding was measured: electrical signals were changed in a linear fashion with the concentration (1 fM to 1 nM) in PBS containing 1.37 mM of salts. Finally, to address the effects of Debye length, silicon nanowires coupled with antigen proteins underwent electrical signal changes as the salt concentration changed.     

阿维菌素中毒患者血清C反应蛋白的浓度变化及意义

目的探讨口服阿维菌素中毒患者血清C反应蛋白浓度变化与病情严重程度及预后的关系。方法将39例口服阿维菌素中毒患者分为轻度中毒组和中重度中毒组,42例健康体检者为对照组。轻、中重度中毒组患者分别于入院时及入院第3、5天检测血清C反应蛋白浓度,并进行组间比较。结果中毒组血清CRP水平明显高于对照组,差异有统计学意义（P〈0.05）;轻度中毒组血清CRP水平在入院时及入院第3、5天变化较小,各时点血清CRP水平比较无显著统计学意义（P〉0.05）;中重度中毒组血清CRP水平在入院时即显著升高,入院第3天达最高值,各时点血清CRP水平比较差异有统计学意义（P〈0.05）。结论血清C反应蛋白浓度可作为判断口服阿维菌素中毒患者病情严重程度及预后的敏感指标。     

Attenuation of photobleaching in two-photon excitation fluorescence from green fluorescent protein with shaped excitation pulses

The two-photon excitation fluorescence (TPEF) process of an enhanced green fluorescent protein (EGFP) for fluorescence signals was adaptively controlled by the phase-modulation of femtosecond pulses. After the iteration of pulse shaping, a twofold increase in the ratio of the fluorescence signal to the laser peak power was achieved. Compared with conventional pulses optimized for peak power, phase-optimized laser pulses reduced the bleaching rate of EGFP by a factor of 4 while maintaining the same intensity of the fluorescence signal. Our method will provide a powerful solution to various problems confronting researchers, such as the photobleaching of dyes in two-photon excitation microscopy.     

Membrane activity of a C-reactive protein

C-reactive protein (CRP) from the American horseshoe crab, Limulus polyphemus, exhibits complex membrane activities. Here, we describe the behavior of protein and lipid as CRP interacts with model liposomes and bacterial membranes. Limulus C-reactive protein (L-CRP) forms extended fibrilar structures that encapsulate liposomes in the presence of Ca²⁺. We have observed structures consistent in size and shape with these fibers bound to the surface of Gram-negative bacteria. The membranes of Limulus CRP-treated bacteria exhibit significantly different mechano-elastic properties than those of untreated bacteria. In vitro, bilayer lipids undergo a rigidification and reorganization of small domains. We suggest that these interactions reflect the protein’s role as a primary defense molecule, functioning in the entrapment and killing of potential pathogens.     

Expression of membrane-associated C-reactive protein by human monocytes: indications for a selectin-like activity participating in adhesion

We have shown previously that rat liver macrophages (Kupffer cells) express a membrane-bound form of C-reactive protein (mCRP) on their surface which is identical to a galactose-specific particle receptor activity. We now establish the presence of mCRP on human monocyte-macrophages using immunocytochemistry with an anti-neoCRP specific monocloncal antibody and RNA-RNAin situ hybridization to demonstrate the presence of CRP-specific mRNA. Concomitant with mCRP expression, cells exhibit galactose-dependent uptake of particles coated with lactosylated bovine serum albumin. Adhesion experiments on fibronectin-coated surfaces that mCRP on human blood monocytes may act as a selectin-like adhesion molecule, mediating initial carbohydrate-specific contacts which are followed by peptide-specific recognition via integrin receptors.     

C-reactive protein as an early predictor of COVID-19 severity

BackgroundData for predicting severity of patients with COVID-19 infection are sparse and still under investigation. We retrospectively studied whether the admission serum C-reactive protein level (CRP) can serve as nearly predictor of disease severity during COVID-19 infection in comparison with other hematologic and inflammatory markers.MethodsWe included all consecutive patients who were admitted in Cheikh Khalifa International University Hospital, Casablanca, Morocco, between February to April 2020, with a confirmed diagnosis of COVID-19 infection using SARS-CoV-2 viral nucleic acid via RT-PCR. The complete blood count and serum CRP level were routinely measured on admission. All clinical and laboratory data of patients were collected and analyzed. The classification of the disease severity was in accordance with the clinical classification of the WHO interim guidance, and the management of patients were adapted to the national management guideline. We estimated receiver operating characteristic (ROC) curves of blood routine parameters as well as their association with COVID-19 disease severity.Results145 COVID-19 patients were included in the study. The median age (range) was 50 (32-63) years, and 75 (51.7%) were men. 101 patients were classified in the non-severe group and 44 patients in the severe group. Based on disease severity, significant differences were observed in the age, gender, comorbidities, and respiratory symptom. Similarly, the biological analysis found significant differences for the neutrophil count, lymphocyte count, eosinophil count, and CRP level. However, according to ROC curves of these laboratory biomarkers, the AUC of CRP at 0.872 was significantly higher than all other parameters. Further, CRP was independently associated with severity of COVID-19 disease (OR = 1.11, 95% IC (1.01-1.22) and or = 1.13, 95% IC (1.04-1.23)).ConclusionsThis study found that the CRP level at admission represent a simple and independent factor that can be useful for early detection of severity during COVID-19 and the easy guidance of primary care.     

Role of C-reactive protein in complement-mediated hemolysis in Malaria

Human C-reactive protein (CRP) is a clinically important classical acute phase protein. Although CRP has been reported to bind with many nucleated cells, the direct binding of CRP to erythrocytes in diseases remains largely unexplored. The main focus of the present study was to investigate the binding of disease-specific CRP to erythrocytes of same patients. Distinct molecular variant of disease-specific CRP was affinity purified from sera of malaria patients (CRP_Mal). This CRP showed strong binding with malaria erythrocytes (RBC_Mal) as confirmed by flow cytometric analysis (FACS), enzyme-linked immunosorbent assays (ELISA), and radio binding assays. Calcium and phosphoryl choline (PC) were found to be essential for this interaction. A 2.3-fold increased binding of induced CRP to RBC_Mal as compared to normal erythrocytes (RBC_N) confirmed disease-specificity. Preincubation of RBC_Mal with unconjugated CRP showed 3–5 fold inhibition. The association constant of CRP and RBC_Mal was 4.7 × 10⁶ cpm/μg with the corresponding number of receptors/cell being 4.3 × 10⁵. The effector function of CRP_Mal has been demonstrated by its potency to activate the complement pathway. An optimal dose of 10 μg/ml of CRP induced three-fold higher hemolysis of patient erythrocytes as compared to RBC_N. These studies provide direct evidence for an important phagocytic functional interaction of this acute-phase protein by triggering the CRP-complement pathway after the binding of CRP_Mal with RBC_Mal. Hemolysis as triggered by this pathway may be one of the causative factors of anemia, a common clinical manifestation of this disease.     

Obesity is an independent determinant of elevated C-reactive protein in healthy women but not men

Background and aims: High-sensitivity C-reactive protein (hs CRP) has emerged as an inflammatory biomarker to predict metabolic syndrome. Here, we investigate the association of hs CRP with metabolic variables and determine the risks for elevated hs CRP levels in healthy Singaporean adults.

Methods: We conducted a cross-sectional study of 225 participants (104 men). The levels of hs CRP and fasting lipid parameters were analyzed by COBAS. Body composition was determined with dual-energy X-ray absorptiometry.

Results: Twenty-one (9?%) participants had elevated hs CRP levels (>3?mg/mL). The levels of hs CRP had significant correlations (p?<0.05) with obesity and metabolic variables among women. Stepwise multivariate regression analysis identified FM (%) (accounted for 22.5% of the variability in hs CRP levels) as a major determinant of hs CRP levels. On multivariate regression, FM (%) was the independent determinant of intermediate and elevated hs CRP in women after adjustment for the potential confounders.

Conclusions: Obesity may play a direct role in the elevated hs CRP levels in women, but not men living in Singapore. This is probably due to different body composition or different effects of sex hormones on adipose tissue between men and women.     

Therapeutic effects of a synthetic peptide of C-reactive protein in pre-clinical tumor models

Previous studies have shown that multilamellar vesicles (MLV) or other carriers containing purified human C-reactive protein (CRP) have therapeutic activity in preclinical tumor models. Here we evaluated the therapeutic effects of MLV containing novel synthetic peptides, derived from the structure of CRP, on the extent of (a) established lung metastases of fibrosarcoma T241 in C57B1/6 mice, (b) survival of C57B1/6 mice bearing established liver metastases of colon carcinoma MCA-38, and (c) primary tumor growth of Renca renal carcinoma in Balb/c mice. In all cases, a single synthetic CRP peptide, RS-83277, demonstrated significant antitumor effects comparable to that seen with intact CRP. Two other synthetic CRP peptides, RS-83287 and RS-83147, showed no therapeutic activity and were comparable to control MLV containing only buffer. None of the peptides contained sequences homologous with that of the phagocyte stimulant, tuftsin. Activity of MLV-encapsulated RS-83277 was dose-dependent, and a comparable dose of the soluble peptide, given either alone or following injection of buffer-MLV, was ineffective. These results demonstrate immunotherapeutic potential for a novel synthetic peptide derived from CRP, and endogenous acute-phase protein.This work was supported in part by grant CA 49950 from the National Cancer Institute, and grant 43618 from the National American Cancer Society     

Nicotine induces the expression of C-reactive protein via MAPK-dependent signal pathway in U937 macrophages

Atherosclerosis is an inflammatory disease in the vessel wall. Nicotine, a major component of cigarette smoke, is an independent risk factor for cardiovascular diseases including atherosclerosis. As an inflammatory molecule, C- reactive protein (CRP) participates in atherogenesis. Although it has been confirmed that CRP level in smoking patient is significantly higher than non-smokers and cigarette withdrawal, it is unknown whether nicotine induces CRP expression in macrophages. The present study was to observe effect of nicotine on CRP production and the related signal pathway in U937 macrophages. The results showed that nicotine significantly increased mRNA and protein expression of CRP in U937 macrophages in time- and concentration-dependent ways. Nicotinic acetylcholine receptor (nAChR) blocker hexamethonium, MEK1/2 inhibitor PD98059, p38 MAPK inhibitor SB203580 and NF-κB inhibitor PDTC almost completely abolished nicotineinduced CRP expression in mRNA and protein levels in U937 macrophages. The further study indicated that hexamethonium, PD98059, and SB203580 significantly inhibited ERK1/2 and p38 MAPK phosphorylation. These demonstrate that nicotine has ability to induce CRP expression in macrophages through nAChR-ERK1/2/p38 MAPK-NF-κB signal pathway, which contributes to better understanding of the pro-inflammatory and pro-atherosclerotic effects of nicotine in cigarette smokers.     

Crystallization and preliminary X-ray diffraction studies of dogfish C-reactive protein

Crystals of dogfish (Mustelus canis) C-reactive protein were obtained through vapor phase equilibration using the sitting drop rod technique with ammonium sulfate as the precipitating agent. The space group was determined to be P1 (triclinic lattice) with unit cell dimensions of a = 82.91, b = 92.25 and c = 103.40 Å; α = 83.36°, β = 89.76°, and γ = 81.30°. These crystals diffract to about 2.6 Å resolution and contain two hexamers in the asymmetric unit. © 1993 Wiley-Liss, Inc.