Development of an indirect sandwich ELISA for detection of urinary antigen,using Legionella pneumophila PAL protein

Legionella pneumophila peptidoglycan-associated lipoprotein (PAL) protein is an extremely conserved antigen among Legionella species. In this study, rabbit and rat anti-PAL immunoglobulin G antibodies were produced by immunization with purified, recombinant PAL (r-PAL) protein of L. pneumophila serogroup 1 and used as capture and detection antibodies in the PAL antigen-based enzyme-linked immunosorbent assay (ELISA) to detect urinary PAL antigen. Urine samples were obtained from rats experimentally infected with L. pneumophila serogroup 1. The PAL antigen was measured in urine samples of 40 infected and 40 uninfected rats. After choosing the cut-off value of 0.192, the sensitivity and specificity of the PAL antigen-based ELISA were 87.5 and 97.5 %, respectively. The results obtained by PAL antigen base ELISA were compared with those obtained by Biotest. The PAL antigen was detected efficiently by both of the assays and all of the control human urine samples were negative by the ELISA test. The PAL antigen-based ELISA assay was relatively simple to perform, precise, highly sensitive and specific, and reproducible. Based on our data the PAL antigen-based ELISA described here is the first indirect sandwich ELISA for urinary antigen detection which could easily be applied for diagnosis of Legionnaires disease.     

Comparison of several ELISA tests for detecting the presence of IgG and IgM against herpes simplex viruses

Four enzyme-linked immunosorbent assays designated test 1 (ETI-HSVK-G 1/2); test 2 (ETI-HSVK-M 1/2); test 3 (ETI-HSVK-G 2), and test 4 (BioElisa HSV2 IgG) were studied to evaluate different stages of herpes simplex virus (HSV) infection. Samples (50 sera and 14 cerebrospinal fluid) were included in four groups. Group 1 consisted of samples from patients with primary HSV infections; group 2 comprised samples from patients with recurrent HSV infections; group 3 were samples nonreactive to HSV; and group 4 were samples from patients with infections by other herpes viruses (4a, chickenpox; 4b, herpes zoster; and 4c, infectious mononucleosis by Epstein-Barr virus). The percentages of agreement between tests 1 and 2 were 100 and 72.1%, respectively. The total diagnostic values of tests 1 and 2 were: 100 and 50% sensitivity, respectively; and 100 and 89% specificity, respectively. Few positive results for HSV-2 infection were found, and so, tests 3 and 4 were not evaluated. The results of tests 3 and 4 for a chickenpox patient, and a herpes zoster patient were not in agreement.     

破伤风类毒素抗体酶联双抗原夹心法定量检测试剂的研制及评价

研制破伤风类毒素抗体酶联双抗原夹心法定量检测试剂,用于破伤风免疫血浆抗体效价检测。以精制破伤风类毒素经Sephacryl S-300柱层析纯化后作为包被抗原,用辣根过氧化物酶以改良过碘酸钠法标记精制破伤风类毒素作为酶标记抗原,以破伤风人免疫球蛋白国家标准品采用小鼠中和试验法标定试剂盒定量标准品,制备双抗原夹心法定量检测试剂;进行试剂盒检测范围、特异性、重复性、精密度及稳定性考核,并与小鼠中和试验法、琼脂双扩散法及国外破伤风类毒素抗体酶联试剂盒进行比较。结果显示,试剂盒的检测范围为10~150mIU/ml,灵敏度为10mIU/ml,线性好(r>0.996),板内孔间变异度小(CV<8%),特异性强(100%),重复性好(CV<13%),于37℃放置6天测定结果无明显差异,与小鼠中和试验法、英国Biding Site酶联试剂有良好的一致性。试验证明所研制的试剂盒适用于破伤风免疫血浆中的破伤风抗体效价定量检测。     

间接ELISA法在注射用矛头蝮蛇血凝酶蛇毒种属鉴别中的应用

目的建立间接ELISA法定性检测矛头蝮蛇血凝酶,用于巴曲亭蛇毒种属来源检测。方法将矛头蝮蛇血凝酶为抗原免疫小鼠,与尖吻蝮蛇血凝酶、白眉蝮蛇血凝酶交叉筛选获得特异性单克隆抗体。优化矛头蝮蛇血凝酶单抗(一抗)、HRP标记的羊抗鼠(二抗)IgG、矛头蝮蛇血凝酶(抗原)工作浓度,建立间接ELISA检测方法。考察方法的重复性、中间精密度,确定方法的适用性。采用膜超滤法将巴曲亭中辅料去除,按照建立的ELISA法检测,判定种属来源。结果矛头蝮蛇血凝酶单抗具有强特异性,一抗的最佳工作浓度1∶4000(250ng),二抗的最佳工作浓度1∶4000(250ng),抗原浓度2μg/孔,该法重复性和中间精密度较好。巴曲亭与矛头蝮蛇血凝酶单抗有特异性反应,与其它蛇毒来源血凝酶单抗无交叉反应,确定巴曲亭来源于矛头蝮蛇蛇毒。结论本研究建立的ELISA法具有较好的特异性,可作为巴曲亭蛇毒种属来源判断的方法。     

Development of a sandwich ELISA for the quantification of enterovirus 71

Since 2008, enterovirus 71 (EV71) has been responsible for high-mortality seasonal epidemics of hand, foot and mouth disease in China. Currently many groups in the world are in the process of developing EV71 vaccines to combat this deadly disease. We have developed three EV71-specific monoclonal antibodies, and in this study we report the establishment of a fast and cost-effective sandwich ELISA kit for measurement of virus concentration in EV71 vaccines using a pair of mouse anti-EV71 monoclonal antibodies. The system is specific for EV71 virus, with no cross-reactivity to coxsackievirus A16, H1N1, rabies, and hepatitis A. Using a reference EV71 vaccine standard, the sensitivity of the assay kit was determined to be 0.82 U/ml, with a linear range between 3.75 and 120 U/ml.     

Comparison of an indirect format ELISA on modified graphite and polystyrene surfaces against triazines

An indirect format enzyme-linked immuno-sorbent assay (ELISA) on graphite rods ( 0.8 mm x 20 mm) and, for comparison, on microtiter plates has been developed against terbuthylazine. For this purpose, a series of 2-aminoalkyl-4-chloro-6-terbuthyl-s-triazine-2,6-diamine ELISA haptens with alkyl spacer lengths of 2, 4, 6, and 8 CH2 groups has been synthesized. The graphite rods or the microtiter plates were covered by a polymerized glutaraldehyde network, and the ELISA haptens have been coupled by imino coupling to the free aldehyde groups of that network. epsilon-Aminocaproic acid has been used as an agent to block unspecific binding sites. The ELISA was run in a competitive mode, where the immobilized ELISA hapten and the solute terbuthylazine as a target analyte compete for the solute antibody.     

A sandwich ELISA for bovine serum in viral vaccines

A double antibody sandwich ELISA for the detection of bovine serum in viral vaccines was developed and standardized with commercially available reagents. The detection limit by ELISA was 0.5 ng ml-1. ELISA was found to be 50-400 times more sensitive than the currently used assays. It was concluded that ELISA is a specific, sensitive and reproducible method for the determination of residual amounts of bovine serum in viral vaccines.     

Comparison of the indirect immunofluorescent (IFAT), ELISA test and the comercial Chagatek test for anti-Trypanosoma cruzi antibodies detection

Chagas disease is a public health problem in Colombia, particularly in the eastern region. Because of human migration from rural areas to urban centers, the possibility of transfusional transmission becomes increasingly important. However the risk can be minimized by a careful screening of blood donors by means of serological tests. Colombian blood banks use comercial, foreign serological tests for screening for T. cruzi infection. The purpose of the current study was to compare the IFAT and ELISA tests (both use antigen obtained from Colombian strains) with the comercially available Chagatek tests. Sera of blood donors were classified in two groups on the basis of the IFAT: group I, 15 positive patients and group II, 14 negative patients. Sera from each group were tested by the ELISA and Chagatek tests. The ELISA test detected 100% of the patients as positive in group I and 7% (1/14) of patients as positive in group II. The Chagatek test detected 93% (14/15) of the patients as positive in group I and 50% (7/14) in group II. The kappa index for concordance between the ELISA and IFAT tests was 0.93 (95% C.I.: 0.80-1.00); between IFAT and Chagatek 0.43 (95% C.I.: 0.26-0.62), and between ELISA and Chagatek 0.49 (95% C.I.: 0.31-0.67). These results highlighted the importance of using autochtonous Colombian strains as antigens in screening tests for blood donors.     

用ELISA一步法检测白色念珠菌

用白色念珠菌临床分离株免疫家兔并经纯化获得特异性抗体,建立了检测临床标本中白色念珠菌抗原的ＥＬＩＳＡ一步法,此法的敏感性为９９％,特异性为９８３％,与其它念珠菌和临床常见细菌均无交叉反应,整个反应只需１小时即可完成,可望成为一种取代培养法的快速诊断方法     

The standardization of a 'spot-test' ELISA for the rapid screening of sera and hybridoma cell products II. The determination of binding capacity, binding ratio and coefficient of variation of different ELISA plates in sandwich and indirect ELISA

The different commercially available enzyme-linked immunosorbent assay (ELISA) plates were compared for their binding capacity for purified foot-and-mouth disease virus antigen or IgG, their binding ratio (a measure of the efficiency with which positive and negative serum samples may be distinguished), and their coefficients of variation within a plate, between plates and between batches of plates. No one plate could be described as having ideal characteristics, and the choice of ELISA plate depends on the use to which the ELISA is being put. For our purposes, viz. a 'spot-test' which rapidly and efficiently detects specific antibody when the levels of that antibody are low (hybridoma culture supernatants) or when the antibody is contaminated with other 'interfering' proteins (high concentrations of serum), we found that most of the PVC plates and, of the polystyrene plates, the Nunc Immunoplate I and Dynatech M129B plates performed well. The lowest coefficients of variation were obtained using Nunc Immunoplate I, Dynatech M129B and Falcon 3912 plates.     

双抗体夹心法检测3-硝基酪氨酸方法的建立及应用

目的：建立一种准确、快速的双抗体夹心酶免疫吸附的方法,以定量检测组织中过氧亚硝基阴离子的水平。方法：分别以小鼠源性抗3-硝基酪氨酸单克隆IgG抗体和兔源性抗3-硝基酪氨酸IgG抗体为包被抗体和检测抗体,采用正交设计方法摸索以上各抗体的浓度,建立定量检测3-硝基酪氨酸（3-NT）的双抗体夹心ELISA法。同时,测定心肌缺血再灌注大鼠心肌组织3-NT的含量。结果：本研究建立的双抗体夹心ELISA法检测3-NT的最低检测下限为0．10ng·ml^-1,具有良好线性关系的检测范围是（0．15-7．50）ng·ml^-1（r^2=0．995）;心肌缺血再灌注组大鼠的心肌组织中的3-NT水平为（1022．42±97．35）ng·mg pro^-1,明显高于假手术组（246．58±56．52ng·mg pro^-1,P〈0．01）。结论：本研究建立的定量检测3-NT的双抗体夹心ELISA法能够方便、准确、快速地检测组织中3-NT的含量,为定量检测组织中ONOO-的水平提供了新的方法。     

Development of a double antibody sandwich ELISA assay for the diagnosis of angiostrongyliasis

With the use of 2 monoclonal antibodies (MAbs) against excretory/secretory (ES) antigens of adult Angiostrongylus cantonensis, a new method was developed for double antibody sandwich ELISA for the detection of circulating antigens (CAg). To evaluate the sensitivity of the new procedure, the CAg in sera of rats (80) and mice (15) infected with A. cantonensis, as well as CAg in sera of clinically confirmed angiostrongyliasis patients (70), were evaluated. Cross-reaction testing was used to determine the specificity of serum from patients infected with Ascaris lumbricoides, Trichinella spiralis , Toxoplasma gondii , Schistosoma japonicum, Paragonimus westermani, Clonorchis sinensis, Echinococcus granulosus, Spirometra, and Taenia solium, as well as normal healthy people. The results proved that the sensitivity and the specificity of the new method were totally effective for the detection of A. cantonensis CAg. The assay is highly sensitive, specific, and reproducible, with easy handling and excellent cost effectiveness, and thereby provides a new method for the accurate diagnosis of angiostrongyliasis.     

A sandwich ELISA for the conformation-specific quantification of the activated form of human Bax

Bcl-2 family proteins are critical regulators of mitochondrial outer membrane permeabilization (MOMP), which represents the point of no return of apoptotic cell death. The exposure of the Bax N-terminus at the mitochondria reflects Bax activation; and this activated configuration of the Bax protein is associated with MOMP. N-terminal exposure can be detected using specific monoclonal and/or polyclonal antibodies, and the onset of activated Bax has extensively been used as an early marker of apoptosis. The protocols of immunoprecipitation and/or immunocytochemistry commonly used to detect activated Bax are long and tedious, and allow semiquantification of the antigen at best. The sandwich ELISA protocol we developed has a 5 ng/mL detection limit and is highly specific for the activated conformation of Bax. This ELISA allows a rapid quantification of activated human Bax in whole cells and isolated mitochondria protein extracts. These properties grant this assay the potential to further clarify the prognostic and diagnostic value of activated Bax in disorders associated with deregulated apoptotic pathways such as degenerative diseases or cancer.     

检测牛冠状病毒抗体间接ELISA方法的建立与应用

[背景]牛冠状病毒(Bovine coronavirus,BCoV)是引起新生犊牛死亡的主要病原之一,有效的检测手段是防治该病的前提。目前BCoV ELISA检测方法存在敏感性低、不稳定等缺陷。[目的]对原有BCoV ELISA方法进行改进,建立间接ELISA检测方法。[方法]应用我国BCoV流行毒株CD株n基因为模板,预测N蛋白抗原表位,通过原核表达制备可溶性的重组N蛋白作为抗原,建立间接ELISA方法,应用该方法对黑龙江省2010-2017年的BCoV感染进行血清流行病学调查。[结果]该ELISA方法最佳工作条件为:用50 mmol/LpH 9.6碳酸盐作为包被液,抗原包被浓度2.5μg/mL;用PBST作为样本稀释液,稀释浓度1:50,37℃孵育1.5 h;HRP-羊抗牛IgG稀释浓度1:7 500,37℃孵育1.0 h;用1%明胶37℃封闭30 min。阴阳性临界值为0.225。该方法与BRV、BRSV、BVDV、IBRV、BPIV3和E.coli阳性血清均无交叉反应。批内和批间变异系数均小于10%,与病毒中和试验的符合率高达93.5%。对黑龙江省部分地区共603份奶牛血清样品检测结果显示,BCoV抗体阳性率为98.84%。[结论]建立的ELISA方法特异性强、敏感性高、稳定性好,为进一步研发ELISA试剂盒提供了技术基础。     

Development of a double-antibody sandwich ELISA for sensitive detection of Yersinia pestis

We developed a biotin–streptavidin-based sandwich ELISA for the sensitive and specific detection of Yersinia pestis. In this assay, the F1 capsular protein and Y. pestis were captured by anti-F1 mouse monoclonal antibody followed by detection with biotinylated-anti-F1 rabbit polyclonal antibody and HRP-conjugated streptavidin. The developed F1 ELISA could detect not only the F1 protein up to 29 and 17 pg/ml but also Y. pestis up to 177.8 and 129.2 CFU/ml in PBS buffer and human serum, respectively. In addition, the F1 ELISA did not show any cross-reactivity with various proteins and bacterial strains.     

Application of sandwich ELISA for detecting tag fusion proteins in high throughput

Based on a series of mAbs against four frequently used tags—the human Ig Fc fragment, GST, maltose-binding protein, and thioredoxin—we developed corresponding sandwich enzyme-linked immunosorbent assay (ELISA) to detect these tag fusion proteins. As a supplement for Western blot, the successfully established ELISA was specific, sensitive, quantitative, easy to perform, time-saving, and last but not least, suitable for high-throughput screening of tag fusion proteins. Determination of soluble tag fusion proteins expressed by various systems with the sandwich ELISA developed in the present study could be a valuable and promising tool for the wide application of tag-protein fusion systems in the rapidly growing field of proteomics research. Zhu-wei Xu, Tao Zhang, and Chao-jun Song Contributed equally to this work.